Cyanosis of tetralogy of Fallot is mainly due to:

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Cyanosis of tetralogy of Fallot is mainly due to: Answer: Pulmonary stenosis

Pulmonary stenosis or right ventricular outflow obstruction is the major factor determining the degree of right-to-left shunting in tetralogy of Fallot. Greater obstruction directs more deoxygenated blood through the ventricular septal defect into systemic circulation, producing cyanosis.

Question context

This question is part of 🧫 Biotechnology within the broader 🧬 Medical Science subject and appears in the SPSC – Sindh Public Service Commission preparation collection. Reviewing the answer together with nearby questions helps reinforce the underlying concept and identify how it may appear in competitive exams.