Pathophysiology of Chronic Ischemic Heart Disease Flashcards
define unstable angina
sudden increase in tempo or severity of anginal episodes with less exertion or even at rest….typically from plaque rupture and thrombus formation…can lead to NSTEMI
define stable angina
predictable chest pain with exertion or stress…due to a plaque blockage in one more coronary arteries…does not lead to infarction
at rest what percent of oxygen is extracted from the blood in the heart?
almost 100%
what two properties mediate the blood supply to the heart?
coronary blood flow and vascular resistance
does most blood flow to the heart occur during systole or diastole? why?
diastole…because during systole the vessels get crunched within the contracting wall
what is the coronary perfusion pressure typically equal to?
the diastolic pressure of the aorta
what percent of blockage leads to the loss of dilatation by coronary arteries?
70%…they can no longer respond to the effects of NO
how do vessels changes under acidosis?
vasodilate
how do vessels changes under hypoxia?
vasodilate
how do vessels changes under adenosine?
vasodilate
what two ways does atherosclerosis limit blood flow in coronaries?
limit radius of vessel and make it dysfunctional and unable to respond to or release NO
how does an adenosine stress test work?
it is a vasodilator for vessels that do not have plaques…so if there is a plque then after adenosine it will not show up, whereas the others will
when is an exercise stress test positive?
if yields chest pain and ECG abnormality of ST segment depression of 1 mm
if exercise stress test is positive…what can we add to see better?
radionuclide that will provide nuclear imaging and perfuse with vessels that are not blocked
does the oxygen demand of the heart increase or decrease when catecholamines are present?
increases due to increasing heart rate and contractility
how do catecholamines affect the coronary vessels?
cause more constriction that dilation…so decrease the supply of blood to the heart
what is best class of drugs for the stable angina patient?
beta blockers
what three beta blockers are best for ischemic heart disease and why?
atenolol, metoprolol and esmolol
because they are cardioselective…IE they target the B1 better than B2 receptor
in what type of heart failure are beta blockers contraindicated?
acute…because heart is failing we dont want to slow it even more
what two types of conduction issues are beta blockers contraindicated with?
AV block or severe bradycardia
dihydropyridine calcium channel blockers target what? and have what effect?
smooth muscle cells…leads to vasodilation to help with coronary flow
non dihydropyridines calcium channel blockers target what and have what effect?
the heart…leads to slower rate and increases time of diastole to decrease O2 demand of the heart
when should you not give calcium channel blockers?
AV block or severe bradycardia
nitroglycerin causes what vessel types to constrict or dilate?
arteries and veins…to dilate
the venous dilation from nitoglycerine leads to what benefit for ischemic patients?
decreased LVEDV which leads to less O2 demand for heart
the arterial dilation from nitroglycerine leads to what benefit for ischemic patients?
increased coronary supply to heart
name the two side effects of nitroglycerin
headaches and hypotension
in what scenarios should CABG be performed instead of PCI (3 scenarios)?
if LAD is over 50% blocked
if 3 vessels are blocked
if 2 vessels including LAD with low ejection fraction
