THE 2018 HEART RHYTHM SOCIETY SCIENTIFIC SESSIONS WERE HELD IN BOSTON, MASSACHUSETTS.
The results of the CABANA trial comparing ablation to drugs in the treatment of atrial fibrillation was the headline-story at the 2018 Heart Rhythm Society scientific sessions in Boston, held earlier this month, but there were many presentations of clinical data on new and established electrophysiology technologies. Here are a few highlights you may have missed.
Single-Center Report Raises Questions About Tendril Leads
St. Jude Medical Inc. Tendril pacemaker leads had a high-rate of failure over a short duration of follow-up in a single-single center experience reported at the HRS meeting.
Michael Sayegh and colleagues at Emory University School of Medicine and Georgia Institute of Technology in Atlanta, presented a poster on the performance of Tendril leads at their institution while comparing it to the performance of a control lead. "Our data show that Tendril leads have a high rate of failure over a short duration of follow-up. These findings are important to consider especially in pacemaker dependent patients," the authors conclude.
Specifically, they retrospectively analyzed outcomes with the Tendril STS 2088TCand1688TCmodels and Medtronic PLC'sCapSureFix Novus 4076. The 1688TC was approved by FDA in 2003, 2088TC was approved in 2009, and the Medtronic lead was approved in 2004. Despite being in regular clinical use for many years, data on Tendril lead performance is limited, according to Sayegh et al.
The study includes 751 Tendril leads (665 2088TCs and 86 1688TCs)and 269 CapSureFix leads implanted with pacemakers from January 2007 through May 2016. The investigators collected data on baseline demographics, clinical characteristics, and follow-up information. For the purposes of the study, the investigators defined lead malfunction as insulation breach, lead fracture, or rise in capture threshold.
The baseline demographics were similar, including patient-age at implantation, age at malfunction, and gender mix, and about a third of both groups also had an ICD. The most common reason the patients had a pacemaker was sinus node dysfunction, followed by AV block. The patients were followed for an average of 2.4 years.
The rate of malfunction of Tendril leads was significantly higher than that of CapSureFix Novus leads (6.83% vs. 0.37%, p < 0.01), and the most common cause of Tendril lead malfunction was insulation breach (76.47%) which manifested as "noise" (51%) or low impedance (25.5%). Lead fractures were the cause of 21.6% of the observed malfunctions in the Tendril patients. The most common management options following lead-malfunction was clinical monitoring (40.4% cases), device reprogramming (36.8%), or lead revision (17.5%) of cases. There was only insulation-breach malfunction in CapSureFix Novus group and that lead was revised.
In an email, Abbott told Medtech Insight:"Abbott reviews all research that helps us better understand physicians’ clinical experience with our products. This single center experience is not consistent with the global performance of our Tendril and Optimleads over nearly a decade of use. We look forward to working with this center to better understand the analysis and factors that may have contributed to their experience. It is worth noting that more than 80% of the leads that were classified as 'insulation breaches' due to the presence of noise are still in use and the observances were resolved via simple reprogramming."
Nevertheless, a number of physicians at HRS tweeted their doubts about the Tendril lead, including frequent-tweeter John Mandrola, an electrophysiologist at Baptist Health in Louisville. In a "Perspective" column published by Medscape, Mandrola called the results of the study by Sayegh et al. "stunning. "
"This was a retrospective single-center study with nonrandomized group comparisons. It has serious limitations and is not yet published," he points out. "That said, it's hard to dismiss an 18-fold greater risk for lead failure as spurious." Mandrola says both he and several other pacemaker-implanting doctors he spoke to have also seen these leads fail.
He points out that St. Jude had to recall itsRiataandRiata STICD leads due to unacceptably high risk of abrasion to the Optim silicone outer insulation. Tendril 2088TC also has Optim insulation. (Also see "St. Jude Agrees To Pay $39m To Settle Shareholder Suit" - Medtech Insight, 14 Jul, 2016.). "The safety of [St. Jude] leads therefore turns on the reliability of this proprietary insulation," he argues. "I see enough signal to warrant much more investigation into this potentially major health problem. And if this turns out to be a problem, we should also study how it eluded us for many years."
Meta-Analysis Finds No Benefit From Contact-Force Catheters
A meta-analysis of contact force catheters for atrial fibrillation-ablation finds these devices neither reduce fluoroscopy or procedure time and do not improve AF freedom ablations.
Contact-force catheters are supposed to make it easier for electrophysiologists to isolate the pulmonary vein during atrial fibrillation procedures. Thira Rattanakosit of the University of Adelaide in Australia and colleagues searched all the English-language literature for trials comparing the success-rate of contact-force-sensing catheters to standard ablation catheters up to August 2017.
