Cardiac and peripheral responses to exercise in patients with chronic heart failure

Clinical Impact of Preoperative Symptoms of Aortic Stenosis on Prognosis After Transcatheter Aortic Valve Replacement

Background: The prognostic significance of different presentations of aortic stenosis (AS) remains unclear. Our aim was to analyze outcomes after transcatheter aortic valve replacement (TAVR) according to preoperative AS symptoms. Methods and Results: We retrospectively enrolled 369 consecutive patients (age 84.3±5.0 years, and 64% females) who underwent TAVR from 2014 to 2021. We divided them into 4 groups by the main preoperative symptom: asymptomatic (n=50), chest pain (n=46), heart failure (HF; n=240), and syncope (n=33). Post-TAVR rates of HF readmission, all-cause death and cardiac death were compared among the 4 groups. The 4 groups showed no significant trends in age, sex, stroke volume index, or echocardiography indices of AS severity. During a follow-up, the overall survival rate at 1 and 5 years after TAVR was 97% and 90% in the asymptomatic group, 96% and 69% in the chest pain group, 93% and 69% in the HF group, and 90% and 72% in the syncope group, respectively. HF and syncope symptom had significantly lower HF readmission or cardiac death-free survival at 5 years after TAVR (log-rank test P=0.038). In the Cox hazard multivariate analysis, preoperative syncope was an independent predictor of future HF readmission or cardiac death after TAVR (HR=9.87; 95% CI 1.67-97.2; P=0.035). Conclusions: AS patients with preoperative syncope or HF had worse outcomes after TAVR than those with angina or no symptoms.

Hemodynamic Changes During Physiological and Pharmacological Stress Testing in Patients With Heart Failure: A Systematic Review and Meta-Analysis

Although disease etiologies differ, heart failure patients with preserved and reduced ejection fraction (HFpEF and HFrEF, respectively) both present with clinical symptoms when under stress and impaired exercise capacity. The extent to which the adaptation of heart rate (HR), stroke volume (SV), and cardiac output (CO) under stress conditions is altered can be quantified by stress testing in conjunction with imaging methods and may help to detect the diminishment in a patient’s condition early. The aim of this meta-analysis was to quantify hemodynamic changes during physiological and pharmacological stress testing in patients with HF. A systematic literature search (PROSPERO 2020:CRD42020161212) in MEDLINE was conducted to assess hemodynamic changes under dynamic and pharmacological stress testing at different stress intensities in HFpEF and HFrEF patients. Pooled mean changes were estimated using a random effects model. Altogether, 140 study arms with 7,248 exercise tests were analyzed. High-intensity dynamic stress testing represented 73% of these data (70 study arms with 5,318 exercise tests), where: HR increased by 45.69 bpm (95% CI 44.51–46.88; I2 = 98.4%), SV by 13.49 ml (95% CI 6.87–20.10; I2 = 68.5%), and CO by 3.41 L/min (95% CI 2.86–3.95; I2 = 86.3%). No significant differences between HFrEF and HFpEF groups were found. Despite the limited availability of comparative studies, these reference values can help to estimate the expected hemodynamic responses in patients with HF. No differences in chronotropic reactions, changes in SV, or CO were found between HFrEF and HFpEF. When compared to healthy individuals, exercise tolerance, as well as associated HR and CO changes under moderate-high dynamic stress, was substantially impaired in both HF groups. This may contribute to a better disease understanding, future study planning, and patient-specific predictive models.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/], identifier [CRD42020161212].

Rest and exercise oxygen uptake and cardiac output changes 6 months after successful transcatheter mitral valve repair

Aims

Changes in peak exercise oxygen uptake (VO₂) and cardiac output (CO) 6 months after successful percutaneous edge‐to‐edge mitral valve repair (pMVR) in severe primary (PMR) and functional mitral regurgitation (FMR) patients are unknown.

The aim of the study was to assess the efficacy of pMVR at rest by echocardiography, VO₂ and CO (inert gas rebreathing) measurement and during cardiopulmonary exercise test with CO measurement.

Methods and results

We evaluated 145 and 115 patients at rest and 98 and 66 during exercise before and after pMVR, respectively.

After successful pMVR, significant reductions in MR and NYHA class were observed in FMR and PMR patients. Cardiac ultrasound showed reverse remodelling (left ventricular end‐diastolic volume from 158 ± 63 mL to 147 ± 64, P < 0.001; ejection fraction from 51 ± 15 to 48 ± 14, P < 0.001; pulmonary artery systolic pressure (PASP) from 43 ± 13 to 38 ± 8 mmHg, P < 0.001) in the entire population. These changes were significant in PMR (n = 62) and a trend in FMR (n = 53), except for PASP, which decreased in both groups. At rest, CO and stroke volume (SV) increased in FMR with a concomitant reduction in arteriovenous O₂ content difference [ΔC(a‐v)O₂]. Peak exercise, CO and SV increased significantly in both groups (CO from 5.5 ± 1.4 L/min to 6.3 ± 1.5 and from 6.2 ± 2.4 to 6.7 ± 2.0, SV from 57 ± 19 mL to 66 ± 20 and from 62 ± 20 to 69 ± 20, in FMR and PMR, respectively), whereas peak VO₂ was unchanged and ΔC(a‐v)O₂ decreased.

