The chordae tendineae are tough, fibrous cords found within the heart, often called the “heart strings.” These structures are a fundamental part of the complex machinery regulating the flow of blood through the heart’s chambers. They maintain the heart’s one-way circulatory system and ensure the organ functions efficiently with every beat.
Where the Heart Strings Are Found
These cord-like structures are positioned deep inside the lower chambers of the heart, known as the ventricles. The chordae tendineae connect the flaps of the atrioventricular (AV) valves—the tricuspid valve on the right side and the mitral valve on the left side—to the muscular walls below. They are made primarily of strong collagen protein fibers, which provide structural integrity, along with some elastin fibers that offer flexibility.
The cords extend from the free edges of the valve leaflets down to specialized pillars of heart muscle called papillary muscles. These papillary muscles arise from the inner surface of the ventricular walls and serve as the muscular anchors for the chordae tendineae. This entire assembly—the valve leaflets, the chordae, and the papillary muscles—works together as a single functional unit.
How They Maintain Valve Integrity
The primary mechanical role of the chordae tendineae is to prevent the AV valves from being forced backward into the atria during ventricular contraction. When the ventricles contract in a phase called systole, they generate substantial pressure to push blood out to the rest of the body or the lungs. Without a failsafe, this intense pressure would easily invert the valve leaflets, causing them to prolapse into the low-pressure atria above.
The chordae tendineae act like guy-wires, holding the valve leaflets securely in a closed position against this force. As the ventricular pressure builds, the papillary muscles contract simultaneously, pulling the taut chordae to keep the valve edges aligned and sealed. This active restraint ensures that blood flows forward out of the ventricles and not backward into the atria, a process called preventing regurgitation.
The chordae are classified based on where they attach to the valve leaflets. Marginal chordae attach directly to the free edge of the valve, functioning to prevent the leaflet margin from everting or prolapsing. Other chordae insert further back on the ventricular surface, helping to distribute tension and maintain the proper curvature and shape of the valve against the high-pressure load. Maintaining this structural relationship ensures the complete and instantaneous closure of the valve.
When the Chordae Tendineae Fail
Damage to these cords can severely compromise the heart’s pumping efficiency. When a chord is broken or weakened, it can no longer hold the corresponding valve leaflet in place during ventricular contraction. This failure immediately results in valvular regurgitation, where blood is forcefully ejected backward into the atrium instead of moving forward.
The sudden onset of severe regurgitation, often due to an acute rupture, can lead to symptoms of acute heart failure, including breathlessness and hemodynamic instability. Damage to the chordae tendineae can occur from various causes, such as:
- Infectious endocarditis, where bacteria directly weaken the fibrous tissue.
- Myocardial infarction, or heart attack, which can lead to ischemia and subsequent dysfunction or rupture of the connected papillary muscles.
In some cases, chronic conditions like degenerative mitral valve disease can cause the chordae to become elongated or spontaneously rupture over time, leading to progressive valve leakage. Whether the failure is sudden or gradual, the resulting backflow of blood strains the entire system, requiring the heart to work much harder to move the same amount of blood. Surgical intervention, often involving repair or replacement of the damaged valve apparatus, is frequently necessary to restore proper blood flow dynamics and prevent life-threatening complications.