Atrial contraction ii should be present and upright 1

Atrial contraction
ii. Should be present and upright
1. If absent or inverted
a. Junction of rhythm
b. QRS complex
i. Ventricular depolarization

1. Ventricles are contracting
a. Ventricular contraction
2. Atrial repolarization happens during this time but it is hidden by
QRS complex because ventricular depolarization has a greater
amplitude
ii. 0.06- 0.12 seconds in duration (less than 2.5 small boxes!)
1. > 0.12 seconds
a. Wide
i. Delayed conduction through the bundle branches
1. Bundle Branch Block
ii. Abnormal conduction within the ventricles
iii. Early activation of ventricles through a bypass route
c. T Wave
i. Ventricular repolarization
1. Resting state
a. Ventricles are relaxing
ii. Usually same direction as qrs
iii. Upstroke
1. Occurs during the absolute refractory period
iv. Downstroke
1. Relative refractory period
a. Strong electrical stimulus can trigger depolarization
b. Heart is vulnerable here
v. Abnormals
1. Flattened/Inverted
a. Myocardial ischemia
2. Tall T waves
a. Hyperkalemia
d. PR Interval
i. Start of P wave to start of QRS complex
ii. Time needed for SA node stimulation, atrial depolarization, and
conduction of impulse through AV node
1. Beginning of atrial depolarization to ventricular depolarization
2. Conduction of impulse from the SA node through the internodal
pathway to the AV node and down to ventricles
iii. 0.12-0.20 seconds (less than 5 small boxes)
1. > 0.20 seconds
a. Prolonged
i. Due to increase conduction delay
1. Heart blocks (1st degree AV block)
2. < 0.12 seconds

a. Takes less time for impulse to make it from atria to
ventricles
i. Wolff Parkinson White Syndrome
e. ST Segment
i. End of QRS beginning of T
ii. Normal position is at isoelectric line
iii. Represents the completion of ventricular depolarization and the beginning
of ventricular repolarization
iv. Important for medical emergencies
1. MI
v. Elevated ST
1. Above the baseline
2. STEMI (Heart Attack!)
vi. Depressed ST
1. Below the baseline
2. Ischemia (lack of O2)
a. Chest pain or angina
f. QT Interval
i. Beginning of QRS to end of T
1. Less than half of the R-R interval
ii. Total time for ventricular depolarization and repolarization
1. Start of ventricular depolarization to end of ventricular
repolarization
iii. As heart rate decreases
1. QT interval lengthens
iv. As heart rate increases
1. QT intervals shorten
v. Look for prolonged QT
1. Causes
a. Electrolyte abnormalities (hypokalemia, hypomagnesemia,
hypocalcemia)
b. Medications
i. Antipsychotics
1. Haloperidol
ii. Antiarrhythmics
iii. Some antibiotics
c. Hypothermia
d. MI
e. Congenital long QT syndrome

5. 5 Step Approach to EKG Interpretation
a. Regularity
i. Measure R-R
1. Constant?
a. Should be at regular intervals
b. HR
i. Regular or irregular?
c. P Wave
i. Present or absent?
1. Should be smooth, tounded, upward deflection
2. Should precede QRS complex
a. 1:1 ratio
d. PR Interval
i. Constant or variable
ii. Duration
1. 0.12-0.20
e. QRS Complex
i. Duration

1. 0.06-0.10
6. ECG Paper
a. 6 second strip
1. 3 small tick lines
2. 1 small box=0.04 seconds
3. 1 big box=0.20 seconds
a. 39 large squares is 6 seconds
ii. Methods
1. 6 Second Method (if there are 3 ticks and its a 6 second strip )
a.