Open AccessQT correction using Bazett’s formula remains preferable in long QT syndrome type 1 and 2
Author(s) -
Dahlberg Pia,
Diamant UllaBritt,
Gilljam Thomas,
Rydberg Annika,
Bergfeldt Lennart
Publication year - 2021
Publication title -
annals of noninvasive electrocardiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.494
H-Index - 48
eISSN - 1542-474X
pISSN - 1082-720X
DOI - 10.1111/anec.12804
Subject(s) - medicine , concordance , qt interval , long qt syndrome , cardiology , framingham risk score , heart rate , kappa , framingham heart study , pediatrics , blood pressure , disease , linguistics , philosophy
Background The heart rate (HR) corrected QT interval (QTc) is crucial for diagnosis and risk stratification in the long QT syndrome (LQTS). Although its use has been questioned in some contexts, Bazett's formula has been applied in most diagnostic and prognostic studies in LQTS patients. However, studies on which formula eliminates the inverse relation between QT and HR are lacking in LQTS patients. We therefore determined which QT correction formula is most appropriate in LQTS patients including the effect of beta blocker therapy and an evaluation of the agreement of the formulae when applying specific QTc limits for diagnostic and prognostic purposes. Methods Automated measurements from routine 12‐lead ECGs from 200 genetically confirmed LQTS patients from two Swedish regions were included (167 LQT1, 33 LQT2). QT correction was performed using the Bazett, Framingham, Fridericia, and Hodges formulae. Linear regression was used to compare the formulae in all patients, and before and after the initiation of beta blocking therapy in a subgroup ( n = 44). Concordance analysis was performed for QTc ≥ 480 ms (diagnosis) and ≥500 ms (prognosis). Results The median age was 32 years (range 0.1–78), 123 (62%) were female and 52 (26%) were children ≤16 years. Bazett's formula was the only method resulting in a QTc without relation with HR. Initiation of beta blocking therapy did not alter the result. Concordance analyses showed clinically significant differences (Cohen's kappa 0.629–0.469) for diagnosis and prognosis in individual patients. Conclusion Bazett's formula remains preferable for diagnosis and prognosis in LQT1 and 2 patients.