ORLANDO—As-needed anticoagulation could be effective in preventing stroke in at least some patients after successful ablation of atrial fibrillation, according to a pilot study presented at the 22nd Annual International Atrial Fibrillation Symposium. Neurologists are interpreting the results with caution, however.
The positive findings, originally reported at the 2016 Annual Meeting of the Heart Rhythm Society (HRS), were updated at the International Atrial Fibrillation Symposium by Francis Marchlinski, MD, Director of Cardiac Electrophysiology at the University of Pennsylvania in Philadelphia. When delivering the data, he provided several caveats before other atrial fibrillation experts added their own.
Guidelines Recommend Anticoagulation
The study was conducted in response to the substantial number of patients who request discontinuation of their anticoagulation therapy after a successful ablation for atrial fibrillation, according to Dr. Marchlinski. Current guidelines recommend anticoagulation in patients with atrial fibrillation following ablation if they have risk factors for stroke, even if their atrial fibrillation is controlled. The risk of stroke in patients with a negative ECG after ablation, however, appears to be “in the neighborhood of 0.1%,” according to Dr. Marchlinski, who cited five observational studies.
“There are no randomized prospective trials that have assessed the safety of stopping anticoagulants, but the fact is that this is a pretty low event rate if the observational studies are accurate, and even if they are off by severalfold, it is likely that we would be unable to show the benefit of continuing anticoagulants in these patients,” Dr. Marchlinski observed.
Researchers Observed One Cerebrovascular Accident
A strategy of as-needed anticoagulation has been made practical by the introduction of novel oral anticoagulants (NOACs), which have a rapid onset of action, relative to warfarin, and would therefore be expected to provide rapid protection against atrial-fibrillation-related stroke risk if initiated upon atrial fibrillation onset, according to Dr. Marchlinski. To test this approach, 105 “highly motivated” patients with atrial fibrillation were selected for the pilot study.
In addition to three weeks of ECG monitoring to confirm the absence of atrial fibrillation, patients participating in the trial were required to demonstrate skill in pulse assessment, which they agreed to perform on a twice-daily basis. Use of a smartphone app that can detect atrial fibrillation was encouraged, but not required. All patients were required to fill a prescription for a NOAC and told to initiate therapy for any atrial fibrillation episode of more than one hour.
Of the 105 patients, four were noncompliant with atrial fibrillation monitoring and were removed from the study. Another two patients voluntarily requested to return to daily NOAC treatment. The remaining 99 were followed for 30 months. Of these participants, 18 had multiple episodes of atrial fibrillation and were transitioned back to daily NOAC therapy. In all, 15 patients used NOAC on an as-needed basis at least once, but remained off daily therapy, and the remaining 66 did not have an episode of atrial fibrillation that triggered a course of NOAC therapy.
In 263 patient years of follow-up, there was a single cerebrovascular accident (CVA). This event occurred in an 81-year-old patient with a history of hypertrophic cardiomyopathy and an atherosclerotic aortic arch on imaging. The patient presented with neurologic symptoms, but had a negative ECG. The CVA symptoms resolved with treatment.
In presenting these data, Dr. Marchlinski said, “Pro re nata use of NOACs may be safe and effective to maintain a low risk of stroke when patients are adherent to diligent pulse monitoring.” However, he reiterated that the study group consisted of “a select group of motivated patients,” and he emphasized that the patients must be followed closely.
Are Risk Factors Well Understood?
In a discussion that followed this presentation, several experts expressed the usual caution about drawing conclusions from a single uncontrolled study, but Elaine M. Hylek, MD, Professor of Medicine at Boston University, expressed additional reservations about the “pill in a pocket” strategy. In particular, she noted an imperfect correlation between onset of atrial fibrillation and stroke risk. “I think this makes us [reluctant] to stop oral anticoagulation,” she said.
The available data suggest that “once the atrial fibrillation is gone, the risk of stroke recedes,” according to Daniel Singer, MD, Chief of Epidemiology at Harvard School of Public Health in Boston. He indicated, however, that all the variables of risk may not be fully understood. More “hard data” are needed to endorse a wider application of on-demand anticoagulation in patients like those entered into this study, he said.
The fact that patients without atrial fibrillation following ablation remain at substantial risk of atrial fibrillation recurrences, including asymptomatic episodes, is a liability of as-needed anticoagulation, conceded Dr. Marchlinski. However, these initial results provide promise for the substantial proportion of patients without atrial fibrillation after ablation who wish to avoid anticoagulants and are willing to consider risks and benefits.
Dr. Marchlinski reported financial relationships with Abbott, Biosense Webster, Biotronik, Boston Scientific, St. Jude Medical, and Medtronic.
—Ted Bosworth
Suggested Reading
Karasoy D, Gislason GH, Hansen J, et al. Oral anticoagulation therapy after radiofrequency ablation of atrial fibrillation and the risk of thromboembolism and serious bleeding: long-term follow-up in nationwide cohort of Denmark. Eur Heart J. 2015;36(5):307-314a.
Link MS, Haïssaguerre M, Natale A. Ablation of atrial fibrillation: patient selection, periprocedural anticoagulation, techniques, and preventive measures after ablation. Circulation. 2016;134(4):339-352.
Noseworthy PA, Yao X, Deshmukh AJ, et al. Patterns of anticoagulation use and cardioembolic risk after catheter ablation for atrial fibrillation. J Am Heart Assoc. 2015;4(11). pii: e002597.
