Ischemia Flashcards
What is important to know about the phases of ischemia to irreversible infarction (losing cells)
- Hyperacute T waves
- Infarction (inverted T waves)
- ST segment elevation
- Switch from an R wave to a Q wave (shows irreversible cell death)
What is a T wave indicative of?
Ventricular repolarization
What makes a hyperacute T wave for MI
ST segment blurs into the T wave
Broad Width of the T wave that goes up to a mountain top (rounded rather than pointed)
no strict rules, just has to be big essentially (typically at least 1/3 or 1/2 of the QRS complex)
different leads may be normal, and abnormal ones suggest the location of where the infarction may be (anterior leads for example)
What is segment serves as a baseline for an EKG?
The PR segment
After seeing hyperacute T waves, what do you see an MI progress to include?
Elevated ST segment
What is an elevated ST segment?
ST segment is at least 2 boxes above the PR segment
What type of ST segments tend to be a better prognosis?
If you could put two dots over it and it makes a happy face = good
sad face = bad
NOT ALWAYS THE CASE
What is the J point?
The junction between the QRS (end of depolarization) and the ST segment
What is an elevated J point?
J point that is above elevation of the PR segment. The ST segment is horizontal though.
Can be a normal finding in healthy young patients, but it can signify the beginning of ST elevation
What 2 factors tends to suggest a non-concerning, normal variant J point elevation on a 12 point lead?
- The patient is young
- The J-point is diffuse throughout random parts of the lead (unlikely to infarct the entire heart)
What is considered the first negative deflection?
Q wave
What 2 criteria are necessary to be considered a pathologic Q wave?
1) at least 1 box wide (0.04 seconds)
2) depth at least 1/3 the QRS complex (dips down at least 1/3 the total it goes back up to)
What is a pathologic Q wave indicative of?
Late stage MI
How do you localize an infarction?
The abnormalities are in a WHOLE group
if in one lead, there is NOT an infarction, because the groups are looking at the same part of the heart.
What are the anterior leads?
V2, V3, V4 (LAD lesion)
What are the lateral leads?
I, aVL, V5, V6 (Circulation)
sometimes just I, aVL or V5 and V6
What are the inferior leads?
II, III, aVF (RCA lesion)
What are the Right-sided leads?
aVR, V1
What are the septal leads?
V2, V3 (LAD lesion)
What are reciprocal changes?
One side is infracting (so the depolarization and repolarization are abnormal), so the other side of the heart will compensate:
example: ST elevation on one side of the heart leads to ST depressions (opposite)
The ST elevations are the problem, and the ST depression is the heart’s response, not the other way around
are reciprocal changes always present?
No - but if present, it is highly suggestive of MI
If you have an inferior wall MI, where do you see reciprocal changes?
Anterior or lateral walls
MI on which wall(s) of the heart leads to inferior reciprocal changes?
ALL OF THEM, except for the inferior wall itself
Septal
Anterior
Lateral
What are the 3 steps of diagnosing a STEMI/MI?
- Look at entire EKG for T wave, ST segment changes – up or down, or pathologic Q waves
- If changes are noted, determine if the change is present in a group of leads
- If there is ST segment elevation in a group of leads, look for reciprocal ST segment depression in another group to support diagnosis of STEMI
