Heart involvement in cystic fibrosis: A specific cystic fibrosis-related myocardial changes?

Cardiac Structure and Function in People with Cystic Fibrosis

BACKGROUND

The extent of cardiac involvement in cystic fibrosis (CF) remains to be determined. The remarkable therapeutic advancements with new highly effective cystic fibrosis transmembrane conductance regulator (CFTR) modulator treatment and subsequent increase in life expectancy substantiates further research. We aimed to explore the prevalence of cardiac alterations in people with CF (pwCF) compared to matched controls and investigate potential cardiovascular risk factors.

METHODS

In this cross-sectional study, 104 pwCF underwent clinical and echocardiographic assessment. All participants were matched 1:1 with controls from the general population.

RESULTS

Of 104 pwCF, 44 % were female, mean age was 34 years, and 93 % received CFTR modulator treatment. The prevalence of abnormal cardiac function in pwCF was 44 %, more than double the prevalence in controls. PwCF were found to have smaller left ventricular (LV) dimensions, worse LV diastolic function, and reduced right ventricle (RV) as well as LV systolic function. After multivariable adjustment, LV diastolic function as well as LV and RV systolic function remained poorer in pwCF as compared to controls. Male sex and decreasing FEV1/FVC ratio remained independently associated with abnormal cardiac function in pwCF (male sex: OR 3.94 (1.56; 9.95), p = 0.004 and FEV1/FVC ratio: OR 2.05 per 0.1 unit decrease (1.21; 3.52), p = 0.008, respectively).

CONCLUSIONS

Both left- and right-sided cardiac alterations were found in pwCF. After adjustments for risk factors, both RV and LV systolic measures remained altered in pwCF, compared to controls. Male sex and decreasing pulmonary function evaluated by FEV1/FVC-ratio were associated with abnormal cardiac function in pwCF.

Echocardiographic assessment of cardiovascular involvements in children with cystic fibrosis

BACKGROUND

Over the past four decades, numerous case reports and clinical studies have highlighted the presence of heart disease in individuals with cystic fibrosis. Given the limited information in this field and the imperative to identify early changes during childhood, our study aims to explore cardiac dysfunction in patients with cystic fibrosis using echocardiography.

METHODS

In this case-control study, we examined echocardiographic findings from thirty-three patients with cystic fibrosis and sixty healthy children. Demographic information for both groups was recorded, and the disease severity in patients was assessed using the Schawachman criterion. M-mode, Doppler flow velocity, and Tissue Doppler Imaging echocardiography were performed for all participants, with subsequent data analysis using SPSS 24.

RESULTS

Our study encompassed thirty-three CF patients and sixty healthy children. The estimated pulmonary artery blood pressure (systolic and mean) in patients with cystic fibrosis was significantly higher than in the control group (P < 0.05). Additionally, the mean trans-tricuspid peak early to late diastolic flow velocity (E/A) was significantly lower in the case group than the control group (P < 0.05), along with a significantly lower mean tricuspid valve deceleration time (DT) (P < 0.05). Similarly, the mean TAPSE in the case group was notably lower than in the control group (P < 0.05). No significant difference in Mean left ventricular Ejection Fraction (EF) and Fractional Shortening (FS) existed between the two groups (P > 0.05). Furthermore, Trans-mitral peak early to late diastolic flow velocity (E/A) in the case group was significantly lower than in the control group (P < 0.05), and the mean mitral valve DT in the case group was also significantly lower (P < 0.05).

CONCLUSION

Our study findings indicate the presence of some degree of right ventricular dysfunction in children with cystic fibrosis. This finding may have implications for the development or modification of clinical guidelines for managing cystic fibrosis in children. Further investigations are recommended to elucidate the underlying mechanisms and contributing factors, providing valuable insights for clinical management.

The cardiomyopathy of cystic fibrosis: a modern form of Keshan disease

Introduction

We conducted a study to determine the prevalence of structural heart disease in patients with CF, the characteristics of a cardiomyopathy not previously described in this population, and its possible relationship with nutritional deficiencies in CF.

Methods

We studied 3 CMP CF patients referred for heart-lung transplantation and a prospective series of 120 adult CF patients. All patients underwent a clinical examination, blood tests including levels of vitamins and trace elements, and echocardiography with evaluation of myocardial strain. Cardiac magnetic resonance imaging (CMR) was performed in patients with CMP and in a control group. Histopathological study was performed on hearts obtained in transplant or necropsy.

Results

We found a prevalence of 10% (CI 4.6%-15.4%) of left ventricular (LV) dysfunction in the prospective cohort. Myocardial strain parameters were already altered in CF patients with otherwise normal hearts. Histopathological examination of 4 hearts from CF CMP patients showed a unique histological pattern of multifocal myocardial fibrosis similar to Keshan disease. Four of the five CF CMP patients undergoing CMR showed late gadolinium uptake, with a characteristic patchy pattern in 3 cases (p < 0.001 vs. CF controls). Selenium deficiency (Se < 60 µg/L) was associated with more severe LV dysfunction, higher prevalence of CF CMP, higher NTproBNP levels, and more severe pulmonary and digestive involvement.

Conclusion

10% of adults with CF showed significant cardiac involvement, with histological and imaging features resembling Keshan disease. Selenium deficiency was associated with the presence and severity of LV dysfunction in these patients.

Can Bioactive Food Substances Contribute to Cystic Fibrosis-Related Cardiovascular Disease Prevention?

