ABC | Volume 112, Nº4, April 2019

Original Article Efficacy, Safety, and Performance of Isolated Left vs. Right Ventricular Pacing in Patients with Bradyarrhythmias: A Randomized Controlled Trial Elizabeth Sartori Crevelari, Katia Regina da Silva , Caio Marcos de Moraes Albertini, Marcelo Luiz Campos Vieira, Martino Martinelli Filho, Roberto Costa Instituto do Coração (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP), São Paulo, SP – Brazil Mailing Address: Roberto Costa • Av. Dr. Enéas de Carvalho Aguiar, 44, Postal Code 05403-900, Cerqueira César, São Paulo, SP – Brazil E-mail: rcosta@incor.usp.br Manuscript received May 11, 2018, revised mansucript August 03, 2018, accepted September 05, 2018 DOI: 10.5935/abc.20180275 Abstract Background: Considering the potential deleterious effects of right ventricular (RV) pacing, the hypothesis of this study is that isolated left ventricular (LV) pacing through the coronary sinus is safe andmay provide better clinical and echocardiographic benefits to patients with bradyarrhythmias and normal ventricular function requiring heart rate correction alone. Objective: To assess the safety, efficacy, and effects of LV pacing using an active-fixation coronary sinus lead in comparison with RV pacing, in patients eligible for conventional pacemaker (PM) implantation. Methods: Randomized, controlled, and single-blinded clinical trial in adult patients submitted to PM implantation due to bradyarrhythmias and systolic ventricular function ≥ 0.40. Randomization (RV vs. LV) occurred before PM implantation. Themainresultsofthestudywereproceduralsuccess,safety,andefficacy.Secondaryresultswereclinicalandechocardiographic changes. Chi-squared test, Fisher’s exact test and Student’s t-test were used, considering a significance level of 5%. Results: From June 2012 to January 2014, 91 patients were included, 36 in the RV Group and 55 in the LV Group. Baseline characteristics of patients in both groups were similar. PM implantation was performed successfully and without any complications in all patients in the RV group. Of the 55 patients initially allocated into the LV group, active‑fixation coronary sinus lead implantation was not possible in 20 (36.4%) patients. The most frequent complication was phrenic nerve stimulation, detected in 9 (25.7%) patients in the LV group. During the follow-up period, there were no hospitalizations due to heart failure. Reductions of more than 10% in left ventricular ejection fraction were observed in 23.5% of patients in the RV group and 20.6% of those in the LV group (p = 0.767). Tissue Doppler analysis showed that 91.2% of subjects in the RV group and 68.8% of those in the LV group had interventricular dyssynchrony (p = 0.022). Conclusion: The procedural success rate of LV implant was low, and the safety of the procedure was influenced mainly by the high rate of phrenic nerve stimulation in the postoperative period. (Arq Bras Cardiol. 2019; 112(4):410-421) Keywords: Cardiac Pacing, Artificial; Bradycardia; Arrhythmias, Cardiac; Pacemaker, Artificial; Ventricular remodeling. Introduction Artificial cardiac pacing is the only treatment for acquired atrioventricular blocks. 1-3 Conventional pacemakers (PM), which stimulate the right ventricle (RV), via unicameral or atrioventricular pacing, have been the most widely used devices to treat these bradyarrhythmias. 1-4 Owing to its proven effectiveness in reducing symptoms caused by low cerebral and systemic blood flow, as well as its increased survival rate, this clinical indication represents 55.1% and 83.4% of all implants performed in the United States of America and Brazil, respectively. 5,6 Nevertheless, deleterious effects of chronic right ventricular pacing have been described. Examples include proarrhythmic mechanisms, intra- or interventricular electromechanical dyssynchrony, and ventricular remodeling, which may lead to heart failure refractory to drug treatment. 7-14 Changing the mode of pacing from RV to biventricular has been reported to reverse these events. 15-20 Isolated atrial synchronous left ventricular pacing has been used for the correction of cardiac dyssynchrony in patients with severe left ventricular dysfunction and left bundle branch block, with results similar to those obtained by atriobiventricular pacing. 21-25 There is, however, no evidence to date that the use of isolated left ventricular pacing, in comparison with right ventricular pacing, may reduce the rate of ventricular remodeling in patients with acquired atrioventricular blocks, regardless of the presence or absence of previous left ventricular dysfunction. Notwithstanding the possible clinical-functional benefits that may be expected from the use of left ventricular pacing, in comparison with right ventricular pacing, there are other factors that may influence this comparison, especially those related to the operating technique and its complications. The technique of implanting PM with endocardial RV pacing is well established and its results and complications have long been known. On the other hand, implants in the left ventricle 410