Evidence of region-specific right ventricular functional adaptation in endurance-trained men in response to an acute volume infusion

NEW FINDINGS

What is the central question of this study? Endurance athletes demonstrate altered regional right ventricular (RV) wall mechanics, characterized by lower basal deformation, in comparison to non-athletic control subjects at rest. We hypothesized that regional adaptations at the RV base reflect an enhanced functional reserve capacity in response to haemodynamic volume loading. What is the main finding and its importance? Free wall RV longitudinal strain is elevated in response to acute volume loading in both endurance athletes and control subjects. However, the RV basal segment longitudinal strain response to acute volume infusion is greater in endurance athletes. Our findings suggest that training-induced cardiac remodelling might involve region-specific adaptation in the RV functional response to volume manipulation.

ABSTRACT

Eccentric remodelling of the right ventricle (RV) in response to increased blood volume and repetitive haemodynamic load during endurance exercise is well established. Structural remodelling is accompanied by decreased deformation at the base of the RV free wall, which might reflect an enhanced functional reserve capacity in response to haemodynamic perturbation. Therefore, in this study we examined the impact of acute blood volume expansion on RV wall mechanics in 16 young endurance-trained men (aged 24 ± 3 years) and 13 non-athletic male control subjects (aged 27 ± 5 years). Conventional echocardiographic parameters and the longitudinal strain and strain rate were quantified at the basal and apical levels of the RV free wall. Measurements were obtained at rest and after 7 ml/kg i.v. Gelofusine infusion, with and without a passive leg raise. After infusion, blood volume increased by 12 ± 4 and 14 ± 5% in endurance-trained individuals versus control subjects, respectively (P = 0.264). Both endurance-trained individuals (8 ± 10%) and control subjects (7 ± 9%) experienced an increase in free wall strain from baseline, which was also similar following leg raise (7 ± 10 and 6 ± 10%, respectively; P = 0.464). However, infusion evoked a greater increase in basal longitudinal strain in endurance-trained versus control subjects (16 ± 14 vs. 6 ± 11%; P = 0.048), which persisted after leg raise (16 ± 18 vs. 3 ± 11%; P = 0.032). Apical longitudinal strain and RV free wall strain rates were not different between groups and remained unchanged after infusion across all segments. Endurance training results in a greater contribution of longitudinal myocardial deformation at the base of the RV in response to a haemodynamic volume challenge, which might reflect a greater region-specific functional reserve capacity.

Left ventricular mechanics in late second trimester of healthy pregnancy

OBJECTIVE

To evaluate left ventricular (LV) mechanics in the second trimester of healthy pregnancy and to determine the influence of underpinning hemodynamics (heart rate (HR), preload and afterload) on LV mechanics during gestation.

METHODS

This was a cross-sectional study of 18 non-pregnant, 14 nulliparous pregnant (22-26 weeks' gestation) and 13 primiparous postpartum (12-16 weeks after delivery) women. All pregnant and postpartum women had uncomplicated, singleton gestations. Cardiac structure and function were assessed using echocardiography. LV mechanics, specifically longitudinal strain, circumferential strain and twist/untwist, were measured using speckle-tracking echocardiography. Differences between groups were identified using ANCOVA, with age, HR, end-diastolic volume (EDV) and systolic blood pressure (SBP) as covariates. Relationships between LV mechanics and hemodynamics were examined using Pearson's correlation.

RESULTS

There were no significant differences in LV structure and traditional measurements of systolic and diastolic function between the three groups. Pregnant women, compared with non-pregnant ones, had significantly higher resting longitudinal strain (-22 ± 2% vs -17 ± 3%; P = 0.002) and basal circumferential strain (-23 ± 4% vs -16 ± 2%; P = 0.001). Apical circumferential strain and LV twist and untwist mechanics were similar between the three groups. No statistically significant relationships were observed between LV mechanics and HR, EDV or SBP within the groups.

CONCLUSIONS

Compared to the non-pregnant state, pregnant women in the second trimester of a healthy pregnancy have significantly greater resting systolic function, as assessed by LV longitudinal and circumferential strain. Contrary to previous work, these data show that healthy pregnant women should not exhibit reductions in resting systolic function between 22 and 26 weeks' gestation. The enhanced myocardial contractile function during gestation does not appear to be related to hemodynamic load and could be the result of other physiological adaptations to pregnancy. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Cardiovascular response to prescribed detraining among recreational athletes

