Novel Mechanical Sensor in Medtronic's Micra Pacing System Evaluated to Detect Atrial Contractions and Restore AV Synchrony
July 2, 2018—Medtronic announced clinical study results that demonstrate that an investigational algorithm, utilizing the accelerometer signal in the company's Micra transcatheter pacing system (TPS) may restore atrioventricular (AV) synchrony, improving cardiac function in patients with sinus rhythm and AV block. The results from the MARVEL (Micra Atrial Tracking Using a Ventricular Accelerometer) feasibility study were published by principal investigator Larry Chinitz, MD, et al online ahead of print in Heart Rhythm simultaneous with their presentation at Heart Rhythm 2018, the Heart Rhythm Society's (HRS) 39th annual scientific sessions held May 9–12 in Boston, Massachusetts.
In Medtronic's announcement, Dr. Chinitz commented, "The results of MARVEL indicate that this novel mechanical sensor may allow more patients to benefit from a miniaturized leadless pacemaker. Although single-chamber pacing in the ventricle is quite safe for these patients, the preferred option is to treat them with a wired pacemaker in two chambers to maintain synchrony and cardiac function. However, patients with these traditional pacemakers are at risk of experiencing complications related to the pocket and the leads, and leadless pacemakers remove these risks." Dr. Chinitz is Cardiac Electrophysiologist and Director of NYU Langone's Heart Rhythm Center in New York, New York.
According to Medtronic, the MARVEL study evaluated 64 patients who already had a Micra TPS at 12 centers in nine countries. Investigators evaluated the ability for the Micra's accelerometer to monitor and detect contractions in the atrium, even though the device is implanted in the ventricle. Investigators also evaluated Micra's ability to pace the ventricle to contract in sequence with the atrium, creating AV synchrony. AV synchrony was measured using continuous device telemetry and an electrocardiogram via a Holter monitor.
The company reported that the study showed the percentage of AV beats in synchrony during pacing with the AV algorithm was 87% among all study patients (while they were at rest for 30 minutes), 80% in high-degree AV block patients, and 94.5% in patients with predominantly intact AV conduction during the study.
In patients with high-degree AV block who would benefit the most from AV synchrony, the algorithm yielded significantly greater AV synchrony (P < .001) compared with VVI pacing without the algorithm. In addition, AV block patients had a statistically significant improvement (P = .004) in stroke volume (blood flow out of the left ventricle) during AV algorithm pacing (23.9 cm, left ventricle outflow tract velocity time integral) compared with VVI pacing (21.8 cm).
Earlier results presented at HRS 2018 from the Micra Post-Approval Registry demonstrated major complications with Micra TPS were infrequent with a 63% lower risk for major complication (P < .001) compared with traditional pacing systems, advised Medtronic.
The Micra TPS does not require leads or a surgical "pocket" under the skin, so potential sources of complications related to such leads and pocket are eliminated—as are any visible signs of the device. Micra TPS utilizes an accelerometer—a miniaturized sensor inside the device that measures patient movement and determines appropriate pacing rates based on patient activity levels. Medtronic first introduced the Medtronic Micra TPS commercially in Europe in 2015 and in the United States in 2016 for patients who need a single-chamber pacemaker.