Pulmonary and peripheral vascular factors are important determinants of peak exercise oxygen uptake in patients with heart failure

Cardiac Rehabilitation Improves Fitness in Patients With Subclinical Markers of Cardiotoxicity While Receiving Chemotherapy: A RANDOMIZED CONTROLLED STUDY

PURPOSE

Heart failure (HF) due to cardiotoxicity is a leading non-cancer-related cause of morbidity and mortality in cancer survivors. Cardiac rehabilitation (CR) improves cardiorespiratory fitness (CRF) and reduces morbidity and mortality in patients with HF, but little is known about its effects on cardiotoxicity in the cancer population. The objective of this study was to determine whether participation in CR improves CRF in patients undergoing treatment with either doxorubicin or trastuzumab who exhibit markers of subclinical cardiotoxicity.

METHODS

Female patients with cancer (n = 28: breast, n = 1: leiomyosarcoma) and evidence of subclinical cardiotoxicity (ie, >10% relative decrease in global longitudinal strain or a cardiac troponin of >40 ng·L -1 ) were randomized to 10 wk of CR or usual care. Exercise consisted of 3 d/wk of interval training at 60-90% of heart rate reserve.

RESULTS

Cardiorespiratory fitness, as measured by peak oxygen uptake (V˙ o2peak ), improved in the CR group (16.9 + 5.0 to 18.5 + 6.0 mL∙kg -1 ∙min -1 ) while it decreased in the usual care group (17.9 + 3.9 to 16.9 + 4.0 mL∙kg -1 ∙min -1 ) ( P = .009). No changes were observed between groups with respect to high-sensitivity troponin or global longitudinal strain.

CONCLUSION

This study suggests that the use of CR may be a viable option to attenuate the reduction in CRF that occurs in patients undergoing cardiotoxic chemotherapy. The long-term effects of exercise on chemotherapy-induced HF warrant further investigation.

Carbon Monoxide Diffusing Capacity Predicts Cardiac Readmission in Patients Undergoing Left Ventricular Assist Device Implantation in Japan

Carbon monoxide diffusion capacity (DLCO) is impaired in heart failure patients; however, its clinical impact has not been well investigated in the left ventricular assist device (LVAD) population. We explored the predictive value of preoperative DLCO in the survival and cardiac readmission rates after LVAD implantation. Seventy-six patients who received continuous-flow LVAD as bridge-to-transplant therapy from November 2007 to September 2018 and underwent pulmonary function test before LVAD implantation were included. The primary study endpoints were death and readmission for heart failure or arrhythmia (cardiac readmission). Patients were stratified into two groups according to the percent of predicted DLCO (%DLCO). Pulmonary vascular resistance (PVR) was equivocal between the groups preoperatively, whereas the low DLCO group (%DLCO < 80%) showed significantly high PVR postoperatively. The mortality rate was not different between the groups. The 2 year cardiac readmission rate was 33.5% in the low DLCO group and 8.7% in the high DLCO group (%DLCO ≥ 80%) (P = 0.028). The %DLCO was associated with cardiac readmission in univariate and multivariate analyses (hazard ratio: 4.32; 95% CI: 1.50-15.9; P = 0.005). Low %DLCO was associated with high PVR postoperatively and was a risk factor for cardiac readmission after LVAD implantation.

Exercise Dynamic of Patients with Chronic Heart Failure and Reduced Ejection Fraction

PURPOSE OF REVIEW

Exercise causes various dynamic changes in all body parts either in healthy subject or in heart failure (HF) patients. The present review of current knowledge about HF patients with reduced ejection fraction focuses on dynamic changes along a "metabo-hemodynamic" perspective.

RECENT FINDINGS

Studies on the dynamic changes occurring during exercise span many years. Thanks to the availability of advanced methods, it is nowadays possible to properly characterize respiratory, hemodynamic, and muscular function adjustments and their mismatch with the pulmonary and systemic circulations. Exercise is a dynamic event that involves several body functions. In HF patients, it is important to know at what level the limitation takes place in order to better manage these patients and to optimize therapeutic strategies.

Reliability, construct validity and determinants of 6-minute walk test performance in patients with chronic heart failure

BACKGROUND

In-depth analyses of the measurement properties of the 6-minute walk test (6MWT) in patients with chronic heart failure (CHF) are lacking. We investigated the reliability, construct validity, and determinants of the distance covered in the 6MWT (6MWD) in CHF patients.

METHODS

337 patients were studied (median age 65years, 70% male, ejection fraction 35%). Participants performed two 6MWTs on subsequent days. Demographics, anthropometrics, clinical data, ejection fraction, maximal exercise capacity, body composition, lung function, and symptoms of anxiety and depression were also assessed. Construct validity was assessed in terms of convergent, discriminant and known-groups validity. Stepwise linear regression was used.

RESULTS

6MWT was reliable (ICC=0.90, P<0.0001). The learning effect was 31m (95%CI 27, 35m). Older age (≥65years), lower lung diffusing capacity (<80% predicted) and higher NYHA class (NYHA III) were associated with a lower likelihood of a meaningful increase in the second test (OR 0.45-0.56, P<0.05 for all). The best 6MWD had moderate-to-good correlations with peak exercise capacity (r_s=0.54-0.69) and no-to-fair correlations with body composition, lung function, ejection fraction, and symptoms of anxiety and depression (r_s=0.04-0.49). Patients with higher NYHA classes had lower 6MWD. 6MWD was independently associated with maximal power output during maximal exercise, estimated glomerular filtration rate and age (51.7% of the variability).

CONCLUSION

6MWT was found to be reliable and valid in patients with mild-to-moderate CHF. Maximal exercise capacity, renal function and age were significant determinants of the best 6MWD. These findings strengthen the clinical utility of the 6MWT in CHF.

Exertional dyspnoea in chronic heart failure: the role of the lung and respiratory mechanical factors

Exertional dyspnoea is among the dominant symptoms in patients with chronic heart failure and progresses relentlessly as the disease advances, leading to reduced ability to function and engage in activities of daily living. Effective management of this disabling symptom awaits a better understanding of its underlying physiology.

Cardiovascular factors are believed to play a major role in dyspnoea in heart failure patients. However, despite pharmacological interventions, such as vasodilators or inotropes that improve central haemodynamics, patients with heart failure still complain of exertional dyspnoea. Clearly, dyspnoea is not determined by cardiac factors alone, but likely depends on complex, integrated cardio-pulmonary interactions.

A growing body of evidence suggests that excessively increased ventilatory demand and abnormal “restrictive” constraints on tidal volume expansion with development of critical mechanical limitation of ventilation, contribute to exertional dyspnoea in heart failure. This article will offer new insights into the pathophysiological mechanisms of exertional dyspnoea in patients with chronic heart failure by exploring the potential role of the various constituents of the physiological response to exercise and particularly the role of abnormal ventilatory and respiratory mechanics responses to exercise in the perception of dyspnoea in patients with heart failure.

The association of cardiorespiratory fitness with endothelial or smooth muscle vasodilator function

BACKGROUND

Maximal oxygen consumption (VO2max) is strongly associated with peripheral vasodilator function as determined by exercise-induced vasodilation. However, findings with regard to its relation with non-exercise-stimulated vasodilation are unclear. The purpose of this study was to systematically review published literature reporting associations between VO2max and endothelial function (EF) or smooth muscle function (SMF).

DESIGN AND METHODS

We conducted a systematic search of MEDLINE, Cochrane and Web of Science, since their inceptions until April 2014 for articles reporting the association between (a) VO2max during incremental exercise and (b) endothelium-dependent or -independent vasodilator function, by means of correlation and/or regression analysis.

