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31 Cards in this Set

  • Front
  • Back
What occurs to coronary circulation of the innermost (endocardial) layers of the heart during systole?
They are compressed and blood flow is reduced
True/False: Coronary arterys have few sizeable anastomoses between individual coronary artery branches.
Define: The large coronary arteries and veins visible on the surface of th heart.
Conduit vessels
True/False: the Conduit vessels (arteries/veins) on the surface of the heart exercise a large influence on coronary flow rate.
False; the arterioles they supply exercise the strong influence
Define: tiny, thick-walled muscular tubes which determine the rate of passage of blood through the coronary circulation.
Coronary resistance vessels
True/False: The heart extracts nearly all of the oxygen from circulation.
The Rate of myocardial oxygen consumption (in a normally perfused subject) =
Rate of coronary blood flow
What is the effect of increased contractility, increased heart rate, increased systolic pressure/chamber volume on myocardial oxygen consumption?
Increase rate of myocardial oxygen consumption and therefore the rate of coronary blood flow
What occurs when coronary oxygen supply falls short of myocardial oxygen demand?
Myocardial ischemia
If heart rate is increased from 60 bpm to 120 bpm what is the effect on myocardial oxygen consumption and coronary blood flow?
It will also double.
If coronary flow is limited, what is the danger associated with interventions augmenting HR, BP or contractility?
These interventions increase myocardial oxygen consumption and if flow is limited bring on or increase myocardial ischemia
What is the most important influence in controlling coronary blood flow?
Metabolic regulation
List one metabolite known to cause coronary vasodilation.
Define: the blood pressure gradient driving flow from arteries to veins
Perfusion pressure
Describe how perfusion pressure is important in coronary circulation.
Despite the presence of metabolites, if there is not adequate perfusion pressure there will not be blood flow
During what phase of the cardiac cycle does blood flow to most of the ventricular wall occur?
During diastole (during systole intramyocardial pressure collapses the vessels)
What is the effect of an increase in left ventricular diastolic pressure on the subendocardial capillary beds?
They are collapsed potentially resulting in mild heart ischemia
Shear stress on the endothelial wall releases what vasodilator in coronary circulation (and probably systemic?)?
Nitric Oxide
What effect does prostacyclin have on coronary circulation?
What effect does adrenergic (sympathetic) nerve terminals have on vascular smooth muscle?
Tends to contract vascular smooth muscle resulting in constriction
True/False: Minor and even moderate degrees of conduit blockage have no effect on coronary arteries.
With increase in luminal blockage greater than ____ % maximum flow in the affected artery is progressively reduced.
50 % results in progressive reduction in coronary artery flow
Obstruction of at least ______% maximum flow interferes with coronary blood flow even at rest.
Describe myocardial hibernation.
Sustained reduction in perfusion by a sustained decrease in contractile and metabolic activity
Normally is conduit resistance greater or smaller relative to microvessel resistance?
Much smaller
How is microvasscular resistance effect in coronary occlusive disease?
Since the conduit resistance is increased (via coronary artery stenosis) the microvasculature shrinks to compoensate (resulting in loss of metabolic regulation)
What is the effect of the shrinking of microvasculature in coronary occlusive disease on metabolic regulation?
Metabolic regulation is lost
What effect does the loss of metabolic regulation have on the heart?
Makes the myocardium vulnerable to ischemia whenever blood pressure is low
List three factors which exacerbate the hemodynamic effects of coronary stenosis.
Markedly decreased arterial pressure, thrombosis, and coronary artery spasm
List three factors which mitigate the hemodynamic effects of coronary stenosis.
Thrombolysis, coronary collateral formation, and arterial wall remodeling
Give a nonatherosclerotic cause of coronary occlusive disease.
myocardial hypertrophy due to longstanding hypertension (resulting from outgrowing the blood supply)