Cardio 4 Flashcards
Electrocardiograph
instrument that measures electrical potentials on the body surface and generates a record of the electrical currents of the heart
Electrocardiogram
the graph of changing voltage/electrical actvity over time (y vs. x)
Uses for ECG
Detects:
arrythmias
plasma electrolyte concentrations
influence of certain drugs
anatomical orientation of the heart (A)
size of chambers (A)
injury to heart muscle (A)
When was the first ECG?
1887
Einthoven Standards
Y axis: 1 cm = 1mV
X axis: 25mm/sec
How many seconds is each box on an ECG when un with Einthoven standards?
40 milliseconds
Dipole Theory
individual dipoles at specific points in time and summing them all up as a vector (with direction and magnitude)
VECTOR
How many leads does the Einthoven standard ECG use?
12
What wave of an ECG is used to quickly identify a human having a heart attack? Do we have the same concern in animals?
T wave
Not as oncerned in animals because it does weird things for no reason (really)
What phase of electrical activity is not picked up on an ECG?
Atrial repolarization (Ta wave)
it is very broad with a very low amplitude
Which lead do we primarily look at in an ECG?
Lead II (2)
What does ‘a’ mean in an ECG lead?
augmented (multiplier factor)
Who developed the standard ECG?
Einthoven
P wave
atrial depolarization, SA node to AV node
What can the QRS interval be an indicator of?
size of the heart
When do you use little letters in an ECG?
denotes magnitude of the peak/trough
QRS complex
ventricular depolarization (R)
(Q is early, S is late)
T wave
ventricular repolarization
ST segment
typically isoelectric
Which wave of the ECG frquentl changes in domestic animals but can be problematic in humans?
T wave
When is the PR interval prolonged?
atrial enlargement or AV conduction problem
How do we correct the QT interval to be heart rate independent?
one of the gazillion different formulas
What was the first QT interval formula developed?
Bazett’s
Isoelectric in Dipole Theory
vector perpendicular to electrodes
Maximum Deflection in Dipole Theory
vector parallel to the electrode
How many ECG leads do they use in humans?
12 (6 in frontal plane, 6 in transverse plane)
Meaning of ST segment elevation in animals?
big ventricle
Category A animals
Purkinje fibers on endocardial surface
Category B animals
Purkinje fibers ramify throughout entire myocardium
Why are category B animal ECGs different?
can’t really look at chamber enlargement, needs different lead system
Base-apex Lead System
used in category B animals
- = right jugular vein
+ = left thorax over apex beat
What looks different on a base-apex ECG?
The QRS interval is inverted
best position to take an ECG
right lateral recumbency with 90 degree forelimbs
ECG filters
put on the ECG at a certain range (0.5 - 150 Hz) to avoid artifacts
What is a lead II ECG quality score of 3?
the highest score which is real bad (0 is the best score, no noise)
How long should the shortest ECG be?
10 seconds
What 3-4 things should you examine in an ECG?
- Heart rate (atrial and ventricular)
- Heart rhythm
- P-QRS-T complexes and intervals
- Mean electrical axis (Category A)
1 = PR interval
2 = PR segment
3 = QRS interval
4 = ST segment
5 = QT interval
Mean Electrical Axis (MEA)
Largest net QRS amplitude = MEA is parallel with this lead
Isoelectric (smallest net QRS voltage) = MEA is perpendicular to this lead
