Electrocardiographic Biomarkers of Ventricular Repolarisation in a Single Family of Short QT Syndrome and the Role of the Bazett Correction Formula

The definition of the short QT syndrome (SQTS) is based on QT duration, but thorough QT- and T-wave evaluation has not been performed to date. To evaluate the influence of QT rate-correction formulas in SQTS diagnosis, 12-lead electrocardiograms (ECGs) were recorded in 27 subjects from a single family with SQTS. Based on QT duration corrected by Bazett formula (QTc), 4 men were considered to have SQTS (QTc ≤340 ms), and 16 were classified to have “suspected” SQTS (QT ≤320 ms and/or QTc ≤380 ms). Holter ECGs were recorded in the 4 patients with SQTS, 8 with suspected SQTS, and 62 healthy volunteers. We evaluated QT duration at each RR interval and calculated individual α coefficient of the QT/RR relation. The QT interval duration at the mean Holter heart rate was corrected using an individual approach and 5 “universal” correction formulas (Bazett, Fridericia, Sagie-Framingham, Hodges, Rautaharju). Patients with SQTS and controls had lower α coefficients of the QT/RR relation when compared with Bazett and Fridericia formulas. The QT rate-dependence was lower in patients with SQTS (α 0.146 ± 0.070) when compared with control subjects (α 0.203 ± 0.039, p <0.05). The universal correction-formulas consistently provided higher values of corrected QT interval duration at the mean Holter heart rate than a subject-specific correction formula (p <0.05), which induced false negative diagnoses. In conclusion, the Bazett correction formula is not appropriate for making a diagnosis of SQTS. The subject-specific correction formula may provide a better cut-off value definition for the diagnosis of SQTS.