Background
The aim of this study was to test the effect of endurance training on the age-related changes of left ventricular (LV) twist-untwist mechanics. Aging has been shown to induce a decline of diastolic function and more recently an impairment of twist-untwist mechanics, which constitutes an important factor for early diastolic suction and filling. On the other hand, endurance training has been shown to improve cardiac function.
Methods
Speckle-tracking echocardiography was performed in 106 endurance-trained male athletes and 75 controls (age range 18–70 years), divided into three groups according to age.
Results
From the younger to older age groups, progressive increases in LV apical rotation and twist angle and a decrease in LV untwisting rate during isovolumic relaxation time were observed. Athletes had lower systolic twist angles ( P < .01) but higher untwist/twist ratios and LV untwisting rate during isovolumic relaxation time compared with controls, with the largest difference between senior groups (51 ± 24% vs 42 ± 22% in the young and 42 ± 29% vs 24 ± 25% in seniors, P < .001, respectively). The normal timing of untwisting rate occurring before radial displacement was preserved in athletes with increasing age, whereas it was blunted in controls.
Conclusions
Endurance training does not prevent but minimizes changes in LV twist-untwist mechanics from young subjects to seniors. Athletes showed smaller increases of twist angle with age and smaller declines of LV untwisting rate during isovolumic relaxation time and untwist/twist ratio compared with controls. This training-improved preservation of LV twist-untwist mechanics is likely to play a key role for systolic-diastolic coupling and diastolic filling, particularly during exercise.
The question of whether physical training can be considered a potent tool for delaying the physiologic aging process of the left ventricle is an ongoing debate. Normal aging induces marked changes in left ventricular (LV) diastolic function, whereas ejection fraction is generally well preserved. Moreover, recent studies have shown alterations of LV twist-untwist mechanics related to age. The systolic twist angle of the left ventricle stores a large part of the energy in elastic components, which is released during diastolic untwist. During isovolumic relaxation time (IVRT), untwist builds up an intraventricular pressure gradient, facilitating mitral valve opening, LV suction, and thus early diastolic filling. An increase in systolic twist angle, for example during exercise, normally induces an increase in diastolic untwisting rate, thus critically linking systole to diastole.
Studies in different age ranges have reported an increased resting twist angle, whereas early LV untwisting rate is decreased in seniors, indicating reduced systolic-diastolic coupling efficiency. Burns et al . showed that resting alterations in older individuals were associated with lower twisting rate and untwisting rate reserve during exercise echocardiography.
On the other hand, regular endurance training has been shown to positively affect LV diastolic parameters. A study based on standard and Doppler tissue imaging showed that age-associated LV relaxation abnormalities were not prevented by endurance training, whereas LV compliance was positively influenced by physical activity. Recent studies based on speckle-tracking echocardiography (STE) have also examined the impact of training on LV twist mechanics in a small number of athletes, showing lower LV twist angles and no effect or even an increase in this parameter with endurance training. These inconsistencies preclude any conclusion regarding twist mechanics in endurance-trained subjects. Furthermore, the effect of training on age-related changes in twist mechanics has not been evaluated, underlining the need for a study based on a large cohort of athletes of different age groups.
STE has high temporal resolution, enabling the evaluation of LV untwisting mechanics very early in diastole. The objective of the present study was to investigate LV twist-untwist mechanics in athletes aged 18 to 70 years, compared with age-matched sedentary controls. We hypothesized that endurance training would prevent or at least minimize the changes in twist-untwist mechanics from young subjects to seniors.
Methods
Ethics Approval and Study Population
Data from 106 male endurance-trained athletes (marathon and ultra trail runners, n = 28; triathletes, n = 37; and cyclists, n = 41) were recruited at various national and international sport competitions. Athletes aged 18 to 70 years performed exclusively aerobic training for ≥8 hours weekly for ≥5 years and were all in active training periods. Young, middle-aged, and senior athletes had performed for means of 8 ± 4, 13 ± 7, and 24 ± 12 years, respectively. They were compared with 75 healthy controls with no regular training habits, recruited via public notice boards. Exclusion criteria included historic or clinical evidence of cardiovascular disease, diabetes, arterial hypertension, dyslipidemia, metabolic syndrome, active cigarette smoking in the past 10 years, body mass index > 30 kg/m 2 , electrocardiographic changes suggestive of ischemic disease, conduction or rhythm abnormalities, and renal or pulmonary disease. Subjects of both groups were divided into three age groups: young (18–30 years), middle aged (31–45 years), and senior (>45 years) subjects. This study complied with the Declaration of Helsinki and received approval from the local ethics committee of Nîmes.
Echocardiography
Echocardiography was performed with the Vivid Q system (GE Vingmed Ultrasound AS, Horten, Norway), with a 3.5-MHz transducer. Cine loops were recorded in parasternal short-axis (basal, papillary muscle, and apical levels) and apical four-chamber views and saved for blinded offline analysis (EchoPAC version 6.0; GE Vingmed Ultrasound AS). Grayscale images were saved at a frame rate of 65 to 90 frames/sec and color tissue velocity images at a frame rate of 120 to 140 frames/sec. All measurements were averaged from three cardiac cycles.
