Jeremy P. Wrobel

Mechanisms of pulmonary hypertension in chronic obstructive pulmonary disease: A pathophysiologic review

Chronic obstructive pulmonary disease (COPD) is a major cause of mortality and morbidity worldwide and is often complicated by the development of pulmonary hypertension (PHT). The presence of PHT in COPD subjects is associated with increased mortality, morbidity and use of health-care resources. Thus, there has been significant effort to treat PHT in COPD patients to achieve improved clinical outcomes, but with only minimal success. There is renewed interest in understanding the mechanisms contributing to PHT in COPD as the basis for exploring new therapeutic strategies. In this study we review the evidence supporting the postulated mechanisms contributing to PHT in COPD. Hypoxia plays a pivotal role in the development of COPD-associated PHT. However, other mechanisms are also likely involved in the pathogenesis of increased pulmonary vascular resistance in this cohort, including acidemia, dynamic pulmonary hyperinflation, parenchymal destruction, pulmonary vascular remodeling, endothelial dysfunction and inflammation. These mechanisms are interdependent, modulated by genetic factors, and may be confounded by comorbidities such as sleep-disordered breathing, left heart failure and pulmonary thromboembolism. Despite significant research in recent decades, there is surprisingly little evidence of a causal relationship between many of these factors and the development of COPD-associated PHT. The pathogenesis of PHT in COPD is complex and multifaceted. Ultimately, as we obtain better information on COPD phenotypes, we may be able to more precisely account for the varied pathologic mechanisms of PHT occurring in various COPD patients. This may ultimately enable targeted PHT therapy for each COPD phenotype.

Increased Dead Space Ventilation Mediates Reduced Exercise Capacity in Systolic Heart Failure.

RATIONALE Patients with chronic heart failure have limited exercise capacity, which cannot be completely explained by markers of cardiac dysfunction. Reduced pulmonary diffusing capacity at rest and excessively high ventilation during exercise are common in heart failure. We hypothesized that the reduced pulmonary diffusing capacity in patients with heart failure would predict greater dead space ventilation during exercise and that this would lead to impairment in exercise capacity. OBJECTIVES To determine the relationship between pulmonary diffusing capacity at rest and dead space ventilation during exercise, and to examine the influence of dead space ventilation on exercise in heart failure. METHODS We analyzed detailed cardiac and pulmonary data at rest and during maximal incremental cardiopulmonary exercise testing from 87 consecutive heart transplant assessment patients and 18 healthy control subjects. Dead space ventilation was calculated using the Bohr equation. MEASUREMENTS AND MAIN RESULTS Pulmonary diffusing capacity at rest was a significant predictor of dead space ventilation at maximal exercise (r = -0.524, P < 0.001) in heart failure but not in control subjects. Dead space at maximal exercise also correlated inversely with peak oxygen consumption (r = -0.598, P < 0.001), peak oxygen consumption per kilogram (r = -0.474, P < 0.001), and 6-minute-walk distance (r = -0.317, P = 0.021) in the heart failure group but not in control subjects. CONCLUSIONS Low resting pulmonary diffusing capacity in heart failure is indicative of high dead space ventilation during exercise, leading to excessive and inefficient ventilation. These findings would support the concept of pulmonary vasculopathy leading to altered ventilation perfusion matching (increased dead space) and resultant dyspnea, independent of markers of cardiac function.

Beta-blocker under-use in COPD patients

Background Cardiovascular (CVS) comorbidities are common in COPD and contribute significantly to morbidity and mortality, especially following acute exacerbations of COPD (AECOPD). Beta-blockers (BBs) are safe and effective in COPD patients, with demonstrated survival benefit following myocardial infarction. We sought to determine if BBs are under-prescribed in patients hospitalized with AECOPD. We also sought to determine inpatient rates of CVS and cerebrovascular complications, and their impact on patient outcomes. Methods Retrospective hospital data was collected over a 12-month period. The medical records of all patients >40 years of age coded with a diagnosis of AECOPD were analyzed. Prevalent use and incident initiation of BBs were assessed. Comorbidities including indications and contraindications for BB use were analyzed. Results Of the 366 eligible patients, 156 patients (42.6%) had at least one indication for BB use – of these patients, only 53 (34.0%) were on BB therapy and 61 (39.1%) were not on BB therapy but had no listed contraindication. Prevalent use of BBs at the time of admission in all 366 patients was 19.7%, compared with 45.6%, 39.6% and 45.9% use of anti-platelets, statins and angiotensin-converting enzyme inhibitor/angiotensin II receptor blockers, respectively. CVS and cerebrovascular complications were common in this population (57 patients, 16%) and were associated with longer length of stay (p<0.01) and greater inpatient mortality (p=0.02). Conclusions BBs are under-prescribed in COPD patients despite clear indication(s) for their use. Further work is required to explore barriers to BB prescribing in COPD patients.

