The chordae tendineae are thin, strong, fibrous strings found in the heart’s ventricles. They are also known as the heart strings.
Structure
The chordae tendineae are made up of collagenous fibers, elastic fibers, and endothelial cells. These components give the chordae tendineae their strength and flexibility. The collagenous fibers provide tensile strength, which is crucial for withstanding the pressure changes and forces that occur within the heart during the cardiac cycle. The elastic fibers allow for the slight stretch and recoil necessary for their function.
Appearance
The chordae tendineae are cord-like structures that are typically pearly white in color due to their dense connective tissue composition. They vary in thickness and length but are generally slender, measuring just a few millimeters in diameter. Each chord is attached at one end to the papillary muscles, which are small muscular projections from the inner surface of the ventricles, and at the other end, they fan out to attach to the edges of the atrioventricular valves (the mitral valve in the left ventricle and the tricuspid valve in the right ventricle).
In the heart, the chordae tendineae extend from the apex of the papillary muscles to the ventricular side of the atrioventricular valves’ leaflets. They look somewhat similar to the strings of a parachute, where the canopy of the parachute would be analogous to the valve leaflets, and the person or object secured by the parachute would be analogous to the papillary muscles.
Each ventricle contains several groups of chordae tendineae, corresponding to the number of cusps (or leaflets) of the atrioventricular valve they are connected to. The chordae are organized in a hierarchical manner: there are primary (marginal) chordae, which attach directly to the free edges of the valve leaflets; secondary (intermediate) chordae, which attach to the ventricular surface of the valve leaflets; and tertiary (basal) chordae, which may attach more to the ventricular wall or valve annulus.
Location
The chordae tendineae are located inside the heart’s ventricles. Specifically, they are found in the right and left ventricles, attached at one end to the papillary muscles, which are small muscular projections from the inner walls of the ventricles. The other end of the chordae tendineae is attached to the cusps (also known as leaflets) of the atrioventricular valves:
- In the right ventricle, they are connected to the tricuspid valve, which has three cusps.
- In the left ventricle, they attach to the mitral (bicuspid) valve, which has two cusps.
The chordae tendineae, along with the papillary muscles and the valve cusps, work together to prevent the inversion or prolapse of these valves into the atria during ventricular contraction, ensuring that blood flows in the correct direction through the heart.
Function
The chordae tendineae have several critical functions in the heart’s physiology:
- Valve Closure: They play a crucial role in ensuring the proper closure of the atrioventricular valves (the tricuspid valve in the right ventricle and the mitral valve in the left ventricle) during ventricular contraction (systole). This prevents the backflow of blood from the ventricles back into the atria.
- Preventing Valve Prolapse: The chordae tendineae help prevent prolapse of the atrioventricular valve leaflets into the atrial chambers during systole. Prolapse can lead to regurgitation, where blood leaks back into the atria, impairing the heart’s efficiency and increasing the workload on the heart.
- Maintaining Valve Integrity: By anchoring the valve leaflets to the papillary muscles, the chordae tendineae maintain the structural integrity and correct positioning of the valve leaflets, ensuring they provide an effective seal when closed.
- Facilitating Efficient Blood Flow: By contributing to the proper functioning of the heart’s valves, the chordae tendineae help facilitate efficient blood flow through the heart and to the rest of the body, maintaining adequate cardiac output and blood pressure.
- Aiding in Heart Muscle Function: While their primary role is in valve function, the connection of the chordae tendineae to the papillary muscles also means that they play a part in the overall mechanics of heart muscle contraction and coordination during the cardiac cycle.
Clinical significance
The chordae tendineae have significant clinical implications, especially in the context of heart valve diseases and conditions affecting the ventricular structure.
- Valvular Heart Disease: Damage to the chordae tendineae can lead to valvular heart disease, such as mitral valve prolapse (MVP) or tricuspid valve prolapse. In these conditions, the affected valve does not close properly, leading to regurgitation, where blood flows backward into the atrium each time the ventricle contracts. This can result in decreased cardiac efficiency and increased heart workload.
- Infective Endocarditis: This is an infection of the heart valves and the inner lining of the heart chambers and can lead to the damage of the chordae tendineae. If the chordae are damaged or weakened by infection, this can exacerbate problems with valve function, leading to regurgitation or heart failure.
- Rheumatic Heart Disease: This condition, which follows rheumatic fever, can lead to scarring and shortening of the chordae tendineae. This, in turn, can affect valve function, typically resulting in stenosis (narrowing of the valve) or regurgitation.
- Congestive Heart Failure: While congestive heart failure is not directly caused by issues with the chordae tendineae, their dysfunction due to valve problems can contribute to the worsening of this condition. Poor valve function leads to inefficient blood flow, which can strain and weaken the heart, contributing to or exacerbating heart failure.
- Surgical Repair and Replacement: Understanding the structure and function of the chordae tendineae is crucial for cardiac surgery, especially valve repair and replacement surgeries. Preserving or restoring the function of the chordae tendineae during such procedures can significantly affect the outcome and long-term success of the surgery.
- Echocardiography: In diagnostic imaging, especially echocardiography, the chordae tendineae can be visualized and assessed for structural integrity and function. This is crucial for the diagnosis and management of various heart conditions, including valve diseases and endocarditis.