Conclusions

These data confirm pMVR‐induced clinical improvement and reverse ventricular remodelling at a 6‐month analysis and show, in spite of an increase in CO, an unchanged exercise performance, which is achieved through a ‘more physiological’ blood flow distribution and O₂ extraction behaviour. Direct rest and exercise CO should be measured to assess pMVR efficacy.

Effects of chronotropic incompetence on exercise capacity in people with heart failure versus age-matched controls

Chronotropic incompetence (CI) is an inability to adequately raise heart rate during physiological stress. We established CI prevalence and exercise capacity in heart failure versus healthy age-matched controls. We conducted a systematic search (1966-July 1, 2020) and meta-analysis of studies reporting peak VO₂ in people with heart failure with reduced (HFrEF) and preserved (HFpEF) left ventricular ejection fraction and controls. Seventeen studies of 4410 participants were included, 4167 with heart failure and 243 age-matched controls. In both heart failure phenotypes, CI was more prevalent in HFrEF (51.7%) and HFpEF (55.8%) than in healthy controls (9%). Mortality was 24% higher in people with HFrEF and CI versus those with HFrEF and without CI; OR -1.24 (95% CI -2.20 to -0.28; p = 0.01). People with heart failure and CI had lower peak VO₂ than those without CI (MD) -3.30 ml kg^-1 min^-1 (95% CI -4.25 to -2.35, p < 0.01), and this was primarily driven by the HFrEF sub-population (MD) -3.86 ml kg^-1 min^-1 (95% CI -4.83 to -2.89, p < 0.01). Maximum heart rate MD -37.51 beats min^-1 (95% CI -41.99 to -33.03, p < 0.01) and maximum-resting heart rate were lower MD -29.44 beats min^-1 (95% CI -34.55 to -24.33, p < 0.01) in people with heart failure with CI vs without CI. People with heart failure and CI demonstrated similar respiratory exchange ratios (RER) to people with heart failure but without CI; (MD) -0.02 (95% CI -0.03 to -0.01), p < 0.01, suggesting that poor effort was unlikely to explain CI. CI is more prevalent in heart failure than in age-matched controls and although it is associated with lower peak VO₂ in HFrEF, it is unrelated to the lower peak VO₂ in HFpEF. RER values suggest poor effort is unlikely to explain these findings.

The utility of the oxygen pulse recovery as a marker of the cardiac output response to exercise in patients with chronic heart failure

PURPOSE

The cardiac output (CO) response to exercise is a useful marker to grade the prognosis and severity of chronic heart failure (CHF). The recovery of the oxygen pulse (OP) is a non-invasive parameter, which is related to exercise capacity in cardiac patients. However, the relation between OP recovery and the central haemodynamic response to exercise remains to be determined. We hypothesized that an impaired OP recovery is associated with a reduced CO response to exercise in CHF patients.

METHODS

Sixty one CHF patients performed cardiopulmonary exercise test with simultaneous measurement of CO. Impaired OP recovery was defined as an overshoot during the first minute of recovery or OP at 1-min recovery as a percentage of peak OP (OP_RR ).

RESULTS

An OP overshoot was observed in 9% (n = 5) of patients. In these patients, peak CO and VO₂ were significantly lower (peak CO 7.9 ± 0.8 versus 11.2 ± 4.3 L/min and peak VO₂ 14.1 ± 4.7 versus 19.6 ± 5.8 ml min^-1  kg^-1 ). Mean relative recovery of OP was 78 ± 20%. Slow OP recovery (negative OP_RR ) was seen in 13% (n = 8). Peak CO and VO₂ were significantly lower in the negative OP_RR group (11 ± 4 versus 8 ± 0.7 L/min and 19.7 ± 5.9 versus 14.6 ± 3.7 ml kg min^-1 ). There was a significant relation between OP_RR and stroke volume (SV) _RR (r = .57), as well as between OP_RR and a-v O₂ diff _RR (r_s  = .4).

CONCLUSION

An impaired OP recovery is associated with a reduced CO response to exercise and worse functional status. Therefore, the OP recovery can be used to grade the severity of CHF.

