Diffusion capacity and haemodynamics in primary and chronic thromboembolic pulmonary hypertension

Sex-specific differences in sleep-disordered breathing and nocturnal hypoxemia in chronic thromboembolic pulmonary hypertension and chronic thromboembolic pulmonary disease

Objective

Although chronic thromboembolic pulmonary hypertension (CTEPH) and chronic thromboembolic pulmonary disease (CTEPD) are known to be accompanied by symptoms associated with sleep-disordered breathing (SDB) and nocturnal hypoxemia, the sex-specific differences of SDB and nocturnal hypoxemia in patients with CTEPH and CTEPD remain unknown.

Methods

Between July 2020 and August 2022, data were retrieved from 57 males and 63 female patients with CTEPH and CTEPD who underwent sleep study at Shanghai Pulmonary Hospital. Nocturnal mean SpO₂ (mean SpO₂) < 90% was defined as nocturnal hypoxemia. Logistic and linear regression analysis was performed to assess the predictive value of sleep study indices to hemodynamic parameters. Receiver operating characteristic (ROC) curve was applied to analyze the specific parameters to predict the risk of CTEPH.

Results

SDB was similarly present in males and females, and both sexes predominantly had obstructive sleep apnea (OSA); more women were diagnosed with nocturnal hypoxemia (32 vs. 7%, p = 0.002). SaO₂ was negatively associated with mean pulmonary arterial pressure (mPAP) in men (p < 0.001), whereas the ratio of nocturnal SpO₂ < 90% of the total monitoring time (T90%) was positively correlated with mPAP. Mean SpO₂ was an independent predictor for pulmonary vascular resistance and cardiac output in women (p = 0.001, p < 0.001, p = 0.001, respectively). T90%, SaO₂, and minimal SpO₂ were combined to develop a new composite parameter: hypoxemia scoring index (HSI). ROC curve analysis indicated that HSI levels of 0.55 could discriminate CTEPH from CTEPD with a sensitivity of 92.3% and specificity of 87.5% in female patients (an area under the curve, 0.937; 95% CI: 0.879–0.995, p < 0.001).

Conclusion

Sex-specific nocturnal hypoxemia was present in patients with CTEPH or CTEPD. In female patients, the HSI showed high capacity for predicting the risk of CTEPH.

Clinical trials registration

Registry: chictr.org.cn; Identifier: ChiCTR-DDD-16009406.

Different response of the oxygen pathway in patients with chronic thromboembolic pulmonary hypertension treated with pulmonary endarterectomy versus balloon pulmonary angioplasty

Background

Oxygen pathway limitation exists in chronic thromboembolic pulmonary hypertension (CTEPH). Pulmonary endarterectomy (PEA) and balloon pulmonary angioplasty (BPA) are two effective interventions for CTEPH, but their effects and comparison of these two interventions on the oxygen pathway are not well demonstrated.

Methods

CTEPH patients with available pulmonary function test, hemodynamics, and blood gas analysis before and after the interventions were included for comparison of oxygen pathway in terms of lung ventilation, lung gas exchange, oxygen delivery, and oxygen extraction between these two interventions.

Results

The change in the percentage of the predicted forced expiratory volume in the 1 s (−3.4 ± 12.7 vs. 3.8 ± 8.7%, P = 0.006) and forced vital capacity (−5.5 ± 13.0 vs. 4.2 ± 9.9%, P = 0.001) among the PEA group (n = 24) and BPA group (n = 46) were significantly different. Patients in the PEA group had a significant increase in their arterial oxygen saturation (from 92.5 ± 3.6 to 94.6 ± 2.4%, P = 0.022), while those in the BPA group had no change, which could be explained by a significant improvement in ventilation/perfusion (−0.48 ± 0.53 vs. −0.17 ± 0.41, P = 0.016). Compared with patients post-BPA, patients post-PEA were characterized by higher oxygen delivery (756.3 ± 229.1 vs. 628.8 ± 188.5 ml/min, P = 0.016) and higher oxygen extraction (203.3 ± 64.8 vs. 151.2 ± 31.9 ml/min, P = 0.001).

Conclusion

Partial amelioration of the oxygen pathway limitations could be achieved in CTEPH patients treated with PEA and BPA. CTEPH patients post-PEA had better performance in lung gas exchange, oxygen delivery, and extraction, while those post-BPA had better lung ventilation. Cardiopulmonary rehabilitation may assist in improving the impairment of the oxygen pathway.

PHD2 deletion in endothelial or arterial smooth muscle cells reveals vascular cell type-specific responses in pulmonary hypertension and fibrosis

Hypoxia plays an important regulatory role in the vasculature to adjust blood flow to meet metabolic requirements. At the level of gene transcription, the responses are mediated by hypoxia-inducible factor (HIF) the stability of which is controlled by the HIF prolyl 4-hydroxylase-2 (PHD2). In the lungs hypoxia results in vasoconstriction, however, the pathophysiological relevance of PHD2 in the major arterial cell types; endothelial cells (ECs) and arterial smooth muscle cells (aSMCs) in the adult vasculature is incompletely characterized. Here, we investigated PHD2-dependent vascular homeostasis utilizing inducible deletions of PHD2 either in ECs (Phd2^∆ECi) or in aSMCs (Phd2^∆aSMC). Cardiovascular function and lung pathologies were studied using echocardiography, Doppler ultrasonography, intraventricular pressure measurement, histological, ultrastructural, and transcriptional methods. Cell intrinsic responses were investigated in hypoxia and in conditions mimicking hypertension-induced hemodynamic stress. Phd2^∆ECi resulted in progressive pulmonary disease characterized by a thickened respiratory basement membrane (BM), alveolar fibrosis, increased pulmonary artery pressure, and adaptive hypertrophy of the right ventricle (RV). A low oxygen environment resulted in alterations in cultured ECs similar to those in Phd2^∆ECi mice, involving BM components and vascular tone regulators favoring the contraction of SMCs. In contrast, Phd2^∆aSMC resulted in elevated RV pressure without alterations in vascular tone regulators. Mechanistically, PHD2 inhibition in aSMCs involved  actin polymerization -related tension development via activated cofilin. The results also indicated that hemodynamic stress, rather than PHD2-dependent hypoxia response alone, potentiates structural remodeling of the extracellular matrix in the pulmonary microvasculature and respiratory failure.

