Is abnormal adrenergic activation associated with abnormal Heart Rate Recovery?

BACKGROUND: Heart Rate Recovery (HRR) reflects the capacity of the cardiovascular system to reverse the vagal withdrawal caused by exercise. Scintigraphy with metaiodobenzylguanidine (I¹23 MIBG) evaluates innervation and cardiac adrenergic activation. The association of these two methods is not well established. OBJECTIVE: To evaluate the association between HRR and washout rate (WO) of I¹²³ MIBG in patients with heart failure (HF). METHODS: wenty-five patients with ejection fraction < 45% underwent exercise testing, and analysis of the variation of HRR from the 1st to the 8th minute after exertion. Submitted to I¹²³ MIBG, they were separated into groups by WO: G1) 27%. For the statistical analysis Mann-Whitney’s U test and Spearman’s correlation coefficient were used. RESULTS: G2 showed a slower variation of HRR: 1st minute: G1: 21.5 (16.12 to 26.87) vs. G2: 11.00 (8.5 to 13.5) bpm, p = 0.001; 2nd minute: G1: 34 (29-39) vs. G2: 20 (14 – 26) bpm, p = 0.001; 3rd minute: G1: 46 (37.8 – 54.1) vs. G2: 30 (22 – 38) bpm, p = 0.005; 5th minute: G1: 51.5 (42 – 61) vs. G2: 39 (31.5 to 46.5) bpm, p = 0.013, and in the 8th minute: G1: 54.5 (46.5 – 62.5) vs. G2: 43 (34 – 52) bpm, p = 0.037. HRR in the 1st (r = -0.555, p = 0.004), and in the 2nd minute (r = -0.550, p = 0.004) were negatively correlated with WO. CONCLUSION: Patients with high HF and WO showed an abnormal HRR compared with patients with normal WO. These findings suggest that adrenergic activation may influence the HRR.