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 <or=340 ms), and 16 were classified to have "suspected" SQTS (QT <or=320 ms and/or QTc <or=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 alpha 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 alpha coefficients of the QT/RR relation when compared with Bazett and Fridericia formulas. The QT rate-dependence was lower in patients with SQTS (alpha 0.146 +/- 0.070) when compared with control subjects (alpha 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.
Extramiana
Fabrice
F
Lariboisière University Hospital, Paris 7 University, APHP, Paris, France. fabrice.extramiana@lrb.aphp.fr
Maury
Philippe
P
Maison-Blanche
Pierre
P
Duparc
Alexandre
A
Delay
Marc
M
Leenhardt
Antoine
A
D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001919:Bradycardia / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D003937:Diagnosis, Differential; D004562:Electrocardiography / Q000379:methods*; D005190:Family; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008962:Models, Theoretical; D010375:Pedigree; D011379:Prognosis