Physiological mechanisms of pulmonary hypertension

Pulmonary hypertension is usually related to obstruction of pulmonary blood flow at the level of the pulmonary arteries (eg, pulmonary embolus), pulmonary arterioles (idiopathic pulmonary hypertension), pulmonary veins (pulmonary venoocclusive disease) or mitral valve (mitral stenosis and regurgitation). Pulmonary hypertension is also observed in heart failure due to left ventricle myocardial diseases regardless of the ejection fraction. Pulmonary hypertension is often regarded as a passive response to the obstruction to pulmonary flow. We review established fluid dynamics and physiology and discuss the mechanisms underlying pulmonary hypertension. The important role that the right ventricle plays in the development and maintenance of pulmonary hypertension is discussed. We use principles of thermodynamics and discuss a potential common mechanism for a number of disease states, including pulmonary edema, through adding pressure energy to the pulmonary circulation.

The mechanism for the development of pulmonary hypertension associated with the different diseases processes is shown. Any distal obstruction or limitation to flow results in a greater pressure energy production by the right ventricle in an attempt to normalize both pulmonary and systemic flow. If right ventricular stroke volume exceeds left ventricular stroke volume, pulmonary edema results. The site of the flow limitation determines the clinical phenotype.Figure optionsDownload high-quality image (170 K)Download as PowerPoint slide