Cardiomyopathy Induced by Artificial Cardiac Pacing: To Whom, When, Why, and How? Insights on Heart Failure Development

ABSTRACT Coordinated and harmonic (synchronous) ventricular electrical activation is essential for better left ventricular systolic function. Intraventricular conduction abnormalities, such as left bundle branch block due to artificial cardiac pacing, lead to electromechanical “dyssynchronopathy” with deleterious structural and clinical consequences. The aim of this review was to describe and improve the understanding of all the processes connecting the several mechanisms involved in the development of artificially induced ventricular dyssynchrony by cardiac pacing, most known as pacing-induced cardiomyopathy (PiCM). The chronic effect of abnormal impulse conduction and nonphysiological ectopic activation by artificial cardiac pacing is suspected to affect metabolism and myocardial perfusion, triggering regional differences in the activation/contraction processes that cause electrical and structural remodeling due to damage, inflammation, and fibrosis of the cardiac tissue. The effect of artificial cardiac pacing on ventricular function and structure can be multifactorial, and biological factors underlying PiCM could affect the time and probability of developing the condition. PiCM has not been included in the traditional classification of cardiomyopathies, which can hinder detection. This article reviews the available evidence for pacing-induced cardiovascular disease, the current understanding of its pathophysiology, and reinforces the adverse effects of right ventricular pacing, especially right ventricular pacing burden (commonly measured in percentage) and its repercussion on ventricular contraction (reflected by the impact on left ventricular systolic function). These effects might be the main defining criteria and determining mechanisms of the pathophysiology and the clinical repercussion seen on patients.摘要 协调一致的心室电活动对于维持良好的左心室收缩功能（left ventricular systolic function）至关重要。心室内传导异常（intraventricular conduction abnormalities），如人工心脏起搏（artificial cardiac pacing）所致的左束支传导阻滞（left bundle branch block），可引发电机械不同步综合征（electromechanical dyssynchronopathy），并带来有害的结构与临床不良结局。本综述旨在阐明并加深人们对心脏起搏所致人工诱导心室不同步发病机制相关全部过程的理解，此类病症即通常所称的起搏诱导型心肌病（pacing-induced cardiomyopathy, PiCM）。人工心脏起搏引发的异常冲动传导与非生理性异位兴奋所产生的慢性效应，可能会影响心肌代谢与灌注，进而导致激活-收缩过程出现区域差异，最终因心肌组织损伤、炎症及纤维化引发电重构与结构重构。人工心脏起搏对心室功能与结构的影响可能是多因素的，而起搏诱导型心肌病的潜在生物学因素，可能会影响该病的发病时间与发病概率。起搏诱导型心肌病尚未被纳入传统心肌病分类体系，这一情况可能会阻碍该病的早期检出。本文综述了起搏诱导型心血管疾病的现有研究证据，以及当前对其病理生理学（pathophysiology）的认知，并着重强调了右心室起搏（right ventricular pacing）的不良影响，尤其是右心室起搏负荷（right ventricular pacing burden，通常以百分比量化）及其对心室收缩功能的影响（具体体现为对左心室收缩功能的作用）。此类效应或可成为该病病理生理学特征与患者临床结局的核心判定标准及关键致病机制。