Response to brief coronary stenosis in conscious dogs after ventricular sympathectomy.

Left ventricular responses to 2-min circumflex occlusion were studied in conscious dogs. In nonsympathectomized controls at 2, 4, and 8 wk after surgery for cardiac instrumentation, segmental shortening in the posterior ventricle significantly decreased by 111, 87, and 81% of the preocclusion values, respectively (P less than 0.05). The decrease in shortening was associated with increases in end-diastolic pressure of 9, 9, and 8 mmHg (P less than 0.05), decreases in the maximal rate of pressure generation of 305, 272, and 340 mmHg/s (P less than 0.05), and increases in heart rate of 28, 21, and 20 beats/min, respectively (P less than 0.05). After 2 and 4 wk of ventricular sympathectomy, posterior segmental shortening declined by 38 and 31%, respectively (P less than 0.05), but these decreases were less than in controls (P less than 0.05). Shortening did not change during occlusion after 8 wk of sympathectomy. Diastolic pressure increased by 6 mmHg (P less than 0.05), and the rate of pressure generation decreased by 232 mmHg/s (P less than 0.05) in the 2-wk sympathectomized ventricle. These variables did not change significantly after 4 and 8 wk of sympathectomy. After 2, 4, and 8 wk of sympathectomy, the increases in heart rate during circumflex occlusion were not different from controls (P greater than 0.05). Thus chronic sympathectomy preserved ventricular function during occlusion. This effect was attributable to a reduced preocclusion mechanical performance with a reduction in blood flow requirement and to an increased collateral perfusion, as indicated by a higher peripheral coronary pressure during occlusion in sympathectomized ventricles.