Implantable Cardiac Monitor (ICM) from Medtronic’s insertable REVEAL XT device published resulted in detecting atrial fibrillation in 30% of cryptogenic stroke patients at 36 months of follow-up in the CRYSTAL AF trial. Seventy-seven percent of first episodes of AF detected through 36 months were asymptomatic. The CRYSTAL AF Trial also discovered a surprising AF detection rate of only 3% in the control group randomized to standard monitoring with resting 12 lead EKG and Holter monitoring studies. These findings (reported at the American College of Cardiology (ACC) meeting in Washington DC) help document the use of long (long) term Implantable Cardiac Monitors.
Thirty percent of all strokes are cryptogenic; that is, of unknown mechanism despite a thorough workup. The rationale underlying the CRYSTAL AF (Cryptogenic Stroke and Underlying Atrial Fibrillation) study was that many of these strokes are actually due to AF, which has gone undetected by conventional methods. The detection of AF in a patient with a history of ischemic stroke warrants initiation of long-term oral anticoagulation therapy, the cardiologist noted.
The CRYSTAL AF study randomized 441 cryptogenic stroke patients to the REVEAL XT insertable cardiac monitor (ICM) or conventional monitoring for possible AF. The 6- and 12-month outcomes were presented earlier this year at the International Stroke Conference. The AF detection rates were significantly higher in the ICM group at both time points. At ACC 14, Dr. Passman presented the updated 36-month outcomes.
The median time from randomization to AF detection was 8.4 months in the ICM recipients. That’s well beyond the time frame during which external monitoring can realistically be used, he noted.
Fully 95% of patients with AF detected via ICM had at least 1 day with an episode duration greater than 6 minutes. Among patients with AF detected by ICM within the first 12 months, about half had one or more episodes of 12 hours duration or longer.