ACS 1 Flashcards
What are some of the endogenous anti-thrombotics that prevent spontaneous thrombosis and arterial occlusion?
- Antithrombin 3: Plasma protein that binds irreversible to thrombin and other clotting factors; increased effectiveness with heparin
- Protein C and S- Degrades factors Va and VIIIa
- Tissue factor pathway inhibitor: Plasma serine protease inhibitor activated by factor Xa; inhibits coagulation via the extrinsic pathway
What are other endogenous factors involved in ACS?
- TPA: Secreted by endothelial cells; cleaves plasminogen to form plasmin, which degrades fibrin clots
- Prostacyclin: Secreted by endothelial cells; increases platelet levels of cAMP and thus inhibits platelet activation/aggregation; also a vasodilator
- Nitric oxide- Secreted by endothelial cells; acts locally to inhibit platelet activation; potent vasodilator
What are some characteristics of Acute MI?
- Discrete focus of ischemic necrosis in the heart
- Development related to duration of ischemia and metabolic rate of ischemic tissue
- 20-30 minutes of ischemia can cause infarct
- Frequently result of acute plaque change with coronary artery thrombosis
- Dissolution of thrombus frequent within 12-24 hrs
- Infarcts involve LV more commonly and extensively than RV
What is a transmural infarct?
Spans the entire thckness of myocardium; due to prolonged, total occlusion of an epicardial coronary artery (LAD, LCx, RCA or one of the major branches)
What is a subendocardial infarct?
Involves only the innermost layers of the myocardium (most susceptible to ischemia due to poor collateral flow, adjacent to high pressure ventricle, furthest from epicardial coronaries)
The amount of tissue that succumbs to infarction depends on?
- Mass of myocardium perfused by coronary artery
- Magnitude and duration of ischemia
- Oxygen demand of affected area
- Adequacy of collateral coronary flow (collateral flow is supplied by other coronaries)
- Degree of reperfusion and inflammatory response
The LAD supplies which portions of the heart?
- Anterior LV
- Anterior 2/3 septum
- Apical LV
The LCx supplies which portions of the heart?
- Lateral LV
- Posterolateral LV
The RCA supplies which portions of the heart?
- Posterior LV
- Posterior 1/3 septum
- Posterior papillary muscle
- Inferior or diaphragmatic
What are some of the early changes that occur during an MI?
- Rapid shift from aerobic to anaerobic metabolism (lactic acid accumulates)
- Reduction in ATP
- Rising Na+ leading to cellular edema
- Abnormal electrolyte/ion shifts increasing arrhythmia risk (Vtach, vfib)
Irreversible cell injury ensures in 20 min
What are the macroscopic features that occur less than 4 hours after infarction?
No abnormalities
What are the macroscopic features that occur at 4-12 hours after infarction?
Occasional dark mottling
What are the macroscopic features that occur at 12-24hours after infarction?
Dark mottling
What are the macroscopic features that occur at 1-3 days after infarction?
Mottling with developing yellow-tan necrotic center
What are the macroscopic features that occur at 3-14 days after infarction?
Maximally yellow-tan and soft, depressed red-tan borders
What are the macroscopic features that occur at 2-8 weeks after infarction?
Gray-white scar, progressive from border to core of infarct
What are the macroscopic features that occur at greater than 2 months after infarction?
Mature scar
What are the MICROroscopic features that occur less than 4 hours after infarction?
None, variable wavy fibers at border
What are the MICROroscopic features that occur at 4-12 hours after infarction?
Early coagulative necrosis, edema, hemorrhage, wavy fibers
What are the MICROroscopic features that occur at 12-24 hours after infarction?
Coagulative necrosis, nuclear pyknosis, hypereosinophilia, contraction band necrosis, early PMNs
What are the MICROroscopic features that occur at 1-3 days after infarction?
Extensive coagulative necrosis with loss of nuclei and striations, interstitial PMNs
What are the MICROroscopic features that occur at 3-14 days after infarction?
