Cardiac Autonomic Impairment and Chronotropic Incompetence in Dipper and Nondipper Hypertension

Objective: The aim of the present study was to compare the autonomic nervous system activity indexes obtained from treadmill exercise stress testing in dipper and non-dipper hypertensive patients. Material and Methods: This study included 214 hypertensive patients, under antihypertensive medication. All study participants underwent 24-hour ambulatory blood pressure monitoring (ABPM) and maximal exercise testing. Thereafter patients were divided into two groups: 94 dipper hypertensives and 120 non-dipper hypertensives. Heart-rate (HR) response during exercise was evaluated by the chronotropic index (CI). HR recovery (HRR) was defined as the difference between HR at peak exercise and first minute after the exercise test. Results: Daytime systolic and diastolic BP measurements were similar, however night-time measurements were significantly lower among dippers than non-dippers (night-time systolic BP: 114.1±11.4 vs 126.3±15.0 mmHg, p<0.001; night-time diastolic BP: 72.3±7.3 vs 79.9±9.8 mmHg, p<0.001). Chronotropic index was lower than normal in both groups (0.79±0.1 vs 0.78±0.7 p=NS). Dippers had higher HRR values than non-dippers (31.8±4.6 vs 29.1±4.6 p<0,001). HRR was positively correlated with the percentage decline of systolic and diastolic BP from day to night (r=0.255 p<0.001 and r=0.228 p=0.001, respectively). There were no correlation between CI and percentage of systolic and diastolic BP reduction from day to night (r=0.067 p>0.05 and r=0.16 p>0.05, respectively). Conclusion: Hypertensive patients have abnormal HR response to exercise,. Non-dippers had lower HRR values than dippers. This may due to a relative general decrease of parasympathetic reactivation after exercise that is linked to the failure of nighttime fall of BP.