1.     Introduction:
Conventional pacing from the right ventricle (RV) remains the most common site for cardiac pacing. But, RV pacing results in altered electromechanical activation of the ventricles which can have detrimental effects on myocardial perfusion, metabolism, and energy efficiency (1). This, in turn, can lead to progressive adverse remodelling at cellular and chamber levels with resultant deterioration in ventricular function (2). The term pacing-induced cardiomyopathy (PICM) was coined to identify the deleterious effects of RV pacing on left ventricular (LV) function and the resultant clinical syndrome of heart failure. Physiological pacing, with its advantage of minimizing or eliminating electromechanical dyssynchrony, is emerging as an attractive alternative (3). However, because of the steeper learning curve and paucity of long-term safety data, it is too early for it to completely replace conventional pacing (4). So, for the foreseeable future, RV pacing will remain the most common therapy for pacing indications.
Only a subset of patients with RV pacing develop PICM. Depending on the definition used, the incidence of PICM varies from 9 to 19.5% (5–8). The list of risk factors that predispose to PICM is not exhaustive and continues to evolve. One common factor across most studies is the burden of RV pacing (7,9). South Asians have a high cardiovascular risk and younger age of hospitalization for heart failure (10). It is possible that ethnicity and demographic factors may play a role. The aim of this study was to determine the incidence and identify predictors of PICM in the South Asian population. We also sought to evaluate if these risk factors added up.
2. Methods
2.1 Study Population
Consecutive adult patients who underwent pacemaker (PM) in our institution from 2012 to 2018 were identified for analysis after institutional review board approval. Exclusion criteria were: (i) unavailability of echocardiogram done within 6 months before implantation, (ii) Left Ventricular ejection fraction (LVEF) < 50.0%, (iii) significant valvular abnormalities (more than mild stenosis or regurgitation), (iv) complex congenital heart disease, (v) previous myocardial infarction or significant coronary artery disease, and (vi) implantable cardioverter-defibrillator, cardiac resynchronization therapy device, or single chamber atrial pacemaker implantation.