Two-Dimensional Echocardiography and Doppler Tissue Imaging
M-mode measurements were obtained from the parasternal short-axis recorded at the papillary muscle level. LV mass was calculated according to the recommendations of the American Society of Echocardiography. Pulsed Doppler LV inflow and aortic flow were recorded, and stroke volume and cardiac output were calculated. The following time delays were measured from the onset of the QRS interval: to the onset of aortic flow (aortic valve opening), to the peak of aortic flow, to the end of aortic flow (aortic valve closure [AVC]), to the onset of mitral flow (mitral valve opening), and to peak of early filling (peak E). IVRT was calculated as mitral valve opening − AVC. Doppler tissue imaging velocities were assessed at the mitral annular level on the septal and lateral walls and averaged.
Speckle-Tracking Echocardiographic Analysis
Analysis of LV strains and twist-untwist parameters was conducted as previously described. LV rotation and rotational rate were assessed from short-axis views at the basal and apical levels. At the LV basal level, parasternal short-axis images were obtained with the cross-section as circular as possible from the standard parasternal position and with the tips of the mitral valve leaflets in the middle of the sector. At the LV apical level, the transducer was positioned one or two intercostal spaces more caudal (i.e., just proximal to the level with end-systolic LV luminal obliteration, as recommended by Van Dalen et al . ). Good tracking quality was obtained in 91% of apical segments and 88% of basal segments. Strain data were processed with a specific toolbox (Scilab version 4.1; Consortium Scilab, INRIA-ENPC, Paris, France). LV twist angle was calculated as the instantaneous difference between apical and basal rotation. Untwist describes the movement (recoil) of the left ventricle to its initial position, and untwisting rate represents the peak velocity of untwist in early diastole, expressed in degrees per second. The percentage of untwist during IVRT (%UT IVRT ) was calculated : %UT IVRT = (twist at AVC − twist at the end of IVRT)/twist at AVC × 100. The ratio of untwist to twist was calculated as peak untwisting velocity normalized for maximal twist to represent the presumed potential energy stored in the myocardium by systolic torsional deformation and released in diastole (i.e., systolic-diastolic coupling). To assess the dynamics of global LV twist mechanics and their relationship to radial displacement (reflecting volumetric changes of the left ventricle) throughout the cardiac cycle, twist–radial displacement loops were constructed.
Statistical Analysis
All values in the text and tables are expressed as mean ± SD. Analysis was performed using StatView version 5.0 (SAS Institute Inc, Cary, NC). Analysis of variance was used to compare each variable according to age and training status. Post hoc Bonferroni tests were used for comparisons between two age groups when appropriate. Linear regression analyses were performed to determine the relationships between age and parameters of diastolic functions. Statistical significance for all analyses was assumed at P < .05.
Results
Athletes had lower body mass compared with controls, whereas no differences were observed regarding body surface area or body mass index ( Table 1 ). There was no difference among subjects of different age groups concerning systolic blood pressure or heart rate, whereas diastolic blood pressure increased with advancing age. Athletes had lower systolic and diastolic blood pressures and lower heart rates compared with controls.
| Variable | Controls | Athletes | Statistical analysis ( P value) | |||||
|---|---|---|---|---|---|---|---|---|
| Young ( n = 30) | Middle-aged ( n = 19) | Seniors ( n = 26) | Young ( n = 25) | Middle-aged ( n = 46) | Seniors ( n = 35) | Age effect | Training effect | |
| Age (yrs) | 21 ± 3 | 38 ± 5 ‡|| | 56 ± 6 ‡|| | 23 ± 2 | 38 ± 5 ‡|| | 54 ± 7 ‡|| | <.001 | NS |
| Height (cm) | 178 ± 7 | 179 ± 7 | 175 ± 6 ∗§ | 178 ± 7 | 179 ± 7 | 175 ± 14 ∗§ | <.05 | NS |
| Body mass (kg) | 73.9 ± 19.4 | 75.7 ± 10.0 | 80.9 ± 22.4 | 71.1 ± 6.6 | 73.0 ± 6.5 | 73.7 ± 7.9 | NS | <.05 |
| Body mass index (kg/m 2 ) | 23.5 ± 6.5 | 23.6 ± 2.5 | 26.3 ± 0.2 †§ | 22.4 ± 1.5 | 22.5 ± 1.4 | 25.2 ± 8.6 †§ | <.05 | NS |
| Body surface area (m 2 ) | 1.91 ± 0.19 | 1.94 ± 0.15 | 1.95 ± 0.22 | 1.89 ± 0.12 | 1.92 ± 0.12 | 1.88 ± 0.15 | NS | NS |
| Systolic BP (mm Hg) | 131 ± 14 | 129 ± 10 | 128 ± 11 | 124 ± 11 | 123 ± 13 | 127 ± 11 | NS | <.05 |
| Diastolic BP (mm Hg) | 74 ± 11 | 83 ± 7 † | 82 ± 7 ‡ | 73 ± 12 | 75 ± 8 † | 80 ± 9 ‡ | <.001 | <.01 |
| Heart rate (beats/min) | 69 ± 12 | 69 ± 10 | 65 ± 10 | 59 ± 9 | 57 ± 9 | 56 ± 9 | NS | <.001 |
Standard Echocardiography
Data on morphologic parameters and systolic and diastolic data are presented in Table 2 . There was no difference among subjects of different age groups regarding LV morphologic parameters. S′ mean was similarly decreased from young subjects to seniors in both groups. Athletes had higher LV diameters, LV mass, and stroke volumes compared with controls. All diastolic parameters were affected by age, with decreases in peak E and peak E′ mean without a training effect on these parameters. In both groups, peak A and A′ mean progressively increased from young subjects to seniors, with lower values in endurance-trained subjects. Consequently, in all age groups, E/A and E′ mean /A′ mean ratios were higher in athletes. Significant differences among age ranges for peak E, peak A, and peak E′ in both groups are illustrated in Figure 1 .
