Question:
Which of the following types of TAPVC is least common?
Which of the following types of TAPVC is least common?
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TAPVC Frequencies: Supracardiac ($50\%$, most common) $>$ Cardiac ($20\%$) $=$ Infracardiac ($20\%$, highest rate of obstruction) $>$ Mixed ($5-10\%$, least common).
Updated On: Sep 3, 2026
- Mixed
- Cardiac TAPVC
- Infracardiac
- Supracardiac
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The Correct Option is A
Solution and Explanation
Concept:
The clinician is required to recall the standard anatomical classification and the relative epidemiological frequencies of the various subtypes of Total Anomalous Pulmonary Venous Connection (TAPVC).
Explanation:
• Total Anomalous Pulmonary Venous Connection (TAPVC) is a cyanotic congenital heart defect where all four pulmonary veins fail to connect to the left atrium. Instead, they drain erroneously into the systemic venous circulation, mixing oxygenated and deoxygenated blood in the right atrium. An obligatory Right-to-Left shunt (usually an ASD or patent foramen ovale) is required for survival.
• TAPVC is anatomically classified into four distinct subtypes based on the exact site where the anomalous pulmonary veins drain into the systemic circulation.
• 1. Supracardiac (Type I): This is the most common type, accounting for approximately $50\%$ of all cases. The pulmonary veins converge into a confluence that drains upwards into a vertical vein, which joins the innominate vein and eventually the Superior Vena Cava (SVC).
• 2. Cardiac (Type II): Accounts for about $20\%$ of cases. The pulmonary veins empty directly into the right side of the heart, most frequently into the Coronary Sinus or directly into the right atrium.
• 3. Infracardiac (Type III): Accounts for about $20\%$ of cases. The pulmonary veins converge and travel downwards below the diaphragm, typically inserting into the Portal Vein or Inferior Vena Cava (IVC). This type is notorious for severe venous obstruction.
• 4. Mixed (Type IV): This is the least common type, accounting for only $5\%$ to $10\%$ of all cases. It occurs when there is a combination of two or more of the above drainage patterns (e.g., the left lung drains supracardiac, and the right lung drains cardiac).
Final Answer:
The mixed variant is statistically the rarest anatomical configuration of TAPVC.
The clinician is required to recall the standard anatomical classification and the relative epidemiological frequencies of the various subtypes of Total Anomalous Pulmonary Venous Connection (TAPVC).
Explanation:
• Total Anomalous Pulmonary Venous Connection (TAPVC) is a cyanotic congenital heart defect where all four pulmonary veins fail to connect to the left atrium. Instead, they drain erroneously into the systemic venous circulation, mixing oxygenated and deoxygenated blood in the right atrium. An obligatory Right-to-Left shunt (usually an ASD or patent foramen ovale) is required for survival.
• TAPVC is anatomically classified into four distinct subtypes based on the exact site where the anomalous pulmonary veins drain into the systemic circulation.
• 1. Supracardiac (Type I): This is the most common type, accounting for approximately $50\%$ of all cases. The pulmonary veins converge into a confluence that drains upwards into a vertical vein, which joins the innominate vein and eventually the Superior Vena Cava (SVC).
• 2. Cardiac (Type II): Accounts for about $20\%$ of cases. The pulmonary veins empty directly into the right side of the heart, most frequently into the Coronary Sinus or directly into the right atrium.
• 3. Infracardiac (Type III): Accounts for about $20\%$ of cases. The pulmonary veins converge and travel downwards below the diaphragm, typically inserting into the Portal Vein or Inferior Vena Cava (IVC). This type is notorious for severe venous obstruction.
• 4. Mixed (Type IV): This is the least common type, accounting for only $5\%$ to $10\%$ of all cases. It occurs when there is a combination of two or more of the above drainage patterns (e.g., the left lung drains supracardiac, and the right lung drains cardiac).
Final Answer:
The mixed variant is statistically the rarest anatomical configuration of TAPVC.
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