Advances in cystic fibrosis (CF) care have significantly improved the quality of life and life expectancy of patients. Nutritional therapy based on a high-calorie, high-fat diet, antibiotics, as well as new therapies focused on CFTR modulators change the natural course of the disease. They do so by improving pulmonary function and growing BMI. However, the increased weight of such patients can lead to unwanted long-term cardiovascular effects. People with CF (pwCF) experience several cardiovascular risk factors. Such factors include a high-fat diet and increased dietary intake, altered lipid metabolism, a decrease in the level of fat-soluble antioxidants, heightened systemic inflammation, therapeutic interventions, and diabetes mellitus. PwCF must pay special attention to food and eating habits in order to maintain a nutritional status that is as close as possible to the proper physiological one. They also have to benefit from appropriate nutritional counseling, which is essential in the evolution and prognosis of the disease. Growing evidence collected in the last years shows that many bioactive food components, such as phytochemicals, polyunsaturated fatty acids, and antioxidants have favorable effects in the management of CF. An important positive effect is cardiovascular prevention. The possibility of preventing/reducing cardiovascular risk in CF patients enhances both quality of life and life expectancy in the long run.

Whole-Exome Sequencing Revealed New Candidate Genes for Human Dilated Cardiomyopathy

Dilated cardiomyopathy (DCM) is a complex disease affecting young adults. It is a pathological condition impairing myocardium activity that leads to heart failure and, in the most severe cases, transplantation, which is currently the only possible therapy for the disease. DCM can be attributed to many genetic determinants interacting with environmental factors, resulting in a highly variable phenotype. Due to this complexity, the early identification of causative gene mutations is an important goal to provide a genetic diagnosis, implement pre-symptomatic interventions, and predict prognosis. The advent of next-generation sequencing (NGS) has opened a new path for mutation screening, and exome sequencing provides a promising approach for identifying causal variants in known genes and novel disease-associated candidates. We analyzed the whole-exome sequencing (WES) of 15 patients affected by DCM without overloading (hypertension, valvular, or congenital heart disease) or chronic ischemic conditions. We identified 70 pathogenic or likely pathogenic variants and 1240 variants of uncertain clinical significance. Gene ontology enrichment analysis was performed to assess the potential connections between affected genes and biological or molecular function, identifying genes directly related to extracellular matrix organization, transcellular movement through the solute carrier and ATP-binding cassette transporter, and vitamin B12 metabolism. We found variants in genes implicated to a different extent in cardiac function that may represent new players in the complex genetic scenario of DCM.

Altered intravenous drug disposition in people living with cystic fibrosis: A meta‐analysis integrating top‐down and bottom‐up data

Cystic fibrosis (CF) has been linked to altered drug disposition in various studies. However, the magnitude of these changes, influencing factors, and underlying mechanisms remain a matter of debate. The primary aim of this work was therefore to quantify changes in drug disposition (top‐down) and the pathophysiological parameters known to affect pharmacokinetics (PKs; bottom‐up). This was done through meta‐analyses and meta‐regressions in addition to theoretical PK simulations. Volumes of distribution and clearances were found to be elevated in people living with CF. These increases were larger in studies which included patients with pulmonary exacerbations. Differences in clearance were smaller in more recent studies and when results were normalized to body surface area or lean body mass instead of body weight. For the physiological parameters investigated, measured glomerular filtration rate and serum cytokine concentrations were found to be elevated in people living with CF, whereas serum albumin and creatinine levels were decreased. Possible pathophysiological mechanisms for these alterations relate to renal hyperfiltration, increases in free fraction, and inflammation. No differences were detected for cardiac output, body fat, fat free mass, hematocrit, creatinine clearance, and the activity of drug metabolizing enzymes. These findings imply that, in general, lower total plasma concentrations of drugs can be expected in people living with CF, especially when pulmonary exacerbations are present. Given the potential effect of CF on plasma protein binding and the variability in outcome observed between studies, the clinical relevance of adapting existing dosage regimens should be evaluated on a case‐by‐case basis.

Cyclic GMP modulating drugs in cardiovascular diseases: mechanism-based network pharmacology

Mechanism-based therapy centred on the molecular understanding of disease-causing pathways in a given patient is still the exception rather than the rule in medicine, even in cardiology. However, recent successful drug developments centred around the second messenger cyclic guanosine-3'-5'-monophosphate (cGMP), which is regulating a number of cardiovascular disease modulating pathways, are about to provide novel targets for such a personalized cardiovascular therapy. Whether cGMP breakdown is inhibited or cGMP synthesis is stimulated via guanylyl cyclases or their upstream regulators in different cardiovascular disease phenotypes, the outcomes seem to be so far uniformly protective. Thus, a network of cGMP-modulating drugs has evolved that act in a mechanism-based, possibly causal manner in a number of cardiac conditions. What remains a challenge is the detection of cGMPopathy endotypes amongst cardiovascular disease phenotypes. Here, we review the growing clinical relevance of cGMP and provide a glimpse into the future on how drugs interfering with this pathway may change how we treat and diagnose cardiovascular diseases altogether.

