Pulmonary hypertension. Etiology, types. Cor pulmonale. Right ventricle and pulmonary vessel microscopic & gross pathomorphology
Cor pulmonale is shorthand for pulmonary hypertensive heart. It consists of right ventricular hypertrophy and dilation, often accompanied with right heart failure. It is exclusively caused by pulmonary hypertension.
Pulmonary hypertension is defined as pulmonary arterial pressure exceeding 25 mm Hg at rest or 30 mmHg in exercise. This increased pressure means the right side of the heart has to work harder, causing hypertrophy, and there is a build up of blood in the R side of the heart, causing dilation. It is caused by a number of conditions that affect the lung or the left side of the heart, etiological causes include:
- WHO group I - pulmonary arterial hypertension
- Idiopathic
- Heritable
- Drug toxicity
- CT disease, HIV infection, portal hypertension, congenital disorders
- WHO group I’ - pulmonary veno-occlusive disease, pulmonary capillary hemangiomatosis
- WHO group I’’ - persistent pulmonary hypertension of the newborn
- WHO group II - pulmonary hypertension secondary to left heart disease
- L systolic/diastolic dysfunction
- Valvular heart disease
- Congenital disease
- WHO group III - pulmonary hypertension due to lung disease
- COPD
- Interstitial lung disease
- Sleep apnea
- Bronchiectasis
- WHO group IV - chronic arterial obstruction
- Chronic thromboembolic pulmonary hypertension
The pathogenesis should be clear. In Lung disease causes we have increased resistance, in heart causes we have increased back-pressure or volume of blood, we know these cause hypertension.
Pathology of vessels/lungs
- Features characteristic of pulmonary hypertensive vascular remodeling include:
- Increased vascular stiffening of proximal pulmonary arteries
- intima/medial thickening of arteries
- Development of vaso-occlusive lesions
- Increased smooth muscle proliferation
Remember: in severe pulmonary arterial hypertension (especially idiopathic and heritable forms, often with BMPR2 mutations) small arteries show plexiform lesions: a tuft of capillary channels inside a dilated, thin-walled artery. The main pulmonary arteries may develop atheromas, which normally never form in the pulmonary circulation.
In the below image we can see arteries in pulmonary hypertension with thickened walls.
- When we consider the gross morphology, we should take particular note of the lungs which become heavy, fluid filled, and sometimes frothy, due to the congestion of blood that occurs in pulmonary hypertension due to left heart failure.
Right ventricular pathology
- The key change here is the hypertrophy of the myocardium of the right ventricle, as is visible on the image below, along with right ventricular dilation.