ACS 1 - Quiz 3 Flashcards
continuum of ACS
- unstable angina
- NSTEMI
- STEMI
STEMI stands for
- ST Elevation Myocardial Infarction
NSTEMI stands for
- Non-ST Elevation Myocardial Infarction
troponin levels of unstable angina
- troponin is negative
- not actually myocyte death or necrosis
more than 90% of ACS results from
- disruption of an atherosclerotic plaque
- with subsequent platelet aggregation and thrombus formation
major trigger for coronary thrombosis
- atherosclerotic plaque rupture
atherosclerotic plaque rupture due to
- chemical factors that destabilize the lesion
- physical stresses on the lesion
triggers for ACS
- strenuous physical activity
- emotional stress
- SNS activation
coronary thrombosis exacerbated by
- endothelial dysfunction
endothelial dysfunction leads to
- vasoconstriction and diminished anti-thrombotic function
normal hemostasis
blood vessel injured –> disrupted endothelial surface
–> exposure of the thrombogenic connective tissue to circulating blood
primary hemostasis
- first line of defense versus bleeding
primary hemostasis mediated by
- circulating platelets
- form platelet plug
secondary hemostasis
- sub endothelial tissue triggers coagulation cascade
- fibrin clot by thrombin activation
endogenous anti-thrombotic examples
- antithrombin III
- protein C and S
- Tissue Factor Pathway Inhibitor
- tissue plasminogen activator
- Prostacyclin
- nitric oxide
what are anti-thrombotics
- safeguards to prevent spontaneous thrombosis and arterial occlusion
role of antithrombin
- binds irreversibly to thrombin and other clotting factors
antithrombin increased effectiveness with
- heparin
role of protein C and S
- degrades factors Va and VIIIa
tissue factor pathway inhibitor
- plasma serine protease inhibitor
tissue factor pathway inhibitor activated by
- factor Xa
role of tissue factor pathway inhibitor
- inhibits coagulation via extrinsic pathway
tPA secreted by
- endothelial cells
tPA cleaves
- plasminogen to form plasmin
tPA role
- degrades fibrin clots
prostacyclin secreted by
- endothelial cells
prostacyclin role
- increases platelet levels of cAMP
- inhibits platelet activation/aggregation
- vasodilator
nitric oxide secreted by
- endothelial cells
nitric oxide role
- inhibits platelet activation
- potent vasodilator
which are partially occlusive thrombi
- unstable angina
- NSTEMI
which are completely obstructive thrombi
- STEMI
acute MI discrete focus of
- coagulative necrosis in the heart
acute MI development related to
- duration of ischemia
- metabolic rate of ischemic tissue
how many minutes of ischemia can cause infarct
- 20-30 minutes
acute MI frequently result from
- acute plaque rupture with coronary artery thrombosis
acute MI dissolution of thrombus frequent within
- 12-24 hours
infarcts involve which ventricle
- LV more commonly and extensively than RV
MI occurs when
- ischemia is bad enough to cause myocyte necrosis
two types of infarct
- transmural infarct
- subendocardial infarct
transmural infarct spans
- entire thickness of myocardium
transmural infarct due to
- prolonged, total occlusion of an epicardial coronary artery
subendocardial infarct involves
- only innermost layers of the myocardium
which infarct is most susceptible to ischemia
- subendocardial infarct
why is subendocardial infarct most susceptible to ischemia
- poor collateral flow
- adjacent to high-pressure ventricle
- furthest from epicardial coronary arteries
amount of tissue that ultimately succumbs to infarction depends upon
- degree of reperfusion and inflammatory response
- oxygen demand of affected area
- mass of myocardium perfused by the coronary artery
- adequacy of collateral coronary flow
- magnitude and duration of ischemia
DOMAM
collateral flow is supplies by
- other coronaries
early MI changes - metabolism
- rapid shift from aerobic to anaerobic metabolism
