Changes in Respiratory Muscle Strength Following Cardiac Rehabilitation for Prognosis in Patients with Heart Failure

Improving Respiratory Muscle Strength and Overall Function in Patients With Cardiovascular Disease Through Rehabilitation Hospitals

Background

The prevalence of respiratory sarcopenia and its effect on respiratory muscle strength (RMS) in patients with cardiovascular disease (CVD), who are transferred to a convalescent rehabilitation hospital after acute care and require continuous cardiac rehabilitation (CR), is currently unclear. This study aimed to assess changes in RMS, physical function, and activities of daily living (ADL) before and after CR performed in a rehabilitation hospital.

Methods

Of 50 consecutive patients transferred to a rehabilitation hospital for ongoing CR, 30 fulfilled the inclusion criteria. Maximal inspiratory and expiratory pressures (MIP and MEP, respectively) were measured at transfer, and patients with decreased RMS were diagnosed with respiratory sarcopenia. RMS, physical function, exercise tolerance, ADL ability, and health-related quality of life (HR-QoL) were measured and compared at transfer and discharge.

Results

The prevalence of respiratory sarcopenia at the time of transfer to the rehabilitation hospital was 93.3%. RMS assessments at transfer and discharge demonstrated significant improvements in %MIP (from 46.3±26.1% to 63.6±33.7%) and %MEP (from 44.8±17.3% to 56.6±21.8%). Short physical performance battery, gait speed, handgrip strength, and knee extension muscle strength significantly improved, along with significant prolongation of 6-min walking distance as a measure of exercise tolerance. ADL assessment using the functional independence measure revealed significant improvement, as did HR-QoL assessed according to the five-dimension, five-level, EuroQoL instrument, following CR.

Conclusions

Although respiratory sarcopenia was highly prevalent among patients with CVD who required transfer to a rehabilitation hospital after acute care, continuous CR significantly improved RMS, ADL, physical function, and exercise tolerance. These findings support the continued expansion of CR, particularly in dedicated rehabilitation hospitals.

The effect of cardiac rehabilitation on cardiopulmonary function after coronary artery bypass grafting: A systematic review and meta-analysis

We carried out a meta-analysis on the effect of cardiac rehabilitation (CR) on cardiopulmonary function after coronary artery bypass grafting (CABG). Four databases were searched for studies comparing CR with control. A random-effects model was used to pool mean difference (MD). The meta-analysis showed an increase in peak oxygen consumption (peak VO2) (MD = 1.93 mL/kg/min, p = 0.0006), and 6-min walk distance (6MWD) (MD = 59.21 m, p < 0.00001), and a decrease in resting heart rate (resting HR) (MD = 5.68 bpm, p < 0.0001) in the CR group. The subgroup analysis revealed aerobic exercise could further improve resting HR and peak HR, and physical/combination with aerobic exercise could further increase 6MWD. The improvement of peak VO2, workload, resting HR, peak HR, and 6MWD regarding CR performed within one week after CABG is greater than that one week after CABG. CR after CABG can improve the cardiopulmonary function, which is reflected by the improvement of peak VO2, 6MWD, and resting HR.

Respiratory Muscle Strength and Quality of Life in Patients With Heart Failure and Their Main Correlated Factors: A Cross-sectional Study

BACKGROUND

Heart failure may cause peripheral and respiratory muscle alterations, dyspnea, fatigue, and exercise intolerance, worsening the quality of life of patients.

OBJECTIVES

The aims of this study were to analyze respiratory muscle strength and quality of life of patients with heart failure and correlate them with clinical variables and functional classification.

METHODS

This cross-sectional study involved patients with heart failure. A manovacuometer assessed maximum inspiratory and expiratory pressures, and quality of life was assessed using the Minnesota Living with Heart Failure Questionnaire. Functional classification was categorized according to the New York Heart Association (NYHA) class in I, II, III, or IV.

RESULTS

We included 60 patients (66.7% male) with a mean age of 62.0 years and mean left ventricular ejection fraction of 42.0%. Maximum inspiratory pressure and maximum expiratory pressure were close to normal (>70% of predicted) in most patients; however, a subgroup composed mostly of patients with dilated heart failure and NYHA class III (n = 21) presented low maximum inspiratory pressure values (59.2%; 95% confidence interval, 55.7%-62.8%). The mean total score of the Minnesota Living with Heart Failure Questionnaire was 44.4 points, being negatively correlated with left ventricular ejection fraction (r = -0.29, P = .02). Patients with NYHA class III and disease duration longer than 120 months presented higher total (P < .01) and physical dimension scores.

