Issue: August 2018
August 09, 2018
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New technologies continue to emerge for treatment of arrhythmias

Issue: August 2018
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Numerous new technologies providing solutions for patients with arrhythmia disorders are emerging, and several were unveiled at the recent Heart Rhythm Society Annual Scientific Sessions.

Among some of the new technologies are an algorithm to promote atrioventricular synchronous pacing with a ventricular leadless pacemaker, an extravascular implantable cardioverter defibrillator lead, an intramural needle ablation technology to treat refractory ventricular arrhythmias, a system providing multi-electrode contact mapping plus ablation to treat atrial fibrillation and a novel single-chamber ICD that can detect asymptomatic atrial arrhythmias.

The MARVEL study tested an algorithm developed for the ventricular leadless pacemaker (Micra, Medtronic) to help patients who require atrioventricular synchronous pacing.

“These patients were getting the benefits of a leadless pacemaker by the substantially lower complications, but they were not benefiting from atrioventricular synchrony, meaning their atrium was working, but this was a ventricular pacemaker alone,” Larry A. Chinitz, MD, FHRS, Alvin Benjamin and Kenneth Coyle, Sr. Family Professor of Medicine and Cardiac Electrophysiology and director of the Cardiac Electrophysiology and Heart Rhythm Center at NYU Langone Health, said during a press conference. “There is substantial value from [atrioventricular] synchrony, such as improvement in cardiac output, functional status, quality of life and loss of pacemaker syndrome. The question became, can the accelerometer that exists within the leadless pacemaker sense the acceleration of blood flow related to atrial contraction without there being a lead in the atrium?”

Larry A. Chinitz, MD, FHRS
Larry A. Chinitz

Chinitz and colleagues downloaded the algorithm into 70 patients with an existing ventricular leadless pacemaker; there were 64 usable Holter readings (mean age, 72 years; 31% women) for the study.

The mean atrioventricular synchrony rate was 87% (95% CI, 81.8-90.9; range, 30.2-100), and 83% of patients had an atrioventricular synchrony rate greater than 70%, Chinitz said.

“In the patients with [atrioventricular] block, we were able to achieve [atrioventricular] synchrony greater than 80% of the time,” Chinitz said during the press conference. “Complications were extraordinarily minimal. In patients with intact conduction, the presence of the algorithm did not interfere with their normal function. We also found that when patients increased their activity, there was a higher loss of [atrioventricular] synchrony because the signals within the heart get pushed together. However, at higher heart rates, most cardiac output is dependent on rate and not [atrioventricular] synchrony, so from a clinical perspective, we do not think the lower performance at higher heart rates will matter.”

Extravascular ICD lead

For the ASD2 study, Lucas V.A. Boersma, MD, PhD, from St. Antonius Hospital Nieuwegein, the Netherlands, and colleagues evaluated the feasibility of sensing, pacing and defibrillation from a novel acutely implanted lead (Medtronic) designed for the substernal space.

Lucas V.A. Boersma, MD, PhD
Lucas V.A. Boersma

“This is a new way of defibrillating the heart,” Boersma said during the press conference. “Instead of doing it from inside the heart, we did it by putting the lead under the sternum. There are many issues with ICD leads and there is a need to do something else aside from putting them in the vascular space.”

The subcutaneous ICD also addresses this problem, but cannot provide pacing, which the novel lead under the sternum close to the heart is able to do, he said.

The lead was placed in 79 patients (mean age, 62 years; 86% men).

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Ventricular pacing capture success was 76% in the ring-ring vector, 77% in the ring-coil vector and 97% in the coil-coil vector, Boersma said during the press conference.

Single 30-J shock success was 81% in the first episode, 86% in those with a second episode tested and 83% for all episodes together, he said.

There were seven adverse events in six patients, most of which were resolved without sequelae, he said.

