SAN FRANCISCO – Wireless endocardial left ventricular pacing provides an alternative approach to cardiac resynchronization pacing in heart failure patients, according to preliminary results from an ongoing multicenter trial.
At the annual scientific sessions of the Heart Rhythm Society, Dr. Vivek Y. Reddy presented preliminary results from 19 patients enrolled in the SELECT-LV (Safety and Performance of Electrodes Implanted in the Left Ventricle) study. The purpose of the open-label trial is to evaluate the safety and feasibility of leadless, ultrasound-based pacing using a wireless cardiac stimulation system (WiCS-LV) developed by EBR Systems.
Dr. Vivek Y. Reddy
"The idea is to use an existing standard ICD [implantable cardioverter defibrillator] or pacemaker and place this device, which has a transmitter as well as a battery, in a subcutaneous location, and then place a receiver-electrode ‘pellet’ on the left ventricle endocardial wall," explained Dr. Reddy, professor of medicine at Mount Sinai Hospital, New York. "The idea is that the transmitter emits ultrasound impulses detected by the pellet. In turn, the pellet transduces the ultrasound impulse into an electrical pacing pulse to stimulate the heart."
The battery, which is 42 cc in size, is placed subcutaneously in the subaxillary region. The transmitter, which is 13 cc in size, is placed between the ribs "in an optimal position so that there is an echo window which allows you to see the left ventricle," Dr. Reddy said. "Then, on the same day or the next day, the pellet (which is 0.05 cc in size) is placed on the left ventricle via a transfemoral catheter approach."
The SELECT-LV investigators intend to enroll 40 patients at seven centers to evaluate the performance and efficacy of the approach. The primary endpoints are device- and procedure-related complications perioperatively and at 1 month, and biventricular pacing capture on 12-lead ECG at 1 month. Secondary endpoints are device-related or major complications up to 6 months and LV pacing capture at 1, 2, and 6 months, as well as biventricular capture at 6 months on 12-lead ECG. Preliminary efficacy is measured by a composite score of all-cause mortality, heart failure hospitalization, New York Heart Association (NYHA) class, and patient global assessment at 6 months, as well as LV end systolic/diastolic volumes and LV ejection fraction at 6 months.
Patients are eligible for the trial if they have a failed implant of a coronary sinus lead or a chronic issue with their CS lead; if they have no clinical status improvement in 6 months of cardiac resynchronization pacing (CRT); or if they have a previously implanted pacemaker or ICD with a new indication for biventricular pacing but are at risk for a CRT upgrade due to venous occlusion or other factors.
Of the 19 patients who have been implanted to date, 16 (84%) were male, their mean age was 68 years, and they were relatively evenly split between ischemic and nonischemic substrates. Nearly half (47%) had a failed CS lead implant and their mean LV ejection fraction at baseline was 26%.
Primary and secondary endpoint data were available for 15 of the 19 patients, and 6-month data were available for 8 patients. At 1 month, all 15 patients demonstrated Bi-V pacing on 12-lead ECG. The QRS narrowed by 46 ms at 1 month and by 23 ms at 6 months. NYHA class also significantly improved between baseline and 6 months (from II to I; decline of 0.63 points). All patients experienced improvements on their clinical composite score.
No periprocedural adverse events and no device-related serious adverse events occurred within the first month of implant, but 10 serious adverse events occurred in six patients within the first 6 months, including one patient with a hematoma at the transmitter pocket and one patient who had a stroke 3 days after the procedure. "This is a patient who had atrial fibrillation," Dr. Reddy noted. "At the time of the procedure the [warfarin] was stopped. The patient was implanted, did well, but the [warfarin] hadn’t been restarted at the 3-day time point and the patient suffered a stroke. After this experience, we altered the protocol so that patients on anticoagulation for any indication need to continue active coagulation [with no interruption]. We’ll see how that fares."
The study was funded by EBR Systems. Dr. Reddy is a consultant to the company.
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