Exercise Capacity, Breathing Pattern, and Gas Exchange During Exercise for Patients with Isolated Diastolic Dysfunction

Physical Functioning in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent, yet interventions and therapies to improve outcomes remain limited. There has been increasing attention towards the impact of comorbidities and physical functioning (PF) on poor clinical outcomes within this population. In this review, we summarize and discuss the literature on PF in HFpEF, its association with clinical and patient-centered outcomes, and future advances in the care of HFpEF with respect to PF. Multiple PF metrics have been demonstrated to provide prognostic value within HFpEF, yet the data are less robust compared with other patient populations, highlighting the need for further investigation. The evaluation and detection of poor PF provides a potential strategy to improve care in HFpEF, and future studies are needed to understand if modulating PF improves clinical and/or patient-reported outcomes. LAY SUMMARY: • Patients with heart failure with preserved ejection fraction (HFpEF) commonly have impaired physical functioning (PF) demonstrated by limitations across a wide range of common PF metrics.• Impaired PF metrics demonstrate prognostic value for both clinical and patient-reported outcomes in HFpEF, making them plausible therapeutic targets to improve outcomes.• Clinical trials are ongoing to investigate novel methods of detecting, monitoring, and improving impaired PF to enhance HFpEF care.Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent, yet interventions and therapies to improve outcomes remain limited. As such, there has been increasing focus on the impact of physical performance (PF) on clinical and patient-centered outcomes. In this review, we discuss the state of PF in patients with HFpEF by examining the multitude of PF metrics available, their respective strengths and limitations, and their associations with outcomes in HFpEF. We highlight future advances in the care of HFpEF with respect to PF, particularly regarding the evaluation and detection of poor PF.

Cardiovascular and systemic determinants of exercise capacity in people with type 2 diabetes mellitus

The global burden of heart failure (HF) is on the rise owing to an increasing incidence of lifestyle related diseases, predominantly type 2 diabetes mellitus (T2D). Diabetes is an independent risk factor for cardiovascular disease, and up to 75% of those with T2D develop HF in their lifetime. T2D leads to pathological alterations within the cardiovascular system, which can progress insidiously and asymptomatically in the absence of conventional risk factors. Reduced exercise tolerance is consistently reported, even in otherwise asymptomatic individuals with T2D, and is the first sign of a failing heart. Because aggressive modification of cardiovascular risk factors does not eliminate the risk of HF in T2D, it is likely that other factors play a role in the pathogenesis of HF. Early identification of individuals at risk of HF is advantageous, as it allows for modification of the reversible risk factors and early initiation of treatment with the aim of improving clinical outcomes. In this review, cardiac and extra-cardiac contributors to reduced exercise tolerance in people with T2D are explored.

Novel Echocardiography-Derived Left Ventricular Stiffness Index in Low-Flow Versus Normal-Flow Severe Aortic Stenosis with Preserved Left Ventricular Ejection Fraction

Background Paradoxical low-flow (LF) severe aortic stenosis (AS) with preserved left ventricular ejection fraction (LVEF) may have poorer prognosis than normal-flow (NF) AS, though its pathophysiology remained unclear. In particular, LV stiffness has not been compared between LF vs NF. We used a novel echocardiography-derived index of LV stiffness to compare between these groups. Consecutive patients with medically-managed isolated severe AS (aortic valve area < 1 cm²) and preserved LVEF (>50%) were studied. Echocardiographic LV stiffness index was measured by a method previously validated against cardiac catheterization. We compared LF (stroke volume index, SVI < 35 ml/m²) and NF severe AS. Of the 352 patients, 121 (34%) were LF. Both LF and NF groups had similar demographics, valve areas and indices. Compared to NF, LF severe AS had higher LV stiffness indices (>0.11 ml^-1 OR 3.067, 95% CI 1.825-5.128, p < 0.001). Increased LV stiffness was associated with concentric remodelling and more severe diastolic dysfunction, especially in LF AS. An LV stiffness index of > 0.11 ml^-1 was independently associated with increased mortality, after adjusting for age, clinical and echocardiographic parameters (HR 2.283 95% CI 1.318-3.968, p = 0.003). Non-invasive echocardiographic-derived index of LV stiffness may be important in LF AS. Increased LV stiffness was related to LV concentric remodelling and diastolic dysfunction, and associated with poorer clinical outcomes in medically-managed AS.

