Assessment of cardiac autonomic functions by heart rate recovery indices in patients with myocardial bridge.

BACKGROUND Heart rate (HR) recovery (HRR) reflects autonomic activity and predicts cardiovascular events. The aim of this study was to assess HRR in patients with myocardial bridge (MB). METHODS Medical recordings of 93 patients with MB and appropriate age, compared to 78 sex-matched healthy subjects were analyzed. MB was diagnosed via coronary computed tomography angiography after a positive exercise stress test (EST). HRR indices were calculated by subtracting 1st (HRR1), 2nd (HRR2) and 3rd (HRR3) minute HR from the maximal HR during EST. RESULTS HRR1 (30.2 ± 13.3 bpm vs. 35.8 ± 10.4 bpm, p = 0.001) and HRR2 (52.3 ± 13.3 bpm vs. 57.1 ± 11.6 bpm, p = 0.013) were lower in patients with MB. In addition, HRR1 was lower in patients with left anterior descending (LAD) MB than non-LAD MB (28.5 ± 13.2 vs. 37.1 ± 11.4, p = 0.013). Presence of MB, deep MB, LAD MB and multi-vessel MB were predictors of HRR1 (p < 0.01 for all). In a multivariate analysis, LAD MB was the only significant independent predictor of HRR1 (b = -8.524, p = 0.009). CONCLUSIONS Patients with MB have impairment in HRR indices which is more pronounced among patients with LAD MB. Cardiac autonomic dysfunction in MB might be due to recurrent myocardial ischemia.