European Heart Journal Advance Access originally published online on April 14, 2008
European Heart Journal 2008 29(9):1210-1211; doi:10.1093/eurheartj/ehn147
Prevalence and significance of an isolated long QT interval in elite athletes
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France
Concerning the prevalence and significance of an isolated long QT syndrome in elite athletes, Basavarajaiah et al.1 concluded that a QTc value of 
500 ms is diagnostic of long QT syndrome (LQTS), considering these athletes with QTc 500 ms (three of seven patients) having a high probability of LQTS.2,3
We have some remarks regarding their definition of LQTS, the accuracy of Schwartz score,2 used in this work and the place of ethnic differences on definition of QTc interval.
LQTS is a genuine channelopathy and mutations in potassium-channel genes KCNQ1 (LQT1 locus) and KCNH2 (LQT2 locus) and the sodium-channel gene SCN5A (LQT3 locus) are the most common causes, occurring in 60–75% of all cases.4
Among their three patients with QTc 500 ms and high probability of LQTS by Schwartz score, 2 (66%) had negative genetic testing and the only positive (athlete no. 3) had QTc shorter than two others (respectively, QTc interval 515 vs. 550 and 570 ms). This fact suggests that the correlation between the length of QTc interval and the gene mutation should be taken with precaution, furthermore in the literature the so-called ‘normal QTc’ LQTS has been reported in 
5% of LQTS gene carriers with QTc values <440 ms.5
Athlete no. 3, positive for LQT1 had negative exercise treadmill test (ETT) despite affected first-degree family members, whereas the two others with QTc >500 ms but without LQTS (as genetic test was negative) had positive ETT and one of them had not affected first-degree family members (athlete no. 2).
Two out of four athletes, with QTc < 500 ms, declined genetic testing. This lack of information (50%) does not allow us to use this cut off value of QTc interval for genetic screening of potential high-risk population for sudden death, as elite athletes with an isolated long QT as recommended by the authors.
What is the age distribution and duration of physical activity of all seven athletes? Knowing that they were asymptomatic although two had positive ETT.
The current cut off value of a prolonged QTc interval (>440 ms in males and >460 ms in females) does not take into account the possible race specificity of phenotype–genotype correlation. This fact would be an explanation of missed diagnoses of black Africans,6 who represent a large cohort of elite athletes worldwide.
All these conflicting data show the difficulties in finding a high diagnostic yield and an accuracy of phenotype feature of LQTS, keeping in mind that the gold standard for diagnosis is genetic testing. Moreover, the authors studied a small number of patients to have consistent data.
In our point of view, the significance of an isolated long QT interval remains unknown, and we need to study the long-term outcome of this phenotype in elite athletes.
References
- Basavarajaiah S, Wilson M, Whyte G, Shah A, Behr E, Sharma S. Prevalence and significance of an isolated long QT interval in elite athletes. Eur Heart J (2007) 28:2944–2949.
[Abstract/Free Full Text] - Schwartz PJ, Moss AJ, Vincent GM, Crampton RS. Diagnostic criteria for the long QT syndrome. An update. Circulation (1993) 88:782–784.
[Free Full Text] - Swan H, Viitasalo M, Piippo K, Laitinen P, Kontula K, Toivonen L. Sinus node function and ventricular repolarisation during exercise stress test in long QT syndrome patients with KvLQT1 and HERG potassium channel defects. J Am Coll Cardiol (1999) 34:823–829.
[Abstract/Free Full Text] - Lehnart SE, Ackerman MJ, Benson DW Jr, Brugada R, Clancy CE, Donahue JK, George AL Jr, Grant AO, Groft SC, January CT, Lathrop DA, Lederer WJ, Makielski JC, Mohler PJ, Moss A, Nerbonne JM, Olson TM, Przywara DA, Towbin JA, Wang LH, Marks AR. Inherited arrhythmias: a National Heart, Lung, and Blood Institute and Office of Rare Diseases workshop consensus report about the diagnosis, phenotyping, molecular mechanisms, and therapeutic approaches for primary cardiomyopathies of gene mutations affecting ion channel function. Circulation (2007) 116:2325–2345.
[Abstract/Free Full Text] - Schwartz PJ. The long QT syndrome. In: Sudden Death—Kulbertus HE, Wellens HJJ, eds. (1980) The Hague: Martinus Nijhoff. 358–378.
- Heradien M, Goosen A, Moolman-Smook JC, Brink PA. Race and gender representation of hypertrophic cardiomyopathy or long QT syndrome cases in a South African research setting. Cardiovasc J Africa (2007) 18:312–315.
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