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CRYSTAL AF: Insertable cardiac monitor detected AF in patients with cryptogenic stroke
SAN DIEGO — An insertable cardiac monitor was superior to standard cardiac monitoring for the detection of atrial fibrillation in patients with cryptogenic stroke.
The likelihood of AF detection was more than sixfold for patients with cryptogenic stroke implanted with an insertable cardiac monitor (Reveal XT, Medtronic) compared with those undergoing standard cardiac monitoring, researcher Rod Passman, MD, MSCE, said during an International Stroke Conference press briefing.
A potential clinical implication is that patients who have had a stroke and are later found to have a diagnosis of AF could be shifted from antiplatelet therapy to anticoagulant therapy, which is more effective at preventing recurrent strokes in patients with AF, said Passman, from Northwestern University Feinberg School of Medicine.
Rod Passman
“In almost all of the cases, once AF was found, the treatment was changed from antiplatelet therapy, which we know is not a very good treatment for stroke in AF, to anticoagulation, which we know is an excellent treatment,” he said.
Richard Bernstein, MD, PhD, also from Northwestern University Feinberg School of Medicine, and colleagues enrolled 441 patients (mean age, 61.5 years; 63% men) with cryptogenic stroke in the CRYSTAL AF study. Patients received the insertable cardiac monitor (n=221) or standardized cardiac monitoring (n=220).
The primary endpoint was detection of AF (>30 seconds) within 6 months of randomization. At 6 months, AF was detected in 8.9% of patients in the insertable cardiac monitor arm vs. 1.4% of patients in the standardized cardiac monitoring arm (HR=6.43; 95% CI, 1.9-21.74). At 12 months, the primary endpoint occurred in 12.4% of patients in the insertable cardiac monitor arm vs. 2% of controls (HR=7.32; 95% CI, 2.57-20.81).
Richard Bernstein
At 6 months, 74% of patients in the insertable cardiac monitor arm were asymptomatic during their first AF episode, compared with 33% of those in the standardized cardiac monitoring arm with AF, Passman said. At 12 months, the rates were 79% in the insertable cardiac monitor arm and 50% standardized cardiac monitoring arm, he said.
Another reason the higher rate of AF detection by the insertable cardiac monitor is important, according to Passman, is that recent research has shown that “less AF is necessary to be associated with stroke than we had previously thought.
“Another point is that in the electrophysiology world, we say that AF begets AF. A 6-minute episode today can become a 6-hour episode tomorrow. We need to intervene when we have a window of opportunity before something terrible happens.” – by Erik Swain
For more information:
Bernstein R. Plenary Session III: Abstract LB11. Presented at: International Stroke Conference 2014; Feb. 12-14, 2014; San Diego.
Disclosure: The study was funded by Medtronic. Bernstein reports financial ties with Boehringer Ingelheim, Bristol Myers-Squibb/Pfizer and Medtronic. Passman reports financial ties with Medtronic.
Perspective
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It is part of a growing trend that many people whom we’ve diagnosed with cryptogenic stroke indeed have bouts of AF. This isn’t the only study to show that, but it is unique in the data I’ve seen in terms of the length of monitoring. Other studies I’ve seen monitor for 1 week or 1 month. As you can see from the curves shown in CRYSTAL AF, a lot of the pickup happens during the first week or the first month, but the curve continues to go up, even past 3 months. It means there is a lot of AF out there.
The missing information is whether all AF is the same and carries the same risk for stroke, and whether it will dictate the same treatment. That is still a question that remains to be answered. The stakes are high to make that decision, because we do have an effective treatment in anticoagulation therapy. If we can fill in a couple of the gaps in knowledge, we may be able to have an enormous impact on stroke prevention. Cryptogenic stroke is a large group, and a large subgroup of cryptogenic stroke is showing up as having AF.
Perspective
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Many practitioners have suspected AF to be the cause of many cryptogenic strokes, but AF can be intermittent, asymptomatic, and elude detection by short-term monitoring. Although finding AF after cryptogenic stroke should prompt a change from antiplatelet therapy to oral anticoagulation, the optimal strategy for identifying intermittent AF after cryptogenic stroke has been unknown. Now, the CRYSTAL AF investigators have provided insight: They compared standard cardiac monitoring according to local standards to the use of an insertable cardiac monitor for detecting AF after cryptogenic stroke, and found that the insertable cardiac monitor is superior to standard monitoring to detect AF in both short-term (8.9% at 6 months [HR=6.43]) and longer-term (30% at 36 months [HR=8.78]) follow-up.
In my opinion, the finding of AF in 30% of the patients at 36 months is of huge clinical importance, especially since 92.3% of patients with AF in the insertable cardiac monitor arm had a day with AF lasting 6 minutes or longer; 61.6% of those episodes lasted 6 hours or longer. Furthermore, 74% of the episodes were asymptomatic, and 66% of the patients in CRYSTAL AF had a CHADS2 score ≥3, making the population very clinically relevant. Notably, the complication rate of device implantation was low, and unlike for infections in patients with transvenous cardiac rhythm management devices, removal of insertable cardiac monitors is a simpler procedure by orders of magnitude.
A possible limitation of CRYSTAL AF relates to the accuracy of the insertable cardiac monitor to accurately distinguish AF from other irregular rhythms, such as sinus with premature atrial complexes or premature ventricular contractions. Thus, we do await the final paper to answer these and other questions. For example, the insertable cardiac monitor requires 2 minutes of AF to be present before it is registered, but the trial used AF lasting only 30 seconds to define an episode. Was the occurrence of AF even higher than reported in the insertable cardiac monitor patients? And, did characteristics of AF, the “AF burden” affect outcome? Did multiple short episodes carry the same risk as less frequent longer ones? Regardless, since the consequences of stroke due to AF are devastating and the risk of recurrent stroke substantial, appreciating the frequent occurrence of AF in the cryptogenic stroke population has the potential for hugely impacting management and outcomes in this population; in this study, 97% of patients who had AF detected had their management changed to oral anticoagulation.
Finally, the authors recommend that long-term continuous monitoring be performed in patients with cryptogenic stroke. Questions notwithstanding, the clinical challenge now will be to get the word out, and for the strategy to be adopted.