Heart rate during exercise: mechanisms, behavior, and therapeutic and prognostic implications in heart failure patients with reduced ejection fraction

Exercise intolerance is a typical manifestation of patients affected by heart failure with reduced ejection fraction (HFrEF); however, the relationship among functional capacity, mortality, and exercise-induced heart rate response during exercise remains unclear in either sinus rhythm or atrial fibrillation subjects. Heart rate increase during incremental load exercise has a typical pattern in normal subjects, whereas it is commonly compromised in HFrEF patients, mainly due to the imbalance of the autonomic nervous system. In the present review, we aim to describe the behavior of heart rate during exercise in normal subjects and in HFrEF patients in sinus rhythm and atrial fibrillation, understanding and explaining the mechanism leading to a different exercise performance and functional limitation. Moreover, the role of chronotropic incompetence and the need of standardizing the cutoff criteria are also discussed in order to clarify the clinical importance, the prognostic relevance, and the potential therapeutic implications of this condition. Looking into the relative contribution and interaction of heart rate response during exercise might represent an important issue to guide individualized therapeutic interventions and prognostic assessment in HFrEF patients.

Effort Oxygen Saturation and Effort Heart Rate to Detect Exacerbations of Chronic Obstructive Pulmonary Disease or Congestive Heart Failure

Background: current algorithms for the detection of heart failure (HF) and chronic obstructive pulmonary disease (COPD) exacerbations have poor performance. Methods: this study was designed as a prospective longitudinal trial. Physiological parameters were evaluated at rest and effort (walking) in patients who were in the exacerbation or stable phases of HF or COPD. Parameters with relevant discriminatory power (sensitivity (Sn) or specificity (Sp) ≥ 80%, and Youden index ≥ 0.2) were integrated into diagnostic algorithms. Results: the study included 127 patients (COPD: 56, HF: 54, both: 17). The best algorithm for COPD included: oxygen saturation (SaO₂) decrease ≥ 2% in minutes 1 to 3 of effort, end-of-effort heart rate (HR) increase ≥ 10 beats/min and walking distance decrease ≥ 35 m (presence of one criterion showed Sn: 0.90 (95%, CI(confidence interval): 0.75–0.97), Sp: 0.89 (95%, CI: 0.72–0.96), and area under the curve (AUC): 0.92 (95%, CI: 0.85–0.995)); and for HF: SaO₂ decrease ≥ 2% in the mean-of-effort, HR increase ≥ 10 beats/min in the mean-of-effort, and walking distance decrease ≥ 40 m (presence of one criterion showed Sn: 0.85 (95%, CI: 0.69–0.93), Sp: 0.75 (95%, CI: 0.57–0.87) and AUC 0.84 (95%, CI: 0.74–0.94)). Conclusions: effort situations improve the validity of physiological parameters for detection of HF and COPD exacerbation episodes.

Arterial Stiffness is Related to Impaired Exercise Capacity in Patients With Coronary Artery Disease and History of Myocardial Infarction

BACKGROUND

Augmented arterial stiffness and reduced cardiorespiratory fitness are associated with increased morbidity and mortality from coronary artery disease (CAD). The relationship between exercise capacity and arterial stiffness is independent of known influencing variables in CAD. This study aimed to analyse the interaction between exercise capacity, arterial stiffness and early vascular ageing in patients with CAD.

METHODS

This cross-sectional study included 96 CAD patients with myocardial infarction (55.9±10.9years, 81 men) referred to cardiac rehabilitation. Arterial stiffness was assessed using carotid-femoral pulse wave velocity (cf-PWV). Cardiopulmonary exercise test was performed to measure VO₂peak. Comparisons of VO₂peak across cf-PWV risk threshold values (high-risk cf-PWV≥10m/s) and tertile groups, and across cf-PWV threshold values and age groups (younger group<60 years) were performed. Correlation tests were used to study the association between pair of variables.

RESULTS

Patients with high-risk cf-PWV had lower VO₂peak than those with low-risk cf-PWV (p<0.001). VO₂peak decreased across tertiles of cf-PWV, showing significantly lower values in the third tertile (p<0.001). There were no differences in the VO₂peak between younger patients with high-risk cf-PWV and older patients irrespective of their cf-PWV values. VO₂peak showed an upward trend in younger patients with low-risk cf-PWV compared to their age-mates with high-risk cf-PWV (p=0.09). VO₂peak was strongly and inversely correlated with cf-PWV (r=-0.502, p<0.001).

CONCLUSIONS

Arterial stiffening is associated with lower cardiorespiratory fitness in CAD patients with myocardial infarction. When its values are above risk threshold, exercise capacity is impaired regardless of the relationship between age and arterial stiffness.

Association between baseline cardiovascular mechanics and exercise capacity in patients with coronary artery disease

OBJECTIVE

Functional capacity is one of the cardinal determinants of morbidity and mortality in patients with coronary artery disease (CAD). We hypothesized that baseline cardiovascular mechanics, including cardiac systolic and diastolic functions, arterial mechanics, and ventriculoarterial interaction, may play a role in predicting exercise capacity in patients with CAD.