RESULTS

Fifty-six articles exploring 88 associations between VO2max and vascular EF or SMF were included, involving a total of 4159 healthy and diseased subjects. VO2max was determined by incremental cycle ergometer (64%), treadmill (33%) and cycle ergometer/treadmill (3%) exercise. Vasodilator function variables were assessed in the upper limb (86%), lower limb (10%) and both upper and lower limbs (3%). Most of the evaluated bivariate associations involved EF stimuli such as flow-mediated dilation (FMD) (n = 29) or blood flow occlusion (BFO) (n = 18). VO2max was significantly associated with FMD and BFO in 59% and 67% of bivariate associations and 46% and 33% of age-independent associations, respectively. Explored bivariate associations regarding SMF involved sodium nitroprusside (SNP) iontophoresis (n = 7) and nitrate-mediated dilation (NMD) (n = 4). VO2max was associated with NMD in 50% of bivariate associations and 50% of age-independent associations. VO2max was not associated with SNP iontophoresis. Results were similar for associations including only healthy subjects.

CONCLUSIONS

The association between VO2max and EF or SMF is moderately frequent and independent of health status, despite very few studies having assessed vasodilator function in the lower limb.

Effects of an interatrial shunt on rest and exercise hemodynamics: results of a computer simulation in heart failure

BACKGROUND

A treatment based on an interatrial shunt device has been proposed for counteracting elevated pulmonary capillary wedge pressure (PCWP) in patients with heart failure and mildly reduced or preserved ejection fraction (HFpEF). We tested the theoretical hemodynamic effects of this approach with the use of a previously validated cardiovascular simulation.

METHODS AND RESULTS

Rest and exercise hemodynamics data from 2 previous independent studies of patients with HFpEF were simulated. The theoretical effects of a shunt between the right and left atria (diameter up to 12 mm) were determined. The interatrial shunt lowered PCWP by ~3 mm Hg under simulated resting conditions (from 10 to 7 mm Hg) and by ~11 mm Hg under simulated peak exercise conditions (from 28 to 17 mm Hg). Left ventricular cardiac output decreased ~0.5 L/min at rest and ~1.3 L/min at peak exercise, with corresponding increases in right ventricular cardiac output. However, because of the reductions in PCWP, right atrial and pulmonary artery pressures did not increase. A majority of these effects were achieved with a shunt diameter of 8-9 mm. The direction of flow though the shunt was left to right in all of the conditions tested.

CONCLUSIONS

The interatrial shunt reduced left-sided cardiac output with a marked reduction in PCWP. This approach may reduce the propensity for heart failure exacerbations and allow patients to exercise longer, thus attaining higher heart rates and cardiac outputs with the shunt compared with no shunt. These results support clinical investigation of this approach and point out key factors necessary to evaluate its safety and hemodynamic effectiveness.

Exercise intolerance in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is associated with symptoms of dyspnea and fatigue, which contribute to exercise limitation. The origins and significance of dyspnea and fatigue in PAH are not completely understood. This has created uncertainly among healthcare professionals regarding acceptable levels of these symptoms, on exertion, for patients with PAH. Dysfunction of the right ventricle (RV) contributes to functional limitation and mortality in PAH; however, the role of the RV in eliciting dyspnea and fatigue has not been thoroughly examined. This paper explores the contribution of the RV and systemic and peripheral abnormalities to exercise limitation and symptoms in PAH. Further, it explores the relationship between exercise abnormalities and symptoms, the utility of the cardiopulmonary exercise test in identifying RV dysfunction, and offers suggestions for further research.

A general theory of acute and chronic heart failure

Current concepts of heart failure propose multiple heterogeneous pathophysiological mechanisms. Recently a theoretical framework for understanding chronic heart failure was suggested. This paper develops this framework to include acute heart failure syndromes. We propose that all acute heart failure syndromes may be understood in terms of a relative fall in left ventricular stroke volume. The initial compensatory mechanism is frequently a tachycardia often resulting in a near normal cardiac output. In more severe forms a fall in cardiac output causes hypotension or cardiogenic shock. In chronic heart failure the stroke volume and cardiac output is returned to normal predominantly through ventricular remodeling or dilatation. Ejection fraction is simply the ratio of stroke volume and end-diastolic volume. The resting stroke volume is predetermined by the tissue's needs; therefore, if the ejection fraction changes, the end-diastolic volume must change in a reciprocal manner. The potential role of the right heart in influencing the presentation of left heart disease is examined. We propose that acute pulmonary edema occurs when the right ventricular stroke volume exceeds left ventricular stroke volume leading to fluid accumulation in the alveoli. The possible role of the right heart in determining pulmonary hypertension and raised filling pressures in left-sided heart disease are discussed. Different clinical scenarios are presented to help clarify these proposed mechanisms and the clinical implications of these theories are discussed. Finally an alternative definition of heart failure is proposed.

Characterization of pulmonary venous hypertension patients with reactive pulmonary hypertension as compared to proportional pulmonary hypertension

BACKGROUND

Patients with pulmonary venous hypertension (PVH) secondary to left heart disease can be further classified according to their hemodynamic profile: pulmonary hypertension (PH) in proportion to the pulmonary capillary wedge pressure (PCWP) and PH out of proportion to the PCWP or reactive PH. Currently, there are no measures that enable prediction of the development of reactive PH in patients with left heart disease.

OBJECTIVES

In this study, we aim to characterize PVH patients with reactive PH as compared to proportional PH in an attempt to create a distinct profile for patients with left heart disease carrying a high risk for the development of reactive PH.

METHODS

Thirty-three PVH patients with reactive PH and 29 PVH patients with proportional PH were analyzed retrospectively over a 6-year period. Clinical, laboratory, echocardiographic and hemodynamic parameters were noted and compared between subgroups.

RESULTS

There was no significant difference between PVH patients with reactive and proportional PH with regard to gender, age (65.91 ± 11.9 vs. 66.69 ± 10.5 years) and body surface area (1.89 ± 0.24 vs. 1.9 ± 0.23 m(2)). Prevalence of the metabolic syndrome components was similar in both groups. Interestingly, PCWP was similar in both groups, as were the structural and functional parameters of the left heart.

CONCLUSIONS

PVH patients with reactive PH have a similar profile as patients with proportional PH; consequently, the evolution of reactive PH is unpredictable. Therefore, it is imperative that physicians maintain a high index of suspicion for the development of reactive PH even in the early stage of heart disease.

Dose-dependent effects of omega-3-polyunsaturated fatty acids on systolic left ventricular function, endothelial function, and markers of inflammation in chronic heart failure of nonischemic origin: a double-blind, placebo-controlled, 3-arm study

BACKGROUND

Supplementation with 1 g/d omega-3-polyunsaturated fatty acids (n3-PUFAs) demonstrated a small survival advantage in patients with chronic heart failure (CHF) in the GISSI-HF trial. However, a dose-efficacy relationship was postulated for the beneficial effects of n3-PUFA before. Therefore, we evaluated dose-dependent effects of n3-PUFA in patients with severe CHF.

METHODS

In a double-blind, randomized, controlled pilot trial, 43 patients with severe, nonischemic heart failure received 1 g/d n3-PUFA (n = 14), 4 g/d n3-PUFA (n = 13), or placebo (n = 16) for 3 months. Changes in left ventricular ejection fraction (LVEF), flow-mediated vasodilation, plasma high-sensitive interleukin 6 and high-sensitive tumor necrosis factor α, and exercise peak oxygen consumption were assessed.

