TAMPA, FLORIDA. Surveys of lone afibbers generally find that the ratio of men to women is about 80:20. It is by no means clear why this is indeed the case, but the proportion of afib induced by sustained, vigorous endurance exercise would likely be higher among men. If all cases of atrial fibrillation (AF) are considered, including those involving heart disease, men have a 50% higher risk of developing AF than do women. The overall prevalence of AF is, however, higher among women because they tend to outlive men.

Other significant differences between men and women when it comes to arrhythmias and the heart in general were summarized in a study carried out by cardiologists at the University of South Florida. Among the highlights are:

• The average resting heart rate in women is about 3-5 bpm faster than in men. This may be due to an intrinsic difference in the sinus node.
• Women have longer QT (corrected) intervals than men. NOTE: The QT interval is the duration of the activation (contraction) and recovery of the ventricular myocardium. A prolonged QT interval is associated with ventricular arrhythmias.
• Women are more likely to suffer from supraventricular tachycardia (SVT). Research has shown that SVT episodes are more common during the luteal phase of the menstrual cycle when progesterone levels are elevated. Inappropriate sinus tachycardia (inappropriately high heart rate at rest [over 100 bpm] and during stress) is also more common among women and is thought to involve abnormal autonomic regulation of the sinus node. Editor's comment: Inappropriate sinus tachycardia is also fairly common after an ablation, perhaps indicating that an ablation can result in a temporary, abnormal regulation of the sinus node.
• Women with AF are more likely than men to suffer an embolic stroke; however, they are also more likely to experience a major bleeding event if taking warfarin, so stroke prevention in women is particularly challenging. Women with paroxysmal AF tend to have longer episodes and a higher average heart rate during an episode.
• Pulmonary vein isolation (ablation) procedures are equally effective in men and women.
• Women are more likely to experience Torsades de Pointes (a distinctive form of ventricular tachycardia associated with a prolonged QT interval). This means that class 1C antiarrhythmics (flecainide and propafenone) are the preferred antiarrhythmics for women since they do not increase the QT interval. Amiodarone, sotalol, dofetilide and disopyramide may, on the other hand, increase the QT interval and should be used with caution in women.
• In the United States sudden cardiac death (SCD) claims between 300,000 and 400,000 victims every year. The incidence among women is only half of that among men and occurs 10-20 years later in life.
• The risk of SVT increases during pregnancy and during the post-partum period.

The Florida researchers conclude that there are important differences in the presentation and clinical course "of many cardiovascular disorders in men and women. It is important for health care providers to be aware of these differences to provide optimal care for their patients".

Yarnoz, MJ and Curtis, AB. More reasons why men and women are not the same (gender differences in electrophysiology and arrhythmias). American Journal of Cardiology, Vol. 101, 2008, pp. 1291-96