8/4- Basics of ECG: Bridging Theory and Practice Flashcards
Which ECG limb lead has a negative QRS complex in normal subjects?
A. Lead I
B. Lead II
C. Lead aVF
D. Lead aVR
E. Lead aVL
Which ECG limb lead has a negative QRS complex in normal subjects?
A. Lead I
B. Lead II
C. Lead aVF
D. Lead aVR
E. Lead aVL
Which chest leads are most aligned with overall position of heart in chest cavity?
A. V1/V2
B. V3/V4
C. V5/V6
Which chest leads are most aligned with overall position of heart in chest cavity?
A. V1/V2
B. V3/V4
C. V5/V6
Which chest leads have consistently positive QRS complexes?
A. V1/V2 “septal leads”
B. V3/V4 “anterior leads”
C. V5/V6 “lateral heads”
Which chest leads have consistently positive QRS complexes?
A. V1/V2 “septal leads”*
B. V3/V4 “anterior leads”
C. V5/V6 “lateral heads”
Where is the sinus node located?
A. Right atrium near SVC
B. Right atrium near IVC
C. Left atrium near pulmonary veins
Where is the sinus node located?
A. Right atrium near SVC
B. Right atrium near IVC
C. Left atrium near pulmonary veins
What is a normal QRS axis?
A. -30 to +90 degrees in the frontal plane
B. 0 to + 90 degrees in the frontal plane
C. -30 to -90 degrees in the frontal plane
What is a normal QRS axis?
A. -30 to +90 degrees in the frontal plane
B. 0 to + 90 degrees in the frontal plane
C. -30 to -90 degrees in the frontal plane
Describe (broadly) the normal QRS axis?
Downward and to the left (-30 to +90)
- QRS is positive in Leads I and aVF
What planes are used in placing ECG leads? Number/type of leads?
Frontal plane:
- 3 standard limb leads: bipolar leads I, II, III
- 3 augmented limb leads: aVF, aVR, aVL
Horizontal plane:
- 6 precordial chest leads
What is Einthoven’s triangle?
3 electrodes: RA, LA, LL
- generate 3 bipolar limb leads I, II, and III
Lead 1: bipolar vector from R arm to L arm
Lead 2: R arm to L leg
Lead 3: L arm to L leg
What is the setup for the augmented limb leads?
Augmented limb leads: aVR, aVL, and aVF use combination of electrodes as ground (vector looks like it’s coming from the other two)
aVR: ground L arm, L leg
aVL: ground R arm, L leg
aVF: ground R arm, L arm
How far apart are the vectors for the 3 bipolar leads?
60 degrees (0, 60, and 120)
How far apart are the vectors for the 3 augmented leads?
120 degrees (-150, -30, and 90)
Which vectors point downward?
Another name for them?
What do they reflect?
“Inferior leads”; inflect pathology in the inferior wall of the left ventricle
Leads: II, III, aVF
How do we group limb leads (broad groups)?
Inferior leads: II, III, aVF
Lateral leads: I and aVL
What do inferior leads reflect? Where do they point?
- Point inferiorly
- Reflect inferior LV wall pathology (e.g. ischemia or infarction)
What do superior leads reflect? Where do they point?
- Point laterally
- Reflect lateral LV wall pathology
Which lead(s) do(es) not have a positive QRS complex? Why?
aVR
- All standard ECG leads have a positive QRS except aVR
- The aVR vector points upward and to the right, while the heart is on the left side, pointing downward
Where are the precordial chest leads placed?
???
V1-
V2-
V3-
V4-
V5-
V6-
How do we group chest/precordial leads?
Chest leads V1-V6 derived from + chest electrodes placed over chest wall
V1, V2: septal (or anteroseptal) leads
V3, V4: anterior leads
V5, V6: lateral leads
QRS is negative in leads ___ and positive in ___
QRS is negative in leads V1/V2 and positive in V5/V6
As you move from V1 to V6, the leads are becoming more positive/upright (V1 pointing out to the right, while others fan across until V6 is pointing left and most aligned with the heart in the chest cavity)
T/F: V5 and V6 are better aligned with the chest orientation in the chest and are thus “positive”?
True
Draw/label normal EKG (P, QRS, T) wave?
Sequence of depolarization in the heart?
- Sinus node
- AV node
- His bundle
- Bundle branches
- Purkinje fibers
- Myocardium
Cardiac structures and the corresponding ECG waves:
- Sinus node:
- AV node:
- His bundle:
- Bundle branches:
- Purkinje fibers:
- Myocardium
Cardiac structures and the corresponding ECG waves:
- Sinus node: P wave
- AV node: PR interval
- His bundle: PR interval
- Bundle branches: QRS interval
- Purkinje fibers: QRS interval
- Myocardium: QRS interval
Localization of ECG abnormalities:
- Abnormal P wave
- Long PR interval
- Short PR interval
- Wide QRS interval
Localization of ECG abnormalities:
- Abnormal P wave: ectopic atrial rhythm
- Long PR interval: AV block
- Short PR interval: accessory tract
- Wide QRS interval: bundle branch block or dilated ventricles
What is the QRS axis? Direction?
The QRS axis is the overall direction of ventricular depolarization
- Ventricular depolarization proceeds from the right and left bundle branches and outward from ENDOcardium to EPIcardium
- It proceeds downward and to the left in the frontal plane
How can a normal heart vector be up to 0 to -30 if the heart points down and to the left?
Left ventricle may undergo concentric hypertrophy in response to high blood pressure, causing the heart axis to shift leftward
What is commonly seen in the EKG of individuals over the age of 50 or 60?
This leftward deviation/shift of the heart axis
The indeterminate axis/area is where?
- 90 to +/- 180
Deviation:
- Normal:
- Left:
- Right:
- Indeterminate:
Deviation:
- Normal: -30 to +90
- Left: -30 to -90
- Right: +90 to 180
- Indeterminate: -90 to 180
Axis shift is typically important as a marker of what?
Ventricular hypertrophy
(Left hypertrophy -> left deviation and vice versa)
