Congenital cleft of the mitral valve leaflets is a rare cardiac malformation characterized by the presence of a structural discontinuity in one or both valve leaflets, most frequently affecting the anterior leaflet. This anomaly results in incomplete coaptation of the leaflets during systole, leading to varying degrees of mitral regurgitation. The condition may occur as an isolated defect or in association with other congenital heart diseases, particularly atrioventricular septal defects. Although some forms may remain silent for years, hemodynamically significant cases are dominated by symptoms of mitral regurgitation, progressing to left-sided heart failure if left untreated.
The etiology of congenital cleft of the mitral valve leaflets is attributed to a developmental defect of the endocardial cushion and the atrioventricular valve tissue during embryogenesis. Between gestational weeks 5–7, the endocardial cushions fuse to form the central portion of the mitral valve apparatus, including the leaflets, chordae tendineae, and part of the atrioventricular septum. If this process is incomplete or disorganized, a linear or branched fissure may remain in one of the leaflets, typically the anterior one, which is the continuation of the primitive septum. This anomaly represents a failure of tissue fusion and, although morphologically similar to a “cleft,” it has a distinct embryologic origin compared to acquired fenestrations or post-inflammatory ruptures.
Risk factors are not always identifiable, but well-documented associations exist with other congenital anomalies, particularly:
In rare isolated cases, the origin may be sporadic or linked to mutations interfering with endocardial cushion differentiation, such as disruptions in the Notch, Wnt, or TGF-β signaling pathways, all of which play key roles in atrioventricular morphogenesis.
From a pathogenic standpoint, the cleft typically affects the coaptation line of the anterior mitral leaflet, medially located and often directed toward the septum. This configuration is considered the classical variant, but other forms have been described, including para-commissural or multiple clefts, sometimes branched, which may also involve the posterior leaflet or mimic a fenestration. The position and morphology of the cleft determine the degree of regurgitation and influence the surgical strategy. In some cases, the cleft may extend toward the chordae tendineae or commissural margins, exacerbating regurgitation and further compromising valve stability.
It is important to differentiate this condition from acquired leaflet ruptures, which occur in entirely different contexts such as infective endocarditis, myxomatous degeneration, chest trauma, or papillary muscle ischemia. Congenital cleft is present from birth, has regular and contiguous margins, and is not associated with necrotic tissue, vegetations, or calcifications.
The resulting pathophysiology is typical of congenital mitral regurgitation. The loss of valvular competence during systole leads to backward blood flow into the left atrium, resulting in volume overload. Initially, the left ventricle compensates with eccentric hypertrophy and increased compliance, maintaining effective stroke volume. Over time, chronic hypervolemia leads to progressive dilation of the left atrium and ventricle, alteration of valvular geometry, and eventual impairment of contractile function. In advanced stages, reactive pulmonary hypertension develops, followed by right ventricular dysfunction and biventricular heart failure.
The clinical severity depends on multiple factors: cleft size and location, stiffness or laxity of adjacent leaflets, presence of subvalvular support abnormalities (chordae and papillary muscles), and coexistence of associated lesions. Progression may be slow and subclinical or rapid in cases of significant regurgitation.
The clinical presentation of congenital cleft of the mitral valve leaflets is highly heterogeneous and essentially depends on three factors: the size and location of the cleft, the resulting degree of mitral regurgitation, and the presence or absence of associated cardiac anomalies. In many cases—particularly when isolated and hemodynamically mild—the condition may remain asymptomatic for years and be discovered incidentally during auscultation or an echocardiogram performed for unrelated reasons.
In symptomatic patients, the clinical picture is closely related to the severity of mitral regurgitation and the adaptive response of the left heart.
In neonates and infants with severe regurgitation, the clinical presentation corresponds to high-output heart failure. Volume overload increases atrial and ventricular filling pressures, leading to pulmonary congestion. The most frequent signs in this age group include:
In older children and adolescents, symptoms tend to present more insidiously and progress gradually. Exertional dyspnea is often the first reported symptom, followed by fatigue and exercise intolerance. As atrial dilation progresses, patients may experience palpitations due to atrial extrasystoles or episodes of supraventricular tachyarrhythmias. In advanced cases, clinical signs of pulmonary hypertension and right ventricular dysfunction may emerge, such as peripheral venous congestion, pulsatile hepatomegaly, and systemic circulatory disturbances.