Effects of a Long-Term Wearable Activity Tracker-Based Exercise Intervention on Cardiac Morphology and Function of Patients with Cystic Fibrosis

Several studies have shown that patients with cystic fibrosis (CF), even at a young age, have pulmonary and cardiac abnormalities. The main complications are cardiac right ventricular (RV) systolic and/or diastolic dysfunction and pulmonary hypertension, which affects their prognosis. Exercise training (ET) is recommended in patients with CF as a therapeutic modality to improve physical fitness and health-related quality of life. However, questions remain regarding its optimal effective and safe dose and its effects on the patients’ cardiac function. The study aimed to provide a wearable activity tracker (WAT)-based ET to promote physical activity in CF patients and assess its effects on cardiac morphology and function. Forty-two stable CF individuals (aged 16.8 ± 3.6 years) were randomly assigned to either the intervention (Group A) or the control group (Group B). Group A participated in a 1-year WAT-based ET program three times per week. All patients underwent a 6-min walking test (6-MWT) and an echocardiographic assessment focused mainly on RV anatomy and function at the baseline and the end of the study. RV systolic function was evaluated by measuring the tricuspid annular plane systolic excursion (TAPSE), the systolic tricuspid annular velocity (TVS’), the RV free-wall longitudinal strain (RVFWSL), and the right ventricular four-chamber longitudinal strain (RV4CSL). RV diastolic function was assessed using early (TVE) and late (TVA) diastolic transtricuspid flow velocity and their ratio TVE/A. Pulmonary artery systolic pressure (PASP) was also estimated. In Group A after ET, the 6MWT distance improved by 20.6% (p < 0.05), TVA decreased by 17% (p < 0.05), and TVE/A increased by 13.2% (p < 0.05). Moreover, TAPSE, TVS’, RVFWSL, and RV4CSL increased by 8.3% (p < 0.05), 9.0% (p < 0.05), 13.7% (p < 0.05), and 26.7% (p < 0.05), respectively, while PASP decreased by 7.6% (p < 0.05). At the end of the study, there was a significant linear correlation between the number of steps and the PASP (r = −0.727, p < 0.01) as well as the indices of RV systolic function in Group A. In conclusion, WAT is a valuable tool for implementing an effective ET program in CF. Furthermore, ET has a positive effect on RV systolic and diastolic function.

Cardiac involvement in cystic fibrosis evaluated using cardiopulmonary magnetic resonance

Cystic fibrosis (CF) transmembrane conductance regulator is expressed in myocardium, but cardiac involvement in CF remains poorly understood. The recent development of a combined cardiopulmonary magnetic resonance imaging technology allows for a simultaneous interrogation of cardiac and pulmonary structure and function. The aim of this study was to investigate myocardial manifestations in adults with CF, both in a stable state and during an acute respiratory exacerbation, and to investigate the relationship between cardiac and pulmonary disease. Healthy adult volunteers (n = 12) and adults with CF (n = 10) were studied using a multiparametric cardiopulmonary magnetic resonance protocol. CF patients were scanned during an acute respiratory exacerbation and re-scanned when stable. Stable CF was associated with left ventricular dilatation and hypertrophy (LVH; left ventricular mass: CF 59 ± 9 g/m2 vs. control 50 ± 8 g/m2; p = 0.028). LVH was predominantly driven by extracellular myocardial matrix expansion (extracellular matrix mass: CF 27.5 ± 3.4 g vs. control 23.6 ± 5.2 g; p = 0.006; extracellular volume [ECV]: CF 27.6 [24.7-29.8]% vs. control 24.8 [22.9-26.0]%; p = 0.030). Acute CF was associated with an acute reduction in left ventricular function (ejection fraction: acute 57 ± 3% vs. stable 61 ± 5%; p = 0.025) and there was a suggestion of myocardial oedema. Myocardial oedema severity was strongly associated with the severity of airflow limitation (r = - 0.726, p = 0.017). Multiparametric cardiopulmonary magnetic resonance technology allows for a simultaneous interrogation of cardiac and pulmonary structure and function. Stable CF is associated with adverse myocardial remodelling, including left ventricular systolic dilatation and hypertrophy, driven by myocardial fibrosis. CF exacerbation is associated with acute myocardial contractile dysfunction. There is also a suggestion of myocardial oedema in the acute period which is related to pulmonary disease severity.

Emerging non-pulmonary complications for adults with cystic fibrosis

Improved treatments of cystic fibrosis (CF) related lung disease have resulted in increased longevity, but also increasing prevalence and severity of extrapulmonary manifestations of CF, treatment related complications, age-related conditions and psychosocial effects of longstanding chronic disease. Likewise, the recognition of mild CF phenotypes has changed the landscape of CF disease. This review outlines our current understanding of the common extrapulmonary complications of CF, as well as the changing landscape and future directions of the extrapulmonary complications experienced by patients with CF.

Cardiovascular System Involvement in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive disease primarily affecting the respiratory system and gastrointestinal system. The life expectancy of patients with CF has significantly improved due to medical advancement and the effective use of screening techniques. However, new challenges have emerged. Particularly those involving cardiovascular pathology. This study aims to provide a better understanding of the different mechanisms that cause cardiovascular complications in patients with CF, which would help find an efficient treatment that not only prolongs survival but also improves their quality of life. This study extensively reviews different theories such as right ventricular hypertrophy due to lung pathology, ventricular interdependence, the association of nutritional deficiencies and severe cystic fibrosis transmembrane conductance regulator (CFTR) genotypes with myocardial fibrosis, effects of hypoxia, recurrent infections, and systemic inflammation of the heart and blood vessels that explain the direct or indirect involvement of the cardiovascular system in CF. For this review, 258 articles were retrieved from PubMed and Google Scholar. Out of which, a total of 12 high-quality articles were selected using appropriate quality assessment tools and preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The result of this study suggests that early detection of cardiovascular dysfunction can improve the survival rate of the patient. Furthermore, this study could aid future researchers in the exploration of various best screening modality techniques for the early detection of cardiovascular dysfunction.

