Paper I
2014 September (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Rationale for the use of nitrates in angina pectoris.

Q111 marksShort Answers

Answer

Nitrates release nitric oxide, which activates guanylyl cyclase, increasing cGMP and causing smooth muscle relaxation. At therapeutic doses they cause predominant venodilatation, reducing venous return (preload) and hence left ventricular wall tension and myocardial oxygen demand. They also produce some arteriolar dilatation (↓afterload) and dilate epicardial coronary arteries/collaterals, improving coronary blood flow to ischaemic areas. This combination of reduced myocardial oxygen demand and improved oxygen supply relieves anginal pain.

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