Barlow’s syndrome is another name for mitral valve prolapse (MVP), a condition where the flaps of the heart’s mitral valve become floppy and don’t close tightly during each heartbeat. It affects roughly 1.4% of the general population. Most people with Barlow’s syndrome never experience symptoms or complications, but in some cases the valve allows blood to leak backward, which can eventually strain the heart.
How the Mitral Valve Normally Works
The mitral valve sits between the two left chambers of your heart: the upper chamber (left atrium) and the lower pumping chamber (left ventricle). It has two thin flaps, or leaflets, that open to let blood flow down into the ventricle, then snap shut to prevent blood from flowing backward when the ventricle contracts. Thin cord-like structures called chordae tendineae anchor the leaflets to the heart muscle below, acting like parachute strings that keep the flaps from flipping inside out.
What Goes Wrong in Barlow’s Syndrome
In Barlow’s syndrome, the leaflet tissue undergoes a process called myxomatous degeneration. The normal three-layered structure of the valve breaks down as spongy tissue infiltrates the leaflets, making them thicker, stretchier, and more billowy than they should be. At the microscopic level, the structural proteins that give the valve its strength fragment and become disorganized, while the anchoring cords elongate. The ring of tissue where the valve attaches to the heart (the annulus) can also stretch and widen over time.
This distinguishes Barlow’s disease from a milder form of prolapse called fibroelastic deficiency, where the valve tissue is thin and fragile rather than thick and excessive. Barlow’s disease tends to involve both leaflets and produces more dramatic billowing, while fibroelastic deficiency usually affects a single segment. The distinction matters because Barlow’s disease is more complex to repair surgically and carries a somewhat higher rate of valve leakage returning after surgery.
Symptoms You Might Notice
Many people with Barlow’s syndrome have no symptoms at all and only discover the condition during a routine physical exam or an echocardiogram done for another reason. When symptoms do occur, they commonly include:
- Palpitations: a racing or irregular heartbeat, sometimes felt as skipped beats
- Fatigue: tiredness that seems out of proportion to your activity level
- Dizziness or lightheadedness
- Shortness of breath: particularly during exercise or when lying flat
These symptoms don’t always correlate with how much the valve is actually leaking. Some people with significant prolapse feel fine, while others with minimal prolapse experience noticeable palpitations or fatigue. The autonomic nervous system, which controls heart rate and blood pressure, appears to play a role in driving symptoms independently of the valve problem itself.
How Barlow’s Syndrome Is Diagnosed
A doctor listening with a stethoscope may hear a characteristic midsystolic click, a brief snapping sound that occurs partway through each heartbeat as the floppy leaflets bow backward. If blood is leaking through the valve, a murmur may follow the click. These sounds shift in timing with certain movements or maneuvers, which helps distinguish prolapse from other causes of heart murmurs.
The definitive diagnosis comes from an echocardiogram, an ultrasound of the heart. The formal criterion is displacement of one or both leaflets more than 2 millimeters beyond the valve’s attachment ring at the point when the ventricle is fully contracted. The echo also shows how much blood is leaking backward (regurgitation), the thickness of the leaflets, and whether the heart chambers have started to enlarge in response to the extra workload. Cardiac MRI can identify the same 2-millimeter displacement and provides additional detail about heart muscle function when needed.
Potential Complications
For the majority of people, Barlow’s syndrome remains a benign finding that never causes serious problems. The main concern is progressive mitral regurgitation, where the backward leak worsens over time and forces the heart to work harder. This can eventually lead to enlargement of the left heart chambers, weakened pumping function, and heart failure if left untreated.
Chordal rupture is another possibility. When one of the anchoring cords snaps, a leaflet suddenly flails freely, and regurgitation can worsen dramatically. This sometimes converts a stable, mild condition into one that needs urgent surgical attention. Abnormal heart rhythms are also more common in people with significant prolapse, ranging from harmless extra beats to more concerning rhythm disturbances that require monitoring.
Managing Symptoms Without Surgery
If the prolapse is mild and there’s little or no regurgitation, no treatment is typically needed beyond periodic echocardiograms to track any changes. How often you need imaging depends on the severity: mild cases might be rechecked every few years, while moderate regurgitation warrants more frequent monitoring.
For bothersome palpitations or racing heart, beta blockers are the most commonly used medication. These drugs slow the heart rate and reduce the force of contractions, which can ease the sensation of a pounding or fluttering heart. Staying well hydrated and maintaining adequate electrolyte intake, including magnesium, may also help reduce palpitations, though research has not established a clear link between magnesium supplementation and improvement in the valve problem itself. Regular aerobic exercise is generally safe and encouraged for people with mild to moderate prolapse.
When Surgery Becomes Necessary
Surgery enters the picture when regurgitation becomes severe, particularly if the heart is starting to enlarge or the pumping function is declining. The strong preference is to repair the existing valve rather than replace it with a mechanical or biological prosthetic. Valve repair preserves the heart’s natural geometry, avoids the need for lifelong blood thinners (which mechanical replacements require), and delivers better long-term survival. Data comparing the two approaches show that the survival advantage of repair over replacement grows over time, reaching roughly 21% better survival at 10 to 15 years.
Barlow’s disease presents a greater surgical challenge than simpler forms of prolapse because of the excess tissue, stretched cords, and dilated annulus. However, experienced surgeons achieve durable results even with this complexity. When optimal techniques are used, the rate of significant regurgitation returning after repair falls to around 2 to 3% per year, comparable to the results seen in simpler valve disease. Centers that perform a high volume of mitral valve repairs tend to achieve the best outcomes, so the surgeon’s experience matters considerably.
Recovery after mitral valve repair typically involves several days in the hospital, followed by weeks of gradually increasing activity. Most people return to normal daily life within two to three months, with periodic echocardiograms in the years that follow to confirm the repair is holding.