Heartstrings are real. Inside your chest, thin cords of tissue called chordae tendineae anchor the flaps of your heart valves to the muscular walls below, keeping those flaps from blowing backward every time the heart pumps. The metaphor predates modern anatomy by centuries, but the physical structures it accidentally describes turn out to be remarkably important. When they fail, the consequences can be severe, and when poets talk about tugging at your heartstrings, the biology underneath that feeling is stranger and more literal than most people realize.
The Cords Inside Your Heart
Chordae tendineae are slender, whitish strands that connect the edges of the heart’s valve leaflets to small columns of muscle called papillary muscles. You have them on both sides of the heart, tethering the mitral valve on the left and the tricuspid valve on the right. Their job is mechanical and relentless: every time the ventricles squeeze to push blood out, pressure tries to shove those valve flaps upward and backward. The chordae hold them in place, preventing blood from leaking the wrong way. Without them, each heartbeat would be partly wasted, sending blood sloshing back into the chambers it just left.
Up close, the structure is elegant. The bulk of each cord is collagen, roughly 39% by volume in both the mitral and tricuspid valves, with individual collagen fibrils averaging about 40 to 41 nanometers in diameter.1PubMed Central. Ultrastructural quantification of collagen in human chordae tendineae Those fibrils aren’t arranged straight like piano wire. Instead, they form wavy, undulating bundles that wrap around the entire circumference of each cord, giving it a striped appearance under reflected light. The wave pattern acts like a built-in spring, letting the chordae stretch slightly under load and snap back without tearing.2PubMed Central. Structure of chordae tendineae in the left ventricle of the human heart Considering these cords absorb the force of every single heartbeat for an entire lifetime, that kind of resilience matters.
In younger hearts, the inner core of each cord has an additional layer of protection: regularly spaced ring-like collagen structures that surround the central bundles, somewhat like the rings on a caterpillar. These rings appear to reinforce the cord’s structure. In older hearts, they thin out or disappear entirely.3PubMed. Coil-like structure of the inner core of chordae tendineae That age-related loss hints at why valve problems tend to show up later in life.
Not All Heartstrings Are the Same
If you looked at the underside of the mitral valve, you wouldn’t see a single neat fan of cords. You’d see a tangled web of them, varying in thickness and attachment point. Anatomists divide them into primary (or marginal) chordae, which attach to the very edges of the valve flaps, and secondary (or strut) chordae, which attach farther back on the leaflet body. The distinction matters because these two groups do different things.
Primary chordae are mainly responsible for keeping the valve sealed shut during a heartbeat. They’re the ones that prevent blood from leaking backward. Secondary chordae play a different role: they help maintain the overall shape and geometry of the left ventricle itself. Cutting secondary chordae in experimental settings doesn’t cause the valve to leak right away, but it does warp the chamber’s architecture in ways that degrade pumping efficiency over time.4PubMed. Mitral subvalvular apparatus: different functions of primary and secondary chordae So the chordae aren’t just passive tethers; they’re structural elements that help the whole ventricle keep its shape under pressure. The idea that heartstrings are simple strings is itself an oversimplification. They’re more like a load-bearing cable network.
When Heartstrings Snap
Chordae tendineae can and do rupture, and when they do, the result is sudden and dramatic. A ruptured cord lets part of the valve flap flop backward with each heartbeat, causing mitral regurgitation, which means blood surges back into the left atrium instead of heading out to the body. Symptoms can range from gradual breathlessness to an acute medical emergency, depending on how many cords give way and how quickly.
The most common cause is mitral valve prolapse, a condition where the valve leaflets are slightly too floppy. A systematic review of chordal rupture found that since the mid-1980s, mitral valve prolapse and a related tissue disorder called myxomatous degeneration together account for the majority of cases, with prolapse alone responsible for about 45% and myxomatous degeneration for roughly 12%.5International Journal of Cardiology. The underlying causes of chordae tendinae rupture: A systematic review The review noted that myxomatous degeneration is likely underestimated because not every ruptured cord gets examined under a microscope. In myxomatous degeneration, the collagen that gives chordae their strength gradually breaks down and gets replaced by weaker, spongier tissue. The cord stretches, thins, and eventually gives way. Endocarditis (an infection of the heart lining) and rheumatic heart disease are other known triggers, though both are less common in high-income countries than they once were.
