Effect of volume-overload hypertrophy on the coronary circulation in awake dogs

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Abstract
Inadequate coronary reserve is present in left ventricular hypertrophy secondary to hypertension. Since this abnormality might be due in part to vascular hypertrophy of coronary resistance vessels in response to chronic hypertension, we studied a model of ventricular hypertrophy without hypertension. Volume-overload hypertrophy was produced by creating complete heart block in mongrel dogs; 6 to 7 weeks later the dogs were studied in the awake state. The thirteen dogs with chronic heart block had a 49% increase (P−1·min·100 g, respectively). Minimal coronary vascular resistance of the entire left ventricle was significantly less in dogs with hypertrophy than controls (13.0±0.8 vs 17.3±1.7 kPa·litre−1·min, respectively). This data suggests that vascular hypertrophy of coronary resistance vessels related to chronic hypertension may be the cause of the increased minimal coronary vascular resistance seen in dogs with pressure-overload left ventricular hypertrophy.