{"id":751,"date":"2025-07-31T14:15:59","date_gmt":"2025-07-31T14:15:59","guid":{"rendered":"https:\/\/cardiocases.com\/?page_id=751"},"modified":"2026-07-08T14:19:29","modified_gmt":"2026-07-08T14:19:29","slug":"av-delays-refractory-periods-and-management-of-tachycardia-medtronic","status":"publish","type":"page","link":"https:\/\/cardiocases.com\/fr\/pacing-defibrillation\/devices-per-company\/medtronic\/av-delays-refractory-periods-and-management-of-tachycardia-medtronic\/","title":{"rendered":"AV delays, refractory periods and management of tachycardia Medtronic"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-page\" data-elementor-id=\"751\" class=\"elementor elementor-751\" data-elementor-post-type=\"page\">\n\t\t\t\t<div class=\"elementor-element elementor-element-622038e e-con-full e-flex e-con e-parent\" data-id=\"622038e\" data-element_type=\"container\" data-e-type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t<div class=\"elementor-element elementor-element-5396007 e-con-full e-flex e-con e-child\" data-id=\"5396007\" data-element_type=\"container\" data-e-type=\"container\" data-settings=\"{&quot;background_background&quot;:&quot;classic&quot;}\">\n\t\t\t\t<div class=\"elementor-element elementor-element-af0d613 elementor-widget elementor-widget-heading\" data-id=\"af0d613\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h2 class=\"elementor-heading-title elementor-size-default\">Medtronic - AV delays, refractory periods, and management of tachycardia<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-74e3911 elementor-toc--minimized-on-tablet elementor-widget elementor-widget-table-of-contents\" data-id=\"74e3911\" data-element_type=\"widget\" data-e-type=\"widget\" data-settings=\"{&quot;headings_by_tags&quot;:[&quot;h3&quot;,&quot;h4&quot;],&quot;exclude_headings_by_selector&quot;:[],&quot;no_headings_message&quot;:&quot;No headings were found on this page.&quot;,&quot;marker_view&quot;:&quot;bullets&quot;,&quot;icon&quot;:{&quot;value&quot;:&quot;fas fa-circle&quot;,&quot;library&quot;:&quot;fa-solid&quot;,&quot;rendered_tag&quot;:&quot;&lt;svg class=\\&quot;e-font-icon-svg e-fas-circle\\&quot; viewBox=\\&quot;0 0 512 512\\&quot; xmlns=\\&quot;http:\\\/\\\/www.w3.org\\\/2000\\\/svg\\&quot;&gt;&lt;path d=\\&quot;M256 8C119 8 8 119 8 256s111 248 248 248 248-111 248-248S393 8 256 8z\\&quot;&gt;&lt;\\\/path&gt;&lt;\\\/svg&gt;&quot;},&quot;minimize_box&quot;:&quot;yes&quot;,&quot;minimized_on&quot;:&quot;tablet&quot;,&quot;hierarchical_view&quot;:&quot;yes&quot;,&quot;min_height&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_tablet&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]},&quot;min_height_mobile&quot;:{&quot;unit&quot;:&quot;px&quot;,&quot;size&quot;:&quot;&quot;,&quot;sizes&quot;:[]}}\" data-widget_type=\"table-of-contents.default\">\n\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__header\">\n\t\t\t\t\t\t<h4 class=\"elementor-toc__header-title\">\n\t\t\t\tContent\t\t\t<\/h4>\n\t\t\t\t\t\t\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--expand\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__74e3911\" aria-expanded=\"true\" aria-label=\"Ouvrir la table des mati\u00e8res\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-down\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M207.029 381.476L12.686 187.132c-9.373-9.373-9.373-24.569 0-33.941l22.667-22.667c9.357-9.357 24.522-9.375 33.901-.04L224 284.505l154.745-154.021c9.379-9.335 24.544-9.317 33.901.04l22.667 22.667c9.373 9.373 9.373 24.569 0 33.941L240.971 381.476c-9.373 9.372-24.569 9.372-33.942 0z\"><\/path><\/svg><\/div>\n\t\t\t\t<div class=\"elementor-toc__toggle-button elementor-toc__toggle-button--collapse\" role=\"button\" tabindex=\"0\" aria-controls=\"elementor-toc__74e3911\" aria-expanded=\"true\" aria-label=\"Fermer la table des mati\u00e8res\"><svg aria-hidden=\"true\" class=\"e-font-icon-svg e-fas-chevron-up\" viewBox=\"0 0 448 512\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M240.971 130.524l194.343 194.343c9.373 9.373 9.373 24.569 0 33.941l-22.667 22.667c-9.357 9.357-24.522 9.375-33.901.04L224 227.495 69.255 381.516c-9.379 9.335-24.544 9.317-33.901-.04l-22.667-22.667c-9.373-9.373-9.373-24.569 0-33.941L207.03 130.525c9.372-9.373 24.568-9.373 33.941-.001z\"><\/path><\/svg><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<div id=\"elementor-toc__74e3911\" class=\"elementor-toc__body\">\n\t\t\t<div class=\"elementor-toc__spinner-container\">\n\t\t\t\t<svg class=\"elementor-toc__spinner eicon-animation-spin e-font-icon-svg e-eicon-loading\" aria-hidden=\"true\" viewBox=\"0 0 1000 1000\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\"><path d=\"M500 975V858C696 858 858 696 858 500S696 142 500 142 142 304 142 500H25C25 237 238 25 500 25S975 237 975 500 763 975 500 975Z\"><\/path><\/svg>\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-7ef9114 elementor-widget elementor-widget-heading\" data-id=\"7ef9114\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">The atrioventricular delay<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-e4e6b7d elementor-widget elementor-widget-text-editor\" data-id=\"e4e6b7d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>The AV delay determines the longest time interval between an atrial event and the programmed\u00a0delivery of a ventricular pacing pulse. This interval\u00a0is the electronic equivalent of the PR interval.<\/p><p>The programming of the AV delay intends to ensure optimal mechanical coordination between atrial\u00a0and ventricular contractions, whether the atrium is sensed or paced. The length of these intervals can\u00a0be programmed within a wide, fixed or adaptable range and influenced\u00a0by a large\u00a0number of\u00a0algorithms.<\/p><p><strong>Paced AV delay<\/strong><\/p><p>A paced AV delay is implemented after atrial pacing when the pacemaker operates in DDD, DDI, DVI\u00a0and DOO modes.<br \/>The observed duration of the paced AV delay might differ from the programmed value because of interactions with the following algorithms:<\/p><ul><li>Adaptable AV delay<\/li><li>AV delay+ hysteresis<\/li><li>Ventricular safety pacing<\/li><li>Non-competitive atrial pacing<\/li><\/ul><p><strong>AV delay<\/strong><\/p><p>The sensed AV delay is implemented after a sensed atrial event when the pacemaker functions in\u00a0atrial synchronized pacing mode (DDD and VDD).