On physical examination, the most consistent finding in symptomatic patients is the presence of a holosystolic murmur, typically audible at the cardiac apex and radiating to the left axilla. The murmur may vary in intensity depending on the amount of regurgitation and atrial compliance. In some cases, a third heart sound (S3) may be heard, indicating volume overload. In children with advanced heart failure, bibasilar pulmonary crackles and an accentuated pulmonary second heart sound may be present in the setting of pulmonary hypertension.
It is important to note that in the presence of associated anomalies—such as atrioventricular septal defects or other valvular dysplasias—the symptoms may be modulated or masked. In such cases, symptom interpretation requires an integrated clinical and instrumental assessment. The possibility of an isolated, paucisymptomatic, or latent presentation further underscores the need for careful auscultation and echocardiography, even when clinical indications are minimal.
In completely asymptomatic patients, the first clue may be an ECG alteration (e.g., broad or bifid P waves due to atrial dilation) or an incidental finding of cardiomegaly on chest X-ray. In all cases, the progression of regurgitation and potential ventricular remodeling necessitate regular clinical and echocardiographic monitoring, even in the absence of overt symptoms.
The diagnosis of congenital cleft of the mitral valve leaflets requires careful integration of medical history, clinical signs, and cardiac imaging, with particular attention in cases where symptoms are subtle or absent. Clinical suspicion is often based on the detection of an apical systolic murmur on auscultation, in a patient without a history of rheumatic fever or other acquired causes of mitral regurgitation. In children and adolescents, the diagnosis may also be suggested by indirect signs such as cardiomegaly, ECG changes, or recurrent episodes of fatigue.
The Electrocardiogram (ECG) may reveal signs of left atrial overload (bifid P waves in lead II or “P mitrale”) and, in more advanced cases, axis deviations or supraventricular arrhythmias.
The Chest X-ray is useful to assess cardiomegaly—predominantly involving the left atrium and ventricle—and to identify signs of pulmonary congestion.
The fundamental diagnostic tool is transthoracic echocardiography (TTE), which allows direct visualization of the valvular cleft and quantification of the mitral regurgitation. In parasternal long-axis or apical four-chamber views, the cleft appears as a linear or V-shaped interruption along the coaptation line of the mitral leaflet, often associated with an eccentric regurgitant jet. Continuous-wave and color Doppler facilitate analysis of regurgitation direction, extent, and velocity, as well as estimation of the transvalvular gradient.
When the anomaly is difficult to visualize, or in older patients with a poor acoustic window, transesophageal echocardiography (TEE) is indicated, offering superior resolution and detailed evaluation of valvular morphology and dynamics. TEE is particularly useful in surgical planning, as it allows:
In selected cases—particularly when complex surgery is anticipated or multiple structural defects are present—advanced imaging may be warranted. Cardiac magnetic resonance (CMR) is valuable for accurate quantification of regurgitant volume, evaluation of left ventricular function, and identification of myocardial fibrosis areas.
Cardiac computed tomography (CT) plays a more limited role but may be useful in specific contexts (e.g., patients with contraindications to MRI or the need for extracardiac anatomical definition).
Differential diagnosis should primarily consider other causes of congenital mitral regurgitation, such as parachute mitral valve, mitral valve dysplasia, and the presence of accessory chordae tendineae. It is also crucial to distinguish congenital cleft from acquired leaflet ruptures, which result from endocarditis, trauma, or myxomatous degeneration, and are characterized by irregular margins, vegetations, calcifications, or leaflet prolapse.
Accurate diagnosis is essential not only to define the severity of the hemodynamic impact but also to properly plan surgical treatment, if indicated.
Therapeutic management of congenital cleft of the mitral valve leaflets is based on a careful assessment of mitral regurgitation severity, clinical symptoms, and the degree of hemodynamic compromise. In patients with mild regurgitation and preserved left ventricular function, a conservative approach may be appropriate, consisting of regular echocardiographic monitoring and clinical follow-up—especially if the patient is asymptomatic and the cleft exhibits a stable morphology. However, in moderate to severe cases, or when signs of heart failure are present, surgical intervention becomes the standard of care.
