From the Journals

Atrial fib guidelines may fall short on oral anticoagulation

 

Key clinical point: Anticoagulation thresholds based on CHA2DS2-VASc risk score varied from population to population.

Major finding: After accounting for differing rates of stroke in published studies, the benefit of warfarin anticoagulation varied nearly fourfold. Anticoagulation thresholds were lower but still varied widely in a model of non–vitamin K antagonist therapy.

Study details: Markov state-transition model of 33,434 patients with nonvalvular atrial fibrillation.

Disclosures: The study had no primary funding source. Dr. Shah reported having no conflicts of interest. Three coinvestigators disclosed research support from relevant pharmaceutical or device companies.

Source: Shah SJ et al. Ann Intern Med. 2018 Sep 25. doi: 10.7326/M17-2762.

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Risk score is not “one size fits all”

Based on this study, the CHA2DS2-VASc score threshold for anticoagulation might not be a “one-size-fits all approach but rather a starting point for a more tailored assessment,” wrote Jennifer M. Wright, MD, and Craig T. January, MD, PhD, in an editorial accompanying the report.

The CHA2DS2-VASc algorithm uses fixed whole integers and therefore might lack the sensitivity and flexibility needed to accurately reflect the effects of its components, the experts wrote. “For example, female sex now seems to be a risk modifier, and its intensity depends on other risk factors.”

However, CHA2DS2-VASc remains the main way to assess net clinical benefit of oral anticoagulation for patients with anticoagulation, they conceded. “When it comes to the conversation about the risks and benefits of anticoagulation for our patients with atrial fibrillation, we must remember that each patient is an individual and has his or her own ‘score.’ ”

The editorialists are with the University of Wisconsin in Madison. They reported having no relevant conflicts of interest. These comments are based on their editorial (Ann Intern Med. 2018 Sep 25. doi: 10.7326/M18-2355).


 

FROM THE ANNALS OF INTERNAL MEDICINE

Anticoagulation thresholds based on CHA2DS2-VASc risk score varied from population to population, researchers reported in the Annals of Internal Medicine.

After accounting for differing rates of stroke in published studies, the benefit of warfarin anticoagulation varied nearly fourfold, said Sachin J. Shah, MD, of the University of California San Francisco and his associates. They called for guidelines that “better reflect the uncertainty in current thresholds of stroke risk score for recommending anticoagulation.”

Oral anticoagulation markedly reduces risk of ischemic stroke in patients with atrial fibrillation but increases the risk of major bleeding, including intracranial hemorrhage, which often is fatal. Therefore, when deciding whether to recommend oral anticoagulation, physicians must estimate clinical net benefit by quantifying the difference between reduction in stroke risk and increase in major bleeding risk, weighted by the severity of each outcome.

Guidelines on nonvalvular atrial fibrillation from the European Society of Cardiology and joint guidelines from the American Heart Association, American College of Cardiology, and Heart Rhythm Society (AHA/ACC/HRS) recommend oral anticoagulation when CHA2DS2-VASc (congestive heart failure, hypertension, age, diabetes, stroke, and vascular disease) risk score is 2 or greater. These guidelines implicitly assume that a particular CHA2DS2-VASc score denotes the same amount of risk across populations, even though a recent meta-analysis found otherwise, as the researchers noted.

To further test this assumption, they applied an existing Markov model to data from more than 33,000 members of the ATRIA-CVRN cohort. All patients had nonvalvular atrial fibrillation, were members of Kaiser Permanente Northern California, and were diagnosed during 1996-1997. About 81% had a CHA2DS2-VASc score of at least 2. For each patient, the researchers produced four estimates of the net clinical benefit of oral anticoagulation based on ischemic stroke rates from ATRIA, the Swedish AF cohort study, the SPORTIF study, and the Danish National Patient Registry.

Optimal anticoagulation thresholds were a CHA2DS2-VASc score of 3 or more using stroke rates from ATRIA, 2 or more based on Swedish AF rates, 1 or more based on SPORTIF rates, and 0 or more using rates from the Danish National Patient Registry. Oral anticoagulation thresholds were lower but still varied widely after accounting for the lower rates of intracranial hemorrhage associated with non–vitamin K antagonist therapy.

Therefore, current guidelines based on CHA2DS2-VASc score may need revising “in favor of more accurate, individualized assessments of risk for both ischemic stroke and major bleeding,” the investigators wrote. “Until such time, guidelines should better reflect the uncertainty of the current approach in which a patient’s CHA2DS2-VASc score is used as the primary basis for recommending oral anticoagulation.”

The study had no primary funding source. Dr. Shah reported having no conflicts of interest. Three coinvestigators disclosed research support from relevant pharmaceutical or device companies.

SOURCE: Shah SJ et al. Ann Intern Med. 2018 Sep 25. doi: 10.7326/M17-2762

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