Exercise-induced delayed onset of left ventricular early relaxation in association with coronary microcirculatory dysfunction in patients with diabetes mellitus

The initiation of ventricular diastole is an energy-dependent phase of cardiac cycle. Delayed onset of left ventricular (LV) relaxation has been proposed to identify myocardial ischemia. Diabetes mellitus (DM) is known to be associated with coronary microangiopathy, but its influence on LV early relaxation is not established.

Ninety-two subjects consisting of 70 DM patients without overt cardiac disease and 22 normal controls were evaluated. Using strain rate imaging, time from R-wave on the electrocardiogram to onset of LV relaxation (Tr) was measured at rest and peak exercise. Using myocardial contrast echocardiography, myocardial blood flow (MBF) was measured at rest and peak exercise, enabling MBF reserve. Tr at rest was similar between DM patients and controls, but Tr at peak exercise was significantly longer in DM patients than controls. MBF reserve was significantly reduced in DM patients compared with controls. There was a significant negative correlation between Tr at peak exercise and MBF reserve. In a multivariate analysis, MBF reserve was an independent determinant of Tr at peak exercise.

This study demonstrates that DM patients have exercise-induced delayed onset of LV relaxation in association with impaired coronary microcirculatory function in the absence of coexistent heart disease.