Coronary Circulation

Current · V5 (2025) → D4.iv Historical · V4 (2023) → G1.ii 6 exam appearances

2026B Q13

Exam question

With respect to the adult coronary circulation:
a) State the normal resting coronary blood flow, including appropriate units (5% of marks)
b) Describe the anatomy of the coronary arteries including the regions of the heart they supply (20% of marks)
c) Describe the flow characteristics of the coronary arteries (15% of marks)
d) Briefly outline the venous drainage of the myocardium (10% of marks)
e) Describe the regulation of coronary perfusion (50% of marks)

CICMWrecks answer

Master answer

Arteries

LCA to
- LCx to
  - OM1
  - OM2
- LAD has branches
  - Diagonal 1 or 2
RCA
- Right Ventricular
- Acute Marginal
- Posterior descending

Veins

Great, small, middle
Drain into the thebesian veins → ventricles directly
Empty into the coronary sinus on the posterior wall or the RV

Regional Supply

Artery	Anatomical region	ECG abnormality on occlusion
RCA	Down Anterior aspect of the heart, right of the pulmonary trunk Supplies RA SAN and AVN Posterior IVS	RCA occlusion causes → inferior: 2,3 aVF → true posterior: tall R in V1
LCA	Left coronary artery ostia adjacent to left leaflet → Left Main → LCx and LAD Supplies LA, LV IVS AV Bundles	LCA occlusion → Lateral: 1, aVL, V1-V6
LCx	LA and superior LV	anterolateral leads (1, aVL, V5 and V6)
LAD	RV, LV Anterior 2/3rds Interventricular Septum	Anteroseptal (V1 and V2) Anteroapical (V3 and V4) with some RCA supply.
Left Marginal	The continuation of the LCA after LAD branch Supplies LV laterally	Isolated Abnormalities rare V5, V6
Right Marginal	The anterior branch of the RCA along the inferior border Supplies right ventricle and apex	Isolated Abnormalities rare RCA occlusion causes 2,3 aVF

Coronary Blood Flow

80 mL/min/100 g
or 200-250 mL/min
5% of CO at rest
Can increase by 3-4 times (up to 400mL/min/100g)

High Extraction Ratio

High at rest (55-65%) body average of 25%

Extraction ratio can only rise by factor of < 2 to 90%
AV Δ O₂ = 11 mL/dL
Coronary venous O₂ content = 5 mL/dL
Coronary sinus SpO₂= 20mmHg

Phasic coronary blood flow across the cardiac cycle

Coronary perfusion pressure (CPP)

CPP \; = \; ADP \; – \; (larger \; of \; LVEDP \; or \; RAP)

ADP = Ao Diastolic Prssure
- It is different throughout the cycle and b/w ventricles

Phasic Supply as per diagram.

Determinants of Coro BF

Physical Factors
- Extravascular compression (CPP factors)
Neural and Neurohumoral Factors
- ↑ SNS tone →
  - α receptor mediated vasoconstriction
  - β receptor mediated vasodialtion
  - ↑ force and rate of contractions → ↑ vasodialtor metabolite release
  - Overall effect is dilation
- ↑ PSNS tone → KACh stimulation → mild ↓ Coronary vascular resistance
Metabolic Factors (main)
- Vasodilatory
  - ↑ Adenosine, H, K, CO2, Lactate
  - NO → GTP
  - ↑ O2 demand → ↓ ATP → ↑KATP channel activation → hyperpolarisation → vasodilation
Myogenic autoregulation (keep CPP 60-180 mmHg)

Gladwin 2016

Reusable content

Formulae used in this answer

Coronary Perfusion Pressure

CWF-0094

CPP \; = \; ADP \; - \; (larger \; of \; LVEDP \; or \; RAP)

Answer by Gladwin

Quick reference

Summary

Coronary circulation	Key point
Resting flow	≈250 mL/min, about 4–5% of cardiac output (≈70–80 mL/100 g/min)
Anatomy	RCA and LCA arise from aortic sinuses; LCA → LAD + circumflex; dominance defined by origin of PDA
Flow	LV coronary flow is predominantly diastolic because systolic myocardial compression impedes flow; RV flow is more continuous
Venous drainage	Mostly via coronary sinus to RA; anterior cardiac and Thebesian veins provide additional drainage
Regulation	High resting O2 extraction means increased demand is met mainly by increased flow; local metabolic control dominates (adenosine, hypoxia, K+, H+, CO2, NO) with autoregulatory and neural modulation

Past papers

Exam appearances

6 appearances

Exam	Exact exam wording	Candidate success
2026B Q13	With respect to the adult coronary circulation: a) State the normal resting coronary blood flow, including appropriate units (5% of marks) b) Describe the anatomy of the coronary arteries including the regions of the heart they supply (20% of marks) c) Describe the flow characteristics of the coronary arteries (15% of marks) d) Briefly outline the venous drainage of the myocardium (10% of marks) e) Describe the regulation of coronary perfusion (50% of marks)	—
2023A Q15	Describe the adult coronary circulation (50% of Marks) and its regulation (50% of Marks).	66%
2021A Q19	Describe the adult coronary circulation (50% marks) and its regulation (50% marks).	62%
2018A Q11	Describe the regulation of the coronary circulation.	46%
2014B Q10	Describe the adult coronary circulation (50% of marks) and its regulation (50% of marks).	65%
2008B Q11	Describe the adult coronary circulation (50% of marks). Describe the physiological control of the coronary circulation (50% of marks).	—