Micra Leadless Pacemaker Holds Up at 2 Years in Real-World Use

Patrice Wendling

September 03, 2021

Early benefits associated with the Micra leadless pacemaker (Medtronic) appear to be sustained through 2 years among more than 10,000 Medicare patients, according to new data from the Micra Coverage with Evidence Development (CED) study.

Micra leadless pacing cut the relative risk of reintervention by 38% and chronic complications by 31% compared with conventional transvenous pacemakers.

Despite the Micra group being sicker, there was no significant difference in adjusted all-cause mortality at 2 years, Jonathan Piccini, MD, reported in a late-breaking session at the virtual European Society of Cardiology (ESC) Congress 2021.

The single-chamber transcatheter Micra pacemaker was approved in the United States in April 2016, with the Centers for Medicare & Medicaid allowing reimbursement for implantation the following year through the CED study.

Short-term results reported last year showed no difference in the adjusted rate of acute complications or survival at 30 days between the Micra and traditional pacemaker groups but 23% fewer complications with Micra pacing at 6 months, said Piccini, Duke University Medical Center, Durham, North Carolina. Longer-term outcomes in real-world populations, however, have not been previously examined.

The present analysis included 6219 patients (44.1% female) who received the Micra pacemaker and 10,212 patients who (43.2% female) who received a transvenous device.

The Micra group was younger (mean, 79.5 vs 82.0 years) and less likely to have atrial fibrillation (81.5% vs 89.0%) but had more comorbid illness including end-stage renal disease (12% vs 2.3%), diabetes (45.1% vs 41.3%), and coronary artery disease (56.1% vs 53.3%). Mean Charlson Comorbidity Index scores were 5.1 vs 4.6, respectively.

After using propensity score overlap weights to account for baseline differences, the rate of chronic complication at 2 years was 4.6% with the Micra leadless pacemaker and 6.5% with transvenous pacemakers (hazard ratio [HR], 0.69; 95% CI, 0.60 - 0.81).

Patients in the Micra group had half as many device-related complications such as device failure, dislodgement, or infections (2.4% vs 4.8%; P < .0001) but a higher rate of other complications such as pericarditis and hemothorax (2.1% vs 1.4%; P = .002). Embolism and thrombosis rates were 0 vs 0.2% (P = .12).

The 2-year rate of reintervention was 3.1% with Micra vs 4.9% with transvenous systems (HR, 0.62; 95% CI, 0.45 - 0.85).

Among its components, patients who received the Micra pacemaker had fewer system revisions (0 vs 0.6%; P = .001), removals (0 vs 0.8% P < .0001), and upgrades to a dual-chamber (0.4% vs 0.8%; P = .06) or cardiac resynchronization therapy device (1.2% vs 1.7%; P = .025), but did have a higher rate of replacements (1.1% vs 0.4%; P = .002).

All-cause mortality was higher before adjustment (HR, 1.10; 95% CI, 1.04 - 1.17), likely due to the Micra patient characteristics, but was similar after adjustment (HR, 0.97; 95% CI, 0.91 - 1.04), Piccini said.

Session co-chair Carina Blomström-Lundqvist, MD, Uppsala University, Sweden, asked what the clinical implications are, given the lower risk of reinterventions and chronic complications. "Do you see these as an option for high-risk patients?"

Piccini pointed out that the choice of implant was up to the physician and that "very few clinics anywhere in the world have 12% of patients with end-stage renal disease or very high comorbidity burdens," as seen in those treated with the Micra pacemaker.

"In these high-risk, perhaps vulnerable patients, the improved outcomes in terms of lower rates of intervention and complications in extended follow-up is an important finding and should give clinicians confidence and reassurance when they choose this device for their patients that they are getting several advantages — reinforcing probably the very reason they chose the device in the first place," he said.

Co-chair Rik Willems, MD, KU Leuven in Leuven, Belgium, reminded Piccini that in his introduction he stated that one in every eight patients implanted with a conventional transvenous pacemaker has a complication, but that his data show this to be only about 1 in 15 or 16.

"Is the 1-in-8 an exaggeration or is that just due to the limited time you are looking at the patients here?" he asked.

Piccini said the 1-in-8 figure comes from a commonly cited prospective registry but that event rates improve over time. "It's fortunate that we're seeing lower complication rates compared to what has been historically reported."

The study was funded by Medtronic. Piccini disclosed a grant from the National Heart, Lung, and Blood Institute; grants for clinical research from Abbott, American Heart Association, Association for the Advancement of Medical Instrumentation, Bayer, Boston Scientific, and Philips; and serving as a consultant to Abbott, Abbvie, Altathera, ARCA Biopharma, Biotronik, Boston Scientific, Bristol Myers Squibb, LivaNova, Medtronic, Milestone, ElectroPhysiology Frontiers, Itamar, Pfizer, Philips, Sanofi, ResMed, and Up-to-Date.

European Society of Cardiology (ESC) Congress 2021: Late Breaking Science in Arrhythmias. Presented August 27, 2021.

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