METHODS

Fifty consecutive patients with CAD who were referred to cardiac rehabilitation were prospectively included in the study. Patients with non-sinus rhythms or severe valvular disease were excluded. Full left ventricular pressure-volume loops were constructed and arterial mechanics was evaluated using echocardiographic and tonometric measurements. Cardiopulmonary exercise tests were performed to measure exercise capacity.

RESULTS

Fifty patients were enrolled in the study. Ventriculo-arterial coupling showed a moderate correlation with peak oxygen consumption (VO2) (r=0.410, p=0.04) in patients with reduced left ventricular ejection fraction (LVEF). Only left ventricular volume at 15 mm Hg (r=0.514, p<0.01) in diastolic parameters (stiffness constant, p=0.75; ventricular compliance, p=0.17) and arterial compliance (r=0.467, p=0.01) in arterial parameters [arterial elastance, p=0.27; systemic vascular resistance, p=0.45; augmentation pressure, p=0.85; augmentation index (AIx), p=0.63; heart rate-corrected AIx, p=0.68] emerged as significant factors correlated with peak VO2 in patients with normal LVEF.

CONCLUSION

Comprehensive evaluation of resting cardiovascular mechanics can give clues about exercise-recruited reserves of the cardiovascular system. Optimization of ventriculo-arterial coupling in patients with reduced LVEF and arterial compliance in patients with normal LVEF should be the main target in patients with CAD and limited functional capacity.

Effects of exercise on postexercise ventricular-arterial coupling and pulsatile efficiency in patients with systolic dysfunction

BACKGROUND

A suboptimal ventricular-arterial (VA) interaction may have a prolonged depressing effect on the failing heart after functional reserves forced to their limits under stress conditions such as exercise. The continuation of excessive load in the postexercise period may be more important than the load during exercise, because the sum of postexercise periods generally exceeds exercise time itself. We sought that exercise-induced changes in postexercise VA coupling and pulsatile efficiency in patients with heart failure (HF).

METHODS

Thirty consecutive HF with reduced ejection fraction (EF) and thirty age-, sex- and peak VO2 -matched subjects with preserved EF were enrolled. Pre- and postexercise echocardiographic and tonometric measurements were taken to calculate left ventricular and arterial elastances, arterial compliance and wave reflections, and steady and pulsatile power.

RESULTS

VA coupling significantly deteriorated in HF group (from 1·50 ± 0·47 to 2·00 ± 0·75 mmHg/mL, P < 0·01), but control group maintained basal favourable coupling status after exercise (from 1·04 ± 0·29 to 1·03 ± 0·24 mmHg/mL, P = 0·77). Pulsatile percentage of total power significantly increased with exercise in HF group, whereas it showed a significant decrease in control group. The change in pulsatile power fraction was correlated with the change in augmentation pressure (r = 0·41, ß = 3·00, P < 0·01) and inversely correlated with the change in total arterial compliance (r = -0·29, ß = -8·52, P = 0·02).

CONCLUSION

Our data indicate that exercise-induced VA decoupling and pulsatile inefficiency extend into postexercise phase in patients with systolic dysfunction. The exact duration of these derangements requires further studies.

Characterization of exercise limitations by evaluating individual cardiac output patterns: a prospective cohort study in patients with chronic heart failure

BACKGROUND

Patients with chronic heart failure (CHF) suffer from exercise intolerance due to impaired central hemodynamics and subsequent alterations in peripheral skeletal muscle function and structure. The relative contribution of central versus peripheral factors in the reduced exercise capacity is still subject of debate. The main purpose was to investigate heterogeneity in the nature of exercise intolerance by evaluating individual cardiac output (Q) patterns. The secondary purpose was to evaluate whether patient and disease characteristics were associated with a central hemodynamic exercise limitation.

METHODS

Sixty-four stable CHF patients performed a symptom limited incremental exercise test with respiratory gas analysis and simultaneous assessment of Q, using a radial artery pulse contour analysis method. A central hemodynamic exercise limitation was defined as a plateau or decline in Q from 90 to 100 % of exercise duration.

RESULTS

Data from 61 patients were analyzed. A central hemodynamic exercise limitation was observed in 21 patients (34 %). In these patients, a higher occurrence of a plateau/decrease in oxygen uptake (VO2) (52 % vs 23 %, p = 0.02), stroke volume (SV) (100 % vs. 75 %, p = 0.01) and chronotropic incompetence (31 % vs. 2.5 %, p = 0.01) was observed, while presence of a left bundle branch block (LBBB) occurred significantly less (19 % vs 48 %, p = 0.03) There was no difference in disease characteristics such as etiology, duration, NYHA class, mitral regurgitation or ischemia.

