Life-threatening arrhythmias in the intensive care unit.

Symptomatic arrhythmias are frequently observed in the intensive care unit and often lead to significant hemodynamic compromise because of the presence of multisystem disease. In particular, prompt evaluation of patients with tachycardia is critical because treatment depends on the accurate diagnosis of the arrhythmia mechanism. The electrocardiogram remains the most important diagnostic tool for the evaluation of both wide complex and narrow complex tachycardia. For wide complex tachycardia, evaluation of the atrioventricular relationship and QRS morphology are critical, and for narrow QRS complex tachycardias, evaluation focuses on identification of the location and morphology of P waves. Bradycardia can arise from sinus node dysfunction or atrioventricular conduction block.