Published online before print March 13, 2006, doi: 10.1161/CIRCULATIONAHA.105.600445
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Circulation. 2006;113:1385-1392.)
© 2006 American Heart Association, Inc.
Arrhythmia/Electrophysiology |
Epinephrine QT Stress Testing in the Evaluation of Congenital Long-QT Syndrome
Diagnostic Accuracy of the Paradoxical QT Response
From the Department of Pediatric and Adolescent Medicine/Division of Pediatric Cardiology (H.V., M.J.A.), Department of Medicine/Division of Cardiovascular Diseases (J.H., M.J.A.), and Department of Molecular Pharmacology & Experimental Therapeutics (M.J.A.); Mayo Clinic College of Medicine, Rochester, Minn.
Correspondence to Michael J. Ackerman, MD, PhD, Long QT Syndrome Clinic and Sudden Death Genomics Laboratory, Guggenheim 501, Mayo Clinic, Rochester, MN 55905. E-mail ackerman.michael{at}mayo.edu
Received November 9, 2005; revision received December 22, 2005; accepted January 13, 2006.
Background— A paradoxical increase in the uncorrected QT interval during infusion of low-dose epinephrine appears pathognomonic for type 1 long-QT syndrome (LQT1). We sought to determine the diagnostic accuracy of this response among patients referred for clinical evaluation of congenital long-QT syndrome (LQTS).
Methods and Results— From 1999 to 2002, 147 genotyped patients (125 untreated and 22 undergoing ß-blocker therapy) had an epinephrine QT stress test that involved a 25-minute infusion protocol (0.025 to 0.3 µg · kg–1 · min–1). A 12-lead ECG was monitored continuously, and repolarization parameters were measured. The sensitivity, specificity, and positive and negative predictive values for the paradoxical QT response (defined as a 
30-ms increase in QT during infusion of 
0.1 µg · kg–1 · min–1 epinephrine) was determined. The 125 untreated patients (44 genotype negative, 40 LQT1, 30 LQT2, and 11 LQT3) constituted the primary analysis. The median baseline corrected QT intervals (QTc) were 444 ms (gene negative), 456 ms (LQT1), 486 ms (LQT2), and 473 ms (LQT3). The median change in QT interval during low-dose epinephrine infusion was –23 ms in the gene-negative group, 78 ms in LQT1, –4 ms in LQT2, and –58 ms in LQT3. The paradoxical QT response was observed in 37 (92%) of 40 patients with LQT1 compared with 18% (gene-negative), 13% (LQT2), and 0% (LQT3; P<0.0001) of the remaining patients. Overall, the paradoxical QT response had a sensitivity of 92.5%, specificity of 86%, positive predictive value of 76%, and negative predictive value of 96% for LQT1 status. Secondary analysis of the subset undergoing ß-blocker therapy indicated inferior diagnostic utility in this setting.
Conclusions— The epinephrine QT stress test can unmask concealed type 1 LQTS with a high level of accuracy.
CLINICAL PERSPECTIVE
Related Article:
-
Issue Highlights
Circulation 2006 113: 1377.[Extract] [Full Text]
This article has been cited by other articles:
 |
|
 |
|
  C. I. Berul Congenital Long-QT Syndromes: Who's at Risk for Sudden Cardiac Death? Circulation, April 29, 2008; 117(17): 2178 - 2180. [Full Text] [PDF]
|
|
|
|
 |
|
 D. M. Roden Long-QT Syndrome N. Engl. J. Med., January 10, 2008; 358(2): 169 - 176. [Full Text] [PDF]
|
|
|
|
 |
|
 S. Balaji Long QT Syndrome in Children: Not One Disease Anymore J. Am. Coll. Cardiol., October 2, 2007; 50(14): 1341 - 1342. [Full Text] [PDF]
|
|
|
|
|
|
N. W. Taggart, C. M. Haglund;, D. J. Tester, and M. J. Ackerman Diagnostic Miscues in Congenital Long-QT Syndrome Circulation, May 22, 2007; 115(20): 2613 - 2620. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. M. Karp and A. J. Moss Authors' response J Am Dent Assoc, August 1, 2006; 137(8): 1069 - 1070. [Full Text] [PDF]
|
|