title: Value of the "Standing Test" in the Diagnosis and Evaluation of Beta-blocker Therapy Response in Long QT Syndrome.
abstract: OBJECTIVE
  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 QTcstandingand ΔQTc were significantly higher in the LQTS group than in controls (QTcstanding, 528 ± 46ms vs 420 ± 15ms, P < .0001; ΔQTc, 78 ± 40ms vs 8 ± 13ms, 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 QTcstandingand 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 ± 32ms, P < .0001; ΔQTc, 14 ± 16ms, 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.
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain. Electronic address: carmue83@gmail.com.
authors.forename: Carmen
authors.initials: C
authors.lastname: Muñoz-Esparza
authors.affiliation: Unidad de Valoración del Riesgo de Muerte Súbita Familiar, Servicio de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain.
authors.forename: Esther
authors.initials: E
authors.lastname: Zorio
authors.affiliation: Unidad de Valoración del Riesgo de Muerte Súbita Familiar, Servicio de Cardiología, Hospital Universitario y Politécnico La Fe, Valencia, Spain.
authors.forename: Diana
authors.initials: D
authors.lastname: Domingo Valero
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Peñafiel-Verdú
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Sánchez-Muñoz
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Esperanza
authors.initials: E
authors.lastname: García-Molina
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Sabater
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Marina
authors.initials: M
authors.lastname: Navarro
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: San-Román
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Pérez
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Santos
authors.affiliation: Departamento de Hematología y Análisis Clínico, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Valentín
authors.initials: V
authors.lastname: Cabañas-Perianes
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Mariano
authors.initials: M
authors.lastname: Valdés
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Domingo
authors.initials: D
authors.lastname: Pascual
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Arcadio
authors.initials: A
authors.lastname: García-Alberola
authors.affiliation: Unidad de Cardiopatías Familiares, Hospital Clínico Universitario Virgen de la Arrixaca, Universidad de Murcia, Instituto Murciano de Investigación Biosanitaria, Murcia, Spain.
authors.forename: Juan R
authors.initials: JR
authors.lastname: Gimeno Blanes
mesh_terms: D000319:Adrenergic beta-Antagonists; D000328:Adult; D016022:Case-Control Studies; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000188:drug therapy / Q000503:physiopathology; D008297:Male; D000067716:Point-of-Care Testing; D011187:Posture; D012372:ROC Curve
chemical_list: D000319:Adrenergic beta-Antagonists
keywords: Beta-blocker therapy; Corrected QT interval; Intervalo QT corregido; Long QT syndrome; Morfología de la onda T; Standing test; Síndrome de QT largo; T wave morphology; Test de bipedestación; Tratamiento con bloqueadores beta