Lecture 4- Axis Flashcards
Normal width of QRS (duration)
< 0.12 seconds (3 small boxes)
Where should you measure the QRS width?
Should be measured in several different leads- use the widest one
Causes of wide QRS?
- Hyperkalemia
- Medications (especially tricyclics)
- Ventricular tachycardia
- Idioventricular rhythms
- WPW
- Bundle branch blocks (BBB) and intraventricular conduction delay (IVCD)
- PVCs
- Aberrantly conducted complexes
- Pacemaker
Where does a pacemaker stimulate from?
Right ventricle (ventricular paced)
These are large deflections at the end of QRS complex (much larger than benign notching) and occur in cases of severe hypothermia.
Osborn waves
Benign notching?
- Small notch at end of QRS complex
- Most common in precordial leads
- Generally associated with benign causes of ST elevation: early repolarization, pericarditis
What is this difference between benign Q waves and pathologic?
- Insignificant Q waves = first vector of ventricular depolarization
- Significant Q waves = old MI in that region
What comes to mind when considering Q waves and respiration?
-Depth of the Q wave can vary slightly with respiration if axis of heart changes (obese/pregnant/ascites)
In what lead are Q waves common?
In aVR and generally not significant.
Criteria for pathologic Q waves?
- > 1/3 total height of QRS
- 0.04 seconds wide (one small box)
What is the Transition Zone? Where is it located?
Transition from mostly negative to mostly positive complex in precordial leads. Between V3 and V4.
Define early and late transition?
- If before V3, axis rotated counter-clockwise = early transition
- If after V4, axis rotated clockwise = late transition
If your V2 net deflection is positive, what type of deflection is this?
Early.
The QT interval, generally defined?
Should be less than ½ the R-R interval
Torsade de Pointes is indicative of?
Prolonged QT
What does Axis help us diagnose?
- Left or Right Ventricular Hypertrophy
- Hemiblock
- Pulmonary Embolus
- Dextrocardia
- Lead Misplacement
Incorrect lead placement would cause what to happen when looking at the EKG?
-Will see negative P and QRS in Lead II and positive P and QRS in aVR (opposite from normal)
(If arm leads are not switched and this occurs = dextrocardia)
What leads are used for determining Axis?
Limb leads (frontal or coronal plane)
Two most important leads for determining Axis?
Lead I and aVR
In the Hexaxial System, each spoke is separated by ____ degrees.
30
Normal axis is located between ____ and ____
0 degrees (Lead I) and 90 degrees (aVR)
Negative aVR and positive Lead I = ?
Left axis deviation
Negative Lead I and positive aVR = ?
Right axis deviation
What is the Indeterminant Axis?
aka “No Man’s Land”, extreme LAD, or extreme RAD. (negative in Lead I AND aVR)
