Cardiac resynchronisation therapy (CRT) may be achieved using a direct wireless endocardial left ventricular pacing system, a new study has shown. Results from the prospective, non-randomised, multicentre SELECT-LV trial were presented at the Heart Rhythm Society (HRS) 36th Annual scientific Sessions (13-16 May, Boston, USA) and demonstrated promising efficacy and safety data.
Vivek Y Reddy (Mount Sinai School of Medicine, New York, USA), presenter and lead author of the study told delegates: “The data show that in terms of efficacy it is certainly promising. The device was able to synchronise to the right ventricular pulse from a variety of types of devices and co-implants. It allowed synchronous left ventricular stimulation providing significant reductions in QRS duration, evidence of structural as well as electrical remodelling, and improvements in ejection fraction. In those patients in whom it was successful there were significant improvements in clinical outcome.”
The left ventricular pacing system (Wise LV, EBR Systems) is leadless. It has a subcutaneous generator that transmits ultrasound energy to the left ventricle. A pellet implanted in the left ventricle transduces ultrasound energy to the pacing output. Reddy said: “Beyond surgical approaches there are data that suggest that endocardial, as opposed to epicardial pacing, does have some potential benefits. You are not subject to the vagaries of the coronary sinus anatomy.”
He continued, “The co-implant included both conventional high energy as well as pacemaker devices in the right ventricle from a variety of different manufacturers. The subcutaneous battery and transmitter are implanted in one procedure and then the following day the patient undergoes a second procedure, a transvascular procedure, to place the endocardial pacing pellet.”
The patients selected for this study had heart failure with baseline QRS of 174ms. They met the criteria for CRT but had failed conventional resynchronisation therapy, either because of technical problems, such as coronary sinus lead issues, or because they were non-responders to CRT. Reddy said: “Left ventricular endocardial pacing was then proposed as a potential solution.”
The primary endpoint was safety in the 24-hour perioperative period, and safety and pacing performance at one month postoperation. Secondary endpoints were safety, performance and efficacy at six months.
A total of 39 patients were enrolled, but four did not undergo implantation-one patient withdrew and a further three were not implanted due to the lack of an acoustic window. Of the remaining 34 patients, all were followed-up at one month, and 26 were followed-up at six months. They will continue to have a device check every three months and annual assessments for five years. Participants who were not already taking anticoagulants were treated with three months dual antiplatelet therapy.
An initial evaluation of the first generation of the device (WISE-CRT study) published by Angelo Auricchio (Division of Cardiology, Fondazione Cardiocentro Ticino, Lugano, Switzerland) and colleagues in Europace in 2014, had to be terminated early due to three pericardial effusions that occurred during electrode implantation. However, this initial study showed early feasibility with the leadless technology.
In the current study, implantation was successful in all but one of the 34 patients. In that case the electrode was not implanted because of intraprocedural ventricular fibrillation. This was one of four adverse events that occurred in four patients in the 24-hour perioperative period. Between 24-hours postoperatively and one month following the procedure, eight adverse events occurred in eight patients (six procedure related, one procedure and device related and one unrelated to either). “No patient suffered a pericardial tamponade,” Reddy noted.
However, he admitted: “This did come with a cost. There were some safety issues. One of the safety issues that we were very concerned about was the perforation during implantation of the pellet in the left ventricle. That did not happen so that is good news.
“What of the bad news? There are other complications that did occur. There were some related to vascular complications during vascular access that we are sort of less worried about. We have to see that in a large number of patients. We believe all of these safety events are things that are fixable.”
Reddy told delegates: “This is a non-randomised study so you have to take this with a grain of salt, but having said that, the QRS narrowed significantly from a baseline in the 170’s by 40ms. That translated to improvements in ejection fraction by seven points, improvements in remodelling as assessed by ventricular size, as well as electrical remodelling in terms of remodelling of the baseline QRS, and finally that also translated to improvements in functional capacity in these patients.”
But he conceded: “There were some issues with device performance but these are technical issues that seem to have been resolved.” Three patients suffered from battery depletion.
Reddy concluded: “To me the most exciting aspect of this is the idea that we may be able to improve our efficacy of CRT. There is a fair amount of data suggesting that we can do much better. It does actually seem to have implications in terms of even endpoints like mortality. So I think it is a very exciting technology, a very exciting approach. It is still early and we need large data.
“Ultimately I think what the study showed is that left ventricular pacing is possible, it appears to convey significant benefits and we need to understand if we do this in a large number of patients how safe this can be.”