MI and Infarction Flashcards
What are determining factors of M ischemia??
- supply and demand
- intracavitary blood protects endocardial layer
- myocardial distance from epicardial coronaries
- myocardial oxygen demand: HR, contractility, wall tension
Which layer most susceptible to ischemia?
subendocardial layer - the blood has to get over the surface, through the epicardial layer and then finally the subendocardial layer– by that time a lot of the O2 has already been used
ST segments remain isoelectic when?
IF blood flow is normal then even durin inc demand ST segments are isoelectric
Inc oxygen demands and coronary blood flow is reduced
-what happens?
- subendocardial ischemia begins = ST segment changes
- T-waves invert (less reliable than ST segment)
T waves and ischemia- what happens?
-inverted!
What are hyperacute T-waves? When do you see them?
- tall and peaked T-wave = ischemia
- can only see at onset of ischemia - would need to have ECG set up on patient prior to even
ST segment depression of more than 2mm is a positive sign for:
subendocardial ischemia
ST elevation means what?
transmural ischemia (epicardial coronary occlusion)
coronary spasm-
atypical angina pectoris
(-preunsmtals angina?)
ischemia but occurs at rest!
-the coronary artery gets inc vasomotor tone = shut off flow due to some factor
ST elevation vs depression
elevation is transmural
depression is just subendocardial
ST segment elevation - which artery 90% of the time?
Which 10% of the time?
Right coronary
Left Circumflex
what is this j-point funkiness?
during decreased supply (myocardial ischemia) the junction point between the QRS and the T wave is distorted due to the hyperacute T-wave
What is myocardial infarction?
prolonged ischemia that moves toward necrosis
-necrosis begins at subendocarium and moves to epicardium
Myocardial infarction on ECG?
vs ischemia?
-ST, QRS, and T are ALL affected!
ischemia=ST and T sometimes and even less often QRS
Most useful ECG change for acute infarction?
-QRS!
