Autonomic nervous system dysfunction and abnormal heart rate recovery

Abstract

The nervous autonomic system imbalance with a shift towards a sympathetic predominance is associated with an overall increased cardiovascular risk by elevated heart pressure, tachycardia and arrhythmias. Heart rate recovery (HRR) immediately after stopping the exercise stress test is considered as a reflection of the equilibrium between sympathetic and parasympathetic tone, focusing upon vagal reactivation. The aim of this study was to evaluate HRR after ergometer exercise testing as a marker of impaired autonomic balance and the possible correlation between a slow HRR and cardiovascular risk factors (smoking, diabetes, age, hypertension). We performed a retrospective analysis on 31 patients with abnormal heart rate recovery studying the possible influence of the most important cardiovascular risk factors: smoking, diabetes, obesity and hypertension as possible determinants for autonomic imbalance. There was no association found between the presence of the major risk factors with the DHR1, which only seems to be correlated with the maximal load of the stress test. When defining sub-groups with lower cut-off values for HRR and taking into consideration only the segment of age above 75, we have obtained several correlations with smoking status, diastolic blood pressure and obesity. Age is probably the most important determinant in our analysis, the older the patient the slower he will recover from the 3rd minute: smoking patients over 75–80 will have slower HRR from minute 2 and they will be less capable to reach higher maximal loads ( Table 1 , Fig. 1 ). Even though our study group is small, our findings still raise the question if we should be more strict when considering the HRR abnormality with a possible cut-off value of 8/9 for each of the minutes of recovery.