Studies on the Pathologic Physiology of Pulmonary Hypertension in Mitral Valvular Disease : Part 1. The Role of Sympathetic Nervous System on the Increment of Pulmonary Vascular Resistance

The relations of pulmonary hemodynamics and the urinary catecholamine were investigated in patients with elevated left atrial pressure, and also the effects of 100 per cent oxygen and sympathetic blocking agents, such as phentolamine and hexamethonium, on pulmonary circulation were studied. Noradrenaline and the ratio of noradrenaline to adrenaline were higher in mitral valvular disease compared with control subjects, and somewhat better correlation (r=0.62) was obtained between the ratio of noradrenaline to adrenaline and the pulmonary arteriolar resistance. Administration of sympathetic blocking agents and inhalation of 100 per cent oxygen were followed by the reduction in pulmonary arteriolar resistance, and the decrement was found to be remarkable in those with the higher control values. From these evidences it is concluded that the functional vasoconstriction due to the sympathetic hyperactivity can make an additional contribution to the pathogenesis of pulmonary hypertension in cases with elevated left atrial pressure.