Implanted Cardioverter-Defibrillator

Report:

Implanted cardioverter-defibrillator (ICD) readout 1

Ventricular tachycardia 152 – 162/min 4

Burst overdrive pacing 190-245/min 4

Sinus rhythm 95/min 1

Comment:

The patient had numerous runs of VT which failed to activate the ICD because the rate was generally below 160/min; the current recording was taken after the ICD had been re-programmed to start overdrive pacing for lower ventricular rates, 150-160/min.

The morphology of the complexes in this digital readout has nothing to do with their origin. The “broad-complex” bursts are accelerating runs of ventricular pacing, programmed to take place whenever the ventricular rate is above a pre-set value. This does not distinguish between VT and SVT. The “narrow complexes” are native ventricular beats of whatever origin sensed and recorded by the ICD. From the rate – and the rate alone – one can deduce that the last pacing “ramp” in the bottom strip has been successful in abolishing VT and restoring sinus rhythm.

Had the ICD not succeeded, it would have gone a step further, delivering low-energy intracardiac shocks. This can be felt by the patient and is quite unpleasant.

Below (Fig 85a) is a summary of the entire 100 seconds episode, with graph of the heart rate during it. It can be seen that five burst of “straight” pacing at increasing speeds (lower V-V intervals) were unsuccessful, as were the first and the second episode of accelerating “ramp” pacing. The third ramp succeeds: its readout is shown on the preceding page.