RESULTS

Left ventricular ejection fraction increased in a dose-dependent manner (P = .01 for linear trend) in the 4 (baseline vs 3 months [mean ± SD]: 24% ± 7% vs 29% ± 8%, P = .005) and 1 g/d treatment groups (24% ± 8% vs 27% ± 8%, P = .02). Flow-mediated vasodilation increased significantly with high-dose 4 g/d n3-PUFA (8.4% ± 4.8% vs 11.6% ± 7.0%, P = .01) but only trendwise with low-dose 1 g/d (8.3% ± 5.3% vs 10.2% ± 4.3%, P = .07). Interleukin 6 significantly decreased with 4 g/d n3-PUFA (3.0 ± 2.9 pg/mL vs 0.7 ± 0.8 pg/mL, P = .03) but only trendwise with 1 g/d (4.5 ± 6.6 pg/mL to 1.6 ± 2.1 pg/mL, P = .1). High-sensitive tumor necrosis factor α decreased trendwise with 4 g/d n3-PUFA but remained unchanged with 1 g/d. In patients with maximal exercise effort, only 4 g/d increased the peak oxygen consumption. No changes in any investigated parameters were noted with placebo.

CONCLUSION

Treatment with n3-PUFA for 3 months exerts a dose-dependent increase of LVEF in patients with CHF. In parallel, a significant improvement of endothelial function and decrease of interleukin 6 is found with high-dose n3-PUFA intervention.

Resting lung function in the assessment of the exercise capacity in patients with chronic heart failure

BACKGROUND

Despite the lung involvement in patients with chronic heart failure (CHF), the significance of lung function abnormalities to functional status in these patients is still controversial. We postulated that in patients with CHF, resting lung function assessment may provide information of clinical relevance on exercise capacity, expressed as peak oxygen uptake (VO2) and ventilatory response to CO2 production (VE/VCO2) during a maximal exercise.

METHODS

We studied 49 clinically stable patients with CHF (38 men, age range: 25-78 years) (New York Heart Association class range: I-IV) with left ventricular ejection fraction <40%. Patients with chronic obstructive pulmonary disease were excluded. Patients performed pulmonary function tests and maximal incremental exercise test.

RESULTS

Resting spirometry was related to the exercise capacity (P < 0.05), expressed as peak VO2. By means of receiver operating characteristic curve analysis, the forced expiratory volume at first second (FEV1) cutoff point, which better identified patients with a peak VO2 < or =14 mL/kg/min, was <79% of predicted value (0.79 sensitivity and 0.73 specificity). Resting lung diffusion capacity for carbon monoxide and end-tidal pressure of CO2 (PETCO2) were inversely correlated to VE/VCO2 (P < 0.01). The lung diffusion capacity for carbon monoxide and PETCO2 cutoff points, which better identified patients with VE/VCO2 value >34, were <58% of predicted (0.92 sensitivity and 0.42 specificity) and <33 mm Hg (0.67 sensitivity and 0.92 specificity), respectively.

CONCLUSIONS

In patients with CHF, resting lung function, including spirometry, lung diffusion capacity, and PETCO2, can provide clinically useful information on exercise capacity, by predicting peak VO2 and VE/VCO2 slope. The results of this study highlight the role of resting lung function in the assessment of the functional status of cardiac patients.

Correlations between respiratory and functional variables in heart failure

BACKGROUND

Respiratory alterations can impact on the functional performance of patients with heart failure.

AIM

To correlate maximum inspiratory muscular force and lung function variables with functional capacity in heart failure patients.

METHODS

A transversal study January-July 2007 with 42 chronic heart disease patients (28 males) with no prior pulmonary illness. The patients were in New York Heart Association Functional Class I, II and III. The variables used were maximum inspiratory pressure, forced vital capacity and forced expiratory volume in the first second. Respiratory variables measured were distance covered in the six-minute walk test, NYHA functional class and the physical functioning domain of the Short Form-36 Quality of Life Questionnaire.

RESULTS

Maximum inspiratory pressure correlated with the six-minute walk test (r=0.543 and p<0.001), functional capacity (r=-0.566 and p<0.001) and the physical functioning domain score of the Short Form- 36 (r=0.459 and p=0.002). The same was true of forced vital capacity and the six-minute walk test (r=0.501 and p=0.001), functional capacity (r=-0.477 and p=0.001) and Short Form-36 (r=0.314 and p=0.043) variables. Forced expiratory volume correlated with the distance covered in the six-minute walk test (r=0.514 and p<0.001) and functional capacity (r=-0.383 and p=0.012).

CONCLUSION

Lung function and inspiratory muscular force respiratory variables correlated with functional variables in patients with heart failure.

Endothelium-dependent and -independent vasodilation is more attenuated in ischaemic than in non-ischaemic heart failure

AIMS

Endothelial dysfunction in chronic heart failure (CHF) contributes to vasoconstriction. Underlying atherosclerosis may increase vascular abnormalities in ischaemic CHF. We aimed to compare flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) of the brachial artery between patients with ischaemic and non-ischaemic CHF.

METHODS AND RESULTS

A total of 57 patients with systolic CHF participated in the study (mean age 59 +/- 8 years, 81% male). Patients were in stable NYHA class II (40 patients, 70%) and III (17 patients, 30%). Ischaemic aetiology of CHF was confirmed by coronary angiography in 34 (60%) patients and ruled out in 23 (40%). Flow-mediated dilation and NMD of the brachial artery was assessed by high-resolution ultrasound. Endothelium-dependent vasodilation was markedly reduced in patients with ischaemic CHF compared with those with non-ischaemic aetiology of CHF-mean absolute change in artery diameter (Deltad) 0.09 +/- 0.07 mm in ischaemic group vs. 0.18 +/- 0.07 mm in non-ischaemic (P < 0.0001). Nitroglycerin-mediated vasodilation was also significantly different-Deltad = 0.14 +/- 0.06 mm in ischaemic vs. 0.31 +/- 0.10 mm in non-ischaemic CHF (P < 0.0001).

CONCLUSION

Endothelium-dependent and -independent vascular response is more attenuated in ischaemic than in non-ischaemic CHF.

Reduced surface tension normalizes static lung mechanics in a rodent chronic heart failure model

RATIONALE

Chronic elevation of pulmonary microvascular pressure in chronic heart failure results in compensatory changes in the lung that reduce alveolar fluid filtration and protect against pulmonary microvascular rupture.

OBJECTIVES

To determine whether these compensatory responses may have maladaptive effects on lung function.

METHODS

Six weeks after myocardial infarction (chronic heart failure model) rat lung composition, both gross and histologic; air and saline mechanics; surfactant production; and immunological mediators were examined.

MEASUREMENTS AND MAIN RESULTS

An increase in dry lung weight, due to increased insoluble protein, lipid and cellular infiltrate, without pulmonary edema was found. Despite this, both forced impedance and air pressure-volume mechanics were normal. However, there was increased tissue stiffness in the absence of surface tension (saline pressure-volume curve) with a concurrent increase in both surfactant content and alveolar type II cell numbers, suggesting a novel homeostatic phenomenon.

CONCLUSIONS

These studies suggest a compensatory reduction in pulmonary surface tension that attenuates the effect of lung parenchymal remodeling on lung mechanics, hence work of breathing.

Pulmonary surfactant protein B in the peripheral circulation and functional impairment in patients with chronic heart failure

INTRODUCTION AND OBJECTIVES

Surfactant protein B (SP-B) is a marker of damage to the alveolar-capillary barrier that could be useful for monitoring functional impairment in patients with chronic heart failure (HF).

