Utility of the recovery electrocardiogram after exercise: a novel indicator for the diagnosis and genotyping of long QT syndrome?

Abstract

BACKGROUND:

Exercise testing has shown modest utility in the ability to diagnose and genotype long QT syndrome (LQTS). Although numerous small studies have shown a genotype-specific repolarization response to exercise, the repolarization responses during recovery from exercise have received less focus.

OBJECTIVE:

The purpose of this study was to characterize genotype-specific QT responses during recovery from exercise and to determine its potential as a diagnostic and genotyping tool.

METHODS:

Seventy-five patients were age and sex matched into three groups (n = 25): LQT1, LQT2, and unaffected controls based on Schwartz score and genetic testing results. Each group underwent upright burst and gradual bicycle exercise testing while being monitored by 12-lead electrocardiogram.

RESULTS:

LQT1 patients had significantly longer corrected QT (QTc) than LQT2 intervals during early recovery (P <.01). Control subjects showed little variation in QTc throughout the recovery period, maintaining a QTc within normal limits. Each group showed a distinct pattern of QTc adaptation during recovery. LQT1 patients began the recovery period at a QTc of 492 +/- 11 ms, after which the QTc decreased by 33 +/- 11 ms during recovery. Conversely, the LQT2 patients began recovery at its lowest mean QTc of 420 +/- 10 ms, which increased by 40 +/- 16 ms. At the end of recovery, a QTc cut-off value of 445 ms distinguished 92% of LQTS patients from unaffected controls, while a start-of-recovery QTc cut-off of 460 ms correctly identified genotype in 80% of LQT1 and 92% of LQT2 patients.

CONCLUSIONS:

Genotype-specific differences exist in QT recovery after exercise. These differences can help to identify LQTS patients and distinguish LQT1 from LQT2 genotypes.

• Authors: Ishvinder S Chattha, Raymond W Sy, Raymond Yee, Lorne J Gula, Allan C Skanes, George J Klein, Matthew T Bennett, Andrew D Krahn
• Journal: Heart rhythm (Heart Rhythm) Vol. 7 Issue 7 Pg. 906-11 (Jul 2010) ISSN: 1556-3871 [Electronic] United States
• PMID: 20226272 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright 2010 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Topics

• Adaptation, Physiological
• Adolescent
• Adult
• Aged
• Child
• Electrocardiography
• Exercise (physiology)
• Exercise Test
• Female
• Genotype
• Humans
• Long QT Syndrome (genetics)
• Male
• Middle Aged
• Young Adult