CLINICAL RESEARCH
New upper limit of physiologic cardiac hypertrophy in Japanese participants in the 100-km ultramarathon
Junzo Nagashima, MD* ,*,
Haruki Musha, MD ,
Hideomi Takada, MD* and
Masahiro Murayama, MD*
* Internal Medicine Section, Yokohama Sports Medical Center, Yokohama, Japan
Division of Cardiology, Department of Internal Medicine, St. Marianna University School of Medicine, Kawasaki, Japan
Division of Cardiology, St. Marianna University School of Medicine, Yokohama City Seibu Hospital, Yokohama, Japan
Manuscript received March 1, 2003;
revised manuscript received May 27, 2003,
accepted June 9, 2003.
* Reprint requests and correspondence: Dr. Junzo Nagashima, Internal Medicine Section, Yokohama Sports Medical Center, Yokohama International Stadium, 3302-5, Kodukue-cho, Kouhoku-ku, Yokohama, 222-0036, Japan.
junzo-n{at}zb3.so-net.ne.jp
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Abstract
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OBJECTIVES: The goal of our study was to define the structural characteristics of the heart in Japanese 100-km ultramarathon runners.
BACKGROUND: During screening of participants in a 100-km ultramarathon, we found some participants who had larger cardiac chambers than had ever been previously reported.
METHODS: A total of 291 male participants in a 100-km ultramarathon age from 20 to 73 years were examined using echocardiography.
RESULTS: The mean heart rate (HR) was 50.6 ± 5.6 beats/min (38 to 79 beats/min), the systolic blood pressure (SBP) was 110.5 ± 5.6 mm Hg (94 to 138 mm Hg), the diastolic blood pressure (DBP) was 65.9 ± 6.6 mm Hg (58 to 90 mm Hg), the left ventricular end-diastolic diameter (Dd) was 61.8 ± 6.9 mm (42 to 75 mm), the left ventricular end-systolic diameter (Ds) was 39.6 ± 6.0 mm (23.0 to 55.0 mm), the interventricular septal thickness (IVS) was 10.2 ± 1.9 mm (5 to 19 mm), the posterior wall thickness (PW) was 10.0 ± 1.4 mm (5 to 15 mm), the aortic diameter (Ao) was 38.5 ± 4.0 mm (27 to 50 mm), the left atrial diameter (LA) was 40.2 ± 4.8 mm (26 to 49 mm), and the systolic wall stress (WS) was 221.5 ± 52.9 kdyne/cm2 (108.0 to 537.6 kdyne/cm2). Significant predictors of these parameters were the monthly running distance for HR, SBP, DBP, Dd, Ds, Ao, LA, and WS, as well as the age for IVS, PW, and Ao.
CONCLUSIONS: Thirty-three participants had a Dd larger than 70 mm. Moreover, some athletes had a larger aorta and left atrium than had ever been previously reported. The oldest runner was 73 years old.
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Abbreviations and Acronyms
| | Ao | = aortic diameter | | DBP | = diastolic blood pressure | | Dd | = left ventricular end-diastolic diameter | | Ds | = left ventricular end-systolic diameter | | HR | = heart rate | | IVS | = interventricular septal thickness | | LA | = left atrial diameter | | PW | = posterior wall thickness | | SBP | = systolic blood pressure | | WS | = systolic wall stress |
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To our knowledge, the biggest left ventricular end-diastolic diameter (Dd) previously reported was 70 mm in a cyclist (1,2), the biggest left atrial (LA) diameter was 45 mm in a rower (2,3), and the biggest aortic diameter (Ao) was 39 mm also found in a rower (2,3). In our study, we describe the characteristics of the hearts of Japanese 100-km ultramarathon runners, some of whom have larger hearts than had ever been previously reported.
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Methods
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Subjects.
The subjects were 291 healthy men age from 20 to 73 years (mean age: 41.8 ± 9.7 years) who participated in and ran the entire 100-km ultramarathon at Lake Saroma from 1995 to 1997. Subjects were excluded if they had hypertension (systolic blood pressure [SBP] above 140 mm Hg or diastolic blood pressure [DBP] above 90 mm Hg) or a positive reply to the revised Physical Activity Readiness Questionnaire (PAR-Q) (4). Written, informed consent to this study was obtained from all of the subjects. Approval of the study was also obtained from the Research Ethics Committee of St. Marianna University School of Medicine.
