Module 8 ECGs Flashcards
Conductivity
The ability of cells to transmit electrical current
Contractility
The ability of muscle fibres to respond to electrical stimulus by shortening and contracting
Conductivity
The ability of the cells to transmit electrical current
Contractility
The ability of muscle fibers to respond to electrical stimulus by shortening and contracting
Conduction System of the heart
Sa Node
AV node
Bundle of His
Purkinje Fibres
Pacemaker Potential
A self-initiating action potential that occurs in the condition system of the heart and triggers action potentials (and thus contraction)in the cardiac cells.
why would a QRS complex be inverted?
Ischemia
Ventricular hypertrophy
Basically, whenever blood flow is restricted (lack of O2)
What are the 5 rules for analyzing ECG’s/heart rhythms?
Regularity
Rate
P wave
PR Interval
QRS
How PR intervals are measured?
when they measure between 0.12 and 0.20 seconds.
Expected QRS range?
Less than 0.12 seconds.
indicates time between atrial and ventricle contraction
Innervations of the heart by the autonomic system: what does the sympathetic branch effect?
- The atria and ventricles
- It increases:
-HR
-Conduction
-Irritability
Innervations of the heart by the autonomic system: what does the parasympathetic branch effect?
- only the atria
- decreases:
-HR
-Conduction
-Irritability
Elements of Sinus Arrhythmia
-SA Node is the pacemaker, impulses are irregular.
-RR increases with inspiration/expiration
-Each beat is conducted normally
Characteristics of: Accelerated Junctional Rhythm
-Short waves but regular rhythm
-The AV node takes over.
Inherent Rates for: SA Node
60 - 100 BPM
Inherent Rates for: AV Node
40 - 60 BPM
Inherent Rates for: Ventricles
20 - 40 BPM
How do you calculate a regular rhythm from a ECG?
Count the number of large squares between the R waves and divide into 300.
OR
Count small squares and divide into 1500 (more accurate)
ECG Recordings: How much is one small square in terms of time?
0.04 s
ECG Recordings: 5 large squares is equal to how many seconds?
1 second
ECG Recordings: How many seconds are in 5 small squares?
0.20 seconds
ECG Interpretation: what does the ST segment represent? (Lead II)
Depression = possible ischemia
Elevation = acute myocardial injury (MI)
What do inverted T Waves (lead II) suggest?
Ischemia
ECG Interpretation: What are QT intervals?
Vulnerable refractory period of ventricles