Left ventricular geometry and function in Tanzanian patients with hypertension and diabetes

Abstract

From echocardiographic studies in hypertension, African Americans have been found to be more prone to develop cardiac target-organ damage than Caucasians. Hypertension is among the major upcoming health problems in Africa. However, there is a lack of knowledge about cardiac structural and functional changes in hypertension and diabetes in native sub-Saharan Africans. This thesis consists of 3 studies that aimed at determining the prevalence, covariates and functional consequences of abnormal left ventricular (LV) geometry in native Tanzanian patients with hypertension and diabetes attending out-patient clinics at Muhimbili National Hospital in Dar es Salaam, Tanzania. In study I, 161 untreated hypertensive patients, and 80 age- and sex-matched normotensive controls were studied. Studies II and III included 123 type 2 and 61 type 1 diabetic patients with about 10 years duration of diabetes. The prevalence of abnormal LV geometry was 77% in type 2 diabetic patients, 62.1% in untreated hypertensives, 40% in type 1 diabetic patients and 12.5% among the controls. Concentric LV hypertrophy was the most common abnormal LV geometric pattern in type 2 diabetes (in 47% of patients with abnormal LV geometry) and in untreated hypertensive patients (in 42% of patients with abnormal LV geometry), while concentric remodelling was the predominant type of abnormal LV geometry in type 1 diabetic patients (in 75% of patients with abnormal LV geometry) and in controls (90% of controls with abnormal LV geometry). Higher systolic blood pressure, obesity and impaired renal function were the main independent determinants of abnormal LV geometry both in patients with hypertension and in diabetes. Abnormal LV geometry was associated with subclinical LV myocardial systolic dysfunction both in hypertension and in diabetes, as well as subclinical LV diastolic dysfunction independent of clinical covariates. A risk score comprising key clinical variables in standard assessment of diabetic patients (type of diabetes, hypertension, obesity and abnormal albuminuria) was developed. This score demonstrated that presence of either hypertension, obesity or abnormal albuminuria in a patient with type 2 diabetes or presence of any 2 of these clinical variables in a type 1 diabetic patient identified 3 out of 4 diabetic patients with echocardiographic abnormal LV geometry (concentric remodelling or concentric LV hypertrophy, the main types of abnormal LV geometry in the diabetic patients). The ability of enlarged left atrial volume index (LAVI) to detect subclinical LV diastolic dysfunction in diabetic patients was tested, and was found to be a good indicator of LV diastolic dysfunction in type 2 diabetic patients while LAVI reflected early diabetic cardiomyopathy in type 1 diabetic patients. In conclusion, abnormal LV geometry is very prevalent in asymptomatic Tanzanian patients with hypertension and/or diabetes, increased by 4-6 folds compared to healthy controls, and is associated with subclinical LV systolic and diastolic dysfunction.