Atrial fibrillation - also known as AFib or AF - is the most common form of heart arrhythmia, where the heartbeat is irregular, too slow, or too fast.
Atrial fibrillation - also known as AFib or AF - is the most common form of heart arrhythmia, where the heartbeat is irregular, too slow, or too fast. It can occur in brief episodes or it can be permanent.
Because AF causes their beating to be irregular, blood flow from the upper chambers of the heart (the atria) to the lower chambers (the ventricles) is not as good as it should be.
The risk of having a stroke is four to five times higher in a person with AF, compared with a person without AF. Also, strokes in AF patients tend to be more severe.
While AF is a growing and costly public health problem, and much research has been published on the condition, we know little about sex differences in symptoms and how they may affect quality of life, treatment, and outcomes.
In the journal JAMA Cardiology, Jonathan P. Piccini, a clinical cardiac electrophysiologist and professor of medicine at Duke University Medical Center in Durham, NC, and colleagues describe how they investigated these outstanding questions.
Despite worse outcomes, women had better overall survival
For their observational study, the researchers used data on 10,135 patients with incident and prevalent AF that were enrolled in the Outcomes Registry for Better Informed Treatment of Atrial Fibrillation (ORBIT-AF) during June 2010-August 2011. The patients were enrolled as outpatients at 176 sites across the United States.
- An estimated 2.7-6.1 million people in the US have AF
- This number is expected to rise as the population ages
- Some people with AF do not experience any symptoms and do not know they have it.
Overall, 42 percent (4,293) of the patients were women, who on average were older than the men (77 and 73 years, respectively). The researcher note that they found four main differences between men and women:
- Women had more symptoms, more functional impairment, and worse quality of life - despite having less persistent forms of AF
- Women were more likely to undergo a procedure called atrioventricular node ablation
- Women had a higher risk for stroke or systemic embolism
- Despite these worse outcomes, women experienced a better overall survival.
Atrioventricular node ablation is a procedure where the atrioventricular node - the electrical pathway that links the top chambers to the bottom chambers of the heart - is removed. This is performed in patients with AF when medications do not work to control rapid heart rate.
The researchers suggest that:
"The reasons for this stroke-survival paradox may have important implications for AF-directed therapies in women and men."
In an accompanying commentary, Rod S. Passman, professor in medicine-cardiology and preventive medicine at Northwestern University Feinberg School of Medicine in Chicago, IL, notes that while registries can do much to help us understand how medicine is practiced, "they also have significant limitations that cannot be ignored."
For example, Prof. Passman notes that "unlike clinical trials where randomization attempts to ensure that treatment arms are comparable," an observational study that follows what happens to patients in a registry has to go with what the registry has to offer. Thus, the "baseline differences in a registry may allow for residual or unmeasured confounders that cannot be fully accounted for with statistical methods."
Another point he makes is that data completeness and follow up may also be a problem, and in the case of this study, health status data was not available for all patients. Less than half who gave health-related quality of life information at the start of the study period did so again at the end - 2 years later.
He implies that the value of this observational study is that it establishes a good beginning, by raising questions that should be researched further, rather than definite answers.
"Overall, patient registries can demonstrate what issues are worthy of future exploration, but the findings are usually more hypothesis generating than definitive."
Prof. Rod S. Passman
Meanwhile, the authors conclude that future studies "should focus on how treatment and interventions specifically affect AF-related quality of life and cardiovascular outcomes in women."