Exercise-Induced Cardiac Fatigue after a 45-Minute Bout of High-Intensity Running Exercise Is Not Altered under Hypoxia

Inversion of Left Ventricular Axial Shortening: In Silico Proof of Concept for Treatment of HFpEF

Left ventricular (LV) longitudinal function is mechanically coupled to the elasticity of the ascending aorta (AA). The pathophysiologic link between a stiff AA and reduced longitudinal strain and the subsequent deterioration in longitudinal LV systolic function is likely relevant in heart failure with preserved ejection fraction (HFpEF). The proposed therapeutic effect of freeing the LV apex and allowing for LV inverse longitudinal shortening was studied in silico utilizing the Living Left Heart Human Model (Dassault Systémes Simulia Corporation). LV function was evaluated in a model with (A) an elastic AA, (B) a stiff AA, and (C) a stiff AA with a free LV apex. The cardiac model simulation demonstrated that freeing the apex caused inverse LV longitudinal shortening that could abolish the deleterious mechanical effect of a stiff AA on LV function. A stiff AA and impairment of the LV longitudinal strain are common in patients with HFpEF. The hypothesis-generating model strongly suggests that freeing the apex and inverse longitudinal shortening may improve LV function in HFpEF patients with a stiff AA.

Left and right ventricular strain-volume/area loops: a narrative review of current physiological understanding and potential clinical value

Traditionally, echocardiography is used for volumetric measurements to aid in assessment of cardiac function. Multiple echocardiographic-based assessment techniques have been developed, such as Doppler ultrasound and deformation imaging (e.g., peak global longitudinal strain (GLS)), which have shown to be clinically relevant. Volumetric changes across the cardiac cycle can be related to deformation, resulting in the Ventricular Strain-Volume/Area Loop. These Loops allow assessment of the dynamic relationship between longitudinal strain change and volumetric change across both systole and diastole. This integrated approach to both systolic and diastolic function assessment may offer additional information in conjunction with traditional, static, measures of cardiac function or structure. The aim of this review is to summarize our current understanding of the Ventricular Strain-Volume/Area Loop, describe how acute and chronic exposure to hemodynamic stimuli alter Loop characteristics, and, finally, to outline the potential clinical value of these Loops in patients with cardiovascular disease. In summary, several studies observed Loop changes in different hemodynamic loading conditions and various (patho)physiological conditions. The diagnostic and prognostic value, and physiological interpretation remain largely unclear and have been addressed only to a limited extent.

Dose-effect of exercise intervention on heart rate variability of acclimatized young male lowlanders at 3,680 m

This study investigated whether exercise could improve the reduced HRV in an environment of high altitude. A total of 97 young, healthy male lowlanders living at 3,680 m for >1 year were recruited. They were randomized into four groups, of which three performed-low-, moderate-, and high-intensity (LI, MI, HI) aerobic exercise for 4 weeks, respectively. The remaining was the control group (CG) receiving no intervention. For HI, compared to other groups, heart rate (p = 0.002) was significantly decreased, while standard deviation of RR intervals (p < 0.001), SD2 of Poincaré plot (p = 0.046) and the number of successive RR interval pairs that differ by > 50 ms divided by total number of RR (p = 0.032), were significantly increased after intervention. For MI, significantly increase of trigonometric interpolation in NN interval (p = 0.016) was observed after exercise. Further, a decrease in systolic blood pressure (SBP) after high-intensity exercise was found significantly associated with an increase in SD2 (r = - 0.428, p = 0.042). These results indicated that there was a dose effect of different intensities of aerobic exercise on the HRV of acclimatized lowlanders. Moderate and high-intensity aerobic exercise would change the status of the autonomic nervous system (ANS) and decrease the blood pressure of acclimatized lowlanders exposed to high altitude.

A new protocol for a single-stage combined cardiopulmonary and echocardiography exercise test: a pilot study

Aims

The value of cardiopulmonary exercise testing (CPET) and exercise stress echocardiography (ESE) in managing cardiac disease is well known, but no standard CPET-ESE protocol is currently recommended. This pilot study aims to compare feasibility and cardiac function responses between a new high-intensity single-stage combined test (CPET-hiESE) and a standard maximal ESE (smESE).

