Cardio Physiology- ECG Flashcards
Briefly describe for the components of an ECG strip.
P Wave- Atrial depolarization, lasts for 0.1 seconds. Voltage - 0.1-0.3 mv
PR Segment- The segment between the end of the P wave to the beginning of the QRS complex.
ORS Complex- Ventricular depolarization. Last 0.04- 0.12 s. Voltage - 1.0-1.5 mv
ST Segment- The segment between the end of the S wave (QRS Com.) to the beginning of the T wave.
T wave - Ventricular repolarization. Have a voltage of 0.2-0.3 mv
U wave- follows the T wave and has a similar shape of a P wave but the similar depolarization of a T wave.
PR Interval - The interval from the beginning of the P wave to the beginning of the QRS Complex. Duration - 0.12-0.20s
QT Interval- the beginning of the QRS complex to the end of the T wave. If U wave is present then it will end at the end of the U wave.
In an ECG, one distance across one small square is equal to _________
0.04 seconds.
What is Einthoven’s Triangle?
This is the equilateral triangle that is formed by the 3 bipolar limb leads.
What is Einthoven’s Law?
Lead I + Lead III= Lead II
List the leads of an Echocardiogram.
Lead I,II, III
AVR, AVF, AVL and
V1- V6
If normal heartbeat rhythm is 60-100 bpm, what is anything <60 bpm and anything >100bpm
<60 bpm: bradycardia
>100 bpm: Tachycardia
What are two different rates that can be determined from an ECG?
Atrial rate (Frequency of the P wave) and Ventricular rate (frequency of the ORS complex)
What are three ways to calculate ventricular rate on a 10s ECG Strip?
Ventricular rate can be calculated by:
Small box method- 1500 (25mmx60s)/ # of small boxes
Large box method - 300/ # large boxes
R wave method - # of R waves (in a ORS) x 6 (If a 10s strip) or x by 10 (if a 6s strip)
What are the causes of left electrical axis deviation?
- Changes in heart position, left shift occurs from lying down, increased visceral adiposity, and the end of a deep expiration.
- Hypertrophy of left ventricle due to hypertension, aortic regurgitation and aortic stenosis
- Left bundle branch block (LBBB)
What are the causes of right electrical axis deviation?
- Changes in right position, right shift occurs. After a deep inspiration, standing up and in tall lanky people
- Hypertrophy of right ventricle caused by pulmonary hypertension, congenital conditions such as pulmonary valve stenosis, etc.
- Right bundle branch block (RBBB)
What causes increased voltage in the standard bipolar leads?
Increased ventricular muscle mass.
What causes decreased voltage in the standard bipolar leads?
Cardiac muscle abnormalities such as old myocardial infarction
Fluid in the pericardium
Anterior- posterior rotation of the apex of the heart
Briefly describe the 1st degree AV Block.
The 1st degree AV block is when the PR interval is prolonged and the PR interval is > 20s
(Normal range is 0.12-0.20s)
Briefly describe the 2nd degree AV Block.
The 2nd degree AV block consist of two types:
Morbitz type I (Wenecback )- this is where the PR interval is increasing and then a dropped beat
Morbitz II - this is where the PR interval is fixed and long and then a dropped beat.
The PR interval is >20s.
Briefly describe the 3rd degree AV Block.
In a 3rd degree AV block, you have constant P-P and Q-Q intervals. The AV Node or AV bundle is totally blocked causing no proper flow to the heart.
