{"id":11151,"date":"2026-07-02T08:15:42","date_gmt":"2026-07-02T08:15:42","guid":{"rendered":"https:\/\/cardiocases.com\/?post_type=ecg_case&p=11151"},"modified":"2026-07-02T11:33:34","modified_gmt":"2026-07-02T11:33:34","slug":"trace-4-8-failure-of-ventricular-sensing","status":"publish","type":"ecg_case","link":"https:\/\/cardiocases.com\/fr\/ecg_case\/trace-4-8-failure-of-ventricular-sensing\/","title":{"rendered":"Trace 4.8: Failure of ventricular sensing"},"content":{"rendered":"","protected":false},"featured_media":9670,"template":"","ecg_case_type":[253],"language_ecgcase":[258],"class_list":["post-11151","ecg_case","type-ecg_case","status-publish","has-post-thumbnail","hentry","ecg_case_type-cardiac-pacing","language_ecgcase-english"],"acf":{"ecg_case_title":"Trace 4.8: Failure of ventricular sensing","patient_description":"A man with a pacemaker implanted in VVI mode due to an atrial condition (alternating between sinus node dysfunction and episodes of atrial fibrillation); follow-up electrocardiogram","quiz_question":"Regarding this ECG, which of the following is\/are the correct answer(s)?","quiz_answer_1":"This is sinus rhythm","quiz_answer_2":"There is a sinus node dysfunction","quiz_answer_3":"There is atrial fibrillation","quiz_answer_4":"There is failure of ventricular capture","quiz_answer_5":"There is failure of ventricular sensing","correct_answer":["C","E"],"ecg_image":9670,"ecg_description":"The electrocardiogram shows atrial fibrillation; spontaneous QRS complexes are not detected and do not inhibit ventricular pacing, which is effective; ventricular detection failures;","ecg_info_box":"Atrial or ventricular underdetection is reflected on the electrocardiogram by the presence of fixed-frequency pacing artifacts despite the presence of spontaneous complexes that do not inhibit pacing.","commentary_ecg":"This trace reveals ventricular underdetection, which can sometimes lead to pacing during the vulnerable period. In the absence of proper detection, the pacemaker operates in asynchronous mode, making it impossible to inhibit spontaneous ventricular contractions. There is a low but non-zero theoretical risk of inducing a malignant polymorphic ventricular arrhythmia that could compromise the patient\u2019s survival. Furthermore, this unnecessary pacing leads to energy consumption that is detrimental to the device\u2019s lifespan.\r\n\r\nSensitivity, expressed in millivolts (mV), describes the pacemaker\u2019s ability to correctly detect spontaneous cardiac events. A pacemaker is equipped with input filters that specifically detect P waves in the atrium and R waves in the ventricle based on the analysis of three characteristics of these electrical signals: the frequency spectrum, the slope, and the amplitude.\r\n\r\nProper sensitivity level programming should allow for the detection of all spontaneous cardiac events occurring in the implanted chamber while avoiding the detection of events of other types (crosstalk with detection of cardiac signals from the other chamber, myopotentials, interference, etc.). Programming for bipolar detection increases detection specificity compared to unipolar detection by limiting the risk of picking up extracardiac signals or cross-talk, and allows for the programming of high sensitivity values. In contrast, in a unipolar configuration, the risk of cross-sensing or picking up extracardiac signals necessitates programming a lower sensitivity level, which carries an increased risk of underdetection.\r\n\r\nTraditionally, unlike defibrillators, pacemakers operated with a stable, fixed sensitivity throughout the cardiac cycle. Increasingly, even though the detection requirements are not the same (it is crucial for a defibrillator to detect and treat very rapid, polymorphic, and microvolt ventricular arrhythmias), modern pacemakers offer adaptive sensitivity (a sensitivity level that varies depending on the amplitude of the detected R-wave or P-wave) with a gradual increase in sensitivity over the course of the cardiac cycle (allowing for the detection of low-amplitude signals without overdetecting the T-wave).\r\n\r\nProgramming a more appropriate adaptive ventricular sensitivity resolved the issue in this patient.","ecg_info_post_answer":"\"\""},"yoast_head":"\nTrace 4.8: Failure of ventricular sensing - Cardiocases<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/cardiocases.com\/fr\/ecg_case\/trace-4-8-failure-of-ventricular-sensing\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Trace 4.8: Failure of ventricular sensing - 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