ECGs Flashcards
(27 cards)
purpose of ECGs
● Examine heart rate
● Examine heart rhythm
● Detect conduction delays
● Detect arrhythmias
● Detect coronary perfusion
➤ Hypertrophy, ischemia, infarction
Single lead component
Only one area of heart can be viewed at a time
Sensitive to rate and rhythm
Common for monitoring patients during ambulation or other activity
12 lead component
12 areas may be viewed
Assist with arrhythmia detection and perfusion impairments
Sensitive to rate, rhythm, and conduction
Does not provide continuous monitoring except during ETT
Normally identified MI
horizontal axis represents time
➤ 1 small box = 0.04 seconds
➤ 1 large box = 0.20 seconds (comprises 5 small boxes)
vertical axis represents mm
➤ 1 small box = 1 mm
➤ 1 large box = 5 mm
6 sec strip method
On a 6-second strip, count 30 large boxes
On this 6-second strip, count the number of QRS complexes and multiply by
10 → heart rate per minute
R wave calculation method
Identify a specific R wave that falls on a heavy black line
For each heavy black line that follows this R wave until the next R wave, count
300, 150, 100, 75, 60, 50 → heart rate per minute
⚬ However, this method cannot be used for irregular heart rhythms
30 sec strip method
Count the number of QRS complexes in a 30-second strip and multiply by
2 → heart rate per minute
QRS complex method
Count the number of large boxes (5 mm or 0.20 seconds) between the first QRS
complex and the next QRS complex
⚬ 300/(number of large boxes) → heart rate per minute
Another more accurate method: count the number of small boxes (1 mm or 0.04
seconds) between adjacent QRS complexes
⚬ 1500/(number of small boxes) → heart rate per minute
P wave
atrial depolarization contraction
PR interval
time required for atrial depolarization and for the impulse to travel from
the SA node to the AV node
QRS complex
ventricular depolarization (contraction) and atrial repolarization
(relaxation)
ST segment
a flat piece of isoelectric line
➤ J point: where the S wave turns into the ST segment
T wave
ventricular repolarization
QT interval
time for ventricular electrical systole (both ventricular depolarization
and repolarization)
Rate: P wave
➤ Does the P wave look normal and upright?
➤ Is there a P wave before every QRS complex?
➤ Are the atria contracting too fast or too much?
➤ Calculate HR by counting the number of QRS complexes in a 6-second strip and
multiplying by 10
rhythm: av block
➤ Atria did not communicate with ventricles (PR interval)
➤ Normal PR interval duration is 0.12 to 0.20 seconds
Axis ST
➤ ST segment: MI or ischemia
● Determine whether anything is even wrong
ectopic beats
➤ Beat that originates from site other than sinus node
➤ Results in irregular rhythm
➤ Common with stress, caffeine, and nicotine
common types of ectopic beats
Premature ventricular contractions (PVCs)
Ventricular tachycardia
Ventricular fibrillation
Premature atrial contractions (PACs)
⚬ Supraventricular arrhythmias
⚬ Ectopic beat that originates in atria
Atrial tachycardia
Atrial flutter
Atrial fibrillation
Ventricular arrhythmias:
ectopic focus in ventricles
premature ventricular contraction
➤ Ventricles contract before atria → cannot be filled optimally
➤ Premature beat arising from somewhere in one of the ventricles
➤ ECG: no P waves, wide QRS complex followed by a long pause
➤ Occurs in normal population
Ventricular bigeminy:
every other beat is a PVC
1 normal, 1 PVC, 1 normal, 1 PVC
Ventricular trigeminy:
every 3rd beat is a PVC
2 normal, 1 PVC, 2 normal, 1 PVC
