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Exam Two Study Guide

Terms in this set (29)

ST segment elevation in leads II, III, and aVF is indicative of a(n) ___________ infarction.

Which artery is obstructed?
Reciprocal changes?
inferior

The right coronary artery is obstructed.

Reciprocal changes in leads I, aVL, and V leads.
ST segment elevation in leads V1 and V2 is indicative of a(n) ________ infarction.

Which artery is obstructed?
Reciprocal changes?
septal wall

The left coronary artery (septal branch) is effected.

No reciprocal changes.
ST segment elevation in leads V2-V4 is indicative of a(n) _________ infarction.

Which artery is obstructed?
Reciprocal changes?
anterior

The left anterior descending artery is obstructed.

Reciprocal changes in leads II, III, and aVF.
ST segment elevation in leads I, aVL, and V5-V6 is indicative of a(n) ___________ infarction.

Which artery is obstructed?
Reciprocal changes?
lateral

The left circumflex artery is obstructed.

Reciprocal changes are possible in leads II, III, and aVF.
Normal PR interval duration?
0.12-0.20 seconds
Normal QRS complex duration?
0.06-0.10 seconds
What does the P wave represent?
atrial depolarization
What does the QRS complex represent?
ventricular depolarization
What does the T wave represent?
ventricular repolarization
When does atrial contraction occur (in respect to ECG waves)?
after the P wave
When does ventricular contraction occur (in respect to ECG waves)?
after the QRS complex
What are the characteristics of PVCs?
PVCs are "extra" beats that occur early in the cycle.

- are not preceded by a P wave
- T wave is in the opposite direction than the QRS
- wide and distorted QRS
- typically followed by a full compensatory pause
- arise from the ventricles
The SA and AV nodes are primarily supplied by which coronary artery?
the right coronary artery
When are PVCs considered particularly dangerous?
- When they occur in more than 1 in 10 beats
- When they occur in groups of 2 or 3
- When they are multifocal
- When they occur in or near a T wave
Which is lead is best to look at atrial hypertrophies and why?
V1, because it is directly over the atria.
ECG characteristics of right atrial hypertrophies
- Beginning portion of the diphasic P wave is larger/taller
- Tall, peaked P waves (>2.5-3mm) in leads II, III, and aVF
ECG characteristics of left atrial hypertrophy
- Terminal portion of diphasic P wave is larger/taller
- Broad, notched P waves (>0.10 seconds) in leads I, aVL, and V4-V6
ECG characteristics of left ventricular hypertrophy
S in V1 or V2 and R in V5 or V6 is >35mm
ECG characteristics of right ventricular hypertrophy
- large R waves in V1
- R waves become progressively smaller from V1 through V4
What is the most common cause of LVH?
hypertension (HTN)
ECG characteristics of right bundle branch block (RBBB)
- QRS duration >0.12 seconds in leads V1-V2
- RSR' in V1-V2
- positive QRS in lead V1
ECG characteristics of left bundle branch block (LBBB)
- QRS >0.12 seconds in V1 and V2
- broad RSR' in I, aVL, and V5-V6
ECG characteristics of left anterior hemiblock
small r waves and deep S waves in II, III, and aVF
ECG characteristics of left posterior hemiblock (LPH)
- small r waves in I and aVL
- deep S waves in I
Characteristics of an abnormal Q wave?
- >1mm wide
- >0.04 seconds in duration
- 1/3 the size of the QRS complex
What do Q waves indicate?
the presence of a current (accute) or past MI
With MIs in mind, what do ECGs show in ischemia, injury, and necrosis?
ischemia --> ST segment depression or T wave inversion

injury --> ST segment elevation

necrosis --> Q waves
What characteristic on an ECG indicates the presence of an acute (current) MI?
the presence of ST segment elevation
Regarding the hexaxial reference system, what degree ranges indicate normal axis deviation, right axis deviation, left axis deviation, and extreme deviation or no man's land?
NAD: 0 to +90 degrees
RAD: +90 to +180 degrees
LAD: 0 to -90 degrees
EAD: -90 to +180 degrees
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