ABC | Volume 112, Nº4, April 2019

Original Article Philbois et al Isolated left ventricular pacing in bradyarrhythmias Arq Bras Cardiol. 2019; 112(4):410-421 Figure 1 – Diagram showing the main phases of the study. LV: left ventricle; RV: right ventricle. Patients eligible for the study Preoperative assessment Clinical assessment Laboratory assessment Echocardiogram Randomization (2:1) RV lead implant LV lead implant Clinical follow-up Clinical assessment: 10-15 days, 1, 6, 12, 28, and 24 months after procedure Pacemaker assessment: 1, 6, 12, 28, and 24 months after procedure Echocardiogram: 6 and 24 months after procedure Primary Outcomes • Success of surgical procedure • Procedure safety • Procedure efficacy Secondary outcomes • Clinical outcomes – Heart failure and hospitalization • Echocardiographic outcomes – Remodeling and cardiac synchrony Recruiting Group composition Follow-up Results into one of the veins of the lateral or posterolateral wall (Figure 2). When it was not possible to use the veins of the lateral or posterolateral wall due to inadequate stimulation or sensitivity, phrenic stimulation, or lack of lead stability, the diagonal vein was used; placement in the anterior or posterior interventricular sulci was not permitted. Exclusion of patients when implant through the coronary sinus was not feasible This study excluded all patients allocated into the LV Group in whom it was not possible to implant the lead in coronary veins. After the surgical team determined that implantation in the LV was not possible, the Medtronic Attain StarFix® Model 4195 OTW lead was removed and a new Medtronic CapSureFix Novus® 5076-58 was implanted in the RV. After the procedure, the patients were excluded from the study. Study outcomes This study’s primary outcomes include: (1) The proposed procedure was successful, defined by coronary sinus catheterization with lead implant in the posterior or lateral LV wall; (2) Procedure safety, defined by the absence of surgical complications during the study period (24 months); (3) Procedure efficacy, defined by the maintenance of chronic stimulation thresholds at < 2.5 V with 0.4 ms during the study period (24 months). Secondary outcomes were clinical evolutions and echocardiographic changes, such as: (1) Alteration of left ventricular function, defined by the reduction of at least 10% of the ejection fraction in the examination performed at the end of the study; (2) LV positive remodeling, defined by a 15% increase in the systolic diameter of the cardiac chamber. (3) Ventricular dyssynchrony, defined by the presence of intra‑or interventricular electromechanical delay in the examination performed at the end of the study. Sample size calculation The calculation of this study’s sample size was based on the average occurrence rate of the primary outcomes according to the description in the literature, considering an alpha error of 5% and a statistical power of 80%. With respect to operative outcomes, we found procedural success, efficacy, and safety rates in 99% and 91% of the patients who underwent lead implantation in the RV and the LV, respectively. 1,2,28 The sample size required for finding an equivalence between the two techniques was estimated at 188 patients in the LV Group and 94 in the RV Group, with a total of 282 cases. 412