Blacks more likely to have Atrial Fibrillation than previously thought?
Winston-Salem, NC - A new study has found that African Americans seem to have more abnormal values of atrial-fibrillation (AF) predictors on ECG than whites, which might help explain why they are at higher risk of ischemic stroke than whites, despite apparently having a lower prevalence of AF .
"The results raise the possibility that blacks might actually have a higher prevalence of AF than previously thought, that it might have been missed by prior studies owing to limited methodology," lead author Dr Elsayed Z Soliman (Wake Forest University School of Medicine, Winston-Salem, NC) told heartwire. He and his colleagues report their findings in the April 2009 issue of Stroke.
"There has been some sort of disconnect between the prevalence of AF and the prevalence of stroke in blacks," Soliman explained. "AF has been shown to be very low in blacks in many studies, but at the same time the stroke rate is high in blacks." Black patients suffer stroke five times more often than whites, and stroke mortality in blacks is twice that in whites, he noted.
He and his team believe that blacks may be more likely to suffer from intermittent, or paroxysmal, AF than whites. In such AF, the fibrillation pattern is intermittent and may not appear in a single ECG recording, so AF is not always detected. Most studies employ ECG or self-reporting to detect AF, Soliman notes, and as most cases of AF are asymptomatic, this can lead to underdiagnosis of the condition.
"Our research suggests that being proactive in predicting [AF] may be a better approach," he says.
Look for AF predictors on ECG, not AF itself, especially in blacks
In their study, Soliman et al reviewed ECG data from the Atherosclerosis Risk in Communities (ARIC) study with 15 429 participants, 27% of whom were black. They compared the distribution of baseline measures of P-wave terminal force, P-wave duration, P-wave area, and PR duration on ECG—referred to as AF predictors—by ethnicity and examined the association of these predictors with incident AF and ischemic stroke.
These AF predictors represent electrical activity in the atria of the heart, the source of thromboses that can cause stroke if AF occurs, the researchers explain.
They found that black ethnicity was significantly associated with abnormal AF predictors compared with whites; odds ratios for different AF predictors ranged from 2.1 to 3.1.
And AF predictors were significantly and independently associated with AF and ischemic stroke, with no significant interaction between ethnicity and AF predictors, findings that further justify using AF predictors as an early indicator of future risk of AF and stroke, they add.
"With the blacks having more abnormal ECG predictors of AF, as the results showed, there is a possibility that blacks might actually have a higher prevalence of AF than previous studies have picked up on," Soliman said.
Don't think AF is less common in blacks
"When physicians look at the ECG for AF, they perhaps don't need to look for AF itself, but they need to look for these predictors," Soliman told heartwire, adding that most cardiologists would be familiar with these markers for AF.
"For the physician evaluating black patients for the risk of stroke, these results show that you cannot think AF is less common in this population," he stressed.
However, he acknowledges that further research is needed and says the next step will be to perform a long-term ECG study to confirm the hypothesis that AF and especially intermittent AF have been underdiagnosed in blacks.
National Stroke Association’s mission is to reduce the incidence and impact of stroke by developing compelling education and programs focused on prevention, treatment, rehabilitation and support for all impacted by stroke.