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Introduction Implantable cardioverter-defibrillators (ICDs) for cardiac resynchronization therapy (CRT-D) with the capability of LV sensing enable the assessment of interventricular delays in ventricular (VT) and supraventricular tachycardias (SVT). Methods and Results In total, 1078 EGM recordings of VT or VF episodes were investigated that have been transmitted via Home Monitoring. Only those EGM recordings showing the onset of the tachyarrhythmia were used for investigation. In the 623 cases eligible for evaluation leftsided VTs could be identified in 349 cases, right-sided VTs in 252 cases. SVTs with a 1:1 antegrade conduction were found in 22 cases. VT can present three different interventricular delays whereby the right-ventricular sensed event (RVs) is either preceding the left-ventricular sensed event (LVs), or the LVs is preceding RVs, or there can be a simultaneous occurrence of RVs and LVs. In SVTs, either the LVs events were delayed or occurred simultaneously with the RVs events. SVT cases with LVs preceding the RVs events were not found. Conclusion The LV-EGM channel enables to distinguish between left- and right-sided premature ventricular complexes. The assessment of the interventricular delay in VTs is useful to differentiate between a possible apical-, left- or right-sided origin of the VT but not to identify SVTs.

Alternans of the ventricular electrogram (VEGM) during ventricular tachycardia (VT) is a rare cause of ventricular undersensing by an implantable cardioverter-defibrillator (ICD). This report describes a patient with a St. Jude ICD who exhibited sustained monomorphic VT associated with surface QRS alternans, alternating cycle lengths, alternans of the VEGM causing intermittent undersensing of the smaller component, and intermittent 2:1 counting of ventricular intervals during 1:1 sensing in response to the ICD detection algorithm. VEGM undersensing was corrected noninvasively simply by programming the threshold start from 62.5% to 50% which increased the sensitivity based on the amplitude of the VEGM. This maneuver did not affect the satisfactory and stable defibrillation threshold.

Understanding of the traditional Wenckebach phenomenon is enhanced by using a modified ladder diagram where AV conduction in any cycle is represented by a slanted line in the AV bar together with similar AV conduction lines of all the preceding cycles. The diagram facilitates calculation of the duration of RR intervals (equal to the basic PP or sinus interval minus the PR or AV increment applied to this particular cycle) and the duration of the pause (equal to 2 × PP or sinus interval minus the sum of all the increments applied to the AV delay). The modified Wenckebach diagram should help students understand the mysterious clustering of QRS complexes or “paradoxical” increase of the ventricular rate that occurs during a Wenckebach sequence. Ann Noninvasive Electrocardiol 2012;17(1):3–7

ispartof: Tijdschrift voor Geneeskunde status: published

Transthoracic external cardioversion is, if carried out properly, a highly effective cardioversion modality for most patients with atrial fibrillation. Failure to return to sinus rhythm (even for one or two beats) can be related to high transthoracic impedance. Internal cardioversion may offer a safe and worthwhile alternative for these patients, in need of sinus rhythm. This technique, mostly requiring only mild sedation, is actually performed in many electrophysiology centers. Because recurrence rates of atrial fibrillation seem to be the same for both methods, this invasive technique should be considered in patients with a rather low chance of atrial fibrillation recurrences. We present a case report of an extremely obese woman, resistant to external cardioversion. She successfully underwent internal low-energy cardioversion.