Previous studies have compared cardiac morphology between strength and endurance athletes, but few studies have examined predictors of valvular regurgitation in this population. This study evaluated predictors of mitral regurgitation (MR) in high school and collegiate athletes. Athletes in 9 different sports (n = 144) underwent transthoracic echocardiography. We used 97 sedentary patients as controls. Left ventricular (LV) end-diastolic diameter, septal wall thickness, posterior wall thickness, relative wall thickness (RWT), LV mass, LV volume, and mass/volume ratio were calculated and indexed for body surface area. Valvular regurgitation was graded from 0 to 4. Using logistic regression, RWT was associated with decreased odds of MR, with each 0.07 increase in RWT accounting for a 0.52 decrease in odds of MR (95% confidence interval 0.32 to 0.85, p = 0.009). Differences were best exemplified by comparison of soccer and football players, who represent predominantly aerobic versus predominantly isometric exercise, respectively. Soccer players had a larger LV end-diastolic index (29.2 ± 3 vs 24.9 ± 2.6, p <0.001), lesser RWT (0.33 ± 0.06 vs 0.38 ± 0.08, p = 0.014), and lower mass/volume ratio (1.04 ± 0.21 vs 1.29 ± 0.3, p <0.001), with a greater prevalence of MR (45.8% vs 8.5%). Sedentary subjects were similar to football players in LV volume and soccer players in LV mass. In conclusion, RWT is a negative predictor of MR, with higher values reducing the odds of MR. MR appears to be related to the relation between wall thickness and chamber size rather than chamber size alone.
Sports medical examination for high school and collegiate athletes includes a detailed history and a physical examination, in which it is not uncommon to discover heart murmurs by cardiac auscultation. Current American College of Cardiology and American Heart Association guidelines suggest further workup with echocardiography for systolic murmurs of grade >2, systolic murmurs of grade <2 with the presence of signs or symptoms, and any diastolic murmur. Echocardiography is the standard imaging method for evaluating precordial murmurs and is often performed to rule out structural heart disease, most importantly hypertrophic obstructive cardiomyopathy. The prevalence of hypertrophic obstructive cardiomyopathy in young athletes is well documented, as is the prevalence of valvular regurgitation, but few have documented predictors of valvular regurgitation. Furthermore, studies of athlete’s heart that often compare cardiac morphology between strength and endurance athletes rarely describe predictors of valvular regurgitation in this population. This study examines the prevalence of mitral regurgitation (MR) in different athletic populations and in sedentary subjects and the predictors of MR in a population of high school and collegiate athletes, with no evidence or a history of cardiovascular disease.
Methods
A total of 144 high school and collegiate athletes were evaluated medically in a voluntary screening program performed at their local sports facility. All athletes were cleared for sports participation by their family physicians. Consent for the echocardiographic evaluation was provided by the subjects and their parents. Analysis of the anonymized research database from the clinical data was approved by the Temple University School of Medicine Institutional Review Board. The student’s age, gender, body mass index, current level of education, and type of sport were recorded, and students completed a health questionnaire. Details of the physical examination were not available. Additionally, a random population of 97 sedentary subjects who had received an outpatient transthoracic echocardiography and were without an evidence of structural heart disease were selected as controls.
A MyLab 30 Cardiovascular Ultrasound Unit (Esaote, Indianapolis, Indiana) with a 2.5 mHz phased array transducer was used for the ultrasound examinations. Two-dimensional M-mode echocardiography, color flow Doppler, and spectral flow Doppler were performed on each patient. The echocardiographic protocol included routine parasternal long- and short-axis views and an apical 4-chamber view for assessment of left ventricular (LV) and right ventricular dimensions and function and Doppler interrogation of the heart valves. Severity of valvular regurgitation was assessed as mild, mild to moderate, moderate, or severe by visual assessment (1+ to 4+) based on the distance of the regurgitant jet from the corresponding valve and its relative jet area/left atrial ratio area according to published recommendations. Using M-mode echocardiography, LV end-diastolic diameter (LVIDd), ventricular septal wall thickness (VS), and posterior wall thickness (PW) were calculated. Each of these dimensions was also indexed for body surface area. Relative wall thickness (RWT) was calculated by the equation (VS + PW)/LVIDd. LV mass was calculated using the formula 0.8 × (1.04 [(LVIDd + PW + VS) − (LVIDd) ]) + 0.6. LV volume was calculated using the method of Fortuin et al. All echocardiographic studies were evaluated by a core laboratory at the Temple University Hospital by level III trained and echocardiographic board certified cardiologists.
Mean and SD were determined for continuous data, and frequency statistics were determined for noncontinuous data. Analysis of variance was used to determine significant differences between sedentary subjects, football, and soccer players. Binary logistic regression using a forward conditional method was used to determine predictors of MR. Statistical analysis was performed using IBM SPSS v20 (Chicago, Illinois).