early MI changes - what accumulates
- lactic acid accumulates
early MI changes - reduction in
- ATP
early MI changes - ion changes
- rising intracellular Na+
- abnormal electrolyte/ion shifts
rising of intracellular Na+ leads to
- cellular edema
abnormal electrolyte/ion shifts leads to
- arrhythmia risk
early MI changes - irreversible cell injury ensues in how many minutes
- 20 minutes
macroscopic features of infarction <4 hours
- no abnormality
macroscopic features of infarction 4-12 hours
- occasional dark mottling
macroscopic features of infarction 12-24 hours
- dark mottling
macroscopic features of infarction 1-3 days
- mottling with developing yellow tan necrotic center
macroscopic features of infarction 3-14 days
- maximally yellow-tan and soft
- depressed red-tan border
macroscopic features of infarction 2-8 weeks
- gray-white scar
- progressive from border to core of infarct
macroscopic features of infarction > 2 months
- mature scar
microscopic features of infarction <4 hours
- none
microscopic features of infarction 4-12 hours
- early coagulative necrosis
- edema
- hemorrhage
microscopic features of infarction 12-24 hours
- early PMNs
microscopic features of infarction 1-3 days
- marked interstitial PMNs
microscopic features of infarction 3-14 days
- macrophages and granulation tissue at border
microscopic features of infarction 2-8 weeks
- loss of cellularity
- increasing collagen
microscopic features of infarction > 2 months
- dense collagenous scar
functional changes following MI
- systolic and diastolic dysfunction
- stunned myocardium
- ischemic preconditioning
- ventricular remodeling
systolic dysfunctional changes
- hypokinesis
- akinesis
- dyskinesis
hypokinesis
- local region with reduced contraction
akinesis
- local region with no contraction
dyskinesis
- local region that bulges outward with contraction
diastolic dysfunction results in
- reduced compliance
- elevated ventricular filling pressures
stunned myocardium
- prolonged, but reversible period of contractile dysfunction
stunned myocardium how long does it take to recover?
- takes days to weeks to recover
ischemic preconditioning
- renders tissue more resistant to future episodes of ischemia
ventricular remodeling changes geometry of which myocardium
- infarcted and noninfarcted myocardium
ventricular remolding results in
- ventricular dilatation
- infarct expansion
- myocyte slide-to-slide slippage
ventricular remolding advantages
- mechanically disadvantageous
ventricular remolding wall stress
- increased wall stress
MI complications
- arrhythmias
- LV failure, cardiogenic shock
- extension of infarct
- myocardium free wall rupture
- septal perforation
- papillary muscle rupture
- aneurysm
- mural thrombosis
result of LV failure
- high grade stenosis of all coronary vessels
myocardial free wall rupture occurs when
- first 3 weeks
myocardial free wall rupture most common
- days 3-7
- when wall is weakest
myocardial free wall rupture complication of
- large infarcts
myocardial free wall rupture occurs at
- junction of infarct and normal muscle
septal perforation results in
- left to right shunt
papillary muscle rupture results in
- mitral regurgitation
- massive MV incompetence
aneurysm result
- wall bulges outward during systole
aneurysm - as infarct matures
- fibrous scar progressively stretches
aneurysm - increased risk for
- myocardial rupture
BASICALLY AS THE WALL IS STRETCHING IT IS FAR MORE LIKELY TO RUPTURE
aneurysm - predisposes to
- mural thrombosis
aneurysm - effect on workload
- increases workload
mural thrombosis - seen in
- fatal acute myocardial infarct
- after apical infarcts
mural thrombosis predisposes to
- systemic embolization
MI symptoms - nausea, vomiting, weakness is what kind of effect
- parasympathetic
MI symptoms - diaphoresis, cool/clammy skin is what kind of effect?