Exercise-induced cardiac remodeling (EICR) and the attendant myocardial adaptations characteristic of the athlete’s heart may regress during periods of exercise reduction or abstinence. The time course and mechanisms underlying this reverse remodeling, specifically the impact of concomitant plasma volume (PV) contraction on cardiac chamber size, remain incompletely understood. We therefore studied recreational runners ( n = 21, age 34 ± 7 yr; 48% male) who completed an 18-wk training program (~7 h/wk) culminating in the 2016 Boston Marathon after which total exercise exposure was confined to <2 h/wk (no single session >1 h) for 8 wk. Cardiac structure and function, exercise capacity, and PV were assessed at peak fitness (10–14 days before) and at 4 wk and 8 wk postmarathon. Mixed linear modeling adjusting for age, sex, V̇o2peak, and marathon finish time was used to compare data across time points. Physiological detraining was evidenced by serial reductions in treadmill performance. Two distinct phases of myocardial remodeling and hematological adaptation were observed. After 4 wk of detraining, there were significant reductions in PV (Δ −6.0%, P < 0.01), left ventricular (LV) wall thickness (Δ −8.1%, <0.05), LV mass (Δ −10.3%, P < 0.001), and right atrial area (Δ −8.2%, P < 0.001). After 8 wk of detraining, there was a significant reduction in right ventricle chamber size (end-diastolic area Δ = −8.0%, P < 0.05) without further concomitant reductions in PV or LV wall thickness. Abrupt reductions in exercise training stimulus result in a structure-specific time course of reverse cardiac remodeling that occurs largely independently of PV contraction.

NEW & NOTEWORTHY Significant reverse cardiac remodeling, previously documented among competitive athletes, extends to recreational runners and occurs with a distinct time course. Initial reductions in plasma volume and left ventricular (LV) mass, driven by reductions in wall thickness, are followed by contraction of the right ventricle. Consistent with data from competitive athletes, LV chamber volumes appear less responsive to detraining and may be a more permanent adaptation to sport.

Resting cardiopulmonary function in Paralympic athletes with cervical spinal cord injury

PURPOSE

The purposes of this study were to describe resting cardiopulmonary function in highly trained athletes with cervical spinal cord injury (SCI) and to compare the data with able-bodied (AB) control subjects.

METHODS

Twelve Paralympic wheelchair rugby players with cervical SCI (injury level = C5-C7) and 12 AB controls matched for age, stature, and body mass were assessed for pulmonary function using spirometry, body plethysmography, and maximal inspiratory and expiratory mouth pressures; diaphragm function using magnetic stimulation of the phrenic nerves; and cardiac function using transthoracic echocardiography.

RESULTS

Total lung capacity, vital capacity, inspiratory reserve volume, and expiratory reserve volume were lower in SCI compared with AB (P < 0.01), whereas residual volume was elevated in SCI (P = 0.022). Airway resistance and maximal inspiratory mouth pressure were not different between groups (P > 0.41), whereas maximal expiratory mouth pressure, maximal transdiaphragmatic pressure, and twitch transdiaphragmatic pressure were lower in SCI (P < 0.01). Percent predicted total lung capacity was significantly correlated with maximal transdiaphragmatic pressure in SCI (r = 0.74), suggesting that the pulmonary restriction was a result of diaphragm weakness. Left ventricular mass, ejection fraction, stroke volume, and cardiac output were lower in SCI (P < 0.04), but early and late filling velocities during diastole were not different between groups (P > 0.05).

CONCLUSIONS

Highly trained athletes with cervical SCI exhibit a restrictive pulmonary defect, weakness of the expiratory and diaphragm muscles, atrophy of the heart, and reduced systolic cardiac function.

Left ventricular systolic function and diastolic filling after intermittent high intensity team sports

BACKGROUND

Prolonged steady state exercise can lead to a decrease in left ventricular (LV) function as well as promote the release of cardiac troponin T (cTnT). There is limited information on the effect of intermittent high intensity exercise of moderate duration.

OBJECTIVES

To determine the effect of intermittent high intensity exercise of moderate duration on LV function.

METHODS

Nineteen male rugby and football players (mean (SD) age 21 (2) years) volunteered. Assessments, before, immediately after, and 24 hours after competitive games, included body mass, heart rate (HR), and systolic blood pressure (sBP) as well as echocardiography to assess stroke volume (SV), ejection fraction (EF), systolic blood pressure/end systolic volume ratio (sBP/ESV), and global diastolic filling (E:A) as well as to indirectly quantify preload (LV internal dimension at end diastole (LVIDd)). Serum cTnT was analysed using a 3rd generation assay. Changes in LV function were analysed by repeated measures analysis of variance. cTnT data are presented descriptively.

RESULTS

SV (91 (26) v 91 (36) v 90 (35) ml before, after, and 24 hours after the game respectively), EF (71 (8) v 70 (9) v 71 (7)%), and sBP/ESV (4.2 (1.8) v 3.8 (1.9) v 4.1 (1.6) mm Hg/ml) were not significantly altered (p>0.05). Interestingly, whereas LVIDd was maintained after the game (50 (5) v 50 (6) mm), sBP was transiently but significantly reduced (131 (3) v 122 (3) mm Hg; p<0.05). E:A was moderately (p<0.05) reduced after the game (2.0 (0.4) v 1.5 (0.4)) but returned to baseline within 24 hours. No blood sample contained detectable levels of cTnT.

