Evaluation of the Novel Automated Anti-Tachycardia Pacing Algorithm Successfully Terminating Sustained Monomorphic Ventricular Tachycardia in an Electrophysiology Study

Comparison of novel intrinsic versus conventional antitachycardia pacing for ventricular tachycardia among implantable cardioverter-defibrillator recipients

INTRODUCTION

Intrinsic antitachycardia pacing (iATP) is a novel automated antitachycardia pacing (ATP) that provides individual treatment to terminate ventricular tachycardia (VT). However, the clinical efficacy of iATP in comparison with conventional ATP is unknown. We aim to compare the termination rate of VT between iATP and conventional ATP in patients with implantable cardioverter-defibrillators using a unique setting of different sequential orders of both ATP algorisms.

METHODS

Patients with the iATP algorithm were assigned to iATP-first and conventional ATP-first groups sequentially. In the iATP-first group, a maximum of seven iATP sequences were delivered, followed by conventional burst and ramp pacing. In contrast, in the conventional ATP-first group, two bursts and ramp pacing were initially programmed, followed by iATP sequences. We compared the success rates of VT termination in the first and secondary programmed ATP zones between the two groups.

RESULTS

Fifty-eight and 56 patients were enrolled in the iATP-first and conventional ATP-first groups, and 67 and 44 VTs were analyzed in each group, respectively. At the first single ATP therapy, success rates were 64% and 70% in the iATP and conventional groups, respectively. At the end of the first iATP treatment zone, the success rate increased from 64% to 85%. Moreover, secondary iATP therapy following the failure of conventional ATPs increased the success rate from 80% to 93%. There was a significant benefit of alternative iATP for VT termination compared to secondary conventional ATP (100% vs. 33%, p = .028).

CONCLUSIONS

iATP may be beneficial as a secondary therapy after failure of conventional ATP to terminate VT.

Case report: successful termination of ventricular tachycardia by intrinsic anti-tachycardia pacing beyond conventional anti-tachycardia pacing

Background

Anti-tachycardia pacing (ATP) is a pain-free alternative to defibrillation shock for monomorphic ventricular tachycardia (VT). Intrinsic ATP (iATP) is a novel algorithm of auto-programmed ATP. However, the advantage of iATP over conventional ATP in clinical cases is still unknown.

Case summary

A 49-year-old man with no significant past medical history was transferred to our institution with sudden-onset fatigue from working on a farm. A 12-lead electrocardiogram showed monomorphic sustained wide QRS tachycardia with a right bundle branch block pattern and superior axis deviation with a cycle length (CL) of 300 ms. Sustained monomorphic VT originating from the left ventricle due to underlying vasospastic angina was diagnosed by contrast-enhanced cardiac magnetic resonance imaging, coronary angiography, and the acetylcholine stress test, and implantable cardioverter defibrillator implantation was performed. Nine months later, a clinical VT episode with a CL of 300 ms was observed, which could not be terminated by three sequences of conventional burst pacing. Ventricular tachycardia was finally terminated by a third iATP sequence without any acceleration.

Discussion

Although standard burst pacing by conventional ATP reached the VT circuit, it failed to terminate the VT. Using the post-pacing interval, iATP automatically calculated the appropriate number of S1 pulses required to reach the VT circuit. In iATP, the S2 pulses are delivered with a calculated coupling interval based on the estimated effective refractory period during tachycardia. In this case, iATP might have led to less aggressive S1 stimulation, followed by aggressive S2 stimulation, which probably helped terminate the VT without any acceleration.