title: Limb lead interchange in thorough QT/QTc studies.
abstract: The investigators analyzed 85,133 electrocardiograms (ECGs) recorded in 484 subjects from 5 thorough QT/QTc studies (3 using Holter devices, 2 using 12-lead ECGs) for inadvertent limb lead interchanges using a dedicated quality control process in a central ECG laboratory. Limb lead interchanges were present in 2919 (3.4%) ECGs in 17.9% of subjects and were more frequent with Holter devices (7.5% vs 0.8%, P < .0001), where leads remain connected for prolonged periods, affecting data from several time points. Left arm-left leg interchange was seen in 54% of 12-lead ECGs and right arm-left arm interchange in 38%. The ECG device itself could identify 21.7% of interchanges, whereas experienced readers blinded to subject and visit identified 79% of interchanges; 21% of interchanges were identified only during the quality control process. If correctly identified, QT measurement could be performed in a precordial lead. If undiagnosed, incorrect QT interval measurements and morphological diagnosis may confound results.
authors.affiliation: Quintiles Cardiac Safety Services, 502 A, Leela Business Park, M.V. Road, Andheri (East), Mumbai 400 059, India. vaibhav.salvi@quintiles.com
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Salvi
authors.forename: Dilip R
authors.initials: DR
authors.lastname: Karnad
authors.forename: Gopi Krishna
authors.initials: GK
authors.lastname: Panicker
authors.forename: Snehal
authors.initials: S
authors.lastname: Kothari
authors.forename: Pooja
authors.initials: P
authors.lastname: Hingorani
authors.forename: Mili
authors.initials: M
authors.lastname: Natekar
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Mahajan
authors.forename: Dhiraj
authors.initials: D
authors.lastname: Narula
mesh_terms: D004562:Electrocardiography / Q000295:instrumentation*; D004566:Electrodes; D006329:Heart Conduction System / Q000502:physiology*; D006801:Humans