Pulmonary artery catheterization is a technique used to monitor cardiac pressures and output. The catheter is inserted into the internal jugular, subclavian, or femoral veins and threaded into the pulmonary artery. It has four lumens to measure pressures in the right atrium, right ventricle, pulmonary artery, and by wedging in a pulmonary capillary. Indications include major surgery, heart disease, or hemodynamic instability. Complications include arrhythmias, thromboembolism, and pulmonary artery rupture. Abnormal waveforms provide information on conditions like mitral regurgitation. Controversy exists on outcomes, with some studies finding increased risk while others found no effect or benefit in selected patients.