Papillary muscles

At a glance

English

Papillary muscles

Latin (TA2)

Musculi papillares

System

Heart

Region

Thorax

In order

From the anterior papillary muscle of right ventricle to the inferior papillary muscle of left ventricle

About the papillary muscles

Papillary muscles are specialised trabeculae carneae, columns of heart muscle that rise from the inner walls of the ventricles like fingers. Their bases are rooted in the ventricular wall and their tips give rise to chordae tendineae, the fine fibrous cords that run to the free edges and undersides of the atrioventricular valve leaflets. Together the leaflets, cords, papillary muscles and the ring make up the valve apparatus.

Each muscle sends cords to two neighbouring leaflets, never to one alone. This arrangement means that when a papillary muscle contracts it draws the adjoining edges of two leaflets together. The muscles contract a fraction of a second before the rest of the ventricle, triggered early by the conducting system, so the cords are already tight when pressure rises. They do not open or shut the valve; they stop the leaflets from turning inside out into the atrium, much as the stays hold a sail.

The right ventricle normally has three groups. The anterior papillary muscle is the largest and is linked to the septum by the moderator band, which carries part of the right bundle branch to it. The inferior (posterior) muscle is often made of two or three parts. The septal papillary muscles are small and variable, and several cords on that side spring straight from the septum. The left ventricle has two large muscles, anterolateral and posteromedial (in current terms superior and inferior), each supplying cords to both mitral leaflets. The left ones are thicker, reflecting higher pressure.

The papillary muscles sit at the end of their arterial supply, which makes them vulnerable to poor blood flow. The inferior muscle of the left ventricle usually depends on a single artery, most often from the right coronary system, and is the one most likely to rupture after a heart attack, causing sudden severe mitral regurgitation that needs urgent surgery. Less extreme damage or stretching of the ventricle displaces the muscles and lets the valve leak.

Along the series the muscles change with the pressure of their chamber. Those of the right ventricle are slender, numerous and variable, matching the thin wall and low pressure of the lung circulation, and their cords may also arise directly from the septum. Those of the left ventricle are only two, but each is a thick, often multi-headed column firmly rooted in the wall. On echocardiography the papillary muscles are checked for size and movement, and in hypertrophic cardiomyopathy they may be enlarged or abnormally placed.