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A systematic search of the medical literature was performed on January 9, 2008. The search, limited to human subjects and English language journals, included the National Guideline Clearinghouse, the Cochrane database, PubMed, UpToDate®, and PIER. The current American College of Cardiology (ACC)/American Heart Association (AHA)/European Society of Cardiology 2006 Guidelines for Management of Patients with Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death, and the Management of Patients with Supraventricular Arrhythmias can be found at


Cardiac arrhythmia is an abnormality of impulse generation, impulse propagation, or a combination of both. Although arrhythmias can occur in all age groups, significant rhythm disturbances are relatively uncommon in young, healthy individuals. The primary purposes of the history in evaluating a cardiac arrhythmia are to determine the underlying etiology, anatomic abnormalities, physiologic disturbances, cardiac status, and prognosis.

Physical Findings

The symptoms associated with cardiac arrhythmias vary widely. They may be very minor such as an awareness of the heartbeat (palpitations). More serious symptoms usually reflect a decrease in cardiac output resulting from reduced ventricular filling during the tachycardia. Patients may describe a rapid, sustained heartbeat that may be regular or irregular, or may describe intermittent accelerations or decelerations of the heartbeat. Some patients are able to detect even slight variations in the heart rate or rhythm while others may have no awareness of any arrhythmia—even ventricular tachycardia (VT). Patients will commonly seek medical attention because of palpitations, presyncope, syncope, or symptoms of angina or heart failure.

Wide-Complex Rhythm

Wide QRS complexes result from impulses that have at least some conduction outside the normal conduction system. By definition, wide-complex tachycardias have a rate greater than 100 beats per minute and have a QRS duration greater than or equal to 120 ms. VT is one form of a wide-QRS-complex tachycardia, but a wide QRS complex may also occur in supraventricular tachycardia (SVT) when there is a conduction delay in the His–Purkinje system or there is conduction over a parallel route from the atria to the ventricle, that is, an accessory pathway. In general, the wider the QRS complex, the more likely the rhythm is to be ventricular in origin, especially when the complexes are greater than 160 ms in duration.1 The patient’s age and risk factors play a significant role in general as to the potential etiology of a wide complex rhythm. Other evidences to support the diagnosis of VT include the independent P-wave activity, fusion beats, AV dissociation, and concordance throughout the precordial leads. The absence of an RS complex in all precordial leads, or an RS interval of more than 100 ms, is indicative of VT.2 If the origin of the wide-complex tachycardia cannot be determined, the safest option is to treat it as VT.

Narrow-Complex Rhythm

Narrow-complex tachyarrhythmias almost always ...

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