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QT Corrections for Long QT Risk Assessment

Implications for the Preparticipation Examination

Hadley, David, PhD*; Hsu, David, BS; Pickham, David, PhD; Drezner, Jonathan A., MD§; Froelicher, Victor F., MD*,†

doi: 10.1097/JSM.0000000000000522
Original Research: PDF Only

Background: Because sudden cardiac death (SCD) in the young mainly occur in individuals with structurally normal hearts, improved screening techniques for detecting inherited arrhythmic diseases are needed. The QT interval is an important screening measurement; however, the criteria for detecting an abnormal QT interval are based on Bazett formula and older populations.

Objective: To define the normal upper limits for QT interval from the electrocardiograms (ECGs) of healthy young individuals, compare the major correction formula and propose new QT interval thresholds for detecting those at risk of SCD.

Methods: Young active individuals underwent ECGs as part of routine preparticipation physical examinations for competitive sports or community screening. This was a nonfunded study using de-identified data with no follow-up.

Results: There were 31 558 subjects: 2174 grade school (7%), 18 547 high school (59%), and 10 822 college (34%). Mean age was 17 (12-35 years), 45% were female, 67% white, and 11% of African descent. Bazett performed least favorably for removing the effect of heart rate (HR), whereas Fridericia performed the best. Fridericia correction also closely fit the raw data best (R2 of 0.65), and at percentile values applicable to screening. The recommended risk cut points using Bazetts correction identified less than half of the athletes in the 99th or 99.5th percentiles of the uncorrected QT by HR range. Use of Fridericia correction increased capture rates by over 50%.

Conclusion: Our results support the application of the Fridericia-corrected threshold of 460 for men and 470 milliseconds for women (and 485 milliseconds for marked prolongation) rather than Bazett correction for the preparticipation examination.

*Cardiac Insight Inc, Seattle, Washington;

Division of Cardiovascular Medicine, Stanford University School of Medicine, Stanford, California;

Division of General Medicine, Stanford University School of Medicine, Stanford, California; and

§Department of Family Medicine, University of Washington, Seattle, Washington.

Corresponding Author: David Hadley, 13720 220th PL NE, Woodinville, WA 98077 (dave_hadley@comcast.net).

None of the authors had a relationship with industry and financial associations within the past 2 years that might pose a conflict of interest in connection with the submitted article except for Drs. Hadley and Froelicher who are the developers of the software and hardware utilized to gather and analyze the ECG data and are part owners of the company that manufacturers and markets it as CardeaScreen.

Received March 23, 2017

Accepted August 03, 2017

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