Quiz 9 - Coronary Circulation Flashcards
What are the major branches of the coronary arteries?
-Right Coronary
-Left Coronary (Bifurcates)
Left anterior descending (LAD)
Left Circumflex
Ramus intermedius (extra branch found
in some people.)
What is the Ramus Intermedius and to what percentage of people have it?
An additional branch in people who have a tri-furcation of left main and approximately 37% of the population have it.
T/F: Epicardial arteries contribute significantly to coronary vascular resistance.
False, but the intramyocardial vessels do (arterioles)
What is capillary density? Is capillary density increased or decreased in the myocardium?
Capillary density is the amount of capillaries in an area. Myocardium has increased density especially compared to skeletal muscle.
- What are the major determinants of myocardial oxygen demand?
HR, Contractility, Systolic wall tension (afterload)
- What are the major determinants of myocardial oxygen supply?
Vasc resistance
Coronary Blood Flow
O2 carrying capacity
- Is resting oxygen consumption of the heart high or low relative to other organs in the body?
High, next highest is kidneys, brain, liver…
- What is the formula for coronary perfusion pressure?
BP - LVEDP (or PCWP)
- Is oxygen highly extracted from blood flowing through the heart?
Yes, heart extracts O2 more than any other organ
- What factors control coronary blood flow?
Metabolic control Autoregulation Endothelial control of coronary vasc tone Extravascular compressive forces Neural control
- Does the majority of coronary blood flow occur during systole or diastole in the left ventricle? Why?
Diastole, during systole blood vessels are compressed and squeezes blood out. 80-90% of blood flow happens during early diastole.
- Which layer of the myocardium is at greatest risk for ischemia?
Subendocardium - it’s deeper and under more wall tension
- What is coronary flow reserve?
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
- Which of the following places a greater oxygen cost on the heart? Pressure work versus volume work
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
- How stenotic do coronary vessels have to be before there is a significant decrease in flow?
60-70% occlusion of vessel
- What is the final intracellular ion disturbance that leads to impaired myocardial contraction and cell death?
Increased intracellular Calcium
- What are the effects of myocardial ischemia on systolic function?
may cause akinesis (abscence of movement) or dyskinesis (sys lengthening and post sys shortening)
- What are the effects of myocardial ischemia on diastolic dysfunction?
.causes a rise in LVEDP: Relaxation is impaired and myocardial compliance decreases
- What is myocardial stunning?
After brief episode of ischemia, prolonged myocardial dysfunction with gradual return of contractile activity occurs.
- What is myocardial hibernation?
presence of impaired resting LV function owing to reduced CBF that can be restored toward normal by revascularization.
- What are some of the consequences of myocardial ischemia?
Systolic dysfunction Angina CHF or Pulm Edema Arrythmias MI Ventricular rupture or VSD Cardiogenic Shock Death.
- What are some of the drugs used for the treatment of ischemia?
Oxygen Beta Blockers Nitrates Antiplatelet/anticoagulant drugs analgesics (control pain - lead to better perfusion) Calcium Channel Blockers.
- What are some of the interventions used in the treatment of ischemia?
CABG Percutaneous Coronary Interventions ---Coronary Balloon Angioplasty ---Bare-metal stents ---Drug-eluting stents.
- How long should you wait before doing elective surgery on a patient who has had a drug-eluting stent inserted?
Drug-eluting - 1 yr recommended
Bare-metal - after 90 days.
- What are some of the drugs that are used to reduce cardiac ischemic events during surgery?
Beta Blockers Statins Volatile anesthetics (anesthetic preconditioning) Alpha 2 agonists Calcium channel blockers
- Is isoflurane an appropriate anesthetic agent to use during cardiac surgery? Why or why not?
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.
- What are collateral blood vessels in the heart? How are they formed?
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.
- What is ischemic preconditioning in the heart?
Single or multiple brief periods of ischemia can be protective against a subsequent prolonged ischemic insult.
—K+ATP channels play important role
- What is anesthetic preconditioning in the heart?
Inhaled anesthetics have effects that mimic ischemic preconditioning
