Understanding Tricuspid Atresia and Pulmonary Hypertension

Tricuspid atresia is a rare congenital heart defect where the tricuspid valve is absent. This can present as a blue or purple hue on the skin- this is called cyanosis.¹ This is when there is no communication between the ventricle and the right atrium due to complete agenesis (the failure of an organ to develop during embryonic growth) of the tricuspid valve. Pulmonary hypertension occurs when there is high blood pressure in the lungs, and this causes the heart to work much harder than normal to pump blood into both lungs. Tricuspid atresia can ultimately result in pulmonary hypertension due to the missing valve, and this causes an increase in pressure within the pulmonary arteries.

What is Tricuspid Atresia?

The tricuspid valve is located between the right atrium and the right ventricle. Its role is to make sure that the blood flows in a forward direction. Tricuspid atresia is a mixed blood flow congenital heart defect where there is a complete closure of the tricuspid valve due to it being missing or underdeveloped. This means that there is a solid sheet of tissue that prevents blood flow between the right atrium and the right ventricle. To compensate for the tricuspid valve, the blood is rerouted via natural openings in the heart, like the ventricular septal defect (VSD) or the atrial septal defect (ASD). However, this causes cyanosis in patients.² Patients with tricuspid atresia often have surgeries such as the Fontan procedure, which helps reroute the blood flow directly from the heart into the lungs.³

What is Pulmonary hypertension?

When blood pressure in the arteries of the lung is too high, this causes a condition called pulmonary hypertension (PH). Blood is carried from the heart to the lungs to become oxygenated, so when there is an increase in pressure in the blood vessels, the heart works harder to allow blood to flow through the arteries.⁴ Due to the increase in pressure, this can result in weakening of the heart and a reduction in oxygen delivery to the body.⁵ Pulmonary hypertension over time causes symptoms such as fatigue, shortness of breath, and swelling in the legs. When this condition is left untreated, it can lead to heart failure in some cases. Conditions such as tricuspid atresia, where there are abnormal blood flow patterns and increased strain on the heart, can contribute to the development of pulmonary hypertension.

Mechanism of pulmonary hypertension

When the elevated mean pulmonary arterial pressure is greater than 20mmHg at rest, it indicates that a patient could have pulmonary hypertension. If left untreated, this could lead to heart failure. One key mechanism of pulmonary hypertension is endothelial dysfunction. This is when there is an imbalance of a vasoconstrictor (a substance that causes blood vessels to narrow) and a vasodilator (a substance that causes blood vessels to dilate), which causes vasoconstriction as well as inflammation.⁷ When this occurs, there is luminal narrowing and arterial stiffening. Another mechanism that leads to the development of pulmonary hypertension is vascular remodelling (changes in the size, shape, and structure of blood vessels), which is driven by smooth muscle hypertrophy (enlargement of smooth muscle).⁶ This causes structural changes in the pulmonary arteries, such as the vessel walls thickening and the lumen narrowing. This causes an increase in resistance to blood flow and increases pressure within the pulmonary circulation. Over time, this leads to pulmonary hypertension.

Symptoms and diagnosis:

Some common symptoms of pulmonary hypertension for patients with tricuspid atresia are:

• Chest pain or discomfort
• Cyanosis
• Fatigue
• Swelling (typically fluid buildup in the leg or abdomen)
• Dizziness

Doctors can diagnose pulmonary hypertension in tricuspid atresia patients by using several tests that assess the heart function as well as the lungs:

• Echocardiogram- a painless ultrasound scan which produces moving images of the heart and examines the function and structure of the heart and blood vessels⁷
• Cardiac MRI
• Chest X-ray

Treatment and management options

Surgical interventions

The majority of patients with tricuspid atresia require a form of surgical treatment in their early years of life. An indicator for patients who require early surgical intervention is cyanosis with decreased pulmonary blood flow, where a ‘shunt procedure’ is performed to connect the systemic circulation to the pulmonary circulation. One shunt example is the Blalock-Taussig shunt. This is where the shunt is from the subclavian artery to the pulmonary artery.⁹ In cases where patients have an increased pulmonary blood flow, pulmonary artery banding is performed to decrease the flow to the lungs and help assist with treatment.

Treatment to manage symptoms of pulmonary hypertension can be given as a combination of treatments and is prescribed by your doctor depending on different factors. A list of treatments includes:

• Anticoagulant medications – these medications help prevent blood clots and are given to patients with a high risk of having a stroke. Warfarin is a commonly prescribed anticoagulant
• Diuretics – aid in removing excess fluid from the body that is caused by heart failure
• Digoxin – prescribed to control some heart conditions and helps manage symptoms of heart failure. Its function is to slow down the heart rate to make the heart beat strongly
• Home oxygen therapy - using a mask or tube connected to a device at home to breathe in more oxygen

Alternative medications that can be prescribed to help manage symptoms of pulmonary hypertension:

• Calcium channel blockers – amlodipine
• Soluble guanylate cyclase stimulators - riociguat
• Prostaglandins – epoprostenol 

Living with pulmonary hypertension and tricuspid atresia

Having both pulmonary hypertension and tricuspid atresia can have its own challenges for an individual; however, with the right management, patients can have a good quality of life. For both pulmonary hypertension and tricuspid atresia, blood flow and oxygen delivery are affected, meaning patients will experience fatigue, shortness of breath, and have low tolerance to exercise. It is very important to maintain a healthy lifestyle for these patients by engaging in low-intensity exercise and having a diet that is tailored to increase heart health as well. 

Summary

Tricuspid atresia is a rare heart defect where the tricuspid valve is missing, causing poor blood flow between the heart’s chambers and leading to low oxygen levels (cyanosis). Over time, this can result in pulmonary hypertension, a condition where high blood pressure in the lungs makes the heart work harder. Symptoms include fatigue, shortness of breath, and swelling. Diagnosis is done through heart imaging tests, and treatment often involves surgery, medications, and oxygen therapy. With proper care and a healthy lifestyle, patients can still maintain a good quality of life.

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