Early intrahepatic duct defects in a cystic fibrosis porcine model

Hepatobiliary disease causes significant morbidity and mortality in people with cystic fibrosis (CF), yet this problem remains understudied. Previous studies in the newborn CF pig demonstrated decreased bile flow into the small intestine and a microgallbladder with increased luminal mucus and fluid secretion defects. In this study, we examined the intrahepatic bile ducts of the newborn CF pig. We assessed whether our findings from the gallbladder are present elsewhere in the porcine biliary tract and if CF pig cholangiocytes have fluid secretion defects. Immunohistochemistry demonstrated apical CFTR expression in non-CF pig intrahepatic bile ducts of a variety of sizes; CF pig intrahepatic bile ducts lacked CFTR expression. Assessment of serum markers did not reveal significant signs of hepatobiliary disease except for an elevation in direct bilirubin. Quantitative histology demonstrated that CF pigs had smaller bile ducts that more frequently contained luminal mucus. CF intrahepatic cholangiocyte organoids were smaller and lacked cAMP-mediated fluid secretion. Together these data suggest that cholangiocyte fluid secretion is decreased in the CF pig, contributing to structural changes in bile ducts and decreased biliary flow.

Cardiovascular complications in cystic fibrosis: A review of the literature

Cystic fibrosis is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, leading to dysfunction of the CFTR protein. CFTR dysfunction leads to disease in the respiratory and gastrointestinal systems. Disorders of the cardiovascular system in individuals with CF are usually attributed to secondary effects from progressive lung disease. However, CFTR has been localized to vascular endothelium and smooth muscle, suggesting that CFTR dysfunction may directly impact cardiovascular function. As treatments for CF improve and life-expectancy increases, the risk of vascular disease may increase in prevalence related to primary and secondary CFTR dysfunction, chronic systemic inflammation, nutritional health and hyperglycemia in individuals with CF related diabetes. Here we review the available literature on CF and the cardiovascular system, examining the secondary effects and evidence for direct CFTR dysfunction in the heart, aorta, pulmonary vessels, and vasculature, as well as future directions and treatment options.

Involvement of CFTR in the pathogenesis of pulmonary arterial hypertension

INTRODUCTION

A reduction in pulmonary artery (PA) relaxation is a key event in pulmonary arterial hypertension (PAH) pathogenesis. CFTR dysfunction in airway epithelial cells plays a central role in cystic fibrosis (CF); CFTR is also expressed in PAs and has been shown to control endothelium-independent relaxation.

AIM AND OBJECTIVES

We aimed to delineate the role of CFTR in PAH pathogenesis through observational and interventional experiments in human tissues and animal models.

METHODS AND RESULTS

RT-Q-PCR, confocal imaging and electron microscopy showed that CFTR expression was reduced in PAs from patients with idiopathic PAH (iPAH) and in rats with monocrotaline-induced pulmonary hypertension (PH). Moreover, using myograph on human, pig and rat PAs, we demonstrated that CFTR activation induces PAs relaxation. CFTR-mediated PA relaxation was reduced in PAs from iPAH patients and rats with monocrotaline- or chronic hypoxia-induced PH. Long-term in vivo CFTR inhibition in rats significantly increased right ventricular systolic pressure, which was related to exaggerated pulmonary vascular cell proliferation in situ and vessel neomuscularization. Pathologic assessment of lungs from patients with severe CF (F508del-CFTR) revealed severe PA remodeling with intimal fibrosis and medial hypertrophy. Lungs from homozygous F508delCftr rats exhibited pulmonary vessel neomuscularization. The elevations in right ventricular systolic pressure and end diastolic pressure in monocrotaline-exposed rats with chronic CFTR inhibition were more prominent than those in vehicle-exposed rats.

CONCLUSIONS

CFTR expression is strongly decreased in PA smooth muscle and endothelial cells in human and animal models of PH. CFTR inhibition increases vascular cell proliferation and strongly reduces PA relaxation.

Right ventricular diastolic dysfunction and failure: a review

Right ventricular diastolic dysfunction and failure (RVDDF) has been increasingly identified in patients with cardiovascular diseases, including heart failure and other diseases with cardiac involvement. It is unknown whether RVDDF exists as a distinct clinical entity; however, its presence and degree have been shown to be a sensitive marker of end-organ dysfunction related to multiple disease processes including systemic hypertension, pulmonary hypertension, heart failure, and endocrine disease. In this manuscript, we review issues pertaining to RVDDF including anatomic features of the right ventricle, physiologic measurements, RVDDF diagnosis, underlying mechanisms, clinical impact, and clinical management. Several unique features of RVDDF are also discussed.