CONCLUSIONS

Most patients had respiratory muscle strength close to normal; however, those with dilated heart failure and NYHA class III presented low maximum inspiratory pressure values. Quality of life was moderately compromised, mainly because of long disease duration, NYHA class III, and low left ventricular ejection fraction.

Skeletal muscle Nox4 knockout prevents and Nox2 knockout blunts loss of maximal diaphragm force in mice with heart failure with reduced ejection fraction

Patients with heart failure with reduced ejection fraction (HFrEF) experience diaphragm weakness that contributes to the primary disease symptoms of fatigue, dyspnea, and exercise intolerance. Weakness in the diaphragm is related to excessive production of reactive oxygen species (ROS), but the exact source of ROS remains unknown. NAD(P)H Oxidases (Nox), particularly the Nox2 and 4 isoforms, are important sources of ROS within skeletal muscle that contribute to optimal cell function. There are reports of increased Nox activity in the diaphragm of patients and animal models of HFrEF, implicating these complexes as possible sources of diaphragm dysfunction in HFrEF. To investigate the role of these proteins on diaphragm weakness in HFrEF, we generated inducible skeletal muscle specific knockouts of Nox2 or Nox4 using the Cre-Lox system and assessed diaphragm function in a mouse model of HFrEF induced by myocardial infarction. Diaphragm maximal specific force measured in vitro was depressed by ∼20% with HFrEF. Skeletal muscle knockout of Nox4 provided full protection against the loss of maximal force (p < 0.01), while the knockout of Nox2 provided partial protection (7% depression, p < 0.01). Knockout of Nox2 from skeletal myofibers improved survival from 50 to 80% following myocardial infarction (p = 0.026). Our findings show an important role for skeletal muscle NAD(P)H Oxidases contributing to loss of diaphragm maximal force in HFrEF, along with systemic pathophysiological responses following myocardial infarction.

Skeletal muscle abnormalities in heart failure with preserved ejection fraction

Almost half of all heart failure (HF) disease burden is due to HF with preserved ejection fraction (HFpEF). The primary symptom in patients with HFpEF, even when well compensated, is severe exercise intolerance and is associated with their reduced quality of life. Recently, studies showed that HFpEF patients have multiple skeletal muscle (SM) abnormalities, and these are associated with decreased exercise intolerance. The SM abnormalities are likely intrinsic to the HFpEF syndrome, not a secondary consequence of an epiphenomenon. These abnormalities are decreased muscle mass, reduced type I (oxidative) muscle fibers, and reduced type I-to-type II fiber ratio as well as a reduced capillary-to-fiber ratio, abnormal fat infiltration into the thigh SM, increased levels of atrophy genes and proteins, reduction in mitochondrial content, and rapid depletion of high-energy phosphate during exercise with markedly delayed repletion of high-energy phosphate during recovery in mitochondria. In addition, patients with HFpEF have impaired nitric oxide bioavailability, particularly in the microvasculature. These SM abnormalities may be responsible for impaired diffusive oxygen transport and/or impaired SM oxygen extraction. To date, exercise training (ET) and caloric restriction are some of the interventions shown to improve outcomes in HFpEF patients. Improvements in exercise tolerance following aerobic ET are largely mediated through peripheral SM adaptations with minimal change in central hemodynamics and highlight the importance of targeting SM to improve exercise intolerance in HFpEF. Focusing on the abnormalities mentioned above may improve the clinical condition of patients with HFpEF.

Correlation between respiratory muscle weakness and frailty status as risk markers for poor outcomes in patients with cardiovascular disease

AIMS

Although the developmental mechanism of respiratory muscle weakness (RMW) and frailty are partly similar in patients with cardiovascular disease (CVD), their relationship remains unclear. This study aimed to investigate the correlation between RMW and frailty and its impact on clinical outcomes in patients with CVD.

