1. Objective 12 Electrocardiograms
Electrocardiogram: a graphical recording of the potential changes that occur in the heart during a cardiac cycle
Electrocardiograph: a device used to measure these changes
Lead: a combination of electrodes that are used to detect electrical changes; there are standard leads (3 bipolar, 9 unipolar)
William Einthoven

3. Characteristic Waves and Intervals of a Typical ECG:
ECG Event Represented Duration (Sec)
P Wave – 0.10
atrial depolarization
P-R Interval time impulse is being transmitted through the atria and delay at AV node

4. Name Event Represented Duration (Sec)
ventricular depolarization 0.06 – 0.10
QRS Complex
ST Segment time between the end of ventricular depolarization and ventricular repolarization
T Wave ventricular repolarization

5. Objective 13 Common Arrhythmias
Analysis of ECG tracings include an evaluation of these characteristics:
1. Overall rate and rate of individual wave formations
2. Rhythm
3. Shape, height, and duration of wave formations
4. Deviation from the baseline

6. Common deviations include:
Sinus bradycardia: impulses arise at the SA node at a slow rate < 60 bpm
Note: in well conditioned athletes this may not be an abnormality

7. Sinus. impulses arise at the SA node at an
Sinus impulses arise at the SA node at an accelerated rate > 100 bpm
Tachycardia
Causes may include:
Exercise
Excessive sympathetic stimulation
Ischemia
Increased temperature

8. When ectopic foci suppress SA node inherent rate:
a single ectopic pacemaker produces an atrial rate of per minute
Atrial Flutter

9. Reentry causes many arrhythmias
Usually an ectopic pacemaker or a reentry

10. several ectopic foci cause an atrial rate of
several ectopic foci cause an atrial rate of per minute; some reach ventricle notice the presence of QRS complexes
Atrial Fibrillation

11. several ectopic foci generate potentials
several ectopic foci generate potentials independently; there is no effective contraction of the ventricular myocardium, and therefore, no pulse
Ventricular Fibrillation

12. Atrioventricular block
First degree AV block: all impulses are conducted from the atria into the ventricles, but with a greater than normal delay; P-R interval > 0.20 seconds
Second degree: some, but not all impulses are conducted from the atria into the ventricles; further defined as 2:1, 3:1, 4:1, etc; there is a consistent P-R interval
Third degree: called complete AV block; no impulses are conducted from the atria into the ventricles; the P-R interval varies because the atria and the ventricles are contracting independently

13. Bundle Branch Block:. conduction by one of the bundle branches is
Bundle Branch Block: conduction by one of the bundle branches is impaired; ECG shows a widening of the QRS complex
RBBB
LBBB