12 Lead ECG Flashcards
Basics: what do the following waves represent?
- P wave
- PR
- QRS
- T wave
- QT interval
- P wave is Atrial DEPOLARIZATION
- PR interval: AV conduction time (0.12-0.20 sec)
- QRS: Ventricular DEPOLARIZATION (0.06 - 0.10 sec)
- T wave: Ventricular REPOLARIZATION
- QT Interval: time of ventricular depolarization and repolarization (0.36 - 0.44 sec)
QT interval is corrected bc of the effect of heart rate.
QTc = 0.40 - 0.44 sec
When are Q waves considered pathologic?
- Width > 30 ms (0.04 sec)
- Depth ≥ 25% of the height of the R wave (R÷4)
- If present in contiguous leads, indicative of myocardial necrosis. Contiguous: next or together in sequence.
Ex: V3 and V4 or V1 and V2
What does one tiny box on the paper represent?
1 mm or
0.04 sec horizontally
0.1 mV vertically
Which lead placement is:
aVR?
aVL
aVF
What is the R LL’s purpose?
aVR is the right shoulder; stands for augmented Vector Right. It’s a positive electrode.
aVL is on the left shoulder; stands for augmented Vector Left. It’s a positive electrode.
aVF is the left lower limb lead; means augmented Vector Foot. It’s also a positive electrode.
Right LL serves as the ground; a neutral lead, like you would find in an electric plug. It is there to complete an electrical circuit and plays no role in the ECG itself.
Which lead is assessed to determine left vs right bundle branch block?
What is the rhyme r/t this?
V1
“If the QRS is wide, and the QRS is upRIGHT, it’s a RIGHT bundle branch block (BBB). If the QRS is wide and it goes LOW-er, it’s a LEFT BBB.”
- An infarct in the RCA would be seen in which leads?
- What are the reciprocal leads?
- Complications from this infarct?
- RCA = Inferior MI
Leads: II, III, aVF - Reciprocal: I, aVL
- AV Blocks, decreased HR (node conduction in R atria), decreased BP, Papillary muscle rupture, N/V
Right sided ECG asses V2R - V4R for possible RV MI
- An infarct in the LAD would be seen in which leads?
- Reciprocal leads?
- Complications from this infarct?
- LAD = Anterior MI
Septal leads V1 and V2
Anterior leads V3 and V4 (LAD/Left main) - Reciprocal: II, III, aVF
- 2ndº Type II, BBB, 3rdº block, HF, Cardiogenic shock, VT
- An infarct in the Left Circumflex would be seen in which leads?
- Reciprocal leads?
- Complications from this infarct?
- Left Circumflex = Lateral MI
Leads: I, aVL, V5, V6 - Reciprocal: II, III, aVF
- Ventricular aneurysm, AV blocks, PVCs, VT
- An infarct in the RCA or Circumflex (Posterior MI) would be seen in which leads?
- Reciprocal leads?
- Complications from this infarct?
- Septal leads V1, V2
- ST depression and/or Pathologic R waves
- AV Blocks, Bradycardia
- A Right Ventricular MI, supplied by the RCA, would be seen in which leads?
- Reciprocal leads?
- Complications from this infarct?
- V2R, V3R, V4R (ECG done on the RIGHT side of chest)
If you see elevation, that’s confirmation. - Reciprocal: none
- Complications: RV Failure, AV Blocks, N/V
Hypotension = fluids (Caution NTG & morphine use)
Mnemonic Poem for First degree block:
“If the R is far from P, then you have a First Degree.”
Mnemonic poem for Wenckebach:
“Longer, longer, longer, drop, then you have a Wenckebach.”
Wenckebach is a 2ndº Type I block.
This poem is referring to the P to QRS relationship, P’s are further from the QRS and then a QRS is “dropped” all together.
Mnemonic poem for Mobitz II:
“If some P’s don’t get through, then you have a Mobitz II.”
OR
“If some R’s don’t get through, prepare to pace that Mobitz II!”
Mobitz II is a 2ndº Type II block.
This poem is referring to the relationship between the P’s and QRS complexes. The P’s are in consistent intervals with the QRS’s and then a QRS is blocked, or dropped.
Second-degree AV block (Type 2) is almost always a disease of the distal conduction system located in the ventricular portion of the myocardium.
Prepare to pace. This can progress to 3rd degree.
Mnemonic poem for 3rdº Heart Block:
“If P’s and Q’s don’t agree, then you have a THIRD DEGREE.”
OR
“If R’s and P’s don’t agree, prepare to PACE that 3rd degree!”
Third-degree AV block is electrocardiographically characterized by:
1. Regular P-P interval.
2. Regular R-R interval.
3. Lack of an apparent relationship between the P waves and QRS complexes.
4. More P waves are present than QRS complexes.
Third-degree heart block: The electrical signal from the atria to the ventricles is completely blocked. To make up for this, the ventricle usually starts to beat on its own acting as a substitute pacemaker but the heartbeat is slower and often irregular and not reliable.
A third degree heart block can cause a wide range of symptoms, some of which are life-threatening. This type of heart block is usually regarded as a medical emergency and may require immediate treatment with a pacemaker.
These will have bradycardic ventricle rates and atropine will NOT work. Atropine works on the SA node… and there is no communication between the atria and ventricles - so it won’t have an affect.
How do you pick up a posterior wall MI?
By seeing a reciprocal change in V1 and V2.
You will see ST depression (the reciprocal of elevation - we’d see elevation if we were able to place leads on the back). You may also see pathological R waves.