METHODS

Dyspnea-limited cardiopulmonary exercise testing was carried out in 43 outpatients with chronic HF (age 51+/-10 years, 77% male, left ventricular ejection fraction [LVEF] 33+/-11%). Peripheral blood serum samples were obtained at rest and during the first minute of peak exercise. The presence and concentration of SP-B in the serum samples were determined by Western blot analysis.

RESULTS

At rest, SP-B was detected in 35 (82%) patients compared with only six (23%) healthy volunteers in a control group (n=26, age 51+/-10 years, 77% male). The median circulating SP-B level was higher in HF patients, at 174 [interquartile range, 70-283] vs. 77 [41-152] (P< .001) in the control group. In HF patients, the presence of circulating SP-B was associated with a lower LVEF (31.4+/-9.6% vs. 41.8+/-15%; P=.01). Multivariate analysis showed that the resting SP-B level correlated with a greater VE/VCO2 slope (beta=1.45; P=.02). The peak-exercise SP-B level correlated almost perfectly with the resting level (r=0.980; P< .001), but there was no significant increase with exercise (P=.164). Nor was there a correlation with any other exercise parameter.

CONCLUSIONS

In patients with chronic HF, the level of pulmonary surfactant protein B in the peripheral circulation is increased and is correlated with ventilatory inefficiency during exercise, as indicated by the VE/VCO2 slope.

Six minute walk test: a simple and useful test to evaluate functional capacity in patients with heart failure

In heart failure survival is closely related to functional capacity. Peak O2 consumption at cardiopulmonary exercise test (CPET) is considered the gold standard for the evaluation of exercise tolerance. Since >70% of patients with heart failure, usually elderly or with significant comorbidities, are referred to Departments of Internal Medicine where facilities for cardiopulmonary test are rarely available, CPET may be performed in <5% of the patients. Six-minute walk test (6MWT) has been proposed as a simple, inexpensive, reproducible alternative to CPET. The 6MWT reproduces the activity of daily life and this is particularly relevant in elderly patients who usually develop symptoms below their theoretical maximal exercise capacity. Despite some limits 6MWT is attractive for patients referred to Departments of Internal Medicine allowing an objective evaluation of exercise tolerance, a better prognostic evaluation and a guide to evaluate response to medical treatment.

Alveolar gas diffusion abnormalities in heart failure

In heart failure (HF), development of pressure or volume overload of the lung microcirculation elicits a series of structural adaptations, whose functional correlate is an increased resistance to gas transfer across the alveolar-capillary membrane. Acutely, hydrostatic mechanical injury causes endothelial and alveolar cell breaks, impairment of the cellular pathways involved in fluid filtration and reabsorption, and resistance to gas transfer. This process, which is reminiscent of the so-called alveolar-capillary stress failure, is generally reversible. When the alveolar membrane is chronically challenged, tissue alterations are sustained and a typical remodeling process may take place that is characterized by fixed extracellular matrix collagen proliferation and reexpression of fetal genes. Remodeling leads to a persistent reduction in alveolar-capillary membrane conductance and lung diffusion capacity. Changes in gas transfer not only reflect the underlying lung tissue damage but also bring independent prognostic information and may play a role in the pathogenesis of exercise limitation and ventilatory abnormalities. They are not responsive to fluid withdrawal by ultrafiltration and tend to be refractory even to heart transplantation. Some drugs can be effective that modulate lung remodeling (eg, angiotensin-converting enzyme inhibitors, whose impact on the natural course of cardiac remodeling is well known) or that increase nitric oxide availability and nitric oxide-mediated pulmonary vasodilation (eg, type 5 phosphodiesterase inhibitors). This review focuses on the current knowledge of these topics.

Ventricular-vascular interaction in heart failure

Nearly half of all patients who have heart failure have preserved ejection fraction (HFpEF). Patients who have HFpEF tend to be older, female, and hypertensive, and characteristically display increased ventricular and arterial stiffening. In this article, we discuss the pathophysiology of abnormal ventriculoarterial stiffening and how it affects ventricular function, cardiovascular hemodynamics, reserve capacity, and symptoms. We conclude by exploring how novel treatment strategies targeting abnormal ventricular-arterial interaction might prove useful in the treatment of patients who have HFpEF.

Alveolar-capillary membrane conductance is the best pulmonary function correlate of exercise ventilation efficiency in heart failure patients

BACKGROUND

In heart failure (HF), changes in lung mechanics and gas diffusion are limiting factors to exercise. Their contribution to an increased exercise ventilation to CO2 production (VE/VCO2) slope is undefined.

METHODS

A total of 67 stable HF patients underwent cardiopulmonary exercise and pulmonary function tests, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), maximal voluntary ventilation (MVV), total lung capacity (TLC) and alveolar diffusing capacity with its subcomponents (alveolar-capillary membrane conductance (D(m)) and capillary blood volume (V(c))).

RESULTS

Patients showed a mild restrictive pattern (FEV1=85+/-15% and FVC=75+/-13% of normal predicted) and a moderate D(m) reduction (32+/-12 ml min(-1) mm Hg(-1)). Average peak VO(2) was 15.6+/-4.0 ml min(-1) kg(-1) and the VE/VCO2 slope was 39.6+/-11.0. At simple Spearman correlation analysis, all variables, but V(c), correlated with peak VO2; only D(m) correlated with VE/VCO2 slope. At partial Spearman correlation, all variables lost the peak VO2 correlation, and D(m) still inversely correlated with VE/VCO2 slope (r=-0.35; p=0.005). In patients with a high VE/VCO2 slope (cutoff value 34), despite comparable lung volumes, D(m) was significantly more depressed (30+/-13 vs. 35+/-10 ml min(-1) mm Hg(-1); p<0.01).

CONCLUSIONS

Pulmonary function tests and alveolar gas diffusing capacity poorly correlate with peak VO2. D(m) impairment rather than lung volumes correlates with exercise ventilation efficiency. This finding further adds to the pathophysiological relevance of an abnormal gas exchange in HF patients.

Why does chronic heart failure cause breathlessness and fatigue?

Traditional explanations for the symptoms of fatigue and breathlessness experienced by patients with chronic heart failure (CHF) focus on how reduced cardiac output on exercise leads to impaired skeletal muscle blood supply, thus causing fatigue, and on how the requirement for a raised left ventricular filling pressure to maintain cardiac output results in reduced pulmonary diffusion owing to interstitial edema, thus causing breathlessness. However, indices of left ventricular function relate poorly to exercise capacity and symptoms, suggesting that the origin of symptoms may lie elsewhere. There is a specific heart failure myopathy that is present early in the condition which may contribute largely to the sensation of fatigue. Receptors present in skeletal muscle sensitive to work (ergoreceptors) are overactive in patients with CHF, presumably as a consequence of the myopathy, and their activity is related both to the ventilatory response to exercise and breathlessness, and to the sympathetic overactivity of CHF. In the present paper, we review the systemic consequences of left ventricular dysfunction to understand how they relate to the symptoms of heart failure.

