Key result
24-hour Holter QTa/RR slope analysis differentiated LQT2 from LQT1 patients with an area under the curve of 0.804 (95% CI 0.68-0.93).
Why the study?
Clinical course and therapeutic strategies in congenital LQTS are genotype-specific, but accurate genotype estimation is often difficult from standard 12-lead ECG.
Does 24-hour Holter monitoring QT/RR slope analysis improve differential diagnosis between LQT1 and LQT2 in patients with congenital long QT syndrome?
Cross-Sectional (n=54)
Yes
Does 24-hour Holter monitoring QT/RR slope analysis improve differential diagnosis between LQT1 and LQT2 in patients with congenital long QT syndrome?
Effect estimate: AUC 0.804 (95% CI 0.68-0.93)
Absolute Event Rate: 0.233% vs 0.181%
p-value: p=0.0002
Continuous 24-hour QT/RR analysis using Holter monitoring, specifically the QTa/RR slope, is a useful noninvasive tool to differentiate between LQT1 and LQT2 genotypes.
May aid noninvasive LQT1/LQT2 differentiation on Holter; hypothesis-generating and requires prospective validation.
BACKGROUND: The clinical course and therapeutic strategies in the congenital long QT syndrome (LQTS) are genotype-specific. However, accurate estimation of LQTS genotype is often difficult from the standard 12-lead ECG. OBJECTIVES: This study aims to evaluate the utility of QT/RR slope analysis by the 24-hour Holter monitoring for differential diagnosis of LQTS genotype between LQT1 and LQT2. METHODS: This cross-sectional study enrolled 54 genetically identified LQTS patients (29 LQT1 and 25 LQT2) recruited from three medical institutions. The QT-apex (QTa) interval and the QT-end (QTe) interval at each 15-second were plotted against the RR intervals, and the linear regression (QTa/RR and QTe/RR slopes, respectively) was calculated from the entire 24-hour and separately during the day or night-time periods of the Holter recordings. RESULTS: The QTe/RR and QTa/RR slopes at the entire 24-hour were significantly steeper in LQT2 compared to those in LQT1 patients (0.262 ± 0.063 vs. 0.204 ± 0.055, p = .0007; 0.233 ± 0.052 vs. 0.181 ± 0.040, p = .0002, respectively). The QTe interval was significantly longer, and QTe/RR and QTa/RR slopes at daytime were significantly steeper in LQT2 than in LQT1 patients. The receiver operating curve analysis revealed that the QTa/RR slope of 0.211 at the entire 24-hour Holter was the best cutoff value for differential diagnosis between LQT1 and LQT2 (sensitivity: 80.0%, specificity: 75.0%, and area under curve: 0.804 [95%CI = 0.68-0.93]). CONCLUSION: The continuous 24-hour QT/RR analysis using the Holter monitoring may be useful to predict the genotype of congenital LQTS, particularly for LQT1 and LQT2.
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Yodogawa et al. (2021) conducted a cross-sectional in Congenital long QT syndrome (LQTS) (n=54). LQT2 genotype vs. LQT1 genotype was evaluated on QTa/RR slope at the entire 24-hour (AUC 0.804, 95% CI 0.68-0.93, p=0.0002). 24-hour Holter QTa/RR slope analysis differentiated LQT2 from LQT1 patients with an area under the curve of 0.804 (95% CI 0.68-0.93).
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