<br \/>The observed length of the sensed AV delay might differ from the programed value because of\u00a0interactions with the following algorithms:<\/p><ul><li>Adaptable AV delay<\/li><li>Automatic PVARP<\/li><li>AV delay+ hysteresis<\/li><li>Wenckebach function of the pacemaker during exercise<\/li><\/ul><p><strong>Setting of the AV delay<\/strong><\/p><p>The optimal AV delay varies considerably among patients.<\/p><p>The precise programming of the AV delay must allow the maintenance\u00a0of a constant temporal\u00a0relationship between left atrium and ventricle and\u00a0ensure that the left atrial systole has just ended at\u00a0the onset\u00a0of left ventricular systole.<\/p><p>The permanent programming of long AV delays to promote spontaneous conduction in patients who\u00a0are pacemaker non-dependent can now be avoided by implementing the MVP mode. Indeed, a\u00a0programmed AV delay that is excessively long can be associated with: 1) an enhanced risk of\u00a0pacemaker-mediated tachycardia (PMT), 2) an enhanced risk of pacing during the vulnerable period\u00a0of an ventricular extrasystole that was not sensed because it fell during the post-atrial ventricular\u00a0blanking after atrial pacing, and 3) an adverse hemodynamic effect with fusion of the E and A waves,\u00a0premature closure of the mitral valve, and valvular regurgitation due to the reopening of the valves at\u00a0the end of the ventricular diastole.<\/p><p>An inappropriately short programmed AV delay can be associated with 1) a borderline\u00a0atrial ejection volume with a loss of the active component, and 2) valvular regurgitation in early systole.<\/p><p>If the patient is pacemaker-dependent (complete AV block), the mean value of the optimal, sensed AV delay at rest approaches 110 ms.<\/p><p><strong>Paced versus sensed AV delay<\/strong><\/p><p>The optimal sensed AV delay is shorter than the optimal paced AV delay for several reasons:\u00a0<\/p><ul><li>instead of being sensed at the very onset of the surface P wave, the P wave is sensed at the\u00a0passage of the atrial depolarization signal under the electrode, which is often delayed with\u00a0respect of the onset of the P wave on the surface ECG.<\/li><li>when the P wave is paced, the electro-mechanical delay is longer than when the P wave is of\u00a0sinus origin; the conduction time between right and left atria is prolonged.<\/li><li>the difference between sensed and paced AV delays depends on the position of the lead in\u00a0the right atrium: on average this difference is 30 ms if the lead is in the inter-atrial septum, 50\u00a0ms if it is in the appendage, 70 ms if in the high lateral wall, and \u226590 ms if in a low lateral\u00a0position. These average differences, which must be evaluated and adapted to each individual,\u00a0are often longer in presence of intra- or interatrial conduction disorders.<\/li><li>this difference changes minimally with exercise, though tends to shorten under the influence\u00a0of catecholamines, which shorten interatrial conduction. In presence of major interatrial\u00a0conduction abnormality, this difference can increase during exercise. Typically, however, this\u00a0value may remain unchanged within the entire range of programmed changes in rate.<\/li><\/ul><p><strong>Adaptable AV delay<\/strong><\/p><p>The PR interval normally shortens with exercise. The adaptation of the AV delay as the heart rate increases\u00a0is intended to mimic\u00a0this physiologic phenomenon; the same adaptation is imposed on the sensed and paced AV delay.<\/p><p>The specific characteristics of the adaptable AV delay will be presented in the chapter discussing the settings during exercise.<\/p><p>The adaptation of the AV delay that can occur when the pacemaker operates in DDDR, DDD, DDIR, DVIR, DOOR or VDD modes, simulates physiological response.<\/p><ul><li>the same variation is applied to the sensed and paced AV delay<\/li><li>the adaptable AV delay adapts the latter linearly as the heart rate varies<\/li><\/ul><p>\u00a0<\/p><p>Three programmable settings govern the adaptation of the AV delay at faster rates:<\/p><ul><li>the start rate: the shortening of the sensed and paced AV delay begins at that rate<\/li><li>the stop rate: the shortest sensed and paced AV delay does not shorten further from there and up to the programmed upper rate<\/li><li>the maximum variation: the greatest shortening (in ms) of the sensed and paced AV delays<\/li><\/ul><p><a href=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/06\/pm-mdt-elai-AV.png\"><img fetchpriority=\"high\" decoding=\"async\" class=\"aligncenter wp-image-10965 size-full\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/06\/pm-mdt-elai-AV.png\" alt=\"\" width=\"619\" height=\"450\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/06\/pm-mdt-elai-AV.png 619w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/06\/pm-mdt-elai-AV-300x218.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/06\/pm-mdt-elai-AV-18x12.png 18w\" sizes=\"(max-width: 619px) 100vw, 619px\" \/><\/a><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-182feb0 elementor-widget elementor-widget-heading\" data-id=\"182feb0\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Refractory periods of single chamber pacemakers<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6906c32 elementor-widget elementor-widget-text-editor\" data-id=\"6906c32\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>The refractory period is an interval following a paced or sensed event in the chamber containing the\u00a0pacing or sensing lead, during which the inhibited (SSI) or triggered (SST) pacemaker is not reset.\u00a0In a VVI pacemaker, the first part of the refractory period is a programmable, absolutely refractory\u00a0blanking period. It prevents the resetting of the pacemaker by the sensing of a) post-pacing ventricular\u00a0potentials, b) the end of the\u00a0QRS, or c) the T wave. The occurrence of an event during the blanking\u00a0period is not visible on the marker channels.