An arrhythmia is a disruption in the normal events of the cardiac cycle. It may take a variety of forms.
             A heart rate of over 100 beats/minutes, originating in the SA node.
             May be caused by fever, apprehension, physical activity, anemia, hyperthyroidism, drugs (epinephrine, theophylline), myocardial ischemia, caffeine.
             P wave: precedes each QRS complex with normal contour
             C. Treatment: correction of underlying cause, elimination of stimulants; sedatives, propranolol (Inderal).
             A slowed heart rate initiated by SA node
             Caused by excessive vagal or decreased sympathetic tone, MI, intracranial tumors, meningitis, myxedema, cardiac fibrosis; a normal variation of the heart rate in well-trained athletes
             3. P wave: precedes each QRS with normal contour
             4. P-R interval: normal (0.08 second)
             c. Treatment: Usually not needed; if cardiac output is inadequate, atropine and isoproterenol are usually prescribed; if drugs are not effective, a pacemaker may need to be inserted.
             an arrhythmia in which ectopic foci cause rapid, irregular contractions of the heart
             commonly seen in clients with rheumatic mitral stenosis, thyrotoxicosis, cardiomyopathy, hypertensive heart disease, pericarditis, and coronary heart disease
             Ventricular: varies between 100-160 beats/minute
             Rhythm: atrial and ventricular regularly irregular
             P wave: no definite P wave; rapid undulations called fibrillatory (f)waves
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