Regarding the surgical management and hemodynamic changes in Tetralogy of Fallot, all of the following are true EXCEPT:

## Hemodynamic Changes in TOF Surgery ### Pre-Repair Hemodynamics **Key Point:** In uncorrected TOF, the Qp:Qs (pulmonary:systemic blood flow ratio) is **less than 1** because blood preferentially shunts R→L, reducing pulmonary perfusion. $$\text{Qp:Qs} = \frac{\text{Pulmonary blood flow}}{\text{Systemic blood flow}} < 1 \text{ in TOF}$$ ### Post-Repair Hemodynamics **High-Yield:** After complete surgical repair (VSD closure + RVOT relief): - R→L shunt is abolished - All systemic venous return goes to lungs - All pulmonary venous return goes to systemic circulation - **Qp:Qs becomes equal to 1** (not less than 1) The statement "QpQs ratio becomes less than 1" is **FALSE** because successful repair eliminates the R→L shunt entirely, normalizing the ratio to 1:1. ### Palliative vs. Definitive Surgery | Procedure | Type | Goal | Mechanism | | --- | --- | --- | --- | | Blalock-Taussig shunt | Palliative | Increase Qp, reduce cyanosis | Systemic artery (subclavian/innominate) to PA anastomosis | | VSD closure + RVOT relief | Definitive | Eliminate R→L shunt, normalize circulation | Close VSD, relieve pulmonary stenosis (infundibulotomy ± patch) | **Clinical Pearl:** The Blalock-Taussig shunt is a temporizing procedure used in neonates/infants with severe cyanosis awaiting definitive repair. It increases pulmonary blood flow by creating an artificial left-to-right shunt, thereby improving oxygenation. ### Long-Term Sequelae After Complete Repair 1. **Pulmonary regurgitation** — most common (up to 80% of patients) - Caused by RVOT patch or infundibulotomy - Progressive RV dilatation over decades - May eventually require pulmonary valve replacement 2. **Residual VSD** — if repair incomplete 3. **RV dysfunction** — from chronic pressure/volume overload 4. **Arrhythmias** — scar-related reentry 5. **Aortic regurgitation** — if aortic root involved **Mnemonic: POST-REPAIR COMPLICATIONS = PRAVA** - **P**ulmonary regurgitation - **R**esidual VSD - **A**ortic regurgitation - **V**entricular arrhythmias - **A**ortic root dilatation [cite:Moss & Adams Heart Disease in Infants, Children, and Adolescents 9e Ch 42; Anderson & Macartney Pediatric Cardiology Ch 35]