<\/p><p>The programmed duration of the refractory period is usually between 220 and 350 ms.<\/p><p>The programming of an excessively short refractory period facilitates oversensing, which is reflected by a resetting of the escape interval and a slowing of the pacing rate. The programming of an excessively long refractory period incurs a risk of non-sensing of ventricular premature events. In that case, a stimulus might be delivered at the end of the pacing interval on the T wave of the extrasystole. In AAI pacemakers, the first part of the refractory period is a programmable blanking period. The refractory period prevents the resetting by an R wave sensed in the atrium (ventriculoatrial cross talk). Its duration must be as long as the AR interval (between the atrial stimulus and the R wave), which is longer than the PR interval, though not inordinately long to ensure atrial sensing up to the maximum sensor-driven rate.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-af3c81b elementor-widget elementor-widget-heading\" data-id=\"af3c81b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Refractory periods of double chamber pacemakers<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-66ef294 elementor-widget elementor-widget-text-editor\" data-id=\"66ef294\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>Atrial or ventricular pacing initiates different blanking and refractory periods in the paced chamber as\u00a0well as in alternate chambers in order to prevent cross talk.<br \/>Two types of refractory periods are implemented in DDD mode:<\/p><ol><li><em>The blanking periods\u00a0<\/em>completely deactivate sensing for a programmable or nonprogrammable\u00a0interval to protect against:<\/li><\/ol><ul><li style=\"list-style-type: none;\"><ul><li>post-pacing potentials in each chamber;<\/li><li>atrioventricular or ventriculoatrial crosstalk;<\/li><\/ul><\/li><\/ul><ol start=\"2\"><li><em>Longer refractory periods<\/em>, during which sensed events are included in the diagnosis of\u00a0arrhythmias and in the proper function of various algorithms. In contrast, a spontaneous event\u00a0sensed during a refractory period does not reset the synchronization interval.<br \/>The refractory periods prevent the resetting of the pacemaker by unwanted signals such as\u00a0retrograde P waves\u00a0or electrical interference.<br \/>It is noteworthy that in new pacemaker models, the differentiation between a) blanking (absence\u00a0of sensing and inscription of the signal on\u00a0the marker chain) and b) refractory period (preserved\u00a0sensing and presence on the marker chain) is less clear-cut. Thus, an event sensed during\u00a0blanking might be visible on the marker chain and interfere with the function of various\u00a0algorithms.<\/li><\/ol>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d2543c3 elementor-widget elementor-widget-image\" data-id=\"d2543c3\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr1\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIyOCwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjEucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"434\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1.png\" class=\"attachment-large size-large wp-image-4228\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1.png 923w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1-300x163.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1-768x417.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr1-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-c51eb2b elementor-widget elementor-widget-text-editor\" data-id=\"c51eb2b\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>Post atrial pacing ventricular blanking<\/strong><\/p><p>This programmable ventricular blanking period, triggered by an atrial stimulus, prevents sensing of\u00a0that stimulus by the ventricle, which would inhibit ventricular pacing and cause ventricular asystole\u00a0in a pacemaker-dependent patient presenting with complete AV block.<br \/>In the event of a ventricular extrasystole occurring during the post-atrial pacing ventricular blanking, a risk\u00a0is incurred of ventricular pacing during the vulnerable period. This blanking period is usually\u00a0programmed between 30 and 40 ms.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-db3249a elementor-widget elementor-widget-image\" data-id=\"db3249a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr2\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIyOSwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjIucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"440\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2.png\" class=\"attachment-large size-large wp-image-4229\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2.png 970w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2-300x165.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2-768x422.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr2-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-90b060c elementor-widget elementor-widget-text-editor\" data-id=\"90b060c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>The safety window<\/strong><\/p><p>The safety window is a ventricular sensing period that complements the post-atrial ventricular blanking.\u00a0It is implemented only after atrial pacing.\u00a0The sensing of a ventricular event after the post-atrial\u00a0ventricular blanking triggers a ventricular pulse at the end of this safety window. In case of ventricular\u00a0extrasystole, the pulse is triggered during its refractory period. In case it has sensed an artifact or a\u00a0late atrial stimulus, ventricular asystole is prevented.<br \/><br \/>This function is available when the pulse generator operates in DDD, DDI and DVI modes.<br \/><br \/>The duration of the safety window is 110 ms, or is identical to the paced AV delay if the latter is\u00a0&lt;110 ms. A short AV delay on the ECG indicates the occurrence of pacing in the safety window. While\u00a0ventricular safety pacing can be programmed ON or OFF, it is advised to systematically program it ON.