DouglasP.Zipes, MD, MACC, Chair MichaelJ.Ackerman, MD, PHD, FACC ,N.A. MarkEstesIII, MD, FACC, Augustus O. Grant, MB, CHB, PHD, FACC, Robert J. Myerburg, MD, FACC, George Van Hare, MD, FACC

Inherited arrhythmia syndromes

LONG QT SYNDROME

The definitive clinical diagnosis of congenital long QT syndrome (LQTS) can be complex (20). Debate continues as to what QTc constitutes the upper limit of normal. An increasing proportion of asymptomatic individuals with genetically proven LQTS are found to have a normal resting ECG with a heart rate corrected QT interval (QTc) by Bazett's formula of less than 460ms (genotype positive/phenotype negative LQTS). In addition, a QTc of 440ms, used in the past as an upper limit of normal, is present in far too many normal individuals (greaterthan25%) to serve as a meaningful upper limit cut-off value. In general, a QTc of 470ms or more in males and 480ms or more in females requires further investigation as to the presence of congenital (or acquired) causes of QT prolongation. A patient with LQTS and a resting QTc of 500ms or more is generally considered at increased clinical risk for a significant arrhythmia (21). One approach to the diagnosis of congenital LQTS is to utilize the "Priori-Schwartz" score that incorporates QTc, T-wave morphology, symptomatic presentation, and family history into the diagnostic algorithm (21). A "Priori-Schwartz" score of 4 or more suggests high clinical probability for LQTS. In addition, genetic testing for the five cardiac ion-channel genes responsible for 75% of LQTS (LQT1, LQT2, LQT3, LQT5, and LQT6) is now available as a commercial diagnostic test (22). Mutations involving the structural protein ankyrin-B underlie the rare LQT 4 form (23). Mutations involving the KCNJ2-encoded IK1 potassium channel account for approximately one-half of Andersen-Tawil syndrome (ATS1) characterized by abnormal U waves, a prolonged QU interval, periodic paralysis, and facial and skeletal dysmorphisms. The ATS1 has been annotated in the past as LQT7. Physical exertion (particularly swimming) appears to be a common trigger for ventricular arrhythmias in LQT1, where as individuals with LQT2 seem more at-risk to auditory/emotional triggers, and patients with LQT3 may be at greater risk during rest and in activity (24, 25). However, exceptions to these genotype-phenotype correlations hinder genotype-specific tailoring of competitive sports recommendations. The entire personal and family phenotype must be incorporated before any eligibility or disqualification decision is rendered.

Recommendations:

1. Regardless of QTc or underlying genotype, all competitive sports, except those in class IA category should be restricted in a patient who has previously experienced either: 1) an out-of-hospital cardiac arrest, or 2) a suspected LQTS-precipitated syncopal episode.
2. Asymptomatic patients with baseline QT prolongation (QTc of 470ms or more in males, 480ms or more in females) should be restricted to class IA sports. The restriction limiting participation to class IA activities may be liberalized for the asymptomatic patient with genetically proven type 3 LQTS (LQT3).
3. Patients with genotype-positive/phenotype-negative LQTS (i.e., identification of a LQTS-associated mutation in an asymptomatic individual with a nondiagnostic QTc) may be allowed to participate in competitive sports. Although the risk of sudden cardiac death is not zero in such individuals, there is no compelling data available to justify precluding these individuals (who are being identified with increasing frequency) from competitive activities. Because of the strong association between swimming and LQT1, persons with genotype-positive/phenotype-negative LQT1 should refrain from competitive swimming.
4. LQTS patients with an ICD/pacemaker should not engage in sports with a danger of bodily collision because such trauma may damage the pacemaker system. The presence of an ICD should restrict individuals to class IA activities.

You can read the full text of the 36th Bethesda Conference--which contains sections on screening, use of AEDs, and other cardiac conditions like Brugada syndrome, CPVT, HCM, etc.--on the ACC website: http://www.acc.org/qualityandscience/clinical/statements.htm. Look towards the bottom of the page at the section titled "March 5, 2005 Competitive Athletes With Cardiovascular Abnormalities: Eligibility Recommendations for: Bethesda Conference 36"