Echocardiographic (echo) and blood pressure (BP) reference values may help identify athletes at cardiovascular risk, yet benchmarks are inadequate for collegiate American-style football (ASF) players. Our purpose was to describe echo characteristics and BP values in collegiate ASF athletes compared with normal. First-year players (n = 80, age = 18 ± 1 years, height = 186 ± 7 cm, weight = 100.1 ± 22.0 kg, body mass index = 28.7 ± 5.0), body surface area [BSA] = 2.24 ± 0.25; percentage fat = 16.5 ± 9.7%) were measured for systolic and diastolic BP, and underwent echo procedures by a certified sonographer. Data analyses included simple statistics, Pearson r , frequencies in normal ranges, and t test; α = 0.05. Selected echo measurements (and indexed by BSA) were: left ventricular (LV) internal diameter diastole = 5.3 ± 0.5 cm (2.4 ± 0.3); left atrial diameter = 3.9 ± 0.5 cm (1.8 ± 0.2): LV end-diastolic volume = 138 ± 30 ml (62 ± 11); septal wall thickness = 1.0 ± 0.2 cm (0.5 ± 0.1); LV posterior wall thickness = 1.0 ± 0.1 cm (0.5 ± 0.1), LV mass = 212 ± 46 g (95 ± 18); and relative wall thickness = 0.39 ± 0.07. Correlations between BSA and echo variables were significant ( r = 0.26 to 0.50). Indexing by BSA reduced percentages above reference ranges from 36% to 7%. Septal wall thickness index was significantly greater in black (0.5 ± 0.1) than nonblack (0.4 ± 0.1) athletes. Fifty-nine athletes were hypertensive or prehypertensive, and diastolic BP was significantly greater in black (76 ± 10 mm Hg) compared with nonblack athletes (71 ± 8 mm Hg). ASF athletes demonstrated LV wall thicknesses and cavity sizes consistent with sport-training hypertrophy but which were unremarkable when indexed by BSA. Ethnicity generally did not influence echo variables. No ASF players were identified with cardiac dysfunction or disease.
Enlarged left ventricular (LV) mass, LV internal diameter, and LV wall thickness are commonly found in athlete’s hearts. Paradoxically, a greater left atrial (LA) diameter and LV mass predict cardiovascular disease (CVD) in the general population. Thus, differentiating benign adaptations from pathologic conditions is a major sports concern. In this regard, American-style football (ASF) athletes are an understudied sport group. National Football League (NFL) players show enlarged LV internal diameters and wall thicknesses consistent with concentric hypertrophy. Former NFL linemen compared to nonlinemen evidence larger LV dimensions and mass, which are correlated with elevated blood pressure (BP). In the single study published to date, first-year ASF players showed increased systolic BP, diastolic BP, and concentric hypertrophy over the competitive season. Our purpose was to describe the echocardiographic (echo) characteristics and frequency of elevated BP in first-year collegiate ASF athletes, and to compare with normal values where available. These data provide comparative benchmarks for screening incoming ASF athletes for cardiovascular risk.
Methods
Subjects were 80 freshmen and transfer ASF players enrolling in the university after at least 4 years of secondary school playing experience. Our study was approved by the Institutional Review Board for Research with Human Subjects, and informed consent was obtained from each athlete. Data were collected over a consecutive 3-year period as part of a required preparticipation physical examination, which included a medical history, height, weight (SECA model 700 scale; SECA North America Medical Measuring Systems and Scales, Benson Avenue, Chino, CA ), calculated body mass index, and body fat percentage by dual-energy x-ray absorptiometry (G.E. Lunar Prodigy; GE Health Care, Waukesha, WI). Heart rate, systolic BP and diastolic BP were obtained by experienced technicians with the athletes at supine rest for 5 minutes. Standard 2-dimensional and M-mode echo examinations were performed all 3 years by the same registered diagnostic cardiac sonographer according to the American Society of Echocardiography guidelines and procedures. Views obtained included the parasternal long axis, parasternal short axis, apical 4-chamber, and apical 5-chamber. Measurements were made offline by the sonographer from 2-dimensional echos, then reviewed and verified by the same cardiologist trained in ultrasound interpretation. Measured and calculated variables included body surface area (BSA), LV internal diameter diastole, LV internal diameter systole, LA diameter, aortic root diameter, LV end-diastolic volume, LV end-systolic volume, stroke volume, septal wall thickness, LV posterior wall thickness, LV mass, relative wall thickness, and ejection fraction. Data analyses included simple statistics and Pearson r calculated for selected variables of interest. Echo measurements were reported in raw values and relative to BSA, and compared to reference ranges where available; percentages of athletes above or below reference ranges were calculated. Differences between black (n = 36) and nonblack (n = 44) athletes were analyzed by unpaired t test, α = 0.05.