\u00a0The annotations VS and VP are visible on the real-time monitor tracing, on the \u201cfrozen\u201d tracings and\u00a0on the printed tracings.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-77d5282 elementor-widget elementor-widget-image\" data-id=\"77d5282\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr3\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzMCwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjMucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"444\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3.png\" class=\"attachment-large size-large wp-image-4230\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3.png 973w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3-300x166.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3-768x426.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr3-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4418ba1 elementor-widget elementor-widget-text-editor\" data-id=\"4418ba1\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>The blanking period and the post-ventricular ventricular refractory period<\/strong><\/p><p>All events sensed or paced in the ventricle trigger a non-programmable ventricular blanking period,\u00a0the duration of which is dynamically modulated by the pacemaker according to the amplitude and duration\u00a0of the ventricular stimulus. The dynamic blanking prevents the repetitive sensing of a same event.<br \/>The ventricular refractory period (VRP) occurring after a sensed or paced ventricular event prevents\u00a0sensing of the T wave. A ventricular event sensed during the VRP does not recycle the pacemaker.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-6c6f30a elementor-widget elementor-widget-image\" data-id=\"6c6f30a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr4\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzMSwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjQucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"439\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4.png\" class=\"attachment-large size-large wp-image-4231\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4.png 974w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4-300x164.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4-768x421.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr4-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-aa2ded9 elementor-widget elementor-widget-text-editor\" data-id=\"aa2ded9\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>Atrial blanking and atrial post-atrial refractory period<\/strong><\/p><p>The atrial blanking and atrial refractory period (ARP) follow paced or sensed atrial events. The blanking period and the ARP are used in the AAI or AAT modes. If the pacemaker is programmed in MVP mode and functions in AAI mode, the ARP is automatically adjusted to 75% of the cardiac cycle, up to a maximum of 600 ms.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-3c439cf elementor-widget elementor-widget-image\" data-id=\"3c439cf\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr5\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzMiwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjUucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"444\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5.png\" class=\"attachment-large size-large wp-image-4232\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5.png 972w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5-300x167.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5-768x427.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr5-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d0dbc4c elementor-widget elementor-widget-text-editor\" data-id=\"d0dbc4c\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>Post-ventricular atrial blanking<\/strong><\/p><p>It is typically an absolute refractory period enforced in the atrium after ventricular sensing and pacing.\u00a0The PVAB represents the beginning of the PVARP.<br \/>Its role is to prevent the sensing by the atrial chain :<\/p><ul><li>of the ventricular pacing stimulus<\/li><li>of the spontaneous or paced QRS.<\/li><\/ul><p>It operates in DDD, DDI, VDD and VDI modes.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-dfa36cb elementor-widget elementor-widget-image\" data-id=\"dfa36cb\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr6\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzMywidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjYucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"436\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6.png\" class=\"attachment-large size-large wp-image-4233\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6.png 972w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6-300x164.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6-768x419.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr6-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-77ebb8f elementor-widget elementor-widget-text-editor\" data-id=\"77ebb8f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>The post-ventricular atrial refractory period<\/strong><\/p><p>The post-ventricular atrial refractory period (PVARP) is triggered by ventricular sensing or pacing and\u00a0is implemented in DDD, DDI and VDD modes.<\/p><p>Its main role is to prevent the sensing of retrograde P wave that might trigger a pacemaker mediated tachycardia in the P wave synchronous modes. When the pacemaker is in DDI mode, the PVARP prevents the atrial inhibition by sensing of retrograde P waves.<\/p><p>Its initial component is occupied by the PVAB, which was traditionally the absolutely refractory. Beyond the PVAB, the period is relatively refractory. During the PVARP, intrinsic atrial events might be sensed and identified as refractory (AR) on the event marker channel, though its does not modify the synchronization of the pacing intervals. Thus, an atrial event sensed during this period does not initiate an AV delay. When the pacemaker is in DDD or DDI modes, the expected atrial pacing is not inhibited.