@entity1425 QT stress testing in the evaluation of XXXX : diagnostic accuracy of the @entity1162 .

@entity1 @entity1788 @entity9677 @entity1425 @entity1162 @entity9678 @entity26320
BACKGROUND: A paradoxical increase in the uncorrected QT interval during infusion of low-dose @entity1425 appears pathognomonic for @entity26320 ( @entity9677 ). We sought to determine the diagnostic accuracy of this response among @entity1 referred for clinical evaluation of @entity1162 (LQTS). METHODS AND RESULTS: From 1999 to 2002, 147 genotyped @entity1 (125 untreated and 22 undergoing beta-blocker therapy) had an @entity1425 QT stress test that involved a 25-minute infusion protocol (0.025 to 0.3 microg.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 @entity1162 (defined as a > or =30-ms increase in QT during infusion of < or =0.1 microg.kg(-1).min(-1) @entity1425 ) was determined. The 125 untreated @entity1 (44 genotype negative, 40 @entity9677 , 30 @entity9678 , and 11 @entity1788 ) constituted the primary analysis. The median baseline corrected QT intervals (QTc) were 444 ms (gene negative), 456 ms ( @entity9677 ), 486 ms ( @entity9678 ), and 473 ms ( @entity1788 ). The median change in QT interval during low-dose @entity1425 infusion was -23 ms in the gene-negative group, 78 ms in @entity9677 , -4 ms in @entity9678 , and -58 ms in @entity1788 . The @entity1162 was observed in 37 (92%) of 40 @entity1 with @entity9677 compared with 18% (gene-negative), 13% ( @entity9678 ), and 0% ( @entity1788 ; P<0.0001) of the remaining @entity1 . Overall, the @entity1162 had a sensitivity of 92.5%, specificity of 86%, positive predictive value of 76%, and negative predictive value of 96% for @entity9677 status. Secondary analysis of the subset undergoing beta-blocker therapy indicated inferior diagnostic utility in this setting. CONCLUSIONS: The @entity1425 QT stress test can unmask concealed type 1 LQTS with a high level of accuracy.
