Chronic Thromboembolic Pulmonary Hypertension

Excerpt

Chronic Thromboembolic Pulmonary Hypertension Overview

Chronic thromboembolic pulmonary hypertension (CTEPH) is a potentially life-threatening condition associated with high morbidity and mortality. However, advances in medical and surgical treatments have markedly improved the outcomes. CTEPH is a form of precapillary pulmonary hypertension associated with chronic thromboembolic disease. This condition falls under the World Health Organization's group 4 pulmonary hypertension classification.

Acute pulmonary embolism, particularly when coupled with additional risk factors such as prothrombotic tendencies, recurrent thromboembolic events, genetic predisposition, and patient characteristics like comorbidities, has the potential to evolve into chronic thromboembolic disease over time. Chronic thromboembolism can result in CTEPH. Overt right heart failure can ensue if this condition is untreated at advanced stages. Thus, a low threshold is necessary when monitoring at-risk individuals for the development of CTEPH. Untreated cases eventually lead to significant functional capacity limitations and premature death due to worsening hemodynamics.

Pulmonary Circulation

Understanding the anatomical features involved in CTEPH pathophysiology provides insights into how thromboembolic obstructions impact pulmonary hemodynamics, gas exchange, and right heart function. The pulmonary circulation involves the network of blood vessels transporting blood between the heart and lungs for oxygenation. This circulation begins at the right side of the heart. The right ventricle injects deoxygenated blood into the pulmonary arteries. The pulmonary arteries then branch into smaller vessels, eventually reaching the pulmonary capillaries within the lung parenchyma.

Gas exchange occurs in the pulmonary capillaries. Carbon dioxide is released from the capillary blood into the alveoli to be exhaled, while inhaled oxygen diffuses into the blood to be carried back to the heart. Once oxygenated, blood travels toward the left atrium via the pulmonary veins.

The pulmonary circulation is normally a low-pressure system compared to the systemic circulation. The right ventricle only needs to pump blood a short distance into the lungs' highly compliant blood vessels and back. This anatomy is well-adapted for efficient gas exchange, ensuring that blood is adequately oxygenated before systemic distribution. Additionally, the pulmonary vasculature is highly responsive to oxygen level changes, allowing for blood flow fine-tuning to match the body's metabolic demands.