| Variable | Controls | Athletes | Statistical analysis ( P value) | |||||
|---|---|---|---|---|---|---|---|---|
| Young ( n = 30) | Middle-aged ( n = 19) | Seniors ( n = 26) | Young ( n = 25) | Middle-aged ( n = 46) | Seniors ( n = 35) | Age effect | Training effect | |
| Morphologic parameters | ||||||||
| LV EDD (cm) | 5.0 ± 0.4 | 5.1 ± 0.5 | 5.0 ± 0.5 | 5.4 ± 0.5 | 5.4 ± 0.3 | 5.5 ± 0.4 | NS | <.001 |
| LV ESD (cm) | 3.0 ± 0.4 | 3.0 ± 0.3 | 2.9 ± 0.5 | 3.3 ± 0.5 | 3.1 ± 0.4 | 3.2 ± 0.5 | NS | <.001 |
| MWTd (cm) | 0.96 ± 0.16 | 1.06 ± 0.12 | 1.03 ± 0.17 | 1.10 ± 0.15 | 1.08 ± 0.4 | 1.05 ± 0.14 | NS | <.01 |
| LVMi (g/m 2.7 ) | 89 ± 20 | 106 ± 21 | 97 ± 24 | 123 ± 18 | 125 ± 26 | 129 ± 28 | NS | <.001 |
| Systolic function | ||||||||
| SVi (mL/m 2 ) | 40.4 ± 7.5 | 43.0 ± 9.5 | 41.4 ± 8.4 | 47.8 ± 9.4 | 50.3 ± 11.9 | 52.7 ± 14.0 | NS | <.001 |
| Qci (L/min/m 2 ) | 2.8 ± 0.7 | 2.9 ± 0.6 | 2.7 ± 0.6 | 2.8 ± 0.6 | 2.9 ± 0.8 | 2.9 ± 0.8 | NS | NS |
| DTI S′ mean (cm/sec) | 8.3 ± 1.2 | 7.6 ± 1.1 | 7.3 ± 1.6 ∗ | 7.9 ± 0.7 | 8.0 ± 1.3 | 7.5 ± 1.6 † | <.01 | NS |
| Diastolic function | ||||||||
| Peak E velocity (cm/sec) | 86 ± 15 | 80 ± 12 ∗ | 70 ± 15 †‡ | 79 ± 10 | 74 ± 15 ∗ | 71 ± 15 †‡ | <.001 | NS |
| Peak A velocity (cm/sec) | 53 ± 12 | 62 ± 10 ∗ | 66 ± 13 † | 46 ± 12 | 55 ± 13 ∗ | 64 ± 16 †§ | <.001 | <.01 |
| E/A ratio | 1.67 ± 0.38 | 1.31 ± 0.30 † | 1.09 ± 0.20 † | 1.83 ± 0.41 | 1.38 ± 0.29 † | 1.15 ± 0.29 †|| | <.001 | <.05 |
| DTI E′ mean (cm/sec) | 12.8 ± 1.8 | 10.2 ± 2.2 † | 7.9 ± 1.3 †|| | 12.4 ± 1.4 | 10.9 ± 1.6 † | 8.8 ± 1.9 †|| | <.001 | NS |
| DTI A′ mean (cm/sec) | 5.8 ± 1.4 | 7.5 ± 1.3 † | 8.4 ± 1.3 †|| | 5.2 ± 1.5 | 6.7 ± 1.5 † | 7.5 ± 1.3 †|| | <.001 | <.001 |
| DTI E′ mean /A′ mean ratio | 2.4 ± 0.89 | 1.45 ± 0.52 † | 0.97 ± 0.24 †|| | 2.63 ± 1.00 | 1.72 ± 0.49 † | 1.22 ± 0.34 †|| | <.001 | <.05 |
| SrLd (sec −1 ) | 1.76 ± 0.35 | 1.27 ± 0.24 † | 1.23 ± 0.27 †‡ | 1.58 ± 0.23 | 1.58 ± 0.31 † | 1.20 ± 0.29 †‡ | <.001 | NS |
| IVRT (msec) | 69 ± 19 | 71 ± 19 || | 76 ± 20 † | 63 ± 14 | 68 ± 19 || | 85 ± 22 † | <.001 | NS |
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