Introduction: In established cLQTS patients the QT interval can be normal or slightly prolonged, with significant prolongation needed for diagnosis on standard resting ECGs, meaning there are potentially undiagnosed people susceptible to SCD. Simple autonomic manoeuvres such as postural changes can aid the diagnosis of cLQTS.
Methods: Continuous 12-lead ECGs were digitally recorded in 38 patients with congenital LQTS genotype and 30 healthy controls (each in whom two recordings were made) in the supine and abrupt standing position, both for 5 minutes. Through specialised software the QT interval was measured and corrected using Fridericia’s formula.
Results: On standing, healthy subjects demonstrated average QT shortening by 16 and 17ms respectively. In cLQTS patients the QT interval prolonged by an average of 1ms, with a maximum prolongation of 64ms observed.
Conclusions: The similarity of results in healthy subjects suggests the test is reproducible, with expected prolongation elicited amongst cLQTS patients. Therefore this technique can help more accurately establish the LQTS diagnosis, especially in patients with cLQTS in whom the resting ECG is non-diagnostic, whilst being simple, safe and easily performable at bedside.