HYPERKINETIC PULMONARY HYPERTENSION



Since pulmonary artery pressure is the product of pulmonary vascular resistance and cardiac out­put, any increase in pulmonary blood flow is in­variably associated with an increase in pulmonary artery pressure. If the increased flow is sustained,as in intracardiac shunts, anatomical changes occur in the pulmonary vessels (vascular remod­eling) which increase vascular resistance and fur­ther increase pulmonary artery pressure, causing the pulmonary hypertension to persist even after the initial stimulus is corrected. Remodeling con­sists initially of the muscularization and hyper­trophy of previously unmuscularized small arter­ies, followed by medial hypertrophy and intimal proliferation in the larger pulmonary arteries. Both of these changes are reversible if the pul­monary hypertension is reduced. However, per­sistently high pressures produce permanent ob­structive changes such as necrotizing arteritis and complex dilatations known as plexiform lesions.