EKG Flashcards
What types of pathology can we identify and study from ECGs?
Arrhythmias
MI and infarction
Pericarditis
Chamber hypertrophy
Electrolyte disturbances
Drug toxicity
What are the 12 leads?
3 limb leads (I, II, III)
3 Augmented leads (aVR, aVL, aVF)
6 Precordial leads (V1-V6)
Einthoven’s Triangle
An imaginary equilateral triangle having the heart at its center and formed by lines that represent the three standard limb leads of the electrocardiogram.
Lead I
Consists of positive electrode on the left arm looking toward the negative electrode on the right arm for electrical energy
Produces upward deflection of the QRS
Lead II
Consists of positive electrode on the left foot, negative electrode on the right arm.
Shows most upright QRS complexes and most prominent P wave
Lead III
Consists of positive electrode on the left foot, negative electrode on the left arm.
Produces upward QRS deflection
Lead aVR
Consists of positive electrode on the right arm- only limb lead on the right side of the body
Is the only lead with downward deflected QRS (normal EKG)
Lead aVL
Consists of positive electrode on the left arm, looks to the right and down.
Produces the least upright QRS among the limb leads.
Lead aVF
Consists of positive electrode on the left leg and looks straight up to the center of the chest.
Has very upright QRS complexes with prominent P waves.
Known as inferior lead (along with Leads II and III) because all look upward
Lead V1 location
Located at the right sternal border, forth intercostal space.
Lies above the right ventricle and septum
Lead V2 Location
Located at the left sternal border, fourth intercostal space.
Lead V3 Location
Located midway between leads V2 and V4
Lead V4 Location
Located at the midclavicular line, fifth intercostal space
Lead V5 Location
Located at the anterior axillary line, fifth intercostal space
Lead V6
Located at the midaxillary line, fifth intercostal space, above lateral wall of the left ventricle.
The QRS Axis
Represents the net overall direction of the heart’s electrical activity.
Leads I and aVF to determine axis. Normal = -30 degrees to 90 degrees.
Left axis deviation -30- -90 degrees
Right axis deviation 90- 180 degrees
Abnormality can mean ventricular enlargement or conduction blocks.
Bundle Branch blocks
Most common ECG abnormality
Appears as a wider than normal QRS complex
Occurs when one of the two bundle branches can’t conduct the impulse
Most common cause: ischemic heart disease
Right Bundle Branch Block
Impulse conduction to the right ventricle is blocked.
Examine lead V1 to identify.
ECG shows delayed or positive R wave (rabbit ears)
Key Identifier: QRS complex wider than 0.12 seconds with positive R wave in V1.
Left Bundle Branch Block
Electrical impulses don’t reach the left side of the heart.
QRS wider than 0.12 seconds.
Key Identifier: wide downward S wave or rS wave in leads V1 and V2.
What is the widow maker?
Left anterior descending coronary artery.
V1 and V2
Reciprocal Changes
Changes seen in the wall of the heart opposite the location of the infarction. These are normally seen at the onset of MI and are short lived.
Posterior Myocardial Infarction
Suggested by the following changes in V1-V3
- Horizontal ST depression
- Tall, broad R waves (>30ms)
- Upright T waves
- Dominant R wave (R/S ratio >1) in V2
Location of Posterior EKG leads
V7- Left posterior axiallary line, in the same horizontal plan as V6.
V8- Tip of the left scapula, in the same horizontal plane as V6
V9- Left paraspinal region, in the same horizontal plan as V6.
8 Step Process for Rhythm Interpretation
- Rate
- Rhythm
- P wave
- PR Interval
- QRS complex
- Ratio of P:QRS
- T wave
- QT
- Identify
- Ectopic beats
- Check ST segments
- U wave presence