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(Circulation. 2009;120:278-285.)
© 2009 American Heart Association, Inc.

Arrhythmia/Electrophysiology

Systematic Assessment of Patients With Unexplained Cardiac Arrest

Cardiac Arrest Survivors With Preserved Ejection Fraction Registry (CASPER)

Andrew D. Krahn, MD; Jeffrey S. Healey, MD; Vijay Chauhan, MD; David H. Birnie, MD; Christopher S. Simpson, MD; Jean Champagne, MD; Martin Gardner, MD; Shubhayan Sanatani, MD; Derek V. Exner, MD; George J. Klein, MD; Raymond Yee, MD; Allan C. Skanes, MD; Lorne J. Gula, MD; Michael H. Gollob, MD

From University of Western Ontario (A.D.K., G.J.K., R.Y., A.C.S., L.J.G.), London, Ontario, Canada; Hamilton Health Sciences Center (J.S.H.), Hamilton, Ontario, Canada; University Health Network (V.C.), Toronto, Ontario, Canada; University of Ottawa Heart Institute (D.H.B., M.H.G.), Ottawa, Ontario, Canada; Queen’s University (C.S.S.), Kingston, Ontario, Canada; Quebec Heart Institute (J.C.), Laval Hospital, Quebec City, Quebec, Canada; QEII Health Sciences Center (M.G.), Halifax, Nova Scotia, Canada; BC Children’s Hospital (S.S.), Vancouver, British Columbia, Canada; and Foothills Hospital (D.V.E.), Calgary, Alberta, Canada.

Correspondence to Dr Andrew Krahn, Arrhythmia Service, London Health Sciences Centre, 339 Windermere Rd, London, Ontario, Canada N6A 5A5. E-mail akrahn{at}uwo.ca

Received January 22, 2009; accepted May 6, 2009.

Background— Cardiac arrest without evident cardiac disease may be caused by subclinical genetic conditions. Provocative testing to unmask a phenotype is often necessary to detect primary electrical disease, direct genetic testing, and perform family screening.

Methods and Results— Patients with apparently unexplained cardiac arrest and no evident cardiac disease (normal cardiac function on echocardiogram, no evidence of coronary artery disease, and a normal ECG) underwent systematic evaluation that included cardiac magnetic resonance imaging, signal-averaged ECG, exercise testing, drug challenge, and selective electrophysiological testing. Diagnostic criteria were based on accepted criteria or provocation of the characteristic clinical features for long-QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarization, arrhythmogenic right ventricular cardiomyopathy, coronary spasm, and myocarditis. Sixty-three patients in 9 centers were enrolled (age 43.0±13.4 years, 29 women). A diagnosis was obtained in 35 patients (56%): Long-QT syndrome in 8, catecholaminergic polymorphic ventricular tachycardia in 8, arrhythmogenic right ventricular cardiomyopathy in 6, early repolarization in 5, coronary spasm in 4, Brugada syndrome in 3, and myocarditis in 1. Targeted genetic testing demonstrated evidence of causative mutations in 9 (47%) of 19 patients. Screening of 64 family members of these patients identified 15 affected individuals who were treated (24%). The remaining 28 patients (44%) were considered to have idiopathic ventricular fibrillation.

Conclusions— Systematic clinical testing, including drug provocation and advanced imaging, results in unmasking of the cause of apparently unexplained cardiac arrest in >50% of patients. This approach assists in directing genetic testing to diagnose genetically mediated arrhythmia syndromes, which results in successful family screening.

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