Multidisciplinary approach to patients with manifestations and pulmonary complications of cystic fibrosis

Cystic fibrosis (CF) is a genetic disease, with autosomal recessive transmission, multisystemic, characterized by a remarkable clinical polymorphism and significant lethal prospective. Respiratory manifestations dominate the clinical picture, being present in all patients. The aim of the paper was to analyze the incidence of clinical manifestations, especially respiratory ones, as well as the contribution of interdisciplinary consultations to the positive diagnosis of CF, in a group of 16 patients who were hospitalized and treated in the II^nd Pediatric Clinic and II^nd Medical Clinic of the Emergency County Hospital, Craiova, Romania, in a period of 20 years. The 16 patients diagnosed with and treated of CF had all shown increased values of sweat chloride concentration of over 60 mmol/L. The main symptoms and clinical signs encountered in these patients were cough (75%), sputum (62.5%), dyspnea (50%), wheezing (50%), stature hypotrophy (100%), pallor (37.5%), cyanosis (25%). All 16 patients had an acute exacerbation of chronic pulmonary disease. Of the total hospitalizations, the death was recorded only in the case of one female patient. The association of some clinical aspects specific with a positive result of the sweat test or the presence of the two pathological alleles made room for determining a positive diagnosis. The multisystemic nature of this disease requires a multidisciplinary approach to these patients. Histopathologically, there was a correspondence between lung morphological lesions and the results of imaging investigations.

Perioperative Management and Preemptive ECMO Cannulation of a Parturient with Cystic Fibrosis Undergoing Cesarean Delivery

Physiologic changes of pregnancy and cystic fibrosis pathology provide a unique set of circumstances. Pulmonary disease accounts for over 90% of the morbidity and mortality of patients with cystic fibrosis. These abnormalities create anesthetic challenges due to multiple organ systems being affected including the respiratory, gastrointestinal, cardiovascular, and genitourinary tracts, where patients present with chronic respiratory failure, pancreatic insufficiency, poor nutrition, and cardiac manifestations. We present the perianesthetic management of a parturient with cystic fibrosis who successfully underwent preterm cesarean delivery under neuraxial anesthesia with preemptive bilateral femoral venous sheaths placed for potential extracorporeal membrane oxygenation (ECMO) initiation.

Right Ventricle Dysfunction in Patients With Adult Cystic Fibrosis Enlisted for Lung Transplant

Knowledge of preoperative right heart function of adult patients with cystic fibrosis (CF) awaiting lung transplant (LUTX) is limited. The echocardiography of adult patients with CF enlisted for LUTX was retrospectively analyzed and compared with standards and invasive analyses (right heart catheterization, multigated radionuclide ventriculography). We included 49 patients (reported as mean ± standard deviation; 29 ± 9 years of age; forced expiratory volume in first second of expiration, 31% ± 11% predicted; lung allocation score, 36 ± 5; invasive mean pulmonary artery pressure, 17 ± 5 mm Hg; multigated radionuclide ventriculography right ventricle [RV] ejection fraction, 50% ± 9%). Patients had increased RV end-diastolic area, RV wall thickness, and increased pulmonary artery acceleration time with subnormal tricuspid annular plane systolic excursion, tissue Doppler positive peak systolic velocity, and fraction area change. Subnormal tricuspid annular plane systolic excursion (< 23 mm), tissue Doppler positive peak systolic velocity (< 14 cm/s), and fraction area change (< 49%) had high sensitivity and negative predictive value in predicting impaired RV. EJECTION FRACTION: A good correlation between echocardiographic estimated and invasively measured systolic pulmonary artery pressure was observed (R² = 0.554, P < .001). Adults with CF awaiting LUTX have morphologic alterations of the right heart, with subclinical impairment of RV systolic function. Echocardiography may be used as a bedside, repeatable, and reliable noninvasive test to screen further deterioration in RV function while on the waiting list for LUTX. More prospective follow-up echocardiographic studies are necessary to confirm such a hypothesis.

Oxygen transport and utilisation during exercise in cystic fibrosis: contributors to exercise intolerance

NEW FINDINGS

What is the topic of this review? This review highlights the central and peripheral mechanisms that alter oxygen transport and utilisation and thereby contribute to exercise limitation in people with cystic fibrosis, considering also viable therapeutic targets for intervention. What advances does it highlight? Although traditionally considered a respiratory condition, pathological intramuscular and cardiovascular changes in people with cystic fibrosis appear to be key determinants of exercise intolerance up until the later stages of respiratory disease. Even young, habitually active patients with normal lung function experience multisystemic abnormalities, which play a role in exercise intolerance.

ABSTRACT

Cystic fibrosis (CF) is a complex condition, commonly associated with exercise limitation. The mechanisms responsible for this in CF are of interest, given that lower aerobic fitness is associated with an increased risk of being hospitalised with pulmonary exacerbation, a poorer quality of life and a poorer prognosis. Pathophysiological changes in lung function are considered central to CF, and may contribute to exercise limitation. However, it is now clear that the pathogenesis of exercise limitation in this population is multifactorial, with alterations in cardiovascular, muscle and pulmonary function contributing. Whilst some of these changes are attributable to respiratory disease per se, the CF transmembrane conductance regulator protein is also found in skeletal muscle and the vascular endothelium and can directly alter central and localised oxygen delivery, as well as the ability to effectively extract and utilise oxygen at the myocyte level. Since intense exercise poses considerable challenges to arterial oxygen content and/or blood flow and its supply to the working skeletal muscle, evaluating the exercise physiology of people with CF has helped us understand the mechanisms underlying exercise intolerance. Through several investigations over recent years, we have collectively demonstrated that people with CF exhibit reduced skeletal muscle oxygen extraction and utilisation during exercise, with a lesser contribution from haemodynamic or chronotropic mechanisms. Taken together, our findings highlight the importance of targeting mechanisms of skeletal muscle oxygen utilisation in CF to improve exercise tolerance and we offer potential therapeutic interventional strategies.