They found four randomized controlled trials that compared contact-force ablation to standard ablation and measured atrial-fibrillation recurrence, procedure and fluoroscopy-time. The four trials included 417 participants with a mean follow-up of 10.2 months. The authors reported their meta-analysis of the trials as a poster at the HRS conference. The meta-analysis found that atrial fibrillation recurred following the ablation procedure in 30.5% of the patients treated with contact-force-guided pulmonary vein isolation and 30.6% of patients treated with non-contact-force catheters. Contact-force-guided ablation procedures were not significantly shorter overall or require less fluoroscopy time than procedures with the non-contact-force-sensing catheters.
"The present metaanalysis should be interpreted with caution due to apparent small number of participants," Rattanakosit et al report. However, this is not the first clinical evidence that contact-force sensing does not accomplish what it is supposed to. For example, a 120-patient randomized trial of Biosense Webster's Thermocool Smartouch, reported at the 2016 HRS meeting, found contact force sensing did not affect procedure and fluoroscopy duration or complication rates, but did reduce extremes of contact force. (Also see "HRS 2016 ROUND-UP: Medtronic Unveils New “Extravascular ICD”" - Medtech Insight, 12 May, 2016.)
Also, a 2017 reportof data in the Manufacturer and User Facility Device Experience database found atrioesophageal fistula formation accounted for a much higher proportion of reported adverse events with contact force-sensing catheters compared with non-CF-sensing catheters (78 vs 13, from 2,689 adverse event reports on approved ablation catheters).
Could Light Work Better Than Force In Guiding AF-Ablation?
One of the companies trying to improve atrial-fibrillation-ablation outcomes with better guidance during the procedure is LuxCath LLC , a subsidiary of Allied Minds. LuxCath is developing theOmniViewlight-guided ablation catheter which allows electrophysiologists to see and assess the catheter-tissue contact, tissue composition, and lesion quality. First developed at George Washington University, OmniView identifies stable and consistent tissue contact and allows the operator to assess lesion-progression. As the lesions are formed by the ablation process, the fluorescence of the natural tissue diminishes, showing that the tissue has been destroyed. The system has been verified in animals and in an 11-patient first-in-man trial in Europe which showed 100% procedural success.
"Today, everything [electrophysiologists do during AF-ablation] is indirect measurement," CEO Omar Amirana told Medtech Insight. The use of contact-force at the end of the catheter has become a gold standard, because it gives more information than they had previously, but at the end of the day, it's still just a question of force, and it tells you nothing about what is going on in the wall of the heart and tells you nothing about the myocardial viability or the metabolic activity in the wall of the heart. So, they're still very much hampered by not knowing what is going on metabolically."
"This is still an untapped frontier with no competition. It's still considered a holy grail," Amirana said. "The afib-ablation space is on fire and growing by leaps and bounds. There's a battle out there between all the big companies for market share. The thing we take comfort in is that today, being able to see a lesion is going to dramatically improve the procedure's efficiency so you don't have to wait until the patient has a recurrence to come back to the lab and have a re-do procedure. That has dramatic economic as well as clinical advantages."
The company is now preparing to run clinical trials to earn regulatory approvals in the US and Europe, but cannot yet announce when those trials will begin. "We'll probably take a walk-crawl-run type of approach and probably do several types of arrhythmia patients that are relatively straightforward and easy to do before migrating into more challenging and complex patients which we know how to do, but offer a little bit more robust and complex clinical study," Amirana said
The company used the 2018 HRS to demonstrate the OmniView for physicians and other companies, and to announce the establishment of a scientific advisory board, including several well-known electrophysiologists and clinical trialists, who will help guide the clinical trials of OmniView. The board will include Vivek Reddy, Mount Sinai Hospital and the Mount Sinai Health System in New York, David Haines of Beaumont Hospital in Michigan, Pierre Jais of L’Institut de Rythmologie et Modélisation Cardiaque in Bordeaux, Andrea Natale of the Texas Cardiac Arrhythmia Institute at St. David’s Medical Center, and Jeremy Ruskin from Massachusetts General Hospital in Boston.
ASD2 Results Support Medtronic's Extravascular Defibrillator
Data presented at the HRS Conference support the feasibility of a Medtronic PLC's EV-ICDlead, an ICD lead placed under the sternum and outside of the heart.
The results of the ASD2 feasibility study, presented by Lucas V.A. Boersma of the University of Amsterdam confirm that Medtronic's investigational extravascular ICD lead can sense, pace, and defibrillate the heart.