Cardiopulmonary Exercise Test in heart failure: A Sine qua non

A robust literature, over the last years, supports the indication of cardiopulmonary exercise testing (CPET) in patients with cardiovascular diseases. Understanding exercise physiology is a crucial component of the critical evaluation of exercise intolerance. Shortness of breath and exercise limitation is often treated with an improper focus, partly because the pathophysiology is not well understood in the frame of the diagnostic spectrum of each subspecialty. A vital field and research area have been cardiopulmonary exercise test in heart failure with preserved/reduced ejection fraction, evaluation of heart failure patients as candidates for LVAD-Implantation, as well as for LVAD-Explantation and ultimately for heart transplantation. All the CPET variables provide synergistic prognostic discrimination. However, Peak VO2 serves as the most critical parameter for risk stratification and prediction of survival rate.

Left Atrial Volume, Cardiorespiratory Fitness, and Diastolic Function in Healthy Individuals: The HUNT Study, Norway

Background Left atrial (LA) size and cardiorespiratory fitness (CRF) are predictors of future cardiovascular events in high-risk populations. LA dilatation is a diagnostic criterion for left ventricular diastolic dysfunction. However, LA is dilated in endurance athletes with high CRF, but little is known about the association between CRF and LA size in healthy, free-living individuals. We hypothesized that in a healthy population, LA size was associated with CRF and leisure-time physical activity, but not with echocardiographic indexes of left ventricular diastolic dysfunction. Methods and Results In this cross-sectional study from HUNT (Nord-Trøndelag Health Study), 107 men and 138 women, aged 20 to 82 years, without hypertension, cardiovascular, pulmonary, or malignant disease participated. LA volume was assessed by echocardiography and indexed to body surface area LAVI (left atrial volume index). CRF was measured as peak oxygen uptake (VO_2peak) using ergospirometry, and percent of age- and-sex-predicted VO_2peak was calculated. Indexes of left ventricular diastolic dysfunction were assessed in accordance with latest recommendations. LAVI was >34 mL/m² in 39% of participants, and LAVI was positively associated with VO_2peak and percentage of age- and-sex-predicted VO_2peak (β [95% CI], 0.11 [0.06-0.16] and 0.18 [0.09-0.28], respectively) and weighted minutes of physical activity per week (β [95% CI], 0.01 [0.003-0.015]). LAVI was not associated with other indexes of left ventricular diastolic dysfunction. There was an effect modification between age and VO_2peak/percentage of age- and-sex-predicted VO_2peak showing higher LAVI with advanced age and higher VO_2peak/percentage of age- and-sex-predicted VO_2peak as presented in prediction diagrams. Conclusions Interpretation of LAVI as a marker of diastolic dysfunction should be done in relation to age-relative CRF. Studies on the prognostic value of LAVI in fit subpopulations are needed.

Effects of detraining on breathing pattern and ventilatory efficiency in young soccer players

BACKGROUND

This study investigated the effects of detraining on breathing pattern. The aim of this study was to evaluate the effect of a six-week detraining period on breathing patterns and ventilatory efficiency.

METHODS

Fourteen young soccer players were evaluated at the end of a competitive season and after a six-week detraining period. Assessment of respiratory efficiency was based on VE/VCO2 slope changes below 70% of exercise intensity. All participants underwent twice an incremental graded exercise test up to exhaustion.

RESULTS

No differences in breathing frequency and inspiratory time/total time ratio (Ti/Ttot) were found after detraining (P>0.05). Differences in tidal volume (VT), VT/Ti quotient and VE were significant (P<0.05) at between 40 to 100% of exercise intensity. The VE/VCO2 slope did not change (P>0.05) during a postdetraining maximal incremental test.

