right heart catheterization

Right heart catheterization is a way of measuring the pressures inside the lung circulation directly, by threading a thin, flexible tube into a vein and steering its tip through the right side of the heart and out into the pulmonary artery. Instead of estimating the pressure from outside, the catheter takes the reading at the source, the way a pressure gauge screwed straight onto a pipe gives a truer figure than guessing from the outside.

The catheter carries a tiny balloon and pressure sensor at its tip. As it advances, it records pressures in the right atrium, right ventricle, and pulmonary artery, and when the balloon is gently inflated to wedge in a small vessel, it gives the pulmonary capillary wedge pressure, an indirect estimate of left-heart filling pressure. Combined with measured blood flow, these numbers reveal the pulmonary vascular resistance.

This is the reference standard for diagnosing and classifying pulmonary hypertension, because it directly confirms the mean pulmonary artery pressure and separates lung-vessel disease from left-heart causes. Although echocardiography can suggest raised pressures non-invasively, only catheterization measures them definitively. It is generally safe in experienced hands, with low rates of serious complications.