Introduction
Drug-induced prolongation of the QT interval (diLQTS) substantially
increases the risk for Torsades de Pointes (TdP) and sudden
death.1 Offending agents include widely used drugs
like antibiotics, antimalarials, antifungals, antivirals,
anti-arrhythmic drugs (AAD), psychiatric drugs, and many
others.1–3 In the current context of severe acute
respiratory syndrome coronavirus 2 (SARS-CoV2)
infections,4 drugs with a risk for diLQTS, like
hydroxychloroquine, azithromycin or antiviral drugs, are used widely
off-label and are investigated in randomized trials in large patient
populations.5 Expert consensus statements therefore
recommend ECG screening for QT interval prolongation before treatment
initiation and regularly during treatment with these
drugs.6,7 However, repeated ECG screening using
12-lead ECG is clinically unfeasible in the large number of isolated,
hospitalized or ambulatory patients, may increase the risk for virus
transmission and is economically unfeasible in low-income countries.
Mobile ECG devices seem to be able to reconstruct the six ECG limb leads
with good reproducibility of basic ECG intervals compared to
conventional 12-lead ECGs in patients with normal and prolonged QT
interval.8–11 They might therefore offer a
lower-cost, clinically more convenient and safer screening modality for
QT prolongation in diLQTS used by the patients themselves. However, as
T-wave morphology in the limb leads may flatten in very long QT
intervals with the highest risk for TdP, the diagnostic accuracy and
interpretability of the QT interval might be low if only limb leads are
used.12 Currently, systematic data on the diagnostic
value of the limb versus chest leads for prolonged QT interval and
T-wave morphology in patients with diLQTS and subsequent TdP are
lacking.
We therefore aimed to systematically investigate the diagnostic value
and interpretability of the limb versus the chest ECG leads in patients
with diLQTS, who subsequently experienced TdP.