CONCLUSIONS

A six-week detraining period causes changes in inspiratory flow but does not affect the inspiratory time/total respiratory cycle time ratio. The overall ventilatory efficiency of the respiratory system remains constant and is not affected by detraining.

Causes of exercise intolerance in heart failure with preserved ejection fraction: searching for consensus

Exercise intolerance is one of the cardinal symptoms of heart failure with preserved ejection fraction (HFpEF). We review its mechanistic basis using evidence from exercise studies. One barrier to a consensus understanding of the pathophysiology is heterogeneity of the patient population. Therefore, we pay special attention to varying study definitions of the disease and their possible impact on the causal factors that are implicated. We then discuss the role of exercise testing and its potential to subtype HFpEF in to more homogeneous mechanism-based subclasses.

Left ventricular diastolic performance at rest is essential for exercise capacity in patients with non-complicated myocardial infarction

INTRODUCTION

In patients with recent myocardial infarction (MI) limited exercise capacity during physical activity is an important symptom and the base for future treatment. The myocardial injury after MI leads to both systolic and diastolic left ventricular (LV) dysfunction.

OBJECTIVE

The aim of this study was to assess the relevance of systolic and diastolic LV function for cardiopulmonary exercise capacity in patients with prior MI.

METHODS

Sixty-five consecutive patients after first MI without signs and symptoms of heart failure, aged 52 ± 6 years, were included in the study. The following echo parameters were evaluated: LV ejection fraction (LVEF), peak early and late diastolic velocities (E, A), deceleration time of E wave (dec t E), ratio of early trans-mitral to early annular diastolic velocities (E/e'), velocity propagation of early filling (Vp), and diameters and volumes of LV and left atrium (LA). CPET variables included: oxygen uptake at peak exercise (peak VO2), oxygen pulse (VO2 HR), VE/VCO2 slope, circulatory power (CP) and recovery half time (T1/2).

RESULTS

Significant correlations were demonstrated between peak VO2 and E/e' (p < 0.001), peak VO2 and dec t E (p < 0.001), VO2 HR and E/e' (p = 0.002) and between VE/VCO2 and E/e' (p < 0.001). Twenty patients with elevated LV filling pressure achieved significantly lower peak VO2 (1624 vs. 1932 ml, p = 0.027) VO2 HR (11.70 vs. 14.05, p = 0.011) and CP (287,073 vs. 361,719, p = 0.014). By using multivariate regression model we found that only E/e' (p = 0.001) and dec t E (p = 0.008) significantly contributed to peak VO2.

CONCLUSIONS

Diastolic dysfunction, particularly LV filling pressure, determine exercise capacity, despite differences in LV ejection fraction in patients with prior MI.

Left atrial volume as an independent predictor of exercise capacity in patients with isolated diastolic dysfunction presented with exertional dyspnea

Background

Left atrial volume (LAV) and exercise capacity are important prognostic determinants of cardiovascular risk. Exercise intolerance and increased LAV are expected in patients with diastolic dysfunction. While dyspnea is the symptom reported by the patient and considered subjective, exercise capacity obtained by exercise testing provides an objective measure of cardiovascular fitness. The objective of this study is to determine the relationship between LAV index and exercise capacity in patients with isolated diastolic dysfunction who presented with exertional dyspnea.

Methods

We studied consecutive patients with dyspnea who underwent treadmill exercise testing and transthoracic echocardiography on the same day. LAV was assessed using the biplane area-length method. Symptom-limited exercise testing was performed immediately after echocardiography. Patients with coronary artery disease, valvular or congenital heart disease, left ventricular systolic dysfunction, pulmonary hypertension or positive exercise test were excluded.

Results

The study consisted of 111 patients (58.1 ± 9.2 years of age, 54.1% male, 64% hypertension, 57.7% dyslipidemia and 20.7% diabetes). The exercise duration and capacity were 6.8 ± 2.1 minutes and 7.7 ± 1.9 METs, respectively. Left ventricular ejection fraction and LAV index was 71.0 ± 5.8% and 31.4 ± 10.5 ml/m², respectively. In multivariate analysis, age [odds ratios (OR) 0.94; 95% confidence interval (CI) 0.89-0.99], body mass index (OR 0.82, 95% CI 0.72-0.93), and LAV index (OR 0.92, 95% CI 0.87-0.97) were associated with good exercise capacity.

