| 1) Sinus
Tachycardia |
| Sinus tachycardia
occurs when impulses originate at the SA node at a rate
greater than 100 beats per minute in adults. It may or
may not be clinically significant, and is not in itself
indicative of cardiac disease. (For example, sinus tachycardia
may be associated with fever or exercise.) |
 | |
| 2) Sinus
Bradycardia |
| Sinus bradycardia
occurs when impulses originate at the SA node at a rate of
less than 60 beats per minute. Sinus bradycardia is not
necessarily indicative of cardiac disease, and is often seen
in athletes and during sleep. |
 | |
| 3) Atrioventricular (AV)
block |
| Partial AV
block occurs when AV node damage prevents some atrial
impulses from being transmitted to the ventricles. In
the particular case illustrated, every second P wave is not
followed by QRS and T waves, producing 2:1 AV block. It
is said that there are "dropped beats" of the
ventricles. |
|
|
Complete AV
block: When the condition that is causing poor
conduction in the AV node becomes severe, there is a complete
block of the impulses from the atria to the ventricles.
There is no synchronization between atrial and ventricular
electrical activity. The ventricles have "escaped" from
atrial control, and are beating at their own natural
rate. |
 | |
| 4) Premature
Contractions |
| A premature
contraction occurs when the heart contracts prior to the time
when normal contraction is expected. Most premature
contractions are due to ectopic foci in the heart, which emit
abnormal impulses at abnormal times during the cardiac
rhythm. |
 | |
| 5) Ventricular
Fibrillation |
| In ventricular
fibrillation, multiple impulses are traveling in all
directions through the ventricles. If left untreated,
ventricular fibrillation results in death within about 2-4
minutes. Although electric shock can initiate
ventricular fibrillation, a very strong electrical current
passed through the ventricles for a short period of time can
actually stop fibrillation. By stimulating all parts of
the ventricles simultaneously and putting them in the same
state of refractoriness, the S-A node or some other part of
the heart becomes the pacemaker when the heart starts to beat
again. |
 | |
Cardiovascular
