Published Online
on August 24, 2009

A more recent version of this article appeared on October 1, 2009

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Original Article

Exercise-Induced ECG Changes in Brugada Syndrome

Ahmad S. Amin; Elisabeth A.A. de Groot; Jan M. Ruijter; Arthur A.M. Wilde and Hanno L. Tan¹

Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands

^* Corresponding author; email: h.l.tan{at}amc.uva.nl

Background—Ventricular arrhythmia occurrence during exercise is reported in Brugada syndrome (BrS). Accordingly, experimental studies suggest that BrS-linked SCN5A mutations reduce sodium current more at fast heart rates. Yet, the effects of exercise on the BrS ECG phenotype have not been studied. We aimed to assess ECG responses to exercise in BrS and determine whether these responses are affected by the presence of an SCN5A mutation.

Methods and Results—ECGs at baseline, at peak exercise and during recovery were analyzed from 35 control males (controls), 25 BrS males without SCN5A mutation (BrS_SCN5A-), and 25 BrS males with SCN5A mutation (BrS_SCN5A+; 15 with missense mutation and 10 with mutation leading to premature truncation of the protein). No differences existed in clinical phenotype between BrS groups. At baseline, BrS_SCN5A- and BrS_SCN5A+ patients had lower heart rates, wider QRS, shorter QTc, and higher peak J-point amplitudes than controls; BrS_SCN5A+ patients also had longer PR than BrS_SCN5A- and controls. Exercise resulted in PR shortening in all groups, more QRS widening in BrS_SCN5A+ than in BrS_SCN5A- and controls, and less QT shortening in BrS_SCN5A- and BrS_SCN5A+ than in controls. The latter resulted in QTc shortening in controls, but QTc prolongation in BrS_SCN5A- and BrS_SCN5A+. Finally, the increase in peak J-point amplitude during exercise was similar in all three groups, but resulted in a coved-type pattern only in BrS_SCN5A- and BrS_SCN5A+.

Conclusions—Exercise aggravated the ECG phenotype in BrS. The presence of an SCN5A mutation was associated with further conduction slowing at fast heart rates. Possible mechanisms that may explain the observed ECG changes are discussed.

Key Words: arrhythmia • exercise • tachycardia • Brugada syndrome • SCN5A • mutation • ECG