ECG Quiz Answer
ECG Variations in College Athletes
John D. Cantwell, MD; Allen L. Dollar, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 27 - NO. 9 - SEPTEMBER 1999
Limited echocardiography (4), done on all freshman athletes, revealed mild-to-moderate left ventricular enlargement. His left ventricular end-diastolic dimension (LVEDd) was 60 mm (upper normal for the nonathletic population is 54 mm) and his left ventricular end-systolic dimension (LVESd) was 47 mm (upper normal is 40 mm). His interventricular septum measured 12 mm (normal range, 7 to 12 mm), and the posterior left ventricular wall measured 11 mm (upper normal, 12 mm). His left ventricular ejection fraction was normal at 55%. He was cleared for competition.
Patient 2. The ECG of the 17-year-old football player (figure 5) also indicated marked LVH, prominent septal Q waves, and repolarization variations in the midprecordial leads.
The limited echocardiogram showed that all LV dimensions were in the normal range: LVEDd, 51 mm; LVESd, 30 mm; interventricular septal thickness, 11 mm; and left ventricular posterior wall thickness, 10 mm. His left ventricular ejection fraction was normal at 65%. He was cleared for competition.
Patient 3. The ECG of the 19-year-old basketball player (figure 6) reflects LVH and inferior and anterolateral repolarization variations.
His limited echocardiogram revealed a normal LVEDd of 51 mm and a normal LVESd of 32 mm. The interventricular septum was mildly thickened at 15 mm, as was the left ventricular posterior wall at 13 mm. The septal-to-posterior wall ratio was normal at less than 1.3. The LV ejection fraction was 70%. Overall, the findings were normal for a competitive athlete. He was cleared for play and had an excellent season, with no untoward events or symptoms.
Resting ECGs in athletes can vary widely and can suggest LVH, septal hypertrophy, and repolarization variations. This can occur, as in patient 2 (figure 5), without signs of left ventricular or septal hypertrophy on the echocardiogram, the "gold standard" for measuring ventricular dimensions. ECG variations in normal athletes can include repolarization changes, QRS width of 0.10 to 0.12 s, Wenckebach AV heart block, AV dissociation, early repolarization, QS in right precordial leads, prominent R-wave voltage, sinus bradycardia and sinus pauses, accelerated idioventricular rhythm, and U-wave prominence.
The resting ECG doesn't necessarily correlate with body size. Competitive athletes vary greatly in size, some being as large as a young polar bear (figure 7) (5). Voltage is not always greater in larger people. Athletes who have relatively thin chests and little body fat are likely to have greater QRS voltage than larger athletes. For example, in the 6 ft 8 in., 365-lb athlete shown in figure 7, QRS voltage was normal (figure 8)—considerably less than the voltage of patient 2 (figure 5) who weighed 200 lb less.
The correlation between various measurements of ECG voltage and LVH as measured by echocardiography or necropsy has been evaluated by several authors (6-10). ECG voltage measurements in the general population are fairly specific but insensitive for the detection of LVH. One of the more sensitive ECG voltage measurements involves the summation of the total QRS voltage in each of the 12 leads of the ECG (11). Dollar and Roberts (12) found that a total 12-lead QRS amplitude of more than 175 mm reflects LVH in nonathletes. This correlation, however, did not hold up in the athletic patients described here. As can be seen in figure 6, dramatically increased QRS voltage will sometimes occur in competitive athletes who have no or minimal LVH. The total QRS amplitude in figure 5, an athlete with normal echocardiographic dimensions, exceeded 300 mm. We base our final clearance decision on the history and physical findings and ECG, supplemented by the limited echocardiogram.
We have found that limited echocardiograms are a useful and relatively inexpensive way ($40 per test) to more accurately determine the presence of LVH. The test is done on all freshman athletes at Georgia Tech. The limited echocardiogram is done without placing electrode leads, which saves time and is less expensive. A two-dimensional parasternal long axis view examines the left ventricle, the intraventricular septal and posterior LV walls, the aortic root, and the left atrial diameter. Color Doppler ultrasound, performed in the same view, visualizes the aortic and mitral valves. With Doppler turned off, a two-dimensional short-axis sweep of the aorta base and LV apex is performed.
When interpreting limited echocardiography results in athletes, physicians should keep in mind that the normal measurements for athletes can be higher than for the general population. For example, a study of 738 male and 209 female elite athletes found that the LVEDd ranged from 40 to 66 mm (mean 52) (13). (The normal range in nonathletes is 36 to 54 mm.) In 38% of the athletes, the value exceeded 54 mm, the upper limit of normal for a nonathletic population.
The yield in limited echocardiography might be more favorable if reserved for athletes who have any of the following: (1) a heart murmur greater than grade 2/6 intensity, (2) a murmur that intensifies with Valsalva's maneuver or with standing, (3) any diastolic murmur, or (4) an ECG that resembles figures 4 through 6 (ie, marked LVH, septal hypertrophy, and repolarization variations).
Dr Cantwell and Dr Dollar are cardiologists at Cardiology of Georgia, PC, in Atlanta. Dr Cantwell is a clinical professor of medicine at Morehouse School of Medicine, in Atlanta, an editorial board member of The Physician and Sportsmedicine, and the cardiovascular consultant to the Georgia Tech Athletic Department. Address correspondence to John D. Cantwell, MD, Cardiology of Georgia, PC, 95 Collier Rd NW, Suite 2075, Atlanta, GA 30309.