METHODS AND RESULTS

In this retrospective observational study, consecutive 1217 patients who were hospitalized for CVD treatment were enrolled. We assessed frailty status by using the Fried criteria and respiratory muscle strength by measuring the maximal inspiratory pressure (PImax) at hospital discharge, with RMW defined as PImax <70% of the predicted value. The endpoint was a composite of all-cause death and/or readmission for heart failure. We examined the prevalence of RMW and frailty and their correlation. The relationships of RMW with the endpoint for each presence or absence of frailty were also investigated. Respiratory muscle weakness and frailty were observed in 456 (37.5%) and 295 (24.2%) patients, respectively, and 149 (12.2%) patients had both statuses. Frailty was detected as a significant indicator of RMW [odds ratio: 1.84, 95% confidence interval (CI): 1.39-2.44]. Composite events occurred in 282 patients (23.2%). Respiratory muscle weakness was independently associated with an increased incidence of events in patients with both non-frailty [hazard ratio (HR): 1.40, 95% CI: 1.04-1.88] and frailty (HR: 1.68, 95% CI: 1.07-2.63).

CONCLUSIONS

This is the first to demonstrate a correlation between RMW and frailty in patients with CVD, with 12.2% of patients showing overlap. RMW was significantly associated with an increased risk of poor outcomes in patients with CVD and frailty.

Association between Rapid Dementia Screening Test score and clinical events in elderly patients with cardiovascular disease: a retrospective cohort study

AIMS

Cognitive decline is prevalent among patients with cardiovascular disease (CVD). Cognitive measurement has been considered as a standard assessment for secondary prevention; however, standard cognitive tests are sometimes infeasible due to time constraints. This study aimed to examine the association between the Rapid Dementia Screening Test (RDST), a brief screening tool for cognitive function, and clinical events in elderly patients with CVD.

METHODS AND RESULTS

This retrospective cohort study included 140 hospitalized patients with CVD who participated in inpatient cardiac rehabilitation (median age, 75 years; male, 67%). Cognitive function for each patient was assessed using the RDST and Montreal Cognitive Assessment (MoCA), a standard test of mild cognitive impairment. The clinical events assessed as outcomes included all-cause mortality and unplanned rehospitalization. Receiver-operating characteristic (ROC) curve analysis showed similar predictive accuracy for the study outcome (P = 0.337) between the RDST [area under the curve, 0.651; 95% confidence interval (CI), 0.559-0.743] and MoCA (0.625; 0.530-0.720). The ROC analysis identified a cut-off value of 9 points for the RDST (sensitivity, 77.8%; specificity, 50.5%). Patients with RDST ≤9 showed a poor survival rate compared with those with ≥10 points (log-rank test, P = 0.002; hazard ratio, 2.94, 95% CI, 1.46-5.94). This result was consistent even after adjusting for potential confounders.

CONCLUSION

The RDST was associated with clinical events in elderly patients with CVD and its predictive capability was comparable with that of MoCA, a standard cognitive test. The RDST may be useful in CVD as an alternative screening tool for cognitive decline.

Association among mild cognitive impairment, social frailty, and clinical events in elderly patients with cardiovascular disease

BACKGROUND

Social support is considered a key factor for secondary prevention in patients with cardiovascular disease (CVD) and mild cognitive impairment (MCI). Recent studies have suggested the clinical importance of social frailty in CVD.

OBJECTIVE

This study aimed to examine the association among coexistent MCI, social frailty, and clinical events in patients with CVD.

METHODS

This study included 184 hospitalized elderly patients with CVD who participated in inpatient cardiac rehabilitation (median age, 75 years; male, 66.3%). MCI was defined as a Montreal Cognitive Assessment score of ≤25 points at discharge. Social frailty was defined using the Makizako criteria. Lack of caregiver support was also assessed as an indicator of poor social support. The Kaplan-Meier survival curve analysis and Cox regression analysis were conducted to evaluate the combined impact of MCI and social frailty or the lack of caregiver support on the composite endpoint of all-cause mortality or unplanned rehospitalization.

RESULTS

The prevalence of MCI, social frailty, and lack of caregiver support were 65.2%, 70.7%, and 19.0%, respectively. There was a significant difference among subgroups by MCI and a lack of caregiver support (log-rank test, p = 0.018), and the MCI/non-caregiver group showed the worst prognosis (adjusted hazard ratio 3.96; 95% confidence interval 1.57-9.98). Likewise, MCI/social frailty group showed a significantly high event risk (3.94; 1.20-12.9) among the subgroups by MCI and social frailty.

CONCLUSION

Our results highlight the clinical importance of assessing the presence of caregiver support along with conventional social frailty for patients with CVD and MCI.

