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Coronary Artery Anatomy

Left coronary Arises from left posterior aortic sinus (worse prognosis if stenosed)	Right coronary Arises anterior aortic sinus
Sinoatrial nodal (40%) Circumflex Left marginal (obtuse marginal) Left conus Posterior interventricular artery (PDA - posterior descending artery) Left anterior descending Left conus Diagonal Ventricular + septal	Left atrial Right conus SA nodal (60%) Right atrial Right marginal Posterior interventricular artery (PDA) Ventricular branches Septal branches AV nodal (90%)

Internal structure of the heart

Coronary blood flow

• 70-80mls/min per 100g cardiac muscle
• High blood flow per unit weight of myocardium
• 70% oxygen extraction (compared to 25% for the rest of the body)
• Efficient metabolic hyperaemia - myocardial metabolites generated have strong (positive) influence on coronary blood flow
• Greatest during diastole, lowest flow is during isovolumetric (systolic) contraction - due to compression of artery

Control of Coronary blood flow

1. Metabolic
   • CO2, PGs, Adenosine produce vasodilation
2. Neural
   • B2 stimulation causes coronary vasodilation
3. Autoregulation: between 60-180mmHg [See CPP]
   • Myogenic theory - increase in pressure stimulates stretch receptors which causes reflex vasoconstriction increasing pressure despite rising pressure
   • Vasodilator washout - transient arteriorlar dilation following rise in perfusion pressure due to wash out of vasodilators