<\/p><p>In order to prevent the resetting of ventricular pacing by a retrograde P wave, the PVARP must be programmed at a value longer than the ventriculoatrial conduction time of the patient. The mean retrograde conduction time is between 220 and 280 ms, though might be longer, which requires an adaptation of the PVARP in each individual patient.<\/p><p>An excessively long PVARP might cause the development of 2:1 block during rapid sinus rhythm, when the pacemaker operates in P wave synchronous mode (DDD or VDD). To increase the 2:1 point, the PVARP may be configured to vary as a function of the sensor-indicated rate (sensor-modulated PVARP) or by the mean atrial rate (automatic PVARP). The details of the exercise-dependent settings will be reviewed in another chapter.<\/p><p>While they cannot reset the synchronization interval, the events sensed during the PVARP are used by the pacemaker toward functions that require a knowledge of their periodicity or frequency (mode switch, response to ventricular extrasystoles, adaptable AV delay, automatic PVARP and NCAP). The sensed refractory events are included in the telemetry of the event markers.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-5a7aa90 elementor-widget elementor-widget-image\" data-id=\"5a7aa90\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr7\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzNCwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjcucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"443\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7.png\" class=\"attachment-large size-large wp-image-4234\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7.png 974w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7-300x166.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7-768x425.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr7-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-14b0d69 elementor-widget elementor-widget-image\" data-id=\"14b0d69\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr8\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzNSwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjgucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"440\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8.png\" class=\"attachment-large size-large wp-image-4235\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8.png 974w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8-300x165.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8-768x423.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr8-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-4111a15 elementor-widget elementor-widget-image\" data-id=\"4111a15\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr9\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzNiwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjkucG5nIn0%3D\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"451\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9.png\" class=\"attachment-large size-large wp-image-4236\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9.png 964w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9-300x169.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9-768x433.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr9-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-1e56f3a elementor-widget elementor-widget-heading\" data-id=\"1e56f3a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t\t<h3 class=\"elementor-heading-title elementor-size-default\">Protection against pacemaker-mediated tachycardias<\/h3>\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-0170e2f elementor-widget elementor-widget-text-editor\" data-id=\"0170e2f\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>Onset, duration and rate of pacemaker-mediated tachycardia<\/strong><\/p><p><em>The onset of a PMT requires:<\/em><\/p><ul><li>the programming of a P wave synchronous mode (DDD or VDD)<\/li><li>intact retrograde conduction\u00a0loss of AV synchronization; a properly synchronized ventricular and atrial activity blocks<\/li><li>retrograde conduction.<br \/>Retrograde conduction is present on average in 40% of unselected patients who are paced at rest(up to 80% prevalence in patients paced\u00a0for sinus node dysfunction, considerably higher than in\u00a0patients paced for AV block). During exercise, the mean prevalence of retrograde conduction is 75%.\u00a0This high prevalence justifies an effective protection, which should be systematically programmed.<\/li><\/ul><p>\u00a0<\/p><p><em>The following events might promote AV dissociation, retrograde conduction and the onset of PMT:<\/em><\/p><ul><li>a ventricular extrasystole (the most frequent cause);<\/li><li>an atrial extrasystole with lengthening of the AV delay to respect the programmed upper rate;<\/li><li>an excessively long programmed AV delay; the nodo-hisian tissue has recovered its excitability\u00a0at the time of ventricular pacing;<\/li><li>an external interference or myopotentials sensed by the atrial chain;<\/li><li>an atrial sensing or pacing defect;<\/li><li>absence of PVARP extension after removal of a magnet, or exit from fallback upon 1:1 AV\u00a0re-association;<\/li><li>application and removal of magnet;<\/li><li>VDD mode programming in a patient in sinus rhythm at a rate slower than the programmed\u00a0back-up rate;<\/li><\/ul><p>\u00a0<\/p><p>PMT is a repetitive sequence in which the pacemaker responds to each retrograde P wave by pacing\u00a0the ventricle at a rapid rate, which, in turn, produces a retrograde P wave. This cycle repeats itself\u00a0indefinitely unless interrupted by retrograde block or by the intervention of a specific pacemaker\u00a0algorithm.<br \/>A long-lasting PMT may be poorly tolerated, with symptoms ranging from ill feeling or palpitations\u00a0to cardiac decompensation in patients suffering from underlying heart disease.<\/p><p><em>The rate of PMT depends on:<\/em><\/p><ul><li>the retrograde conduction time,\u00a0<\/li><li>the programmed upper rate,\u00a0<\/li><li>the existing AV delay.