A 64-year-old man recipient of a Virtuoso DR dual chamber ICD, implanted for secondary prevention because of ischemic cardiomyopathy, a left ventricular ejection fraction of 25% and documented VT, presented with episodes of SVT stored in the device memory at a routine ambulatory visit.
At each interrogation of the defibrillator, all episodes stored in the device memory as VF, VT or SVT must be reviewed. A diagnosis of SVT made by the device may be correct (AF, atrial flutter or atrial tachycardia) or incorrect (VT, VF, oversensing). The demonstration of true episodes of AF may influence the treatment (e.g. introduction or increase of anti-arrhythmic therapy, consideration of anticoagulation, reprogramming of the ICD). The minimum duration and number of AF episodes, and the overall AF burden that mandates the introduction of anticoagulation, remain controversial.
Note : The EGM of Medtronic defibrillators include all atrial events, including those falling in the blanking periods (Ab). These events are not included in the pacing timing cycle, though are used to diagnose arrhythmias.
Detection of an episode of AT/AF in the zone of atrial tachycardias. The lower limit for these tachycardias was programmed at 150 bpm. The atrial rate of this SVT was above this limit.
