Chordae tendineae are thin, cord-like structures inside your heart that tether the flaps of your heart valves to the muscular walls of the ventricles. Their primary job is to keep those valve flaps from flipping backward when the heart contracts, ensuring blood flows in one direction. Without them, every heartbeat would push blood the wrong way, and the heart would quickly fail. They are sometimes called “heart strings,” which is actually a fairly accurate description of what they look like: pale, fibrous threads that fan out from cone-shaped muscles to the undersides of the valve leaflets, holding everything in place under remarkable mechanical stress.
Where They Sit and What They Look Like
Chordae tendineae connect two structures: the papillary muscles, which are small columns of muscle projecting from the inner wall of each ventricle, and the leaflets (also called cusps) of the atrioventricular valves. Your heart has two of these valves. The mitral valve sits between the left atrium and the left ventricle and has two leaflets. The tricuspid valve sits between the right atrium and right ventricle and has three leaflets. Both valves have their own set of chordae.
Under a microscope, chordae tendineae are composed mainly of collagen fibers with interwoven elastic fibers, all covered by a thin layer of endocardium, the same smooth tissue that lines the inside of the heart. The collagen fibrils have a wavy, undulating arrangement when the chordae are relaxed. When the papillary muscle contracts and pulls the chord taut, those waves straighten out, which absorbs some of the peak stress before it reaches the valve leaflet. When the muscle relaxes, the elastic tissue pulls the collagen back into its wavy shape, essentially resetting the system for the next heartbeat.1PubMed Central. Structure of chordae tendineae in the left ventricle of the human heart This built-in shock-absorbing design is crucial for tissue that gets stretched and released roughly 100,000 times a day.
Not all chordae look the same. Anatomical studies of cadaveric hearts have identified several branching patterns: some chordae run as a single strand from muscle to leaflet, some fan out into multiple branches, and some form web-like networks.2PubMed. Morphology of the papillary muscles and the chordae tendineae of the ventricles of adult human hearts The number of chordae also varies between the two valves. Comparative studies across mammalian hearts have found that the tricuspid valve has roughly twice as many chordae as the mitral valve, and the chordae attaching to the posterior papillary muscle tend to be nearly double the number of those on the other papillary muscles.3PubMed Central. A comparative study of the morphology of mammalian chordae tendineae of the mitral and tricuspid valves
True Chordae, False Chordae, and How They Are Classified
Cardiologists and anatomists sort chordae tendineae into categories based on where they attach and what role they play. The broadest split is between “true” chordae and “false” chordae. True chordae originate from a papillary muscle and insert into a valve leaflet. They are the functional anchors of the valve. False chordae, by contrast, run between a papillary muscle and the ventricular wall, or between two papillary muscles, without touching a valve leaflet at all.2PubMed. Morphology of the papillary muscles and the chordae tendineae of the ventricles of adult human hearts False chordae do not directly prevent valve leakage, though they may play a supporting structural role in the ventricle.
True chordae are further divided by where exactly they attach on the leaflet. First-order (or marginal) chordae attach to the free edge of the leaflet, the very tip that opens and closes. Second-order (or rough-zone) chordae attach slightly further back, on the underside of the leaflet near the free edge. Third-order (or basal) chordae, found mainly on the posterior mitral leaflet, insert closer to the base of the leaflet near the valve ring. Additional types include commissural chordae, which insert at the junction where two leaflets meet, and cleft chordae, which attach at indentations within a leaflet.4PubMed Central. Morphological Study of Chordae Tendinae in Human Cadaveric Hearts
These categories are not just academic labels. They correspond to meaningfully different jobs. Research on the mitral valve’s subvalvular apparatus has shown that primary (first-order) chordae are more involved in keeping the valve sealed shut during contraction, while secondary chordae play a bigger role in maintaining the shape and geometry of the left ventricle itself.5PubMed. Mitral subvalvular apparatus: different functions of primary and secondary chordae Cutting or losing a primary chord has different consequences than losing a secondary chord, which matters enormously in surgical planning.
