NEW YORK (Reuters Health) – African Americans are less likely to develop atrial fibrillation after isolated coronary artery bypass graft (CABG) surgery than European Americans, a new study confirms.

African Americans “characteristically come to CABG with more severe coronary disease and more comorbidity than do European Americans,” Dr. Joseph Lindsay, of Washington Hospital Center in Washington, D.C., noted in an e-mail to Reuters Health.

“It is, therefore, very interesting that, in the instance of atrial fibrillation, African Americans have less in population studies (i.e. chronic) and now acutely following cardiac surgery,” he said.

“It appears that there are real ethnic differences unrelated to socioeconomic factors. Thus, we are entitled to suspect that there is genetically determined susceptibility to atrial fibrillation,” Dr. Lindsay added.

The research team compared the incidence of new-onset atrial fibrillation in 2,312 African Americans and 6,054 European Americans who underwent isolated CABG from July 2000 to June 2007. After the surgery, 504 African Americans (22%) and 1,838 European Americans (30%) developed atrial fibrillation (P < 0.01).

The lower incidence of post-CABG atrial fibrillation in African Americans persisted after adjustment with logistic regression analysis for numerous baseline differences, the authors note. The adjusted incidence of atrial fibrillation in African Americans was roughly two-thirds of that in European Americans, they report in the American Journal of Cardiology.

A comparison of the propensity-matched African-American and European-American patients confirmed a lower incidence of postoperative new-onset atrial fibrillation in the African Americans (22% vs 29%; P < 0.01).

In their paper, Dr. Lindsay and colleagues point out that their findings are “remarkably consistent” with those of another recent study.

They also note that the lower incidence of post-CABG atrial fibrillation in African Americans occurred despite the greater prevalence of the risk factors for the arrhythmia found in population studies.

“At this point,” said Dr. Lindsay, “I don’t expect these observations will have a significant impact on clinical care. On the other hand, as (the Danish physicist) Niels Bohr once said, ‘How wonderful that we have met with a paradox. Now we have some real hope of making progress.’ It appears that there are real ethnic differences unrelated to socioeconomic factors. Thus, we are entitled to suspect that there is genetically determined susceptibility to atrial fibrillation,” Dr. Lindsay said.

Am J Cardiol 2011.