OBJECTIVES: The aim of this study was to develop a diagnostic technique to detect latent long QT syndrome. BACKGROUND: Asymptomatic patients with genetically diagnosed long QT syndrome (LQTS) may have a normal resting QT interval, yet remain at risk for cardiac events. We hypothesized that the QT response during a novel burst exercise protocol simulating clinical events might distinguish patients with "latent LQTS" from healthy subjects. METHODS: A burst bicycle protocol was performed on 31 healthy subjects and 31 patients with LQTS (13 LQT2, 3 LQT1, 15 unknown genotype). The bicycle exercise protocol involved sudden maximal exertion against a fixed workload (200 W) for 1 minute. Digitized 12-lead eletrocardiograms were acquired every 10 seconds at baseline for 1 minute, during 1 minute of burst exercise, and for 5 minutes during recovery. Patients with LQTS were segregated according to whether the baseline QTc was normal (< or = 440 milliseconds, n = 13) or abnormal (> 440 milliseconds, n = 18). RESULTS: During exercise, the QTc increased to a greater extent in the group with latent LQTS (DeltaQTc 98 +/- 36 milliseconds) in comparison with controls (DeltaQTc 65 +/- 19 milliseconds, P < .01) and those with baseline QTc prolongation (DeltaQTc 17 +/- 70 milliseconds, P < .01). In patients with a normal baseline QTc, a DeltaQTc > 85 milliseconds had a sensitivity of 85% and a specificity of 86% for LQTS (P = .0004). CONCLUSION: Marked QTc prolongation during burst bicycle ergometry provides potentially diagnostic information for patients with normal baseline QTc and suspected LQTS.
OBJECTIVES: The aim of this study was to develop a diagnostic technique to detect latent long QT syndrome. BACKGROUND: Asymptomatic patients with genetically diagnosed long QT syndrome (LQTS) may have a normal resting QT interval, yet remain at risk for cardiac events. We hypothesized that the QT response during a novel burst exercise protocol simulating clinical events might distinguish patients with "latent LQTS" from healthy subjects. METHODS: A burst bicycle protocol was performed on 31 healthy subjects and 31 patients with LQTS (13 LQT2, 3 LQT1, 15 unknown genotype). The bicycle exercise protocol involved sudden maximal exertion against a fixed workload (200 W) for 1 minute. Digitized 12-lead eletrocardiograms were acquired every 10 seconds at baseline for 1 minute, during 1 minute of burst exercise, and for 5 minutes during recovery. Patients with LQTS were segregated according to whether the baseline QTc was normal (< or = 440 milliseconds, n = 13) or abnormal (> 440 milliseconds, n = 18). RESULTS: During exercise, the QTc increased to a greater extent in the group with latent LQTS (DeltaQTc 98 +/- 36 milliseconds) in comparison with controls (DeltaQTc 65 +/- 19 milliseconds, P < .01) and those with baseline QTc prolongation (DeltaQTc 17 +/- 70 milliseconds, P < .01). In patients with a normal baseline QTc, a DeltaQTc > 85 milliseconds had a sensitivity of 85% and a specificity of 86% for LQTS (P = .0004). CONCLUSION: Marked QTc prolongation during burst bicycle ergometry provides potentially diagnostic information for patients with normal baseline QTc and suspected LQTS.
Authors: Peter F Aziz; Tammy S Wieand; Jamie Ganley; Jacqueline Henderson; Akash R Patel; V Ramesh Iyer; R Lee Vogel; Michael McBride; Victoria L Vetter; Maully J Shah Journal: Circ Arrhythm Electrophysiol Date: 2011-09-28
Authors: Christina Abrahamsson; Corina Dota; Bo Skallefell; Leif Carlsson; Lars Frison; Anders Berggren; Nils Edvardsson; Göran Duker Journal: Ann Noninvasive Electrocardiol Date: 2012-11-22 Impact factor: 1.468