Inspiratory muscle weakness in cardiovascular diseases: Implications for cardiac rehabilitation

Exercise limitation is a cardinal manifestation of many cardiovascular diseases (CVD) and is associated with poor prognosis. It is increasingly well understood that exercise-based cardiac rehabilitation (CR) is an intervention that portends favorable clinical outcomes, including improvements in exercise capacity. The etiology of exercise limitation in CVD is multifactorial but is typically governed by terminal sensations of pain, fatigue, and/or breathlessness. A known but perhaps underestimated complication of CVD that contributes to breathlessness and exercise intolerance in such patients is inspiratory muscle dysfunction. For example, inspiratory muscle dysfunction, which encompasses a loss in muscle mass and/or pressure generating capacity, occurs in up to ~40% of patients with chronic heart failure and is associated with breathlessness, exertional intolerance, and worse survival in this patient population. In this review, we define inspiratory muscle weakness, detail its prevalence in a range of CVDs, and discuss how inspiratory weakness impacts physiological function and clinical outcomes in patients with CVD often referred to CR. We also evaluate the available evidence addressing the effects of exercise-based CR with and without concurrent specific inspiratory muscle training (IMT) on inspiratory muscle function, general physiological function, and clinical outcomes in patients with CVD. Finally, we consider whether the assessment of global respiratory muscle function should become standard as part of the patient intake assessment for phase II CR programs, giving practical guidance on the implementation of such measures as well as IMT as part of phase II CR.

Associations between kidney function and outcomes of comprehensive cardiac rehabilitation in patients with heart failure

AIMS

To investigate the impact of baseline kidney function on outcomes following comprehensive cardiac rehabilitation (CR) in patients with heart failure (HF).

METHODS

We reviewed a total of 3,727 patients who were admitted for HF treatment. Estimated glomerular filtration rate (eGFR), quadriceps strength (QS), and 6-min walk distance (6MWD) were measured at hospital discharge as a baseline and 5 months thereafter in participants of outpatient comprehensive CR. The association between outpatient CR participation and all-cause events was evaluated using propensity score-matched analysis in subgroups across eGFR stages. The changes in QS and 6MWD following 5-month CR were compared between eGFR stages.

RESULTS

Out of the studied patients, 1585 (42.5%) participated in outpatient CR. After propensity matching for clinical confounders, 2680 patients were included for analysis (pairs of n = 1340 outpatient CR participants and nonparticipants). The participation in outpatient CR was significantly associated with low clinical events in subgroups of eGFR ≥ 60 [hazard ratio (HR): 0.65, 95% confidence interval (CI): 0.51-0.84] and eGFR 45-60 (HR: 0.71, 95% CI: 0.55-0.92), but not in eGFR 30-45 (HR: 0.83, 95% CI: 0.64-1.08) and eGFR < 30 (HR: 0.88, 95% CI: 0.69-1.12). QS and 6MWD were significantly higher after 5-month CR than those at baseline (P < 0.001, respectively), but lower baseline eGFR correlated with lower changes in QS and 6MWD (trend P < 0.001, respectively).

CONCLUSIONS

Although low baseline kidney function attenuates the outcomes of CR, outpatient CR seems to be associated with a better prognosis and positive change in physical function in HF patients with low kidney function.

Endothelial Dysfunction and Its Clinical Implications

Endothelial dysfunction (ED) plays a substantial role in the pathogenesis of atherosclerosis and some other vascular diseases. ED has been demonstrated in patients with hypercholesterolemia, diabetes, smoking, hypertension, and in patients with atherosclerotic disease. Besides classical risk factors, ED is affected by chronic inflammatory diseases and acute infections, particularly viral diseases. Causes of ED include oxidative stress, inflammation, and shear stress, which decrease the bioavailability of nitric oxide. Markers of ED have been sought, particularly circulating markers. Using these tests, it is possible to evaluate the response to harmful effects of risk factors and the effects of treatment on vessel wall function. Endothelial dysfunction is significantly and directly correlated with the occurrence of cardiac events and the risk of cardiac events increase as ED worsens. Because endothelial function plays a central role in atherogenesis it became a therapeutic target. Endothelial dysfunction is reversible and its improvement may be achieved by elimination of risk factors, inhibitors of endothelium-derived contracting factors (angiotensin-converting enzyme), smoking cessation, lipid-lowering drugs, diet, and physical exercise. By reversing ED, it is possible to restore vascular function.