Methods and results

After screening and maximal CPET, all volunteers (n = 21) underwent three ESE modalities: (i) based on the gas exchange threshold (hiESE-GET, 40% of peak-GET, 6 min), (ii) based on heart rate (HR) (hiESE-HR, 80% of peak HR, 6 min), and (iii) smESE (85% of predicted peak HR for age, 3 min). Speckle tracking echocardiography (STE) and tissue Doppler imaging (TDI) were measured at each step. There was superior image quality and data completeness for the right ventricle strain for both hiESE modalities compared with smESE (71.4 and 76.2 vs. 42.9%, P = 0.07). Left ventricular STE data completeness was similar for all three conditions. Despite systematically higher HR, work rate and levels of exertion in the smESE compared with hiESE, STE and TDI parameters were not systematically different. Concordance correlation coefficients ranged from 0.56 to 0.88, lowest for strain rate parameters and mean difference from -0.34 to 1.53, highest for TDI measurements.

Conclusion

The novel CPET-hiESE protocol allowed for better data completeness, at lower levels of exertion compared with smESE, without systematically different cardiac reserve measurements in healthy participants. This single-stage protocol can be individualized to clinical populations, which would provide practical advantages to standard testing.

Exposure to Intermittent Environmental Hypoxia Promotes Vascular Remodeling through Angiogenesis in the Liver of Largemouth Bass (Micropterus salmoides)

In this study, we explored the effects of 4 weeks of intermittent hypoxic exposure (IHE) on liver angiogenesis and related regulatory mechanisms in largemouth bass (Micropterus salmoides). The results indicated that the O2 tension for loss of equilibrium (LOE) decreased from 1.17 to 0.66 mg/L after 4 weeks of IHE. Meanwhile, the red blood cell (RBC) and hemoglobin concentrations significantly increased during IHE. Our investigation also found that the observed increase in angiogenesis was correlated with a high expression of related regulators, such as Jagged, phosphoinositide-3-kinase (PI3K), and mitogen-activated protein kinase (MAPK). After 4 weeks of IHE, the overexpression of factors related to angiogenesis processes mediated by HIF-independent pathways (such as nuclear factor kappa-B (NF-κB), NADPH oxidase 1 (NOX1), and interleukin 8 (IL8)) was correlated with the accumulation of lactic acid (LA) in the liver. The addition of cabozantinib, a specific inhibitor of VEGFR2, blocked the phosphorylation of VEGFR2 and downregulated the expression of downstream angiogenesis regulators in largemouth bass hepatocytes exposed to hypoxia for 4 h. These results suggested that IHE promoted liver vascular remodeling by the regulation of angiogenesis factors, presenting a potential mechanism for the improvement of hypoxia tolerance in largemouth bass.

Association of left ventricular strain-volume loop characteristics with adverse events in patients with heart failure with preserved ejection fraction

AIMS

Patients with heart failure with preserved ejection fraction (HFpEF) are characterized by impaired diastolic function. Left ventricular (LV) strain-volume loops (SVL) represent the relation between strain and volume during the cardiac cycle and provide insight into systolic and diastolic function characteristics. In this study, we examined the association of SVL parameters and adverse events in HFpEF.

METHODS AND RESULTS

In 235 patients diagnosed with HFpEF, LV-SVL were constructed based on echocardiography images. The endpoint was a composite of all-cause mortality and Heart Failure (HF)-related hospitalization, which was extracted from electronic medical records. Cox-regression analysis was used to assess the association of SVL parameters and the composite endpoint, while adjusting for age, sex, and NYHA class. HFpEF patients (72.3% female) were 75.8 ± 6.9 years old, had a BMI of 29.9 ± 5.4 kg/m2, and a left ventricular ejection fraction of 60.3 ± 7.0%. Across 2.9 years (1.8-4.1) of follow-up, 73 Patients (31%) experienced an event. Early diastolic slope was significantly associated with adverse events [second quartile vs. first quartile: adjusted hazards ratio (HR) 0.42 (95%CI 0.20-0.88)] after adjusting for age, sex, and NYHA class. The association between LV peak strain and adverse events disappeared upon correction for potential confounders [adjusted HR 1.02 (95% CI 0.96-1.08)].

CONCLUSION

Early diastolic slope, representing the relationship between changes in LV volume and strain during early diastole, but not other SVL-parameters, was associated with adverse events in patients with HFpEF during 2.9 years of follow-up.

Myocardial Fatigue at a Glance

Expanding on the modern lexicon of heart failure (HF), the novel mechano-energetic concept of myocardial fatigue describes a transiently energy-depleted myocardium with impaired contractility and relaxation in the face of adverse haemodynamic load. It encompasses established concepts of ventricular-arterial decoupling, deranged cardiac energetics and impaired myocardial efficiency, offering an alternative explanation for functional causes of HF.

