Poorly-discriminated ventricular tachycardia

Patient

59-year-old man implanted with a Lumax 740 DR-T dual-chamber ICD for dilated cardiomyopathy with VT episodes; event report (yellow color) in the setting of a classified VT1 and a SVT.

Trace

Telecardiology tracing 1

tachycardia in the VT1 zone initially with a 1:1 atrioventricular ratio; the ventricular events are classified Tsin (sinus tachycardia);
interruption of retrograde conduction with ventricular rhythm faster than the atrial rhythm (pathognomonic of a VT); discrimination in the PP>RR zone;
diagnosis of VT1 in the PP>RR arm;
delivery of 6 ATP sequences;

Telecardiology tracing 2

tachycardia in the VT1 zone with a 1:1 atrioventricular ratio; the ventricular events are classified Tsin (sinus tachycardia); note that the ventricular morphology is perfectly similar to that of the previous episode;
SVT classification in the PP=RR arm; average PP at initial classification 332 ms, average RR during at classification 336 ms; stable rhythm, with measured stability at 8 ms for a 24-ms threshold; stable PP intervals; stable PR intervals without monotonous change; the sudden onset criterion is not fulfilled (measured at 18% for a programmed threshold of 20%); the diagnosis made by the device is therefore that of SVT (sinus tachycardia).

Comments

During a 1:1 tachycardia, a transient retrograde ventriculo-atrial block allows confirming the diagnosis of VT. The second episode is misdiagnosed as SVT by the device (sinus tachycardia). The differential diagnosis between VT and sinus tachycardia is highly challenging, if not impossible, on the basis of the analysis to this tracing alone. The first episode allows a diagnosis of certainty. Indeed, the interruption of retrograde conduction (V>A) reveals the ventricular origin of the tachycardia. In a patient presenting multiple episodes of 1:1 tachycardia, it is very important to analyze all of the tracings in search of an anterograde (SVT) or retrograde block (VT), which provides a diagnosis of certainty.

As with a single-chamber ICD, it is possible to program on the latest generation of dual-chamber devices, a discrimination based on the morphology analysis. This criterion is not featured as an addition to the SMART algorithm, the physician having to choose between discrimination based on the morphology or on SMART.

Pacing & Defibrillation

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