Congenital Mitral Leaflet Fissuration

Definition

Congenital mitral leaflet fissuration is a rare anomaly of the mitral valve characterized by discontinuities in the valve leaflets, ranging from small interruptions to more extensive fissures. This condition can compromise valve coaptation, leading to varying degrees of mitral regurgitation. While it can occur as an isolated anomaly, it is often associated with other congenital heart defects such as atrioventricular septal defect (AVSD), parachute mitral valve, or mitral valve prolapse.

Embryology and Pathogenesis

During fetal development, the mitral valve forms from the differentiation of the endocardial cushions, which give rise to the valve leaflets, chordae tendineae, and papillary muscles. An anomaly in the remodeling process of the mitral leaflets can lead to the persistence of congenital fissures, disrupting normal valve coaptation. The main hypothesized causes include:

• Defects in the fusion of endocardial cushions: May lead to abnormalities of the mitral valve and its supporting structures.
• Genetic mutations: Affect the development of collagen and elastin, resulting in structural alterations of the valve.
• Persistence of incomplete embryonic tissue bridges: Prevent the formation of a fully coapting mitral valve.

Pathophysiology

The presence of fissures in the mitral leaflets disrupts the valve closure mechanism, leading to varying degrees of mitral regurgitation. The main hemodynamic consequences include:

• Left ventricular volume overload: Due to blood reflux from the left atrium.
• Left atrial dilation: Caused by increased atrial pressure.
• Compensatory left ventricular hypertrophy: In cases of chronic mitral regurgitation.

In severe cases, fissuration may predispose to progressive heart failure and an increased risk of infective endocarditis due to the blood turbulence caused by regurgitation.

Clinical Manifestations

The clinical presentation of congenital mitral leaflet fissuration depends on the severity of the associated mitral regurgitation. In mild cases, the condition may be asymptomatic and diagnosed incidentally during an echocardiographic examination. In moderate to severe cases, the most common symptoms include:

• Exertional dyspnea: Due to increased left atrial pressure and pulmonary congestion.
• Early fatigue: Due to reduced cardiac output in cases with significant regurgitation.
• Palpitations: In cases of left atrial dilation, with possible development of atrial fibrillation.
• Systolic murmur: Due to mitral regurgitation, detectable on auscultation in the apical region.

In neonates and children with severe forms, the condition may present with tachypnea, feeding difficulties, and poor growth, typical signs of early heart failure.

Diagnosis

The diagnosis of congenital mitral leaflet fissuration relies on advanced imaging techniques:

• Transthoracic echocardiography with Doppler: First-line examination to identify fissuration and assess the associated mitral regurgitation.
• Transesophageal echocardiography: Particularly useful for a more detailed visualization of valve morphology in complex cases.
• Cardiac magnetic resonance imaging (CMR): Used in patients with uncertain valve anatomy or for ventricular function assessment.
• Cardiac catheterization: Reserved for cases with significant pulmonary hypertension or for a more detailed hemodynamic evaluation.

Treatment

The management of congenital mitral leaflet fissuration depends on the severity of mitral regurgitation and its hemodynamic impact on left ventricular function.

• Clinical monitoring: Indicated for asymptomatic patients with mild regurgitation.
• Medical therapy: In cases of moderate mitral regurgitation, beta-blockers and diuretics may be used to reduce pressure overload and improve symptoms.
• Mitral valve repair surgery: Recommended for symptomatic patients with severe regurgitation or progressive left ventricular dilation.
  • Direct fissure suturing
  • Valve remodeling with an autologous pericardial patch
  • Mitral valve replacement: In the most severe cases
• Transcatheter approach: In patients not eligible for traditional surgery, percutaneous mitral repair with clip implantation or edge-to-edge techniques may be considered.

Prognosis

The prognosis depends on the severity of the fissuration and its clinical management.

• In mild cases, the quality of life is excellent, with periodic cardiological follow-ups sufficient to monitor potential regurgitation progression.
• In severe cases, prognosis is closely linked to timely surgical intervention, which ensures long-term survival and restoration of valve function in symptomatic patients.

Conclusion

Congenital mitral leaflet fissuration is a rare valvular anomaly that can lead to progressive mitral regurgitation. Early diagnosis and timely intervention are essential to prevent complications and ensure a favorable prognosis.

Bigliografia
1. Carpentier A. et al. *Congenital anomalies of the mitral valve: Pathophysiology and surgical repair.* The Journal of Thoracic and Cardiovascular Surgery, 114(1), 1997, pp. 126-135.
2. McElhinney D. et al. *Mitral valve abnormalities in congenital heart disease: A comprehensive review.* Pediatric Cardiology, 27(1), 2006, pp. 56-71.
3. Shoji H. et al. *Echocardiographic assessment of mitral valve clefts and fissurations: Differentiation from mitral regurgitation.* Journal of the American Society of Echocardiography, 18(3), 2005, pp. 234-240.
4. David T. et al. *Surgical techniques for congenital mitral valve anomalies: Long-term outcomes and considerations.* Annals of Thoracic Surgery, 92(5), 2011, pp. 1765-1773.
5. Kumar K. et al. *Congenital mitral valve defects: Current perspectives on diagnosis and treatment.* International Journal of Cardiology, 268(1), 2018, pp. 102-108.
6. Vahanian A. et al. *2021 ESC/EACTS Guidelines for the management of valvular heart disease.* European Heart Journal, 43(7), 2022, pp. 561-632.
7. Gaynor J. et al. *Congenital mitral valve anomalies: Surgical outcomes and considerations.* Journal of Thoracic and Cardiovascular Surgery, 141(1), 2011, pp. 99-107.
8. Friedman K. et al. *Congenital mitral valve disease in infants and children: Clinical implications and surgical strategies.* The Annals of Thoracic Surgery, 88(5), 2009, pp. 1486-1493.
9. Ruckman R. et al. *Congenital mitral stenosis and regurgitation: An echocardiographic approach.* Circulation, 68(1), 1983, pp. 135-146.
10. Langley S. et al. *Surgical repair of congenital mitral clefts and fissurations: Techniques and outcomes.* The Journal of Heart Valve Disease, 15(4), 2006, pp. 453-459.