Termination of sustained ventricular tachycardia by ultrarapid subthreshold stimulation in humans.

Abstract

Our purpose was to investigate the efficacy, safety, and electrophysiological mechanism of ultrarapid subthreshold electrical stimulation in terminating sustained ventricular tachycardia (VT) in humans. Fifteen patients with inducible sustained hemodynamically stable VT and whose VT cycle length ranged between 295 and 440 msec (337 + 60 msec) were included in this study. The stimulation threshold and ventricular myocardial elfective refractory period were determined during VT, and the values ranged between 0.4 and 1.2 mA (mean, 0.7 0.3 mA) and between 185 and 245 msec (mean, 225 + 20 msec), respectively. Trains of ultrarapid subthreshold stimulation were delivered with cycle lengths of 100 to 10 msec in decremental steps of 10 msec. A 5-second pause was allowed between each step (decrement). A 2-msec pulse width was used in all patients, and a 4-msec pulse width was also tested in eight patients. Any apparent captured beat was disregarded. In eight (53%) patients, ultrarapid subthreshold stimulation terminated VT, and in the remaining seven (47%) patients, it did not. The lowest subthreshold stimulation that effectively terminated VT was 0.05 mA. In 10 patients, the site of early activity during VT was determined by endocardial catheter mapping, and subthreshold stimulation more effectively terminated VT in eight patients when it was applied close to the site of early activity. In seven patients who underwent mapping-guided arrhythmia surgery, subthreshold stimulation was applied close to the site of early activity and successfully terminated VT. In no patient did subthreshold stimulation produce acceleration of VT or induce ventricular fibrillation. We conclude that ultrarapid subthreshold stimulation, when applied appropriately, provides a safe and effective method for termination of VT in humans. Further investigations and experiences with this method are warranted. (Circulation 1988;78:1135-1143 S ubthreshold electrical stimulation delivered within the effective refractory period is reported to inhibit the response to extrastimuli that ordinarily produce a response in human heart.' The electrophysiological mechanism of this phenomenon has recently been investigated and is thought to be due to increased local refractoriness.

Spatiotemporally Controlled Cardiac Conduction Block Using High-Frequency Electrical Stimulation

“…Using HF stimulation, we have been able to generate reversible inhibition for up to 5 minutes. While short durations (seconds) have already been proven effective in termination of arrhythmia or ablation guidance [2], [9]–[11], [18], [19], the ability to block conduction for longer durations provides further flexibility in deployment. This might prove especially useful in cardiac mapping, RF ablation guidance or in vitro models, where longer durations might be desirable (increased time for assessing impact of inhibition) or even necessary (sustained conduction blocks for reentry models).…”

Sustained ventricular tachycardia in structural heart disease

“…Isolated mid-diastolic potentials are typically recorded at these points. A stimulus that fails to capture the ventricles but interrupts the tachycardia is also indicative that the pacing site is at a protected zone that composes or is near the critical isthmus [65].…”

Subthreshold Stimulation in Three Types of Reentrant Supraventricular Tachycardia. Correlation With the Results of Catheter Ablation.

“…Several studies have demonstrated that STS can terminate reentrant ventricular and supraventricular tachycardia without myocardial capture, [1][2][3][4][5] and although the methods for STS are differed among the studies, none reported any complications. We used STS of a direct current similar to that adopted by Willems et al, 5 and we also did not observed any serious complications, such as atrial or ventricular fibrillation, during STS.…”

“…Although STS has been reported to modulate cardiac electrophysiologic properties and terminate various types of tachycardia, [1][2][3][4][5]15,16 the mechanism of this phenomenon has not been fully clarified. The local capture and unpropagate stimulus might be one possible explanation, 17 but the termination of tachycardia without any change in the activation sequence that occurred in our series is not supported by this explanation.…”