Let’s talk about blue babies — not because they’re fans of Avatar, but because of cyanotic congenital heart diseases (CCHDs). These are the right-to-left shunt monsters that sneak past pulmonary circulation and dump deoxygenated blood straight into systemic circulation. Result? Central cyanosis, clubbing, and an anxious house officer with a pulse oximeter they trust more than their own judgment. 😅
I still remember my first cyanotic baby at Sheikh Khalifa Bin Zayed Hospital — oxygen saturation in the 70s, dusky lips, and a cardiac murmur that could wake the dead. It was Tetralogy of Fallot, of course (the class topper of the 5 T’s). But to avoid mixing them up — especially under exam stress or NICU panic — we use the legendary mnemonic: the famous 5 T’s.
Cyanotic Congenital Heart Disease Mnemonic
| Mnemonic | Condition | Key Feature |
|---|---|---|
| T | Truncus Arteriosus | One big trunk instead of two vessels — single outflow tract 🌲 |
| T | Transposition of the Great Arteries | Aorta and PA switch places — parallel circuits 🚧 |
| T | Tricuspid Atresia | No tricuspid valve — right atrium can’t talk to RV 🛑 |
| T | Tetralogy of Fallot | Four-in-one combo meal: VSD + RVH + Overriding Aorta + Pulmonary Stenosis 🍔 |
| T | Total Anomalous Pulmonary Venous Return | Pulmonary veins drain into systemic veins — lungs work overtime with no reward 🌀 |
🧠 Quick Clinical Pearls & Dry Wit:
🔹 Truncus Arteriosus
“One heart, one love” — unfortunately, one arterial trunk as well. Instead of a separate aorta and pulmonary artery, there’s a single common outflow tract. Think of it as a plumbing disaster — both oxygenated and deoxygenated blood are thrown together into a common tube. Needs surgical separation before the baby turns into a smurf.
🔹 Transposition of the Great Arteries (TGA)
This one gives med students nightmares. You’ve got two closed circuits, and unless there’s a VSD/ASD/PDA to mix the blood, the baby won’t survive. It’s like putting the return fuel pipe into the air intake. We had one neonate in our CCU who had sat O₂ of 50% despite high-flow O₂. Turned out to be classic TGA — prostaglandin drip and balloon atrial septostomy saved the day. 🏥
🔹 Tricuspid Atresia
When tricuspid valve is MIA, the right atrium gets ghosted by the right ventricle. Blood has to sneak into the left side through an ASD, then maybe drop in on the RV via a VSD (if it exists). This is an introvert of a heart lesion — no direct communication, just subtle shunting.
🔹 Tetralogy of Fallot (TOF)
Ah yes, the MCQ favorite and my personal favorite. Cyanotic spells, squatting toddler, boot-shaped heart. The classic “pink-toddler-turned-blue-during-crying” scenario. Every time I hear a murmur with a harsh crescendo-decrescendo over the LUSB in a cyanotic kid, TOF is at the top of my list. 🩺
And let’s not forget: these kids are born gymnasts — they instinctively squat to increase systemic vascular resistance and reduce the shunt.
🔹 Total Anomalous Pulmonary Venous Return (TAPVR)
You’d think after all that hard work in the lungs, pulmonary veins would know where to go. But nope — they drain into the wrong atrium or systemic veins entirely. “Thanks for the oxygen, now let’s send it back to where it came from.” 🙄 Obstructed TAPVR is a surgical emergency. No mixing means no fixin’.
💬 Clinical Tip from the Wards
Always suspect a cyanotic CHD if saturations are low and don’t improve with 100% oxygen (aka the “hyperoxia test”). It’s your clinical detective moment. 🕵️♂️
🩺 Want more blog posts like this? Or maybe a breakdown of acyanotic heart defects next? Let me know — no murmurs about it. 😉
Happy learning, folks! 🙂
👨⚕️ Written by
Dr. Aurangzaib Qambrani
MBBS, PLAB, MRCP-UK
General Medicine | Gastroenterology | Cardiac Care Unit
Sheikh Khalifa Bin Zayed Hospital, Quetta
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