Current clinical applications of spectral tissue Doppler echocardiography (E/E' ratio) as a noninvasive surrogate for left ventricular diastolic pressures in the diagnosis of heart failure with preserved left ventricular systolic function

Congestive heart failure with preserved left ventricular systolic function has emerged as a growing epidemic medical syndrome in developed countries, which is characterized by high morbidity and mortality rates. Rapid and accurate diagnosis of this condition is essential for optimizing the therapeutic management. The diagnosis of congestive heart failure is challenging in patients presenting without obvious left ventricular systolic dysfunction and additional diagnostic information is most commonly required in this setting. Comprehensive Doppler echocardiography is the single most useful diagnostic test recommended by the ESC and ACC/AHA guidelines for assessing left ventricular ejection fraction and cardiac abnormalities in patients with suspected congestive heart failure, and non-invasively determined basal or exercise-induced pulmonary capillary hypertension is likely to become a hallmark of congestive heart failure in symptomatic patients with preserved left ventricular systolic function. The present review will focus on the current clinical applications of spectral tissue Doppler echocardiography used as a reliable noninvasive surrogate for left ventricular diastolic pressures at rest as well as during exercise in the diagnosis of heart failure with preserved left ventricular systolic function. Chronic congestive heart failure, a disease of exercise, and acute heart failure syndromes are characterized by specific pathophysiologic and diagnostic issues, and these two clinical presentations will be discussed separately.

Effect of physical training on exercise capacity, gas exchange and N-terminal pro-brain natriuretic peptide levels in patients with chronic heart failure

BACKGROUND

Decreased exercise capacity is the main factor restricting the daily life of patients with chronic heart failure. N-terminal pro-brain natriuretic peptide (NT pro-BNP) is strongly related to the severity of and is an independent predictor of outcome in chronic heart failure.

DESIGN

The study aimed to evaluate the effect of exercise training on functional capacity and on changes in NT pro-BNP levels and to assess the effect of exercise training on quality of life.

MATERIALS AND METHODS

Sixty patients (45 men/15 women, mean age 52.7 years; +/-5.3 SD), with stable heart failure (45 ischaemic/hypertensive and 15 idiopathic patients), in New York Heart Association (NYHA) functional class II (n=35) to III (n=25), with an ejection fraction less than 40%, were randomly assigned to a training (n=30) and a control group (n=30). The training group (30 patients) performed 3 months of supervised physical training programme using a bicycle ergometer for 30 min three times a week at a load corresponding to 60-70% of their oxygen consumption (VO2) peak. The control group did not change their previous physical activity. A graded maximal exercise test with respiratory gas analysis and an endurance test with constant workload corresponding to 85% of the peak oxygen load at the baseline and after 3 months were performed, and at the same times NT pro-BNP levels were measured.

RESULTS

The exercise capacity increased from 15.8 (+/-2.3 SD) to 29.9 (+/-2.1 SD) min (P<0.0001) and the peak VO2 tended to improve from 14.5 (+/-1.4 SD) to 17.7 (+/-2.6 SD) ml/kg per min (P<0.0001) during the supervised training period. VO2 at the anaerobic threshold increased from 12.9 (+/-1.0 SD) to 15.5 (+/-1.7 SD) ml/kg per min (P<0.0001). NT pro-BNP levels decreased from 3376 (+/-3133 SD) to 1434 (+/-1673 SD) pg/ml (P=0.043). The positive training effects were associated with an improvement in the NYHA functional class.

CONCLUSION

Physical training of moderate intensity significantly improves the exercise capacity and neurohormonal modulation in patients with chronic heart failure. This is associated with an alleviation of symptoms and improvement in quality of life.

Vasoconstrictive Response in the Vascular Beds of the Non-Exercising Forearm During Leg Exercise in Patients With Mild Chronic Heart Failure

BACKGROUND

Reduced exercise capacity may be related to decreased redistribution of blood flow from the non-exercising tissues to the exercising skeletal muscle in patients with mild chronic heart failure (CHF).

METHODS AND RESULTS

In the present study 14 patients with mild CHF and 10 healthy subjects (N) underwent symptom-limited multistage-ergometer exercise, during which forearm vascular resistance (FVR), cardiac index (CI), systemic vascular resistance index (SVRI), and oxygen uptake (VO(2)) were measured non-invasively using the plethysmograph, impedance, and respiratory gas analysis methods, respectively. The VO(2) and CI at peak exercise were lower (p<0.01 each), and SVRI and FVR at both rest and peak exercise were higher in the CHF group than in N. However, both the percent increase in FVR and percent decrease in SVRI from the resting state to peak exercise were lower in CHF than N, and both of them correlated with not only peak VO(2), but also the corresponding resting value of FVR and SVRI (p<0.01 each).

CONCLUSIONS

Redistribution of blood flow from the non-exercising tissues to the working skeletal muscles, which may participate in exercise capacity, can be blunted in CHF. The decreased vasoconstrictive response in the non-exercising tissues is intimately related to the increased resting vascular tone in CHF.

Effects of continuous positive airway pressure on pulmonary function and exercise tolerance in patients with congestive heart failure

STUDY OBJECTIVES

Continuous positive airway pressure (CPAP) has been used to improve cardiopulmonary function and reduce pulmonary edema symptoms in patients with congestive heart failure (CHF). The objective of this study was to evaluate the efficacy of CPAP therapy on pulmonary function and exercise tolerance in patients with CHF.

DESIGN

Prospective blind randomized clinical study.

PARTICIPANTS

Twenty-four patients with class II or III CHF and dilated cardiomyopathy were randomly assigned to 30 min of CPAP therapy and respiratory exercises (CPAP group) or respiratory exercise only (control group) once a day for 14 days.

MEASUREMENTS AND RESULTS

Evaluation of pulmonary function was performed measuring FEV1 and FVC. Exercise tolerance was assessed measuring the distance walked during the 6-min walking test (6MWT). These parameters were measured before treatment and 4 days, 9 days, and 14 days later. CPAP therapy caused a progressive increase (p < 0.05) in both FVC (maximum of 16% after 9 days) and FEV1 (maximum of 14% after 14 days) compared to basal values, without significant changes in the control group. The 6MWT showed a progressive improvement in the distance walked in the CPAP group, reaching approximately 28% above the basal values in the CPAP group and without significant changes in the control group.

CONCLUSIONS

These data show that the use of CPAP therapy for 2 weeks on a daily basis is able to enhance pulmonary function and consequently improve the tolerance to physical activities in patients with CHF. The clinical implication of this finding is that CPAP therapy could potentially be used as an adjunct to the treatment of CHF patients.

Incidence and risk distribution of heart failure in adolescents and adults with congenital heart disease after cardiac surgery

Heart failure (HF) is a major problem in the long-term follow-up of adults with congenital heart disease (CHD) after cardiac surgery. The purpose of this study was to evaluate risk factors for HF in patients with CHD. N-terminal-pro-brain natriuretic peptide and maximal oxygen uptake (VO2max) were measured in 345 consecutive patients with CHD. HF was defined as an elevated N-terminal-pro-brain natriuretic peptide level (> or = 100 pg/ml) and reduced VO2max (< or = 25 ml/kg/min). The HF criteria were met by 89 patients. These patients were significantly older (mean +/- SEM 30.8 +/- 0.9 vs 24.8 +/- 0.5 years), had significantly lower maximal heart rates (149 +/- 3 vs 164 +/- 1 beats/min), and had larger end-diastolic right ventricular diameters (36 +/- 1 vs 27 +/- 1 mm) and right ventricular pressure estimated by Doppler flow velocities of tricuspid valve regurgitation (2.9 +/- 0.1 vs 2.3 +/- 0.03 m/s). Mean fractional shortening of the left ventricle was within the normal range. To estimate risk stratification, odds ratios for HF were determined for the most frequently occurring types of congenital heart defects and surgical procedures. In conclusion, HF in adults with CHD predominately depends on diagnosis, age, the frequency of reoperation, and right ventricular function and may be related to chronotropic incompetence indicated by lower maximal heart rates.

