Ischemic Heart Disease Flashcards
ischemic heart disease is caused by
- coronary atherosclerosis
myocardial ischemia results from
- an imbalance between oxygen supply and oxygen demand
how does atherosclerosis disrupt myocardial oxygen supply
(1) decreasing coronary artery diameter
(2) disrupting normal endothelial function
chief determinants of myocardial oxygen demand
- heart rate
- contractility
- wall tension
how do we treat chronic stable angina
- reduce demand
how do we treat coronary syndromes
- restore supply
most commonly used medications for treatment of chronic stable angina
- organic nitrates
- beta blockers
- calcium channel blockers
definition of ischemia
- interference with blood supply to tissues
angina
- chest pain due to inadequate supply of oxygen to the heart
chief clinical manifestation of myocardial ischemia
- angina
how does ischemia cause angina
- release lactate, serotonin, and adenosine that activates local afferent pain fibers
chronic stable angina
- predictable transient chest discomfort during exertion or emotional stress
chronic stable angina caused by
- fixed obstructive plaque in >1 coronary arteries
chronic stable angina and myocyte death
- not associated with cardiomyocyte death
what supplies the oxygen
- coronary artery
what demands the oxygen
- myocardium
what is compressed during systole
- intramural coronary arteries
when is the heart’s oxygen demand the highest
- at rest
- due to ATP requirement
reserve of oxygen in blood at rest
- minimal reserve
what is the primary determinant of myocardial oxygen supply
- coronary blood flow
what is the primary determinant of coronary blood flow
- vascular resistance
the fate of the myocardium subjected to ischemia depends on
- severity and duration of imbalance between oxygen supply and demand
phases of myocyte function at low oxygen supply
- reversible recovery of myocyte function
- stunned myocardium
- hibernating myocardium
- irreversible myocardial necrosis/infarction
regulation of blood flow occurs in which vessels?
- smaller resistance vessels
we visualize atherosclerosis in which vessels?
- larger epicardial vessels
coronary blood flow occurs in which phase?
- diastole
relationship of diastolic filling time and heart rate
- increasing heart rate decreases diastolic filling time
coronary perfusion pressure formula
aortic diastolic pressure - LVEDP
how can coronary perfusion pressure be compromised?
- LVEDP is high
- aortic pressure is low
- as in heart failure
what is the major determinant of resistance in blood vessels
- radius
coronary arteries are capable of sufficient compensatory dilatation to prevent ischemia until the diameter of the lumen is what
- decreased by > 70%
metabolic determinants of vascular tone
results
- acidosis
- hypoxia
- citrate/acetate
- adenosine
all vasodilation
endothelial determinant of vascular resistance
results
- nitric oxide
- vasodilation
what is the most known endogenous vasodilator
- nitric oxide
how atherosclerosis causes endothelial dysfunction
- impairs endothelial capacity to regulate vascular tone
how stress tests work
- provoke and detect a mismatch in supply and demand that causes controlled and transient subendocardial ischemia
pharmacologic drugs for stress test
- dobutamine
- adenosine
- dipyridamole
when is a stress test considered positive
- typical chest discomfort reproduced
- > 1 mm ST depression
radionucleotide imaging can be added in patients with
- abnormal baseline ECG
- high clinical suspicion of ischemic heart disease
cause of a reversible defect: perfused at rest, but not after stress
- inducible ischemia
cause of fixed defect: no perfusion at rest or after stress
- prior MI and fibrosis
coronary angiography reserved for which patients:
- anginal symptoms not respond to drug therapy
- unstable presentation
- noninvasive test is abnormal
what is the gold standard for CAD
- coronary angiography
what do endothelial cells release
- paracrine vasodilatory signals
non-selective beta blockers
- propranolol
- nadolol
cardioselective beta blockers
- atenolol
- metoprolol
- esmolol
mixed selective beta blockers
- carvedilol
- labetalol
contraindications of beta blockers
- severe bronchospastic disease
- severe decompensated heart failure
- severe bradycardia
- AV block
calcium channel blockers MOA
- block L type calcium channel
dihydropyridines
- all the -dipines
non-dihydropyridines
- verapamil
- diltiazem
what do dihydropyridine calcium channel blockers act on
- vascular smooth muscle
physiological effects of both classes of calcium channel blockers
- arterial vasodilation
result of arterial vasodilation
- increased coronary blood flow
- decreased blood pressure
physiologic effects of non-DHP calcium channel blockers
- prolonged AV conduction
- negative inotropy
result of prolonged AV conduction
- decreased heart rate
- increased diastolic time
result of negative inotropy
- decreased oxygen demand
what line of therapy are calcium channel blockers?
- second line therapy
contraindications for calcium channel blockers
- systolic heart failure
- bradycardia
- sinus node dysfunction
- AV nodal block
organic nitrates serve as
- nitric oxide donors
MOA of organic nitrates
- venodilation
- arteriodilation
result of venodilation
- decreased venous return
- decreased wall tension
- decreased oxygen demand
result of arteriodilation
- increased coronary blood flow
- increased oxygen demand
what is sublingual nitroglycerin used to treat
- acute episodes of angina
what do we use for prevention of chronic stable angina
- isosorbide mononitrate
- denigrate
contraindication for organic nitrates
- PDE-5 inhibitors like viagra
what do we use for secondary prevention
- aspirin
- statins
first line treatment of stable angina
- beta blockers and nitrates to reduce demand
- aspirin and statins to prevent worsening atherosclerosis and ACS
what if angina persists despite medical therapy
- use PCI
does PCI change mortality
- no
how does a CABG work?
- left internal mammary artery freed from chest wall and attached to LAD
- saphenous veins removed from legs and grafted from ascending aorta to coronary arteries
when is CAB preferred over PCI
- 50% of left main coronary artery
- 3 vessel disease - LAD, Lcx, RCA
- 2 vessel disease - LAD with low ejection fraction or diabetes
