Does coronary occlusion alter left ventricular wall thickness and shear motion in open-chest dogs?
A novel ultrasonic triangulation technique successfully documented true wall thickness dynamics and shear motion during and after coronary occlusion in a canine model.
We developed a new ultrasonic triangulation technique 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 three receiving crystals were sutured to the opposing epicardium at the corners of a 45-degree right triangle. By the trigonometric combination of three 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 SEM) 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 three-dimensional display of dimensions and thereby permit documentation of true wall thickness dynamics both during and after coronary occlusion.
Osakada et al. (Fri,) studied this question.