<\/li><\/ul><p>\u00a0<\/p><p>If the retrograde conduction time + the AV delay (at the upper rate) is shorter than the shortest pacing\u00a0cycle (60,000\/upper rate), the rate of the\u00a0PMT is equal to the programmed upper rate, the AV delay\u00a0being prolonged with each cycle.<\/p><p>If the retrograde conduction time + the AV delay (at the rate of the PMT) is longer than the shortest\u00a0pacing cycle (60,000\/upper rate), the rate of the PMT is slower than the programmed upper rate and\u00a0equal to 60,000\/(retrograde conduction time + AV delay), and the AV delay is that programmed at\u00a0the ongoing rate. This hypothesis is observed in approximately 35% of cases.<\/p><p><strong>Prevention of onset of pacemaker-mediated tachycardia<\/strong><\/p><p>Several measures can help prevent\u00a0PMT, including:<\/p><ul><li>the programming of a mode such as DDI which prevents the onset of PMT. It is a pacing mode,\u00a0which might not be suitable for some patients (absence of ventricular pacing synchronized with\u00a0sensed P waves).<\/li><li>the programming of a PVARP longer than the retrograde conduction time, which can be measured\u00a0at the time of implantation. One must keep in mind, however, that the programming ofan excessively long PVARP might cause intolerable 2: 1 AV block during exercise. The programming\u00a0of a PVARP, or adaptable AV delay, or both, can increase the exercise capacity. A PVARP\u00a0programmed at 300 ms prevents the development of PMT in a majority of patients.<\/li><li>avoidance of all instances that might promote a loss of AV synchrony.<\/li><li>programming of short instead of long AV delays<\/li><li>program a sufficient safety margin to ensure proper and permanent sensing and pacing<\/li><li>program bipolar atrial sensing to prevent the sensing of myopotentials or outside interferences<\/li><li>automatically lengthen the PVARP upon magnet removal<\/li><li>the response to premature ventricular complexes (PVC) prevents the tracking of retrograde P\u00a0waves originating from PVC. The pacemaker defines PVC as any sensed ventricular event that\u00a0follows another paced, refractory or sensed ventricular event in absence of interim atrial event.\u00a0When the PVC response is ON, a PVC initiates a 400-ms PVARP if its programmed value or the\u00a0on-going value is &lt;400 ms.<\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-a340099 elementor-widget elementor-widget-image\" data-id=\"a340099\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr10\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzNywidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjEwLnBuZyJ9\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"433\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10.png\" class=\"attachment-large size-large wp-image-4237\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10.png 975w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10-300x162.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10-768x416.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr10-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-59d5349 elementor-widget elementor-widget-text-editor\" data-id=\"59d5349\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><strong>Diagnosis of pacemaker-mediated tachycardia by the pacemaker<\/strong><\/p><p>Diagnosis of pacemaker-mediated tachycardia by the pacemaker\u00a0The anti-PMT intervention is available when the device functions in DDD, VDD, or MVP mode. With\u00a0MVP mode, the anti-PMT intervention functions only in DDD mode.<br \/>The pacemaker diagnoses a PMT when it detects 8 consecutive VA intervals which fulfill all these<br \/>conditions:<\/p><ul><li>VA interval &lt;400 ms<\/li><li>VA interval begins with a paced ventricular event<\/li><li>VA interval ends with a sensed atrial event<\/li><\/ul><p>Using the activity sensor-indicated rate, the pacemaker verifies that the eight consecutive VA intervals\u00a0are tracked retrograde P waves instead of an intrinsic accelerated atrial rhythm.<\/p><ul><li>if the sensor-indicated rate is below or equal to the ADL rate, an episode of PMT as defined by\u00a0the device is confirmed and therapy is delivered.<\/li><li>if the sensor-indicated rate is &gt; than the ADL rate, rapid sinus rhythm is diagnosed and no\u00a0therapy is delivered, and,<\/li><li>the pacemaker continues its monitoring of series of eight consecutive VA intervals along with\u00a0the sensor-indicated rate.<\/li><\/ul><p><strong>Anti-pacemaker-mediated tachycardia therapy<\/strong><\/p><p>This algorithm interrupts PMT by lengthening the PVARP and sensing the next retrograde atrial event\u00a0in the refractory period. This refractory event does not synchronize ventricular pacing and the\u00a0tachycardia is interrupted.<br \/>When a PMT is detected, a 400\u00a0ms PVARP is introduced after the 9th paced ventricular event. If a\u00a0PMT is ongoing, the extended PVARP ensures that the next sensed atrial event occurring within a\u00a0400\u00a0ms delay will be refractory.<br \/>Sinus tachycardia might prompt an anti-PMT intervention, causing a single P wave during the PVARP, consequently not tracked by the pacemaker.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d99d001 elementor-widget elementor-widget-image\" data-id=\"d99d001\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a href=\"http:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11.png\" data-elementor-open-lightbox=\"yes\" data-elementor-lightbox-title=\"schema_va_pr11\" data-e-action-hash=\"#elementor-action%3Aaction%3Dlightbox%26settings%3DeyJpZCI6NDIzOCwidXJsIjoiaHR0cHM6XC9cL2NhcmRpb2Nhc2VzLmNvbVwvd3AtY29udGVudFwvdXBsb2Fkc1wvMjAyNVwvMTFcL3NjaGVtYV92YV9wcjExLnBuZyJ9\">\n\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"800\" height=\"447\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11.png\" class=\"attachment-large size-large wp-image-4238\" alt=\"\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11.png 934w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11-300x168.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11-768x429.