CONCLUSIONS

The study revealed considerable heterogeneity in the nature of exercise limitations between moderately impaired CHF patients. In one third of the study population a plateau or decrease in Q towards peak exercise was demonstrated, which is indicative of a central hemodynamic exercise limitation. A central hemodynamic exercise limitation was associated with an impairment to augment stroke volume and heart rate.

Association of left atrial booster-pump function with heart failure symptoms in patients with severe aortic stenosis and preserved left ventricular ejection fraction

BACKGROUND

Identification of heart failure (HF) symptoms in patients with severe aortic stenosis (AS) and preserved left ventricular (LV) ejection fraction (EF) is clinically important, but assessment of HF symptoms is challenging. It was recently reported that resting left atrium (LA) functions are related to exercise performance and are also important prognostic markers for patients with HF. The aim of this study was to assess the association of the HF symptoms with LA function in patients with severe AS and preserved LVEF.

METHODS

We retrospectively studied 40 patients with severe AS and preserved LVEF (all ≥50%) who were referred for aortic valve replacement (AVR). LA reservoir (SR-LAs), conduit (SR-LAe), and booster-pump (SR-LAa) functions were determined as the averaged global LA speckle tracking longitudinal strain rate from apical four- and two-chamber views. Twenty patients were symptomatic and 20 asymptomatic.

RESULTS

Aortic stenosis severity was similar for the 2 groups. Symptomatic status was associated with age, LV mass index, hemoglobin, B-type natriuretic peptide, LV end-systolic volume index, LVEF, LA volume index, SR-LAs, SR-LAe, and SR-LAa. Importantly, multivariate logistic regression analysis revealed that SR-LAa was the only independent determinant of symptomatic status (OR = 0.242, P = 0.002). Furthermore, significant improvement of SR-LAa was observed along with the reduction in LA volume index and LV mass index after AVR.

CONCLUSIONS

SR-LAa was found to be associated with the HF symptoms. Characterization of LA booster-pump function may be useful for the assessment of the symptomatic status in patients with severe AS patients and limited physical activity.

A differing role of oxidative stress in the regulation of central and peripheral hemodynamics during exercise in heart failure

This study sought to characterize the role of free radicals in regulating central and peripheral hemodynamics at rest and during exercise in patients with heart failure (HF). We examined cardiovascular responses to dynamic handgrip exercise (4, 8, and 12 kg at 1 Hz) following consumption of either a placebo or acute oral antioxidant cocktail (AOC) consisting of vitamin C, E, and α-lipoic acid in a balanced, crossover design. Central and peripheral hemodynamics, mean arterial pressure, cardiac index, systemic vascular resistance (SVR), brachial artery blood flow, and peripheral (arm) vascular resistance (PVR) were determined in 10 HF patients and 10 age-matched controls. Blood assays evaluated markers of oxidative stress and efficacy of the AOC. When compared with controls, patients with HF exhibited greater oxidative stress, measured by malondialdehyde (+36%), and evidence of endogenous antioxidant compensation, measured by greater superoxide dismutase activity (+83%). The AOC increased plasma ascorbate (+50%) in both the HF patients and controls, but significant systemic hemodynamic effects were only evident in the patients with HF, both at rest and throughout exercise. Specifically, the AOC reduced mean arterial pressure (-5%) and SVR (-12%) and increased cardiac index (+7%) at each workload. In contrast, peripherally, brachial artery blood flow and PVR (arm) were unchanged by the AOC. In conclusion, these data imply that SVR in patients with HF is, at least in part, mediated by oxidative stress. However, this finding does not appear to be the direct result of muscle-specific changes in PVR.

Breathing strategy to preserve exercising cardiac function in patients with heart failure

The heart and lungs are closely linked as they lie in series, share a common surface area and compete for space within the thoracic cavity. The heart and lungs are exposed to the similar changes in intrathoracic pressure, and reflexes within one organ can influence the other (i.e. vagal influence of lung inflation on heart rate). In patients with heart failure, these cardiopulmonary interactions may be altered due to decreased lung and left ventricular compliance, increased cardiac size, high cardiac filling pressure and altered receptor sensitivity to neural activation. Exercise further affects the cardiopulmonary interactions by stimulating an increase in the depth and frequency of breathing which accentuates the fluctuations in intrathoracic pressure, and by requiring large increases in stroke volume and heart rate in order to respond to the increased metabolic demand. Previous work from our laboratory suggested that patients with heart failure avoid high lung volumes during exercise, often at the expense of unnecessary large positive expiratory intrathoracic pressures resulting in significant wasted effort. Moreover, we also observed that voluntarily increases in lung volume in patients with heart failure induced a mild relative bradycardia, a response not observed in similar aged healthy individuals. Thus, we hypothesized that the rapid shallow low lung volume breathing, in combination with positive expiratory intrathoracic pressure, often adopted by patients with heart failure during exercise is an attempt to preserve, or even enhance, the cardiac response to exercise.

