Electrophysiology Axis Deviation
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Transcript of Electrophysiology Axis Deviation
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ElectrophysiologyAxis Deviation
EXSC 531Clinical Exercise Physiology
J. Larry Durstine, PhDProfessor and Chair
Exercise Science DepartmentSchool of Public Health
University of South Carolina
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Learning Objective
• At the end of this lecture, students will be able to understand the concept of axis deviation and determine axis deviation with special considerations.
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Lecture Outline
• Determine axis deviation
• Understand normal physiologic reasons for deviation.
• Understand pathologic reasons for deviation.
• Steps for determination
• Special consideration
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Axis Deviation Determination
If we add up all the small vectors of ventricular depolarization (considering both direction and magnitude), we have one large“Mean QRS Vector” which represents the general direction of ventricular depolarization.
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Axis Deviation Determination
In myocardial infarction there is a necrotic (dead) area of the heart that has lost its blood and does not depolarize. The unopposed vectors from the other side Draw the Mean QRS vector away from the infarct.
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Axis Deviation Determination
Axis is the Mean QRS vector when give in degrees, and the normal axis range is 0 to +90o in the frontal plane.
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Axis Deviation Determination
In the frontal plane, there are 4 possible axis quadrants where the Mean QRS Vector may point. Visualize this large circle on the patient’s chest in the frontal plane.
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Now, by looking at the QRS complex in I and AVF, you can locate the Mean QRS Vector in an Axis quadrant (in the frontal plane asit relates to the patient)
Determination of Axis Deviation
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Degrees of Deviation
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Axis Deviation Determination• For this method we will use only the limb and
augmented leads• Step 1 Determine quadrant
– Check leads I and AVF• Step 2 Determine the isoelectric lead
– Where the QRS has “nearly” equal positive and negative deflections
• Step 3 Move into the determined quadrant (from step 1) at a 90 degree angle
• Special consideration – If the isoelectric lead is I, what is the
quadrant?– If the isoelectric lead is AVF, what is the
quadrant?
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Determine Quadrant
• Check leads I and AVF
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Determine the Isoelectric Lead
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Move at a Right Angle
• Move into the determined quadrant (from step 1) at a 90 degree angle
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Determination
of
Axis I
IIIII F
LR
I II III R L F
1. Determine Quadrant.
2. Determine Isoelectric lead.
3. Move at right angle toward quadrant.
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I
IIIII F
LR
I II III R L F
Determination
of
Axis
1. Determine Quadrant
2. Determine Isoelectric lead
3. Move at right angle toward quadrant
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1. Determine Quadrant
3. Move at right angle toward quadrant
I
IIIII F
LR
I II III R L F
Determination
ofAxis
2. Determine Isoelectric lead
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I
IIIII F
LR
I II III R L F
Determinationof
Axis
1. Determine Quadrant
2. Determine Isoelectric lead
3. Move at right angle toward quadrant
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I
IIIII F
LR
I II III R L F
Determinationof
Axis
1. Determine Quadrant
2. Determine Isoelectric lead
3. Move at right angle toward quadrant
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Lecture Outline
• Determine axis deviation
• Understand normal physiologic reasons for deviation.
• Understand pathologic reasons for deviation.
• Steps for determination
• Special consideration
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Lead I Lead II avR avL avFLead III
L
I
IIFIII
R
F
2. Determine Isoelectric lead3. Move at right angle toward quadrant
Lead I
Lead I
Lead AVF
Lead AVF
1. Determine Quadrant
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1. Determine Quadrant
L
I
IIFIII
R
2. Determine Isoelectric lead
3. Move at right angle toward quadrant
Lead I Lead II avR avL avFLead III
AVFAVF
Lead ILead I
G
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Lecture Outline
• Determine axis deviation
• Understand normal physiologic reasons for deviation.
• Understand pathologic reasons for deviation.
• Steps for determination
• Special consideration
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Determination of Axis Deviation1. Mean vector2. Physiologic reasons for deviation3. Pathogenic reasons for deviation4. Steps for determination
• Determine quadrant– Check leads I and AVF
• Determine the isoelectric lead• Move into the determined quadrant at a 90 degree angle
5. Special consideration • If the isoelectric lead is I, what is the quadrant?• If the isoelectric lead is AVF, what is the quadrant?
Counting heart rates1. R to R
• Count off• Small box counting (1 and 5 contraction methods)
2. Three and six second3. Know reasons for using each