There’s also a rare congenital variant worth knowing about. In a parachute mitral valve, all the chordae tendineae insert into a single papillary muscle instead of the usual two. The name comes from the way the cords converge to one point, making the valve look like a parachute canopy. This arrangement can cause the valve opening to narrow, leading to stenosis or regurgitation. It’s usually caught in childhood, but mild cases occasionally go undiagnosed until adulthood.6PubMed Central. Case Report: Cardiac Adult Presentation of Congenital Mitral Stenosis: The Challenges of a True Parachute Mitral Valve
Fixing and Replacing Broken Cords
When chordae rupture, surgeons can repair the valve rather than replace it entirely, often by stitching in artificial cords made of expanded polytetrafluoroethylene, a synthetic material better known by the brand name Gore-Tex. This material has become the standard for artificial chordae because it holds up well in the body over time and doesn’t provoke a strong immune reaction.7PubMed Central. A review of the development of interventional devices for mitral valve repair with the implantation of artificial chords
Getting the length right is the tricky part. If an artificial cord is even slightly too long or too short, the valve won’t close properly. Surgeons now use three-dimensional imaging during the procedure to measure the exact cord length needed before stitching it in, which shortens the time spent on bypass and improves the accuracy of the repair.8PubMed Central. Real-time three-dimensional transesophageal echocardiography to predict artificial chordae length for mitral valve repair The imaging itself has become sophisticated enough to visualize individual cords and measure their lengths from angles that weren’t accessible a decade ago.9PubMed. Visualization and measurement of mitral valve chordae tendineae using three-dimensional transesophageal echocardiography from the transgastric approach
There’s also growing interest in doing these repairs without open-heart surgery. One device, called the Harpoon, allows surgeons to implant new cords through a small incision in the chest wall while the heart is still beating, guided by ultrasound. Early clinical experience has shown it can work, potentially sparing patients the risks of stopping and restarting the heart on a bypass machine.10PubMed. Transapical Beating-Heart Mitral Valve Repair With an Expanded Polytetrafluoroethylene Cordal Implantation Device: Initial Clinical Experience
Looking further ahead, researchers are developing tissue-engineered replacements that try to mimic the natural architecture of chordae rather than just substituting a synthetic string. One approach, called BioChord, uses a combination of biodegradable and non-degradable polymers shaped into a scaffold that resembles the layered, tendon-like structure of the real thing. Early lab results suggest these scaffolds encourage the body’s own cells to infiltrate and build new tissue around the scaffold, potentially creating a living replacement cord.11Global Cardiology Science and Practice. Engineering Functional Chordae Tendineae: A Mandrel-Less Biofabrication Approach For Heart Valve Repair That work is still early-stage, but it points toward a future where artificial cords could grow and adapt like natural tissue.
Where the Metaphor Came From
The phrase “tug at your heartstrings” feels timeless, but its origin is surprisingly specific. In medieval and early Renaissance anatomy, the heart was believed to be the seat of the soul, emotions, and even thought. When anatomists began dissecting hearts and finding tendons and cords inside, those structures became associated with emotional sensitivity. Writers from at least the fifteenth century onward used “heartstrings” to mean the deepest core of a person’s feelings. The concept evolved alongside European anatomy: as physicians learned what the cords actually did, the metaphor stuck even as the science moved on.
By the time William Harvey described the circulation of blood in the 1620s, the idea that the heart was the center of emotion was already losing ground to the brain-centered view of consciousness. But language is slower to change than science. We kept saying “heartstrings” long after we stopped believing the heart thinks or feels. The word became entirely figurative, carrying no anatomical baggage for most people. Walk into a modern cardiologist’s office and say “heartstrings” and they’ll know you mean chordae tendineae, but in every other context it means something purely emotional.
Why Emotions Really Do Affect Your Heart
The irony is that the old metaphor was less wrong than the brain-first crowd assumed. Your emotional state genuinely influences how your heart behaves, through pathways that have nothing to do with chordae tendineae but everything to do with the nervous system.
