New-onset atrial fibrillation raises mortality risk, even among healthy middle-aged women with a low burden of cardiovascular disease, according to a report in the May 25 issue of JAMA.
However, the absolute excess in mortality attributable to atrial fibrillation (AF) is a "fairly low" 2% in this population, said Dr. David Conen of University Hospital Basel (Switzerland) and his associates.
To assess the risk of adverse events related to new-onset AF in a large cohort of patients with low cardiovascular risk, the investigators analyzed data from 34,722 subjects enrolled in the Women’s Health Study. The WHS furnished detailed medical information on female health care professionals who were aged 45 years and older at baseline in 1993 and were followed prospectively through 2010.
During a median follow-up of 15 years, 1,011 (2.9%) of these women developed new-onset AF. A total of 63 of these women died during the study period, including 4 (6.3%) who died within 30 days of receiving the diagnosis of AF.
"The age-adjusted relative risk of all-cause, cardiovascular, and noncardiovascular mortality was significantly higher among women with new-onset AF" than among those without AF, Dr. Conen and his colleagues said (JAMA 2011;305:2080-7).
The risk was "substantially higher shortly after AF diagnosis" and appeared to be related to the occurrence of nonfatal cardiovascular events – chiefly stroke, heart failure, and myocardial infarction – prior to death. This raises the possibility that "associated comorbidities at the time of AF diagnosis may be responsible for at least a portion of the excess death risk in these individuals," they said.
"As both [congestive heart failure] and stroke are at least partly preventable through blood pressure controls and anticoagulation, our data reinforce the importance of strict risk factor control in AF patients," the investigators noted.
Even though the increase in mortality risk was significant, the absolute excess in mortality was not high. "We estimated that after taking [CV risk factors] into account, approximately 2% of all deaths could be attributed to incident AF," they said.
In secondary analyses, they assessed mortality risks according to subtypes of AF.
The researchers found that cardiovascular mortality, but not total or noncardiovascular mortality, was significantly increased in the 65% of women who had paroxysmal AF. Although the number of events in this subgroup was small, "these data raise the possibility that individuals with paroxysmal AF may have a lower mortality risk than those with other AF patterns," Dr. Conen and his associates said.
In the subgroup of 74 women who had lone AF, none died or had a stroke during follow-up, and only 2 developed heart failure. "Although this represents the largest prospective sample of women with lone AF reported so far, the number is still too small and follow-up is not long enough to draw definite conclusions about long-term outcomes. Nevertheless, these data are consistent with prior observations that lone AF may be a benign disease, at least in the short term," they said.
The study was supported by the National Heart, Lung, and Blood Institute. The WHS was supported by the NHLBI and the National Cancer Institute. Dr. Conen and his associates reported ties to numerous industry sources.