BOSTON — A wireless left ventricular endocardial pacing system could be a viable alternative for patients with HF in whom cardiac resynchronization therapy is not beneficial, researchers reported at the Heart Rhythm Society Annual Scientific Sessions.
The SELECT-LV nonrandomized pilot study included 39 patients with HF (mean age, 65 years; 88% men; mean LV ejection fraction, 25.6%; mean baseline QRS, 174 ms) with an indication for CRT but who were unsuited for or did not respond to conventional CRT.
“There are patients who don’t seem to benefit [from CRT], either because there are technical issues with implantation or because … they are nonresponders,” Vivek Y. Reddy, MD, said at a press conference. “Particularly for the nonresponders, there are other data that suggest that instead of pacing from the outside of the heart, pacing directly from within the left ventricle” may be a successful approach.
Vivek Y. Reddy
The patients underwent implantation of an ultrasound-based wireless cardiac stimulation system (WiCS-LV, EBR Systems), which includes a 9-mm leadless pacing electrode implanted at the endocardial mid-lateral LV free wall positioned using a retrograde aortic approach with a steerable 12F sheath. The electrode is activated by a submuscular ultrasonic transmitter synchronized to a right ventricular pacing pulse of a standard pacemaker or implantable cardioverter defibrillator.
“One component is a subcutaneous battery generator that emits ultrasonic pulses to the left ventricle, which hit a pellet that you implant in the left ventricle, and that pellet converts that ultrasound energy into electrical energy to pace the left ventricle,” Reddy said. “It’s a way to perform endocardial [LV] pacing.”
Four patients did not undergo the procedure, three because of an inadequate acoustic window and one because of a decision to withdraw. During the procedure, one patient had ventricular fibrillation and was not implanted.
“An important point is that of the patients enrolled, in 90% it was possible to employ this approach,” Reddy said. “That is, there were proper acoustic windows to perform this kind of pacing.”
At 1 month, mean QRS dropped from 174 ms to 132 ms, Reddy said. “That translated into improvements in [EF] by 7 points [baseline, 27%; 6 months, 33.7%], improvements in remodeling as assessed by ventricular size as well as electrical remodeling based on QRS,” he said. “It also translated to improvements in functional capacity and quality of life.”
Mean NYHA functional class improved from 2.6 at baseline to 1.8 at 6 months, mean end-diastolic volume improved from 228 mL at baseline to 208 mL at 6 months, and mean end-systolic volume improved from 171 mL at baseline to 141 mL at 6 months, according to the researchers.
There were four procedure- or device-related events (11.4%) within 24 hours of the procedure: one groin fistula that was repaired surgically, one groin pseudoaneurysm that did not require treatment, one electrode embolization to the lower leg during catheter/dilator exchange with no negative effect on the patient, and the aforementioned case of ventricular fibrillation. There were no cases of pericardial tamponade.
Between 24 hours and 1 month, there were eight events (22.9%), seven of which were related to the device or procedure, including three infections, Reddy reported. He noted that the patient whose implant was aborted died following prolonged resuscitation 4 days after the procedure.
“We believe all of these safety events are things that are fixable,” Reddy said. “Ultimately, I think what the study showed is that [LV] pacing is possible and appears to confer significant benefits. We need to understand, by studying it in a large number of patients, how safe this can be.” – by Erik Swain
Reddy VY, et al. Abstract LBCT01-05. Presented at: Heart Rhythm Society Annual Scientific Sessions; May 13-16, 2015; Boston.
Disclosure: The study was funded by EBR Systems. Reddy reports receiving consultant fees/honoraria from EBR Systems.