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 (LV), via epicardial or transvenous access, presents specificities both with regard to the anesthetic technique and the skills required to perform them, either via thoracotomy or coronary sinus catheterization. 26-32 Among these aspects, the viability of using coronary sinus tributary veins in individuals with normal or slightly enlarged heart is still unknown, notwithstanding the significant experience already achieved with this means of access in patients with cardiomegaly and an accentuated increase in the left ventricular cavity. In view of this concern regarding the deleterious effects of chronic right ventricular pacing, the hypothesis of the present study was that the use of an active-fixation coronary sinus lead will allow for safe isolated left ventricular pacing for patients with atrioventricular blocks who are indicated for conventional PM implantation. Objectives The objective of the present study was to evaluate the safety, efficacy, and effects of left ventricular pacing, using an active-fixation coronary sinus lead ( Medtronic Attain StarFix® Model 4195 OTW ), 33 in comparison with right ventricular pacing in patients who were indicated for conventional PM implantation and who had normal or slightly altered left ventricular function, with the aim of determining: • The procedural success rate of coronary sinus lead implantation; • The safety and efficacy of left ventricular pacing; • Cardiac synchrony and the occurrence of remodeling and left ventricular dysfunction. Methods Study design This is a randomized controlled clinical trial that compared the use of right ventricular pacing (RV Group) with relation to unifocal left ventricular pacing (LV Group) in patients with bradyarrhythmias. This study was performed in a high complexity cardiology hospital. It received approval from the Institution’s Research Ethics Committee. All participants signed an informed consent form. This study was registered at ClinicalTrials.gov . Study Population Adult subjects whomet the following criteria were considered eligible for the study: (1) Indication of initial implantation of a definitive conventional PM by the transvenous technique; (2) Systolic ventricular function ≥ 0.40; (3) Agreement to participate in the study. Individuals who presented at least one of the following criteria were not included in the study: (1) Impediment of venous access through tributaries of the superior vena cava due to: uncorrected intracardiac defects, absence of venous access, tricuspid valve prosthesis, or need for radiotherapy in the thorax; (2) > 85 years of age; (3) Pregnancy in progress; (4) Contraindication for use of iodinated contrast during the surgical procedure (serum creatine ≥ 3.0 mg/dL). Patients were consecutively selected from those with indication for conventional PM implantation. After the indication of surgical treatment, the individuals who fulfilled the eligibility criteria were submitted to a preoperative evaluation, consisting of medical history, clinical, laboratory and echocardiographic assessment. (Figure 1) Composition of study groups Before the surgical procedure, patients were allocated into two groups in a random distribution list generated by a computer: (1) composed of patients who were submitted to conventional RV lead implantation; (2) LV Group: composed of patients who received implantation of an active-fixation coronary sinus lead in the LV. The random distribution list was generated by the computer program Statistical Analysis System (SAS), with a 2:1 ratio of LV implants. To guarantee a balanced distribution of patients, we opted for block randomization, generating a list with blocks of 10 to allocate patients into the two study groups. Allocation was performed by means of sealed, opaque envelopes, whichwere numbered sequentially. Patient allocation always occurred the night before the surgical procedure, following adequate assessment of the study’s eligibility criteria. The process of preparing and sealing the envelopes was performed by an independent individual who was not involved in any other steps of the study. Blinding of all patients and the investigator responsible for assessing the study results was guaranteed during all phases of the study. Due to the surgical intervention protocol, it was not possible to blind the surgical staff and the team responsible for the PM evaluations and programming. Study interventions The two main interventions performed during this study were conventional right ventricular (RV Group) and left ventricular (LV Group) implantations. The surgical procedure for PM implantation was always performed through the transvenous route, in accordance with our institution’s routine practice. In patients allocated into the RV Group, the Medtronic CapSureFix Novus® 5076-58 lead was preferably implanted in the middle portion of the interventricular septum, always under indirect vision using fluoroscopy. When it was not possible to obtain adequate fixation, stimulation, or sensitivity in the mid-septum position, the ventricular lead was implanted in the apical septum or the outlet septum. In patients allocated into the LV Group, a Medtronic 6228 CTH deflectable catheter was introduced into the coronary sinus, serving as a guide for the introduction of a Medtronic Attain 6227 DEF deflectable guide catheter. When the latter was introduced into the coronary sinus, coronary sinus phlebography was performed in a left anterior oblique position at 30 degrees, with the aid of a Medtronic Attain 6215 balloon catheter and non-ionic iodized contrast medium ( Iodixanol , VisipaqueTM). When the radiological anatomy of the coronary sinus and its tributary veins was defined, a Medtronic Attain StarFix® Model 4195 OTW unipolar lead was introduced 411