Cor pulmonale is a form of right-sided heart failure resulting from a primary disorder of the respiratory system, rather than a direct failure of the left side of the heart. This condition alters the structure and function of the heart’s right ventricle, which pumps deoxygenated blood to the lungs. The root cause is an underlying disease of the lungs, their blood vessels, or the mechanics of breathing that strains the right ventricle, leading to eventual failure. This article explores the distinct mechanisms that cause this heart-lung connection.
The Role of Pulmonary Hypertension
The development of Cor Pulmonale is linked to pulmonary hypertension (PH), which is abnormally high blood pressure within the arteries of the lungs. Pulmonary circulation is normally a low-pressure system. When a lung disorder causes chronic low oxygen levels (hypoxia), the body triggers a maladaptive reflex called hypoxic pulmonary vasoconstriction. This causes small pulmonary arteries to constrict, redirecting blood flow away from poorly ventilated areas.
Sustained hypoxia causes the artery walls to thicken and constrict, a process called vascular remodeling. This structural change narrows the vessels, leading to a permanent increase in resistance and pressure. The right ventricle must pump against this increased resistance, known as afterload. To compensate, the walls initially thicken (hypertrophy), but this sustained strain eventually causes the chamber to stretch and enlarge (dilate), resulting in heart failure.
Causes Stemming from Chronic Lung Damage
The most frequent causes of Cor Pulmonale involve diseases that chronically damage the lung’s air sacs and tissue structure, leading to persistent hypoxia.
Chronic Obstructive Pulmonary Disease (COPD)
COPD, including chronic bronchitis and emphysema, is the leading cause. Chronic bronchitis obstructs the airways, while emphysema destroys the air sacs and surrounding capillary bed. This widespread loss of blood vessels (capillary rarefaction) reduces the area for gas exchange and increases the resistance the right ventricle must pump against.
Interstitial Lung Diseases (ILDs)
ILDs, such as pulmonary fibrosis, cause scarring and stiffness in the interstitium, the tissue framework supporting the air sacs. This fibrosis makes the lungs rigid, impeding expansion and oxygen intake. It also physically obliterates the pulmonary capillaries embedded within the scarred tissue. The result is poor oxygen transfer and reduced vascular capacity, significantly elevating pulmonary artery pressure.
Other Inflammatory Conditions
Chronic inflammatory conditions like Cystic Fibrosis (CF) and severe Bronchiectasis also destroy lung tissue. Characterized by chronic infection, they cause progressive destruction of the airways and surrounding parenchyma. The resulting chronic alveolar hypoxia and structural damage combine to drive pulmonary hypertension.
Ventilation and Vascular System Causes
Causes of Cor Pulmonale not related to lung tissue destruction stem from issues with breathing mechanics or direct vascular blockage.
Sleep-Related Breathing Disorders
Obstructive Sleep Apnea (OSA) and Obesity Hypoventilation Syndrome (OHS) are sleep disorders that cause chronic intermittent hypoxia. Repeated drops in oxygen saturation overnight trigger a maladaptive response, causing pulmonary arteries to constrict repeatedly. Over time, this intermittent hypoxia leads to structural remodeling and fixed pulmonary hypertension.
Chronic Thromboembolic Pulmonary Hypertension (CTEPH)
CTEPH arises when blood clots from a prior pulmonary embolism fail to dissolve naturally. These persistent, organized clots physically obstruct the main pulmonary arteries. This mechanical blockage significantly raises pressure. The turbulent blood flow also triggers secondary small-vessel disease in the lung areas distal to the obstruction, compounding the pulmonary hypertension.
Restricted Chest Wall Movement
Conditions that restrict chest wall movement impair ventilation and cause chronic hypoxia. Neuromuscular diseases like amyotrophic lateral sclerosis (ALS) or muscular dystrophy weaken respiratory muscles. Severe skeletal deformities, such as kyphoscoliosis, physically compress the lungs. This restriction reduces lung capacity and chest wall compliance, leading to inadequate gas exchange, chronic low oxygen levels, and high carbon dioxide levels (hypercapnia). These factors ultimately trigger the pulmonary vasoconstriction that causes Cor Pulmonale.