Quiz 9 - Coronary Circulation

Question 1

What are the major branches of the coronary arteries?

Answer 1

-Right Coronary
-Left Coronary (Bifurcates)
Left anterior descending (LAD)
Left Circumflex
Ramus intermedius (extra branch found
in some people.)

Question 2

What is the Ramus Intermedius and to what percentage of people have it?

Answer 2

An additional branch in people who have a tri-furcation of left main and approximately 37% of the population have it.

Question 3

T/F: Epicardial arteries contribute significantly to coronary vascular resistance.

Answer 3

False, but the intramyocardial vessels do (arterioles)

Question 4

What is capillary density? Is capillary density increased or decreased in the myocardium?

Answer 4

Capillary density is the amount of capillaries in an area. Myocardium has increased density especially compared to skeletal muscle.

Question 5

5. What are the major determinants of myocardial oxygen demand?

Answer 5

HR, Contractility, Systolic wall tension (afterload)

Question 6

6. What are the major determinants of myocardial oxygen supply?

Answer 6

Vasc resistance
Coronary Blood Flow
O2 carrying capacity

Question 7

7. Is resting oxygen consumption of the heart high or low relative to other organs in the body?

Answer 7

High, next highest is kidneys, brain, liver…

Question 8

8. What is the formula for coronary perfusion pressure?

Answer 8

BP - LVEDP (or PCWP)

Question 9

9. Is oxygen highly extracted from blood flowing through the heart?

Answer 9

Yes, heart extracts O2 more than any other organ

Question 10

10. What factors control coronary blood flow?

Answer 10

Metabolic control
Autoregulation
Endothelial control of coronary vasc tone
Extravascular compressive forces
Neural control

Question 11

11. Does the majority of coronary blood flow occur during systole or diastole in the left ventricle? Why?

Answer 11

Diastole, during systole blood vessels are compressed and squeezes blood out. 80-90% of blood flow happens during early diastole.

Question 12

12. Which layer of the myocardium is at greatest risk for ischemia?

Answer 12

Subendocardium - it’s deeper and under more wall tension

Question 13

13. What is coronary flow reserve?

Answer 13

It is the difference between baseline blood flow and maximal flow. In abscence of coronary disease, max flow is 4-5 times greater than at rest

Question 14

14. Which of the following places a greater oxygen cost on the heart? Pressure work versus volume work

Answer 14

Pressure work is much more costly than volume work on the heart.
Press Work = increased arterial pressure at constant CO
Vol Work = Increased CO while maintaining constant pressure

Question 15

15. How stenotic do coronary vessels have to be before there is a significant decrease in flow?

Answer 15

60-70% occlusion of vessel

Question 16

16. What is the final intracellular ion disturbance that leads to impaired myocardial contraction and cell death?

Answer 16

Increased intracellular Calcium

Question 17

17. What are the effects of myocardial ischemia on systolic function?

Answer 17

may cause akinesis (abscence of movement) or dyskinesis (sys lengthening and post sys shortening)

Question 18

18. What are the effects of myocardial ischemia on diastolic dysfunction?

Answer 18

.causes a rise in LVEDP: Relaxation is impaired and myocardial compliance decreases

Question 19

19. What is myocardial stunning?

Answer 19

After brief episode of ischemia, prolonged myocardial dysfunction with gradual return of contractile activity occurs.

Question 20

20. What is myocardial hibernation?

Answer 20

presence of impaired resting LV function owing to reduced CBF that can be restored toward normal by revascularization.

Question 21

21. What are some of the consequences of myocardial ischemia?

Answer 21

Systolic dysfunction
Angina
CHF or Pulm Edema
Arrythmias
MI
Ventricular rupture or VSD
Cardiogenic Shock
Death.

Question 22

22. What are some of the drugs used for the treatment of ischemia?

Answer 22

Oxygen
Beta Blockers
Nitrates
Antiplatelet/anticoagulant drugs
analgesics (control pain - lead to better perfusion)
Calcium Channel Blockers.

Question 23

23. What are some of the interventions used in the treatment of ischemia?

Answer 23

CABG
Percutaneous Coronary Interventions
---Coronary Balloon Angioplasty
---Bare-metal stents
---Drug-eluting stents.

Question 24

24. How long should you wait before doing elective surgery on a patient who has had a drug-eluting stent inserted?

Answer 24

Drug-eluting - 1 yr recommended

Bare-metal - after 90 days.

Question 25

25. What are some of the drugs that are used to reduce cardiac ischemic events during surgery?

Answer 25

Beta Blockers
Statins
Volatile anesthetics (anesthetic preconditioning)
Alpha 2 agonists
Calcium channel blockers

Question 26

26. Is isoflurane an appropriate anesthetic agent to use during cardiac surgery? Why or why not?

Answer 26

Isoflurane has been associated with Coronary Steal (shunting blood from poorly perfused areas to better perfused) causing worsening ischemia.
In reality, coronary steal is not that big a deal - don’t use Iso if pt has severe hypotension.

Question 27

27. What are collateral blood vessels in the heart? How are they formed?

Answer 27

develop in response to impairment of coronary blood flow.

- develop between branches of occluded and non-occluded arteries and can contribute a significant amount of blood flow.

Question 28

28. What is ischemic preconditioning in the heart?

Answer 28

Single or multiple brief periods of ischemia can be protective against a subsequent prolonged ischemic insult.
—K+ATP channels play important role

Question 29

29. What is anesthetic preconditioning in the heart?

Answer 29

Inhaled anesthetics have effects that mimic ischemic preconditioning