Association between left ventricular structure and cardiac performance during effort in two morphological forms of athlete’s heart

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Abstract

Aim: The aim of the study was to evaluate in 263 competitive athletes possible correlations between changes induced by different sport activities in left ventricular (LV) structure and cardiac response during maximal physical effort. Methods: A total of 160 top-level endurance athletes (ATE; swimmers, runners; 28±4 years; 98 male) and 103 strength-trained athletes (ATS; weight-lifters, body-builders; 27±5 years; male), selected on the basis of training protocol (dynamic vs. static exercise), underwent standard Doppler echocardiography, heart rate variability analysis and maximal exercise stress test by bicycle ergometry. M- and B-mode echocardiographic LV measurements were determined at rest, while the following functional indexes were assessed during effort: maximal heart rate (HR), maximal systolic blood pressure (SBP) and maximal workload (Watts reached by bicycle test). Results: The two groups were comparable for age and sex, but ATS at rest showed higher HR, SBP, and body surface area (BSA). By echo analysis, LV mass index and ejection fraction did not significantly differ between the two groups. However, ATS showed increased sum of wall thickness (septum+posterior wall), relative wall thickness and LV end-systolic stress, while LV stroke volume and LV end-diastolic diameter (P<0.01) were greater in ATE. HR variability analysis underlined in ATE increased indexes of vagal tone (P<0.01). During maximal physical effort, ATE showed a better functional capacity, with greater maximal workload (P<0.001) reached with lower maximal HR and SBP. After adjusting for HR, age, sex, BSA and SBP, distinct multiple linear regression models evidenced in ATE independent associations of maximal effort workload with LV end-diastolic diameter (P<0.001), HR (P<0.001) at rest and LV end-systolic stress (P<0.01) were found in ATE. On the other hand, independent direct correlation of SBP max during effort with sum of wall thickness (P<0.001), BSA (P<0.05) and LV end-systolic stress (P<0.001) was evidenced in ATS. Conclusions: LV structural changes in competitive athletes represent adaptation to hemodynamic overload induced by training and are consistent with different kinds of sport activity. Work capacity during exercise is positively influenced by preload increase in ATE, while increased afterload due to isometric training in ATS determines higher systemic resistance during physical effort.

Introduction

Athlete’s heart is a left ventricular (LV) adaptation to long-term, intensive training which includes changes such as increased cavity diameter, wall thickness and LV mass [1], [2], [3], [4], [5], produced to a degree consistent with sport activity and exercise programs. Standard Doppler echocardiography has been widely used to identify athlete’s heart and to distinguish it from LV pathologies [1], [2], [3], [4], [5], [6], [7], [8]. Morganroth et al. [1] were the first to postulate that two different morphological forms of athlete’s heart can be distinguished: a strength-trained and an endurance-trained heart. A recent large meta-analysis on this topic confirmed how endurance- and strength-training may determine either extreme volume or pressure load, thus explaining the athlete’s increase in LV internal dimension and/or wall thickness [6].

Even though the morphology of the athlete’s heart and the effects of different sports have been recently investigated by several authors [4], [5], [6], few data are presently available about the possible impact of LV structure at rest on cardiac performance during physical effort [9], [10], [11], [12].

On these grounds, the present study was designed to investigate in 263 competitive athletes the possible association between changes induced by different sport activities on LV structure and cardiac response during maximal physical effort. This issue may be critical to better understand the mechanisms underlying LV supernormal systolic and diastolic function observed in athletes at rest as well as during effort [9], [10], [11], [12].

Section snippets

Study population

After the approval of the Institutional Ethics Committee, 160 top-level endurance-trained athletes (ATE; long distance swimmers, runners) and 103 competitive strength-trained athletes (ATS; weight-lifters, body-builders), both having evidence of left ventricular hypertrophy (LVH) (LV mass index >50 g/m2.7 according to the Cornell criteria [13]), were included into the study after their informed consent was obtained.

Training protocols

All the subjects had been training intensively for 15–20 h/week for >4 years.

Clinical characteristics of the study population

As expected, ATS at rest showed higher HR, BSA and systolic BP than ATE (Table 1).

Standard Doppler echocardiographic analysis

LV mass index and fractional shortening did not significantly differ between the two groups (Table 2). However, ATS showed increased sum of wall thickness (septum+LV posterior wall), LV ESSc and relative wall thickness, while LV stroke volume and LV end-diastolic diameter were greater in ATE. All transmitral Doppler indexes were higher in ATE, with increased E/A ratio.

Reproducibility of echocardiographic measurements

Interobserver variability was ±2.6% for septal

Discussion

This study emphasizes the association existing between LV structure at rest and cardiac performance during physical effort in athletes undergoing different long-term intensive training protocols. Our findings suggest that, in the absence of differences in LVMI, (i) ATE achieved greater maximal workload with lower rate-pressure product than ATS; (ii) ATS showed higher values of SBP both at rest and during physical effort; (iii) ATE showed by heart rate variability analysis higher parasympathetic

Acknowledgements

This research is supported by Ph. Doctorate in Medical-Surgical Physiopathology of Cardiopulmonary and Respiratory System and Associated Biotechnologies–SUN. The authors are indebted to Mrs. Anna Gaglione for excellent nursing and technical support during the study protocol.

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