Pulmonary artery

The pulmonary artery is the only artery in the postnatal body that carries deoxygenated blood. All other arteries carry oxygenated blood from the left heart to the body's tissues. The pulmonary artery carries venous blood from the right ventricle to the pulmonary capillary beds of the lungs, where carbon dioxide is exchanged for oxygen before the blood returns via the pulmonary veins to the left heart.

A pulmonary embolism (PE) occurs when a blood clot—most often originating in the deep veins of the legs (deep vein thrombosis)—breaks free and lodges in the pulmonary artery or one of its branches, obstructing blood flow to part of the lung. A massive PE blocking the main pulmonary artery can cause acute right heart failure and circulatory collapse because the right ventricle cannot pump blood against the obstruction, leading to cardiac arrest.

Pulmonary hypertension is elevated blood pressure within the pulmonary arterial system, defined as a mean pulmonary arterial pressure exceeding 25 mmHg at rest. It increases the workload on the right ventricle, eventually causing right ventricular hypertrophy and failure (cor pulmonale). Causes include left heart disease, lung disease, chronic thromboembolic disease, and idiopathic forms. Symptoms include progressive dyspnea, fatigue, and right heart failure signs.

A Swan-Ganz catheter (pulmonary artery catheter) is a specialized hemodynamic monitoring device introduced through a central vein and floated through the right heart into the pulmonary artery using an inflatable balloon at its tip. It measures pulmonary artery pressure, pulmonary capillary wedge pressure (an indirect measure of left atrial pressure), and cardiac output, providing detailed information about heart function in critically ill patients.

In fetal life, the pulmonary artery is connected to the aorta via the ductus arteriosus, allowing most blood to bypass the non-functional lungs. At birth, the lungs inflate and pulmonary vascular resistance drops, prompting the ductus arteriosus to close (becoming the ligamentum arteriosum). Failure to close results in patent ductus arteriosus (PDA), causing left-to-right shunting and eventually pulmonary hypertension if untreated.