EKG Ch. 6 Flashcards
Axis (25 cards)
What does the axis refer to in the context of the heart?
The general direction of electrical conduction through the heart.
What does the QRS complex represent?
Ventricular depolarization.
How is the axis categorized for each patient?
Normal, left, right, or indeterminate.
Which leads are most important in determining the axis?
Leads I and aVF.
What is the normal vector direction in terms of axis?
Points down and to the patient’s left side.
What are the degrees associated with lead I?
0 to 180 degrees.
What does lead aVF represent in terms of axis?
Runs from head to toe, forming a right angle with lead I.
What are the four quadrants defined by the intersection of leads I and aVF?
Normal, left, right, and indeterminate.
What is the mean QRS vector range for a normal axis?
0 to +90 degrees.
What does a right axis indicate in terms of mean QRS vector?
+90 to +180 degrees.
What indicates a left axis deviation?
Mean QRS vector from 0 to −90 degrees.
What is referred to as No Man’s Land in axis determination?
Mean QRS vector between −180 and −90 degrees.
True or False: An extreme axis deviation can be a normal variant.
True.
How can the axis quadrant be determined?
By examining leads I and aVF.
What does a positive QRS in lead I indicate?
The axis points toward the patient’s left.
What is the significance of lead II in axis determination?
Runs from 60 to 120 degrees, terminating at the left foot.
How can the mean axis be determined in degrees?
Identify the isoelectric lead and move 90 degrees in the direction of the positive QRS.
What does the term borderline axis deviation refer to?
The mean QRS axis is oriented toward the lead with the most positive QRS deflection.
What can cause a leftward axis deviation in a patient?
Obesity causing upward pressure from increased abdominal tissue.
What is a potential cause of right axis deviation (RAD)?
Pulmonary diseases such as chronic obstructive pulmonary disease (COPD).
What is the relationship between myocardial infarction and axis deviation?
The mean axis will point away from the area of infarction.
List two causes of left axis deviation.
- Left bundle branch block
- Inferior wall myocardial infarction
List two causes of right axis deviation.
- Right bundle branch block
- Chronic obstructive pulmonary disease
Fill in the blank: An EKG can be described as having a normal axis if the mean QRS vector lies within _______.
0 to +90 degrees.