Indications for surgery include:
Valve repair is the preferred procedure and aims to achieve anatomical closure of the cleft while preserving the native valvular apparatus. In most cases, direct suture closure of the cleft with non-absorbable single stitches is feasible. When the cleft is wide or involves commissural margins, leaflet plasty may be performed, often with annuloplasty using a prosthetic ring or reinforcing band to prevent secondary dilation.
In more complex situations, such as in the presence of valvular dysplasia or abnormal subvalvular apparatus, mitral valve replacement may be necessary—an option reserved for selected cases, due to higher morbidity and the requirement for long-term anticoagulation, especially in pediatric patients.
The prognosis after surgical intervention is excellent in most cases, especially when correction occurs early and via repair techniques. Isolated mitral cleft repair is associated with high long-term survival, good functional recovery, and low reoperation rates. Residual mitral regurgitation is generally minimal and well tolerated, though it requires regular monitoring to prevent late progression.
Postoperative follow-up should include annual echocardiographic assessments, monitoring of systolic function and cardiac chamber dimensions, along with evaluation of functional capacity and potential arrhythmia onset. In children, somatic growth can influence valvular geometry over time, making age- and surgery-response-tailored surveillance essential.
Favorable prognostic factors include valve repairability, absence of subvalvular or associated anomalies, early diagnosis, and timely intervention before the development of pulmonary hypertension or ventricular dysfunction. In well-managed cases, patients can lead entirely normal lives, with excellent exercise tolerance and very low arrhythmic risk.
Complications of congenital cleft of the mitral valve leaflets may arise from the natural progression of the malformation—particularly in untreated patients—or from the outcomes of surgical correction. Their incidence and severity are closely linked to the timeliness of diagnosis and the quality of the therapeutic strategy implemented.
In the natural course, the most frequent and clinically significant complication is progression of mitral regurgitation. An initially modest cleft may become hemodynamically significant over time, leading to left ventricular volume overload. This results in progressive dilation of the ventricle and left atrium, with structural changes that impair coaptation even of the remaining healthy leaflet segments, further worsening regurgitation. The ensuing vicious cycle may lead to secondary systolic dysfunction and development of chronic heart failure.
Another potentially severe complication, especially in uncorrected patients, is pulmonary hypertension. Chronic elevation of left atrial pressure is transmitted retrogradely through the pulmonary venous circulation, promoting pulmonary congestion, reduced exercise tolerance, and—at advanced stages—right ventricular dysfunction. The combination of mitral regurgitation with elevated pulmonary pressure significantly worsens the prognosis.
From an arrhythmic standpoint, left atrial dilation provides an anatomical substrate for the development of supraventricular tachyarrhythmias. Atrial fibrillation is the most common form, particularly in adolescents and young adults with untreated disease. It may initially be paroxysmal but can become chronic over time. This condition increases the risk of thromboembolism and impairs ventricular diastolic function, complicating clinical management.
Postoperative complications include the risk of residual mitral regurgitation and iatrogenic mitral stenosis. The former may occur if the cleft is incompletely closed or if valvular structures are damaged during surgery; the latter is rarer and may result from overly tight cleft closure or restricted leaflet mobility. In both cases, early and serial echocardiographic monitoring is essential to assess valvular function and determine the need for surgical revision.
Rare but possible complications include sinoatrial node dysfunction or atrioventricular conduction disturbances, particularly in patients with associated structural anomalies or after complex surgical procedures. In children, another critical issue is the need for reintervention during growth, especially when the initial repair does not account for future geometric changes in the mitral apparatus.
Finally, in patients with persistent atrial fibrillation or markedly dilated left atrium, personalized anticoagulation prophylaxis may be necessary to reduce thromboembolic risk. Management should be tailored to individual risk profiles, considering age, ventricular function, and other predisposing factors.
Overall, timely and technically appropriate treatment significantly reduces the risk of complications and ensures an excellent long-term quality of life. Nevertheless, active clinical and echocardiographic surveillance remains essential to detect early signs of functional deterioration or recurrence.