How Chordae Tendineae Keep Blood Moving the Right Way
Every time your left ventricle contracts, the pressure inside it spikes dramatically. That pressure tries to push everything outward, including the mitral valve leaflets back toward the atrium. The chordae tendineae prevent this. As ventricular pressure rises, the papillary muscles contract in sync, pulling the chordae taut and holding the leaflets in a closed position. The chordae distribute the closing forces from the leaflets down to the papillary muscles, preventing the leaflets from prolapsing (flipping back) into the atrium.6PubMed Central. Mechanics and Microstructure of the Atrioventricular Heart Valve Chordae Tendineae: A Review
This force distribution is not uniform. Computational modeling has shown that in the mitral valve’s posterior leaflet, the basal chordae bear the highest tension, followed by the intermediate chordae, with the marginal chordae carrying the least. In the anterior leaflet, the strut chordae, which are thick secondary chordae unique to that leaflet, carry particularly high loads.7Scientific Reports. New insights into mitral heart valve prolapse after chordae rupture through fluid–structure interaction computational modeling The system is engineered so that different chordae carry different shares of the load, creating redundancy. If one chord weakens, the neighboring chords can compensate, at least up to a point.
An interesting detail from fluid-dynamics research: during systole (the contraction phase when blood is ejected), the chordae themselves have only a minor effect on the overall pressure drop and pumping efficiency of the ventricle. You could model ventricular blood flow during systole without including the chordae and get reasonably accurate results for pressure and efficiency. However, the chordae do create small vortices in the blood flow around themselves, and they play a larger role in shaping diastolic filling patterns.8PubMed. The effect of chordae tendineae on systolic flow Their primary contribution is structural, holding the valve shut, rather than aerodynamic.
What Happens When Chordae Rupture
A ruptured chord is one of the more dramatic mechanical failures that can happen inside a heart. When a chord snaps, the portion of the valve leaflet it was holding loses its anchor. That section of the leaflet flails backward into the atrium during contraction, and blood rushes through the gap in the wrong direction. The result is acute mitral regurgitation, which can be severe and life-threatening. Patients with acute chordal rupture typically present with sudden-onset pulmonary edema, signs of heart failure, and sometimes cardiogenic shock. A new holosystolic murmur, a whooshing sound heard through a stethoscope throughout the contraction phase, is a key clinical sign that something has torn.9PubMed Central. An Unusual Presentation of Acute Severe Mitral Regurgitation
The severity depends on which chord breaks and how many are affected. Computational modeling of progressive chordal rupture shows that when a single chord fails, the remaining chords redistribute the load. But as more chords rupture, a tipping point is reached. During total double-scallop prolapse (where two adjacent segments of the posterior leaflet both flail), the tension in some remaining chords can drop by more than half, because those segments are no longer effectively participating in valve closure at all.7Scientific Reports. New insights into mitral heart valve prolapse after chordae rupture through fluid–structure interaction computational modeling At that stage, the valve is no longer functioning, and the patient needs emergency intervention.
Case reports illustrate just how rapidly this can deteriorate. In one reported case, a 22-year-old man presented with worsening symptoms and was found to have severe mitral regurgitation caused by chordal rupture of the posterior mitral leaflet, with an ejection fraction of only 28 percent. He developed cardiogenic shock requiring mechanical circulatory support and ultimately died from multiorgan failure.10American Journal of Case Reports. Acute Mitral Regurgitation Due to Chordae Tendineae Rupture: A Rare Presentation of Cardiac Amyloidosis Cases like this are at the extreme end, but they show why chordal integrity is not something the heart can do without.