Intramural needle ablation technology

An arrhythmia substrate that goes deep below the endocardium is a significant cause of ablation failure, so deep intramural radiofrequency lesions may be required. William G. Stevenson, MD, professor of medicine at Vanderbilt University Medical Center and a member of the Cardiology Today Editorial Board, and colleagues assessed the safety and efficacy of a novel irrigated needle catheter for mapping and ablation of ventricular arrhythmias that failed standard catheter ablation and antiarrhythmic drug therapy.

William G. Stevenson

“When ablation is needed for a ventricular tachycardia that originates from deep within the myocardium, beneath the endocardial surface, you may not be able to adequately damage the VT region with available technologies,” Stevenson, the co-inventor of the technology, said during the press conference. “In multicenter trials for ablation of VT, recurrence rates are in the range of 30% to 50%.”

Needle ablation was performed on 31 patients with refractory ventricular arrhythmias (mean age, 62 years; 27 men; 26 with sustained monomorphic ventricular tachycardia), two of whom required repeat ablation.

“Of the 31 patients, 49% had no recurrent VT whatsoever, and considering that this is a population who had failed prior ablation attempts and often had electrical storms or required IV medications, that was gratifying,” Stevenson said. “This is an indication that this ablation method can be helpful in the right patients.”

Eighteen percent of procedures had complications, most typical of catheter procedures and unrelated to needle ablation, he said.

Mapping and ablation system

Researchers tested a novel catheter (Globe Mapping and Ablation System, Kardium) among 60 patients with AF (mean age, 64 years) in the GLOBAL-AF study.

“One of the most critical questions is whether we can develop a new catheter that can combine all the options of a single-tip catheter with the easy use of a balloon catheter,” Hans Kottkamp, MD, from the department of electrophysiology at Hirslanden Hospital, Zurich, said during the press conference. “This catheter has 122 electrodes and multiple mapping options, so it is both an ablation and mapping catheter.”

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The technology achieved pulmonary vein isolation in 99.2% of veins. Mean procedure time was 147 minutes and mean fluoroscopy time was 11 minutes. Two patients had tamponade, one of which occurred before ablation, and there were no cases of stroke, transient ischemic attack, pulmonary vein stenosis, esophageal perforation or phrenic nerve palsy, Kottkamp said.

Single-chamber ICD

Brian Powell, MD, FACC, FHRS, medical director for cardiac electrophysiology at Sanger Heart & Vascular Institute, Atrium Health, and Amy Tucker, RN, advanced cardiac device nurse at Sanger, evaluated the ability of a single-chamber ICD with atrial sensing capabilities (VR-T DX ICD System, Biotronik) to determine the incidence of asymptomatic AF or other undiagnosed atrial arrhythmias in 152 patients (72% men) implanted with the ICD between May 2013 and August 2017.

Brian Powell, MD, FACC, FHRS
Brian Powell

The device had a sensitivity of 100% and a specificity of 96.64% for detection of events in the ventricular tachycardia/ventricular fibrillation zone, he said, noting that some undersensing was observed, which could mean atrial arrhythmia incidence was higher than reported.

“This novel single-chamber ICD with atrial sensing capabilities detected atrial fibrillation that did not fall into any [ventricular tachycardia] detection zone,” Powell said during the presentation. “Larger studies will be needed to determine if this unique lead technology could reduce the risk of stroke by initiation of anticoagulation when asymptomatic AF is detected.” – by Erik Swain

Disclosures: The ASD2 and MARVEL studies were funded by Medtronic. The GLOBAL-AF study was funded by Kardium. Boersma reports he received compensation for services from Abbott, Boston Scientific and Medtronic, received research grants from Medtronic and received fellowship support from Boston Scientific. Chinitz reports he received compensation for services from Abbott, Biosense Webster, Biotronik, Medtronic and Pfizer and fellowship support from Biotronik, Boston Scientific and Medtronic. Kottkamp reports he consults for Biosense Webster and Kardium and holds equity in Kardium. Powell reports he consults for Biotronik, Boston Scientific, Medtronic and St. Jude Medical. Stevenson reports he received compensation for services from Abbott and Boston Scientific and holds intellectual property rights for a product made by Biosense Webster.

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