Unsuccessful ATP during capacitor charge followed by shock
Patient
A 64-year-old recipient of a Concerto CRT-D, presented with ischemic cardiomyopathy, left bundle branch block, lightheadedness and perception of internal shock.
Trace
- Sinus rhythm, biventricular stimulation (AS-BV);
- Sustained FVT at a rate of approximately 240 bpm, with AV dissociation; tachycardia cycle length between the VF (FS) and the FVT via VF zone (TF*), Within the 8 last cycle, there is at least one short interval;
- VF is detected (FD), triggering simultaneously the charge of the capacitors and the delivery of first therapy (VF Tt1 ATP during charge);
- Burst of 8 consecutives pulses at a fixed cycle length of 240 ms during charge of the capacitors;
- Acceleration and disorganization of the tachycardia to polymorphic VT to the VF zone; during the charge of the capacitors, the ventricular EGM are labeled VS despite being very rapid and inside the VF zone;
- CE : end of capacitor charging and delivery of a 34.8 J shock without delay;
- Episode ended.
Comments
As explained for the previous tracing, if ATP delivered during the charge of the capacitors fails to terminate the tachycardia, the charge continues uninterrupted. ATP causes no delay and the shock is delivered on time. On the present tracing, the tachycardia is disorganized after ATP, which might have been spontaneous or a proarrhythmic effect of ATP. This particular patient had received a CRT-D. The superior efficacy and safety of biventricular versus conventional RV ATP delivery remains to be shown.
Take home message
Episode of tachycardia in the VF zone prompting a shock after failure of ATP during charge of the capacitors; the episode lasted a total of 13 sec.
