Of the 94,474 ischemic strokes that occurred in a nationwide registry among patients with known atrial fibrillation, 84% were preceded by inadequate anticoagulation, according to a report published online March 14 in JAMA.
Fully 30% of the patients in this retrospective cohort study weren’t taking any form of antithrombotic therapy before their stroke, even though all of them had atrial fibrillation (AF) and most of them had additional risk factors as well. And although nearly 20,000 of the study participants were taking warfarin before their stroke, 64% of them were taking subtherapeutic doses, said Ying Xian, MD, PhD, of the department of neurology at the Duke Clinical Research Institute, Durham, N.C., and his associates.
Dr. Ying Xian
These findings highlight tens of thousands of missed opportunities for preventing stroke simply by following existing guidelines, the investigators said.
In previous studies, researchers have consistently found underuse of oral anticoagulants in community practice. To examine current trends since the rapid adoption of non–vitamin-K antagonist oral anticoagulants (NOACs), Dr. Xian and his associates analyzed data from the AHA/ASA Get With the Guidelines-Stroke Registry. They determined the prevalence of antithrombotic treatment among AF patients who developed ischemic stroke, focusing on patients (mean age, 79.9 years) enrolled in the registry after being admitted for ischemic stroke to 1,622 participating U.S. hospitals during a 2.5-year period.
A total of 79,008 (83.6%) were not receiving therapeutic anticoagulation at the time of their stroke. This included 28,583 who were not taking any antithrombotic treatment, 12,751 who were taking subtherapeutic doses of warfarin (international normalized ratio,or INR, of less than 2 at the time of their stroke), and 37,674 who were taking only antiplatelet drugs when additional treatment was indicated, the investigators said (JAMA. 2017 Mar 14;317[10]:1057-67).
Among the minority of AF patients who were receiving therapeutic anticoagulation at the time of their stroke, 7,176 were taking adequate warfarin and 8,290 were taking adequate NOACs such as dabigatran (Pradaxa), rivaroxaban (Xarelto), and apixaban (Eliquis).
Stroke severity, as measured by median scores on the National Institutes of Health Stroke Scale, was significantly greater among patients receiving no antithrombotic medication, antiplatelet agents alone, or subtherapeutic levels of warfarin, compared with patients receiving therapeutic levels of warfarin or NOACs. Similarly, patients who had adequate anticoagulation before their stroke were significantly more likely to have better functional outcomes than those who did not. “These findings reinforce the importance of INR monitoring and dose adjustment to ... keep the INR in the therapeutic range,” Dr. Xian and his associates wrote.
The reasons why patients weren’t receiving adequate anticoagulation before their stroke – including any direct contraindications to treatment – were not available from the registry data. But such reasons are likely to persist after a stroke, and study clinicians were required to document such reasons in the medical records at hospital discharge. So the investigators examined reasons listed for not prescribing oral anticoagulation at hospital discharge in 58,084 patients.
A striking 38,249 AF patients (65.8%) in this large subgroup of study participants had no documented reason for not receiving oral anticoagulation, even after they were hospitalized for ischemic stroke and even though such documentation was “required.” Among the minority of patients whose records did show such reasons, the most common reason cited was bleeding risk (16.3%), followed by risk of falling (10.3%), the presence of a terminal illness (6.2%), patient or family refusal of the medication (4.3%), the patient’s impaired mental status (1.1%), adverse effects of the medication (1.0%), and allergy to the medication (0.6%).
This study was supported by the Patient-Centered Outcomes Research Institute. Dr. Xian reported that his institution received research funding from the American Heart Association, Daiichi Sankyo, Janssen, and Genentech. His associates reported ties to numerous industry sources.