Results
Demographic information is listed in Table 1 . There were a total of 144 high school and collegiate athletes included in the study and 97 sedentary age-matched controls. Ages of athletes ranged from 13 to 38 years with a mean age of 20.2 years. Participants were predominantly men, and there were more collegiate athletes than high school athletes. Football was the most heavily represented sport in the study, followed by soccer and basketball.
| Variable | Athletes (%) | Control (%) |
|---|---|---|
| Age (yrs) | 20.21 ± 3.02 | 25.2 ± 4.09 |
| BSA (m 2 ) | 2.03 ± 0.29 | 1.98 ± 0.31 |
| Gender | ||
| Men | 114 (79.2) | 61 (62.9) |
| Women | 30 (20.8) | 36 (37.1) |
| Enrollment | ||
| High school | 24 (16.7) | — |
| College | 120 (83.3) | — |
| Sport ∗ | ||
| Basketball | 16 (11.1) | — |
| Bowling | 6 (4.2) | — |
| Cheerleading | 2 (1.4) | — |
| Cross country | 2 (1.4) | — |
| Football | 71 (49.3) | — |
| Soccer | 24 (16.7) | — |
| Tennis | 6 (4.2) | — |
| Track and field | 12 (8.3) | — |
| Volleyball | 2 (1.4) | — |
Prevalence of valvular regurgitation is listed in Table 2 . No stenotic valves were identified in the study subjects. Most athletes were found to have mild tricuspid regurgitation (TR). There were no patients in the study with severe TR. Similarly, most mitral valvular regurgitation was classified as mild, with a small proportion of patients with mild to moderate and moderate MR. No athletes were found to have severe MR. There were very few athletes who were found to have aortic regurgitation (AR).
| Variable | Athletes (%) | Controls (%) |
|---|---|---|
| TR | ||
| 1+ | 51 (35.4) | 16 (16.5) |
| 2+ | 21 (14.6) | 1 (1) |
| 3+ | 7 (4.9) | 0 |
| MR | ||
| 1+ | 16 (11.1) | 8 (8.2) |
| 2+ | 9 (6.3) | 0 |
| 3+ | 3 (2.1) | 0 |
| AR | ||
| 1+ | 3 (2.1) | 0 |
| 2+ | 1 (0.7) | 0 |
| 3+ | 0 | 0 |
| Multivalvular lesions | ||
| MR + TR | 18 (12.5) | 3 (3.1) |
| MR + AR | 2 (1.4) | 0 |
| TR + AR | 2 (1.4) | 0 |
| MR + TR + AR | 1 (0.7) | 0 |
A comparison between the prevalence of MR in soccer players, football players, and male controls can be seen in Figure 1 . Excluding volleyball, cheerleading, and cross country, each with only 2 subjects, soccer players had the greatest prevalence of MR and football players had the least. Because there was only 1 female soccer player and no female football players, we compared these 2 sports with the male controls. Football players had a slightly less prevalence of MR than the male controls (8.5% vs 9.8%), and soccer players had a much greater prevalence of MR (45.8%) than either group. Table 3 lists between-group differences of soccer players, football players, and sedentary controls. Football players had a larger body mass index, body surface area, LVIDd, VS, PW, RWT, LV mass, LV volume, and mass/volume ratio. When indexed for body surface area, mean PW and VS were not statistically different between soccer players and football players. LV end-diastolic index and LV volume index were greater in the soccer players.
| Variable | Soccer | Football | Control | p ∗ |
|---|---|---|---|---|
| Body mass index (kg/m 2 ) | 21.0 ± 2.8 | 30.2 ± 5.9 | 28.5 ± 7.5 | <0.001 |
| Body surface area (m 2 ) | 1.79 ± 0.19 | 2.20 ± 0.24 | 2.07 ± 0.28 | <0.001 |
| LVIDd (mm) | 51.9 ± 4.8 | 54.5 ± 5.2 | 50.7 ± 4.9 | <0.001 |
| LV end-systolic diameter (mm) | 34.3 ± 4.5 | 36.1 ± 3.9 | 32.1 ± 4.1 | <0.001 |
| Ventricular septal width (mm) | 8.6 ± 1.5 | 10.1 ± 1.9 | 9.3 ± 1.3 | <0.001 |
| PW (mm) | 8.4 ± 1.4 | 10.1 ± 1.7 | 9.3 ± 1.2 | <0.001 |
| LV end-diastolic index (mm·m −2 ) † | 29.2 ± 3.0 | 24.9 ± 2.6 | 24.9 ± 3.3 | <0.001 |
| Posterior wall index (mm·m −2 ) ‡ | 4.7 ± 0.7 | 4.6 ± 0.7 | 4.6 ± 0.8 | 0.854 |
| Ventricular septal index (mm·m −2 ) § | 4.9 ± 0.9 | 4.6 ± 0.9 | 4.5 ± 0.8 | 0.335 |
| RWT ¶ | 0.33 ± 0.06 | 0.38 ± 0.08 | 0.37 ± 0.06 | 0.018 |
| LV mass (g) | 158.8 ± 38.9 | 215.1 ± 55.6 | 171.1 ± 40.2 | <0.001 |
| LV mass index (g/m 2 ) ‖ | 88.3 ± 17.6 | 97.3 ± 20.2 | 82.9 ± 16.2 | <0.001 |
| LV volume (ml) | 154.6 ± 28.0 | 168.3 ± 30.7 | 146.2 ± 29.1 | <0.001 |
| LV volume index (ml/m 2 ) ∗∗ | 86.2 ± 13.3 | 76.7 ± 12.2 | 71.3 ± 13.9 | <0.001 |
| Mass/volume ratio (g/ml) | 1.04 ± 0.21 | 1.29 ± 0.30 | 1.18 ± 0.22 | <0.001 |
∗ Calculated by analysis of variance.
† LVIDd divided by body surface area.
‡ PW divided by body surface area.
§ Interventricular septal width divided by body surface area.
‖ LV mass divided by body surface area.
Binary logistic regression analysis compared the presence or absence of MR. We evaluated the effect of end-diastolic and end-systolic dimensions, VS and PW, and the RWT on MR. VS and RWT correlated with degree of MR. RWT was shown to be a statistically significant negative predictor of MR. Each 0.07 increase (1 SD) in this ratio decreases the odds of MR by a factor of 0.52 (95% confidence interval 0.31 to 0.85, p = 0.009) or about 50%. Figure 1 also shows the relation between MR incidence and RWT in soccer players, football players, and sedentary men.
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