MI

Question 1

STEMI ECG

Answer 1

• ST segment elevation of 2 mm or more at J point in V2-V3 in men; 1.5 mm or more in women in absence of LVH or 1 mm or more in 2 or more contiguous chest or limb leads
• T wave ischemic pattern – inverted T waves or tall, peaked T waves
• “transmural” – large Q wave
• New LBBB (obscures ST elevation analysis)
• May need serial tracings

Question 2

STEMI causes

Answer 2

atherosclerosis, vasospasm, vasculitis, dissection, genetics

Question 3

STEMI hx

Answer 3

• Chest discomfort, more severe than angina
• Heavy, pressure, crushing, etc
• Retrosternal, left, across chest; neck, jaw, left arm, epigastrium
• N/V, diaphoresis, dyspnea
• Not reliably relieved by Nitro or rest
• 20% painless – DM, elderly women

Question 4

Physical exam findings for STEMI

Answer 4

• Normal
• S4 Gallop – atrial beating forcefully against less compliant, stiffened ventricle
• BP variable
• Sympathetic hyperactivity (increased HR, increased BP) seen in anterior MI
• Parasympathetic hyperactivity (bradycardia, decreased BP) in inferior MI
o GI manifestations
• Heart failure – S3, crackles, increased JVD, new murmur

Question 5

Early Acute phase for MI

Answer 5

• T wave increased amplitude
• Hyper-acute pattern
• Convex upward ST pattern

Question 6

Chronic phase for MI

Answer 6

• Resolution of ST elevation is variable (2 weeks for inferior wall, later for anterior wall)
• Persistent ST elevation (after 2 weeks) think ventricular aneurysm

Question 7

Zones of Infraction

Answer 7

o Infarction – dead tissue, lacks depolarization
• Q waves
o Injury – deficient blood supply, inability to fully polarize
• ST Segment shifts
o Ischemia – deficient blood supply, impaired repolarization
• T wave changes

Question 8

Posterior wall infarctions

Answer 8

reciprocal changes in anterior leads
o V1 and V2
• Prominent R wave (reciprocal of posterior Q wave)
• Upright T waves (reciprocal of inverted T wave)
• ST depression (reciprocal of ST elevation)

Question 9

Labs in MI

Answer 9

o Increased WBC 12,000-15,000 (hours to 2-4 days)
o Increased CRP
o BNP – increased in ventricular wall stress and fluid overload

Question 10

Troponin I

Answer 10

• 1-4 hrs detectable after onset AMI
• 10-24 hour peak
• Persists 5-14 days
• Renal failure can cause false positive cTnT (clearance route)

Question 11

non-MI cardiac causes for elevated troponin level

Answer 11

• Myocardial injury, inflammation
• Heart Failure
• Cardiomyopathies
• Aortic dissection
• Severe aortic stenosis
• Tachycardia

Question 12

Pulmonary causes for elevated troponin

Answer 12

• PE, pulmonary HTN, respiratory failure

Question 13

Neurologic causes for elevated troponin

Answer 13

stroke, intracranial hemorrhage

Question 14

Other causes of elevated troponin

Answer 14

• Shock: septic, hypovolemic, cardiogenic

* Renal failure

Question 15

Standard of care STEMI

Answer 15

o 12 lead ECG with continuous cardiac monitoring
o IV lines inserted
o Cardiac enzymes (cTnI), CBC, CMP, PT, PTT

Question 16

Primary percutaneous coronary intervention (PCI)

Answer 16

with angioplasty and stenting
• Within 12 hours
• Lower mortality rate and intracerebral hemorrhage

Question 17

Cath lab

Answer 17

within 90 minutes

• Transport to other hospital if needed within 120 min

Question 18

Fibrinolysis (clot busters)