Activated L-Arginine/Nitric Oxide Pathway in Pediatric Cystic Fibrosis and Its Association with Pancreatic Insufficiency, Liver Involvement and Nourishment: An Overview and New Results

Cystic fibrosis (CF; OMIM 219700) is a rare genetic disorder caused by a chloride channel defect, resulting in lung disease, pancreas insufficiency and liver impairment. Altered L-arginine (Arg)/nitric oxide (NO) metabolism has been observed in CF patients’ lungs and in connection with malnutrition. The aim of the present study was to investigate markers of the Arg/NO pathway in the plasma and urine of CF patients and to identify possible risk factors, especially associated with malnutrition. We measured the major NO metabolites nitrite and nitrate, Arg, a semi-essential amino acid and NO precursor, the NO synthesis inhibitor asymmetric dimethylarginine (ADMA) and its major urinary metabolite dimethylamine (DMA) in plasma and urine samples of 70 pediatric CF patients and 78 age-matched healthy controls. Biomarkers were determined by gas chromatography–mass spectrometry and high-performance liquid chromatography. We observed higher plasma Arg (90.3 vs. 75.6 µM, p < 0.0001), ADMA (0.62 vs. 0.57 µM, p = 0.03), Arg/ADMA ratio (148 vs. 135, p = 0.01), nitrite (2.07 vs. 1.95 µM, p = 0.03) and nitrate (43.3 vs. 33.1 µM, p < 0.001) concentrations, as well as higher urinary DMA (57.9 vs. 40.7 µM/mM creatinine, p < 0.001) and nitrate (159 vs. 115 µM/mM creatinine, p = 0.001) excretion rates in the CF patients compared to healthy controls. CF patients with pancreatic sufficiency showed plasma concentrations of the biomarkers comparable to those of healthy controls. Malnourished CF patients had lower Arg/ADMA ratios (p = 0.02), indicating a higher NO synthesis capacity in sufficiently nourished CF patients. We conclude that NO production, protein-arginine dimethylation, and ADMA metabolism is increased in pediatric CF patients. Pancreas and liver function influence Arg/NO metabolism. Good nutritional status is associated with higher NO synthesis capacity and lower protein-arginine dimethylation.

CFTR deficiency causes cardiac dysplasia during zebrafish embryogenesis and is associated with dilated cardiomyopathy

Mutations in the CFTR gene cause cystic fibrosis (CF) with myocardial dysfunction. However, it remains unknown whether CF-related heart disease is a secondary effect of pulmonary disease, or an intrinsic primary defect in the heart. Here, we used zebrafish, which lack lung tissue, to investigate the role of CFTR in cardiogenesis. Our findings demonstrated that the loss of CFTR impairs cardiac development from the cardiac progenitor stage, resulting in cardiac looping defects, a dilated atrium, pericardial edema, and a decrease in heart rate. Furthermore, we found that cardiac development was perturbed in wild-type embryos treated with a gating-specific CFTR channel inhibitor, CFTRinh-172, at the blastula stage of development, but not at later stages. Gene expression analysis of blastulas indicated that transcript levels, including mRNAs associated with cardiovascular diseases, were significantly altered in embryos derived from cftr mutants relative to controls. To evaluate the role of CFTR in human heart failure, we performed a genetic association study on individuals with dilated cardiomyopathy and found that the I556V mutation in CFTR, which causes a channel defect, was associated with the disease. Similar to other well-studied channel-defective CFTR mutants, CFTR I556V mRNA failed to restore cardiac dysplasia in mutant embryos. The present study revealed an important role for the CFTR ion channel in regulating cardiac development during early embryogenesis, supporting the hypothesis that CF-related heart disease results from an intrinsic primary defect in the heart.

High-intensity interval training accelerates oxygen uptake kinetics and improves exercise tolerance for individuals with cystic fibrosis

Background

Exercise training provides benefits for individuals with cystic fibrosis; however, the optimal program is unclear. High-intensity interval training is safe and effective for improving ‘functional capacity’ in these individuals with peak rate of O₂ uptake typically referenced. The ability to adjust submaximal rate of oxygen uptake (V̇O₂ kinetics) might be more important for everyday function because maximal efforts are usually not undertaken. Moreover, the ability of high-intensity training to accelerate V̇O₂ kinetics for individuals with cystic fibrosis could be enhanced with O₂ supplementation during training.

Methods

Nine individuals with cystic fibrosis completed incremental cycling to limit of tolerance followed by 8 weeks of high-intensity interval cycling (2 sessions per week x ~ 45 min per session) either with (n = 5; O2+) or without (AMB) oxygen supplementation (100%). Each session involved work intervals at 70% of peak work rate followed by 60 s of recovery at 35%. For progression, duration of work intervals was increased according to participant tolerance.

