Determinants of myocardial and vascular function in young subjects with Type 1 diabetes mellitus

Cardiovascular disease including myocardial dysfunction and vascular disease is a major cause of morbidity and mortality among patients with type 1 diabetes mellitus. Early detection of myocardial dysfunction and identification of its determinants may be helpful in preventing diabetic heart muscle disease. In this thesis, I studied myocardial and vascular function in 53 subjects – 19 with type 1 diabetes mellitus (aged 21 ± 4 years, HbA1c 8.8 ± 1.6 %) and 34 controls (aged 25 ± 3). I measured myocardial functional reserve using myocardial velocity imaging during dobutamine in 18 patients and 21 controls. The main findings of this thesis were: 1. Longitudinal shortening of the left ventricle was reduced in type 1 diabetes mellitus. (medial mitral annular excursion 1.2±0.2 vs. 1.4±0.2 cm, p =0.01). 2. During dobutamine, long-axis peak systolic velocity was lower in type 1 diabetes by 20% at 10 and 13% at 20 μg/kg/minute (both p =0.05; ANOVA, p=0.003) but systolic velocities at peak dobutamine were similar and thus myocardial functional response was. 3. Longitudinal displacement was reduced in subjects with type 1 diabetes mellitus both at rest and during dobutamine stress. (by 15%, p =0.001). 4. Early diastolic relaxation was lower in type 1 diabetes, measured globally as the mitral E/A ratio (1.5±0.4 cm/s vs. 1.8±0.4 cm/s, p=0.02) or regionally as the early diastolic velocity of the medial mitral annulus (e’ -13.0±2.7 cm/s vs. -14.8±2.0 cm/s, p=0.02). 5. Features of adiposity and adverse lipid profiles, more than glycaemia, are major determinants also for myocardial and vascular dysfunction in young subjects with type 1 diabetes mellitus. In conclusion, there is evidence of myocardial dysfunction in young subjects with type 1 diabetes mellitus, and early changes may be related to metabolic rather than structural changes. Control of other risk factors such as dyslipidaemia, and maintenance of normal body weight, may be important measures in preventing progression of subclinical myocardial dysfunction into overt clinical disease