Vyas Himeshkumar, Hejlik Joseph, Ackerman Michael J
Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic College of Medicine, Rochester, MN, USA.
Circulation. 2006 Mar 21;113(11):1385-92. doi: 10.1161/CIRCULATIONAHA.105.600445. Epub 2006 Mar 13.
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).
From 1999 to 2002, 147 genotyped patients (125 untreated and 22 undergoing beta-blocker therapy) had an epinephrine 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 paradoxical QT response (defined as a > or =30-ms increase in QT during infusion of < or =0.1 microg.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 beta-blocker therapy indicated inferior diagnostic utility in this setting.
The epinephrine QT stress test can unmask concealed type 1 LQTS with a high level of accuracy.
在输注低剂量肾上腺素期间，未校正QT间期出现反常延长似乎是1型长QT综合征（LQT1）的特征性表现。我们试图确定在因先天性长QT综合征（LQTS）接受临床评估的患者中，这种反应的诊断准确性。
1999年至2002年，147例进行基因分型的患者（125例未接受治疗，22例正在接受β受体阻滞剂治疗）接受了肾上腺素QT应激试验，该试验采用25分钟的输注方案（0.025至0.3μg·kg⁻¹·min⁻¹）。持续监测12导联心电图，并测量复极参数。确定反常QT反应（定义为在输注≤0.1μg·kg⁻¹·min⁻¹肾上腺素期间QT增加≥30ms）的敏感性、特异性、阳性预测值和阴性预测值。125例未接受治疗的患者（44例基因阴性，40例LQT1，30例LQT2，11例LQT3）构成主要分析对象。基因阴性组、LQT1组、LQT2组和LQT3组的基线校正QT间期（QTc）中位数分别为444ms、456ms、486ms和473ms。低剂量肾上腺素输注期间QT间期的中位数变化在基因阴性组为-23ms，LQT1组为78ms，LQT2组为-4ms，LQT3组为-58ms。40例LQT1患者中有37例（92%）出现反常QT反应，而其余患者中基因阴性组为18%，LQT2组为13%，LQT3组为0%（P<0.0001）。总体而言，反常QT反应对LQT1状态的敏感性为92.5%，特异性为86%，阳性预测值为76%，阴性预测值为96%。对接受β受体阻滞剂治疗的亚组进行的次要分析表明，在这种情况下诊断效用较差。
肾上腺素QT应激试验能够以较高的准确性揭示隐匿性1型LQTS。
