Background: Although assessment of left ventricular (LV) regional work per unit of myocardium (RWM) from the wall stress-area relationship has been proposed using M-mode echocardiography, the applicable region was limited. Anatomical M-mode is a new technique which permits the M-mode cursor to be angled in any direction on digital two-dimensional images. Our objective was to characterize regional heterogeneity of LV myocardial work using anatomical M-mode.
Methods: Sixteen patients were studied: 5 with idiopathic dilated cardiomyopathy (DCM), 4 hypertrophic cardiomyopathy (HCM), and 7 controls. Digital 2-dimensional echocardiographic cineloops were acquired from the mid LV short-axis view simultaneously with high-fidelity LV pressure. Using anatomical M-mode, LV internal diameters and wall thickness (H) were determined to calculate mean wall stress (sigma) at 6 equiangular directions. The volume of region, which was given by area times H, was assumed to be constant throughout one cardiac cycle from the incompressibility of myocardium. Thus, 1/H is proportional to the regional area, and then RWM was determined as an area within the sigma-ln (1/H) loop at each direction (positive values indicated a counterclockwise loop rotation).
Results: RWM from controls were heterogeneous with the highest in the lateral segments. The 6-segment average RWM was lower in both patients with DCM and HCM than controls (3.9 +/- 1.7 and 2.1 +/- 0.3 vs. 5.5 +/- 1.4 mJ/cm(3), both p < 0.05). RWM was particularly deteriorated at septal and inferior segments in patients with DCM (2.3 +/- 0.9 and 3.0 +/- 1.5 mJ/cm(3), both p < 0.05 vs. control) and at hypertrophied anterior and anteroseptal segments in patients with HCM (0.4 +/- 0.1 and 0.8 +/- 0.6 mJ/cm(3), both p < 0.01 vs. control).
Conclusions: Anatomical M-mode enabled RWM assessment at all segments including the inferoseptum and lateral regions that had been impossible for analysis, revealing regional heterogeneity. The present method has the potential to provide additional information on myocardial mechanical condition.