Estimating stroke volume from oxygen pulse during exercise

This investigation aimed at verifying whether it was possible to reliably assess stroke volume (SV) during exercise from oxygen pulse (OP) and from a model of arterio-venous oxygen difference (a-vO(2)D) estimation. The model was tested in 15 amateur male cyclists performing an exercise test on a cycle-ergometer consisting of a linear increase of workload up to exhaustion. Starting from the analysis of previous published data, we constructed a model of a-vO(2)D estimation (a-vO(2)D(est)) which predicted that the a-vO(2)D at rest was 30% of the total arterial O(2) content (CaO(2)) and that it increased linearly during exercise reaching a value of 80% of CaO(2) at the peak workload (W(max)) of cycle exercise. Then, the SV was calculated by applying the following equation, SV = OP/a-vO(2)D(est), where the OP was assessed as the oxygen uptake/heart rate. Data calculated by our model were compared with those obtained by impedance cardiography. The main result was that the limits of agreement between the SV assessed by impedance cardiography and the SV estimated were between 22.4 and -27.9 ml (+18.8 and -24% in terms of per cent difference between the two SV measures). It was concluded that our model for estimating SV during effort may be reasonably applicable, at least in a healthy population.

Central haemodynamics and peripheral muscle function during exercise in patients with chronic heart failure

In this narrative review of the current literature, we examine the central and peripheral mechanisms responsible for the exercise intolerance of chronic heart failure and highlight briefly the benefits of exercise training in the treatment of this debilitating disorder. Specifically, we identify the common finding of reduced cardiac output reserve during exercise conditions leading to decreased exercise tolerance. We also reveal that the stroke volume response to exercise varies depending on the individual patient, the presence of mitral regurgitation, and the aetiology of heart failure. Chronic heart failure patients with left ventricular systolic dysfunction appear able to use the Frank-Starling mechanism to compensate (in part) for their decreased contractile reserve. Patients with left ventricular diastolic dysfunction have normal contractile function; however, they are unable to make use of the Frank-Starling mechanism during exercise conditions. We also reveal that pericardial constraint may limit diastolic filling and exercise capacity in patients with chronic heart failure. It appears that interventions that reduce pericardial constraint and mitral regurgitation enhance diastolic filling and increase exercise tolerance. A series of peripheral muscle changes also occur, including changes in muscle mass, cellular structure, energy metabolism, and blood flow. Each of these factors is associated with decreased exercise capacity and the symptoms of chronic heart failure. Exercise training has been shown to improve both central haemodynamics and peripheral muscle function leading to improvements in exercise capacity, functional status, and overall quality of life in patients with chronic heart failure.

Left atrial remodelling contributes to the progression of asymptomatic left ventricular systolic dysfunction to chronic symptomatic heart failure

Systolic heart failure (HF) is a progressive disorder that often begins with asymptomatic left ventricular (LV) systolic dysfunction and culminates in symptoms from fluid overload and poor end-organ perfusion. The progression to symptomatic HF is accompanied by marked activation of neurohormonal and cytokine systems, as well as a series of adaptive LV anatomical and functional changes, collectively referred to as LV remodelling. However, the mechanisms underlying symptom appearance have not been delineated and the weight of experimental and clinical evidence suggests that the development of symptomatic HF occurs independently of the haemodynamic status of the patient. The left atrium is a muscular chamber strategically located between the left ventricle and the pulmonary circulation with important mechanical function (modulation of LV filling), which is closely coupled with its endocrine (atrial natriuretic peptide synthesis and secretion) and regulatory (contribution to the control of sympathetic activity and vasopressin release) functions. In this narrative review we provide evidence supporting the concept that left atrial dilation and systolic dysfunction (left atrial remodelling) contributes to the progression of asymptomatic LV dysfunction to chronic symptomatic systolic HF as it is a prerequisite for the development of the pulmonary congestion and marked neuronhormoral activity that characterize the symptomatic state.

Impaired central hemodynamic response and exaggerated vasoconstriction during muscle metaboreflex activation in heart failure patients

The muscle metaboreflex is enhanced in chronic heart failure (CHF) patients, and this fact has been associated with the early fatigue shown by these patients in response to exercise. In animal studies of CHF, it was found that the limited capacity to enhance ventricular performance is responsible for a functional shift from a cardiac output to a systemic vascular resistance (SVR) increase in the mechanism by which the cardiovascular system raises blood pressure in response to the metaboreflex. However, the existence of this functional shift is still unknown in humans. The present study was undertaken to test the hypothesis that a similar hemodynamic response was also present in humans with CHF. The hemodynamic response to metaboreflex activation obtained through postexercise ischemia was assessed in nine patients with CHF and nine healthy controls (CTL) by means of impedance cardiography. The main results were that 1) the blood pressure rise due to the metaboreflex was similar in the two groups; 2) the CTL group achieved the blood pressure response via cardiac output increase, and the CHF group, via SVR increase; and 3) stroke volume was enhanced in the CTL group and decreased in the CHF group. This study demonstrates that in CHF patients, metaboreflex recruitment causes a functional shift from flow increase to peripheral vasoconstriction in the mechanism through which blood pressure is increased. The incapacity to enhance cardiac performance and stroke volume is probably the primary cause of this cardiovascular alteration.

