<aside>
Cyanotic congenital heart diseases (CCHDs) are structural cardiac anomalies present at birth that result in a right-to-left shunt, allowing deoxygenated blood to bypass the lungs and enter systemic circulation, leading to cyanosis (bluish discoloration of skin and mucosa due to hypoxemia).
</aside>
Mnemonic: The “5 Ts” of Cyanotic CHD
| Condition | Description |
|---|---|
| 1. ‣ | VSD + RV outflow obstruction + overriding aorta + RV hypertrophy |
| 2. ‣ | Aorta arises from RV; pulmonary artery from LV → parallel circulation |
| 3. ‣ | Single arterial trunk for systemic, pulmonary, and coronary circulation |
| 4. ‣ | No tricuspid valve → hypoplastic RV; must have ASD and VSD for survival |
| 5. ‣ | All pulmonary veins drain to RA or systemic vein |
Other causes:
Mechanisms of Cyanosis:
| Pathophysiologic Mechanism | Examples |
|---|---|
| Right-to-left shunt | Tetralogy of Fallot, Eisenmenger syndrome, TGA |
| Mixing of oxygenated and deoxygenated blood | Truncus arteriosus, TAPVR |
| Pulmonary outflow obstruction with shunting | Tricuspid atresia, pulmonary atresia |
| Feature | Description |
|---|---|
| Cyanosis | Central (lips, tongue), often noticed in newborns |
| Tachypnea, dyspnea | From reduced pulmonary blood flow or pulmonary edema |
| Failure to thrive | Poor feeding, weight gain |
| Clubbing | Seen in older children with chronic hypoxia |
| "Tet spells" | Hypoxic episodes in ToF relieved by squatting |
| Murmurs | Vary by lesion (e.g., systolic ejection murmur in ToF) |