Why Chordae Degenerate or Break
The causes of chordal rupture have shifted over time. A systematic review tracking the underlying causes found that before 1985, infective endocarditis and rheumatic heart disease together accounted for the vast majority of cases. Since 1985, those causes have declined sharply, and mitral valve prolapse and myxomatous degeneration have taken over as the leading causes. Myxomatous degeneration alone accounted for about 12 percent of cases after 1985, but the review noted this is likely an underestimate, since microscopic evaluation of the tissue was not routinely performed. In fact, myxomatous degeneration is probably the single most common underlying cause, because it also drives most cases of mitral valve prolapse.11International Journal of Cardiology. The underlying causes of chordae tendinae rupture: A systematic review
Myxomatous degeneration is a process in which the normal collagen and elastic-fiber architecture of the chord gradually breaks down and is replaced by looser, weaker connective tissue. The chord becomes thinner, more elongated, and eventually unable to bear the repetitive stress of normal heartbeats. This process tends to worsen with age, which is why chordal rupture is more common in older adults, though it can happen at any age.
Other causes include connective tissue diseases such as systemic lupus erythematosus, which can damage the valve through a form of inflammation called Libman-Sacks endocarditis.12Journal of Clinical Review & Case Reports. Libman-Sacks Endocarditis and Chordae Tendineae Rupture as Sudden Presentation of Systemic Lupus Erythematous Ischemic heart disease can also cause trouble indirectly: when a heart attack damages the papillary muscle that anchors the chordae, the muscle can become dysfunctional or even rupture, causing the attached chordae to lose their mechanical foundation.13Kosin Medical Journal. Dynamic Change of Ischemic Mitral Regurgitation in a Patient with Acute Coronary Syndrome In some of these ischemic cases, the regurgitation is transient and resolves once blood flow to the muscle is restored, which makes recognizing the underlying cause critical for choosing the right treatment.
How Density Changes Reveal Weakened Chords
Researchers have been looking for ways to detect chordal weakness before a rupture happens. One approach uses advanced imaging to measure the physical density of the tissue. A study using synchrotron-based X-ray phase computed tomography (a high-resolution imaging technique far beyond standard clinical CT scans) found that ruptured chordae tendineae had significantly lower tissue density compared to healthy ones. The ruptured group averaged a density of about 1.029 grams per cubic centimeter, compared to about 1.085 in the control group.14Journal of Synchrotron Radiation. Structural properties in ruptured mitral chordae tendineae measured by synchrotron-based X-ray phase computed tomography
This is still a research tool rather than something used in everyday clinical practice, but it points toward the idea that structural deterioration in chordae might eventually be detectable through imaging before the chord actually snaps. For now, echocardiography remains the standard way to evaluate chordal function in living patients. A skilled echocardiographer can often see elongated, thickened, or flailing chordae and identify regurgitation jets on a color Doppler study well before a patient reaches an emergency.
Surgical Repair With Artificial Chordae
When chordae rupture or degenerate beyond function, surgeons can replace them with synthetic substitutes. The most widely used material is expanded polytetrafluoroethylene (ePTFE), a form of the same polymer used in Gore-Tex fabric. These artificial chordae are sutured between the papillary muscle and the valve leaflet, mimicking the anchoring function of the original tissue. The technique is well established and has been in use for decades.15PubMed Central. Artificial chordae for mitral valve repair
Long-term follow-up data are reassuring. A study tracking 74 patients who received ePTFE chordal replacements from 1988 to 1999 found that the reoperation-free rate was about 94 percent at five years and roughly 82 percent at ten years. When surgeons examined ePTFE material that was removed during reoperations, they found no calcification, preserved flexibility, and the surface had become completely lined with endothelial cells, the body’s own protective layer. Collagen growth was observed where the synthetic chord was anchored to the leaflet and papillary muscle, suggesting the body actively integrates the material over time.16Circulation. Ten-Year Experience of Chordal Replacement With Expanded Polytetrafluoroethylene in Mitral Valve Repair
More recent data from a larger series of over 400 consecutive patients who underwent mitral valve repair between 2002 and 2020 confirmed long-term feasibility. The most common reason for reoperation in the artificial chordae group was rupture of the ePTFE suture, though this remained uncommon overall.17PubMed. Predictors of Failure of Mitral Valve Repair Using Artificial Chordae Valve repair is strongly preferred over valve replacement when possible, because it preserves the patient’s own valve tissue and avoids the lifelong blood-thinning medication typically required with mechanical replacement valves.
