Tricuspid atresia

Key takeaways

Tricuspid atresia belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Tricuspid atresia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Tricuspid atresia from memory before moving on to harder problems.

Reference excerpt

Tricuspid atresia is a form of congenital heart disease whereby there is a complete absence of the tricuspid valve. Therefore, there is an absence of right atrioventricular connection. This leads to a hypoplastic (undersized) or absent right ventricle. This defect occurs during prenatal development, when the heart does not finish developing. It causes the systemic circulation to be filled with relatively deoxygenated blood. The causes of tricuspid atresia are unknown. In most cases of tricuspid atresia, additional defects exist to allow exchange of blood between the loops of systematic circulation and pulmonary circulation, filling in the role of the missing atrioventricular connection. An atrial septal defect (ASD) must be present to fill the left atrium and the left ventricle with blood. Since there is a lack of connection to the right ventricle, there must also be a way to pump blood into the pulmonary artery. This can be accomplished by a ventricular septal defect (VSD) connecting the left ventricle to the pulmonary artery or by a patent ductus arteriosus (PDA) connecting the aorta to the pulmonary artery. In the latter case, prostaglandin E1 is used to maintain the PDA connection until emergency corrective surgery can be completed. As oxygenated blood is mixed with deoxygenated blood in both cases, there is a reduction in the oxygen-carrying capacity. It is also possible for tricuspid atresia to appear without the life-saving defects. In this case, the systemic and pulmonary circulations would be cut off from each other and no useful breathing can occur. An experimental procedure called fetal balloon atrial septostomy can be used to artificially create the required defect in utero.

Presentation progressive cyanosis poor feeding tachypnea over the first 2 weeks of life holosystolic murmur due to the VSD left axis deviation on electrocardiography and left ventricular hypertrophy (since it must pump blood to both the pulmonary and systemic systems) Normal or mildly enlarged heart Abnormal heart sounds such as the splitting of the S2 heart sound and an S3 at the cardiac apex may be heard.

Cause Tricuspid atresia is caused by complete absence of the tricuspid valve. The underlying cause of this absence remains unknown. This prevents direct blood flow between the right atrium and the right ventricle. This usually causes the foramen ovale to remain open after birth, leading to atrial septal defect.

Pathophysiology As there is no communication between the right atrium and the right ventricle, there must be an atrial septal defect to allow blood to flow into the left cardiac chambers. Due to the lack of blood flow into the right ventricle, it will be hypoplastic. In most cases, there will also be a ventricular septal defect allowing some blood into the pulmonary circulation. Due to the lack of blood flow into the pulmonary circulation, there is poor oxygenation of blood, leading to progressively worsening cyanosis.

Diagnosis The majority of cases can be diagnosed prenatally during a routine anomaly scan. If evidence of a congenital heart disease is found, the diagnosis can be confirmed by a foetal echocardiogram. If it is not diagnosed prenatally, it may be diagnosed shortly after birth with physical examination, which would reveal cyanosis and murmur. Further evidence for the diagnosis can be obtained with an electrocardiogram and a chest radiograph. ECG will typically show a left axis deviation, while the chest X-ray may show pulmonary oligaemia or hyperaemia. The definitive investigation is, as in all congenital heart diseases, an echocardiogram, although the aforementioned tests along with clinical features might be sufficient for most cases.

Treatment Treatment is based on:

PGE1 to maintain patent ductus arteriosus. First operation: modified Blalock-Taussig shunt to maintain pulmonary blood flow by placing a Gore-Tex conduit between the subclavian artery and the pulmonary artery. See also Norwood procedure. Where too much flow to the lungs is present, a pulmonary band may be placed in a first operation. Second operation: cavopulmonary anastomosis (hemi-Fontan or bidirectional Glenn) to provide stable pulmonary flow Final operation: Fontan procedure to redirect inferior vena cava and hepatic vein flow into the pulmonary circulation.

Epidemiology Tricuspid atresia is the third most common critical congenital heart defect. It is estimated to cause between 1% and 3% of all congenital heart defects.

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Tricuspid atresia

Start with the simplest possible case. Write down what Tricuspid atresia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tricuspid atresia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tricuspid atresia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tricuspid atresia

In research: Tricuspid atresia appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tricuspid atresia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tricuspid atresia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Congenital heart defects, so understanding it makes those chapters shorter.
In everyday life: Look for Tricuspid atresia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Tricuspid atresia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tricuspid atresia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Tricuspid atresia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Tricuspid atresia in simple terms?

Tricuspid atresia is a form of congenital heart disease whereby there is a complete absence of the tricuspid valve. Therefore, there is an absence of right atrioventricular connection.

Why does Tricuspid atresia matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tricuspid atresia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tricuspid atresia.