MECHANISM OF IMPAIRED LEFT-VENTRICULAR WALL-MOTION IN THE DIABETIC HEART WITHOUT CORONARY-ARTERY DISEASE

OBJECTIVE - To elucidate whether impairment of the myocardial free fat ty acid (FFA) metabolism and small vessel abnormalities in the myocard ium are etiologic or contributory factors of myocardial dysfunction in patients with NIDDM without any significant coronary artery disease. RESEARCH DESIGN AND METHODS - We performed myocardial imaging with I-1 23-labeled beta-methyl-p-iodophenyl pentadecanoic acid (BMIPP), a bran ched analog of FFA, and dipyridamole-infusion (201)thallium scintigrap hy (Dip) in nine patients who demonstrated left ventricular wall motio n abnormalities without any significant coronary artery disease and in fifteen control cases. As an index of myocardial FFA metabolism, the heart-to-mediastinum count ratio (H/M) of BMIPP was calculated from th e mean count in the regions of interest at the heart and the upper med iastinum. RESULTS - Nine patients with reduced wall motion documented by left ventriculography (LVG) (hypokinetic group) demonstrated signif icantly lower BMIPP uptake (2.1 +/- 0.2, mean +/- SD) than fifteen pat ients with normal wall motion (normokinetic group) (2.3 +/- 0.2, P < 0 .05). Regional ventricular wall motion observed by LVG, regional BMIPP uptake, and regional redistribution phenomenon (RD) were evaluated fo r five regions of the left ventricle: anterior, septal, apical, latera l, and inferoposterior regions. Wall motion was abnormal in 24 out of 120 regions. Regional BMIPP uptake was reduced in 47 regions. RD in Di p was observed in 23 regions. In regional analysis, the existence of d efect in the BMIPP image showed significant correlation with wall moti on abnormality (P < 0.01), but there was no significant relationship b etween the RD in Dip and regional wall motion abnormality (P = 0.16). Myocardial biopsy specimens obtained from the right ventricle of 20 pa tients showed no pathologic changes, with the exception of two patient s. CONCLUSIONS - Our findings suggest that impairment of myocardial FF A metabolism rather than small vessel abnormalities in the myocardium is responsible for modest left ventricular dysfunction in patients wit h diabetes.