The most dramatic example is takotsubo cardiomyopathy, commonly called broken heart syndrome. After severe emotional or physical stress, the left ventricle can suddenly balloon outward and stop contracting normally, mimicking a heart attack. The mechanism involves a surge of stress hormones, particularly catecholamines like adrenaline, that temporarily stun the heart muscle.12PubMed Central. Broken Heart Syndrome: Evolving Molecular Mechanisms and Principles of Management The condition is reversible in most cases and predominantly affects postmenopausal women, though it can occur in anyone.13PubMed. The “broken heart syndrome”: state of the art Researchers are still working out all the contributing factors; current thinking points to a combination of hormonal changes, altered blood flow at the microvascular level, and disrupted signaling along the brain-heart axis.14PubMed. Metformin as a potential therapeutic agent in broken heart syndrome: Targeting AMPK-dependent cardio-protection and microvascular function
Beyond that acute syndrome, the connection between emotional experience and cardiac activity runs deep in everyday life. Research on heartbeat-evoked potentials, which are tiny brain signals that occur in sync with each heartbeat, shows that your brain’s response to its own heartbeat changes depending on your emotional state. When people look at emotionally charged images and consciously notice a shift in their bodily feelings, the brain signal tied to their heartbeat measurably changes.15PubMed Central. Heartbeat evoked potentials reflect interoceptive awareness during an emotional situation The effect is valence-specific: expecting to see something negative amplifies the brain’s cardiac signal differently than expecting something neutral.16PubMed Central. Affective interoceptive inference: Evidence from heart-beat evoked brain potentials In other words, your brain is constantly monitoring your heartbeat, and emotional context reshapes how it processes that information.
The heart-emotion link extends socially, too. When romantic partners sit together and one shares a painful experience, their bodies tend to synchronize. A study of over a hundred couples found that skin conductance and heart rate became more tightly coupled when one partner disclosed a time of suffering while the other listened, though the synchronization of heart rate was only significant when the person sharing was a woman.17PubMed Central. Shared Hearts and Minds: Physiological Synchrony During Empathy Physical touch appears to play a role in this coupling: another study found that holding a partner’s hand increased heart rate synchronization specifically when one partner was in pain, and the degree of coupling was higher when the non-suffering partner scored higher in empathy.18Scientific Reports. The role of touch in regulating inter-partner physiological coupling during empathy for pain The metaphor of shared heartstrings has a faint echo in measurable physiology.
Heartstrings Across Species
Chordae tendineae aren’t unique to humans. Any animal with a four-chambered heart and atrioventricular valves has some version of these cords. Mammals broadly share the same architecture: valve leaflets, papillary muscles, and chordae connecting them. But the details vary, and those differences tell you something about the demands placed on each heart.
Chickens, for example, have chordae tendineae with a noticeably different organization than human ones. A study using electron microscopy found that in chickens, the collagen fibrils on the left side of the heart were thicker than those on the right, reflecting the higher pressure the left ventricle has to generate. Chickens also lack some of the structural subtypes found in mammalian hearts, having only perichordal and interchordal ligaments rather than the full range of supporting structures humans have. Within individual chords, the base and apex differed in structure, but the very tips looked the same regardless of which side of the heart they were on.19PubMed. The chordae tendineae of the heart in chicken
Comparative anatomy like this is more than trivia. Understanding how chordae vary across species helps bioengineers design better replacement materials and helps veterinary cardiologists treat valve disease in animals from dogs to horses, where chordal rupture is a recognized clinical problem. The shared evolutionary architecture also reinforces just how fundamental these tiny cords are: hearts have been relying on some form of internal tethering for hundreds of millions of years.
Common Misconceptions About Heartstrings
A few ideas about chordae tendineae circulate widely and deserve correction. The first is that they’re like guitar strings or harp strings, vibrating to produce sound. They don’t. The sounds your heart makes come from the valve leaflets snapping shut and blood flowing turbulently through openings. The chordae themselves are passive tethers that absorb tension rather than create vibration. A heart murmur caused by mitral regurgitation does involve the chordae failing, but the sound comes from the jet of blood leaking backward through the incompetent valve, not from the cords themselves.
A second misconception is that emotional distress can directly damage the chordae. Broken heart syndrome, as described above, involves the heart muscle itself, not the chordae tendineae. Stress hormones stun the myocardium; they don’t snap the cords. Chordal rupture is a structural failure of connective tissue, driven by degeneration, infection, or congenital abnormality. Emotional pain is real, and it genuinely affects the heart, but through different pathways than people typically imagine when they picture heartstrings breaking.
A third and subtler misconception is that heart valve problems always require valve replacement. For many patients with chordal rupture or prolapse, repair with artificial cords preserves the native valve and produces better long-term outcomes than putting in an entirely new one. The shift toward repair over replacement has been one of the bigger quiet trends in cardiac surgery over the past few decades, and it depends heavily on understanding the chordae and matching artificial substitutes to their geometry.