Multicentre randomised placebo-controlled trial of oral anticoagulation with apixaban in systemic sclerosis-related pulmonary arterial hypertension: the SPHInX study protocol

Introduction Systemic sclerosis (SSc) is a severe and costly multiorgan autoimmune connective tissue disease characterised by vasculopathy and fibrosis. One of the major causes of SSc-related death is pulmonary arterial hypertension (PAH), which develops in 12–15% of patients with SSc and accounts for 30–40% of deaths. In situ thrombosis in the small calibre peripheral pulmonary vessels resulting from endothelial dysfunction and an imbalance of anticoagulant and prothrombotic mediators has been implicated in the complex pathophysiology of SSc-related PAH (SSc-PAH), with international clinical guidelines recommending the use of anticoagulants for some types of PAH, such as idiopathic PAH. However, anticoagulation has not become part of standard clinical care for patients with SSc-PAH as only observational evidence exists to support its use. Therefore, we present the rationale and methodology of a phase III randomised controlled trial (RCT) to evaluate the efficacy, safety and cost-effectiveness of anticoagulation in SSc-PAH. Methods and analysis This Australian multicentre RCT will compare 2.5 mg apixaban with placebo, in parallel treatment groups randomised in a 1:1 ratio, both administered twice daily for 3 years as adjunct therapy to stable oral PAH therapy. The composite primary outcome measure will be the time to death or clinical worsening of PAH. Secondary outcomes will include functional capacity, health-related quality of life measures and adverse events. A cost-effectiveness analysis of anticoagulation versus placebo will also be undertaken. Ethics and dissemination Ethical approval for this RCT has been granted by the Human Research Ethics Committees of all participating centres. An independent data safety monitoring board will review safety and tolerability data for the duration of the trial. The findings of this RCT are to be published in open access journals. Trial registration number ACTRN12614000418673, Pre-results.

Pulmonary arterial remodeling in chronic obstructive pulmonary disease is lobe dependent

Pulmonary arterial remodeling has been demonstrated in patients with severe chronic obstructive pulmonary disease (COPD), but it is not known whether lobar heterogeneity of remodeling occurs. Furthermore, the relationship between pulmonary hypertension (PH) and pulmonary arterial remodeling in COPD has not been established. Muscular pulmonary arterial remodeling in arteries 0.10–0.25 mm in diameter was assessed in COPD-explanted lungs and autopsy controls. Remodeling was quantified as the percentage wall thickness to vessel diameter (%WT) using digital image analysis. Repeat measures mixed-effects remodeling for %WT was performed according to lobar origin (upper and lower), muscular pulmonary arterial size (small, medium, and large), and echocardiography-based pulmonary arterial pressure (no PH, mild PH, and moderate-to-severe PH). Lobar perfusion and emphysema indices were determined from ventilation-perfusion and computed tomography scans, respectively. Overall, %WT was greater in 42 subjects with COPD than in 5 control subjects (P < 0.0001). Within the COPD group, %WT was greater in the upper lobes (P < 0.0001) and in the small muscular pulmonary arteries (P < 0.0001). Lobar differences were most pronounced in medium and large arteries. Lobar emphysema index was not associated with arterial remodeling. However, there was a significant positive relationship between the lobar perfusion index and pulmonary arterial remodeling (P = 0.024). The presence of PH on echocardiography showed only a trend to a small effect on lower lobe remodeling. The pattern of pulmonary arterial remodeling in COPD is complicated and lobe dependent. Differences in regional blood flow partially account for the lobar heterogeneity of pulmonary arterial remodeling in COPD.

The syndrome of inappropriate anti-diuretic hormone secretion concurrent with an acute exacerbation of cystic fibrosis

Acute exacerbations of cystic fibrosis (CF) can be associated with dehydration, hyponatraemia and hypochloraemia. The syndrome of inappropriate anti-diuretic hormone secretion (SIADH) has also been described in CF patients in the setting of hyponatraemia, but may be under-recognised. Diagnosing SIADH has therapeutic implications as it necessitates fluid and water restriction rather than fluid resuscitation. We report the case of an acute pulmonary exacerbation of CF in which features of SIADH are demonstrated.

