ORLANDO (FRONTLINE MEDICAL NEWS) – A pilot study that suggested as-needed anticoagulation could be effective in preventing stroke in at least some patients after successful ablation of atrial fibrillation (AF) was received with caution at the annual International AF Symposium.

The positive findings, originally reported at the 2016 annual meeting of the Heart Rhythm Society (HRS), were updated at AF Symposium 2017 by Francis Marchlinski, MD , director of cardiac electrophysiology at the University of Pennsylvania. When delivering the data, he provided several caveats before other AF experts added their own.

The study was conducted in response to the substantial number of patients who request discontinuing anticoagulation therapy after a successful ablation for atrial fibrillation, according to Dr. Marchlinski. Current guidelines recommend anticoagulation in AF patients following ablation if they have risk factors for stroke even if their AF is controlled. However, according to Dr. Marchlinski, who cited five observational studies, the risk of stroke in patients with a negative electrocardiogram after ablation appears to be “in the neighborhood of 0.1%.”

“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.

A strategy of as-needed anticoagulants 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 AF-related stroke risk if initiated upon AF onset, according to Dr. Marchlinski. To test this approach, 105 “highly motivated” AF patients were selected for the pilot study.

In addition to 3 weeks of ECG monitoring to confirm the absence of AF, 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 AF was encouraged but not required. All patients were required to fill a prescription for a NOAC and told to initiate therapy for any AF episode of more than 1 hour.

Of the 105 patients, four were noncompliant with AF monitoring and 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, 18 had multiple episodes of AF and were transitioned back to daily NOAC therapy, 15 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 AF that triggered a course of NOAC therapy.

In 263 patient years of follow-up, there was a single cerebrovascular accident (CVA). This 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, “PRN 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 the patients must be followed closely.

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, Boston University, added additional reservations to the “pill in a pocket” strategy. In particular, she noted an imperfect correlation between onset of AF and stroke risk. “I think this makes us [reluctant] to stop oral anticoagulation,” she said.

According to Daniel Singer, MD , chief of epidemiology, Harvard School of Public Health, Boston, the available data suggest that “once the AF is gone, the risk of stroke recedes,” but he indicated that all the variables of risk may not be fully understood. He said more “hard data” are needed to endorse a wider application of on-demand anticoagulation in patients like those entered into this study.

The fact that patients without AF following ablation remain at substantial risk of AF 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 AF after ablation that wish to avoid anticoagulants and are willing to consider risks and benefits.

Dr. Marchlinski reports financial relationships with Abbott, Biosense Webster, Biotronik, Boston Scientific, St. Jude Medical, and Medtronic.