Effects of isolated right and left ventricular stretch on regional arteriolar resistance

Summary: In order to evaluate right and left ventricular stretch receptors without concomitantly stimulating those of the contralateral ventricle, 12 dogs were placed on total cardiopulmonary bypass. Balloons connected to compliant reservoirs were introduced into the right and left ventricles. Changes in systemic, gracilis muscle, and paw perfusion pressure at a constant flow were used as indices of systemic, muscle, and cutaneous vascular resistance. To induce left ventricular stretch, the balloon in that chanber was rapidly inflated from a mean pressure of 1.33 kPa (10 mmHg) to a mean pressure of 7.32 kPa (55 mmHg) for 15 s (6.00 kPa [45 mmHg] increment). For right ventricular stretch, the pressure was increased from 0.67 to 4.00 kPa (5 to 30 mmHg) for 30 s (3.34 kPa [25 mmHg] increment). Both left and right ventricular stretch produced a significant fall in systemic (-4.92 kPa [-37 mmHg], -36%) and gracilis muscle (-5.59 kPa [-42 mmHg],-30%) perfusion pressure, with only minimal changes in cutaneous vascular resistance (-0.80 kPa [-6 mmHg], -4%). This reflex was found to be vagally mediated, to have a low threshold for stimulation (left ventricle, 0.67 kPa [5 mmHg] increment; right ventricle, 1.33 kPa [10 mmHg] increment), and to have a neurogenic sympathetic alpha-adrenergic efferent limb. The low threshold for stimulation suggests that these reflexes may play a physiological role with changes in body position and may be important in such pathological conditions as semilunar valvular stenosis and myocardial infarction.