Results

Both groups experienced a significant increase in work-interval duration over the course of the intervention (O2+, 1736 ± 141 v. 700 ± 154 s; AMB, 1463 ± 598 v. 953 ± 253 s; P = 0.000); however, the increase experienced by O2+ was greater (P = 0.027). During low-intensity constant-work-rate cycling, the V̇O₂ mean response time was shortened post compared to pre training (O2+, 34 ± 11 v. 44 ± 9 s; AMB, 39 ± 14 v. 45 ± 17 s; P = 0.000) while during high-intensity constant-work-rate cycling, time to exhaustion was increased (O2+, 1628 ± 163 v. 705 ± 133 s; AMB, 1073 ± 633 v. 690 ± 348 s; P = 0.002) and blood [lactate] response was decreased (O2+, 4.5 ± 0.9 v. 6.3 ± 1.4 mmol^. L^− 1; AMB, 4.5 ± 0.6 v. 5.2 ± 1.4 mmol^. L^− 1; P = 0.003). These positive adaptations were similar regardless of gas inspiration during training.

Conclusion

Eight weeks of high-intensity interval training for patients with cystic fibrosis accelerated V̇O₂ kinetics and increased time to exhaustion. This provides some evidence that these patients may benefit from this type of exercise.

Trial registration

This study was retrospectively registered in the ISRTCN registry on 22/06/2019 (#ISRCTN13864650).

Focus on echocardiographic right ventricular strain analysis in cystic fibrosis adults without cardiovascular risk factors: a case-control study

Strain echocardiography is able to detect subclinical ventricular systolic and diastolic dysfunction. Prolonged survival to cystic fibrosis favors heart and vessel involvement. The purpose of the present study was to compare clinically stable adult patients affected by cystic fibrosis without overt pulmonary hypertension with controls to evaluate right ventricular (RV) systolic and diastolic function by means of strain and tissue Doppler imaging (TDI), respectively. 22 adults affected by cystic fibrosis and 24 healthy volunteers matched for age and sex were enrolled. None had known cardiovascular risk factors or overt pulmonary hypertension. All people underwent blood pressure measurement and transthoracic echocardiography. Cystic fibrosis patients showed higher sPAP [median 25 (IQR 21-30) vs 22 (22-22) mmHg; p = 0.02] and more frequent RV diastolic dysfunction (p < 0.001). Among cases, some RV systolic parameters were significantly altered than controls, such as TAPSE [20 (18-24) vs. 23 (21-28) mm; p = 0.001], FAC [34 (26-44) vs. 49 (48-50)%; p < 0.001], midwall tissue strain [- 25.0 (- 31.3 to - 22.8) vs. - 30.5 (- 31.8 to - 29.3)%; p = 0.03], apical tissue strain [- 22 (- 29.3 to - 19.0) vs. - 30.5 (- 32.8 to - 28.3)%; p = 0.001] and 2D strain [- 22.0 (- 25.1 to - 19.0) vs. - 29.5 (- 31.8 to - 27.3)%; p < 0.001]. Finally, 2D strain correlated with spirometric FEV1 (ρ = - 0.463, p = 0.03) and nearly with FEF25-75% (ρ = - 0.393, p = 0.07). Our study confirmed a RV subclinical systo-diastolic dysfunction in clinically stable patients affected by cystic fibrosis without overt pulmonary hypertension nor cardiovascular risk factors. This may be due to systemic inflammation and temporary recurrent pulmonary hypertension. We retain that RV 2D strain and TDI echocardiography could become an important tool in the follow-up of these patients.

Biatrial Remodeling in Patients with Cystic Fibrosis Running Title: Atrial Function in Cystic Fibrosis

BACKGROUND

Previous studies have focused on left and right ventricular remodeling in cystic fibrosis (CF), whereas atrial function has not been assessed in detail so far. We sought to investigate left and right atrial (LA and RA) function in patients with CF.

METHODS

This retrospective investigation included 82 CF patients (64 survivors and 18 non-survivors) who were referred to CF department over the period of four years, as well as 32 control subjects matched by age and gender. All participants underwent an echocardiographic examination including a strain analysis, which was performed offline and blinded for groups.

RESULTS

LA and RA volume indexes were significantly higher in CF patients than in controls and were particularly high in CF non-survivors. LA conduit and reservoir functions were significantly worse in CF survivors and non-survivors, compared with control subjects. RA phasic function was not different between controls, CF survivors and non-survivors. The parameters of lung function (forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1)) and the LA and RA volume indexes were predictors of mortality in CF patients. However, in a multivariate analysis, only FVC was an independent predictor of mortality in CF patients.

CONCLUSIONS

Our results suggest that both atria are enlarged, but only LA function is impaired in CF patients. LA reservoir and conduit function is particularly deteriorated in CF patients. Though statistical significance was not reached due to our limited sample size, there was a trend of deterioration of LA and RA function from controls across CF survivors to CF non-survivors. LA and RA enlargement represented predictors of mortality in CF patients.

Exercise capacity in patients with cystic fibrosis vs. non-cystic fibrosis bronchiectasis

Background

Bronchiectasis is associated with morbidity, low exercise capacity and poor quality of life. There is a paucity of data on exercise capacity using cardiopulmonary exercise test (CPET) in non-cystic fibrosis (CF) bronchiectasis. Our aim was to compare exercise capacity using CPET in CF and non-CF bronchiectasis patients.

