Is this clinically relevant AFib?
Dr. Schwamm acknowledged that there is a question of whether device-detected AFib should be thought about in the same way as clinically detected AFib with respect to future stroke risk.
He noted that, in this study, 67.4% of patients for whom AFib was detected by continuous monitoring (31 of 46 patients) had at least one episode of AFib that lasted more than 1 hour.
“This is not a trivial little squiggle of something on an EKG which then goes away. This is of significant duration that the cardiologist who adjudicated these rhythm strips felt confident was AF[ib].”
He added: “AF[ib] lasting more than 1 hour crosses the threshold for most practitioners I know to feel confident in treating the patient with anticoagulation. If it was symptomatic AF, this wouldn’t even be a question.”
Dr. Schwamm made the point that device-detected A AFib F has been accepted as worthy of treatment in patients after cryptogenic stroke.
“If we are honest with ourselves and if we have no hesitation in starting anticoagulation in a patient with cryptogenic stroke who has had device-detected AF 6 months later, should we decide that if the patient has had a lacunar stroke, we can ignore that same device-detected fibrillation?”
He put forward the idea that, at some level, all stroke is cryptogenic. “We never know for sure what the cause was. We have hypotheses, we have associations, but we don’t really know. So how much should we weigh that presumptive etiology in terms of how we interpret a rhythm disturbance of fibrillation?”
When looking for predictors of AFib in this study, the investigators found that patients were more likely to have an episode of AFib detected if they had one of the four following risk factors: congestive heart failure, left atrial enlargement, obesity, or QRS prolongation.
“In patients with any one of those four factors, 30% of those had device-detected AF[ib]. These are same predictors of AF[ib] that we are all accustomed to,” Dr. Schwamm said.
Shared decision-making
Dr. Schwamm said in an interview that, in his practice, for these patients, the decision as to whether to use continuous monitoring is made with the patient through shared decision-making.
“We discuss the chance that they could have AF[ib], and I suggest that it might be worth looking for it, but there are factors to be considered. There is a cost to the device, and reimbursement may depend on insurance coverage. Also, some patients may have strong feelings about having the chip implanted in their body.”
He says implanting the chip is easy. “It takes longer to check in at the front desk than to put the device in. It is injected under the skin. It just needs two stitches and a Band-Aid.” The device connects with a smartphone, and the results are interpreted by a cardiologist.
Dr. Schwamm pointed out that the optimal antithrombotic regimen for these patients in whom AFib is detected remains uncertain and should be the focus of future research.
“Do we just stick to antiplatelet therapy or advance to anticoagulation? In moving to an anticoagulant, are we providing less effective prevention for the atherosclerotic stroke risk at the expense of reducing the AF[ib]-related stroke risk? That may be a reasonable trade-off because we know the disability from AF[ib]-associated stroke is much higher.
“Or perhaps the optimal therapy is aspirin plus low-dose anticoagulant? Or left atrial appendage closure and an antiplatelet for patients at a higher risk of bleeding?” he said. “These are the really important questions we need to start asking.”
He added that he hopes a future study will address these questions, but he noted that it would have to be a large study, that it would have to first identify these patients and then randomly assign them to anticoagulation or to no treatment. “That is quite a major undertaking.”
In the highlights presentation, Dr. Jovin said he was uncertain of which of these patients in whom AFib is detected would benefit from anticoagulation. He said he would also like to see a randomized trial on this. But he added: “This would be challenging, as there is the issue of whether there would be equipoise to allow us to randomize to a placebo.”
Dr. Sansing agreed. “I think it would be a hard sell. I would have to think carefully about randomizing a patient to anticoagulation therapy or no therapy who has been found to have AF[ib].”
Dr. Schwamm noted that the current STROKE-AF study was not designed or powered to detect differences in stroke recurrence rates and that there was no difference in stroke recurrence rates between the two arms. There was also no randomization with regard to treatment; choice of medication was left to the discretion of the treating physician.
But he noted that only for 3 of the 34 patients with recurrent stroke in the continuous-monitor arm was AFib detected prior to the recurrent stroke, and only one of those three was receiving anticoagulation at the time of the recurrent stroke.
“These strokes were occurring in patients who did not have device-detected AF[ib],” Dr. Schwamm said. “This is because the population in this study were loaded with stroke risk factors and are at risk of recurrent stroke, but we don’t have the opportunity in this study to really understand the significance of the recurrent strokes.”
The STROKE AF trial was funded by Medtronic. Dr. Schwamm is a consultant to Medtronic.
A version of this article originally appeared on Medscape.com.