Left ventricular strain-volume loops and diastolic dysfunction in suspected heart failure with preserved ejection fraction

BACKGROUND

Presence of left ventricular diastolic dysfunction (DD) is key in the pathogenesis of heart failure with preserved ejection fraction (HFpEF). However, non-invasive assessment of diastolic function is complex, cumbersome, and largely based on consensus recommendations. Novel imaging techniques may help detecting DD. Therefore, we compared left ventricular strain-volume loop (SVL) characteristics and diastolic (dys-)function in suspected HFpEF patients.

METHOD AND RESULTS

257 suspected HFpEF patients with sinus rhythm during echocardiography were prospectively included. 211 patients with quality-controlled images and strain and volume analysis were classified according to the 2016 ASE/EACVI recommendations. Patients with indeterminate diastolic function were excluded, resulting in two groups: normal diastolic function (control; n = 65) and DD (n = 91). Patients with DD were older (74.8 ± 6.9 vs. 68.5 ± 9.4 years, p < 0.001), more often female (88% vs 72%, p = 0.021), and more often had a history of atrial fibrillation (42% vs. 23%, p = 0.024) and hypertension (91% vs. 71%, p = 0.001) compared to normal diastolic function. SVL analysis showed a larger uncoupling i.e., a different longitudinal strain contribution to volume change, in DD compared to controls (0.556 ± 1.10% vs. -0.051 ± 1.14%, respectively, P < 0.001). This observation suggests different deformational properties during the cardiac cycle. After adjustment for age, sex, history of atrial fibrillation and hypertension, we found an adjusted odds ratio of 1.68 (95% confidence interval 1.19-2.47) for DD per unit increase in uncoupling (range: -2.95-3.20).

CONCLUSION

Uncoupling of the SVL is independently associated with DD. This might provide novel insights in cardiac mechanics and new opportunities to assess diastolic function non-invasively.

Investigating the roles of exercise intensity and biological sex on postexercise alterations in cardiac function

The term exercise-induced cardiac fatigue (EICF) has typically been used to describe a transient reduction in cardiac function following prolonged-strenuous exercise. Recent evidence demonstrates that EICF can occur following only 45 min of high-intensity exercise when assessed using exercising stress echocardiography. This investigation sought to examine whether sprint intervals (SIT; 6 × 30 s Wingate tests), or 90-min moderate-cycling with sprint intervals (MIX; 90 min with 1 × 30 s Wingate test every 15 min) would cause greater EICF than 90 min (CON) or 3 h (LONG) moderate-cycling assessed using stress echocardiography, with a secondary aim to interrogate sex differences in EICF. Seventeen participants (M: 9, F: 8) underwent three cycling sessions with stress-echocardiography performed before-and-after each condition at a target heart rate (HR) of 100 beats·min^-1, with the CON testing occurring at the mid-point of the 3 h LONG condition. For all conditions, measures of left ventricular (LV) systolic [stroke volume, ejection fraction (EF), peak longitudinal strain, isovolumetric contraction time, S') and diastolic (E/A, E', isovolumetric relaxation time, longitudinal strain rate) function were reduced after exercise (all P < 0.05). In the right ventricle (RV), systolic function was reduced (tricuspid annular plane systolic excursion, S', peak longitudinal strain and strain rate) following all conditions, and fractional area change was reduced to the greatest degree following SIT (condition × time, P = 0.01). Females demonstrated lesser impairments in LV EF, and elastance (ESP/ESV) compared with males (P < 0.05). Markers of EICF occurred similarly following all cycling loads, suggesting the functional changes may be due to altered loading conditions and reduced stress-echocardiography workload. However, males experienced greater cardiac alterations in some measures, likely due to greater changes in postexercise loading conditions.NEW & NOTEWORTHY This investigation sought to determine the role of exercise intensity on the magnitude of exercise-induced cardiac fatigue using stress echocardiography to maintain loading conditions, with a secondary purpose of assessing sex differences. Unexpectedly, it was found that all cycling loads elicited the same magnitude of functional alteration, which likely represents a common response to exercise and stress echocardiography, rather than intrinsic cardiac impairment. Males demonstrated greater alterations than females, likely due to sex differences in postexercise hemodynamics.

