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!
Later ECG result of myocardial infarction?
-why?
- From necrosis get Q-wave
- Q-waves=myocardial activation in normal tissue segments away from the affected area
Pathologic Q-wave definition on ECG:
> 0.03sec in duration
-if in 2, 3 (and sometimes V1 but depends on anatomy) then abnormal
Daignostic in leads V1-3 then we have:
- name the infarction?
- which artery?
-Anterior myocardial infarction - in the left ant descending coronary artery
Diagnostic in Leads I and avL then we have:
- name the infarction?
- which artery?
-Lateral myocardial infarction - in the left anterior descending coronary artery - high diagonal branch goes to high lateral wall of left ventricles
Diagnostic in Leads V4-V6 then we ahve:
- name the infarction?
- which artery?
- inferolateral; posterolateral infarction
- Left ant descending - some other branch
Diagnostic in Leads 2,3 an avF then we have:
- name the infarction?
- which artery?
- inferior infarction
- post descending (right coronary)
Diagnostic in Lead V1-V3 (R-wave) then we have:
- name the infarction?
- which artery?
- posterior infarction
- left circumflex artery
Anterior MI feature on ECG?
-small Q wave in V3
Anterior Superior MI (high lateral) - features on ECG?
- no or tiny nub R-wave in V1
- larger R wave in V2
- 3mm R wave in V3
Postero-Larteral MI
-features on ECG?
-Loss of R wave or tiny R wave?
Inferior wall MI
-feature on ECG
-pathologic Q-wave in 2, 3, avF with some ST elevation
True posterior (high part by the crux) MI -feature on ECG?
tall and wide R waves in V2 and V3 (pathologic R waves)
-mirror test confirms true posterior MI bc you can see the ST elevation? I dont know