Influence of water immersion, water gymnastics and swimming on cardiac output in patients with heart failure

BACKGROUND

Whole-body water immersion leads to a significant shift of blood from the periphery to the intrathoracic circulation, followed by an increase in central venous pressure and heart volume. In patients with severely reduced left ventricular function, this hydrostatically induced volume shift might overstrain the cardiovascular adaptive mechanisms and lead to cardiac decompensation.

AIM

To assess the haemodynamic response to water immersion, gymnastics and swimming in patients with chronic heart failure (CHF).

METHODS

10 patients with compensated CHF (62.9 (6.3) years, ejection fraction 31.5% (4.1%), peak oxygen consumption (Vo(2)) 19.4 (2.8) ml/kg/min), 10 patients with coronary artery disease (CAD) but preserved left ventricular function (57.2 (5.6) years, ejection fraction 63.9% (5.5%), peak Vo(2) 28 (6.3) ml/kg/min), and 10 healthy controls (32.8 (7.2) years, peak Vo(2) 45.6 (6) ml/kg/min) were examined. Haemodynamic response to thermoneutral (32 degrees C) water immersion and exercise was measured using a non-invasive foreign gas rebreathing method during stepwise water immersion, water gymnastics and swimming.

RESULTS

Water immersion up to the chest increased cardiac index by 19% in controls, by 21% in patients with CAD and by 16% in patients with CHF. Although some patients with CHF showed a decrease of stroke volume during immersion, all subjects were able to increase cardiac index (by 87% in healthy subjects, by 77% in patients with CAD and by 53% in patients with CHF). Vo(2) during swimming was 9.7 (3.3) ml/kg/min in patients with CHF, 12.4 (3.5) ml/kg/min in patients with CAD and 13.9 (4) ml/kg/min in controls.

CONCLUSIONS

Patients with severely reduced left ventricular function but stable clinical conditions and a minimal peak Vo(2) of at least 15 ml/kg/min during a symptom-limited exercise stress test tolerate water immersion and swimming in thermoneutral water well. Although cardiac index and Vo(2) are lower than in patients with CAD with preserved left ventricular function and controls, these patients are able to increase cardiac index adequately during water immersion and swimming.

Left ventricular chamber stiffness at rest as a determinant of exercise capacity in heart failure subjects with decreased ejection fraction

Impaired exercise tolerance, determined by peak oxygen consumption (V̇o2 peak), is predictive of mortality and the necessity for cardiac transplantation in patients with chronic heart failure (HF). However, the role of left ventricular (LV) diastolic function at rest, reflected by chamber stiffness assessed echocardiographically, as a determinant of exercise tolerance is unknown. Increased LV chamber stiffness and limitation of V̇o2 peak are known correlates of HF. Yet, the relationship between chamber stiffness and V̇o2 peak in subjects with HF has not been fully determined. Forty-one patients with HF New York Heart Association [(NYHA) class 2.4 ± 0.8, mean ± SD] had echocardiographic studies and V̇o2 peak measurements. Transmitral Doppler E waves were analyzed using a previously validated method to determine k, the LV chamber stiffness parameter. Multiple linear regression analysis of V̇o2 peak variance indicated that LV chamber stiffness k ( r2 = 0.55) and NYHA classification ( r2 = 0.43) were its best independent predictors and when taken together account for 59% of the variability in V̇o2 peak. We conclude that diastolic function at rest, as manifested by chamber stiffness, is a major determinant of maximal exercise capacity in HF.

Therapeutic exercise for individuals with heart failure: special attention to older women with heart failure

BACKGROUND

A cardinal feature of heart failure (HF) is the reduced peak aerobic power (VO(2peak)) secondary to alterations in cardiovascular and musculoskeletal function. Methods and results During the last decade, a number of randomized trials have examined the role that exercise training plays in attenuating the HF-mediated decline in VO(2peak) and muscle strength. The major finding of these investigations was that aerobic or strength training was an effective intervention to increase VO(2peak), muscular strength, distance walked in 6 minutes, and quality of life without negatively altering left ventricular systolic function. Despite these benefits, a limitation of these investigations was the primary focus on males <60 years with impaired left ventricular systolic function. Thus the role that exercise training may play in attenuating the HF-mediated decline in VO(2peak) in women > or =65 years of age remains unknown.