Strenuous Endurance Exercise and the Heart: Physiological versus Pathological Adaptations

Although the benefits of regular physical activity on cardiovascular health are well established, the effects of strenuous endurance exercise (SEE) have been a matter of debate since ancient times. In this article, we aim to provide a balanced overview of what is known about SEE and the heart-from epidemiological evidence to recent cardiac imaging findings. Lifelong SEE is overall cardioprotective, with endurance master athletes showing in fact a youthful heart. Yet, some lines of research remain open, such as the need to elucidate the time-course and potential relevance of transient declines in heart function (or increases in biomarkers of cardiac injury) with SEE. The underlying mechanisms and clinical relevance of SEE-associated atrial fibrillation, myocardial fibrosis, or high coronary artery calcium scores also remain to be elucidated. © 2022 American Physiological Society. Compr Physiol 12:1-19, 2022.

Exercise-Induced Cardiac Fatigue in Recreational Ultramarathon Runners at Moderate Altitude: Insights From Myocardial Deformation Analysis

Background

Controversy exists on the actual occurrence of exercise-induced cardiac fatigue (EICF) with ultraendurance exercise, as well as on whether factors such as age or training status might predispose to this condition. The present study aimed to assess the occurrence of EICF among recreational ultramarathon runners, as well as to determine potential predictive factors.

Methods

Nineteen male recreational runners (42 ± 12yrs) participated in a 55-km trial race at moderate altitude (1,800–2,500 m). Participants were evaluated before and after the race using Doppler echocardiography and myocardial deformation analysis. EICF was determined as a reduction >5% of either left ventricular global longitudinal strain (LVGLS) or right ventricular free wall strain (RVFWS). Demographical (age, body mass index), training (training experience, volume and intensity), competition (finishing time, relative intensity) and biochemical variables (blood lactate, creatine kinase [CK] and CK-MB) were assessed as predictors of EICF.

Results

A significant reduction in LVGLS (20.1 ± 2.1% at baseline vs. 18.8 ± 2.4% at post-race, p = 0.026), but not in RVFWS (27.4 ± 7.0 vs. 24.6 ± 5.3%, p = 0.187), was observed after the race. EICF was present in 47 and 71% of the participants attending to the decrease in LVGLS and RVFWS, respectively. No associations were found between any of the analyzed variables and EICF except for age, which was associated with the magnitude of decrement of RVFWS (r = 0.58, p = 0.030).

Conclusions

Ultramarathon running at moderate altitude seems to induce EICF in a considerable proportion of recreational athletes.

Acute Effects of Heart Rate-Controlled Exergaming on Vascular Function in Young Adults

Objective: Acute and regular moderate-intensity endurance exercise (MIEE) is known to positively affect vascular function. The present study assessed if an exercise session in an innovative exergame called the ExerCube can induce similar vascular reactions as an MIEE session. Materials and Methods: Twenty-eight healthy recreationally active participants (13 females and 15 males; aged 24.8 ± 3.9 years; with body mass index 23.2 ± 2.3 kg/m²) completed an exergaming session (EGS) in the ExerCube (25 minutes) and an MIEE session on a treadmill (35 minutes, 65%-70% of maximal heart rate [HR]) in a randomized order. Both before and throughout the 45 minutes after the training sessions, pulse wave velocity (PWV), total peripheral resistance (TPR), stroke volume (SV), and HR were recorded. The study was approved by the Research Ethics Board of the Martin-Luther-Universität Halle-Wittenberg (Medical Faculty of the Martin-Luther-Universität 2019-177). Results: There were different hemodynamic responses to both types of exercises. PWV was significantly decreased 45 minutes after the EGS (P < 0.001). No significant changes were detected after MIEE (P = 0.109). TPR was significantly lower after both exercise sessions (P < 0.01). Only the EGS resulted in a significant decrease in SV 15 minutes after exercise (P < 0.001). The HR was significantly (P < 0.05) higher after both exercise sessions. After the EGS, the increase in HR was still significantly higher (P = 0.011) 45 minutes after the session. The interaction effects revealed significant differences in PWV (15 minutes, P = 0.035; 30 minutes, P = 0.004; and 45 minutes, P < 0.001), favoring the EGS. Conclusion: The EGS seems to induce a relevant exercise stimulus that can modulate vascular function. Therefore, this exergame may present an effective tool for prevention of cardiovascular diseases.

