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S.M. is a 42-year-old woman with a history of paroxysmal atrial fibrillation and mitral valve prolapse since childhood. The patient is under the care of a cardiologist for these conditions. She has a body mass index of 25 kg/m2 and no other documented comorbidities. Her job requires her to examine carbon fiber aerospace components at the end of the manufacturing process. The required physical motions include stacking objects weighing 8-15 lb and bending over repetitively during an 8-hour shift. Three weeks ago, S.M. felt a sudden and extreme pain in the right lumbar area while bending over to retrieve a component that had fallen on the floor. She was transported to the emergency department and discharged with a prescription for meloxicam, a nonsteroidal anti-inflammatory drug. The patient was seen by the corporate physician 2 days later and referred to an outpatient physical therapy clinic for pain relief and a return-to-work program. At the first appointment, the therapist noted that S.M. needed assistance getting out of the vehicle passenger seat. Beyond activities of daily living and clinic visits, S.M. states that she has done almost no physical activity. She has remained in bed or on the couch. Her current medications include diltiazem and naproxen, an over-the-counter nonsteroidal anti-inflammatory drug that she started taking after she completed her prescription of meloxicam. The first three sessions of therapy were aimed at minimizing pain and improving functional mobility. Today, S.M. arrives to begin the functional return-to-work program. At rest, her heart rate is 78 bpm, regular rhythm and her blood pressure is 132/89 mm Hg. Fifteen minutes into the return-to-work exercises, the patient complains of chest palpitations that she recognizes as an arrhythmia. Determination of vital signs indicates her heart rate is 120 bpm, irregular rhythm and blood pressure is 159/98 mm Hg. After several minutes, her palpitations recede and heart rate becomes regular though still tachycardic at 102 bpm.


Cardiac arrhythmias, or abnormal heart rhythms, can be brief or long lasting. They can be completely benign or life threatening. Arrhythmias often occur in the presence of preexisting heart disease. Arrhythmias occur in over 80% of individuals with an acute myocardial infarction and are the most common cause of death in those who have had a myocardial infarction. Electrolyte imbalances can also cause arrhythmias. Diuretics are significant sources of such imbalances. Treatment is required when cardiac rhythms are too rapid, too slow, asynchronous, or significantly reduce cardiac output. Certain arrhythmias may precipitate more serious or even lethal rhythm disturbances. For example, multiple premature ventricular contractions can precipitate ventricular fibrillation, which is fatal unless corrected promptly. In such cases, antiarrhythmic drugs may be lifesaving. In contrast, pharmacologic treatment of arrhythmias that are asymptomatic or minimally symptomatic is avoided because of the ability of many of these drugs to induce lethal arrhythmias. In this chapter, we review the conduction sequence and electrophysiology of ...

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