Angiotensin-receptor blockers (ARBs) should not be used to suppress paroxysmal atrial fibrillation (AF), according to results from a prospective study presented at the European Society of Cardiology Congress 2010.

Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting about 7 million people in Europe. It is a progressive chronic disease in which episodes become more frequent and long lasting over time. Conventional anti-arrhythmic therapy aims at halting progression and reducing symptoms, but the use of most anti-arrhythmic drugs is compromised by severe side effects, such as pro-arrhythmia or extra-cardiac organ toxicity.

A number of meta-analyses have shown that angiotensin II antagonists (ARBs) may reduce recurrence of AF, with an almost placebo-like tolerability. However, the available evidence from meta-analyses is heterogeneous with respect to the patient populations under investigation, the specific study designs, and the methods used to detect recurrent AF.

The ANTIPAF (ANgiotensin II anTagonists In Paroxysmal Atrial Fibrillation) trial was the first trial to prospectively evaluate the principal hypothesis that the angiotensin II receptor antagonist olmesartan suppresses episodes of paroxysmal AF. The primary endpoint of the trial was the percentage of days with documented episodes of paroxysmal AF throughout 12 months of follow-up. Secondary endpoints included the time to first occurrence of a documented relapse of AF, quality of life, time to first AF recurrence, time to persistent AF, and the number of hospitalizations.

Patients were stratified according to presence of beta-blocker therapy and randomized to placebo or olmesartan (40 mg/day). Concomitant therapy with ARBs, ACE inhibitors, and anti-arrhythmic drugs was prohibited. Patients were followed using daily trans-telephonic ECG recordings (at least one 1-minute ECG/day) independent of symptoms - and were encouraged to submit further tele-ECGs in any case of AF-related symptoms. Follow-up visits were scheduled after 3, 6, 9 and 12 months, which included long-term ECGs, transthoracic echocardiography, laboratory markers, and assessment of quality of life.

425 patients (at least 18 years old) with documented episodes of paroxysmal AF were included from 37 centers in Germany. A total of 87,818 tele-ECGs were analyzed during follow-up (44,888 ECGs in the placebo group and 42,930 ECGs in the olmesartan group). Thus, a mean of 207 tele-ECGs were recorded per patient with an average of 1.12 tele-ECGs per patient per day of follow-up.

The study demonstrated no significant difference in the burden of AF (primary endpoint) between both treatment groups. Further secondary outcome parameters such as quality of life, time to first AF recurrence, time to persistent AF, and the number of hospitalizations were also similar between groups. However, the time to prescription of recovery medication (amiodarone) was longer in patients treated with olmesartan than in those receiving placebo.

Commenting on the study results, principal investigator Professor Andreas Gotte from St. Vincenz Hospital, Paderborn, Germany, said: "In patients with AF and concomitant structural heart disease such as hypertensive heart disease or systolic heart failure, ARBs are effective adjunct therapies while being highly tolerable. ANTIPAF provides pivotal evidence, however, that ARBs do not reduce the number of AF episodes in patients with paroxysmal AF and without structural heart disease."

The ANTIPAF study was conducted by the German Competence Network on Atrial Fibrillation (AFNET), an interdisciplinary national research network funded by the German Federal Ministry of Education and Research.