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. 2011 Aug;8(8):1207-13.
doi: 10.1016/j.hrthm.2011.03.009. Epub 2011 Mar 10.

Genotype-specific QT correction for heart rate and the risk of life-threatening cardiac events in adolescents with congenital long-QT syndrome

Alon Barsheshet  1 , Derick R Peterson, Arthur J Moss, Peter J Schwartz, Elizabeth S Kaufman, Scott McNitt, Slava Polonsky, Jonathan Buber, Wojciech Zareba, Jennifer L Robinson, Michael J Ackerman, Jesaia Benhorin, Jeffrey A Towbin, G Michael Vincent, Li Zhang, Ilan Goldenberg
Affiliations

Genotype-specific QT correction for heart rate and the risk of life-threatening cardiac events in adolescents with congenital long-QT syndrome

Alon Barsheshet et al. Heart Rhythm. 2011 Aug.

Abstract

Background: A prolonged QT interval corrected for heart rate (QTc) is a major risk factor in patients with long QT syndrome (LQTS). However, heart rate-related risk in this genetic disorder differs among genotypes.

Objective: This study hypothesized that risk assessment in LQTS patients should incorporate genotype-specific QT correction for heart rate.

Methods: The independent contribution of 4 repolarization measures (the absolute QT interval, and Bazett's, Fridericia's, and Framingham's correction formulas) to the risk of aborted cardiac arrest or sudden cardiac death during adolescence, before and after further adjustment for the RR interval, was assessed in 727 LQTS type 1 and 582 LQTS type 2 patients. Improved QT/RR correction was calculated using a Cox model, dividing the coefficient on log(RR) by that on log(QT).

Results: Multivariate analysis demonstrated that in LQTS type 1 patients 100-ms increments in the absolute QT interval were associated with a 3.3-fold increase in the risk of life-threatening cardiac events (P = .020), and 100-ms decrements in the RR interval were associated with a further 1.9-fold increase in the risk (P = .007), whereas in LQTS type 2 patients, resting heart rate was not a significant risk factor (hazard ratio 1.11; P = .51; P value for heart rate × genotype interaction = .036). Accordingly, analysis of an improved QT correction formula showed that patients with the LQTS type 1 genotype required a greater degree of QT correction for heart rate (improved QTc = QT/RR⁰·⁸) than LQTS type 2 patients (improved QTc = QT/RR⁰·²).

Conclusion: Our findings suggest that risk stratification for life-threatening cardiac events in LQTS patients can be improved by incorporating genotype-specific QT correction for heart rate.

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Figures

Figure 1
Figure 1
Distribution of the QT and RR intervals among LQT1 patients (panels A and B) and among LQT2 patients (panels C and D).
See this image and copyright information in PMC

References

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