CARDIAC CONTRACTILITY IN NONINSULIN-DEPENDENT DIABETES-MELLITUS EVALUATED USING THE RELATION BETWEEN ENDSYSTOLIC WALL STRESS AND VELOCITY OF CIRCUMFERENTIAL FIBER SHORTENING

The relation between left ventricular (LV) endsystolic wall stress (si gma es) and rate-corrected velocity of circumferential fiber shortenin g (Vcf(c)), which is independent of heart rate (HR) and loading condit ions has previously been used to assess cardiac contractility in insul in dependent diabetes mellitus (IDDM). This study is the first report in which this relation has been utilized with data obtained by echocar diography in addition to the traditional indices, to evaluate the card iac function in asymptomatic, middle-aged patients with noninsulin dep endent diabetes mellitus (NIDDM) at baseline and during dobutamine sti mulation. There were 16 NIDDM patients in our study and these patients were classified into 2 groups. Group 1 consisted of 11 patients witho ut microvascular complications. Group 2 consisted of the remaining 5 p atients with microvascular complications. Ten age- and sex-matched nor mal subjects were enrolled as a control group. At baseline, diabetic p atients tended to have a faster HR and a greater LV enddiastolic dimen sion, though these values were not significantly different from the no rmal subjects. Ejection fraction (EF) in group 1 was significantly hig her than that of the normal controls (73 +/- 2% vs 65 +/- 2%, p < 0.00 5). Mitral inflow pattern was normal (E/A > 1) in the normal subjects (1.11 +/- 0.06), but reversed in group 1 (0.87 +/- 0.07) and group 2 ( 0.95 +/- 0.12). Isovolumic relaxation time corrected for HR (IVRTc) an d the slope of relation between sigma es and Vcf(c) were similar among the 3 groups. Comparing Vcf(c) at 50 g/cm(2) of sigma es, it tended t o increase from the normal subjects (0.883 +/- 0.057 circ/sec) to 0.96 9 +/- 0.048 in group 1 and 1.034 +/- 0.101 in group 2, though this res ult was not statistically significant. During dobutamine stimulation, EF increased and IVRTc shortened significantly only in the normal subj ects. E/A became normalized in both diabetic groups. The increment in Vcf(c) representing cardiac reserve of contractility was significantly lower in the diabetics (0.110 +/- 0.040 in group 1 and 0.057 +/- 0.04 3 in group 2) than in normal subjects (0.244 +/- 0.044). In conclusion , using the index of relation between sigma es and Vcf(c), the cardiac contractility of NIDDM was not impaired at baseline, and even had a t endency to increase. However, during dobutamine stimulation, the inade quate reserve of contractility was exposed, especially in those patien ts who had microvascular complications. These results indicate the imp ortance of controlling diabetes, not only to prevent the development o f microvascular complications but also to preserve cardiac function.