Ischemic EKG Changes Flashcards Preview

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Flashcards in Ischemic EKG Changes Deck (12):
1

15 Steps to Reading an EKG

Rate
Rhythm
Axis
P wave
PR interval
Q waves
QRS interval
ST segment
T waves
U waves
QT interval
Hypertrophy
Infract
Alternans
Old ECG

2

EKG Changes in Ischemic Conditions

Q waves
ST segments
T waves
U waves
Infarct
Old EKG

3

ST Depression vs. Elevation

ST Depression:
Unstable angina (troponin negative)
Non-ST Elevation Myocardial Infarction (NSTEMI) (troponin positive)

ST Elevation: ST Elevation Myocardial Infarction (STEMI) (troponin negative)

> 0.5 mm of change from baseline should start to get your attention
> 1 mm ST segment deviation is abnormal (one small box)

4

Distribution of the Leads vs. Areas of the Heart

V1-6 = anterior
V5 and 6: low lateral
I and aVL = high lateral
II, III, and aVF = inferior

V1 and 2 = anterior septal/setpal area
V3 and 4 = anterior area
V5 and 6 = lateral area or anteriolateral area
aVL and I = lateral or high lateral area; signify circumflex distribution
II, III, and aVF = inferior distribution
V1-6 = LAD distribution

5

EKG Findings and Localization of Injury

Positive Predictive Value in Localizing Site of Injury:
Q waves = 98% (good)
ST Elevation = 91% (good)
T Wave Inversion = 89% (good)
ST Depression = 60% (bad)

6

Pathophysiology of ST Depression

In resting/repolarized state the ischemic area is depolarized and generates electrical currents towards the overlying leads
T-P and P-R segments are actually shifted “up” in resting state
Thus when entire ventricle is depolarized it appears that the ST segment is “depressed”

7

Pathophysiology of ST Elevation

In resting/repolarized state the ischemic area is depolarized and generates electrical currents away from the overlying leads
T-P and P-R segments are actually shifted “down” in resting state
Thus when entire ventricle is depolarized it appears that the ST segment is “elevated”

8

Types of ST Elevation

Sad = STEMI
Happy = Consider pericarditis, early repolarization or other causes

9

Q Waves

Always normal: aVR, V1
Always abnormal: V2, V3

Pathological Q waves: two consecutive leads with a duration of 3/4 small box or more + depth of 1 small box

If pathological = Indicates infarction
No ST elevation = Age-indeterminate
ST elevations = Acute infarct

10

Pathological Q Wave Determination

Q wave becomes deep and wide
Days and weeks occur = ST elevation will go back to normal but Q wave stays

Therefore Q wave with no ST elevation, not acute occurrence but it happened sometime

If Q wave + ST elevations then acute

11

T Waves

T wave is ventricular repolarization and every lead, the QRS and T wave should go in the same direction
This occurs because repolarization occurs in opposite direction of depolarization

T wave inversions occur in lead when polarity between the two is not correlating
When associated with ischemia they:
Are usually inverted (symmetrically) or biphasic
May help with localization to a particular portion of the left ventricle (but not as predictive as Q waves and ST elevation)

12

U Waves

Occurs right after T Wave
Best seen in V2 and V3
Rarely seen
Often seen with bradycardia
Pathological if: > 1.5 mm in height or Inverted (ischemia)