ASD2 is the first clinical study of pacing, sensing, and defibrillation from a lead designed specifically to sit in the substernal space, Boersma explained. The leads proximity to the heart allowed it to successfully pace 97% of patients with a low degree of extracardiac stimulation during pacing and terminate 83% of ventricular fibrillation episodes with a single 30 J shock, he said. This performance is comparable to that of existing ICDs.
"Clinicians are highly interested in the potential for an extravascular ICD solution to provide both pacing and lifesaving defibrillation therapy without leads placed inside the heart or vasculature," Boersma said. "The ASD2 study offers very encouraging clinical insights, which bring us closer to implanting the first chronic investigational system in ambulatory patients."
Medtronic hopes the EV-ICD System will offer the benefits of traditional transvenous defibrillators, while addressing some of the current limitations of subcutaneous implantable defibrillators, including the inability to provide painless bradycardia pacing or antitachycardia pacing.
ASD2 implanted the EV-ICD lead in 79 treaded with a defibrillation patch or a defibrillator emulator. The EV-ICD lead was set-up to sense activity in the ventricles, provide pacing to the ventricles, and deliver a 30-joule defibrillation shock after ventricular fibrillation was induced.
There were seven adverse events in in six of the 79 patients. In a press release, the company points out that "the investigational procedure and lead implantation tools were refined during the study, with further technique training and education provided to all investigators in an effort reduce the adverse event rate in future patients."
The company is now sponsoring a first-in-human, chronic study to assess the safety and efficacy of EV-ICD system in an ICD patient population.
MARVEL Shows Feasibility Of Accelerometer-Based Atrial Sensing
The results of the MARVEL (Micra Atrial TRacking Using A Ventricular AccELerometer)feasibility trial justify continued investigation of Medtronic's investigational algorithm that utilizes the accelerometer signal in the Micratranscatheter single-chamber "leadless" pacemaker.
Medtronic launched Micra TPS in Europe in 2015 and in the US in 2016. It is designed to be less-invasive than traditional pacemakers with transvenous leads ( (Also see "HRS 2017: Medtronic And Boston Scientific's Less-Invasive CRM Devices Perform As Hoped In Real-World Registries" - Medtech Insight, 14 May, 2017.))
The MARVEL results, presented at the HRS meeting by Larry Chinitz of New York University, show this novel mechanical sensor in Micra may be used to restore atrioventricular synchrony, improving cardiac function in patients with sinus rhythm and atrioventricular block.
"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," Chinitz said. "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."
The MARVEL study evaluated 64 patients who already had a Micra implanted in the ventricle and evaluated the ability of Micra's accelerometer to monitor and detect contractions in the atrium. The study also looked at Micra's ability to pace the ventricle in sequence with the atrium to create atrioventricular synchrony.
The study showed 87% of atrioventricular beats were in synchrony during pacing with the atrioventricular algorithm – 80% in high-degree block patients and 94.5% in patients with predominantly intact atrioventricular conduction. In the patients with high-degree atrioventricular block – the patients most likely to benefit from from atrioventricular synchrony – the investigational algorithm yielded significantly greater atrioventricular synchrony than standard VVI-pacing without the algorithm. The atrioventricular block patients also showed statistically significant improvement in left-ventricular blood-flow volume during pacing with the investigational atrioventricular algorithm compared to VVI pacing
Medtronic said it is investing in additional clinical studies to confirm this accelerometer-based leadless pacing approach will benefit patients with AV block, about 40% of the worldwide pacemaker population.
Also at HRS 2018, Mikhael El-Chami of Emory University in Atlanta presented results from 85 patients in the 1,498-patient Micra Post-Approval Registry who got a Micra after another device had to be explanted because it was infected.
Micra was successfully implanted in all 85 patients and the average follow-up in the study was 3.2 months. There were no Micra devices explanted due to infection during follow-up.
The median length of hospitalization following Micra implant was two days. Two patients died from sepsis during follow-up, but investigators determined that neither death was related to the Micra device or procedure. One patient required a system upgrade, and one patient developed a recurrent infection at the pocket site of the previously extracted device 11 days post-implant, but this was resolved with antibiotics.
El-Chami presented results from 795 patients in the Micra post-market registry at last year's HRS meeting. Those results showed a 99.6% implant success rate and a 1.51% major complication rate, both of which were better than the rates seen in the pre-market investigations of Micra. (Also see "HRS 2017: Medtronic And Boston Scientific's Less-Invasive CRM Devices Perform As Hoped In Real-World Registries" - Medtech Insight, 14 May, 2017.)
From the editors of Clinica