Clinical parameters.
We sent questionnaires to each participant about their monthly running distance in order to assess the intensity of their training. Body surface area was calculated after measuring the weight and height of each subject. Heart rate (HR) was determined by limb-lead electrocardiography combined with echocardiography, while SBP and DBP were measured using a mercury sphygmomanometer.
Recording and analysis of echocardiograms.
Echocardiography was performed on the day before the 100-km ultramarathon. To record echocardiograms, EUB-565 and HDI-3000 (Hitachi Co., Tokyo, Japan) were used. Conventional M-mode echocardiograms of the left ventricle, aorta, and left atrium were recorded at a paper speed of 50 mm/s via the parasternal approach after obtaining long-axis cross-sectional echocardiograms. A representative cross-sectional echocardiogram is shown in Figure 1. A digital measurement of the HR was done five times and the mean value was calculated. Using these recordings, Dd, left ventricular end-systolic diameter (Ds), interventricular septal thickness (IVS), posterior wall thickness (PW), Ao, and left atrial diameter (LA) were measured. Then systolic wall stress (WS) was calculated using the thick-walled spherical model [WS = Ds[ · ]SBP/(IVS + PW)] (5).
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Figure 1 A representative echocardiography recording. EF = ejection fraction; FS = fractional shortening; IVS = interventricular septal thickness; LV = left ventricular; LVD = left ventricular end-diastolic diameter; LVPW = left ventricular posterior wall thickness; RVD = right ventricular end-diastolic diameter.
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Statistical analysis.
All data are represented as the mean ± SD. Simple and multiple regression analysis were done using HR, SBP, DBP, Dd, Ds, IVS, PW, Ao, LA, and WS as dependent variables versus the age, the monthly running distance, and body surface area as independent variables. A value of p < 0.0001 was considered statistically significant. The computer used for the statistical analysis was an Apple Macintosh (Apple Computer, Inc., Tokyo, Japan), and the software program was Stat View 5.0J (SAS Institute, Inc., Cary, North Carolina).
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Results
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Clinical parameters.
The mean monthly running distance was 408.7 ± 206.1 km (0 to 920 km), while body surface area was 1.66 ± 0.1 m2 (1.36 to 2.05 m2) (2), HR was 50.6 ± 5.6 beats/min (38 to 79 beats/min), SBP was 110.5 ± 5.6 mm Hg (94 to 138 mm Hg), and DBP was 65.9 ± 6.6 mm Hg (58 to 90 mm Hg).
Echocardiographic findings.
The mean values of the parameters were as follows: 61.8 ± 6.9 mm (42 to 75 mm) for Dd, 39.6 ± 6.0 mm (23.0 to 55.0 mm) for Ds, 10.2 ± 1.9 mm (5 to 19 mm) for IVS, 10.0 ± 1.4 mm (5 to 15 mm) for PW, 38.5 ± 4.0 mm (27 to 50 mm) for Ao, and 40.2 ± 4.8 mm (26 to 49 mm) for LA. The mean WS was 221.5 ± 52.9 kdyne/cm2 (108.0 to 537.6 kdyne/cm2). The largest examples of cardiac and Ao are shown in Figures 2A to 2C.
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Figure 2 M-mode echocardiography in 100-km ultramarathon runners. (A) A 44-year-old man. The left ventricular end-diastolic diameter is 75 mm. (B) A 48-year-old man. The aortic diameter (Ao) is 50 mm. (C) A 37-year-old man. The left atrial diameter (LA) is 49 mm. LV = left ventricle; RVOT = right ventricular outflow tract.
