Normal EKG Flashcards
What portion of the P wave represents the right atrium?
First
What portion of the P wave represents the left atrium?
Second
What is a QS wave?
If the entire deflection is entirely negative
What is the second positive deflection of a QRS called?
R’ (R-Prime)
What is an RS wave?
A wave that starts positive and then goes negative before returning to baseline (without going positive again)
What is a QR wave?
A wave that starts negative and then goes positive before returning to baseline (without going negative again)
What is an R-wave?
If the entire deflection is entirely positive
What does the earliest portion of the QRS represent?
Depolarization of the septum by the septal fasicle of the LBB
What is the T wave usually much broader than the QRS wave?
Repolarization is a much slower process (remember the pumps)
What is the difference between a segment and an interval?
A segment connects to waves where as an interval contains the line and one of the two waves
What does the QT interval represent?
The time from the start of depolarization through the completion of repolarization
What is the degree for lead I?
0 degrees (left arm)
What is the degree for lead II?
60 degrees (left leg)
What is the degree for lead III?
120 degree (right leg)
What is the degree for aVL?
-30 degree (left shoulder)
What is the degree for aVR?
-150 degree (right shoulder)
what is the degree for aVF?
90 degree (straight down)
What are leads I and aVL often referred to as?
Left lateral leads
What is considered the only true right sided lead?
aVR
Where does the right ventricle lie in the body?
Anterior and medially
Where does the left ventricle lie in the body?
Posterior and laterally
What lead lies over the right ventricle?
V1
What lead lies over the intraventricular septum?
V2 and V3
What lead lies over the apex of the left ventricle?
V4
What lead lies over the lateral left ventricle
V5-6
What are considered the right leads on a standard EKG?
V1 and aVR
Why is the P wave usually biphasic in lead III?
It’s angle is 120 degrees and lies nearly perpendicular to the atrial current (usually 30 degrees)
What leads usually have a biphasic P wave?
III and V1 because the atrial current runs perpendicular to these leads
Describe the P wave usually found in aVR
Usually negative because
A normal septal Q wave won’t be bigger than what?
0.1 mV (1 small box)
What is the normal QRS morphology in aVR?
All negative (QS wave) since often the electricity is moving directly away
What precordial lead usually has the largest R-wave?
V5
Where is the transition zone usually for R-wave progression?
V3 or V4. This is where QRS complexes go from mostly negative to mostly positive.
Why are QRS and T waves usually congruently positive or negative together on a normal EKG if one is depolarizaton is one is repolarization?
Because repolarization usually starts in the apex and moves backwards up the heart
What is the QT interval proportional to?
Heart rate. For a faster heart rate the QT has to shorten (repolarize faster) so that the heart can fire again.
What percentage of time does the normal QT interval comprise of the cardiac cycle?
40%
What does cardiac hypertrophy mean?
Increased muscle mass (different than enlargement)
What is the usual cause of cardiac hypertrophy?
Pressure overload (think HTN or aortic stenosis)
What is cardiac enlargement?
Dilation of a particular chamber (different than hypertrophy)
What typically causes cardiac enlargement?
Volume overload (think about valve issues like mitral regurgitation)
What are three changes that can occur on an EKG when there is hypertrophy or enlargement?
- Increased duration of P wave or QRS due to more time needed for depolarization
- Increase in amplitude of wave 2/2 increased muscle mass
- The axis can shift 2/2 more current coming from that particular chamber
What is the normal axis for the QRS?
0-90 degress
What is the quick way of determining if QRS axis is appropriate?
Up in I and up in aVF (this means that waves have to be moving somewhere between these two)
What is right axis deviation?
QRS between 90 and 180 degress. Think up in III and avF. Will also be negative in I.
What is left axis deviation?
QRS between 0 and -90. This that the QRS will be positive in I and negative in aVF
What is extreme right axis deviation?
Between -90 and 180. Will be negative in I and aVF.
What is the normal P wave axis?
Between 0 and 70 degrees
What is the normal T wave axis?
Variable but should be between 50-60 degrees of the QRS
