RESUMO
BACKGROUND: Data concerning the effect of chronic right ventricular pacing in patients with normal left ventricular ejection fraction (LVEF%) are contradictory. The aim of this study is to evaluate the prevalence of pacing-induced cardiomyopathy (PICM) at midterm follow-up after permanent pacemaker implantation (PPM). METHODS: A series of 170 patients were submitted to PPM within our facility. Inclusion criteria were the absence of structural heart disease and a preserved LVEF% (> 45%) at the time of PPM. A midterm clinical and echocardiographic follow-up was performed, and data were collected and analyzed retrospectively. PICM was defined as follow-up LVEF ≤ 45%, dyskinesia during RV pacing, and the absence of other known causes of cardiomyopathy. RESULTS: At a median echocardiographic follow-up of 24.5 months (IQR 10.0-43.0 months), the overall mean LVEF% decreased from a preimplantation value of 66.7% (± 8.6%) to 63.2% (± 10.6%) (p < 0.0001). PICM occurred in 11 patients (6.5%). Patients developing PICM had a significantly lower preimplantation LVEF% (58.4 ± 8.0% vs. 67.3 ± 8.4%; p = 0.005), a trend for higher right ventricular pacing time rate (0.7 ± 0.3 vs. 0.5 ± 0.4; p = 0.1), a significantly lower rate of PPM indication for sick sinus syndrome (SSS) (18.2% vs. 61.0%; p = 0.009), and significantly higher rate of second-grade cardiac conduction block (36.4% vs. 11.3%; p = 0.03). At multivariate logistic regression, only preimplantation LVEF% (OR = 0.88; CI 0.80-0.96; p = 0.006) and the presence of SSS (OR = 0.1; CI 0.03-0.9; p = 0.04) were independently related (inverse relationship) to follow-up PICM. CONCLUSIONS: In this selected PPM patient cohort with preserved LVEF%, the rate of PICM at midterm follow-up is relatively low, but its occurrence seems to be related to baseline LVEF% and PPM indication category.