Increases in Central Aortic Impedance Precede Alterations in Arterial Stiffness Measures in Type 1 Diabetes Mellitus

Objective: Increased pulse pressure (PP) has been associated with increased cardiovascular risk in persons with diabetes. Changes in central aortic properties can increase central PP and may adversely affect microvascular perfusion and cardiac performance. This study was performed to define early changes in central arterial properties in a group of young persons with type 1 diabetes mellitus (T1DM). Research and Design Methods: Seventeen persons with type 1 diabetes mellitus and their non-diabetic controls who were participating in the Cardio-Diab Study had arterial stiffness and pulsatile hemodynamics measured using calibrated tonometry and pulsed Doppler. Aortic characteristic impedance (Zc) was calculated from the ratio of change in carotid pressure and aortic flow in early systole. Pulse wave velocity was assessed from tonometry and body surface measurements. Results: Mean duration of T1DM was 15.3±0.7 years. In T1DM, central PP was elevated (45±11 vs. 36±10 mmHg in controls, p=0.02), as was peripheral PP (54±13 vs. 43±10 mmHg, p=0.002). Zc was elevated in T1DM (179±57 vs. 136±42 dynes x sec/cm in controls, p=0.004) whereas pulse wave velocity was not different (5.9±0.9 m/s in T1DM vs. 5.9±0.7 ms/ in controls, p=NS). There was a moderate correlation between Zc and urinary albumin excretion (coefficient = 0.39, p = 0.02). Conclusions: Zc appears to be increased early in T1DM, prior to elevation of pulse wave velocity, and is associated with higher PP, which may contribute to renal microvascular damage in diabetes.