Event‐Recorder Monitoring in the Diagnosis of Atrial Fibrillation in Symptomatic Patients: Subanalysis of the SOPAT Trial

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Abstract
In the SOPAT (suppression of paroxysmal atrial tachyarrhythmias) trial, a high number of asymptomatic atrial fibrillation (AF) episodes were registered in patients with symptomatic AF. This subanalysis was performed to answer three questions: (1) Does antiarrhythmic therapy influence the ratio of symptomatic to asymptomatic AF? (2) Are symptoms during AF dependent on the heart rate (HR)? (3) Do symptoms correlate with an episode of AF? Within 60 months 1,033 patients with symptomatic AF were randomized to either quinidine plus verapamil (Q+V) 480/240 mg/day, Q+V 320/160 mg/day, sotalol 320 mg/day, or placebo, and followed up by daily and symptom-triggered ECG event recording. Over 188,634 ECGs were analyzed (87% SR, 7% AF). Symptoms were reported in only 46% of AF-ECGs. Quinidine plus verapamil reduced the ratio of symptomatic to asymptomatic AF, whereas sotalol had no effect (median [%] (25/75% quartile): Q+V 480/240: 33 (0/79), Q+V 320/160: 45 (1/82), sotalol: 56 (7/93), placebo: 63 (8/92)). The HR during AF directly correlates with the occurrence of symptoms (P < 0.001) and was significantly lower during asymptomatic AF in all groups (mean +/- SD: sympt.: 113 +/- 27/minute, asympt.: 103 +/- 27/minute, P < 0.001). Both antiarrhythmics reduced the mean HR compared to placebo (P < 0.001). Analyzing all symptom-triggered ECGs, AF was diagnosed in only 37%, whereas the majority were SR. Taken together, in contrast to sotalol, Q+V reduces the ratio of symptomatic to asymptomatic AF compared with placebo, at least in part by decreasing the heart rate. Furthermore, patients' symptoms are not a reliable surrogate parameter for the prevalence of AF.