Value of the “Standing Test” in the Diagnosis and Evaluation of Beta-blocker Therapy Response in Long QT Syndrome

• Published in: Revista española de cardiología (English ed.) Vol. 70; no. 11; pp. 907 - 914
• Main Authors: Muñoz-Esparza, Carmen, Zorio, Esther, Domingo Valero, Diana, Peñafiel-Verdú, Pablo, Sánchez-Muñoz, Juan J, García-Molina, Esperanza, Sabater, María, Navarro, Marina, San-Román, Irene, Pérez, Inmaculada, Santos, Juan J, Cabañas-Perianes, Valentín, Valdés, Mariano, Pascual, Domingo, García-Alberola, Arcadio, Gimeno Blanes, Juan R
• Format: Journal Article
• Language: English; Spanish
• Published: Spain 01-11-2017
• Subjects: Adrenergic beta-Antagonists; Adult; Cardiovascular; Case-Control Studies; Exercise Test - methods; Female; Heart Rate; Humans; Internal Medicine; Long QT Syndrome - diagnosis; Long QT Syndrome - drug therapy; Long QT Syndrome - physiopathology; Male; Point-of-Care Testing; Posture; ROC Curve; Corrected QT interval; BB; Test de bipedestación; Síndrome de QT largo; corrected QT interval change from baseline; beta-blocker; Morfología de la onda T; LQTS; ECG; ΔQTc; electrocardiogram; Standing test; Long QT syndrome; Beta-blocker therapy; Intervalo QT corregido; Tratamiento con bloqueadores beta; T wave morphology
• ISSN: 1885-5857; 1885-5857
• DOI: 10.1016/j.rec.2017.01.006

Abstract Introduction and objectives Patients with congenital long QT syndrome (LQTS) have an abnormal QT adaptation to sudden changes in heart rate provoked by standing. The present study sought to evaluate the standing test in a cohort of LQTS patients and to assess if this QT maladaptation phenomenon is ameliorated by beta-blocker therapy. Methods Electrographic assessments were performed at baseline and immediately after standing in 36 LQTS patients (6 LQT1 [17%], 20 LQT2 [56%], 3 LQT7 [8%], 7 unidentified-genotype patients [19%]) and 41 controls. The corrected QT interval (QTc) was measured at baseline (QTcsupine ) and immediately after standing (QTcstanding ); the QTc change from baseline (ΔQTc) was calculated as QTcstanding – QTcsupine . The test was repeated in 26 patients receiving beta-blocker therapy. Results Both QTcstanding and ΔQTc were significantly higher in the LQTS group than in controls (QTcstanding , 528 ± 46 ms vs 420 ± 15 ms, P < .0001; ΔQTc, 78 ± 40 ms vs 8 ± 13 ms, P < .0001). No significant differences were noted between LQT1 and LQT2 patients. Typical ST-T wave patterns appeared after standing in LQTS patients. Receiver operating characteristic curves of QTcstanding and ΔQTc showed a significant increase in diagnostic value compared with the QTcsupine (area under the curve for both, 0.99 vs 0.85; P < .001). Beta-blockers attenuated the response to standing in LQTS patients (QTcstanding , 440 ± 32 ms, P < .0001; ΔQTc, 14 ± 16 ms, P < .0001). Conclusions Evaluation of the QTc after the simple maneuver of standing shows a high diagnostic performance and could be important for monitoring the effects of beta-blocker therapy in LQTS patients.