Pulmonary venous hypertension or pulmonary hypertension due to left heart disease

Abstract

Pulmonary venous hypertension may be caused by increased pressure anywhere between the intraparenchymal pulmonary veins and the left ventricle. Pulmonary venous hypertension has different causes in children compared with adults. In adults the most common cause of pulmonary venous hypertension is left ventricular diastolic disease. In children, congenital heart diseases, acquired and congenital cardiomyopathies are the usual causes of pulmonary venous hypertension. There are three important mechanisms in the pathophysiology of pulmonary venous hypertension. Firstly there is a passive rise in pulmonary artery pressure as down stream pressure increases to maintain left sided preload and cardiac output. In this situation the transpulmonary gradient (< 10 mmHg) and pulmonary vascular resistance index are low (< 2.5–5 WU m 2) and the pulmonary artery diastolic pressure is similar to the left atrial, or in the absence of pulmonary vein or mitral valve pathology, the left ventricular end diastolic pressure. Secondly there is reflex vasoconstriction of the pulmonary arteries or veins or both and the diastolic pulmonary artery pressure will be higher than the pulmonary vein, left atrial or left ventricular end diastolic pressure depending on the site of the left sided pressure increase. The transpulmonary gradient will be > 10 mmHg and pulmonary vascular resistance index > 2.5–5 WU m 2. These patients respond to a cautious pulmonary vasodilator challenge with a decrease in both transpulmonary gradient and pulmonary vascular resistance index but with a variable increase in pulmonary venous pressure. Thirdly, there may be fixed pulmonary artery or vein obstruction. Quite often a combination of all three mechanisms (passive, reflex vasoconstriction and fixed) conspire to increase pulmonary artery pressure. Outside of restrictive cardiomyopathies, severe pulmonary hypertension due to isolated left ventricular diastolic disease is not prominent in young children. However, it seems likely that with the emergence of childhood obesity, insulin resistance, systemic hypertension, survivors of left sided congenital heart disease and organ transplantation that diastolic heart disease will assume more prominence in pediatrics. In general the pulmonary hypertension regresses if the left sided obstruction or dysfunction can be addressed adequately.