Left Ventricular Endocardial Pacing for Heart Failure
What is the feasibility and safety of left ventricular endocardial pacing (LVEP) using a market-released pacing lead implanted via a single pectoral access by a novel atrial transseptal lead delivery system?
ALSYNC (ALternate Site Cardiac ResYNChronization) was a prospective clinical investigation with a minimum of 12-month follow-up in 18 centers of cardiac resynchronization therapy (CRT)-indicated patients, who had failed or were unsuitable for conventional CRT. Patients required warfarin therapy post-implant. The primary study objective was safety at 6-month follow-up, which was defined as freedom from complications related to the lead delivery system, implant procedure, or the lead ≥70%.
The ALSYNC study enrolled 138 patients. The LVEP lead implant success rate was 89.4%. Freedom from complications meeting the definition of the primary endpoint was 82.2% at 6 months. In the study, 14 transient ischemic attacks (nine patients, 6.8%), five non-disabling strokes (five patients, 3.8%), and 23 deaths (17.4%) were observed. No death was from a primary endpoint complication. At 6 months, the New York Heart Association class improved in 59% of patients, and 55% had LV end-systolic volume reduction of ≥15%. Those patients enrolled after CRT nonresponse showed similar improvement with LVEP.
The ALSYNC study demonstrates clinical feasibility, and provides an early indication of possible benefit and risk of LV endocardial pacing.
In addition to a large nonresponder rate, conventional CRT suffers from the limitations imposed by coronary sinus venous anatomy and the diaphragmatic nerve stimulation. This study describes preliminary results of placement of an LV endocardial pacing lead with an investigational lead delivery system via atrial transseptal approach. The pacing lead used was a Medtronic Model 3830 SelectSecure, which is currently approved for right atrial and right ventricular pacing. Endocardial LV lead placement offers the potential for the most optimal placement of the electrode based on physiological factors. There are also some data suggesting superior hemodynamic response with LV endocardial versus epicardial stimulation. A major concern is elevated risk of stroke. Despite anticoagulation with warfarin, the risk of stroke was 2.6 events per 100 patient-years and risk of transient ischemic attack was 7.4 events per 100 patient-years. Most of the thromboembolic events occurred while international normalized ratio (INR) was <2.5. The ideal INR range for stroke prophylaxis in patients with LV endocardial leads is not known, and this matter deserves study. Future research should assess acute hemodynamic improvements and clinical outcomes in patients with endocardial versus epicardial leads in a randomized manner.
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