ECG basics Flashcards
If the PR (atrial) rate was 80 per min and the QRS (ventricular) rate was 45 per min what block would you suspect?
3rd-degree block
Where do you measure the PR interval from and to?
The beginning of the P wave to the beginning of the QRS complex
What is the most likely rhythm?
1st-degree heart block
Rate: ~80bpm (300/3.6)
Rhythm: regular
QRS: Narrow (<3 small squares)
P-waves: Constantly prolonged (> 5 small squares)
How would you calculate the rate on a rhythm strip?
300 divided by the number of large square between consecutive R waves
or
1500 divided by the number of small squares between consecutive R waves
or
Number of R waves across the bottom of a standard 12 lead ECG (10 seconds) multiplied by 6
What common arrhythmias have a broad QRS complex?
Ventricular in origin
Ventricular tachycardia (VT)
3rd degree hear block
Conduction
Left bundle branch block (LBBB)
Right bundle branch block (RBBB)
If the PR interval was…
5 small squares with every 4th beat dropped…
what type of block would you suspect?
2nd-degree block
Mobitz II
Whats the most likely rhythm?
Normal Sinus Rhythm (NSR)
Rate: ~90 (300/3.3)
Rhythm: regular
QRS: narrow (<3 small squares)
P waves: P-R interval normal and constant (3-5 small squares)
Describe 1st-degree heart block
Prolonged PR interval > 0.2 sec (5 small squares).
If the PR interval on you ECG was…
4 small square then 5 small squares then 6 small squares then 7 small squares then QRS missing…
what type of block would you suspect?
2nd-degree block
Mobitz I (Wenckebach)
Define a Q wave
The negative (downward) deflection PRECEDING an R wave
What are the criteria for right bundle branch block (RBBB)
Broad QRS
RSR pattern in V1 (2 R waves like an M shape)
Slurred S wave in V6
Describe 3rd-degree heart block
No relationship between the P waves and the QRS complexes
QRS rate usually <60 QRS
Width frequently broad (> 3 small squares)
Describe 2nd-degree heart block
Mobitz I (Wenckebach)
Ever increasing PR interval until a QRS complex is missed completely and the cycle begins again.
Which are the anterior leads?
V1, V2, V3
(some texts consider V1-2 septal and V3-4 anterior)
If the PR interval on an ECG was 7 small squares what type of block would you suspect?
1st-degree block
Whats the most likely rhythm?
Ventricular Tachycardia (VT/V-Tach)
Rate: ~250 (1500/6)
Rhythm: regular
QRS: Broad (>3 small squares)
P-waves: no
Define an R wave
The positive (upward) deflection of the QRS complex
Describe 2nd-degree heart block
Mobitz II
A regular PR interval until a QRS complex is missed
Often happens at regular intervals such as every 4th QRS missed
Which are the inferior leads?
II, III, aVF
Which are the lateral leads?
V4, V5, V6, aVL, I
(some texts consider V3-4 to be anterior and V5-6)
What is the normal QRS width?
Less than 0.12 sec (3 small squares)
Describe atrial fibrillation (AF)
Irregularly-irregular QRS rate
No clear P waves visible
What is the most likely rhythm?
Atrial flutter
Rate: ~150bpm
Rhythm: regular
QRS: Narrow
P-waves: saw-tooth appearance
What is the most likely rhythm?
2nd-degree heart block (Mobitz I)
Rate: ~35 - 66 (300/8 to 300/4.5)
Rhythm: Regularly irregular
QRS: Narrow
P-waves: Ever increasing P-R interval until QRS complex dropped
What is the voltage criteria for ST elevation?
>1mm above the isoelectric line with the exception of V1 and V2 where >2mm is appropriate
What is the normal PR interval?
0.12 - 0.2 seconds (3 - 5 small squares)
If lead I is predominantly POSITIVE and lead II is predominantly NEGATIVE what is the cardiac axis likely to be?
Left axis deviation
What is the most likely rhythm?
Atrial Fibrillation (AF/A-Fib)
Rate: ~150-300
Rhythm: Irregularly-irregular
QRS: Narrow (<3 small squares)
P-waves: not clearly visible
If lead I is predominantly NEGATIVE and lead II is predominantly POSITIVE what is the cardiac axis likely to be?
Right axis deviation
Define an S wave
The negative (downward) deflection FOLLOWING an R wave
If lead I is predominantly POSITIVE and lead II is predominantly POSITIVE what is the cardiac axis likely to be?
Normal
What is the most likely rhythm?
Supra-Ventricular Tachycardia
Rate: ~250 (1500/6)
Rhythm: regular
QRS: Narrow (< 3 small squares)
P-waves: ?
Whats the most likely rhythm?
2nd-degree heart block
Rate:
Rhythm: Regular (mostly)
QRS: Narrow (<3 small squares)
P-waves: regular but every 4th beat dropped
What are the criteria for left bundle branch block (LBBB)
Broad QRS (>0.12sec)
Dominant S wave in V1
No q wave in V6, I or aVL (high lateral leads)
