Anti-tachycardia pacing in the VF zone - Viva Quad CRT-D

Medtronic

Patient

Male implanted with a triple chamber defibrillator (Viva Quad CRT-D) for ischaemic cardiomyopathy.

Tracing

1-What diagnosis is suggested by the interval plot?
Probable episode of monomorphic VT detected in the VF zone and treated by a burst which appears to be effective

2- What therapy is delivered by the device?
The episode is detected in the VF zone; when the initial VF counter is filled, a burst during charging is delivered.

3- What does the «abandon» message mean?
Charging of capacitors began as soon as the VF counter was filled; the burst was effective with termination of the arrhythmia; after 4 consecutive paced ventricular cycles, the criterion for confirming persistence of the arrhythmia is not met (criterion of 2/5 rapid cycles) and charging is interrupted (therapy abandoned).

Take home message

Various studies have shown that a significant proportion of rapid ventricular arrhythmias (cycle length < 320 ms) classified in the VF zone are regular and monomorphic.
Although it is clear that delivering a shock during an episode of ventricular fibrillation is the only therapy likely to re-establish a viable rhythm, programming should be optimized to minimise number of shocks delivered (inappropriate or appropriate but avoidable) as much as possible.
A shock delivered to a conscious patient is painful and significantly increases battery consumption; a series of shocks to the same patient is associated with a risk of premature battery depletion and a significant deterioration in quality of life (numerous cases of depression or anxiety induced by a series of shocks have been described).
An endocardial shock is accompanied by microscopic myocardial lesions, an increase in cardiac enzymes (troponin, CK, myoglobin) and macroscopic lesions that are all the more significant with higher energy delivery (momentary drop in left ventricular ejection fraction and cardiac output, particularly in patients with already impaired contractility).
The PainFree Rx study (prospective, randomised, multi-centre study) showed that a single ATP sequence (8 beats at 88%) terminated a significant proportion of rapid tachycardias in the VF zone and significantly improved quality of life, by reducing the number of shocks delivered without increasing the risk of sudden death, syncope or accelerated tachycardia. Therefore, delivering an ATP sequence in the VF zone is often effective, painless, reduces battery consumption and improves quality of life.
It is now recommended that at least one ATP sequence is programmed as first-line treatment for tachycardias up to 230 beats/minute, with bursts favoured over ramps (at least 8 stimuli with 88% coupling).

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