Ventricular ectopy during treadmill exercise stress testing in the evaluation of long QT syndrome

Abstract

Background Long QT syndrome (LQTS) can present with sudden death during exertion. Objective To determine the diagnostic importance of exercise-induced ventricular ectopy in the evaluation of LQTS. Methods From 1998 to 2006, 381 patients with a referral diagnosis of LQTS had a treadmill exercise stress test. Blinded to both genotype and rendered diagnosis, the stress tests were scored for the presence of exercise-induced ventricular ectopy. Results The dismissal diagnosis was LQTS in only 177 (46%), catecholaminergic polymorphic ventricular tachycardia (CPVT, 16), miscellaneous cardiac disease (17), and normal (171). Exercise-induced ventricular ectopy was detected in 107 patients (28%). However, only 34 patients (9% overall) had exercise-induced ventricular ectopy greater than single premature ventricular contractions (PVCs). Among the 171 patients dismissed as normal, only 2% had ectopy greater than single PVCs. Among the genotype positive LQTS patients, no significant ectopy was recorded in 80 with LQT1, compared to either 5 (8%) with LQT2, or 3 (20%) with LQT3 (p < 0.0001). In contrast, exercise-induced ventricular ectopy beyond single PVCs was far more common among patients with CPVT (14/16, 88%, p < 0.0001) and included PVCs in bigeminy in 13 (81%), couplets in 7 (47%), and NSVT in 3 (20%). Of note, bi-directional VT was not present in any of the 16 patients diagnosed with CPVT including the 10 with genetically proven, RYR2-mediated CPVT. Conclusion Exercise-induced ventricular ectopy exceeding single PVCs was observed in < 10% of patients referred for LQTS evaluation including 2% of patients ultimately dismissed as normal. Exercise-induced bigeminy is strongly associated with the presence of significant cardiovascular disease but is far more likely to indicate CPVT rather than LQTS.

Nonsustained Ventricular Tachycardia

“…QRS morphology suggests an outflow tract origin of the initiating beat in more than 50% of patients, and subsequent beats portray a polymorphic or typically bidirectional VT morphology (46). NSVT induced by treadmill exercise testing aimed at evaluating presumed LQTS suggests catecholaminergic polymorphic VT rather than LQTS (47). Beta-blocker therapy is the treatment of choice, probably together with calcium-channel blockers (48).…”

The Prevalence of Arrhythmias, Predictors for Arrhythmias, and Safety of Exercise Stress Testing in Children

“…It has been used as part of the diagnostic evaluation for arrhythmias and arrhythmia disorders such as long QT syndrome, catecholiminergic VT, and frequent ventricular ectopy. [4,8,10] It has also been used to assess the utility of anti-arrhythmic medications in many of these conditions [18]. In addition, recent guidelines published through the Heart Rhythm Society have suggested that an exercise stress test should be considered in the evaluation of young patients greater than 8 years of age with asymptomatic ventricular pre-excitation (WPW) [3].…”

Catecholaminergic Polymorphic Ventricular Tachycardia in 2012

“…In patients with or suspected for long QT syndrome (in particular type 1) exercise testing may also trigger ventricular arrhythmias, but ventricular ectopy beyond isolated VPBs is much more common (87.5%) in CPVT patients as compared with long QT syndrome patients (7%). 35 The presence of bigeminy has a specificity of 96% and a sensitivity of 81% for CPVT. 35 Holter monitoring may be used as an alternative test, for instance in children that are too young to undergo exercise testing, or when a patient's symptoms are more emotion-then exercise-related.…”

“…35 The presence of bigeminy has a specificity of 96% and a sensitivity of 81% for CPVT. 35 Holter monitoring may be used as an alternative test, for instance in children that are too young to undergo exercise testing, or when a patient's symptoms are more emotion-then exercise-related. Finally, catecholamine infusion may be used to unmask CPVT.…”