Mitral Atresia: Valvular Birth Defect of the Bicuspid

What Is Mitral Atresia?

Mitral atresia is a congenital defect of the mitral valve. The mitral valve, also known as the bicuspid valve, is between the left ventricle and the left atrium. In mitral atresia, the valve is either completely closed or absent altogether. The function of the mitral valve is to allow the passage of oxygenated blood from the left atrium to the left ventricle, from which it travels through the aorta and reaches the body organs during the heart’s relaxation phase.

The valve also prevents the backflow of blood from the ventricle to the atrium in the contraction phase. This is primarily associated with mal-aligned ventricular septum with or without mal-aligned atrial septum, atrioventricular canal defect, and excessive growth of the endocardial cushion. The condition is often associated with other congenital heart defects like:

• Patent ductus arteriosus (persistent opening between the two major blood vessels leading from the heart).

• Coarctation of the aorta (narrowing of the aorta).

• Transposition of the great arteries (pulmonary artery and the aorta – are switched in position).

• Pulmonary stenosis (pulmonary valve is too narrow).

• Shunt defects (atypical pattern of blood flow through your heart).

• Cor triatriatum (left or right atrium is subdivided by a thin membrane, resulting in three atrial chambers).

• Chamber.

• Valvular anomalies.

What Causes Mitral Atresia?

Mitral atresia is a rare occurrence and is found in approximately one in 10,000 live births. Although the exact cause of the developmental anomaly is yet to be determined, it is hypothesized to result from a combination of various genetic and environmental factors. Some researchers also hypothesize that the anomaly develops as a result of maternal infections or teratogenic medications. These factors also act as events that increase the risk of developing mitral atresia. Eighty percent of cases are seen in association with larger ventricular anomalies, including hypoplastic left heart syndrome, left ventricular outflow tract obstruction, and double-outlet right ventricle.

What Are the Clinical Features of Mitral Atresia?

The clinical entities of mitral atresia vary according to the severity of the condition, along with other factors (both genetic and environmental), like the presence of other cardiac defects. Some of the common symptoms include:

• Cyanosis (bluish skin due to poor oxygen saturation).

• Shortness of breath.

• Fatigue.

• Lethargy.

• Rapid breathing (tachypnea).

• Poor nutrition.

• Slow weight gain.

• Clubbing to fingers and toes.

• Chest pain.

• Chest discomfort.

• Arrhythmias (irregular cardiac rhythm).

• Abnormal heart sounds.

• Difficulty feeding.

How to Diagnose Mitral Atresia?

If the doctor suspects a heart defect, not just mitral atresia, a team of experts performs necessary examinations, both physical and cardiac-specific tests. Primarily, breath sounds and heartbeats are analyzed, along with evaluating signs of oxygen deprivation in the form of cyanosis. Some of the possible findings of a physical examination include:

• Tachycardia (above 150 bpm).

• Displacement of the apex.

• Grade three systolic murmur in first, second, and third heart sounds.

• Tachypnoeic (respiratory cycles above 50 per minute).

• Low oxygen saturation (below 85 percent and may improve on intubation).

Following this, additional tests may be ordered to confirm a diagnosis. These tests include:

• Chest Radiograph: Chest X-rays may show a variable degree of cardiomegaly (heart enlargement).

• Echocardiogram: This uses sound waves to paint a picture of the heart and its valves while functioning. This is used to visualize mitral defects. The great vessels may be normally positioned. Some echo findings may include a hypoplastic left ventricle, right ventricular hypertrophy, and the aortic arch on the left side.

• Electrocardiogram (ECG): ECG shows any anomaly in the heart's electrical activity. The track may show sinus tachycardia.

• Cardiac Catheterization: This is an invasive test involving the introduction of a flexible tube into an artery and guided to the heart. This can help evaluate the blood flow and pressure within the heart and detect and confirm any structural anomaly like mitral atresia or any additional defect accompanying mitral atresia.

• Cardiac MRI: Another test that may be performed is a cardiac MRI (magnetic resonance imaging). However, cardiac MRI and catheterization may not be necessary as echo studies can provide sufficient evidence for the diagnosis and pathophysiological analysis.

How to Treat Mitral Atresia?

The treatment is tailored to meet the patient’s condition, and it depends mainly on the severity and overall health of the baby. Sometimes, conservative therapies may be sufficient to manage the abnormality, while in some cases, surgical interventions may be required.

Pharmacotherapeutics involves prescriptions of diuretics, vasopressors, and antibiotics. Supportive therapies may include oxygen and mechanical ventilation.

Surgical interventions may be required in deteriorating cases or patients with high anomaly severity. Shunts and staged corrective surgeries are planned and performed, but sometimes they may require further more complex surgeries. In most rare cases, a complete heart transplant may just be the only way to save the patient.

However, that road is long and requires specific criteria to be fulfilled even to get listed in the UNOS (United Network for Organ Sharing) list. The list is dynamic, and finding a match is like searching for a needle in a haystack. Multiple parameters like blood typing, tissue typing, and cross-matching must be satisfied in both donor and recipient to schedule a transplant.

What Are the Complications of Mitral Atresia?

• Heart failure (inability of the heart to pump blood efficiently).

• Arrhythmias (irregular heartbeat).

• Cyanosis.

• Thrombosis (clotting within the vessels).

• Stroke (damage to the brain due to insufficient blood supply).

• Pulmonary embolism (pulmonary arteries get blocked by a clot).

Conclusion

Mitral atresia is a congenital heart anomaly that affects the structure and function of the bicuspid valve, which guards the passage of the left chambers. The condition, untreated or undiagnosed, can precipitate a range of complications or may even cause death in infants with severe anomalies. Almost four-fifths of the reported cases are accompanied by several other cardiac anomalies; hence, the patients may require a much higher degree of care and a great many hours in the operation theater. Regular checkups with concerned specialists and medical teams, stringent compliance with medication, and a medically chartered lifestyle can help improve the quality of life. It is of utmost importance to seek medical help immediately if one notices any symptoms or worsening of general health.