MAASTRICHT, THE NETHERLANDS. There is still widespread denial among North American cardiologists as to the existence of vagally-mediated AF (atrial fibrillation) and a pronounced tendency to treat all AF patients the same. Hopefully, this will now change with the publication of the results of the Euro Heart Study. This study involved over 5000 AF patients treated in 182 hospitals in 25 different countries.
A total of 1517 of the patients experienced paroxysmal (intermittent) afib and was studied in detail. Among this group, 42% (640 patients) had a distinct, physician-verified, autonomic pattern as far as triggering an episode was concerned. Another 35% reported no clear trigger patterns, while in the remaining 23%; the physician did not verify the presence of triggers. The authors of the study classified the trigger pattern as vagal if episodes occurred after a meal or during the night, and as adrenergic if initiated by exercise or emotional stress. Afibbers with no clear trigger pattern were classified as mixed.
Sixteen percent of the group had lone AF defined as afib without the presence of hypertension, coronary artery disease, or heart failure. Somewhat surprisingly, the researchers found no difference in the incidence of heart disease among vagal and adrenergic afibbers. Among the group with clearly defined trigger patterns, 18% were classified as vagal, 46% as adrenergic, and the remaining 36% as mixed. (NOTE: The distribution in our most recent LAF survey was 30% vagal, 6% adrenergic, and 64% mixed).The major conclusions reached from the study are as follows:
- Exercise and emotional stress were the most common triggers followed by electrolyte imbalances, and alcohol and caffeine consumption.
- The majority (72%) of vagal afibbers received non-recommended drugs (beta-blockers, sotalol, digoxin or propafenone) – 57% were prescribed beta-blockers or sotalol.
- Vagal afibbers who were prescribed non-recommended drugs were more likely to progress to persistent or permanent AF than were vagal afibbers prescribed recommended drugs (primarily flecainide). After 1 year of follow-up, 19% of vagal afibbers prescribed non-recommended drugs had developed persistent or permanent afib as compared to 0% in the group prescribed correct drugs.
- Among adrenergic afibbers, 20% did not receive the medication recommended in the 2006 ACC/AHS/ESC Guidelines for the Management of Atrial Fibrillation. However, there was no indication that the type of medication affected progression to persistent or permanent in this group.
- Quality of care would appear to vary considerably between the regions in Europe. In the Mediterranean region 41% of patients received the recommended treatment as compared to 20% in Central Europe, and only 19% in Western Europe. Similarly, in the Mediterranean region physicians verified the presence of triggers in 75% of cases as compared to 79% in Central Europe and only 46% in Western Europe. Editor's comment: It would seem that afib care in Western Europe is substandard, but probably no worse than in North America.
- The authors point out that beta-blockers are often given in conjunction with class 1C antiarrhythmics (flecainide and propafenone) in order to prevent 1:1 conduction in the case of atrial flutter induced by the class 1C drug. They suggest that verapamil and diltiazem could be used as safer alternatives
The authors conclude, "Physicians do not seem to choose rhythm or rate control medication based upon autonomic trigger pattern of AF. However, the role of autonomic influences should be taken into consideration in order to achieve an optimal management of the disease as non-recommended treatment may result in aggravation of the arrhythmia."de Vos, CB, et al. Autonomic trigger patterns and anti-arrhythmic treatment of paroxysmal atrial fibrillation: data from the Euro Heart Survey. European Heart Journal, Vol. 29, 2008, pp. 632-39
Although not specifically directed at lone AF, this new European study is clearly a landmark and emphasizes the importance of determining trigger pattern (vagal, adrenergic or mixed) before prescribing medication for paroxysmal afibbers. It is interesting that our first LAF Survey (February 2001) revealed that 50% of vagal afibbers had been prescribed non-recommended drugs. This resulted in an average afib burden (# of episodes times their duration) more than twice as high than the burden among vagal afibbers taking flecainide or disopyramide. As far as propafenone (Rythmol) is concerned, the situation may not be as clear-cut as suggested in the Euro Heart Study. Some vagal afibbers have found this drug quite useful. Some fairly recent research have found that the degree of beta-blocking effect exhibited by propafenone depends markedly on how fast it is metabolized, so this may explain why it works for some vagal afibbers, while it is contraindicated in most others.