Assessment of left ventricular function by meridional and circumferential end-systolic stress/minor-axis shortening relations in dilated cardiomyopathy
Ventricular Dysfunction, Left
Echocardiographic meridional wall stress-endocardial shortening relations provide estimates of left ventricular (LV) contractility that do not uniformly detect myocardial dysfunction despite severe symptoms in dilated cardiomyopathy. To improve detection of myocardial dysfunction in patients with congestive heart failure (CHF) due to dilated cardiomyopathy, echocardiographic meridional and circumferential end-systolic stress were related to endocardial and midwall shortening in 42 patients (95% dead within a mean of 22 months) with dilated cardiomyopathy and 140 normal subjects. A method to estimate LV long-axis dimension from M-mode minor-axis epicardial measurements was developed in a separate series of 115 subjects. Endocardial shortening to meridional wall stress relation identified 31 of 42 CHF patients falling below the 95% normal confidence interval of the reference population; use of midwall shortening decreased this number to 26 (p = NS). The use of circumferential wall stress identified 39 of 42 patients with subnormal endocardial LV shortening and 41 of 42 patients with depressed midwall performance (p < 0.01 vs use of meridional stress). The circumferential/meridional wall stress ratio was 2.6 +/- 0.5 in normal subjects and 1.3 +/- 0.2 in CHF patients (p < 0.0001). Thus, use of circumferential end-systolic stress as the measure of afterload improves the detection of myocardial dysfunction by stress/shortening relations in patients with CHF. The ratio between the 2 stresses decreases with more spherical LV shape. Midwall and endocardial shortening measurements are equivalent in the setting of thin LV walls as occurs in dilated cardiomyopathy.