Dual chamber discrimination: V=A
This 51-year-old man presenting with a severely dilated cardiomyopathy, recipient of a St Jude medical dual chamber ICD, was seen in consultation for evaluation of palpitations.
- sinus rhythm (AS-VS);
- tachycardia detected in the fast VT zone (T2) with mode switch to DDI at the 4th short ventricular cycle, starting suddenly with an atrial extrasystole, thus suggesting an atrial origin of the tachycardia;
- regular 1:1 tachycardia without change in morphology (100% concordance with the reference morphology). There is subtle, though noteworthy slowing of the tachycardia, which is then detected in the slow VT zone (T). The episode is accurately classified as SVT;
- spontaneous termination and return to sinus rhythm after 5 consecutive VS.
This was an accurately discriminated atrial tachycardia. In atrial tachycardia, 1 out of 2 criteria usually indicates SVT, since the onset is sudden (VT) and morphology is unchanged (SVT). Only the “All” programming allows an effective discrimination between VT and atrial tachycardia. Conversely, the programming of “Or” may promote the delivery of inappropriate therapy.