β-Blocker Prophylaxis for Atrial Fibrillation After Coronary Artery Bypass Grafting in Patients With Sympathovagal Imbalance

Background Atrial fibrillation (AF) is the most common arrhythmia after coronary bypass grafting (CABG) resulting in a prolonged hospital stay and higher costs. The withdrawal of β-blocker and a sympathovagal imbalance were identified as risk factors for AF. Methods In our study we performed a measuring of standard deviation of all normal RR intervals (SDNN) among 142 consecutive patients with β-blocker therapy before CABG in order to identify a collective who had an increased risk due to a withdrawal of β-blocker medication. A sympathovagal imbalance was predefined as a SDNN below 30 ms. Patients were divided into four groups according to the results of SDNN and the continuous β-blocker therapy: group I: SDNN ≤ 30 ms or less and withdrawal of β-blocker therapy (26 patients); group II: SDNN ≤ 30 ms and continuously β-blocker therapy (33 patients); group III: SDNN > 30 ms and withdrawal of β-blocker therapy (40 patients); group IV: SDNN > 30 ms and continuous β-blocker therapy (43 patients). Results Atrial fibrillation occurred in 39 patients (27%) after surgery. Patients of group I showed a higher incidence of AF (14 of 26 patients, 54%) than patients of group II (7 of 33 patients, 21%; p < 0.009), patients of group III (8 of 40 patients, 20%; p < 0.004), or patients of group IV (10 of 43 patients, 23%; p < 0.01). We found a significantly higher incidence of diabetes mellitus (47 vs 14% of patients; p < 0.0001) in patients with a sympathovagal imbalance than patients with a SDNN above 30 ms. Conclusions The results of our study suggest a sympathovagal imbalance and withdrawal of a β-blocker therapy increase the risk of postoperative AF. A continuous β-blocker therapy reduces the risk especially in patients with a sympathovagal imbalance and should always be practiced.