Ultra-marathon Runners Have The Biggest Hearts: Fact Or Fiction?

Abstract

Physiologic eccentric hypertrophy (left ventricular end-diastolic diameter [LVDd] ≥ 55mm) has been well documented in endurance-trained individuals. Traditionally, cycling, rowing and cross-country skiing have been associated with the "athlete heart syndrome." Nagashima et al. (2003) reported LVDd to be beyond normal limits in a considerable number of ultra-marathon runners (mean LVDd of 61mm), with 11% of those tested having LVDd greater than 70mm. PURPOSE: The purpose of this investigation was to assess whether ultra-marathon runners have physiological cardiac hypertrophy to the magnitude and prevalence that has been previously reported. METHODS: A total of 105 (26 female) ultra-marathon runners (Age = 43.3 ± 9.3 years (range 24-76 years)) underwent M-mode echocardiography to assess LVDd, interventricular septal thickness (IVS) and posterior wall thickness (PWT). LV mass (LVM) was calculated as: 0.8 (1.04(LVDd + IVS + PWT)3 -LVDd3) +0.6. Body surface area (BSA) was estimated (71.84 (height0.725)*(weight0.425))/10000), and LVM index (LVMI) was calculated as LVM/BSA1.5. All participants were recruited from the Western States Endurance Run (160km), or the Comrades Ultra-Marathon (89km). Participants with known cardiovascular disease or hypertension (systolic >140mmHg, diastolic >90mmHg) were excluded from the analyses. RESULTS: On average, the athletes ran 92.1 ± 32.1 km/week and had trained for 15.4 ± 10.2 yrs. The average resting heart rate was 58 ± 10 beats/minute, while systolic and diastolic blood pressures were 116 ± 10 and 76 ± 9 mmHg respectively. Mean fractional shortening was 40.2 ± 6.1 %, while LVDd was 51.4 ± 4.1mm (range: 42 to 61mm). LVDd exceeded the upper normal limits (≥ 55mm) in 27 (26%) athletes. Mean IVS was 10.3 ± 1.7mm (range: 6 to 14mm) and mean PWT was 9.4 ± 1.6mm (range: 6 to 13mm). Average LVM was 192.5 ± 42.2g (range: 105 to 320g), and LVMI was 76.6 ± 13.2g/m3 (range: 45 to 114g/m3). CONCLUSIONS: Our results suggest that although some (26%) ultra-marathon runners have evidence of eccentric hypertrophy, the frequency and magnitude of hypertrophy are not as great as previously reported. Importantly, only our highest LVDd was equivalent to the mean value reported previously in ultra-marathon runners.