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Atrial Fibrillation Ablation in Women
Abstract & Commentary
By John P. DiMarco, MD, PhD
Source: Patel D, et al. Outcomes and complications of catheter ablation for atrial fibrillation in females. Heart Rhythm. 2010;7: 167-172.
In this paper, Patel et al, from five major ablation centers, report on the results of catheter ablation for atrial fibrillation in women. Between January 2005 and May 2008, 3,265 patients with atrial fibrillation underwent ablation at the five centers that participated in this report. Each center collected data prospectively, and then the data were merged for this study. Atrial fibrillation was classified as paroxysmal AF, persistent AF, and longstanding persistent AF. Procedural failure was defined as any episodes of atrial fibrillation or atrial tachycardia that lasted longer than one minute after an eight-week post-procedure blanking period.
The centers followed a fairly standard ablation protocol. One center maintained warfarin anticoagulation up until the time of the procedure, while the other centers used bridging with low-molecular weight heparin. The ablation strategy consisted of pulmonary vein antral isolation guided by a circular electrode catheter placed in each pulmonary vein. A 3.5 mm open-irrigation-tip catheter (ThermoCool) was used for ablation. The endpoint for ablation was elimination of all pulmonary vein potentials along the antra or inside the vein and exit block from the veins during spontaneous firing. Additional lesions could be placed along the superior vena cava if spontaneous activity was seen. For patients with persistent or longstanding persistent atrial fibrillation, additional ablation in the left and right atrium, at sites of fractionated electrical activity, was also performed. High-dose isoproterenol challenge was used to evaluate electrical disconnection and extra pulmonary vein-firing sites. After the procedure, patients were discharged on oral anticoagulation therapy. Low-molecular heparin was used for bridging, when needed. Patients received a cardiac-event monitor during the first five months after the ablation and were asked to transmit both routine recordings and a recording any time they experienced symptoms consistent with recurrent AF. Holter monitoring was performed at 3, 6, 9, and 12 months after ablation and every 3 to 6 months thereafter.
The overall study population included 2,747 men and 518 women. The women were slightly older than the men, with a mean age of 59 + 13 vs. 56 + 19 years. BMI values were similar, 28 for women and 27.3 for men. Women were more likely to have hypertension (55%) than men (40%), and men were more likely to have coronary artery disease (11.3% vs. 7%). A history of stroke was slightly more common among women(3.8% vs. 1.6%). More women had persistent or longstanding persistent atrial fibrillation (55%), compared to 45% among men. Women also had failed more antiarrhythmic drugs (4.1 + 1) than men (2.2 + 3). During the procedure, women had more non-pulmonary vein sites of firing than men (50.4% vs .16.3%). Success rates were lower in women than in men after 24 + 16 months of follow-up (68.5% vs. 77.5%, p < .001). Higher body mass index, nonparoxysmal forms of atrial fibrillation, and non-pulmonary vein triggers were predictors of procedural failure. Complications were also higher in women. Women had more hematomas (2.1% vs. 0.9%) and pseudoaneurysms (0.6% vs. 0.1%) than men. There were five deaths among women during the course of the study, but none were judged to be related to the procedure.
The authors conclude that catheter ablation has been more widely used in men than in women. They also noted somewhat lower procedural success rates and a higher risk of procedural complications than among men.
Women are less commonly referred for many types of invasive cardiac procedures. The authors cite studies showing that, even for an easily treatable disorder like AV node reentrant tachycardia ablation, women are referred later than men. The reasons for this aren't clear. In this study, women had a somewhat lower success rate and slightly more complications, but it doesn't seem that the differences are large enough to account for the substantial discrepancy. Since these were busy ablation centers, it's likely that much of the difference in referral rates is due to attitudes of referring internists and cardiologists, as well as differences in treatment preference of women vs. men.