The analysis of left ventricular wall thickness and shear by an ultrasonic triangulation technique in the dog.

Abstract

A new ultrasonic triangulation technique was developed to measure regional wall thickness and shear motion of the left ventricular wall under normal conditions and during complete and partial coronary occlusions. In 10 open-chest dogs, a left ventricular micromanometer was inserted, and a screw-driven arterial clamp and flowmeter were placed around the left circumflex coronary artery. A single miniature ultrasonic crystal was placed in the subendocardium of the left ventricular free wall in a region to be made ischemic, and 3 receiving crystals were sutured to the opposing epicardium at the corners of a 45.degree. right triangle. By the trigonometric combination of 3 measured lengths from ultrasonic dimension gauges, the exact position of the endocardial crystal in X, Y and Z coordinates could be displayed by computer. The endocardial surface moved in a longitudinal direction relative to the epicardial surface during normal systole [0.58 .+-. 0.26 (mean .+-. standard error of the mean) mm]. With coronary occlusion this myocardial shear became less marked (0.11 .+-. 0.12 mm) and systolic wall thickening changed to thinning. When coronary occlusion was released end-diastolic wall thickness and percent wall thickening rapidly increased to 104.8% and 141.7% of control, respectively, concurrent with the reactive hyperemia. With partial coronary constriction, these postreperfusion changes were markedly reduced, suggesting a role for reactive hyperemia in postreperfusion wall thickness dynamics. These techniques allow measurement of shear and 3-dimensional display of dimensions and permit documentation of true wall thickness dynamics during and after coronary occlusion.