Early disintegration of dead myocytes, dying PMNs, macrophages and granulation tissue at border
What are the MICROroscopic features that occur at 2-8 weeks after infarction?
Gradual loss of cellularity, increasing collagen
What are the MICROroscopic features that occur greater than 2 months after infarction?
Dense collagenous scar
What are some of the impaired systolic changes that occur with MI?
Hypokinesis: Local region with reduced contraction
Akinesis: Local region with no contraction
Dyskinesis: Local region that bulges outward with contraction
What are some of the impaired relaxation/diastolic changes that occur with MI?
Reduced compliance and elevated ventricular filling pressures
What is stunned myocardium?
A functional change from an MI where there is a reversible period of contractile dysfunction. This takes days to weeks to recover
What is ischemic preconditioning?
Brief ischemia that renders tissue perhaps more resistant to future episodes of ischemia. MI following recent anginal episodes- less morbidity and mortality?
What are some of the ventricular remodeling changes that occur after MI?
- Changes to the geometry of the infarcted AND noninfarcted myocardium; ventricular dilatation
- Infarct expansion, myocyte side-to-side slippage
- Mechanically disadvantageous
- Increased wall stress
What are some MI complications?
- Arrythmias (account for 50% of deaths)
- LV failure, cardiogenic shock (infarct involves>40% LV, up to 90% mortality, high grade stenosis of coronary vessels)
- Extension of infarct (apparent in up to 10 of patients during 1st 2 weeks, significant extension twofold increased mortality)
- Myocardial free wall rupture
- Septal perforation (left to right shunt)
- Paillary muscle rupture (Mitral regurg, Massive MV incompetence)
- Aneurysm
- Mural thrombosis
What are some characteristics of Myocardial free wall rupture?
- occurs during first 3 weeks
- Most common days 1-4 when wall is weakest
- Complication of large infarcts (>20% of LV)
- Occur at junction of infarct and normal muscle
- Hemoperricardium and death from tamponade
- 10% deaths from AMI in hospitalized patients
What are some characteristics of aneurysm after MI?
- After transmural AMI, wall bulges outward during systole
- As infarct matures, fibrous scar progressively stretches
- Increased risk for myocardial rupture
- predisposes to mural thrombosis
- Increases workload
What are some characteristics of mural thrombosis?
- Seen in almost 50% of fatal AMI
- Especially after apical infarcts
- Predisposes to systemic embolization
What are MI symptoms?
- Chest pain-persistent, substernal
- nausea, vomitting, weakness (parasympathetic vagal effect)
- Diaphoresis, cool/clammy skin (sympathetic)
- Fever (inflammatory response)
- SOB
What are symptoms of MI during “typical chest pain” (increases liklihood
- radiation to arm or shoulder
- radiation to both arms or shoulders
- associated with exertion
- associated with diaphoresis
- associated with nausea or vomitting
- Worse than previous angina or similar to previous MI
- Described as pressure
What are symptoms of MI during “atypical chest pain” (decreases liklihood of AMI)
- Described as pleuritic
- Described as positional
- Described as sharp
- Reproducible with palpation
- Inframammary location
- Not associated with exertion
DDX for chest pain?
Cardiac: ischemia, pericarditis
Pulmonary: Pneumonia, Pleurisy, PE
MSK: COstochondritis, cervical radiculitis
GI: GERD, esophageal spasm, peptic ulcer disease, biliary colic
What is included in the physical exam for an MI?
- Airway, breathing, circulation
- Evidence of systemic hypoperfusion (hypotension, tachycardia, impaired cognition, cool extremities, end-organ injury)
- Evidence of heart failure (Elevated JVP, pulmonary crackles, Gallops-S3, S4, New murmurs)
What are EKG abnormalities in in myocardial schemia?
- New ST Segment elevation >/= 1mm (in setting of chest pain)
- New ST-segment depression
- New T-wave inversion
What are high risk MI features?
- Increased age
- Low BP
- Elevated HR
- HF
- Anterior location
Defining an MI includes what criteria?