Answer 18

• Fibrinolytic or Thrombolytic
• Begun in ED within 30 minutes
• Useful for STEMI or new LBBB within 12 hours of onset of symptoms
• Major risk is intracerebral hemorrhage
• Contraindication with active bleeding at any site (ex. GI, GU (except menses))

Question 19

Reperfusion therapy

Answer 19

• Accelerates changes over minutes to hours

* Failure of ST elevation to resolve by >50-70% within 1-2 hours, suggests failure of fibrinolysis

Question 20

Initial medical management of STEMI

Answer 20

o	ASA (162-325 mg) PO – given on presentation – unless contraindicated
•	Helps prevent platelet aggregation

o IV Heparin or Enoxaparin
• Adenosine diphosphate receptor (p2Y12) inhibitor
• Antiplatelet agent
• Use for 1 year after PCI for STEMI with stenting to prevent stent stenosis

Question 21

Treatment of STEMI

Answer 21

o Nitroglycerin – relieve vasoconstriction, relieve pain, reduce pre and afterload
o Morphine – persistent pain
o Beta blocker – esp if increased BP or increased HR
• Don’t use in decompensated HF, decreased HR or BP, MCO2
o Oxygen
o Stool softener (avoid valsalva)
o ACEI – helpful if low EF, increased BP – prevent remodeling
o Coronary ICU – AHA diet

Question 22

Complications of MI - pericarditis

Answer 22

• 2-4 days post MI
• 2-10 weeks after MI could be Dressler syndrome (immune mediated)
• Hurts to breathe, feels better leaning forward
• Friction rub
• Tx: ASA, NSAID

Question 23

Complications of MI - Arrhythmias

Answer 23

o	Ventricular rhythm disturbance
•	Occur early
•	VF in 1st 4 hours – treat via elective cardioversion
•	VT
•	VT (polymorphic VT)
•	VF

o Accelerated Idioventricular Rhythm
• Slow VT (60-100/min)
• After fibrinolytic therapy
• Benign, still irritable

o Atrial fibrillation - First 24 hours (5-10%)

o Sinus Bradycardia
• Included parasympathetic tone
• Associated with inferior MI (up to 40%)

o Second degree AV Block (Wenckebach)
• Associated with inferior wall MI

Question 24

Complications of MI - HF

Answer 24

leading cause of death after AMI
• LV dysfunction – S3, S4 crackles
• RV infarction – 10-30% of inferior STEMI
• Decreased BP, clear lungs, increased JVP
• Kussmaul sign (distention of jugular vein on inspiration)
• Treat with IV fluids
• Cardiogenic shock – decreased BP, decreased CI (>1.8 L/min/m2)
• Increased Pulmonary capillary wedge pressure (PCWP) >18 mmHg
• Mortality 70-80%

Question 25

Mechanical complications of MI

Answer 25

* Acute mitral valve regurgitation – infarction related rupture or dysfunction of papillary muscle * New holosystolic murmur associated with inferior wall MI * Treatment – surgery

Question 26

Complications of MI - VSD

Answer 26

o Septal Rupture with Ventricular Septal Defect (VSD) – associated with anterior wall MI • LV free wall rupture – causes tamponade • LV aneurysm- associated with anterior MI • Treat with surgery

Question 27

Thromboembolic complications of MI

Answer 27

* Arterial emboli from LV aneurysm | * Cause stroke, ischemic bowel

Question 28

RV infarction

Answer 28

o Proximal occlusion of RCA before acute marginal branch • Cause acute inferior wall MI in 30% of cases o Use right chest leads o ST elevation of 1 mm or more in V4-V6 R o Pericarditis, myocarditis, stress induced (takotsubo) syndrome, early repolarization

Question 29

DDX for STEMI

Answer 29

pericarditis, myocarditis, stress induced (takotsubo) syndrome, early repolarization

Question 30

Echocardiogram

Answer 30

o Global and RWM abnormalities o Murmur, Papillary muscle dysfunction, VSD o LV free wall rupture, LV aneurysm o Mural thrombosis