Correlation of Cardiac Sympathetic Nervous System Dysfunction with Diastolic Left Ventricular Dysfunction in Patients with Controlled Hypertension

Introduction: Sympathetic nervous system activity is increased in patients with systemic hypertension. Angiotensin converting enzyme inhibitors can effectively control hypertension without a reflex sympathetic stimulation. However, limited data are available about the role of sympathetic dysfunction in the   pathophysiology of diastolic dysfunction among patients with controlled hypertension receiving angiotensin converting enzyme inhibitors.Methods: Twenty four non-diabetic patients with controlled hypertension on angiotensin converting enzyme inhibitors without heart failure and not currently on β-blocker therapy were included in the study. Patients were divided into 2 groups based on diastolic function as defined by echocardiography, group A with diastolic dysfunction (10 subjects) and group B without diastolic dysfunction (14 subjects). Patients underwent ambulatory blood pressure monitoring for assessment of nocturnal blood pressure dip and 123I metaiodobenzylguanidine (123I-MIBG) imaging to determine heart to mediastinum ratio. Plasma norepinephrine levels were measured.Result: Patients with diastolic dysfunction had a higher level of plasma norepinephrine (0.46 vs 0.26 ng/ml, p=0.01) as compared to patients with normal diastolic function. There was no statistically significant difference in the early or late heart to mediastinum ratio (p=0.5) or the wash-out rate (p=0.9) among the two groups. There was no correlation between plasma norepinephrine and 123I-MIBG uptake. There was a statistically significant inverse correlation between E/A ratio and the log of plasma norepinephrine level (r= - 0.43, P=0.03).Conclusion: Localized cardiac autonomic dysfunction is not significantly worse in grade I diastolic dysfunction, compared to normal