Anti-tachycardia pacing in the VT zone - Visia XT VR

Patient

Male implanted with a single chamber defibrillator (Visia XT VR) for ischaemic cardiomyopathy.

Trace

1-What diagnosis is suggested by the interval plot?
The plot shows a probable arrhythmic episode with sudden acceleration into the VT zone; a burst is delivered with probable termination of the arrhythmia; the plot on this single-chamber defibrillator does not allow us to differentiate with certainty between ventricular tachycardia and supra-ventricular tachycardia.

2- What is your final diagnosis?
This is a regular, monomorphic tachycardia with QRS complexes that appear wide on the shock channel; the burst is effective with termination of the arrhythmia; the morphology of QRS complexes post-termination is different from the morphology during tachycardia; therefore the diagnosis of ventricular tachycardia is very likely.

Take home message

A priority during programming is to reduce the number of shocks delivered without compromising patient safety; ideally, this is achieved by interrupting the tachycardia with the least aggressive and least painful therapy possible; for organised tachycardias, ATP is preferred over a shock as first-line therapy since it is less painful and limits battery consumption; moreover, potentially deleterious effects of device based shocks have been clearly demonstrated.
The principle underlying ATP is the existence of an excitable gap in a reentrant circuit such that rapid pacing can generate a new activation front that collides with the tachycardia circuit and interrupts it; the ventricle must therefore be paced at a higher rate than that of the tachycardia.
The efficacy of this type of therapy has been demonstrated for a wide range of ventricular tachycardia with rates of up to 240 beats/minute; one or more ATP sequences can terminate up to 90% of ventricular tachycardias of less than 200 beats/minute, with a moderate risk of acceleration of approximately 1 to 5%.
These observations have redefined the role of the implantable cardiac defibrillator as a device that offers ATP as a first line treatment, and possible defibrillation as a back-up.
One or more ATP sequences can be programmed empirically without the need to test efficacy with an electrophysiology study.

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