Short QTc interval in males with klinefelter syndrome-influence of CAG repeat length, body composition, and testosterone replacement therapy.

BACKGROUND: Klinefelter syndrome (KS) is a sex chromosomal aneuploidy (47,XXY) affecting 1/660 males. Based on findings in Turner syndrome, we hypothesized that electrocardiogram (ECG) abnormalities would be present in males with KS.
OBJECTIVE: To investigate ECGs in males with KS and compare with controls.
METHODS: Case control study of 62 males with KS and 62 healthy males matched on age. The primary outcome parameter was a difference in the ECG presentation between the two groups. The ECGs were analyzed by one blinded examiner (intraobserver variability 0.2-2.1%). The QT-interval was measured using "teach-the-tangent" method excluding the U-wave. QTc was calculated using Bazett's equation, Hodges' equation, and a linear regression model. Body mass index, abdominal fat, and muscle mass as well as sex hormone levels were secondary parameters. The prevalence of mutations in genes related to short QT syndrome was determined in participants with a QTc < 330 ms.
RESULTS: Compared to controls, the QTc-interval was shorter (P = 0.02-0.06) in males with KS depending on the applied correction method. QTc was shortest among testosterone (T)-treated males with KS, while untreated and thus hypogonadal KS had QTc interval comparable to controls. No mutations in genes related to short QT syndrome were found.
CONCLUSION: We found short QTc interval in males with KS, with further shortening of the QTc interval by T. These results suggest that genes on the X chromosome could be involved in regulation of the QTc interval and that T treatment may aggravate this mechanism. ©2015 Wiley Periodicals, Inc.