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AF-stroke relationship strongest in black patients
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Among patients with atrial fibrillation, black patients had increased risk for having an ischemic stroke before or after an AF diagnosis compared with white patients, according to a study published in HeartRhythm.
Nearly half of ischemic strokes in patients with incident AF occurred before their diagnosis, according to the researchers.
“To date, large phase-3 clinical trials that have evaluated the safety and efficacy of novel blood thinner medications for AF have enrolled very few African American participants, which left us with little data about risks for this patient population,” Rajat Deo, MD, MTR, associate professor of cardiovascular medicine at the Perelman School of Medicine at the University of Pennsylvania, said in a press release. “Now, having identified that African Americans with AF are more at risk for stroke will allow us to more proactively monitor and treat these patients before an adverse event occurs.”
Racial differences in stroke
Parin J. Patel, MD, of the division of cardiology at St. Vincent Medical Group in Indianapolis, and colleagues analyzed data from 3,507 patients who developed incident AF during the Penn Atrial Fibrillation Free study. The cohort included both white (n = 2,230; mean age, 64 years; 66% men) and black patients (n = 1,277; mean age, 63 years; 53% men).
Patients were free from AF and atrial flutter and did not have a history of stroke at baseline. Information on comorbid conditions and demographic characteristics were also reviewed.
The primary outcomes of interest were hemorrhagic and ischemic strokes either 6 months before or 6 months after an AF diagnosis. Follow-up was conducted from the date of the index visit until December 31, 2013.
During follow-up, 538 patients had ischemic strokes and 54 patients had hemorrhagic strokes.
Ischemic strokes
Approximately half of ischemic strokes (47%) occurred within 6 months before an AF diagnosis, most of which occurred either within 7 days before (n = 30) or on the day of (n = 158) an AF diagnosis. The other ischemic strokes occurred a median of 3.6 years after AF was diagnosed.
After multivariable adjustment, black patients had an independently higher risk for ischemic stroke before (adjusted OR = 1.37; 95% CI, 1.03-1.81) or after (adjusted HR = 1.67; 95% CI, 1.3-2.14) a diagnosis of AF compared with white patients.
“The PAFF study suggests a critical need for interventions that target the approximate 50% of ischemic strokes occurring before a diagnosis of AF,” Patel and colleagues wrote. “Effective strategies for reducing stroke risk will require a better understanding of the significance of subclinical AF and potentially novel cardiovascular risk markers such as left atrial structure and mechanics. Clinical studies should be designed to identify individuals in sinus rhythm that have subclinical AF and thromboembolic complications.”
“Given what we already know, it is time to act on these disparities while continuing to investigate other race-related factors such as differential access to preventive health care and compliance with prescribed medications,” Sumeet S. Chugh, MD, FHRS, medical director of the Heart Rhythm Center at Cedars-Sinai Heart Institute, wrote in a related editorial. “While the present study adjusted for several comorbid conditions, there remains the possibility of residual confounding, especially due to varying degrees of severity of these conditions, for example, diabetes vs. complicated diabetes. It is also possible that there are other race-specific characteristics such as differences during atrial mechanical function in patients with AF that contribute to the elevated risk of ischemic stroke.” – by Darlene Dobkowski
Disclosures: The authors and Chugh report no relevant financial disclosures.
Perspective
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Felix O. Sogade, MD, FACC, FHRS
The following are the comments which needs to be addressed, as this article may unwittingly be misconstrued that black individuals have a limited benefit from use of systemic anticoagulants to reduce AF-related strokes.
In this study, it was not stated whether the use of anticoagulants such warfarin vs. non-vitamin K antagonist oral anticoagulants are similar in the two groups compared. Since most of the strokes occurred before and early after diagnosis of AF, use of agents such as warfarin with a delayed onset of therapeutic advantage may not result in early protection of anticoagulant effects compared with non-vitamin K antagonist oral anticoagulants.
There is no mention of how the underlying arrhythmia of AF was treated. If black patients had a lower referral to ablations, this may have a significant impact on the outcomes beyond use of anticoagulants. Multiple studies have demonstrated the superiority of ablation procedures vs. medical therapy for management of AF.
The issue of black patients’ underrepresentation in all the pooled studies of non-vitamin K antagonist oral anticoagulants (approximately 2%, as reported in the article) still begs the question of whether black patients may be underdosed regarding use of non-vitamin K antagonist oral anticoagulants. The common formula for glomerular filtration rate calculation using the Cockcroft-Gault equation ascribes a higher GFR to black patients.
Risk factors associated with higher CHA2DS2-VASc score, hypertension, diabetes and chronic HF are more common in black patients. These may be contributing to ischemic stroke mechanisms unrelated to AF.
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