- sympathetic
MI symptoms - fever is what kind of effect
- inflammatory
evidence of systemic hypoperfusion
- hypotension
- tachycardia
- impaired cognition
- cool extremities
- end-organ injury
evidence of heart failure
- elevated jugular venous pulsation
- pulmonary crackles
- gallops - S3,S4
- new murmurs
ischemia compromises which part of the cardiac cycle
- diastolic, filling function
EKG abnormalities for clinical detection of ischemia
- new ST segment elevation > 1mm
- new ST segment depression
- new T wave inversion
what are labile T wave inversions
- change after rest and nitroglycerin
ST segment represents
- period between depolarization and repolarization of left ventricle
ST segment should be about how long
- about the same size as PR segment
subendocardial injury results in what ST effect
- ST depression
transmural injury results in what ST effect
- ST elevation
high risk features of MI
- increased age
- low BP
- elevated HR
- heart failure
- anterior location
definition of acute MI values
- rise/fall of troponin
- one value above 99th percentile
definition of acute MI - symptoms
- symptoms of acute ischemia
definition of acute MI - ECG
- new ST-T changes
- LBBB
- pathological Q waves
definition of acute MI - imaging
- loss of viable myocardium
- regional wall motion abnormality
definition of acute MI - angiography of autopsy
- intracoronary thrombus
which troponins do we use?
- troponin I and T
CK-MB diagnosis of MI
- upper limit of normal
- 2.5% of total CK (creatine kinase)
importance of collecting samples for diagnosis of MI
- always collect serial samples
non-cardiac causes of troponin elevation
- acute HF
- PE
- shock
- aortic dissection
- myocarditis
- trauma
- ICD discharge
STEMI diagnosis
- > 1 mm ST segment elevation in 2 contiguous leads
- > 2 mm ST segment elevation in 2 contiguous precordial leads
- new LBBB
contiguous leads II, III, and AVF point to which anatomic location
- inferior
contiguous leads II, III, and AVF point to which coronary artery
- RCA > Lcx
V2-V4 point to which anatomic location
- anterior
V2-V4 point to which coronary artery
- LAD
V1-V4 point to which anatomic location
- anteroseptal
note:
V1/V2 = septal
V3/V4 = anterior
V1-V4 point to which coronary artery
- LAD
I, aVL, V5, V6 point to which anatomic location
- lateral
I, aVL, V5, V6 point to which coronary artery
- Lcx > LAD
LBBB points to which anatomic location
- anterior
LBBB points to which coronary artery
LAD
V4R points to which anatomic location
- right ventricle
V4R points to which coronary artery
- RCA
V1,V2 ST depression points to which anatomic location
- posterior
V1,V2 ST depression points to which coronary artery
- RCA > Lcx
MI localization
in LAD
- anterior LV
- anterior 2/3 septum
- apical LV
MI Localization
in LCX
- lateral LV
- posterolateral LV
MI Localization
in RCA
- posterior LV
- posterior 1/3rd septum
- posterior papillary muscle
- “inferior” or “diaphragmatic”
STEMI treated with
- emergency cardiac catheterization
pathologic Q waves are indicative of
- prior transmural STEMI
- not seen in UA or NSTEMI
diagnostic criteria for pathologic Q waves
- > 1 mm wide
25% of overall amplitude of QRS complex - present in > 2 contiguous leads
variant (prinzmetal) angina
- focal coronary artery spam in absence of overt atherosclerotic lesions
variant (prinzmetal) angina presents with
- chest pain
- transient ST elevation
variant (prinzmetal) angina due to
- smooth muscle hyperreactivity
- endothelial dysfunction
variant (prinzmetal) angina diagnosis
- intracoronary acetylcholine provokes spasm
variant (prinzmetal) angina treatment
- nitrates
- calcium channel blockers
UA or NSTEMI symptoms
- rest angina > 20 minutes
- new onset angina that limits activity
- increasing angina in unstable pattern
- +/- T wave inversion or ST depression
TIMI risk score for risk stratification in NSTEMI and Unstable Angina
> 65 years of age - known CAD (>50% coronary stenosis) >3 risk factors for CAD - aspirin use within past 7 days > 2 episodes of angina within past 24 hours - ST changes > 0.5 mm - elevated cardiac markers
other causes of ACS
- decreased myocardial oxygen supply
- increase in myocardial oxygen demand
decreased myocardial oxygen supply due to
- decreased perfusion pressure due to hypotension
- anemia
- coronary artery dissection or emboli
increased in myocardial oxygen demand due to
- rapid tachyarrhythmias
- acute hypertension
- aortic stenosis