The Emerging Role of Cardiac Conduction System Pacing as a Treatment for Heart Failure

Abstract

Purpose of Review The aim of cardiac resynchronization therapy (CRT) is to improve cardiac function by delivering more physiological cardiac activation to patients with heart failure and conduction abnormalities. Biventricular pacing (BVP) is the most commonly used method for delivering CRT; it has been shown in large randomized controlled trials to significantly improve morbidity and mortality in patients with heart failure. However, BVP delivers only modest reductions in ventricular activation time and is only beneficial in patients with prolonged QRS duration. In this review, we explore conduction system pacing as a method for delivering more effective ventricular resynchronization and to extend pacing therapy for heart failure to patients without left bundle branch block (LBBB). Recent Findings The aim of conduction system pacing is to provide physiological ventricular activation by directly stimulating the conduction system. Current modalities include His bundle and left conduction system pacing. His bundle pacing is the most established method; it has the potential to correct left bundle branch block and deliver more effective ventricular resynchronization than BVP. This translates into greater acute haemodynamic improvements and observational data suggests that His-CRT results in improvements in cardiac function and symptoms. AV-optimized His bundle pacing is being investigated in patients with heart failure and long PR interval without LBBB, to see if this improves exercise capacity. More recently, a technique for pacing the left bundle branch has been developed. Early studies show potential advantages including low and stable capture thresholds. Summary Conduction system pacing can deliver more effective ventricular resynchronization than BVP, which has the potential to deliver greater improvements in cardiac function. It may also provide the opportunity to extend pacing therapy for heart failure to patients who do not have LBBB. Further data is required from randomized trials to assess these promising pacing techniques.

Conduction System Disorders Associated with Valvular Heart Disease and Interventions

“…poor improvement in NYHA class, QRS duration, or echocardiographic parameters) [64]. Furthermore, while conventional CRT does improve QRS duration, it does not return it to a range seen in patients with intact conduction tissue, suggesting better therapeutic benefits with shorter QRS [65]. Whether CSP can be used as an alternative to, or as rescue therapy for patients with an indication for CRT remains to be seen.…”

Overview of Current Strategies Aiming at Improving Response to Cardiac Resynchronization Therapy

“…Experiments have shown that CSP is an important alternative in solving the residual dyssynchrony problem created by conventional BVP between the 2 ventricles and in the interventricular septum ( Table 2 ). 23 In addition, considering that IVCD is not limited to the distal area and may include the proximal conduction system in patients with poor conventional CRT response, it is thought that CSP can be used as the first choice in appropriate patient groups 24 ( Figures 2 and 3 ).…”

An Appreciation of Anatomy in the Molecular World

“…It is clearly so that more accurate knowledge is better, but at the same time it is certainly also true that the society of anatomical sciences has an epigenetic state predisposing it to spending many words on fine details. The cardiac conduction system, however, exemplifies a case where painstaking and tedious anatomical work led to insights of great clinical importance such as which parts of the heart can be operated on in corrective surgery [ 117 , 118 , 119 ] and which parts are most suitable for artificial pacing [ 120 , 121 ].…”