Regulation of Coronary Circulation Flashcards
The clinical manifestation of the alterations in the delivery of blood supply to the myocardium.
Coronary heart disease
3 determinants of myocardial oxygen demand
- myocardial wall tension
- myocardial contractility
- heart rate
large conductance vessels providing blood flow to myocardium with little role in vascular regulation
epicardial arteries (arise from aorta)
What layers are present in epicardial arteries?
thin intima, smooth muscle media, and supportive adventitia
What is the site of angioplasty or bypass?
epicardial arteries
What artery provides diagonal and septal branches to the heart?
LAD
Which artery provides obtuse marginal branches to the heart?
left cx
Which vessels are responsible for the majority of coronary vascular resistance?
intramyocardial coronary arteries
Is blood flow to the heart regulated at the microcirculation level or at the major epicardial level?
microcirculation
For the heart, coronary blood flow is determined by the _____ into the coronary arteries and by the ______ of the coronary arterial system.
driving pressure and vascular resistance
What parameters define coronary perfusion pressure?
central aortic pressure - LVEDP
Does most of coronary blood flow occur during systole or diastole?
diastole –> because myocardial compressive forces prevent blood flow during systole
compressive force applied to coronary arteries during systolic muscular contraction of the heart, limiting most flow to the diastolic period
extravascular resistance –> if heart rate increases, there is less diastolic time for delivery and less oxygen for the heart
Are extravascular compressive forces greater on the subendocardial or subepicardial regions of the heart?
subendocardial –> net driving force of subendocardial blood flow is lower than for epicardium –> makes endocardium more vulnerable to ischemia
Can resting or maximal coronary flow be maintained despite substantial epicardial stenosis?
yes
The amount by which resistance can be decreased, therefore preserving flow in the setting of epicardial stenosis.
vasodilatory reserve
Resistance changes that keep flow constant in face of altered pressure
autoregulation
How is vasodilatory reserve described in a two resistor model?
R1 = resistance of epicardial vessels R2 = resistance of small arteries (high but low impact) Q = P/(R1+R2) --> if R1 increases due to stenosis, R2 will decrease to maintain constant flow
How do vasodilation and vasoconstriction differ in regulation within the concept of myogenic regulation as it relates to coronary arteries?
constriction is via stretch induced depolarization of VSMCs
dilation is via potassium ion efflux through ATP-sensitive potassium channels
What is the difference between endothelium dependent vasodilation and endothelial independent vasodilation as it relates to coronary arteries?
endothelium dependent requires intact endothelium –> NO release
endothelium independent does not require intact endothelium –> exogenous nitroglycerin, papavarine, calcium channel antagonists
If you inhibit NO synthase under basal conditions, what is the consequence?
moderate vasoconstriction
How does metabolic demand affect vascular resistance?
adenosine released from breakdown of ATP –> results in vasodilation/increase coronary blood flow via cAMP
Is metabolic regulation of vascular resistance endothelium dependent/independent?
independent
What is the difference between beta 1 and 2 adrenergic vasodilatory effects ?
1: via increased metabolic demand
2: via direct vasodilatory effect
T/F endothelial dysfunction is a hallmark of early and late CAD and may be identified before critically important coronary narrowing is seen
T
Can endothelial dysfunction be modified through standard treatments for CAD like lipid lowering and exercise?
yes
What causes angina pectoris? How is it treated?
narrowing of one or more coronary arteries –> symptoms appear after 70% stenosis b/c of adequate compensation by small arterioles
tx = nitrates, anti-platelets, beta blockers, ultimately stent or CABG
What causes unstable angina? How is it treated?
clinical syndrome of progressive chest pain –> often due to secondary rupture of atherosclerotic plaque w/in vessel resulting in platelet aggregation, thrombus formation, vasospasm
tx = nitrates, anti-thrombotics, platelet inhibitors, revascularization stent or CABG
What causes acute MI? How is it treated?
plaque rupture and secondary thrombus/platelet accumulation resulting in complete/nearly complete occlusion of a coronary vessel
tx = stent, thrombolytic medifications to restore blood flow
What causes coronary artery spasm? How is it treated?
severe, focal, reversible narrowings in epicardial arteries sometimes in presence of pre-existing atherosclerotic plaque
tx= nitrates, calcium channel blockers to prevent spasm
What causes small vessel disease?
poorly defined syndrome with angina w/o obvious narrowing of epicardial arteries but with decreased vasodilator reserve
