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CLINICAL RESEARCH: HEART RHYTHM DISORDERS

Clinical and Electrophysiological Spectrum of Idiopathic Ventricular Outflow Tract Arrhythmias

Department of Medicine, Division of Cardiology, Cornell University Medical Center, New York, New York

Manuscript received November 2, 2006; revised manuscript received January 17, 2007, accepted January 28, 2007.

^_* Reprint requests and correspondence: Dr. Bruce B. Lerman, Division of Cardiology, Cornell University Medical Center, 525 East 68th Street, Starr 409, New York, New York 10021. (Email: blerman{at}med.cornell.edu).

Objectives: This study sought to compare and contrast the clinical and electrophysiological characteristics of outflow tract arrhythmias.

Background: Idiopathic ventricular outflow tract arrhythmias manifest clinically in 3 forms: 1) paroxysmal sustained monomorphic ventricular tachycardia (SMVT), 2) repetitive nonsustained ventricular tachycardia (NSVT), or 3) premature ventricular contractions (PVCs). Although these arrhythmias have a similar site of origin, it is unknown whether they share a common mechanism or similar clinical features.

Methods: A total of 127 patients (63 female [50%], mean age 51 ± 15 years) were evaluated for outflow tract arrhythmias.

Results: A total of 36 (28%) presented with the index clinical arrhythmia of SMVT, 46 (36%) with NSVT, and 45 (35%) with PVCs. The sites of origin of the arrhythmias were similar among the 3 groups, occurring in the right ventricular outflow tract in 82%. Sustained ventricular tachycardia was more likely to be induced during exercise in the SMVT (10 of 15 patients [67%]) than NSVT or PVCs groups (p < 0.01). Sustained outflow tract ventricular tachycardia was induced at electrophysiology study in 78% of SMVT patients, 48% of NSVT patients, and 4% of PVCs patients. Adenosine was similarly effective in all 3 groups (p = NS).

Conclusions: Patients with outflow tract arrhythmias can be differentiated based on the subtype of arrhythmia. However, the observation that approximately 50% of patients with NSVT and 5% of patients with PVCs have inducible sustained ventricular tachycardia that behaves in an identically unique manner to those who present with sustained ventricular tachycardia (e.g., adenosine-sensitive) suggests that rather than representing distinct entities, outflow arrhythmias may be considered a continuum of a single mechanism.

Abbreviations and Acronyms   ECG = electrocardiogram   MRI = magnetic resonance imaging   NSVT = nonsustained ventricular tachycardia   PVC = premature ventricular contraction   RMVT = repetitive monomorphic ventricular tachycardia   SMVT = sustained monomorphic ventricular tachycardia   TWA = T-wave alternans   VT = ventricular tachycardia

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