OPTImizing Lead Placement in Patients Requiring Pacemaker After Cardiac Surgery

Atrioventricular Block, Cardiac Surgery

Conduction system pacing, Atrioventricular block, After cardiac surgery, Left bundle branch area pacing

Conventional right ventricular pacing has been associated with ventricular dyssynchrony and an increased risk of pacing-induced cardiomyopathy, which may lead to worse clinical outcomes. To lessen the burden of pacing-induced cardiomyopathy, the adoption of conduction system pacing has increased in recent years. In patients with normal cardiac function, measured as left ventricular ejection fraction, the superiority of conduction system pacing is less clear. As a result, both pacing strategies remain in widespread clinical use. Patients undergoing cardiac surgery represent a vulnerable cohort for pacing-induced cardiomyopathy, given their established structural heart disease, and postoperative atrioventricular block remains a common occurrence in these patients. This multicenter randomized trial aims to evaluate the use of conduction system pacing, in the form of left bundle branch area pacing, versus conventional pacing in patients with normal left ventricular ejection fraction after cardiac surgery.

A high percentage of ventricular pacing increases the risk of pacing-induced cardiomyopathy. Pacing-induced cardiomyopathy is a syndrome defined by left ventricular dysfunction secondary to chronic right ventricular pacing, resulting in impaired outcomes. Pacing-induced cardiomyopathy is estimated to affect approximately 10-20% of patients with a high proportion of right ventricular pacing (\>20%), a population that mainly consists of patients with atrioventricular block (AVB). The abnormal activation leads to prolonged electrical and mechanical activation, which results in ventricular dyssynchrony. Other important risk factors for pacing-induced cardiomyopathy include structural heart disease and reduced ejection fraction, male sex and wide, paced QRS. Clinical practice guidelines support pacemaker implantation following cardiac surgery only for severe and non-transient bradyarrhythmias, as pacemaker implantation increases the risk of severe infections and device-related long-term complications. Evidence suggests that a substantial proportion of patients who receive a pacemaker following cardiac surgery have limited need for pacing at long-term follow-up. Thus, the risk/benefit ratio for patients following cardiac surgery differs from that of the general population, while these patients also form a vulnerable population at high risk for pacing-induced cardiomyopathy. Over the last decade, a conduction system pacing strategy called left bundle branch area pacing (LBBAP) has been developed. In LBBAP, the pacemaker lead is inserted deep into the interventricular septum from the right ventricle to the left ventricular endocardium, targeting the left bundle and its resulting fascicles. As the current understanding of the development of pacing-induced cardiomyopathy suggests that the electrical dyssynchrony introduced by right ventricular pacing plays a crucial role, our hypothesis is that its incidence could be reduced by the favorable electrical activation achieved with LBBAP. There are ongoing randomized controlled trials of conduction system pacing in the general population; however, none are investigating cardiac surgery patients. These patients differ substantially from the general population in age, expected long-term survival, and cardiovascular health. This increases their risk of pacing-induced cardiomyopathy and could influence the feasibility of conduction system pacing due to their otherwise impaired cardiovascular health. At the same time, their long-term pacing dependence could differ from that of the general population. Therefore, the aim of the present multicenter randomized controlled trial is to evaluate the long-term outcomes of LBBAP versus right ventricular pacing after cardiac surgery in patients with normal left ventricular ejection fraction. A secondary aim is to assess the feasibility of LBBAP after cardiac surgery with regard to implantation success and long-term electrical parameters. The results of this trial are anticipated to provide clinically meaningful evidence to guide pacing strategy selection in this patient cohort.

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