34 Questions
What is the mean QRS vector?
The sum of all smaller vectors of depolarization
In which direction does the mean QRS vector normally point in the frontal plane?
Downward and to the patient's left
Why does the mean QRS vector point more left?
Due to the thicker LV having larger small vectors of depolarization
What is the axis direction if the QRS is upright in lead I, negative in lead aVF, and Lead II is downward (negative)?
Toward -120 with the presence of LAD
What can cause a right axis deviation (RAD) according to the text?
Limb lead reversal
Which condition does NOT lead to left axis deviation?
Right ventricular hypertrophy
What happens to the mean QRS vector if the heart is displaced?
It moves in the same direction as heart displacement
In ventricular hypertrophy, how does the mean QRS vector get displaced?
Toward the hypertrophied side
How is left axis deviation (LAD) defined in terms of degrees?
Between -30 and -90 degrees
What method is suggested for determining the QRS axis?
Finding the major direction of the QRS complex in leads I and aVF
Causes of RAD include normal variant and conditions such as right ventricular ________
hypertrophy
RAD can also be caused by preexcitation syndromes like Wolff-Parkinson-White syndrome and ventricular ________
arrhythmias
Dextrocardia is characterized by the apex of the heart being on the right side of the body, which can lead to ______.
right axis deviation
Limb-lead reversal, right ventricular overload syndromes, and ventricular tachycardia are also potential causes of ______
right axis deviation (RAD)
Another cause of RAD is right ______ enlargement
ventricular
The P wave on an ECG represents ventricular depolarization.
False
The QT Interval measures the contraction of the ventricle from the beginning of the Q wave to the end of the T wave.
False
A mean QRS vector pointing more left indicates right axis deviation (RAD).
False
LAD can indicate the presence of Left Anterior Fascicular Block (LAFB).
True
Mechanical shift of the heart in the chest due to conditions like lung disease can lead to Right Axis Deviation (RAD).
True
Right Axis Deviation (RAD) can be caused by Ventricular Arrhythmias like atrial fibrillation.
False
The QT interval should be less than the preceding R-R interval.
True
The J point is the junction at which the S wave meets the ST segment.
True
A 12-Lead EKG consists of 6 limb leads and 6 precordial leads.
True
The mean QRS axis provides information about the overall electrical activity of the heart.
True
Which condition can cause left anterior fascicular block or LBBB, leading to left axis deviation (LAD)?
Left ventricular hypertrophy
Which of the following is a potential cause of mechanical shift of the heart in the chest, leading to right axis deviation (RAD)?
Pulmonary embolism
What is the normal duration of a Q wave on an ECG?
Less than 0.04 seconds
In which phase of the cardiac cycle does the ST segment occur?
Repolarization
How is the QTc interval calculated?
QT interval + square root of RR interval
Which leads are associated with Lateral Wall MI?
I, aVL, V5, V6
What is a potential EKG finding in Posterior Wall MI?
Tall R waves in V1 and V2
During which stage does part of the myocardium become electrically inert?
Stage II: Infarction
What is the potential consequence of right axis deviation?
Right ventricular strain
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