Left ventricular wall thickness during the isovolumic relaxation period.

Left ventricular (LV) wall thickness was measured by echocardiography at the onset and at the end of the isovolumic relaxation period (IRP) in a group of normal young subjects. Measured LV minor diameter was constant during the IRP in these patients and there was no change in interventricular septal thickness. Posterior LV wall thickness increased by 12 +/- 6 (SD)% (P less than 0.001) and mean LV wall thickness by 6 +/- 4% (P less than 0.01). An increase in LV wall thickness during the IRP is consistent with simple fluid dynamic principles.