Subclinical Left Ventricular Dysfunction is Influenced by Genotype Severity in Patients with Cystic Fibrosis

Subclinical vascular, hemodynamic and arterial stiffness changes in adults with cystic fibrosis: cross-sectional observational study

Cardiovascular diseases can be an emerging complication in cystic fibrosis (CF), as the median life expectancy has improved considerably. The objective of this study was to compare vascular, hemodynamic parameters and arterial stiffness in adult CF patients with healthy participants pared by sex and age, and to assess the factors associated with arterial stiffness in the CF group. This is a cross-sectional observational study. The evaluation of cardiovascular parameters was performed non-invasively using Mobil-O-Graph. 36 individuals with CF and 35 controls were evaluated. The mean arterial pressure (96.71 ± 10.98 versus 88.61 ± 7.40 mmHg, p = 0.0005), cardiac output (4.86 ± 0.57 versus 4.48 ± 0.44 L/min, p = 0.002) and systolic volume (64.30 ± 11.91 versus 49.02 ± 9.31 ml, p < 0.0001) were significantly lower in the CF group. The heart rate was higher in the CF when compared to the control (77.18 ± 10.47 versus 93.56 ± 14.57 bpm, p < 0.0001). The augmentation index (AIx@75) was higher in the CF than control (29.94 ± 9.37 versus 16.52 ± 7.179%, p < 0.0001). In the multivariate model controlled by body mass index and Forced Expiratory Volume in the first second, central systolic blood pressure and reflection coefficient directly related to AIx@75. Negatively related to AIx@75 were age and systolic volume. The adjusted determination coefficient was 87.40%. Individuals with CF presented lower arterial blood pressures and changes in cardiac function with lower stroke volume and cardiac output. The AIx@75, an indirect index of arterial stiffness and direct index of left ventricular overload, is increased in this population. The subclinical findings suggest the need for earlier cardiovascular assessment in this population due to increased risks of cardiovascular disease.

Exercise intolerance in cystic fibrosis-the role of CFTR modulator therapies

Exercise intolerance is common in people with CF (pwCF), but not universal among all individuals. While associated with disease prognosis, exercise intolerance is not simply a reflection of the degree of lung disease. In people with severe CF, respiratory limitations may contribute more significantly to impaired exercise capacity than in those with mild-moderate CF. At all levels of disease severity, there are peripheral factors e.g., abnormal macro- and micro-vascular function that impair blood flow and reduce oxygen extraction, and mitochondrial defects that diminish metabolic efficiency. We discuss advances in understanding the central and peripheral mechanisms underlying exercise intolerance in pwCF. Exploring both the central and peripheral factors that contribute to exercise intolerance in CF can help inform the development of new therapeutic targets, as well as help define prognostic criteria.

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.

Heterozygous Cystic Fibrosis Transmembrane Regulator Gene Missense Variants Are Associated With Worse Cardiac Function in Patients With Duchenne Muscular Dystrophy

Background

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder caused by mutations within the dystrophin gene. DMD is characterized by progressive skeletal muscle degeneration and atrophy and progressive cardiomyopathy. It has been observed the severity of cardiomyopathy varies in patients with DMD.

Methods and Results

A cohort of male patients with DMD and female DMD carriers underwent whole exome sequencing. Potential risk factor variants were identified according to their functional annotations and frequencies. Cardiac function of 15 male patients with DMD was assessed by cardiac magnetic resonance imaging, and various cardiac magnetic resonance imaging parameters and circulating biomarkers were compared between genotype groups. Five subjects carrying potential risk factor variants in the cystic fibrosis transmembrane regulator gene demonstrated lower left ventricular ejection fraction, larger left ventricular end‐diastolic volume, and higher NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) levels compared with 10 subjects who did not carry the potential risk factor variants (P=0.023, 0.019 and 0.028, respectively).

Conclusions

This study revealed heterozygous cystic fibrosis transmembrane regulator gene missense variants were associated with worse cardiac function in patients with DMD. The cystic fibrosis transmembrane regulator gene may serve as a genetic modifier that accounts for more severe cardiomyopathy in patients with DMD, who would require more aggressive management of the cardiomyopathy.

Re-imagining cystic fibrosis care: next generation thinking

Cystic fibrosis (CF) is a common multi-system genetically inherited condition, predominately found in individuals of Caucasian decent. Since the identification of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) gene in 1989, and the subsequent improvement in understanding of CF pathophysiology, significant increases in life-expectancy have followed. Initially this was related to improvements in the management and systems of care for treating the various affected organ systems. These cornerstone treatments are still essential for CF patients born today. However, over the last decade, the major advance has been in therapies that target the resultant genetic defect: the dysfunctional CFTR protein. Small molecule agents that target this dysfunctional protein via a variety of mechanisms have led to lung function improvements, reductions in pulmonary exacerbation rates and increases in weight and quality-of-life indices. As more patients receive these agents earlier and earlier in life, it is likely that general CF care will increasingly pivot around these specific therapies, although it is also likely that effects other than those identified in the initial trials will be discovered and need to be managed. Despite great excitement for modulator therapies, they are unlikely to be suitable or available for all; whether this is due to a lack of availability for specific CFTR mutations, drug-reactions or the health economic set-up in certain countries. Nevertheless, the CF community must be applauded for its ongoing focus on research and development for this life-limiting disease. With time, personalised individualised therapy would ideally be the mainstay of CF care.

Cystic fibrosis - an example of personalized and precision medicine

Cystic fibrosis (CF) is a severe, monogenic, autosomal recessive disease caused by mutations in the CFTR (cystic fibrosis transmembrane regulator) gene, where disturbed chloride and bicarbonate transportation in epithelial cells results in a multiorgan disease with primarily pulmonary infections and pancreatic insufficiency. In 1968, the Copenhagen CF Center was established, and centralized care of CF patients with monthly control was introduced. Close monitoring and treatment of Pseudomonas lung infection as well as segregation of patients with different infection status improved the clinical outcome as well as survival. Prophylactic basic treatment as well as infection treatments follow specific algorithms. A variety of comorbidities have all along the pulmonary infection control necessitated personalized care, adjusted to the patients' phenotype. With the introduction of CFTR modulators, the treatment has shifted from prophylactic, symptomatic type toward a new era of precision medicine targeting the basic defect according to the patients' CFTR genotype. Future directions will focus on further improvement of the CFTR modulators and gene therapy, as well as modifier genes and CF phenotype.