Quiz 9 Coronary Circulation Flashcards
- Know the major branches of the coronary arteries.
Left Main
-LAD
-Circumflex
Right Main
- What is the Ramus Intermedius? In what percentage of the population does it exist?
A trifurcation of the left main (37% of the population)
- Do the major epicardial arteries contribute significantly to coronary vascular resistance?
No, most resistance is at the Intramyocardial vessels (arterioles)
- What is capillary density? Is capillary density increased or decreased in the myocardium?
The # of capillaries per unit area
Increased
- What are the major determinants of myocardial oxygen demand?
HR
Contractility
Systolic Wall Tension
- What are the major determinants of myocardial oxygen supply?
O2 carrying capacity
Coronary Blood Flow
- Is resting oxygen consumption of the heart high or low relative to other organs in the body?
HIGH
- What is the formula for coronary perfusion pressure?
CPP= DBP - LVEDP (or PCWP)
- Is oxygen highly extracted from blood flowing through the heart?
Yes, the heart extracts O2 at a greater extent than any other organ
- What factors control coronary blood flow?
Metabolic Control Autoregulation Endothelial Control of Vascular Tone Extravascular Compressive Forces Neural Control
- Does the majority of coronary blood flow occur during systole or diastole in the left ventricle? Why?
Diastole, Squeeze?
- Which layer of the myocardium is at greatest risk for ischemia?
Subendocardium (More wall tension & b/c it is deepest)
- What is coronary flow reserve?
Difference between baseline blood flow and maximal flow
- Which of the following places a greater oxygen cost on the heart? Pressure work versus volume work.
Pressure - Work
- How stenotic do coronary vessels have to be before there is a significant decrease in flow?
60-70% occlusion
- What is the final intracellular ion disturbance that leads to impaired myocardial contraction and cell death?
High levels of Calcium (Intracellularly)
- What are the effects of myocardial ischemia on systolic function?
Minimal impairment to absence of movement (akinesis) to systolic lengthening & post systolic shortening (diskinesis)
- What are the effects of myocardial ischemia on diastolic dysfunction?
LVEDP increases, relaxation is impaired & myocardial compliance decreases
- What is myocardial stunning?
After a brief episode of severe 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 and Diastolic dysfunction, angina, CHF, Pulmonary Edema, Arrythmias, MI, Ventricular Rupture or VSD, Cardiogenic shock, Death
- What are some of the drugs used for the treatment of ischemia?
O2, beta blockers, nitrates, antiplatelets/ anticoagulants, analgesics, calcium channel blockers
- What are some of the interventions used in the treatment of ischemia?
CABG PCI -coronary balloon angioplasty -bare metal coronary stents -drug eluting stents
- How long should you wait before doing elective surgery on a patient who has had a drug-eluting stent inserted?
1 year is recommended
- What are some of the drugs that are used to reduce cardiac ischemic events during surgery?
Volatile anesthetics Beta blockers Statins Alpha 2 agonists Calcium Channel Blockers
- Is isoflurane an appropriate anesthetic agent to use during cardiac surgery? Why or why not?
Yes, does not effect coronary steel syndrome
- What are collateral blood vessels in the heart? How are they formed?
develop in response to impairment of coronary blood flow, they originate from pre-existing arterioles that undergo proliferative changes of the endocardium and smooth muscle
- What is ischemic preconditioning in the heart?
a single or multiple brief periods of ischemia that can be protective against a subsequent prolonged ischemic insult
- What is anesthetic preconditioning in the heart?
The use of anesthetic agents to have effects that mimic Ischemic preconditioning
K ATP channels play an important role
