REDWOOD CITY, CALIFORNIA. The most recent definitions for the duration-dependent types of atrial fibrillation (AF) are:
- Paroxysmal – episodes terminate spontaneously in less than one week (AF1)
- Persistent – episodes lasting more than one week but less than a year, or requiring electrical or pharmacological conversion within the first week following onset (AF2)
- Long-standing persistent – episodes lasting longer than one year (AF3). NOTE: This category was previously known as "permanent".
There is ample evidence that the success of catheter ablation is greater in the case of paroxysmal AF (AF1) than in the case of persistent (AF2), and that the poorest success rates are associated with long-standing persistent AF (AF3).
Now electrophysiologists at the Sequoia Hospital suggest that the persistent AF category may need to be split into two types – AF2a and AF2b. The AF2a category would relate to afibbers whose episodes are terminated in less than a week by electrical/pharmacologic means, while the AF2b category would encompass afibbers whose episodes last longer than one week but less than a year.
In order to investigate whether ablation outcomes vary between the two categories the Sequoia researchers evaluated the success rates in a group of 179 AF2a patients compared with a group of 244 AF2b patients. The average age of the patients was 62 years, 74% were male, and 15% had coronary artery disease. There were no significant differences between the two groups except for left atrial diameter, body mass index (BMI), and percentage with dilated cardiomyopathy, which were significantly higher in the AF2b group, and duration of AF which was significantly longer in the AF2b group (7.5 vs. 6.0 years). Members of group AF2a had also tried more pharmacological drugs in an effort to control their condition. The AF episodes in group AF2a were terminated by pharmacologic means (antiarrhythmics) in 25% of cases, many through the use of the pill-in-the-pocket approach, and by electro-cardioversion in the remainder. Propafenone (Rythmol) was the most common drug used in chemical conversion.
All study participants underwent a circumferential pulmonary vein isolation (PVI) procedure with additional lesions (including right atrial flutter ablation) as required. Freedom from AF was defined as no AF, flutter or tachycardia episodes lasting more than 30 seconds after a 3-month blanking period. NOTE: It is not clear whether patients who only managed to remain AF-free using previously ineffective antiarrhythmics were included as being AF-free.
Patients with AF continuing at 3 months or with late recurrences were encouraged to undergo repeat ablations and 125 patients did so. At the 1-year mark following the final ablation, 80.1% of the members of group AF2a were free of AF as compared to 72.9% in the AF2b group. Corresponding numbers at the 3-year mark were 75.1% and 64.1%. In comparison, the 1- and 3-year success rates for a group of 270 paroxysmal afibbers were 85.1% and 83.6% respectively. The researchers made the following interesting observations:
Winkle, RA, Patrawala, RA, et al. Relation of early termination of persistent atrial fibrillation by cardioversion or drugs to ablation outcomes. American Journal of Cardiology, May 18, 2011 [Epub ahead of print] Editor's comment
- Members of the AF2b group whose longest episode lasted from 1 week to 1 month had no better ablation outcome than did AF2b patients whose episodes lasted from 1 to 12 months.
- There was a linear correlation between the duration of the longest episode and left atrial diameter.
- Adverse atrial remodeling begins very quickly in persistent AF and the window to restore sinus rhythm to optimize AF ablation outcome may be less than one week.
- A longer duration of AF episodes such as found in the AF2b group is associated with greater body mass index and more cardiomyopathies suggesting that persistent AF can "make you fatter and wear out your heart".
: The above findings support the evidence that afibbers with long-lasting episodes and those with an enlarged left atrium will obtain better outcomes the sooner they undergo an ablation. The following remark made by the authors of the report supports my long-held belief that AF on its own is not a risk factor for stroke. It is the comorbid conditions that often accompany it that is the problem. "For determining thromboembolic risk, AF classifications have little value because thromboembolic risk is not related to type and/or duration of AF but instead to clinical factors such as congestive heart failure, hypertension, age, diabetes, or previous stroke."