Electrocardiography Flashcards
Hypertrophic Obstructive Cardiomyopathy - what decreases and increases the sound of the murmur
It is counterintuitive as an increase in venous return lowers the sound of the murmur (from squatting to standing up) and a decrease in venous return increases the sound of the murmur in HOCD
What does EKG look at
Records the depolarization of cardiomyocytes from 12 different angles
Why dont we see repolarization of the atria on EKG
It is obscurred by the ventricular depolarization QRS complex
What represent the RT complex on EKG
Phase 2 of the ventricular contraction which basically consist of no change in the action potential
What are the 2 planes an EKG measures voltage to
Vertical and horizonatal plane, the 6 leads he showed us meaures in the horizontal plane
What are the limb leads
No sensor on the right leg
Summary of the EKG
How do you define the beginning of QRS segment in abnormal EKG
The first negative to resting potential is defined as the Q point
What is J point
Right after S point
How does ST change in ischemia and infarction
Ischemia cause ST segment depression, infarction causes ST segment elevation
What are the first few things you look at in an EKG
- Rate: 300/ R-R interval (big boxes)
- Rythm: sinus is normal, anything other than that can be afib or some kind of heart block
- Axis: he said look at 1,2 and 3 electrodes in the frontal plane - the slide said right or left axis deviation
- Interval: we look at PR interval, QRS interval and QT interval (200, 120, 450 milliseconds)
- Hypertrophy: left ventricle hypertrophy, the QRS voltage would be higher. He also mentioned the cornel criteria
- Ischemia/Infarction: Previous and acute infarctions
How do you look at the axis
He said here that we look at I and aVF. For these 2 the QRS have to be positive in I and also in aVF. This is called the 2 thumbs up sign.
When he said positive he meant the total area under the curve in the QRS complex has to be positive.
Clinically this means that most of the myocardial mass depolarizes in lead I and in aVF. Anything between aVF and I is normal. Clinically anything between aVF and aVL is normal. This is referred as being in “the normal quadrant”
Sum of the vector has to be between I and aVF
How do you measure hypertrophy on EKG
You measure the height on your QRS complex
What are the characteristics of afib
- Tachycardia
- Not in rythym, R to R dont have equal spacing
- Atrial depolarization waves are not recorded since it is in afib, fibrillation waves are not usually strong
What is the total time that EKG runs for
6 seconds
How do you find the heart rate in afib
Count all of the R waves and multiply it by 6 (know why)
What kind of deviation is in afib
Right axis deviation
What are the main causes of afib
Long term hypertension as the atria are stretched and are more prone to go into afib
Describe the right axis and left axis deviation
Right axis deviation - Lead I is negative, aVF is positive
Left axis deviation is the opposite - aVF is negative and I is positive
What happens in I negative and AVF negative
Extreme right axis deviation, happens in patient with situs inverses
What congential heart disease show right axis deviation
Tetralogy of Fallot and Eisenmenger complex
How do you check for hypertrophy on EKG
This is the Cornell criteria
- Look at the R wave on aVL
- Look at the S wave on V3
For males normal goes up to 28 boxes and for female it goes up to 20 boxes on EKG (in vertical axis).
You check the height of the QRS complex on
When you have left ventricular hypertrophy you have more myocardial mass which causes higher potential
What is this person having
Notice that there is ST elevation in II, III and aVF. This means that this person is having infarction. Since II, III and aVF runs through the right ventricle according to the axis, this person is having right ventricle infarction, so this person may have a thrombus in the right coronary artery.
Also notice that there is sometimes P wave in the bottom strip but no QRS wave which means there is an AV nodal block which causes PR interval change
Types of different blocks
Need to know how to pick them up on an EKG
1st degree AB block: PR interval that is longer than normal, longer than 0.2 seconds
2nd degree AV block, Mobitz I: prolonging PR interval, PR interval gets longer every time
2nd degree, Mobitz II: normal stable PR interval which then just drops, it does not prolong you just get a drop in the PR segment
3rd degree: total heart block, makes no rythym
