Totally leadless cardiac resynchronization therapy (CRT) combining the Micra transcatheter pacing system and a WiSE-CRT system was feasible and associated with significant acute QRS reduction in a small, nonrandomized, retrospective study.
Six months after WiSE-CRT implantation, heart failure patients showed a significant increase in left ventricular ejection fraction (LVEF), from 28.43% to 39.71% (P = .018), but there was no difference in QRS duration or New York Heart Association functional status and no evidence of left ventricular reverse remodeling.
"The take-home from this study is the possibility of performing CRT pacing (biventricular pacing) with leadless pacing — a leadless pacemaker in the right ventricle and a leadless pacemaker in the left ventricle. This is the future of cardiac pacing," said Pascal Defaye, MD, from Grenoble University Hospital, Grenoble Cedex, France.
Conventional CRT with a lead placed in the coronary sinus is the first-line choice for patients with symptomatic heart failure with persistent reduced LVEF and conduction disturbances, but 8% to 10% of CRT-eligible patients are unable to undergo the procedure because of anatomic constraints.
The WiSE-CRT system is an investigational device that uses wireless technology to deliver pacing stimulation directly to the inside of the left ventricle of the heart. With this system, a passive electrode is implanted in the LV endocardial wall; this converts ultrasound energy delivered by a subcutaneous system into an electrical impulse.
"The WiSE-CRT system provides the only means to upgrade the large population of Micra patients to CRT capability without replacing the Micra," write Defaye and colleagues, including first author Adrien Carabelli, MD, also from Grenoble University Hospital.
The small trial was published online on December 13 in EP Europace.
The Micra Transcatheter Pacing System was the first leadless pacemaker approved in Europe (in 2015) and in the United States (in 2016). In January 2020, the Micra's approval was extended to patients with complete AV block, who would normally receive a conventional dual-chamber pacemaker.
This first European experience with completely leadless CRT included eight patients (mean age, 76 years; seven men, one woman) from six European centers.
Implantation of the WiSE-CRT system was successful for all eight patients. The device was able to detect the Micra pacing output and be trained to deliver synchronous LV endocardial pacing. Biventricular endocardial pacing was confirmed in all patients following the procedure.
QRS duration fell from 204.37 ms before implantation to 137.50 ms after implantation (change, -66.88 ms; P = .012).
In an email exchange with theheart.org | Medscape Cardiology, Defaye suggested that the study indicates that pacing the left ventricle endocardially "is more efficient than through the coronary sinus (epicardially)."
One patient died from acute heart failure 4 months after implantation. Among the seven patients who reached the 6-month follow-up, 4 of 8 showed an absolute improvement in LVEF of 10% of more.
All participants were in permanent atrial fibrillation, and most had a preexisting Micra leadless pacemaker. For three patients, the indication for WiSE-CRT implantation was infection. The other five patients needed to upgrade to the single-chamber Micra for biventricular pacing because of heart failure.
Asked about the possibility of one day having a single leadless CRT device, Defaye said, "We could imagine a very small leadless device in the right ventricle, identical to the left ventricle and the energy transmitted with ultrasound synchronously to the right and left ventricle."
He added that a randomized trial of leadless CRT will be very difficult to conduct. The SOLVE-CRT (Stimulation of the Left Ventricular Endocardium for Cardiac Resynchronization Therapy) randomized trial was conducted to assess the safety and efficacy of the WiSE system in support of US Food and Drug Administration approval, but that trial was stopped in April 2020 because of COVID-19, Defaye said. The trial will restart as a nonrandomized study in 2021.
"It is very difficult to perform a randomized study concerning CRT in 2021 because CRT is a class I indication for heart failure with left bundle branch block," Defaye said.
The study received no outside funding. Defaye has disclosed no relevant financial relationships.
Europace. Published online December 13, 2020. Full text
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Cite this: First Experience With Completely Leadless CRT - Medscape - Dec 28, 2020.