A new perspective on cardiovascular drift during prolonged exercise

Prolonged exercise induces cardiovascular drift, which is characterized by decreasing mean arterial pressure (MAP), stroke volume and heart rate increase. Cardiovascular drift has been debated for a long time. Although the exact mechanisms underlying cardiovascular drift are still unknown, two theories have been proposed. The first is that increased skin blood flow displaces blood volume from central circulation to the periphery, which reduces stroke volume. According to this theory, the rise in heart rate is presumably responding to the drop in stroke volume and MAP. The alternative theory is that an increase in heart rate is due to an increase in sympathetic nervous activity causing reducing time at diastole, and therefore stroke volume. It may be difficult to determine a single robust factor accounting for cardiovascular drift, due to the broad range of circumstances. The primary focus of this review is to elucidate our understanding of cardiovascular drift during prolonged exercise through nitric oxide and force-frequency relationship. We highlight for the very first time that cardiovascular drift (in some conditions and within a specific time period) may be considered as a protective strategy against potential damage that could be induced by the intense and prolonged contraction of the myocardium.

Exercise Training Induces Left- but not Right-sided Cardiac Remodelling in Olympic Rowers

Whilst the athlete's heart has been extensively described, less work has focused on the potential for elite athletes to demonstrate further cardiac remodelling upon an increase in training volume. Moreover, little work explored potential side-specific cardiac remodelling. Therefore, we examined the impact of an increase in training volume across 9-months in elite rowers on left- and right-sided cardiac structure, function and mechanics (i. e. longitudinal, radial and circumferential strain, twist and strain-volume loops). As part of the preparations to the 2012 Olympic Games, twenty-seven elite rowers (26.4±3.7years, 19 male) underwent echocardiography prior to and post (9 months) an increase in training volume (24 to 30-35 h weekly). Training increased left ventricular structure, including wall thickness, diameter, volume, mass and LV twist (all p<0.05). Female rowers demonstrated larger adaptation in left ventricular diameter and mass compared to male rowers (both p<0.05). No changes were observed in other measures of left ventricular function in both sexes (all p>0.05). The 9-month intervention showed no change in right ventricular/atrial structure, function or mechanics (all p>0.05). In conclusion, our data revealed that 9-month increased training volume in elite rowers induced left-sided (but not right-sided) structural remodelling, concomitant with an increase in left ventricular twist, with some changes larger in women.

Acute exercise-induced changes in cardiac function relates to right ventricular remodeling following 12-wk hypoxic exercise training

Repeated ventricular exposure to alterations in workload may relate to subsequent cardiac remodeling. We examined whether baseline acute changes in right (RV) and left ventricular (LV) function relate to chronic cardiac adaptation to 12-wk exercise training. Twenty-one healthy individuals performed 12-wk high-intensity endurance running training under hypoxia (fraction of inspired oxygen: 14.5%). Resting transthoracic echocardiography was performed before and after the training program to assess ventricular structure, function, and mechanics (including strain-area/volume loops). In addition, we examined systolic cardiac function during recumbent exercise under hypoxia at baseline (heart rate of 110-120 beats/min, "stress echocardiography"). Fifteen individuals completed training (22.0 ± 2.4 yr, 10 males). Hypoxic exercise training increased RV size, including diameter and area (all P < 0.05). With exception of an increase in RV fractional area change (P = 0.03), RV function did not change post-training (all P > 0.05). Regarding the RV strain-area loop, lower systolic and diastolic slopes were found post-training (P < 0.05). No adaptation in LV structure, function, or mechanics was observed (all P > 0.05). To answer our primary aim, we found that a greater increase in RV fractional area change during baseline stress echocardiography (r = -0.67, P = 0.01) inversely correlated with adaptation in RV basal diameter following 12-wk training. In conclusion, 12-wk high-intensity running hypoxic exercise training induced right-sided structural remodeling, which was, in part, related to baseline increase in RV fractional area change to acute exercise. These data suggest that acute cardiac responses to exercise may relate to subsequent RV remodeling after exercise training in healthy individuals.NEW & NOTEWORTHY During exercise, the right ventricle is exposed to a disproportionally higher wall stress than the left ventricle, which is further exaggerated under hypoxia. In this study, we showed that 12-wk high-intensity running hypoxic exercise training induced right-sided structural remodeling, which was, in part, related to baseline cardiac increase in RV fractional area change to acute exercise. These data suggest that acute RV responses to exercise are related to subsequent right ventricular remodeling in healthy individuals upon hypoxic training.