The relationship between heart rate recovery and brain natruretic Peptide in patients with chest discomfort: a study for relationship between heart rate recovery and pre-exercise, post-exercise levels of brain natruretic Peptide in patients with normal systolic function and chest discomfort

Background and Objectives

The correlation between brain natruretic peptide (BNP) level and cardiac autonomic function has been studied in type 2 diabetic patients. However, there is limited data from patients with normal systolic function. We evaluated the association between heart rate recovery (HRR) representing autonomic dysfunction and three plasma BNP levels: pre-exercise, post-exercise, and change during exercise in patients with normal systolic function.

Subjects and Methods

Subjects included 105 patients with chest pain and normal systolic function. HRR was defined as the difference between the peak heart rate and the rate measured two minutes after completion of a treadmill exercise test. We measured plasma BNP levels before exercise, 5 minutes after completion of exercise, and during exercise (absolute value of difference between pre- and post-exercise BNP levels).

Results

Patients with abnormal HRR values (≤24 beats for the first 2 minutes of HRR) had lower high-density lipoprotein, lower peak heart rates, and higher pre- and post-exercise BNP levels than patients with normal HRR values. The patients with coronary artery disease (CAD) had abnormal HRR. However, no significant differences were found between the two groups in terms of history of hypertension (HTN), diabetes, and peak systolic blood pressure (SBP) and diastolic blood pressure (DBP). HRR was significantly associated with pre-exercise BNP (r=-0.36, p=0.004) and post-exercise BNP (r=-0.27, p=0.006), but not BNP changes. Further, pre-exercise BNP levels showed a greater association with HRR than post-exercise BNP levels.

Conclusion

HRR is independently associated with pre-exercise and post-exercise BNP levels, even in patients with normal systolic function.

Metabolic syndrome is associated with delayed heart rate recovery after exercise

Heart rate (HR) recovery after exercise is a function of vagal reactivation, and its impairment is a predictor of overall mortality and adverse cardiovascular events. While metabolic syndrome is associated with sympathetic overactivity, little is known about the relationship between metabolic syndrome and HR recovery. A symptom-limited exercise stress test in healthy subjects (n=1, 434) was used to evaluate HR recovery. Metabolic syndrome was defined according to the National Cholesterol Education Program's Adult Treatment Panel III (NCEP ATP-III) criteria. Seventeen percent of subjects had > or =3 criteria for metabolic syndrome. HR recovery was lower in men than women and in smokers than nonsmokers. The subject with metabolic syndrome (vs. without) showed lower HR recovery (10.3+/-11.6 vs. 13.6+/-9.7 per minute) and higher resting HR (64.3+/-10.3 vs. 61.6+/-9.1 per minute). HR recovery correlated inversely to age (r=-0.25, p<0.0001), but not to resting HR or maximal oxygen uptake. Delayed HR recovery was associated with metabolic syndrome after an adjustment for age, sex, resting HR and smoking (p<0.01). Metabolic syn-drome is associated with impaired vagal reactivation. Adverse cardiovascular out-comes associated with metabolic syndrome may be mediated by the failure of vagal reactivation in addition to sympathetic overactivity.