Conclusion

In patients with isolated diastolic dysfunction and exertional dyspnea, an increased LAV index, a marker of chronic diastolic dysfunction, is associated with poor exercise capacity.

Gas exchange consequences of left heart failure

This review explores the pathophysiology of gas exchange abnormalities arising consequent to either acute or chronic elevation of pulmonary venous pressures. The initial experimental studies of acute pulmonary edema outlined the sequence of events from lymphatic congestion with edema fluid to frank alveolar flooding and its resultant hypoxemia. Clinical studies of acute heart failure (HF) suggested that hypoxemia was associated only with the final stage of alveolar flooding. However, in patients with chronic heart failure and normal oxygenation, hypoxemia could be produced by the administration of potent pulmonary vasodilators, suggesting that hypoxic pulmonary vasoconstriction is an important reflex for these patients. Patients with chronic left HF commonly manifest a reduced diffusing capacity, an abnormality that appears to be a consequence of chronic elevation of left atrial pressure. That reduction in diffusing capacity does not appear to be primarily attributable to increases in lung water but is improved by any sustained treatment that improves overall cardiac function. Patients with heart failure may also manifest an abnormally elevated VE/VCO2 during exercise, and that exercise ventilation abnormality arises as a consequence of both alveolar hyperventilation and elevated physiologic dead space. That elevated exercise VE/VCO2 in an HF patient has proven to be a powerful predictor of an adverse outcome and hence it has received sustained attention in the HF literature. At least three of the classes of drugs used to treat HF will normalize the exercise VE/VCO2, suggesting that the excessive ventilation response may be linked to elevated sympathetic activity.

Cardiopulmonary exercise testing and its relation to oxidative stress in patients with hypertension

An increase in reactive oxygen species has been implicated in the pathologies of hypertension. This study was designed to evaluate antioxidant activity in hypertensive patients and to assess the relationship between oxidative stress and exercise tolerance in hypertensive patients with mild left ventricular diastolic dysfunction (LVDD). A total of 42 patients, aged 51±9 years, with a long history of hypertension and mild LVDD (mitral flow velocities-E/A <1, deceleration time of E >220 ms, and preserved ejection fraction-EF >50%), and 30 controls without cardiovascular disease, aged 50±7 years, underwent cardiopulmonary exercise testing (CPET). Peak oxygen uptake (peak VO(2)), oxygen pulse (VO(2)/heart rate (HR)) and ventilatory anaerobic threshold (VAT) were obtained during CPET. Antioxidant activity of superoxide dismutase (SOD) and glutathione peroxidase in the blood was measured before and after exercise. Reduced peak VO(2) (1715±426 vs. 2083±465 ml min(-1), P<0.001), VO(2)/HR (12.0±2.8 vs. 14.6±3.3 ml per beat, P<0.001) and percentage of peak VO(2) at VAT (55.5±15.8% vs. 64.5±14.7%, P=0.007) were observed in hypertensive patients, compared with controls. Antioxidant protection was significantly attenuated in hypertensive patients, compared with controls, before (945 vs. 1006, P=0.012) and after exercise (954 vs. 1051, P<0.001). The level of SOD before and after exercise was significantly associated with LVDD in hypertensive patients (P=0.012 and 0.02, respectively). In addition, the degree of LVDD before exercise (E/A) influenced the degree of exercise capability (peak VO(2)) (P=0.016). Asymptomatic hypertensive patients with mild LVDD had reduced cardiopulmonary capacity, accurately identified by CPET. The redox state in hypertensive patients was significantly related to LVDD and exercise tolerance. Attenuated antioxidant protection was associated with long-term hypertension.

