Scar nonexcitability using simultaneous pacing for substrate ablation of ventricular tachycardia

What is the best pulse shape for pacing purposes?

Introduction

Cell pacing is a fundamental procedure for generating action potentials (AP) in excitable tissues. Various pulse shapes have been proposed for this purpose, with the aim of either facilitating the achievement of the excitation threshold or minimizing energy delivery to the patient. This study seeks to identify the optimal pulse shape for each of these objectives.

Methods

To determine the most effective pulse forms, we employed a mathematical model simulating nonlinear tissue responses to a range of pulse shapes.

Results

Our results demonstrate that the rectangular pulse is optimal for reaching the excitation threshold, while the Gaussian pulse is superior in minimizing energy delivery. Other pulse shapes examined, including ramp-up, ramp-down, half-sine, and triangular (tent-like), fall between these two in terms of performance.

Discussion

From a clinical perspective, the appropriate pulse shape should be selected based on the specific goal. For minimizing the pulse amplitude required to cross the excitation threshold, the rectangular pulse is recommended. In contrast, if reducing energy delivery to the patient is paramount, the Gaussian pulse is the preferred choice. In other scenarios, a judicious selection can be made based on the outcomes of our model and the clinical requirements.

Updates in Ventricular Tachycardia Ablation

Sudden cardiac death (SCD) due to recurrent ventricular tachycardia is an important clinical sequela in patients with structural heart disease. As a result, ventricular tachycardia (VT) has emerged as a major clinical and public health problem. The mechanism of VT is predominantly mediated by re-entry in the presence of arrhythmogenic substrate (scar), though focal mechanisms are also important. Catheter ablation for VT, when compared to standard medical therapy, has been shown to improve VT-free survival and burden of device therapies. Approaches to VT ablation are dependent on the underlying disease process, broadly classified into idiopathic (no structural heart disease) or structural heart disease (ischemic or non-ischemic heart disease). This update aims to review recent advances made for the treatment of VT ablation, with respect to current clinical trials, peri-procedure risk assessments, pre-procedural cardiac imaging, electro-anatomic mapping and advances in catheter and non-catheter based ablation techniques.