Chordae Tendineae

1. Overview

The chordae tendineae are fibrous cords in the heart that connect the papillary muscles to the cusps of the atrioventricular (AV) valves, namely the mitral valve and tricuspid valve. These tendinous cords play a crucial role in preventing the inversion or prolapse of the heart valves during systole (the contraction phase of the heart). The chordae tendineae are essential for maintaining the proper functioning of the heart's valve system by ensuring that the valves close tightly and prevent blood from flowing backward into the atria during ventricular contraction. They are key components in the structural integrity and function of the heart valves.

2. Location

The chordae tendineae are located in the ventricles of the heart, specifically in relation to the atrioventricular valves:

• Mitral valve: In the left ventricle, the chordae tendineae are attached to the mitral valve, which has two cusps (anterior and posterior). The chordae tendineae connect the papillary muscles of the left ventricle to the mitral valve cusps, helping to prevent the valve from inverting during contraction.

• Tricuspid valve: In the right ventricle, the chordae tendineae are attached to the tricuspid valve, which has three cusps (anterior, posterior, and septal). Similarly to the mitral valve, the chordae tendineae help maintain proper closure of the tricuspid valve during ventricular contraction.

These chordae are embedded within the walls of the ventricles and extend towards the valves, maintaining the structural stability of the heart's valve apparatus. They are in close proximity to the papillary muscles, which contract during ventricular systole to keep the valve leaflets taut.

3. Structure

The chordae tendineae are thin, fibrous cords composed primarily of collagen and elastin fibers, giving them strength and flexibility. Some key structural features include:

• Length and Thickness: The chordae tendineae vary in length depending on their position and the size of the valve. They are thin but robust, typically measuring a few centimeters in length. The thickness of the chordae varies along their length, with some parts thicker than others, particularly those attached to the papillary muscles.

• Fibrous Composition: The chordae tendineae are primarily made of collagen fibers, which provide tensile strength, and elastin fibers, which give them flexibility. This combination of fibers ensures that the chordae can withstand the mechanical stress of the heart's contraction while still allowing for some degree of elasticity.

• Attachment Points: The chordae tendineae are anchored at one end to the papillary muscles in the ventricles. The other end is attached to the valve leaflets (cusps). These points of attachment are crucial for the function of the chordae, as they must hold the valve leaflets in place during ventricular systole to prevent backflow of blood.

4. Function

The primary function of the chordae tendineae is to maintain the proper closure of the atrioventricular (AV) valves during ventricular contraction. Some key functions of the chordae tendineae include:

• Preventing valve prolapse: During systole, when the ventricles contract, the pressure within the ventricles rises. Without the chordae tendineae, the increased pressure could cause the AV valves to invert or prolapse, leading to blood flowing back into the atria (a condition known as regurgitation). The chordae tendineae prevent this by holding the valve cusps taut, ensuring they close tightly and effectively seal the valve.

• Supporting valve function: The chordae tendineae support the movement of the valve leaflets, ensuring that they open and close properly with each heartbeat. They provide mechanical support to the valve system, facilitating the smooth flow of blood from the atria into the ventricles and preventing backflow during contraction.

• Coordination with papillary muscles: The papillary muscles contract during ventricular systole, pulling on the chordae tendineae. This contraction ensures that the valve leaflets are pulled towards the ventricular walls, which aids in sealing the valve and preventing blood regurgitation. This coordinated action helps regulate the pressure gradient across the AV valves.

5. Physiological Role(s)

The chordae tendineae play several important physiological roles that contribute to the proper functioning of the heart's valve system:

• Efficient blood flow: By ensuring that the AV valves close tightly during ventricular contraction, the chordae tendineae contribute to the efficiency of the heart's pumping action. This allows the ventricles to generate high pressure to send blood to the lungs and the rest of the body while preventing blood from flowing back into the atria.

• Regulation of heart pressure: The chordae tendineae help maintain the appropriate pressure in the atria and ventricles by preventing the inversion of the AV valves. This regulation ensures that the ventricles are filled with blood during diastole and that blood is efficiently ejected during systole.

• Prevention of regurgitation: The most crucial role of the chordae tendineae is to prevent regurgitation, or the backflow of blood, into the atria. Without the proper function of the chordae, regurgitation could occur, leading to reduced cardiac efficiency and overloading of the atria.

• Adaptation during high-output states: During exercise or stress, when the heart must pump blood at a faster rate and higher volume, the chordae tendineae help maintain the integrity of the AV valves under increased pressure. This ensures that the heart continues to function efficiently during times of high metabolic demand.

6. Clinical Significance

The chordae tendineae are critical for the proper functioning of the atrioventricular valves, and any damage or dysfunction can lead to significant heart problems. Some key clinical conditions associated with the chordae tendineae include:

• Mitral valve prolapse (MVP): Mitral valve prolapse occurs when the mitral valve's leaflets become enlarged or displaced, sometimes due to damage to the chordae tendineae. This can lead to mitral regurgitation, where blood flows backward into the left atrium. MVP is a common condition that can lead to symptoms such as palpitations, fatigue, and chest pain. Severe cases may require surgical intervention, such as mitral valve repair or replacement.

• Chordae tendineae rupture: A rupture of the chordae tendineae can occur due to trauma, infection, or certain heart conditions like infective endocarditis. When the chordae tendineae rupture, the affected valve may fail to close properly, leading to valve prolapse and regurgitation. This can result in acute heart failure, and surgical repair may be required.

• Congenital valve malformations: In some cases, congenital abnormalities can affect the chordae tendineae, leading to malformed or poorly functioning valves. These malformations can result in regurgitation or stenosis (narrowing) of the affected valve, which may impair cardiac function and require corrective surgery or other interventions.

• Infective endocarditis: Infective endocarditis is an infection of the heart valves, including the chordae tendineae. This condition can lead to valve damage, abscess formation, and thromboembolic events (blood clots that travel to other parts of the body). Antibiotic treatment is typically required, and in severe cases, surgery may be necessary to repair or replace the damaged valve.

• Tricuspid valve dysfunction: Dysfunction of the tricuspid valve due to chordae tendineae elongation or rupture can cause tricuspid regurgitation, which leads to blood leakage from the right ventricle into the right atrium. This condition can result in symptoms like swelling of the abdomen and legs, and it may require valve repair or replacement.

The chordae tendineae are critical structures in maintaining the proper function of the atrioventricular valves, ensuring that blood flows in the correct direction and preventing regurgitation. Dysfunction or damage to the chordae tendineae can lead to conditions like mitral valve prolapse, tricuspid regurgitation, and infective endocarditis. Early detection and timely intervention are essential for managing these conditions and preserving heart function.