CONCLUSIONS

In this cohort, LV systolic function was not significantly altered after intermittent activity. A transient depression in global diastolic filling was partially attributable to a raised HR and could not be explained by myocyte disruption as represented by cTnT release.

Effect of prolonged exercise in a hypoxic environment on cardiac function and cardiac troponin T

BACKGROUND

Exercise induced cardiac fatigue has recently been observed after prolonged exercise. A moderate to high altitude has been suggested as a possible stimulus in the genesis of such cardiac fatigue.

OBJECTIVE

To investigate if exercise induced cardiac fatigue and or cardiac damage occurs after prolonged exercise in a hypoxic environment.

METHODS

Eight trained male triathletes volunteered for the study. Each completed two 50 mile cycle trials, randomly assigned from normobaric normoxia and normobaric hypoxia (15% FIO(2)). Echocardiographic assessment and whole blood collection was completed before, immediately after, and 24 hours after exercise. Left ventricular systolic and diastolic functional variables were calculated, and serum was analysed for cardiac troponin T. Results were analysed using a two way repeated measures analysis of variance, with alpha set at 0.05.

RESULTS

No significant differences were observed in either systolic or diastolic function across time or between trials. Cardiac troponin T was detected in one subject immediately after exercise in the normobaric hypoxic trial.

CONCLUSIONS

A 50 mile cycle trial in either normobaric normoxia or normobaric hypoxia does not induce exercise induced cardiac fatigue. Some people, however, may exhibit minimal cardiac damage after exercise in normobaric hypoxia. The clinical significance of this is yet to be elucidated.

Cardiac troponin T in female athletes during a two-day mountain marathon

BACKGROUND

Equivocal studies exist on the potential of cardiac damage following prolonged endurance exercise.

AIMS

The aim of the study was to examine humoral markers of cardiac damage in female athletes during a 2-day mountain endurance race.

METHODS

Venous blood samples were drawn from seven female competitors prior to, and immediately following day-1 and day-2 of the event. The serum was analysed for total creatine kinase (CK), creatine kinase isoenzyme MB (CKMB), and cardiac troponin T (cTnT).

RESULTS

Elevations in CK and CKMB were apparent following day-1 of the event (mean +/- SD; CK 84.1 +/- 54.6 mg/L vs. 387 +/- 276.7 mg/L, CKMB 2 +/- 1.7 mg/L vs. 5.9 +/- 1.7 mg/L) and subsequently rose further following race completion (CK 743 +/- 500 mg/L, CKMB 11.9 +/- 4.9 mg/L). Elevations in cTnT were noted in three competitors following day-1 cTNT (range 0.013-0.044 mg/L) and remained elevated in two competitors following day-2 (range 0.014-0.017 mg/L).

CONCLUSIONS

The elevations in cTnT likely represent release from the cytosolic fraction. The mechanism responsible for such release is yet to be elucidated.

Evidence of exercise-induced cardiac dysfunction and elevated cTnT in separate cohorts competing in an ultra-endurance mountain marathon race

Cardiac damage has recently been implicated in the aetiology of "exercise induced cardiac dysfunction". The humoral markers of cardiac damage that have been utilised to date are not sufficiently cardio-specific to investigate this hypothesis. The aim of the present study was to examine cardiac function following prolonged exercise, and investigate the contention of cardiac damage utilising a new highly cardio-specific marker. Thirty-seven competitors in the 2-day Lowe Alpine Mountain Marathon 2000 volunteered for the study. Competitors were sub-divided into 2 groups. Group 1 (n = 11) were examined using echocardiography pre and post the event, examining left ventricular diastolic and systolic function. Group 2 (n = 26) had venous blood samples drawn prior to the event and immediately following day-1 and day-2. Blood samples were analysed for total creatine kinase activity (CK), creatine kinase isoenzyme MB(mass) (CK-MB(mass)), and cardiac troponin T. Echocardiographic results indicated left ventricular diastolic and systolic dysfunction following cessation of exercise. CK and CK-MB(mass) were both elevated following day-1, and immediately following race completion. Cardiac troponin T levels were below the 99th percentile (0.01 microg/L) in all subjects prior to the event, following day-1 cTnT was elevated above 0.01 microg/L in 13 subjects, but returned to below 0.01 microg/L following race completion on day-2. However, no individual data reached clinical cut-off levels for acute myocardial infarction (AMI) (0.1 microg/L). Two days arduous exercise over mountainous terrain resulted in cardiac dysfunction, and significant skeletal muscular degradation. The elevation of cTnT above the 99th percentile in the present study is suggestive of minimal myocardial damage. The clinical significance of and exact mechanism responsible for such damage remains to be elucidated.