The modern echocardiographic characterization of the athlete's heart, defined by the development of increased left ventricular (LV) diameter, mass and wall thickness in a highly trained athlete,¹ is based on data collected from a pooled analysis of athletes engaged in multiple sports. This primarily originates from European centers where mandated and comprehensive pre-participation cardiovascular screening programs exist. Basketball players, and athletes of similarly increased size, represent only a small fraction of the athletes included in these studies. A detailed understanding of expected cardiac remodeling in basketball players has significant clinical importance, particularly because basketball players have a higher incidence of sudden cardiac death (SCD) in the United States, compared with other athlete groups.^2,3 Cardiac conditions that pose a risk for SCD and are particularly relevant in the evaluation of basketball players include hypertrophic cardiomyopathy (HCM), as HCM is the most common cause of sports-related SCD in the U.S.,^4,5 and Marfan Syndrome, given the extreme height of the typical elite basketball player. Significant 'gray zones' exist in basketball players for the distinction between the upper limits of athletic cardiac remodeling and cardiac pathology that predisposes to SCD. The author of this Expert Analysis performed a detailed and systematic echocardiographic analysis of 526 professional basketball players in the National Basketball Association (NBA) to help address these issues and to provide health care providers with a frame of reference to help prevent cardiac emergencies in basketball players.

The mean (SD) age of the players in the NBA cohort was 25.7 (4.3) years; the mean height was 200.2 (8.8) cm and mean Body Surface Area (BSA) was 2.38 (0.19) m². Blood pressures (BP) were normal in the group (mean BP 119.2 (12.0)/72.8 (8.2) mm Hg). 77.2% of the athletes were African-American, 20.3% were Caucasian , 2.3% were Hispanic and <1% were Asian.

With respect to LV size, mean left ventricular end-diastolic diameter (LVEDD) in the NBA cohort ranged from 44 – 71 mm with a mean of 56.8 mm. The distribution of LVEDD in the cohort is shown in Figure 1A. LV cavity dilation, defined by the American Society of Echocardiography (ASE)⁶ as LVEDD > 59 mm, was present in 36.5% of the athletes. However, when LVEDD was indexed to BSA, LV cavity sizes in the NBA athletes were normal in comparison with normal reference adults, even amongst the largest athletes. In fact, we observed a proportional and approximately linear relationship between LVEDD and both height and BSA that extended to the uppermost biometrics of the group, demonstrated by the curves with 95% confidence intervals in Figures 1B and 1C. Left ventricular size was similar in African-American and Caucasian athletes. These results demonstrate that scaling LV size to body size is vitally important in the cardiac evaluation of basketball players.

Figure 1: Left Ventricular (LV) End-Diastolic Diameter (LVEDD) in National Basketball Association Athletes

Maximal left ventricular wall thickness (LVWT) ranged from 8 – 15 mm with mean LVWT of 11.0 mm. The distribution for LVWT in the cohort is shown in Figure 2A; Only 12.2% of the NBA players had LVWT between 13 - 15 mm and 2.5% of the players had LVWT 14 – 15 mm. As with LV size, the author of this Expert Analysis observed a proportional and approximately linear relationship between LV mass and both height and BSA that extended to the uppermost biometrics of the group, demonstrated by the curves with 95% confidence intervals in Figures 2B and 2C. 27.4% of the entire NBA cohort had LV hypertrophy (LVH) as defined by ASE standards (LV Mass Index > 115 g/m²).⁶ African-American athletes had increased LV wall thickness and mass in comparison with Caucasian athletes, and this author observed a difference in hypertrophy patterns between African-American and Caucasian athletes. The most predominant form of hypertrophy in African-American athletes was concentric LVH without cavity dilation, whereas the eccentricly dilated form of hypertrophy was most predominant in white athletes. These differences in hypertrophy patterns may be a reflection of genetic differences in LV adaptation to prolonged and intense exercise, and may underlie the well characterized differences in electrocardiographic patterns between African-American and Caucasian athletes across several sports.^7,8

Figure 2: Left Ventricular Wall Thickness (LVWT) and Mass (LVM) in National Basketball Association Athletes

The range for aortic root diameter in the NBA cohort was 25 – 42 mm with mean of 33.7 mm. The distribution of aortic root diameters in the NBA cohort is shown in Figure 3A. Just 4.6% of the NBA players had an aortic root diameter between 40 – 42 mm. In contrast to our findings demonstrating proportionality between body size and left ventricular size and mass, we observed that aortic root diameters tapered in their increase and reached a plateau at the uppermost biometrics, demonstrated by the curves with 95% confidence intervals in Figures 3B and 3C. Aortic root diameters were similar in African-American and Caucasian athletes. As there is no large-scale comparative data on aortic root dimensions in athletes of the size of a typical NBA player (mean height 200.2 cm, mean BSA 2.38 m²), these results have important implications for the cardiac evaluation of exceptionally tall and large athletes, and question the applicability of traditional formulas to estimate aortic root size that assume a linear relationship between aortic root diameter and BSA.^9,10

Figure 3: Aortic Root Diameters at the Sinuses of Valsalva in National Basketball Association Athletes

The author of this Expert Analysis measured LV function in the NBA cohort and found that LV ejections fractions (LVEF) were normal in the group (range 45 – 72%, mean 59.6 %) with just 0.9% of the group having mildly reduced LVEF between 45 – 49%. All ventricles were observed by stress echocardiography to augment normally with exercise, and no athlete was found to have LV diastolic dysfunction. Reports of athletes with low normal to mildly reduced LVEF are present in other elite athlete groups, such as professional football players and cyclists,^11,12 but no corroborating evidence has suggested that these individuals have an underlying cardiomyopathy. With serial echocardiographic evaluations of the NBA players with lower LVEF, we have found that LVEF has remained stable or increased over time.

