IMPAIRED DIURNAL BLOOD PRESSURE AND HEART RATE VARIATION AND THEIR RELATIONSHIP WITH LEFT-VENTRICULAR FUNCTION IN ADOLESCENTS WITH TYPE 1 DIABETES MELLITUS

Abstract

INTRODUCTION: Diabetic cardiomyopathy is a well-defined complication of diabetes that occurs in the absence of ischemic heart disease or hypertension and has been associated with autonomic dysfunction. OBJECTIVE: Our aim was to evaluate diurnal blood pressure (BP) fluctuations and autonomic function and their possible association with left-ventricular function in adolescents with type 1 diabetes mellitus. METHODS: In 48 normotensive, normoalbuminuric diabetic adolescents, with a mean (±SD) age of 17.3 (±4.1) years and diabetes duration of 8.5 (±3.3) years, 24-hour ambulatory BP and heart rate (HR) monitoring was performed. Left-ventricular end-diastolic and end-systolic diameters were estimated by echocardiography, and left-ventricular mass index (LVMI) was calculated. RESULTS: The patients were divided into 2 groups according to the absence of decrease (nondippers) or the decrease (dippers) of nocturnal diastolic BP. The nondippers presented, in comparison with the dippers, reduced mean HR during 24 hours (79.6 vs 84.0 beats/minute; P = .05) and also during daytime (81.3 vs 86.0 beats/minute; P = .05). The nondippers also presented greater end-systolic diameter (28.7 vs 25.9 mm; P = .001) and left-ventricular end-diastolic diameter (47.8 vs 45.1 mm; P = .040) and greater LVMI (90.2 vs 78.3 g/m2; P = .044) compared with the dippers. During stepwise multiple regression, the most important factors affecting LVMI were mean HR (day) (b = −0.40; P = .001), high-frequency variable of heart rate variability (b = 0.38; P = .016), and hemoglobin A1c: (b = 0.67; P = .001). CONCLUSIONS: A group of normotensive diabetic adolescents with abnormal nocturnal BP reduction and impaired heart rate variation also had impaired left-ventricular function. Our findings suggest that an altered diurnal BP profile, as a result of autonomic dysfunction, may contribute to the development of left-ventricular hypertrophy in patients with type 1 diabetes mellitus.