Results
Demographic and cardiovascular data at rest for our ASF athletes are displayed in Table 1 . Only diastolic BP was significantly (7%) higher in black compared with nonblack athletes. The average systolic BP for all athletes was above normal. Systolic and diastolic hypertension was present in 12% and 3% of the athletes, respectively; additionally, 64% (systolic) and 27% (diastolic) were prehypertensive by published standards. Nearly 78% were overweight or obese by body mass index, but only 28% were >20% body fat, indicating elevated body mass index was the result of greater lean rather than fat tissue.
| Variable | All (n=80) | Black (n=36) | Nonblack (n=44) | p -value |
|---|---|---|---|---|
| Age (yrs) | 18 ± 1 | 18 ± 1 | 18 ± 1 | 0.3664 |
| Height (cm) | 186 ± 7 | 185.4 ± 7.0 | 186.9 ± 7.0 | 0.3436 |
| Weight (kg) | 100.1 ± 22.0 | 98.6 ± 20.3 | 101.4 ± 23.4 | 0.5847 |
| Body mass index (kg/m 2 ) | 28.7 ± 5.0 | 28.5 ± 4.7 | 28.8 ± 5.4 | 0.8050 |
| Body fat (%) | 16.5 ± 9.7 | 14.7 ± 9.3 | 19.9 ± 9.9 | 0.0999 |
| Body Surface Area (m 2 ) | 2.24 ± 0.25 | 2.2 ± 0.2 | 2.3 ± .03 | 0.5176 |
| Heart Rate (bpm) | 70 ± 14 | 69 ± 13 | 70 ± 14 | 0.6857 |
| Systolic BP (mmHg) | 126 ± 10 | 128 ± 10 | 124 ± 10 | 0.1511 |
| Diastolic BP (mmHg) | 73 ± 9 | 76 ± 10 | 71 ± 8 | 0.0156 |
Echo variables are reported in Table 2 along with the percentages of athletes with values above or below published normal reference ranges. Data are collapsed across ethnicity because differences between black and nonblack players were significant only for stoke volume (black = 79.6 ± 18.0 ml and nonblack = 89.0 ± 19.5 ml) and septal wall thickness/BSA (black = 0.5 ± 0.1 and nonblack = 0.4 ± 0.1). The frequency of hypertrophy (LV mass >115 g m −2 ) was 18% in our athletes, and 29% showed relative wall thicknesses in excess of 0.42 suggesting concentric LV remodeling. Echo measurements generally correlated with height, weight, body mass index, and BSA (Pearson r values ranged from 0.222 to 0.505, p <0.05).
| Echo Variables & Units | Athlete Average | Reference Range | % Above Reference | % Below References | Athlete Range |
|---|---|---|---|---|---|
| LV internal diameter diastole | |||||
| cm | 5.3 ± 0.5 | 4.2-5.9 | 8.8 | 2.5 | 3.6-6.4 |
| cm∙m -2 | 2.4 ± 0.3 | 2.2-3.1 | 0 | 20 | 1.7-2.9 |
| LV internal diameter systole | |||||
| cm | 3.5 ± 0.5 | – | – | – | 1.5-4.5 |
| cm∙m -2 | 1.6 ± 0.2 | – | – | – | 0.7-2.1 |
| LA diameter | |||||
| cm | 3.9 ± 0.5 | 3-4 | 49.4 | 5.1 | 2.9-4.8 |
| cm∙m -2 | 1.8 ± 0.2 | 1.5-2.3 | 1.3 | 12.7 | 1.2-2.3 |
| Aortic root diameter | |||||
| cm | 3.0 ± 0.3 | 2.1-4.3 | 0 | 0 | 2.4-4.1 |
| cm∙m -2 | 1.4 ± 0.2 | – | – | – | 1.0-1.8 |
| Aortic root index | |||||
| cm∙m -2 | 0.9 ± 0.1 | – | – | – | 0.7-1.2 |
| LV end diastolic volume | |||||
| ml | 138.0 ± 29.6 | 67-155 | 28.8 | 2.5 | 54-209 |
| ml∙m -2 | 62.0 ± 11.3 | 35-75 | 10.1 | 1.3 | 31-85 |
| LV end systolic volume | |||||
| ml | 54.5 ± 14.6 | 22-58 | 40.5 | 0 | 23-91 |
| ml∙m -2 | 24.3 ± 6.3 | 12-30 | 17.7 | 2.5 | 11-42 |
| Stroke volume | |||||
| ml | 84.7 ± 19.3 | – | – | – | 39-136 |
| ml∙m -2 | 37.83 ± 7.7 | – | – | – | 18-54 |
| Septal wall thickness | |||||
| cm | 1.0 ± 0.2 | 0.6-1.0 | 45.0 | 0 | 0.6-1.3 |
| cm∙m -2 | 0.5 ± 0.1 | – | – | – | 0.3-0.7 |
| LV posterior wall thickness | |||||
| cm | 1.0 ± 0.1 | 0.6-1.0 | 51.3 | 0 | 0.7-1.3 |
| cm∙m -2 | 0.5 ± 0.1 | – | – | – | 0.3-0.6 |
| LV mass | |||||
| g | 211.9 ± 45.8 | 88-224 | 40.0 | 0 | 115.0-329.7 |
| g∙m -2 | 94.5 ± 17.7 | 49-115 | 17.5 | 0 | 52.7-131.5 |
| Relative wall thickness | 0.39 ± 0.07 | 0.24-0.42 | 28.8 | 0 | 0.26-0.65 |
| Ejection fraction % | 60.9 ± 6.6 | ≥55 | 84.8 | 15.2 | 41.7-75.3 |
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