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2025\/11\/schema_va_pr11-18x10.png 18w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-89f1412 elementor-widget elementor-widget-text-editor\" data-id=\"89f1412\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p>Following an intervention, the anti-PMT function is suspended automatically for 90 sec, preventing\u00a0repetitive and unnecessary interventions in cases of rapid and stable intrinsic atrial rates.<\/p><p>The anti-PMT intervention function interacts with other pacemaker functions:<\/p><ul><li>non-competitive atrial pacing (NCAP) is automatically activated for one cycle after the 9th ventricular\u00a0paced event of a PMT episode. The function NCAP can shorten the next paced AV delay\u00a0to stabilize the ventricular rate.<\/li><li>if mode switch is programmed ON, the anti- PMT intervention is temporarily deactivated in\u00a0case the pacemaker switches to the atrial non-tracking mode. It is reactivated as soon as it has\u00a0returned to atrial tracking.<\/li><\/ul>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<div class=\"elementor-element elementor-element-d495f18 elementor-widget elementor-widget-text-editor\" data-id=\"d495f18\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><\/p><p><strong>P\u00e9riodes r\u00e9fractaires atriales &#8211; Medtronic<\/strong><\/p><p><span style=\"text-decoration: underline;\">P\u00e9riode r\u00e9fractaire atriale<\/span> <br \/>Si le stimulateur est programm\u00e9 sur un mode MVP, et fonctionne en mode ADI, la p\u00e9riode r\u00e9fractaire atriale est automatiquement ajust\u00e9e \u00e0 75% du cycle cardiaque jusqu\u2019\u00e0 un maximum de 600 ms.<\/p><p><span style=\"text-decoration: underline;\">Le blanking atrial post-ventriculaire (BAPV)<\/span><br \/>Sur la gamme des pacemakers Adapta et des pacemakers plus anciens, un \u00e9v\u00e9nement <br \/>atrial survenant dans cette p\u00e9riode n\u2019appara\u00eet pas sur la chaine des marqueurs et est <br \/>ignor\u00e9 par les fonctions de stimulation antibradycardique<\/p><p>Pour les stimulateurs les plus r\u00e9cents, comme l\u2019Ensura ou l\u2019Advisa (plateforme commune <br \/>avec celle des d\u00e9fibrillateurs), le comportement en r\u00e9ponse \u00e0 un \u00e9v\u00e9nement atrial survenant dans cette p\u00e9riode diff\u00e8re et est d\u00e9termin\u00e9 en fonction de deux param\u00e8tres programmables : l\u2019intervalle BAPV et la m\u00e9thode BAPV<\/p><ul><li>\u00a0si la m\u00e9thode BAPV est programm\u00e9e sur \u00ab absolue \u00bb : le fonctionnement est identique aux <br \/>pacemakers plus anciens et l\u2019\u00e9v\u00e8nement n\u2019appara\u00eet pas sur la chaine de marqueur<\/li><li>si la m\u00e9thode BAPV est programm\u00e9e sur \u00ab partielle \u00bb : un \u00e9v\u00e9nement atrial survenant dans cette <br \/>p\u00e9riode appara\u00eet sur le chaine de marquer et est \u00e9tiquet\u00e9 Ab ; cet \u00e9v\u00e8nement atrial ne d\u00e9clenche <br \/>pas de d\u00e9lai AV mais est comptabilis\u00e9 pour le diagnostic d\u2019arythmie atriale ; la sensibilit\u00e9 atriale <br \/>n\u2019est pas modifi\u00e9e<\/li><li>\u00a0si la m\u00e9thode BAPV est programm\u00e9e sur \u00ab partielle + \u00bb, le fonctionnement est identique au <br \/>pr\u00e9c\u00e9dent si ce n\u2019est qu\u2019apr\u00e8s un \u00e9v\u00e9nement ventriculaire d\u00e9tect\u00e9 ou stimul\u00e9, le seuil de d\u00e9tection <br \/>atriale augmente et le dispositif devient moins sensible (pour \u00e9viter l\u2019\u00e9coute crois\u00e9e)<\/li><\/ul><p><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-95082cc e-flex e-con-boxed e-con e-parent\" data-id=\"95082cc\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-df773a3 e-flex e-con-boxed e-con e-parent\" data-id=\"df773a3\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-f497963 elementor-widget elementor-widget-text-editor\" data-id=\"f497963\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><\/p><p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-11166\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/PM-MEDTR-300x139.png\" alt=\"\" width=\"300\" height=\"139\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/PM-MEDTR-300x139.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/PM-MEDTR-768x355.png 768w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/PM-MEDTR-18x8.png 18w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/PM-MEDTR.png 798w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/p><p><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-d36c362 e-flex e-con-boxed e-con e-parent\" data-id=\"d36c362\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-d97bb24 elementor-widget elementor-widget-text-editor\" data-id=\"d97bb24\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<h3><\/h3><h3><strong>D\u00e9lai AV &#8211; Medtronic<\/strong><\/h3><p><span style=\"text-decoration: underline;\">D\u00e9lai AV &#8211; Medtronic<\/span><\/p><p>L\u2019adaptation du d\u00e9lai AV qui peut se produire lorsque le stimulateur cardiaque fonctionne <br \/>en mode DDDR, DDD, DDIR, DVIR, DOOR ou VDD simule cette r\u00e9ponse physiologique. <\/p><ul><li>La m\u00eame variation s\u2019applique au d\u00e9lai AV d\u00e9tect\u00e9 et au d\u00e9lai AV stimul\u00e9<\/li><li>Le d\u00e9lai AV adaptatif s\u2019ajuste de mani\u00e8re lin\u00e9aire en fonction des variations de la fr\u00e9quence <br \/>cardiaque<\/li><\/ul><p>Trois param\u00e8tres programmables r\u00e9gissent l\u2019adaptation du d\u00e9lai AV \u00e0 des fr\u00e9quences plus <br \/>\u00e9lev\u00e9es :<\/p><ul><li>\u00a0La fr\u00e9quence de d\u00e9part : le raccourcissement du d\u00e9lai AV d\u00e9tect\u00e9 et stimul\u00e9 commence \u00e0 cette fr\u00e9quence*<\/li><li>La fr\u00e9quence d\u2019arr\u00eat : le d\u00e9lai AV d\u00e9tect\u00e9 et stimul\u00e9 le plus court ne se raccourcit plus \u00e0 partir de l\u00e0 et jusqu\u2019\u00e0 la fr\u00e9quence sup\u00e9rieure programm\u00e9e<\/li><li>\u00a0La variation maximale : le raccourcissement maximal (en ms) des d\u00e9lais AV d\u00e9tect\u00e9s et stimul\u00e9s<\/li><\/ul><p>\u00a0<\/p><p><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-11174\" src=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/pm-delai-av-medt-300x217.png\" alt=\"\" width=\"300\" height=\"217\" srcset=\"https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/pm-delai-av-medt-300x217.png 