The results of this study are the first to provide large-scale normative cardiac structural data for elite basketball players. The large contingent of NBA players forming our study represent an athlete group with more ethnic diversity and significantly greater anthropometry than any athletic group that has been studied on this scale. An overall important finding of this study was that some cardiac dimensions were proportional to body size, even amongst the largest athletes, and other cardiac dimensions, such as aortic root diameter, were not. Contained in Table 1 is a summary of important raw and indexed cardiac variables in the group. As highlighted by the American College of Cardiology Sports and Exercise Cardiology Think Tank,¹³ gaining an understanding of the actual cardiac structural data without having to extrapolate from data in other athlete groups is essential for reference for the healthcare professionals who treat the large number of basketball players from youth to the professional level. This data can hopefully help to focus decision making and improve clinical acumen for the purpose of primary prevention of cardiac emergencies in basketball players and in the athletic community at large.

Table 1: Summary of Raw and Indexed Cardiac Structural and Functional Data

Measure	African-American Athletes (n = 406)	Caucasian Athletes (n = 107)	p Value
LVEDD, mm, mean (95% CI) [Range, mm]	56.2 (55.8-56.6) [44-71]	59.2 (58.5-59.9) [51-67]	<0.001
LVEDD/BSA, mm/m2, mean (95% CI) [Range, mm/m2]	23.9 (23.7-24.1) [18.2-30.4]	24.1 (23.8-24.4) [20.8-30.0]	0.39
LVEDD/height, cm/m2, mean (95% CI) [Range, cm/m2]	1.58 (1.57-1.59) [1.25-1.97]	1.62 (1.60-1.64) [1.39-1.85]	0.001
LVESD, mm, mean (95% CI) [Range, mm]	37.3 (36.8-37.8) [25-50]	39.0 (38.2-39.8) [29-47]	<0.001
Maximum LVWT, mm, mean (95% CI) [Range, mm]	11.19 (11.07-11.31) [8-15]	10.48 (10.28-10.68) [8-13]	<0.001
LVMI, g/m2, mean (95% CI) [Range, g/m2]	106.3 (104.6-108.0) [61.79-164.18]	102.2 (99.0-105.4) [63.24-154.42]	0.029
RWT, mean (95% CI) [Range]	0.39 (0.38-0.40) [0.24-0.51]	0.35 (0.34-0.36) [0.24-0.48]	<0.001
LA Diameter, mm, mean (95% CI) [Range, mm]	37.7 (37.3-38.1) [26-45]	39.3 (38.6-40.0) [31-47]	<0.001
LAVI, mL/m2, mean (95% CI) [Range]	31.0 (30.4-31.6) [16.8-48.9]	30.5 (29.2-31.9) [16.8-51.1]	0.49
Aortic Root Diameter*,mm, mean (95% CI) [Range, mL/m2]	33.4 (33.1-33.7) [25-42]	35.1 (34.5-35.7) [26-42]	<0.001
Aortic Root*/BSA, mm/m2 (95% CI) [Range, mm/m2]	14.2 (14.0-14.4) [11.1-19.4]	14.3 (14.0-14.6) [11.1-17.5]	0.59
Aortic root*/height, mm/cm, mean (95% CI) [Range, mm/cm]	0.168 (0.167-0.169) [0.131-0.199]	0.171 (0.170-0.172) [0.133-0.207]	0.04
LV Ejection Fraction,%, mean (95% CI) [Range, %]	59.7 (59.3-60.1) [45-72]	59.4 (58.7-60.1) [51-71]	0.57
E/Aʂ , mean (95% CI) [Range]	2.0 (1.9-2.1) [0.9-4.8]	2.0 (1.9-2.1) [1.0-3.5]	0.41
E/E'μ , mean (95% CI) [Range]	4.9 (4.8-5.0) [2.5-8.7]	4.7 (4.5-4.9) [2.9-7.2]	0.34

References

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6. Lang RM, Badano LP, Mor-Avi V, et al. Recommendations for cardiac chamber quantification by echocardiography in adults: an update from the American Society of Echocardiography and the European Association of Cardiovascular Imaging. J Am Soc Echocardiogr 2015;28:1-39.
7. Drezner JA, Ackerman MJ, Anderson J, et al. Electrocardiographic interpretation in athletes: the 'Seattle Criteria'. Br J Sports Med 2013;47:122-4.
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9. Devereux RB, De Simone G, Arnett DK, et al. Normal limits in relation to age, body size and gender of two-dimensional echocardiographic aortic root dimensions in persons ≥15 years of age. Am J Cardiol 2012;110:1189-94.
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Keywords: Athletes, Basketball, Blood Pressure, Body Size, Body Surface Area, Cardiomyopathies, Cardiomyopathy, Hypertrophic, Death, Sudden, Cardiac, Diastole, Echocardiography, Echocardiography, Stress, Electrocardiography, Health Personnel, Hypertrophy, Left Ventricular, Marfan Syndrome, Mitral Valve, Primary Prevention, Sports

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