Poor Relationship Between Exercise Capacity and Spirometric Measurements in Patients With More Symptomatic Heart Failure

BACKGROUND

The origin of exercise limitation in patients with chronic heart failure (CHF) is multifactorial, and the relative contributions of different abnormalities may vary with severity of heart failure symptoms. The aim of the current study was to determine the extent to which spirometric indices predict peak exercise capacity in patients with differing severity of symptoms.

METHODS AND RESULTS

A total of 340 patients with left ventricular systolic dysfunction underwent spirometry, and a ramped, maximal exercise treadmill test with metabolic gas exchange measurements. For comparative purposes, a group of 174 aged-matched controls with no major structural heart disease (MSHD) was also included. In a stepwise linear regression model, forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were independent predictors of peak oxygen uptake (pVO2) in controls (r2= 18-25%; P = .001) and New York Heart Association (NYHA) I-II patients (r2= 16-18%; P = .001). No association between spirometric indices (FEV1/FVC) and pVO2 (r2= 1-2%; P > .05) was found in NYHA III-IV patients.

CONCLUSION

In aged-matched controls with no MSHD, spirometric variables (FEV1/FVC) explain 18% to 25% of the variance in pVO2, and 16% to 18% of the variance in patients with NYHA class I-II symptoms. As symptoms worsen, the influence of spirometric variables on peak exercise capacity diminishes, and there is no such relation in the NYHA class III-IV patients.

β-Blockers and Inspiratory Pulmonary Function in Chronic Heart Failure

BACKGROUND

Chronic heart failure (CHF) patients complain of breathlessness and fatigue. Respiratory muscle function is impaired in CHF patients and may contribute to their symptoms. Beta-blockers cause fatigue but have become part of the standard management of CHF. We explored the relation between respiratory muscle power in CHF and the effects of long-term beta-blockade.

METHODS AND RESULTS

A total of 52 CHF patients and 25 control subjects underwent echocardiography, peak exercise testing with metabolic gas exchange analysis, and measurement of forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak inspiratory flow (PIF), and forced inspiratory volume in 1 second (FIV1). Of the patients, 35 started beta-blocker therapy and were tested again at 1 year. Patients had lower peak oxygen consumption (pV(O2) (19.3 [4.5] versus 37.3 [8.4] mL/kg/min, P < .0001), exercise time (414 [134] versus 817 [193] seconds, P < .0001), and anaerobic threshold (13.8 [3.8] versus 27.2 [8.2] mL/kg/min, P < .0001). Patients also had a steeper relationship between ventilation (V(E)) and carbon dioxide (CO2 ) (V(E)/V(CO2)) (40.0 [6.8] versus 26.4 [2.0], P < .0001); lower FEV1, FVC, and FIV1 (89 [15] versus 111 [24]% expected, P < .0001, 80 [20] versus 94 [21]% expected, P < .001 and 2.5 [1.6] versus 3.0 (0.9) L, P < .02); and there was a correlation between pV(O2) and FIV1 (r = 0.24, P < .05) for the patients. The slope relating symptoms of breathlessness (Borg score) to ventilation (Borg/V(E) slope) also correlated with FIV1 (r = 0.36, P < .02). Beta-blocker therapy improved echocardiographic variables, but not pV(O2). There was no change in PIF or FIV1. There was a significant reduction in FEV 1 after beta-blocker treatment (P < .01).

CONCLUSION

Inspiratory flows are impaired in patients with chronic heart failure and correlate with the degree of functional impairment. This may be due to a combination of respiratory muscle weakness and reduced lung compliance. The reduction in inspiratory capacity is not influenced by long-term beta-blockade.

Impact of medical treatment on lung diffusion capacity in elderly patients with heart failure. Baseline characteristics and 1-year follow up after medical treatment

AIM

The aim of this investigation was (1) to study the effect of untreated chronic heart failure (CHF) on alveolar membrane diffusion capacity (transfer coefficient, K(CO)) in elderly patients and (2) to study the impact of the standard regime of medical treatment with diuretics and ACE-inhibitor/angiotensin-II receptor antagonists on K(CO) in these patients.

METHODS

Non-medicated patients (except for diuretics) with symptoms of heart failure (NYHA II-III) and echocardiographically estimated left ventricular ejection fraction (LVEF) <0.40 were recruited. All were characterized according to the results of multiple ECG-gated radionuclide ventriculography (MUGA). LVEF<0.50 when measured by MUGA was considered as heart failure (HF). A total of 20 patients fulfilled the criteria. All patients had a lung function test including measurement of K(CO) and a MUGA for LVEF measurement performed prior to medical treatment (baseline) and after 1 year of treatment with diuretics and ACE-inhibitors/angiotensin-II receptor antagonists. Age- and gender-matched healthy volunteers were included as control group.

RESULTS

(mean+/-S.E.M.): K(CO) at baseline was 0.95+/-0.06 and 1.25+/-0.04 mmol/min x kPa/l in HF patients and controls, respectively (p<0.05). After 1 year of treatment, K(CO) was normalized in the HF group (1.23+/-0.13 mmol/s x kPa, p<0.05). LVEF increased in the HF group from 0.28+/-0.03 at baseline to 0.34+/-0.03 after 1 year of treatment (p<0.05).

CONCLUSION

Elderly patients with symptomatic HF (NYHA II-III) and reduced systolic function have respiratory dysfunction in the form of reduced K(CO). One year of medical treatment had a significant beneficial effect on K(CO) and LVEF.

The reversibility of increased airways resistance in chronic heart failure measured by impulse oscillometry

BACKGROUND

Patients with chronic heart failure complain of breathlessness and fatigue on exercise. Airways resistance is increased and lung compliance is reduced in chronic heart failure patients. The aim of this study was to determine whether the pulmonary abnormalities are reversible and whether any improvements lead to changes to exercise capacity or symptoms.

METHODS

Twelve patients with stable chronic heart failure and 10 matched controls underwent repeated assessment of airways resistance using impulse oscillometry and peak exercise testing with metabolic gas exchange after receiving nebulized saline as placebo or combined salbutamol and ipratropium bromide in a double-blind crossover randomized fashion.

RESULTS

Patients had lower peak oxygen consumption and a steeper slope relating ventilation to carbon dioxide production than controls. Bronchodilators reduced peripheral airways resistance in patients (0.53 versus 0.38, P<.02) and controls (0.21 versus 0.19, P<.005) and increased measures of compliance in both groups. There was no effect on the peak oxygen consumption, exercise time, ventilation to carbon dioxide slope, or anaerobic threshold. There was an increase in peak tidal volume (VT) in both groups but this did not lead to an increase in peak ventilation. The slope relating symptoms to ventilation (ie, Borg/VE) was significantly reduced in the patients after bronchodilators (17%+/-8%, P<.05). The relationship between the improvement in VT and reduction in gradient of the Borg/VE slope was significant (r=.40, P<.05).

CONCLUSIONS

Nebulized bronchodilators improve airways resistance, lung reactance, and peak tidal volume during exercise in chronic heart failure but do not increase peak exercise capacity. They do, however, reduce the symptom of breathlessness.

