MI Flashcards
Myocardial infarction
Ischemia w/ injury or necrosis
Sx: (same as unstable angina) CP – radiates to neck and left arm Diaphoresis Tachycardia Dyspnea Nausea
EKG changes Elevated cardiac enzymes -CK-MB, CK -Troponin I -myoglobin
Less than 20-40 min – reversible
>20-40 min – irreversible
Acute coronary syndrome (ACS)
Elevated cardiac enzymes:
STEMI
NSTEMI
Unstable angina
STEMI vs NSTEMI
STEMI:
ST elevations
CP w/ new LBBB
Change cardiac enzymes
NSTEMI: No ST elevations \+/- ST depression \+/- T wave inversion change cardiac enzymes
Non-MI causes of elevated cardiac enzymes
Heart failure
Rapid a-fib
Myocarditis
Sepsis
Serial cardiac enzymes
Troponin I – most specific to cardic m.
-rises after 4 hours, elevated for 1-2 wks
CK-MB – more specific to cardiac m.
CK – any m. damage
If negative, recheck in 3-6 hours
Order of most likely coronary arteries occluded to cause MI
MC: LAD -> anterior wall MI
2: right coronary a.
3: circumflex branch of LCA
Evolution of MI – first day
0-4 hours:
risk: arrhythmias
4-12 hours:
Gross: Dark mottling
Micro: Necrosis, hemorrhage
Risk: arrhythmias
12-24 hours:
Gross: dark mottling
Micro: contraction bands (reperfusion inj), coagulation necrosis (spills contents) -> neutrophil immigration
Risk: arrhythmias
Evolution of MI – 1-3 days
Gross: dark mottling, hyperemia (redness at infarct
Micro:
Coagulation necrosis
Extensive inflammation
Neutrophil infiltration
Evolution of MI 3-14 days
Gross: yellow-tan softening
Micro:
Macrophage infiltration -> remodel damaged area
Risk:
ventricular aneurysm
wall rupture -> cardiac tamponade
Papillary m. rupture
Evolution of MI over 2 weeks
Gross: gray-white scar
Micro:
Increased collagen deposition
Decreased cellularity
Risk:
Dressler Sn: pericarditis w/ persistent fever
Ventricular aneurysm – no muscle, scar tissue bulges w/ each contraction
ECG evolution of MI – acute, hours, day 1-2, days later, weeks later
Acute:
ST elevates – tombstoning
-Prinzmetal angina
Hours:
ST elevated
R wave decreases
Q wave appears
Day 1-2
T wave inverts
Q wave deepens
Days later
ST normal
T wave inverted
Weeks later
ST normal
T wave normal
Q wave persists
ECG changes w/ MI
Always compare to previous ECG
ST segment elevation of at least 1 mm in two contiguous leads
T wave inversion
New LBBB
New Q waves at least 1 block wide or 1/3 height of total QRS complex
Transmural vs subendocardial
Transmural: Entire wall – endo/myocardium Atherosclerosis of major coronary A. Necrosis present ST elevation -> Q wave
Subendocardial:
Less than 50% wall – endo/myocardium
Small areas of LV, ventricular septum, or papillary muscles
ST depression
MI complications
Cardiac arrhythmia – electroirritability of heart – N0 and M0
-Vfib most lethal
Ventricular failure and pulmonary edema
S4
Cardiogenic shock – LVF
-low BP
Ventricular free wall rupture
Cardiac tamponade
Papillary m. rupture – 5 d layter
-> severe mitral regurg
Intraventricular septal rupture -> VSD
Ventricular aneurysm – scar bulges w/ contraction
Embolism from mural thrombosis -> stroke
-tx warfarin and heparin
Fibrinous pericarditis – 3-5 days post
- friction rub
- lean forward improves sx
Dressler sn – autoimmune
-pericarditis weeks after MI
Left anterior descending a. on ECG
Anterior wall
V1-V4 (V5)
ST elevated or inverted T
