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Insertable cardiac monitors effective, provide value for poststroke AF

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NASHVILLE, Tenn. — Two studies of insertable cardiac monitors presented at the International Stroke Conference demonstrated that the devices were effective for the identification of atrial fibrillation in patients previously diagnosed with cryptogenic stroke and cost effective for the prevention of recurrent stroke.

In the CRYSTAL AF randomized controlled trial, presented at ISC 2014, the likelihood of AF detection was more than sixfold for patients with cryptogenic stroke implanted with an insertable cardiac monitor compared with patients who received standard cardiac monitoring.

Real-world analysis

Paul D. Ziegler

Paul D. Ziegler, MS, and colleagues analyzed the incidence and duration of AF episodes in a real-world population of 1,247 patients (mean age, 65.3 years) with an insertable cardiac monitor (Reveal LINQ, Medtronic) for AF detection after cryptogenic stroke.

Overall, 1,521 AF episodes were detected by the insertable cardiac monitor in 147 patients, corresponding to a detection rate of 12.2% at 180 days, which was 37% higher than in CRYSTAL AF at the same time point.

The median duration of the longest detected AF episode was 3.4 hours, and 25% of patients with AF had an episode longer than 11.8 hours, the researchers reported.

The real-world results validate the findings of CRYSTAL AF and may ultimately show that the device is more effective than what was observed in that trial, owing to differences in the rigor of stroke workup or inclusion and exclusion criteria, the researchers concluded.

“While CRYSTAL AF demonstrated that AF is detected at a clinically significant rate, it was unclear how these results would transfer to real-world practice,” Ziegler, of Medtronic’s Cardiac Rhythm and Heart Failure Business in Mounds View, Minnesota, told Cardiology Today. “These results suggest that AF may go undetected at an even greater rate, and reinforce the benefits of long-term rhythm monitoring in patients with cryptogenic stroke. Long-term, insertable cardiac monitors may be a valuable tool for physicians managing patients with cryptogenic stroke to help detect arrhythmias. Detecting AF in patients with cryptogenic stroke enables physicians to change the patient’s medical therapy to potentially help reduce the risk for having a second stroke.”

Cost-effectiveness study

In a second study, Alex Diamantopoulos, MSc, from Symmetron in Borehamwood, United Kingdom, and colleagues assessed whether detection of AF with an insertable cardiac monitor is cost effective for preventing recurrent stroke in patients with cryptogenic stroke compared with the standard of care.

Diamantopoulos and colleagues developed a lifetime Markov model to use data from CRYSTAL AF and synthesized these with evidence from other trials to estimate cost effectiveness of the insertable cardiac monitors.

The researchers found that insertable cardiac monitors were associated with fewer recurrent strokes and increased quality-adjusted life-years (QALYs) compared with conventional patient follow-up.

Patients with insertable cardiac monitors had lower stroke-related costs, but higher overall costs, according to the researchers.

In the base-case analysis, the incremental cost-effectiveness ratio was below a 20,000 British pound per QALY gained willingness-to-pay threshold, which was developed by the U.K.’s National Institute of Clinical Excellence to assess the reimbursement of technologies in the National Health Service. The incremental cost-effectiveness ratio was further reduced when the researchers considered patient populations with a higher risk for stroke, defined as a CHADS₂ score of 3 or more.

Insertable cardiac monitors “appear to be a cost-effective diagnostic tool for the prevention of recurrent stroke in patients with cryptogenic stroke in the U.K. and countries with similar health care systems,” the researchers wrote in an abstract. – by Erik Swain

References:

Diamantopoulos A. Abstract 14.

Richards M. Abstract 206. Both presented at: International Stroke Conference; Feb. 11-13, 2015; Nashville, Tenn.

Disclosure: Diamantopoulos reports being employed by a company that receives grants from Medtronic. Ziegler reports being employed by and holding equity in Medtronic.