Methods

Cross-sectional retrospective/prospective controlled study assessing CPET using cycle ergometer. Exercise parameters and computed tomography (CT) findings were compared. Results: Hundred two patients with bronchiectasis and 88 controls were evaluated; 49 CF (age 19.7 ± 9.7 y/o, FEV₁%predicted 70.9 ± 20.5%) and 53 non-CF (18.6 ± 10.6 y/o, FEV₁%predicted 68.7 ± 21.5%). Peak oxygen uptake (peak V˙O2) was similar and relatively preserved in both groups (CF 1915.5±702.0; non-CF 1740±568; control 2111.0±748.3 mL/min). Breathing limitation was found in the two groups vs. control; low breathing reserve (49% in CF; 43% non-CF; 5% control) and increased V˙E/V˙CO2 (CF 31.4±4.1, non-CF 31.7±4.1 and control 27.2 ± 2.8). Oxygen pulse was lower in the non-CF; whereas a linear relationship between peak V˙O2 vs. FEV₁ and vs. FVC was found only for CF. CT score correlated with V˙E/V˙CO2 and negatively correlated with V˙O2/kg and post exercise oxygen saturation (SpO₂).

Conclusions

CPET parameters may differ between CF and non-CF bronchiectasis. However, normal exercise capacity may be found unrelated to the etiology of the bronchiectasis. Anatomical changes in CT are associated with functional finding of increased V˙E/V˙CO2 and decreased SpO₂. Larger longitudinal studies including cardiac assessment are needed to better study exercise capacity in different etiologies of non-CF bronchiectasis.

Trial registration

ClinicalTrials.gov, registration number: NCT03147651.

Exercise Stroke Volume in Adult Cystic Fibrosis: A Comparison of Acetylene Pulmonary Uptake and Oxygen Pulse

Cardiac hemodynamic assessment during cardiopulmonary exercise testing (CPET) is proposed to play an important role in the clinical evaluation of individuals with cystic fibrosis (CF). Cardiac catheterization is not practical for routine clinical CPET. Use of oxygen pulse (O₂pulse) as a noninvasive estimate of stroke volume (SV) has not been validated in CF. This study tested the hypothesis that peak exercise O₂pulse is a valid estimate of SV in CF. Measurements of SV via the acetylene rebreathe technique were acquired at baseline and peak exercise in 17 mild-to-moderate severity adult CF and 25 age-matched healthy adults. We calculated O2pulse=V.O2HR. Baseline relationships between SV and O₂pulse were significant in CF (r = .80) and controls (r = .40), persisting to peak exercise in CF (r = .63) and controls (r = .73). The standard error of estimate for O₂pulse-predicted SV with respect to measured SV was similar at baseline (14.1 vs 20.1 mL) and peak exercise (18.2 vs 13.9 mL) for CF and controls, respectively. These data suggest that peak exercise O₂pulse is a valid estimate of SV in CF. The ability to noninvasively estimate SV via O₂pulse during routine clinical CPET can be used to improve test interpretation and advance our understanding of the impact cardiac dysfunction has on exercise intolerance in CF.

Technological advances shed light on left ventricular cardiac disturbances in cystic fibrosis

Cystic fibrosis (CF), the most common autosomal recessive lethal disease in Caucasians, causes chronic pulmonary disease and can lead to cor pulmonale with right ventricular dysfunction. The presence of the cystic fibrosis transmembrane conductance regulator (CFTR) in cardiac myocardia has prompted debate regarding possible defective ion channel-induced cardiomyopathy. Clinical heart disease in CF is considered rare and is restricted to case reports. It has been unclear if this is due to the lack of physiological importance of CFTR in the heart, the relatively short lifespan of those with CF, or a technical inability to detect subclinical disease. Extensive echocardiographic investigations have yielded contradictory results, leading to the dogma that left ventricular defects in CF occur secondary to lung disease. In this review, we consider why studies examining heart function in CF have not provided clarity on this topic. We then focus on data from new echocardiographic and magnetic resonance imaging technology, which are providing greater insight into cardiac function in CF and demonstrating that, in addition to secondary effects from pulmonary disease, there may be an intrinsic primary defect in the CF heart. With advancing lifespans and activity levels, understanding the risk of cardiac disease is vital to minimizing morbidity in adults with CF.

Respiratory muscle training improves respiratory muscle endurance but not exercise tolerance in children with cystic fibrosis

BACKGROUND

Respiratory muscle endurance (RME) training has been shown to increase exercise endurance and lung function in adults with cystic fibrosis (CF). We conducted an interventional study to investigate the effectiveness of RME training on CF-related health outcomes in children.

METHODS

In a crossover trial, 22 children, aged 9-18 years, with CF performed 8 weeks of RME training and standard chest physiotherapy in a randomized sequence separated by a 1 week washout period. All children underwent training sessions using the RME training device before beginning the study. The primary outcomes were RME (in minutes) and exercise endurance (in minutes). Data were analyzed according to the intention-to-treat principle.

RESULTS

Sixteen of 22 children (73%) completed the study. Study dropouts tended to be older with more advanced lung disease. After RME training, respiratory muscle endurance significantly increased by 7.03 ± 8.15 min (mean ± standard deviation, P < 0.001), whereas exercise endurance was unchanged by RME training (0.80 ± 2.58 min, P = 0.169). No significant improvement in secondary outcomes (lung function, CF quality of life, and CF clinical score) were observed. The small sample size and short intervention time have to be acknowledged as limitations of our study.

CONCLUSIONS

RME training led to a significant increase in respiratory muscle endurance in children with CF. However, RME training did not improve exercise endurance or other CF-related health outcomes. Thus, our results do not support the routine use of RME training in the care of children with CF. Future studies in larger populations and with prolonged intervention time may overcome the limitations of our study. Pediatr Pulmonol. 2017;52:331-336. © 2017 Wiley Periodicals, Inc.