52-year-old man • syncopal episode • chest pain • mild lightheadedness • Dx?

DISCUSSION

Guidelines from the American College of Cardiology/American Heart Association/Heart Rhythm Society recommend a detailed history and physical exam, as well as an EKG, for the initial evaluation of syncope.² If this does not point to a diagnosis (and depending on the presentation and other factors), an ambulatory rhythm monitor can be considered. Other possible testing modalities include stress testing, resting transthoracic echocardiography, electrophysiologic testing, and cardiac magnetic resonance imaging or computed tomography.

Is the cause cardiac? The guidelines suggest that a cardiac cause of syncope is more likely if several of the following factors are present: age > 60 years; male sex; presence of known heart disease (acquired or congenital); brief prodrome (eg, palpitations) or no prodrome; exertional or supine syncope; 1 to 2 episodes; an abnormal cardiac exam; and a family history of premature sudden death.² A noncardiac cause is suggested by other factors: younger age; no known cardiac disease; standing or a position change from supine to sitting/standing; prodrome; specific triggers (eg, dehydration, pain); and frequent and prolonged stereotypic episodes.²

Our patient experienced syncope upon standing, which suggested a noncardiac cause. However, his history of palpitations increased our suspicion for a cardiac cause.

While the guidelines do not specify the number of factors or endorse a specific scoring system, such tools have been developed. For example, the EGSYS (Evaluation of Guidelines in Syncope Study) Score assigns 1 point for each of 6 factors: palpitations; heart disease and/or abnormal EKG; effort syncope; supine syncope; precipitating or predisposing factors; and autonomic prodromes. A score ≥ 3 identified cardiac syncope with a sensitivity of 95%, but with a specificity of only 61%. In the derivation study, patients with a score ≥ 3 had higher mortality than those with a lower score (17 vs 3%; P < .001).³

Myocardial ischemia can trigger ventricular arrhythmias. In the GUSTO-1 trial of fibrinolytic therapy in patients with acute ST-segment elevation myocardial infarction (n = 40,895), the incidence of ventricular tachycardia or ventricular fibrillation was 10.2%.⁴ In a pooled analysis (4 trials; n = 26,416) of patients who were treated for non–ST-segment elevation or unstable ­angina-type acute coronary syndromes, the rate of these arrhythmias was markedly lower (2.1%).⁵ The risk of ventricular arrhythmia is one reason close monitoring (eg, continuous telemetry, ICU admission) is the standard of care for patients with acute coronary syndromes.

Our patient experienced syncope upon standing, which suggested a noncardiac cause (usually orthostatic hypotension). However, the history of palpitations increased the suspicion for a cardiac cause, and thus the rhythm monitor was ordered.

THE TAKEAWAY

This case was unusual in that ambulatory monitoring captured electrocardiographic evidence of myocardial ischemia leading directly to a ventricular arrhythmia. In the evaluation of syncope, a detailed history, physical exam, and a baseline 12-lead EKG can sometimes give clues to an arrhythmic cause of syncope (eg, Brugada syndrome, prior infarct pattern, prolonged QTc, bradycardia, heart block, arrhythmogenic right ventricular cardiomyopathy)—but prolonged rhythm monitoring is sometimes needed to identify a cause.

CORRESPONDENCE
Michael A. Chen, MD, PhD, Harborview Medical Center, University of Washington School of Medicine, 325 9th Avenue, Box 359748 (Cardiology), Seattle, WA 98104; michen@u.washington.edu