Changes in regional myocardial blood flow and variable development of hypertrophy after aortic banding in puppies

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Abstract
Supravalvar aortic banding was performed in 6 to 12 week puppies. Sixteen animals were studied 7.3 (3.5 to 10) months later, closed-chested under morphine-chloralose, catheters being positioned in the great vessels and heart, including the left atrium for microsphere injection. Compared with 11 controls, eight dogs developed biventricular hypertrophy, four isolated left ventricular hypertrophy and four had no hypertrophy. The left ventricular systolic pressure was similar (P > 0.05) in these 3 banded groups (mean, 30 ± 2 |SEM] kPa, [222 ± 16 mmHg], n = 16|. The left ventricle was divided into three coronal slices with approximately 59 samples being taken from subendocardial, midwall, and subepicardial layers and additional samples from the atria and right ventricle for regional myocardial flow measurement. As left ventricular hypertrophy increased, the subendocardial/subepicardial flow ratio decreased (r = −0.8). Heterogeneity of left ventricular regional myocardial flow, including a base-to-apex decrease in flow, present in controls, was markedly reduced in the banded dogs. Analysis of variance was found to be the most sensitive test for detecting left ventricular perfusion abnormalities since in banded dogs without hypertrophy, total and regional subendocardial/subepicardial flow ratios were not significantly different from control values, whereas the subendocardial circumferential flow pattern determined by analysis of variance was significantly different from control in these dogs (P < 0.05).