300w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/pm-delai-av-medt-18x12.png 18w, https:\/\/cardiocases.com\/wp-content\/uploads\/2026\/07\/pm-delai-av-medt.png 736w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/p><p><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t<div class=\"elementor-element elementor-element-9ef714f e-flex e-con-boxed e-con e-parent\" data-id=\"9ef714f\" data-element_type=\"container\" data-e-type=\"container\">\n\t\t\t\t\t<div class=\"e-con-inner\">\n\t\t\t\t<div class=\"elementor-element elementor-element-1f86b32 elementor-widget elementor-widget-text-editor\" data-id=\"1f86b32\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t\t\t\t\t\t<p><\/p><h3><strong>Prise en charge des TRE &#8211; Medtronic<\/strong><\/h3><p><span style=\"text-decoration: underline;\">La pr\u00e9vention du d\u00e9marrage des TRE<\/span><br \/>Lorsque la r\u00e9ponse aux ESV est sur Marche, une ESV (tout \u00e9v\u00e9nement ventriculaire d\u00e9tect\u00e9 qui suit un autre \u00e9v\u00e9nement ventriculaire stimul\u00e9, r\u00e9fractaire ou d\u00e9tect\u00e9 sans qu\u2019il y ait un \u00e9v\u00e9nement atrial interm\u00e9diaire) d\u00e9clenche une PRAPV de 400 ms si la valeur programm\u00e9e ou la valeur en cours est inf\u00e9rieure \u00e0 400 ms.<\/p><p><span style=\"text-decoration: underline;\">Diagnostic d\u2019une TRE par le stimulateur (dispositifs anciens)<\/span><br \/>Si le stimulateur d\u00e9tecte une onde P hors p\u00e9riodes r\u00e9fractaires, \u00e0 un intervalle fixe <br \/>pendant plusieurs cycles ventriculaires stimul\u00e9s, une TRE est suspect\u00e9e. Le stimulateur d\u00e9finit l\u2019apparition d\u2019une TRE lorsqu\u2019il d\u00e9tecte huit intervalles VA cons\u00e9cutifs qui remplissent tous les conditions suivantes :<\/p><ul><li>l\u2019intervalle VA est inf\u00e9rieur \u00e0 400 ms<\/li><li>l\u2019intervalle VA d\u00e9bute par un \u00e9v\u00e9nement ventriculaire stimul\u00e9<\/li><li>\u00a0l\u2019intervalle VA finit par un \u00e9v\u00e9nement atrial d\u00e9tect\u00e9<\/li><\/ul><p>Sur les huit intervalles VA cons\u00e9cutifs, le stimulateur essaie de diff\u00e9rencier TRE et <br \/>tachycardie sinusale en contr\u00f4lant la fr\u00e9quence du capteur d\u2019activit\u00e9 :<\/p><ul><li>si la fr\u00e9quence du capteur est inf\u00e9rieure ou \u00e9gale \u00e0 la fr\u00e9quence AQ, la pr\u00e9sence d\u2019un \u00e9pisode de TRE tel qu\u2019il est d\u00e9fini par le stimulateur est admise et l\u2019intervention th\u00e9rapeutique s\u2019ensuit<\/li><li>si la fr\u00e9quence du capteur est sup\u00e9rieure \u00e0 la fr\u00e9quence AQ, la pr\u00e9sence d\u2019un rythme sinusal rapide est admise et aucune intervention th\u00e9rapeutique ne s\u2019ensuit<\/li><li>\u00a0le stimulateur continue \u00e0 contr\u00f4ler chaque s\u00e9rie de huit intervalles VA cons\u00e9cutifs ainsi que la <br \/>fr\u00e9quence du capteur<\/li><\/ul><p>\u00a0<\/p><p><span style=\"text-decoration: underline;\">Intervention anti-TRE (anciens stimulateurs)<\/span><br \/>Lorsqu\u2019une TRE est d\u00e9tect\u00e9e, le stimulateur intervient en appliquant une PRAPV de 400 <br \/>ms apr\u00e8s le neuvi\u00e8me \u00e9v\u00e9nement ventriculaire stimul\u00e9. Si une TRE est effectivement en cours et que le d\u00e9lai VP-AS est inf\u00e9rieur \u00e0 400ms, l\u2019\u00e9v\u00e9nement atrial suivant tombe dans la PRAPV, n\u2019est pas synchronis\u00e9 et la TRE s\u2019arr\u00eate.<br \/>Apr\u00e8s une intervention, la fonction d\u2019intervention anti-TRE est automatiquement <br \/>suspendue pendant 90 secondes. Ceci \u00e9vite les interventions inutiles r\u00e9p\u00e9t\u00e9es en cas de fr\u00e9quences tachycardies sinusales rapides.<\/p><p>\u00a0<\/p><p><span style=\"text-decoration: underline;\">Algorithme anti-TRE (dispositifs r\u00e9cents)<\/span> <br \/>Une phase de confirmation du diagnostic de TRE (modification du d\u00e9lai AV et analyse de l\u2019impact dur l\u2019intervalle VP-AS suivant) a \u00e9t\u00e9 ajout\u00e9e avant d\u2019essayer d\u2019interrompre la tachycardie en allongeant la PRAPV. Cette modification a pour objectif d\u2019am\u00e9liorer la sp\u00e9cificit\u00e9 de l\u2019algorithme et de r\u00e9duire les interventions inappropri\u00e9es sur tachycardie sinusale ou tachycardie atriale.<\/p><ul><li>apr\u00e8s 8 cycles cons\u00e9cutifs VP-AS rapides, le d\u00e9lai AV est allong\u00e9 sur un cycle (+ 50 ms)<\/li><li>l\u2019intervalle VA est alors analys\u00e9 sur les 2 cycles qui suivent<\/li><li>si l\u2019intervalle VA reste constant, une TRE est suspect\u00e9e<\/li><li>\u00a0cette s\u00e9quence est r\u00e9p\u00e9t\u00e9e b3 fois (allongement du d\u00e9lai AV et analyse de la stabilit\u00e9 de l\u2019intervalle VA sur les 2 cycles qui suivent)<\/li><li>\u00a0si l\u2019intervalle VA reste constant sur les 3 s\u00e9quences, suspicion de TRE et allongement de la PRAPV \u00e0 une valeur de 400 ms sur un cycle\u00a0<\/li><\/ul><p><\/p><p>\u00a0<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Medtronic &#8211; AV delays, refractory periods, and management of tachycardia Content The atrioventricular delay The AV delay determines the longest time interval between an atrial event and the programmed\u00a0delivery of a ventricular pacing pulse. This interval\u00a0is the electronic equivalent of the PR interval. The programming of the AV delay intends to ensure optimal mechanical coordination [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":49,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-751","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.0 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Medtronic AV Delay &amp; Refractory Periods Guide | Cardiocases<\/title>\n<meta name=\"description\" content=\"Complete Medtronic pacemaker guide: AV delays, PVARP, refractory periods &amp; tachycardia management with real ECG tracings &amp; programming tips from electrophysiologists.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" 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