Increased left ventricular stiffness impairs exercise capacity in patients with heart failure symptoms despite normal left ventricular ejection fraction

Aims. Several mechanisms can be involved in the development of exercise intolerance in patients with heart failure despite normal left ventricular ejection fraction (HFNEF) and may include impairment of left ventricular (LV) stiffness. We therefore investigated the influence of LV stiffness, determined by pressure-volume loop analysis obtained by conductance catheterization, on exercise capacity in HFNEF. Methods and Results. 27 HFNEF patients who showed LV diastolic dysfunction in pressure-volume (PV) loop analysis performed symptom-limited cardiopulmonary exercise testing (CPET) and were compared with 12 patients who did not show diastolic dysfunction in PV loop analysis. HFNEF patients revealed a lower peak performance (P = .046), breathing reserve (P = .006), and ventilation equivalent for carbon dioxide production at rest (P = .002). LV stiffness correlated with peak oxygen uptake (r = -0.636, P < .001), peak oxygen uptake at ventilatory threshold (r = -0.500, P = .009), and ventilation equivalent for carbon dioxide production at ventilatory threshold (r = 0.529, P = .005). Conclusions. CPET parameters such as peak oxygen uptake, peak oxygen uptake at ventilatory threshold, and ventilation equivalent for carbon dioxide production at ventilatory threshold correlate with LV stiffness. Increased LV stiffness impairs exercise capacity in HFNEF.

An examination of exercise mode on ventilatory patterns during incremental exercise

Both cycle ergometry and treadmill exercise are commonly employed to examine the cardiopulmonary system under conditions of precisely controlled metabolic stress. Although both forms of exercise are effective in elucidating a maximal stress response, it is unclear whether breathing strategies or ventilator efficiency differences exist between exercise modes. The present study examines breathing strategies, ventilatory efficiency and ventilatory capacity during both incremental cycling and treadmill exercise to volitional exhaustion. Subjects (n = 9) underwent standard spirometric assessment followed by maximal cardiopulmonary exercise testing utilising cycle ergometry and treadmill exercise using a randomised cross-over design. Respiratory gases and volumes were recorded continuously using an online gas analysis system. Cycling exercise utilised a greater portion of ventilatory capacity and higher tidal volume at comparable levels of ventilation. In addition, there was an increased mean inspiratory flow rate at all levels of ventilation during cycle exercise, in the absence of any difference in inspiratory timing. Exercising V(E)/VCO₂slope and the lowest V(E)/VCO₂value, was lower during cycling exercise than during the treadmill protocol indicating greater ventilatory efficiency. The present study identifies differing breathing strategies employed during cycling and treadmill exercise in young, trained individuals. Exercise mode should be accounted for when assessing breathing patterns and/or ventilatory efficiency during incremental exercise.

The pathophysiology of heart failure with normal ejection fraction: exercise echocardiography reveals complex abnormalities of both systolic and diastolic ventricular function involving torsion, untwist, and longitudinal motion

OBJECTIVES

The purpose of this study was to test the hypothesis that in heart failure with normal ejection fraction (HFNEF) exercise limitation is due to combined systolic and diastolic abnormalities, particularly involving ventricular twist and deformation (strain) leading to reduced ventricular suction, delayed untwisting, and impaired early diastolic filling.

BACKGROUND

A substantial proportion of patients with heart failure have a normal left ventricular ejection fraction. Currently the pathophysiology is considered to be due to abnormal myocardial stiffness and relaxation.

METHODS

Patients with a diagnosis of HFNEF and proven cardiac limitation by cardiopulmonary exercise testing were studied by standard, tissue Doppler, and speckle tracking echocardiography at rest and on submaximal exercise.

RESULTS

Fifty-six patients (39 women; mean age 72 +/- 7 years) with a clinical diagnosis of HFNEF and 27 age-matched healthy control subjects (19 women; mean age 70 +/- 7 years) had rest and exercise images of sufficient quality for analysis. At rest, systolic longitudinal and radial strain, systolic mitral annular velocities, and apical rotation were lower in patients, and all failed to rise normally on exercise. Systolic longitudinal functional reserve was also significantly lower in patients (p < 0.001). In diastole, patients had reduced and delayed untwisting, reduced left ventricular suction at rest and on exercise, and higher end-diastolic pressures. Mitral annular systolic and diastolic velocities, systolic left ventricular rotation, and early diastolic untwist on exercise correlated with peak VO(2)max.