When native valve repair is not feasible, particularly in patients with connective tissue diseases likely to cause recurrent damage, full mitral valve replacement may be necessary instead.12Journal of Clinical Review & Case Reports. Libman-Sacks Endocarditis and Chordae Tendineae Rupture as Sudden Presentation of Systemic Lupus Erythematous The decision between repair and replacement depends on the underlying disease, the extent of damage, and the likelihood that the remaining valve tissue will hold up over time.
Minimally Invasive and Beating-Heart Approaches
Traditional chordal replacement requires open-heart surgery with a cardiopulmonary bypass machine. Newer techniques aim to accomplish the same thing with less invasive access. One approach involves a transapical route, where a small incision is made near the apex of the heart, and an artificial neochord is implanted while the heart is still beating. Early feasibility work on repairing anterior mitral leaflet flail through this approach has been reported.18PubMed. Feasibility of anterior mitral leaflet flail repair with transapical beating-heart neochord implantation The appeal of beating-heart procedures is avoiding the risks of stopping the heart and placing the patient on a bypass machine, which can be particularly beneficial for older or sicker patients who may not tolerate open surgery well.
Tissue engineering represents a further frontier. Researchers are developing scaffolds made from stabilized biological materials, like treated pericardium, that could serve as replacements for heart valve components. The goal is to create materials that function immediately after implantation but are gradually remodeled by the body’s own cells, eventually becoming living tissue rather than a permanent synthetic implant.19PubMed Central. Stabilized collagen scaffolds for heart valve tissue engineering This work remains largely experimental, but it points toward a future where replacement chordae could grow and adapt alongside the patient’s own heart.
How Chordae Develop Before Birth
The developmental origin of chordae tendineae is more complex than researchers initially assumed. The traditional view held that chordae form from the valve leaflets themselves, essentially stretching and separating from the leaflet as it peels away (delaminates) from the ventricular wall during fetal growth. More recent work on fetal bovine hearts has challenged this idea, finding branched chordae tendineae present well before the leaflet has fully delaminated. This suggests that the chordae may develop independently from the leaflet tissue, forming through their own parallel developmental pathway rather than being carved out of the leaflet.
Congenital abnormalities of the chordae, while rare, provide a window into how sensitive this developmental process is. In a parachute mitral valve, all of the chordae insert into a single papillary muscle instead of the normal two. This can result from fusion of the two papillary muscles or from one muscle failing to develop properly. The funneling of all chordae into one attachment point restricts the valve’s ability to open fully, causing stenosis, and can also lead to regurgitation.20PubMed Central. Case Report: Cardiac Adult Presentation of Congenital Mitral Stenosis: The Challenges of a True Parachute Mitral Valve Parachute mitral valve is sometimes diagnosed in childhood as part of a cluster of left-sided heart defects, but mild cases can escape detection until adulthood, when the restricted valve opening finally causes symptoms under the demands of a fully grown body.
The Tricuspid Valve Gets Less Attention
Most of the clinical and research spotlight falls on chordae tendineae of the mitral valve, and for good reason: the left ventricle generates much higher pressures than the right, so the mitral chordae operate under greater mechanical stress and fail more often. But the tricuspid valve has its own set of chordae, roughly double the number of the mitral valve, distributed across three leaflets and typically three papillary muscles.3PubMed Central. A comparative study of the morphology of mammalian chordae tendineae of the mitral and tricuspid valves
Tricuspid regurgitation is increasingly recognized as a significant clinical problem, especially in older adults and in patients with long-standing left-sided heart disease or pulmonary hypertension. The tricuspid valve’s chordae can undergo the same degenerative processes that affect mitral chordae, and surgical or interventional repair of the tricuspid valve is an area of active development. For years, the tricuspid valve was considered the “forgotten valve” because it tolerated dysfunction without immediately obvious consequences. That perception is changing as evidence accumulates that untreated severe tricuspid regurgitation worsens outcomes and quality of life. The chordae tendineae of this valve deserve the same careful anatomical respect that their left-sided counterparts have long received.