Effect of exercise training on endothelium-derived nitric oxide function in humans

Vascular endothelial function is essential for maintenance of health of the vessel wall and for vasomotor control in both conduit and resistance vessels. These functions are due to the production of numerous autacoids, of which nitric oxide (NO) has been the most widely studied. Exercise training has been shown, in many animal and human studies, to augment endothelial, NO-dependent vasodilatation in both large and small vessels. The extent of the improvement in humans depends upon the muscle mass subjected to training; with forearm exercise, changes are restricted to the forearm vessels while lower body training can induce generalized benefit. Increased NO bioactivity with exercise training has been readily and consistently demonstrated in subjects with cardiovascular disease and risk factors, in whom antecedent endothelial dysfunction exists. These conditions may all be associated with increased oxygen free radicals which impact on NO synthase activity and with which NO reacts; repeated exercise and shear stress stimulation of NO bioactivity redresses this radical imbalance, hence leading to greater potential for autacoid bioavailability. Recent human studies also indicate that exercise training may improve endothelial function by up-regulating eNOS protein expression and phosphorylation. While improvement in NO vasodilator function has been less frequently found in healthy subjects, a higher level of training may lead to improvement. Regarding time course, studies indicate that short-term training increases NO bioactivity, which acts to homeostatically regulate the shear stress associated with exercise. Whilst the increase in NO bioactivity dissipates within weeks of training cessation, studies also indicate that if exercise is maintained, the short-term functional adaptation is succeeded by NO-dependent structural changes, leading to arterial remodelling and structural normalization of shear. Given the strong prognostic links between vascular structure, function and cardiovascular events, the implications of these findings are obvious, yet many unanswered questions remain, not only concerning the mechanisms responsible for NO bioactivity, the nature of the cellular effect and relevance of other autacoids, but also such practical questions as the optimal intensity, modality and volume of exercise training required in different populations.

Exercise and the nitric oxide vasodilator system

In the past two decades, normal endothelial function has been identified as integral to vascular health. The endothelium produces numerous vasodilator and vasoconstrictor compounds that regulate vascular tone; the vasodilator, nitric oxide (NO), has additional antiatherogenic properties, is probably the most important and best characterised mediator, and its intrinsic vasodilator function is commonly used as a surrogate index of endothelial function. Many conditions, including atherosclerosis, diabetes mellitus and even vascular risk factors, are associated with endothelial dysfunction, which, in turn, correlates with cardiovascular mortality. Furthermore, clinical benefit and improved endothelial function tend to be associated in response to interventions. Shear stress on endothelial cells is a potent stimulus for NO production. Although the role of endothelium-derived NO in acute exercise has not been fully resolved, exercise training involving repetitive bouts of exercise over weeks or months up-regulates endothelial NO bioactivity. Animal studies have found improved endothelium-dependent vasodilation after as few as 7 days of exercise. Consequent changes in vasodilator function appear to persist for several weeks but may regress with long-term training, perhaps reflecting progression to structural adaptation which may, however, have been partly endothelium-dependent. The increase in blood flow, and change in haemodynamics that occur during acute exercise may, therefore, provide a stimulus for both acute and chronic changes in vascular function. Substantial differences within species and within the vasculature appear to exist. In humans, exercise training improves endothelium-dependent vasodilator function, not only as a localised phenomenon in the active muscle group, but also as a systemic response when a relatively large mass of muscle is activated regularly during an exercise training programme. Individuals with initially impaired endothelial function at baseline appear to be more responsive to exercise training than healthy individuals; that is, it is more difficult to improve already normal vascular function. While improvement is reflected in increased NO bioactivity, the detail of mechanisms, for example the relative importance of up-regulation of mediators and antioxidant effects, is unclear. Optimum training schedules, possible sequential changes and the duration of benefit under various conditions also remain largely unresolved. In summary, epidemiological evidence strongly suggests that regular exercise confers beneficial effects on cardiovascular health. Shear stress-mediated improvement in endothelial function provides one plausible explanation for the cardioprotective benefits of exercise training.

The effects of alpha and beta blockade on ventilatory responses to exercise in chronic heart failure

OBJECTIVE

To assess the influence of acute alpha and beta blockade on ventilation and symptoms of breathlessness during exercise in patients with chronic heart failure and in controls.

METHODS

11 patients with chronic heart failure and 11 control subjects underwent repeated exercise testing with metabolic gas exchange after random, double blind administration of either an alpha blocker and placebo, a beta blocker and a placebo, both an alpha blocker and a beta blocker, or double placebo.

RESULTS

Patients had a lower peak oxygen consumption (mean (SD) 20.7 (4.9) v 37.6 (9.6) ml/kg/min, p < 0.0001) and a steeper slope relating ventilation to carbon dioxide production (VE/CO2 slope) (26.5 (4.1) v 37.1 (8.2), p = 0.0011), than controls. Blood pressure was lower following alpha and beta blockade (p < 0.05) and the gradients of the slopes relating heart rate to oxygen consumption following the beta blocker were reduced (p < 0.05). Exercise time and peak ventilatory variables following beta or alpha blockers were unchanged. Ventilation was reduced during submaximal exercise following the active medications. Combined alpha and beta blockade produced the greatest difference (p < 0.005), but the alpha and beta blockers alone also reduced ventilation (p < 0.05). There was no difference in perceived exertion during exercise with any of the treatments.

CONCLUSION

Acute sympathetic inhibition can reduce submaximal ventilation during exercise in patients with heart failure and control subjects, suggesting that autonomic nervous system activation has an important role in the abnormal ventilatory response to exercise in chronic heart failure.

Alveolar-capillary membrane dysfunction in heart failure: evidence of a pathophysiologic role

Chronic heart failure (CHF) increases the resistance to gas transfer across the alveolar-capillary interface. Recent reports highlight the pathophysiologic relevance of changes in the lung leading to impaired fluid and gas exchange in the distal airway spaces. Under experimental conditions, an acute pressure or volume overload can injure the alveolar blood-gas barrier. This may disrupt its anatomic configuration, cause the loss of regulation of fluid-flux, and thereby affect alveolar gas conductance properties. These ultrastructural changes have been identified under the term of stress failure of the alveolar-capillary membrane. In the short term, these alterations are reversible due to the reparative properties of the alveolar surface. However, when the alveolar-capillary membrane is chronically challenged, for instance in patients with CHF, by noxious stimuli, such as humoral, cytotoxic, and genetic factors other than by mechanical trauma, remodeling of pathophysiologic and clinical importance may take place. These changes in some respects resemble the remodeling process in the heart. Emerging findings support the view that, in patients with CHF, alveolar-capillary membrane dysfunction may contribute to symptom exacerbation and exercise intolerance, and may be an independent prognosticator of clinical course. Angiotensin-converting enzyme inhibitors ameliorate the alveolar membrane gas conductance abnormality, reflecting improvement in the remodeling process. This article reviews the putative mechanisms involved in the impairment in gas diffusion in CHF patients and provides a link between physiologic changes and clinical findings.

Resting lung function and hemodynamic parameters as predictors of exercise capacity in patients with chronic heart failure

STUDY OBJECTIVES

The aim of this study was to examine the role of resting pulmonary function and hemodynamic parameters as predictors of exercise capacity in patients with chronic heart failure.

