Key result
Endogenous Cushing's syndrome is linked to ~2.2-fold higher LF/HF ratio versus matched controls.
Why the study?
Endogenous Cushing's syndrome carries a higher risk of cardiovascular morbidity and mortality, and hypercortisolism may alter autonomic control of cardiovascular function, prompting investigation into the impact of chronic endogenous hypercortisolism on cardiac autonomic regulation using short-term heart rate variability analysis.
Case-Control (n=38)
May indicate autonomic imbalance in Cushing's syndrome; case-control data leaves open prospective validation for cardiovascular risk stratification.
BACKGROUND/AIMS: Endogenous Cushing's syndrome is associated with a higher risk of cardiovascular morbidity and mortality. Previous literature suggested multiple possible links by which hypercortisolism may alter the autonomic control of cardiovascular functions. We investigated the impact of chronic endogenous hypercortisolism on the autonomic regulation of cardiac functions by short-term heart rate variability analysis. METHODS: Eighteen patients with endogenous Cushing's syndrome and 20 age-, gender- and BMI-matched controls participated in the study. ECG signal was acquired in lead II configuration for 5 min and heart rate variability assessment was made in both time and frequency domain using the extracted RR interval data. RESULTS: All time and frequency domain measures of heart rate variability were significantly (p < 0.05) lower in the patient group compared to the control group. The patient group had an altered sympathovagal balance with low frequency/high frequency band ratio significantly higher than the control group [1.857 (0.6747-2.610) vs. 0.8581 (0.4779-1.352); p = 0.0253]. A significant negative correlation was obtained between normalized high frequency power of heart rate variability and basal cortisol levels (r = -0.6594; p = 0.0029). Multiple linear regression analysis identified age, disease duration (in months), basal cortisol levels and systolic blood pressure as independent predictors of normalized high frequency power. CONCLUSION: Findings of the study clearly portrayed the diminished autonomic modulation of heart rate in endogenous Cushing's syndrome and its possible relationship with hypercortisolism as the main causative factor. Diminished heart rate variability may be an indicator of the increased risk of cardiac mortality in these patients.
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Chandran et al. (2012) conducted a case-control in Endogenous Cushing's syndrome (n=38). Endogenous Cushing's syndrome (chronic endogenous hypercortisolism) vs. Age-, gender-, and BMI-matched controls was evaluated on Low frequency/high frequency (LF/HF) band ratio of heart rate variability (p=0.0253). Endogenous Cushing's syndrome was associated with lower HRV (p<0.05) and a higher LF/HF ratio compared to matched controls (1.857 vs. 0.8581; p=0.0253).
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