CONCLUSION

Older women with HF have a VO(2peak) that is below the minimal threshold level required for independent living. Moreover, older women with HF have greater disability then men and are less likely to be referred to an exercise rehabilitation program. Accordingly, future exercise intervention trials are required to examine the role that exercise training may play in attenuating the HF-mediated decline in cardiorespiratory and musculoskeletal fitness and disability in older women with HF.

Aortic distensibility independently affects exercise tolerance in patients with dilated cardiomyopathy

BACKGROUND

Peak exercise oxygen consumption (VO2) is crucial for the prognostic stratification of patients with congestive heart failure, but its hemodynamic determinants are still not completely understood. Aortic wall elasticity modulates left ventricular function and coronary blood flow. Whether an increased aortic pulse-wave velocity (PWV), a known marker of arterial stiffness, may predict peak VO2 in patients with dilated cardiomyopathy (DCM) has to be clarified.

METHODS AND RESULTS

A total of 78 patients with clinical diagnosis of DCM (aged 62+/-11 years; female 29%; mean ejection fraction 34+/-9%) were selected. All patients underwent a complete echocardiographic-Doppler evaluation. Aortic PWV was measured by Doppler ultrasonography immediately before the exercise. A bicycle exercise test with expiratory gas exchange monitoring was performed to determine VO2 . Plasma concentration of the amino-terminal propeptide of type III procollagen (PIIINP), a marker of extracellular matrix turnover, was determined. Mean PWV was 5.7+/-2.2 m/s, and VO2 was 16.5+/-4.5 mL x kg(-1) x min(-1). The hemodynamic variables correlated with VO2 were PWV (r=-0.39, P=0.0007) and stroke volume (r=0.38, P=0.002). In a multivariate analysis, PWV (P=0.04) and stroke volume (P=0.05) were independently correlated with VO2 , accounting for 34% of its variance. PIIINP levels correlated with PWV (r=0.35, P=0.002) and a more restrictive diastolic filling pattern (r=0.40, P=0.02).

CONCLUSIONS

Increased aortic stiffness measured by PWV is an independent predictor of peak VO2 and could partially explain exercise intolerance in patients with DCM.

Cardiorespiratory effects of inelastic chest wall restriction

We examined the effects of chest wall restriction (CWR) on cardiorespiratory function at rest and during exercise in healthy subjects in an attempt to approximate the cardiorespiratory interactions observed in clinical conditions that result in restrictive lung and/or chest wall changes and a reduced intrathoracic space. Canvas straps were applied around the thorax and abdomen so that vital capacity was reduced by >35%. Data were acquired at rest and during cycle ergometry at 25 and 45% of peak workloads. CWR elicited significant increases in the flow-resistive work performed on the lung (160%) and the gastric pressure-time integral (>400%) at the higher workload, but it resulted in a decrease in the elastic work performed on the lung (56%) compared with control conditions. With CWR, heart rate increased and stroke volume (SV) fell, resulting in >10% fall in cardiac output at rest and during exercise at matched workloads (P < 0.05). Blood pressure and catecholamines were significantly elevated during CWR exercise conditions (P < 0.05). We conclude that CWR significantly impairs SV during exercise and that a compensatory increase in heart rate does not prevent a significant reduction in cardiac output. O(2) consumption appears to be maintained via increased extraction and a redistribution of blood flow via sympathetic activation.

Exercise in the geriatric patient with congestive heart failure

The benefits of exercise in the elderly patient with heart failure have been well documented, but the studies have been limited by restrictive inclusion criteria. Most studies have involved patients who are younger and healthier than those normally seen in clinical practice. Improvements in neurohormonal, metabolic, and vascular status have been well documented in the relatively young patients who have been evaluated. Consequently, peak exercise time, oxygen consumption, submaximal exercise, and quality of life have also improved. Studies suggest that older, more severely limited patients may also benefit from exercise. However, they are less likely to tolerate an exercise program and may not improve their quality of life if the exercise is excessive. Caution is warranted when exercise is prescribed to elderly patients with heart failure.

[Role of rehabilitation in the treatment of chronic heart insufficiency]

Rehabilitation is an important component of the modern comprehensive care plan for patients with chronic heart failure. Cardiac rehabilitation combines exercise training with therapeutical adaptations, behavioral modifications and psychosocial interventions. Based on these data, patients with controlled heart failure should be involved in cardiac rehabilitation programs. Training prescription needs a strict previous cardiac evaluation. Exercise training monitoring must be adjusted to the physical tolerance of each patient. Cardiac rehabilitation has been found to improve functional capacity, reduce symptoms, and finally reduce cardiac morbidity and mortality. These beneficial effects were associated with muscular, endothelial and ventilatory improvements. Reduced sympathetic tone may decrease arrhythmias and may limit the progression of left ventricular dysfunction.