MEASUREMENTS AND RESULTS

Fifty-one patients with chronic heart failure underwent resting pulmonary function testing, including inspiratory capacity (IC) and symptom-limited, treadmill cardiopulmonary exercise testing (CPET). Right-heart catheterization and radionuclide ventriculography were performed within 2 days of CPET. Mean (+/- SD) left ventricular ejection fraction was 31 +/- 12% and cardiac index was 2.34 +/- 0.77 L/min/m(2). Percentage of predicted FEV(1) was 92 +/- 14%, percentage of predicted FVC was 94 +/- 15%, FEV(1)/FVC was 81 +/- 4%, and percentage of predicted IC was 84 +/- 18%. Mean peak oxygen uptake (peak O(2)) was 17.9 +/- 5.4 mL/kg/min. Analysis of variance among the three functional Weber classes showed statistically significant differences for pulmonary capillary wedge pressure (PCWP) and IC. Specifically, the more severe the exercise intolerance, the lower was IC and the higher was PCWP. In a multivariate stepwise regression analysis, using peak O(2) (liters per minute) as the dependent variable and the pulmonary function test measurements as independent variables, the only significant predictor selected was IC (r = 0.71, p < 0.0001). In a final stepwise regression analysis including all the independent variables of the resting pulmonary function tests and hemodynamic measurements, the two predictors selected were IC and PCWP (r(2) = 0.58).

CONCLUSIONS

In patients with chronic heart failure, IC is inversely related to PCWP and is a strong independent predictor of functional capacity.

Impact of serial changes in cardiac hemodynamics on exercise performance in patients with heart failure due to ischemic and nonischemic cardiomyopathy

Although prior studies have examined the role of central and peripheral hemodynamics on exercise tolerance within populations of patients with heart failure, a clear relation between hemodynamics and exercise has not been demonstrated. This may be due to the inability to control for other factors that may influence exercise performance. To isolate the impact of hemodynamics on exercise, we studied the relation between changes in these factors within individual patients studied on 2 occasions. A consecutive series of 133 ambulatory patients with heart failure were evaluated on 2 separate occasions with right-sided cardiac catheterization and treadmill cardiopulmonary exercise testing. Linear regression models were constructed and correlation coefficients were determined to examine the relation between changes in hemodynamic variables and changes in exercise variables over time for each patient. A significant correlation between peak oxygen consumption (VO(2)) and pulmonary arterial wedge pressure was found for both the first (r = -0.316, p <0.001) and second (r = -0.183, p = 0.029) tests. A stronger inverse correlation between the change in pulmonary arterial wedge pressure and change in peak VO(2) was observed in the study patients (r = -0.470, p <0.001). Similar correlations were found between change in peak VO(2) and changes in pulmonary arterial pressures. Changes in left ventricular filling pressure influence exercise tolerance in patients with heart failure due to left ventricular systolic dysfunction. Interpretation of cardiopulmonary exercise testing for the purpose of determining cardiac transplantation eligibility will be improved with knowledge of left ventricular filling pressure.

Neurohormonal Determinants of Peak Oxygen Uptake in Patients with Chronic Heart Failure

Chronic heart failure (CHF) is characterized by the activation of neurohormones and cytokines. This study determined whether peak oxygen uptake (VO2) can be predicted by the degree of neurohormonal and cytokine activations in CHF. Plasma norepinephrine. epinephrine, renin-angiotensin system activity, ANP, BNP, and serum interleukin-6 (IL-6) and tumor necrosis factor (TNF)-alpha were measured in 84 CHF patients (age, 59 +/- 1 years, LVEF, 36 +/- 1%) and 34 controls. Maximal cardiopulmonary exercise testing was performed. Peak VO2 (Controls vs CHF: 27.8 +/- 1.3 vs 18.2 +/- 0.5 mL/min/kg, P < 0.0001) was lower in CHF. Patients with CHF had increased plasma norepinephrine (211 +/- 11 vs 315 +/- 24 pg/mL), renin activity (1.2 +/- 0.2 vs 6.2 +/- 1.1 ng/mL/hr), ANP (22 +/- 3 vs 72 +/- 7 pg/mL), and BNP levels (18 +/- 3 vs 200 +/- 25 pg/mL) (all P < 0.01). Serum IL-6 (1.1 0.1 vs 2.4 +/- 0.3 pg/mL) and TNF-alpha (2.7 +/- 0.2 vs 4.0 +/- 0.3 pg/mL) levels were higher in CHF (both P < 0.001). Univariate analysis revealed that age (P < 0.001), cardiothoracic ratio (P < 0.001), norepinephrine (P < 0.0001), ANP (P < 0.001), BNP (P < 0.01), and log IL-6 (P < 0.05) were significantly related with peak VO2. Stepwise regression analysis indicated that plasma norepinephrine and ANP emerged as significant determinants of peak VO2, independent of patient age (overall R = 0.61, P < 0.0001). In summary, patients with CHF exhibited activation of neurohormones and proinflammatory cytokines. Among the elevated hormonal and cytokine markers, plasma norepinephrine and ANP levels were independent predictors of exercise capacity.

Exercise training for heart failure patients improves respiratory muscle endurance, exercise tolerance, breathlessness, and quality of life

PURPOSE

Increased respiratory muscle endurance and peak oxygen consumption (VO(2peak)) induced by respiratory muscle training support the relationship between respiratory muscle function and exercise capacity in patients with heart failure. This raises the question whether exercise-training results in increased respiratory muscle function contributing to an increased exercise tolerance, a decreased perception of breathlessness, and an improved quality of life.

METHODS

Prospective cohort analysis was completed on 24 patients with New York Heart Association (NYHA) Class III heart failure [18 men, 6 women; aged = 64 (SD 7.9) years; percent ejection fraction (%EF) = 24.0 (SD 7.8)]. Maximal sustainable ventilatory capacity (MSVC), submaximal and peak exercise responses, perception of breathlessness, and quality of life were measured before (baseline) and after (end of study) 12 weeks of exercise training.

RESULTS

As a result of exercise training, VO(2peak) (P=.01) and MSVC (P<.001) increased, with MSVC contributing to a larger proportion of the variability for VO(2peak) at study completion (r=0.57 vs 0.42). Although stroke volume did not increase beyond exercise at 25 W and did not change with exercise training, ventilation decreased during exercise (P<.05), perception of breathing difficulty (P<.05) was reduced, and quality of life was enhanced (P=.008).

CONCLUSIONS

Despite no increase in cardiac output and stroke volume, respiratory muscle endurance improved with exercise training, contributing to increased exercise capacity, decreased breathlessness, and decreased perception of breathlessness. Practical implications can include less frequent rest periods and fatigue, greater confidence, maintenance of independence, and enhanced quality of life.

Diabetes worsens pulmonary diffusion in heart failure, and insulin counteracts this effect

Chronic heart failure (CHF) (hydrostatic stress) and diabetes (basal laminae thickening) share the potentiality of damaging the alveolar-capillary membrane. We investigated 15 control subjects and 3 groups of 15 patients each having type 2 diabetes (Group 1), CHF (Group 2), and diabetes and CHF (Group 3), to probe whether addition of diabetes worsens lung diffusion in CHF and whether insulin counteracts this effect. Compared with control subjects, carbon monoxide diffusing capacity (DL(CO)) and diffusing capacity of the alveolar-capillary membrane at rest were increasingly depressed from Group 1 through Group 3. DL(CO) was lower than predicted in 11 patients each in Groups 1 and 2 and in all patients in Group 3. Regular insulin (10 IU) was ineffective in CHF alone, whereas it improved DL(CO) and diffusing capacity of the alveolar-capillary membrane in diabetes; changes, however, were significantly greater in the patients with both diabetes and CHF (+17.6%, +27.3%) than in those with diabetes alone (+9.2%, +13.1%). Insulin did not affect lung spirometry, volumes, and hemodynamics. Thus, gas transfer is depressed in a number of patients with diabetes or CHF; comorbidity increases the frequency and extent of this disorder. Insulin facilitates diffusion in diabetes, through an influence on alveolar-capillary conductance, and its efficacy is greater in comorbidity; diabetes is more disturbing in patients with CHF and produces a synergistic rather than a simple additive effect.