MI Flashcards
Best Discriminator of MI w/n 3 hours of chest pain onset
EKG
Transmural MI, injury and myocardial ischemia
- full thickness
- usually L ventricle 2* to coronary artery disease
MI diagnosis
At least 2 of 3:
- symptoms >20min
- EKG changes (at least 2 leads)
- Enzyme changes
ST Segment Elevation
>6 months =
ventricular aneurysm
After 3 hours best discriminant of MI is
creatine kinase MB
Reciprocal EKG changes
- indicative of large MI
- in leads opposite of TM MI
- change is transient
- ST segment depression with T wave upright
Myocardial Ischemia
- Zone of Ischemia: functioning tissue at periphery of infarct
- T wave increased size & peaked & symmetrical for 1st several hours
- T wave inverts after 24-48 hours
- After 1st week T gets upright
Myocardial Injury
Zone of Injury: nonfunctional area around infarct
- indicates acute MI
- ST Elevation >1mm
- ST segment normal by 72 hours
Myocardial Infarct
Zone of necrosis: irreversible damage at center of MI
- significant Q wave >0.04 sec (any lead but III & aVr)
- w/n 48 hours & never go away
EKG with MI
- Significant Q wave (>0.04 sec)
- occur w/n 48 hours
- never goes away
EKG with Myocardial Ischemia
- incr T wave; peaked and symmetrical
- initially & for 1st several hours
- 24-48 hours after MI: T wave inverts
- becomes upright after 1st week
EKG with Myocardial Injury
- ST segment elevation
- > 1mm over baseline (2 small boxes)
- immediately
- returned to normal by 72 hours
Potassium
resting membrane potential
Calcium
threshold potential
Low K+
-membrane potential lower
High K+
-membrane potential higher
Low Ca++
-threshold potential lower
High Ca++
-threshold potential higher