CONCLUSIONS

In HFNEF there are widespread abnormalities of both systolic and diastolic function that become more apparent on exercise. HFNEF is not an isolated disorder of diastole.

Diastolic dysfunction: a link between hypertension and heart failure

Diastolic heart failure is characterized by the symptoms and signs of heart failure, a preserved ejection fraction and abnormal left ventricular (LV) diastolic function caused by a decreased LV compliance and relaxation. The signs and symptoms of diastolic heart failure are indistinguishable from those of heart failure related to systolic dysfunction; therefore, the diagnosis of diastolic heart failure is often one of exclusion. The majority of patients with heart failure and preserved ejection fraction have a history of hypertension. Hypertension induces a compensatory thickening of the ventricular wall in an attempt to normalize wall stress, which results in LV concentric hypertrophy, which in turn decreases LV compliance and LV diastolic filling. There is an abnormal accumulation of fibrillar collagen accompanying the hypertension-induced LV hypertrophy, which is also associated with decreased compliance and LV diastolic dysfunction. There are no specific guidelines for treating diastolic heart failure, but pharmacological treatment should be directed at normalizing blood pressure, promoting regression of LV hypertrophy, preventing tachycardia and treating symptoms of congestion. Preventive strategies directed toward an early and aggressive blood pressure control are likely to offer the greatest promise for reducing the incidence of diastolic heart failure.

Exercise oscillatory breathing in diastolic heart failure: prevalence and prognostic insights

AIMS

Exercise intolerance occurs in both systolic and diastolic heart failure (HF). Exercise oscillatory breathing (EOB) is a powerful predictor of survival in patients with systolic HF. In diastolic HF, EOB prevalence and prognostic impact are unknown.

METHODS AND RESULTS

A total of 556 HF patients (405 with systolic HF and 151 with diastolic HF) underwent cardiopulmonary exercise testing (CPET). Diastolic HF was defined as signs and symptoms of HF, a left ventricular ejection fraction > or =50%, and a Doppler early (E) mitral to early mitral annulus ratio (E') > or =8. CPET responses, EOB prevalence and its ability to predict cardiac-related events were examined. EOB prevalence in systolic and diastolic HF was similar (35 vs. 31%). Compared with the patients without EOB, patients with EOB and either systolic or diastolic HF had a higher New York Heart Association class, lower peak VO(2) and higher E/E' ratio (all P < 0.01). Univariate Cox regression analysis demonstrated that peak VO(2), VE/VCO(2) slope and EOB all were significant predictors of cardiac events in both systolic and diastolic HF. Multivariable analysis revealed that EOB was retained as a prognostic marker in systolic HF and was the strongest predictor of cardiac events in diastolic HF.

CONCLUSION

EOB occurrence is similar in diastolic and systolic HF and provides relevant clues for the identification of diastolic HF patients at increased risk of adverse events.

Diastolic dysfunction in exercise and its role for exercise capacity

Diastolic dysfunction is frequent in elderly subjects and in patients with left ventricular hypertrophy, vascular disease and diabetes mellitus. Patients with diastolic dysfunction demonstrate a reduced exercise capacity and might suffer from congestive heart failure (CHF). Presence of symptoms of CHF in the setting of a normal systolic function is referred to as heart failure with normal ejection fraction (HFNEF) or, if evidence of an impaired diastolic function is observed, as diastolic heart failure (DHF). Reduced exercise capacity in diastolic dysfunction results from a number of pathophysiological alterations such as slowed myocardial relaxation, reduced myocardial distensibility, elevated filling pressures, and reduced ventricular suction forces. These alterations limit the increase of ventricular diastolic filling and cardiac output during exercise and lead to pulmonary congestion. In healthy subjects, exercise training can enhance diastolic function and exercise capacity and prevent deterioration of diastolic function in the course of aging. In patients with diastolic dysfunction, exercise capacity can be enhanced by exercise training and pharmacological treatment, whereas improvement of diastolic function can only be observed in few patients.