A 37-year-old woman presents to the emergency department (ED) with a persistent feeling that her heart is racing and skipping beats. She has had similar feelings several times in the past but never for more than a few minutes and always with spontaneous recovery. This episode occurred while she was playing water polo with her community league team, and to her surprise, it did not spontaneously dissipate as it had in the past. She began to feel drained of energy and stamina and thought she would pass out. She immediately got out of the pool and was quickly rushed to the ED.
{mosimage}On examination, the patient appears pale and diaphoretic, and it is clear that she is lethargic and has shortness of breath (dyspnea). Electrocardiographic monitoring (ECG) is quickly initiated (see Figure 1), and it reveals what appears to be ventricular tachycardia at a rate of 224 bpm, though the rhythm is somewhat irregular.
Her pulse is weak and thready and does not correspond to findings on auscultation or to her palpated heart rate of 250 bpm. Her blood pressure is 80/46 mm Hg. Synchronized cardioversion is performed and successfully converts the patient’s rhythm to a normal sinus rhythm at 58 bpm. She becomes more responsive, and her vital signs stabilize. A repeat ECG is obtained (see Figure 2).
What is this woman’s underlying disorder, and how should it be treated? Why did she appear to have ventricular tachycardia on her arrival to the ED?
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HINT
The patient did not have ventricular tachycardia.
Author:
Thomas J. Hemingway, MD, Staff Physician, Department of Emergency Medicine, Olive View – University of California at Los Angeles, and Rick Kulkarni, MD, Attending Physician, Department of Emergency Medicine, Olive View – UCLA Medical Center, Assistant Professor of Medicine, David Geffen School of Medicine at UCLA
eMedicine Editors:
Rick G. Kulkarni, MD,
Assistant Professor,
Yale School of Medicine,
Section of Emergency Medicine,
Department of Surgery,
Attending Physician,
Medical Director,
Department of Emergency Services,
Yale-New Haven Hospital, CT
John Vozenilek, MD, Division of Emergency Medicine, Evanston Northwestern Healthcare
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ANSWER
Wolff-Parkinson-White (WPW) syndrome: WPW syndrome is one of the classic preexcitation syndromes that result from an accessory pathway, such as the Kent bundle, between the atria and the ventricles. Impulses traveling down this pathway bypass all or part of the intrinsic conduction system, resulting in the early depolarization of a portion of the ventricles; this preexcitation produces the classic ECG finding called the delta wave (ie, a slurred upstroke to the QRS complex). This makes the QRS appear wider than expected, and the PR interval appears somewhat shortened. The classic ECG appearance of WPW syndrome is depicted in Figure 2.
WPW syndrome and Lown-Ganong-Levine (LGL) syndrome are 2 major variants of preexcitation, having an estimated prevalence of 0.1-0.3% in the general population. LGL syndrome is similar to WPW syndrome in that preexcitation is secondary to an accessory pathway (the James fibers) that directly connects the atria to the His bundle. In LGL syndrome, the ECG demonstrates a short PR interval (usually less than 0.12 s), without a delta wave and with a normal QRS complex. Both of these syndromes predispose patients to paroxysmal tachydysrhythmia (especially paroxysmal supraventricular tachycardia and atrial fibrillation). Related aberrant conduction, as in this case, can result in rapid ventricular rates of up to 300 bpm (which may be symptomatic and even lethal).
As many as 80% of patients with WPW syndrome have reentrant tachycardia, whereas 15-30% have atrial fibrillation and 5% have atrial flutter. Ventricular tachycardia is uncommon with WPW syndrome, though rapid atrial fibrillation with aberrant conduction can appear as ventricular tachycardia (as seen in Figure 1) and, because of excessive stimulation of the ventricles, can lead to ventricular fibrillation.
Initial treatment for acute tachydysrhythmia is as described in the American Heart Association’s Advanced Cardiac Life Support (ACLS) protocol. Synchronized cardioversion was performed because of the patient’s unstable condition. In general, if patients are stable and have narrow-complex tachydysrhythmia, adenosine can be tried first; however, adenosine can theoretically be harmful to those with antidromic reentrant conduction. Medications such as calcium channel blockers (eg, diltiazem, verapamil) and beta blockers (eg, metoprolol, esmolol, propranolol) should be avoided in this situation. Stable patients may be treated with intravenous procainamide; unstable patients may be treated with direct cardioversion. Medications that have variable effects on accessory conduction (eg, phenytoin, esmolol, propranolol, verapamil) should be avoided. Digoxin is absolutely contraindicated because it may shorten the refractory period and enhance conduction over the bypass tract, thus causing an even faster tachydysrhythmia or deterioration into ventricular fibrillation.
Some patients with WPW syndrome are at risk for sudden death, especially those with excessive unstable rhythms with short refractory periods, as in this case. In these patients, electrophysiologic cardiac studies and radiofrequency catheter ablation may be definitive and curative. Catheter ablation can also be used in patients with symptomatic supraventricular tachycardia. Some patients may refuse this somewhat invasive therapy and choose to undergo long-term antiarrhythmic therapy with drugs such as amiodarone, quinidine, or sotalol. Others without worrisome symptoms (ie, syncope, symptomatic tachyarrhythmias, wide-complex tachycardia of uncertain cause, associated structural heart disease, WPW syndrome with a family history of sudden death, recurrent trial fibrillation or atrial flutter) may be treated symptomatically.
References:
Dubin D. Rapid Interpretation of EKGs. 4th ed. Tampa, FL: Cover Publishing; 1988.
Singh, Vibhuti N. Wolff-Parkinson-White Syndrome. eMedicine.com. Available at: http://www.emedicine.com/med/topic2417.htm. Last updated July 10, 2006.
Tintinalli JE, Kelen GD, Stapczynski JS. Emergency Medicine: A Comprehensive Study Guide. 6th ed. New York, NY: McGraw-Hill Professional; 2003.
