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By Michael H. Crawford, MD
SOURCE: Zorzi A, et al. Differential diagnosis between early repolarization of athlete's heart and coved-type Brugada electrocardiogram. Am J Cardiol 2015;115:529-532.
The normal variant ECG seen predominantly in highly trained athletes of domed ST segment elevation, and negative T waves in V1-V3 can be confused with some of the ECG patterns in Brugada syndrome patients. Clearly this distinction is of importance. Thus, these investigators from Italy compared the ECGs from 61 healthy endurance athletes who exhibited this normal variant of early repolarization with domed ST elevation and a negative T wave to 92 age- and sex-matched patients with Brugada syndrome and the type 1 ECG pattern of ≥ 2 mm of coved ST elevation, followed by a negative T wave in at least two contiguous leads between V1-V3. None of the subjects in either group had demonstrated structural heart disease. All were in sinus rhythm and were not taking drugs that affect the ECGs. All of the athletes had an uneventful, average 4-year follow-up. All the ECGs were digitally analyzed by two observers, with disagreements adjudicated by a third observer.
Results: Although the heart rate was significantly slower in the athletes (56 vs 73 bpm, P < 0.001) paradoxically, the PR interval was longer in the Brugada patients (181 vs 160 ms athletes, P = 0.04) and the QRS duration was longer (112 vs 91 ms athletes, P = 0.01). As expected, more athletes met criteria for left ventricular hypertrophy (Sokolow-Lyon index 36 vs 29 Brugada, P < 0.001). The QTc interval was normal and similar in both groups. Athletes had a lower ST segment height above the baseline at the J point (1.5 mm vs 3.3 mm Brugada P < 0.001) and a lower ST J point/ST at 80 ms after the J point ratio (0.8 vs 1.6 Brugada, P < 0.001). Only 3% of athletes had a ST J/ST80 ratio of > 1.0, whereas 100% of the Brugada patients did. Receiver operating curve analysis showed that an STJ/ST80 > 1.0 had a sensitivity of 97%, a specificity of 100%, and a diagnostic accuracy of 99% for detecting Brugada syndrome patients. The authors concluded that the STJ/ST 80 ratio is highly accurate for distinguishing the athlete’s heart from Brugada syndrome on the resting ECG and could be used to reduce the number of athletes who undergo further evaluation or are unnecessarily disqualified from competition.
Now that the European Society of Cardiology has recommended resting 12-lead ECGs be done in all athletes before competitive sports participation (not endorsed by ACC or AHA), we are seeing more athletes with “ECG abnormalities” referred to cardiologists in the United States and elsewhere. Early repolarization (J point elevation > 1 mm) in leads V1-V3 is seen in a majority of endurance athletes. However, in the typical pattern, J point and ST elevation are followed by a peaked and upright T wave. One series showed that 9% of highly trained athletes have a pattern with upward ST doming and T wave inversion that can resemble the type I Brugada pattern. It is stated that this pattern is more common in athletes of Afro-Caribbean origin, but the racial classification of the athletes in this study is not reported.
This large study with two selected groups validates the use of the STJ/ST80 ratio, according to the authors. In their multivariate analysis, STJ/ST80 ratio was superior to all the other ECG findings for distinguishing the two conditions. Of course, the selection of 61 athletes with this ECG pattern and 92 well-evaluated Brugada patients is a strength and weakness of the study. Selection bias always inflates the value of any discriminator between two groups. Only large all comers type studies in athletes will confirm the utility of the STJ/ST80 ratio. At this point, the authors suggest that an athlete with no family history of sudden collapse or death and a STJ/ST80 ratio < 1.0 does not need further tests for Brugada syndrome.