VT rate hovering around the limit of the VF monitor zone

N° 11
Manufacturer Abbott Device ICD Field Sensing

This 74-year-old man presenting with advanced dilated cardiomyopathy, a 20% left ventricular ejection fraction and multiple episodes of VT, received an Atlas dual chamber ICD. He was on a regimen of amiodarone and beta-adrenergic blocker and presented with decompensated heart failure.

Graph and trace

1: VT with AV dissociation; the ventricular EGM oscillate between the VT (T) and the sinus (VS) zones;
2: Spurious diagnosis of return to sinus rhythm (5 consecutive VS or with intervening unclassified intervals); VT is still on-going;
3: DDI episode pacing mode, as 4 T or F classified cycles were detected after the previous return of sinus rhythm;
4: Diagnosis of VT in the monitor zone (the VT counter was saturated);
5: Spontaneous termination;
6: Confirmed diagnosis of return of sinus rhythm.


The diagnosis of VT was evident in presence of AV dissociation, though was delayed, as the rate of the arrhythmia hovered around the lower limit of the monitor zone. In secondary prevention, the zones are usually programmed according to the rate of the clinical tachycardia. In this patient, the higher dose of beta-adrenergic blocker and the addition of amiodarone slowed the rate of the tachycardias. These prolonged and untreated episodes of VT contributed to a hemodynamic deterioration. A zone of slow VT therapy with several sequences of ATP tailored to this patient was added.

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