Aspirin as Standalone Stroke Protection Still Overused for Patients With A-fib

As recently as 2012, more than one-third of US patients with A-fib were treated with aspirin alone in spite of the fact that oral anticoagulation has been shown to be much more effective for reducing thromboembolic risk, a large registry study shows.

Patients with coronary heart disease (CHD) and risk-equivalent conditions—which often warrant treatment with aspirin—on top of A-fib were more likely to be treated only with the antiplatelet, lead author Jonathan Hsu, MD (University of California, San Diego), and colleagues report.

“We [practitioners] have an automatic inclination . . . to use aspirin in these patients, because we know it can reduce thrombosis in the arterial bed,” Hsu told TCTMD. “That being said, once a patient has atrial fibrillation we know that antiplatelets are not good enough to reduce thrombosis or clot formation in the heart as a result of atrial fibrillation. So immediately we should be thinking about true blood thinners or oral anticoagulants.”

He added that in most such patients an oral anticoagulant alone will likely provide enough protection against thrombotic events. Although some studies have suggested that aspirin has some benefit in patients with A-fib, “we know it’s a Band-Aid,” Hsu said. “We know it’s nowhere near as effective as the oral anticoagulant and [some evidence] suggests it’s not doing anything at all.”

Commenting on the study for TCTMD, Geoffrey Barnes, MD (University of Michigan, Ann Arbor), said, “It’s disappointing but not at all surprising. I think this is a story that we’ve heard over and over again, that patients are frequently undertreated for stroke prevention in atrial fibrillation.”

The message that patients with atherosclerotic disease need to be treated with antiplatelet therapy has been drilled home to cardiologists and internists, but awareness of the absolute necessity of oral anticoagulation to prevent stroke in A-fib is not as widespread, he said.

The latter message has started to take hold in recent years following publication of trials like WOEST and AVERROES, Barnes reported, noting that the impact of that dissemination could not be captured in the current study, which covered patients treated between 2008 and 2012.

“Only in the last couple years I think have we had a real emphasis on this message that patients with stable atherosclerotic disease, such as patients who’ve had an MI more than a year in the past, who’ve had a coronary stent more than a year in the past, if they need anticoagulation therapy for atrial fibrillation, it’s safe and reasonable to not give them concurrent antiplatelet medicines,” he said. “We need to continue to work to send the message that the anticoagulation therapy really should trump antiplatelet therapy as long as you have not had recent active coronary disease.”

Atherosclerotic Disease Tied to Greater Aspirin Use

In the current study, published online ahead of the June 28, 2016, issue of the Journal of the American College of Cardiology, Hsu and colleagues looked at use of aspirin or oral anticoagulation in outpatients with A-fib and intermediate-to-high thromboembolic risk enrolled in the American College of Cardiology’s PINNACLE registry at 123 cardiology practices in 38 states. The primary analysis included 210,380 patients who had a CHADS₂ score of 2 or higher.

Overall, 38.2% of patients were taking aspirin alone and the rest were taking oral anticoagulation. In the latter group, 90.9% were treated with warfarin, 7.2% were taking dabigatran (Pradaxa; Boehringer Ingelheim), and 1.9% were receiving rivaroxaban (Xarelto; Janssen Pharmaceuticals). Apixaban (Eliquis; Bristol-Myers Squibb) and edoxaban (Savaysa; Daiichi Sankyo) were not yet approved.

There was substantial variability across practices, however, suggesting “that focusing on factors at the practice level, and not simply at the individual physician level, may prove important in future efforts to rectify proper prescription of [oral anticoagulation] in [A-fib] patients at risk for stroke,” the authors write.

After multivariate adjustment, hypertension, dyslipidemia, CAD, prior MI, unstable and stable angina, recent CABG, and PAD were associated with prescription of aspirin only (P < 0.001 for all).

Factors tied to use of oral anticoagulation, on the other hand, were male sex, higher body mass index, prior stroke/transient ischemic attack, prior systemic embolism, and congestive heart failure (P < 0.001).

The findings were similar in a secondary analysis of 294,642 patients who had a score of 2 or higher on the newer CHA₂DS₂-VASc score, which incorporates more CHD risk equivalents.

More Education Needed for Patients and Physicians

Hsu said suboptimal use of oral anticoagulation needs to be addressed both with physicians and patients.

For the physician, he said, awareness needs to be increased that patients with vascular disease and A-fib require oral anticoagulation to prevent stroke, as indicated by the well-validated risk scores.

Barnes agreed that further education of physicians is necessary, particularly regarding the impact of the newer oral anticoagulants. “I don’t think there’s been a lot of discussion that some of these newer anticoagulants may be safer alternatives, certainly more effective but perhaps without the same bleeding risk, and really a better alternative to aspirin therapy for stroke prevention in atrial fibrillation,” he said.

Hsu added that patients need to be educated, as well, because they can be reluctant to start taking an anticoagulant. “I understand that. When I see patients, no one ever thanks me for starting them on oral anticoagulation,” Hsu said. “We know from clinical studies and large randomized controlled data that we are helping patients reduce their risk of stroke and saving lives, but we can’t prove that to a patient because they’ll never know . . . whether or not they’re saved from a stroke.”

In an accompanying editorial, Sanjay Deshpande, MD, and L. Samuel Wann, MD (Columbia St. Mary’s Hospital, Milwaukee, WI), argue that concerns about bleeding and the presence of concomitant indications for aspirin are not compelling explanations for why A-fib patients are undertreated.

“Cognitive dissonance (think of death-defying helmetless motorcycle riders and perpetually optimistic slot machine players) and unconscious bias may play a role in justifying continuation of old habits, denying new evidence that requires uncomfortable and inconvenient change,” they write. “Patient choice and the ‘art of medicine’ may be cited to rationalize illogical decisions that conflict with scientific evidence.”

Moreover, they say, “The process of anticoagulation is not a particularly attractive proposition, entailing compliance with a long-term regimen that many patients and their physicians find burdensome, with inevitable nuisance, expense, annoying minor side effects, and infrequent, but devastating, complications, such as intracerebral hemorrhage, and with only an abstract future benefit for perhaps four or five of 100 patients who would suffer a stroke if they did not receive anticoagulation.”

They conclude that “physicians and their patients should not sidestep the real risks of thromboembolism due to atrial fibrillation and the benefits of real anticoagulation, relying instead on aspirin, which has bleeding risk, but little, if any, therapeutic benefit.”

Related Stories:

• US Cardiologists Are Underusing Oral Anticoagulation for A-fib
• Substantial Minority of Low-Risk A-fib Patients Still Given Anticoagulants
• Oral Anticoagulant Use for A-fib in Community Practice Appears Appropriate