Diameters and segment relations during the cardiac cycle in the canine left ventricle.

The relations between left ventricular antero-posterior, septum-free wall diameters and an anterior subendocardial segment were studied by sonomicrometry in seven open-chest anesthetized dogs, during the control state and during left ventricular and right ventricular pressure overload for low and high left ventricular filling pressures. A linear relationship between antero-posterior and septal-free wall shortening was observed during control and during left ventricular pressure overload when left ventricular filling pressure was high. For low end-diastolic ventricular pressure, there was the same relationship during ejection with an isovolumic lengthening of the septal-free wall diameter. This relationship was shifted downwards during pulmonary artery stenosis for both high and low left ventricular filling pressure, which produced a significant decrease in end-diastolic septum-free wall diameter without significant modifications of end-diastolic antero-posterior diameter. The anterior segment exhibited behavior similar to that of the calculated left ventricular circumference. Subendocardial anterior segment measurements in the open-chest dog model can be used as indices of left ventricular circumference.