Coronary Circulation

Question 2

What is the main artery supplying the myocardium?

Answer 2

Coronary arteries

Question 3

From where do the coronary arteries arise?

Answer 3

They arise from the ascending aorta, just above the aortic valve (sinuses of Valsalva)

Question 4

What are the two main coronary arteries?

Answer 4

Left coronary artery (LCA) and right coronary artery (RCA)

Question 5

What are the branches of the left coronary artery?

Answer 5

Left anterior descending (LAD), circumflex artery

Question 6

What are the branches of the right coronary artery?

Answer 6

Right marginal artery, posterior descending artery (PDA)

Question 7

Which part of the heart does the LAD artery supply?

Answer 7

Anterior wall of LV, anterior 2/3 of interventricular septum, apex

Question 8

Which part of the heart does the circumflex artery supply?

Answer 8

Lateral and posterior walls of the left ventricle

Question 9

Which part of the heart does the RCA supply?

Answer 9

Right atrium, right ventricle, SA node (in 60%), AV node (in 85%)

Question 10

What is coronary dominance?

Answer 10

It refers to which artery gives rise to the posterior descending artery (PDA)

Question 11

What is right coronary dominance?

Answer 11

PDA arises from the RCA (seen in ~85% of people)

Question 12

What is left coronary dominance?

Answer 12

PDA arises from the circumflex branch of LCA (seen in ~8-10%)

Question 13

What is balanced dominance?

Answer 13

PDA receives contribution from both RCA and LCA

Question 14

What are the peculiarities of coronary circulation?

Answer 14

Phasic blood flow (mainly during diastole), end-artery system, poor anastomosis, high oxygen extraction

Question 15

When does coronary blood flow occur maximally?

Answer 15

During diastole

Question 16

Why is blood flow reduced during systole in the left coronary artery?

Answer 16

Due to compression of intramyocardial vessels by contracting myocardium

Question 17

What is myocardial oxygen extraction ratio?

Answer 17

Very high (~70-80%), indicating low reserve

Question 18

What is the effect of increased heart rate on coronary perfusion?

Answer 18

It decreases diastolic time, thus reducing coronary perfusion

Question 19

How is coronary blood flow regulated?

Answer 19

By autoregulation, metabolic, neural and endothelial mechanisms

Question 20

Which mechanism is most dominant in coronary blood flow regulation?

Answer 20

Metabolic regulation

Question 21

What is the metabolic regulation of coronary blood flow?

Answer 21

Increase in metabolites (like adenosine, CO₂, H⁺, K⁺, NO) causes vasodilation

Question 22

What is the role of adenosine in coronary circulation?

Answer 22

It is a potent vasodilator released during hypoxia or high metabolic activity

Question 23

What is autoregulation in coronary vessels?

Answer 23

Ability to maintain constant blood flow despite changes in perfusion pressure

Question 24

What is the myogenic response in coronary autoregulation?

Answer 24

Vessel constricts when stretched, helping maintain stable flow

Question 25

How does the sympathetic nervous system affect coronary blood flow?

Answer 25

It causes initial vasoconstriction via α-receptors, followed by vasodilation via β₂-receptors and metabolic factors

Question 26

How does parasympathetic stimulation affect coronary vessels?

Answer 26

Minimal direct effect; can cause vasodilation via nitric oxide

Question 27

What is coronary artery disease (CAD)?

Answer 27

Narrowing or blockage of coronary arteries due to atherosclerosis

Question 28

What are risk factors for CAD?

Answer 28

Hypertension, diabetes, smoking, hyperlipidemia, obesity, family history

Question 29

What is angina pectoris?

Answer 29

Chest pain due to transient myocardial ischemia

Question 30

What is stable angina?

Answer 30

Predictable chest pain on exertion, relieved by rest or nitrates

Question 31

What is unstable angina?

Answer 31

Unpredictable chest pain, can occur at rest; indicates plaque rupture or thrombosis

Question 32

What is myocardial infarction (MI)?

Answer 32

Prolonged ischemia causing irreversible myocardial damage

Question 33

Which enzyme is most specific for MI diagnosis?

Answer 33

Troponin I/T

Question 34

What is the effect of CAD on coronary blood flow?

Answer 34

Decreased perfusion, particularly during increased demand (exercise/stress)

Question 35

What are collateral vessels in the heart?

Answer 35

Small anastomotic vessels that may enlarge during chronic ischemia