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Simple regression analysis showed that the monthly running distance was a significant predictor of HR (r = –0.559, p < 0.0001, Fig. 3), SBP (r = –0.273, p < 0.0001, Fig. 4), DBP (r = –0.361, p < 0.0001, Fig. 4), Dd (r = 0.727, p < 0.0001, Fig. 5), Ds (r = 0.580, p < 0.0001, Fig. 5), Ao (r = 0.267, p < 0.0001, Fig. 6), LA (r = 0.286, p < 0.0001, Fig. 6), and WS (r = 0.401, p < 0.0001, Fig. 3). In addition, age was a significant predictor of IVS (r = 0.250, p < 0.0001, Fig. 7), PW (r = 0.238, p < 0.0001, Fig. 7), and Ao (r = 0.267, p < 0.0001, Fig. 6).
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Figure 3 Correlation of heart rate (HR) and systolic wall stress (WS) with age, body surface area (BSA), and monthly running distance.
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Figure 4 Correlation of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with the age, body surface area (BSA), and monthly running distance.
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Figure 5 Correlation of left ventricular end-diastolic diameter (Dd) and left ventricular end-systolic diameter (Ds) with age, body surface area (BSA), and monthly running distance.
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Figure 6 Correlation of aortic diameter (Ao) and left atrial diameter (LA) with age, body surface area (BSA), and monthly running distance.
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Figure 7 Correlation of interventricular septal thickness (IVS) and posterior wall thickness (PW) with the age, body surface area (BSA), and monthly running distance.
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In multiple regression analysis, both the age (ß = 0.303, p < 0.0001) and the monthly running distance (ß = 0.288, p < 0.0001) were significant predictors of Ao.
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Discussion
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Thirty-three participants had a Dd larger than 70 mm. The first possible reason for the detection of larger cardiac dimensions in the present study may be the age distribution of our subjects. Most previous studies of elite athletes have been confined to subjects in their 20s or younger. Our subjects had a mean age of 41.8 ± 9.7 years and ranged from 20 to 73 years, including many retired elite competitive marathon runners. We found that age was a significant predictor of Ao, IVS, and PW, but not of the other parameters. Thus, the older age of our subjects may partly support the above assumption.
Regarding our present findings, the second possible reason may be a racial difference including genetic influences. In this study, body surface area was not a positive predictor of any of the echocardiographic parameters, while the monthly running distance was a significant positive predictor of Dd, Ds, Ao, and LA. Recently, Pelliccia et al. (3) reported that elite athletes showed a positive correlation of body surface area with Dd, but their subjects were involved in sports with a wide variation of intensity, and this point differs from the subjects of our study. In many previous studies on the athlete's heart, the subjects were all Caucasians (1–3), while our subjects were all Japanese men. Recently, we reported about genetic influences on the heart in Japanese ultramarathon runners (6) and on myocardial injury after running an ultramarathon (7,8). It is possible that genetic characteristics combined with repeated myocardial injury may be related to the formation of athlete's heart. Compared with the subjects of previous reports, the body surface area of our subjects was significantly smaller (1–3), so a larger cardiac load per unit of body size may have been related to our findings.
The third possible reason for the present results may be differences in sampling and the number of subjects. Many previous reports about the normal upper limit of the athlete’s heart have been general assessments of multiple classical sports (1–3). Some of the reports focused only on over full marathon runners have mainly assessed cardiac fatigue or cardiac responsiveness to intensive exercise, and the number of subjects was small (9,10). Thus, limiting our athletes to 100-km runners and the larger number of subjects may have contributed to our present findings.
Study limitations.
An important issue related to this study is that the present findings may be pathological and not a physiological phenomenon. We only performed M-mode echocardiography guided by conventional two-dimensional echocardiograms and did not use color Doppler echocardiography because of the limited time available for examination. Thus, the evidence of physiological changes in these subjects is only their running 100 km within the time limit of 14 h and giving negative replies to the PAR-Q. In the future, a longitudinal follow-up study including Doppler echocardiography should be performed to assess pathological findings.
Conclusions.
Many Japanese ultramarathon runners had larger cardiac chambers and aortic root diameters than previously reported. Their age, intensity of training, and racial difference, as well as the sample size, may have led to these findings. Many elderly participants ran the entire 100-km, and the oldest runner was 73 years old.
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References
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Abstract
Methods