Syncope and Palpitation: A Case

A 37-year-old woman with a history of anxiety disorder presents to the emergency department (ED) with concern for panic attack. She describes a sensation of chest-pounding palpitations, racing heart rate, severe dyspnea, and lightheadedness. She is beginning to feel some chest heaviness. She has a several-year history of these intermittent symptoms, which she ascribes to her "panic attacks." These paroxysms often last for 10-15 minutes and spontaneously subside before her arrival to the ED. In the past, she had an extensive but essentially normal cardiac work-up, which included electrocardiography, exercise treadmill test, 24-hour Holter monitor, and echocardiography. She notes that she was asymptomatic at the time that the studies were being conducted. Her primary care provider diagnosed her with anxiety disorder with panic attacks and prescribed a selective serotonin reuptake inhibitor (SSRI). Despite treatment, she has had several episodes per year. They do not appear to be associated with anything in particular. Her current episode began while she was playing water polo with her community league team and, to her surprise, it did not spontaneously subside. She began to feel drained of her usual energy and stamina and thought that she would pass out. She immediately got out of the pool and was quickly rushed to the ED by her friends.

On initial physical examination, the patient is a young woman in athletic condition who appears pale and diaphoretic. In general, she is somewhat lethargic and in mild respiratory distress. Her heart rate is irregular and tachycardic, ranging from 170 to 300 bpm. Her blood pressure is 80/46 mm Hg. Her respiratory rate is 18 breaths/min, with an oxygen saturation of 99% on 2 L. Her heart sounds include an S1 and S2, with an irregular tachycardic rhythm. The patient's lung sounds are clear to auscultation bilaterally. Her extremities are free of edema, but they are cool and with faint distal pulses.

The initial electrocardiogram (ECG, see Figure 1) reveals an irregular, wide complex tachycardia at a rate of 224 bpm. Because of her altered mentation and significant hypotension, the American Heart Association's (AHA's) Advanced Cardiac Life Support (ACLS) algorithm^[1] is initiated by the ED staff, and a synchronized cardioversion is performed. The patient converts to a normal sinus rhythm at a heart rate of 58 bpm. A repeat 12-lead ECG is obtained (see Figure 2).

On the basis of the clinical presentation and the first ECG, what is the diagnosis?

Hint: The key to diagnosis is combining the rate and morphology of the QRS complex with an understanding of whether the rhythm is regular, irregular, or irregularly irregular. The ECG in Figure 1 is unique and considered pathognomonic

Diagnosis: Wolff-Parkinson-White syndrome with atrial fibrillation