- Detection of a rise/and/or fall of hs cardiac troponin with at least one value above the 99th upper reference limit
AND ONE OF THE FOLLOWING: - Symptoms of acute ischemia
- ECG: New (or presumed new) ST-T changes or LBBB; pathological Q waves
- Imaging: New loss of viable myocardium or regional wall motion abnormality
- Angiography or autopsy: Identification of an intracoronary thrombus
94-97% of troponins are located where?
Myofibrils
6-8% of troponins are?
cTNT
3-4% of troponins are?
cTnI in cytosol
Troponins are released during?
Cell death (necrosis or injury)
What is the criteria for diagnosis of MI using CK-MB (NOTE: CK-MB no longer used clinically for diagnosis but might appear on step 1)
CK-MB>upper limit of normal and >2.5% of total CK
where is CK-MM (CK-3) located?
skeletal muscle, cardiac, thyroid, and lung
Where is CK-MB (CK-2) located?
Cardiac tissue, skeletal muscle, stomach, small intestine, prostate, uterus (Non-cardiac increases: CO poisoning, malignant hyperthermia, muscular dystrophies, some malignancies)
Where is CK-BB (CK-1) located?
Brain, colon, intestine, stomach, uterus, thyroid
What are some noncardiac causes of Tn elevation?
- Acute heart failure
- PE
- Shock
- Aortic dissection
- Myocarditis
- Trauma
- ICD Discharge
Criteria for ST-elevation MI
- Presence of >1mm ST-segment elevation in at least 2 anatomically contiguous leads, or >2mm ST-segment elevation in 2 contiguous precordial leads
OR - New left bundle branch block
Contiguous leads II, III, aVF correspond to what anatomic location and coronary artery?
Inferior; RCA»LCx
Contiguous leads V2-V4 correspond to what anatomic location and coronary artery?
Anterior; LAD
Contiguous leads V1-V4 correspond to what anatomic location and coronary artery?
Anteroseptal; LAD
Contiguous leads 1, aVL, V5, V6 correspond to what anatomic location and coronary artery?
LCx>LAD
LBBB corresponds to what anatomic location and what coronary artery?
Anterior; LAD
Lead V4R corresponds to what anatomic location and what coronary artery?
Right ventricle; RCA
Leads V1, V2 with ST depressions correspond to what anatomic location and what coronary artery?
RCA»LCx
Electrically silent leads correspond to what coronary artery??
LCx
Pathologic Q waves are indicative of?
Prior transmural (ST elevation) MI
What are the diagnostic criteria for pathologic Q waves?
- Q wave should be >/= 1mm wide
- Q wave should be >25% of overall amplitude of QRS complex
- Pathologic Q wave should be present in >/= 2 contiguous leads
What is variant (prinzmetal) angina?
A focal coronary artery spasm in the absence of atherosclerotic lesions, that presents with CP and transient ST elevations >5-15 min in duration. Smooth muscle hyperractivity and endothelial dysfunction. Smoking increases risk
How do you diagnose variant (prinzmetal) angina?
Intracoronary acetylcholine provokes spasm (cardiac cath required)
How do you treat variant (prinzmetal) angina?
nitrates, CCBs
Who tend to have higher mortality, pts with ST elevation or NSTEMI?
NSTEMI
What are the risk stratification criteria in NSTEMI and UA (TIMI RISK SCORE 1 pt each?)
- Age>/= 65 years
- Known CAD (coronary stenosis >/=50%)
- > /= 3 risk factors for CAD
- ASA use within the past 7 days
- > /= 2 episodes of angina within the past 24 hours
- ST changes >/= 0.5mm
- Elevated cardiac markers
Other causes of ACS?
- Decreased myocardial oxygen supply (Decreased perfusion pressure due to hypotension i.e. septic shock. Severely decreased blood oxygen content such as marked anemia. Coronary artery dissection or emboli
- Increase in myocardial oxygen demand (rapid rachhyarrhythmias, acute hypertension, severe aortic stenosis)