Ventilation heterogeneity is increased in patients with chronic heart failure

In the healthy lung, ventilation is distributed heterogeneously due to factors such as anatomical asymmetry and gravity. This ventilation heterogeneity increases pathologically in conditions such as asthma, chronic obstructive lung disease, and cystic fibrosis. In chronic heart failure, lung biopsy demonstrates evidence of peripheral lung fibrosis and small airways narrowing and distortion. We hypothesized that this would lead to increased ventilation heterogeneity. Furthermore, we proposed that rostral fluid shifts when seated patients lie supine would further increase ventilation heterogeneity. We recruited 30 ambulatory chronic heart failure patients (57 ± 10 years, 83% male, left ventricular ejection fraction 31 ± 12%) as well as 10 healthy controls (51 ± 13 years, 90% male). Heart failure patients were clinically euvolemic. Subjects underwent measurement of ventilation heterogeneity using the multiple‐breath nitrogen washout technique in the seated position, followed by repeat measurements after 5 and 45 min in the supine position. Ventilation heterogeneity was calculated using the lung clearance index (LCI), Sacin and Scond which represent overall, acinar, and small conducting airway function, respectively. Lung clearance index (9.6 ± 1.2 vs. 8.6 ± 1.4 lung turnovers, P = 0.034) and Scond (0.029 ± 0.014 vs. 0.006 ± 0.016/L, P = 0.007) were higher in the heart failure patients. There was no difference in Sacin (0.197 ± 0.171 vs. 0.125 ± 0.081/L, P = 0.214). Measures of ventilation heterogeneity did not change in the supine position. This study confirms the presence of peripheral airway pathology in patients with chronic heart failure. This leads to subtle but detectable functional abnormalities which do not change after 45 min in the supine position.

Sjögren Syndrome With Associated Lymphocytic Interstitial Pneumonia Successfully Treated With Tacrolimus and Abatacept as an Alternative to Rituximab

Interstitial lung disease (ILD) is a significant complication of Sjögren syndrome (SS) associated with increased morbidity and mortality. The mainstay of treatment remains corticosteroid administration, with or without additional immunosuppressive therapies. Preliminary studies in SS have shown benefit in glandular and serologic parameters following treatment with the CTLA4 immunoglobulin fusion protein abatacept. Topical tacrolimus has been effective for ocular symptoms in SS, but systemic therapy has not been reported. We describe the first case, to our knowledge, of the successful use of a combination of systemic tacrolimus and abatacept in severe refractory SS and related ILD.

Maximal exercise does not increase ventilation heterogeneity in healthy trained adults

The effect of exercise on ventilation heterogeneity has not been investigated. We hypothesized that a maximal exercise bout would increase ventilation heterogeneity. We also hypothesized that increased ventilation heterogeneity would be associated with exercise‐induced arterial hypoxemia (EIAH). Healthy trained adult males were prospectively assessed for ventilation heterogeneity using lung clearance index (LCI), Scond, and Sacin at baseline, postexercise and at recovery, using the multiple breath nitrogen washout technique. The maximal exercise bout consisted of a maximal, incremental cardiopulmonary exercise test at 25 watt increments. Eighteen subjects were recruited with mean ± SD age of 35 ± 9 years. There were no significant changes in LCI, Scond, or Sacin following exercise or at recovery. While there was an overall reduction in SpO2 with exercise (99.3 ± 1 to 93.7 ± 3%, P < 0.0001), the reduction in SpO2 was not associated with changes in LCI, Scond or Sacin. Ventilation heterogeneity is not increased following a maximal exercise bout in healthy trained adults. Furthermore, EIAH is not associated with changes in ventilation heterogeneity in healthy trained adults.

Under-utilisation of β-blockers in patients with acute coronary syndrome and comorbid chronic obstructive pulmonary disease: β-blockers in COPD patients

β‐blockers are an established mainstay of therapy in acute coronary syndrome (ACS). Despite substantial evidence of their safety and efficacy in chronic obstructive pulmonary disease (COPD) patients, their use in this population remains limited internationally, likely due to fears of inducing bronchospasm. In Australia, little is known about the use of β‐blockers in COPD patients hospitalised for ACS.