Perioperative Management of Pulmonary Hypertension. a Review

Pulmonary hypertension is a rare and progressive pathology defined by abnormally high pulmonary artery pressure mediated by a diverse range of aetiologies. It affects up to twenty-six individuals per one million patients currently living in the United Kingdom (UK), with a median life expectancy of 2.8 years in idiopathic pulmonary hypertension. The diagnosis of pulmonary hypertension is often delayed due to the presentation of non-specific symptoms, leading to a delay in referral to specialists services. The complexity of treatment necessitates a multidisciplinary approach, underpinned by a diverse disease aetiology from managing the underlying disease process to novel specialist treatments. This has led to the formation of dedicated specialist treatment centres within centralised UK cities. The article aimed to provide a concise overview of pulmonary hypertension’s clinical perioperative management, including key definitions, epidemiology, pathophysiology, and risk stratification.

Oxygen Pathway Limitations in Patients With Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

Exertional intolerance is a limiting and often crippling symptom in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Traditionally the pathogenesis has been attributed to central factors, including ventilation/perfusion mismatch, increased pulmonary vascular resistance, and right heart dysfunction and uncoupling. Pulmonary endarterectomy and balloon pulmonary angioplasty provide substantial improvement of functional status and hemodynamics. However, despite normalization of pulmonary hemodynamics, exercise capacity often does not return to age-predicted levels. By systematically evaluating the oxygen pathway, we aimed to elucidate the causes of functional limitations in patients with CTEPH before and after pulmonary vascular intervention.

METHODS

Using exercise cardiac magnetic resonance imaging with simultaneous invasive hemodynamic monitoring, we sought to quantify the steps of the O₂ transport cascade from the mouth to the mitochondria in patients with CTEPH (n=20) as compared with healthy participants (n=10). Furthermore, we evaluated the effect of pulmonary vascular intervention (pulmonary endarterectomy or balloon angioplasty) on the individual components of the cascade (n=10).

RESULTS

Peak Vo₂ (oxygen uptake) was significantly reduced in patients with CTEPH relative to controls (56±17 versus 112±20% of predicted; P<0.0001). The difference was attributable to impairments in multiple steps of the O₂ cascade, including O₂ delivery (product of cardiac output and arterial O₂ content), skeletal muscle diffusion capacity, and pulmonary diffusion. The total O₂ extracted in the periphery (ie, ΔAVo₂ [arteriovenous O₂ content difference]) was not different. After pulmonary vascular intervention, peak Vo₂ increased significantly (from 12.5±4.0 to 17.8±7.5 mL/[kg·min]; P=0.036) but remained below age-predicted levels (70±11%). The O₂ delivery was improved owing to an increase in peak cardiac output and lung diffusion capacity. However, peak exercise ΔAVo₂ was unchanged, as was skeletal muscle diffusion capacity.

CONCLUSIONS

We demonstrated that patients with CTEPH have significant impairment of all steps in the O₂ use cascade, resulting in markedly impaired exercise capacity. Pulmonary vascular intervention increased peak Vo₂ by partly correcting O₂ delivery but had no effect on abnormalities in peripheral O₂ extraction. This suggests that current interventions only partially address patients' limitations and that additional therapies may improve functional capacity.

Chronic Thromboembolic Pulmonary Hypertension: JACC Focus Seminar

Chronic thromboembolic pulmonary hypertension (CTEPH) is the result of pulmonary arterial obstruction by organized thrombotic material stemming from incompletely resolved acute pulmonary embolism. The exact incidence of CTEPH is unknown but appears to approximate 2.3% among survivors of acute pulmonary embolism. Although ventilation/perfusion scintigraphy has been supplanted by computed tomographic pulmonary angiography in the diagnostic approach to acute pulmonary embolism, it has a major role in the evaluation of patients with suspected CTEPH, the presence of mismatched segmental defects being consistent with the diagnosis. Diagnostic confirmation of CTEPH is provided by digital subtraction pulmonary angiography, preferably performed at a center familiar with the procedure and its interpretation. Operability assessment is then undertaken to determine if the patient is a candidate for potentially curative pulmonary endarterectomy surgery. When pulmonary endarterectomy is not an option, pulmonary arterial hypertension-targeted pharmacotherapy and balloon pulmonary angioplasty represent potential therapeutic alternatives.

The prognostic value of DLCO and pulmonary blood flow in patients with pulmonary hypertension

Background

Cardiac output is a prognostic marker in patients with pulmonary hypertension. Pulmonary blood flow as a surrogate for cardiac output can be measured non-invasively by inert gas rebreathing. We hypothesized that pulmonary blood flow can predict outcome in patients with pulmonary hypertension.

Methods

From January 2009 to January 2012, we measured pulmonary blood flow by inert gas rebreathing in outpatients with pulmonary hypertension. Patients with pulmonary hypertension confirmed by right heart catheterization and a valid inert gas rebreathing maneuver were followed until January 2016. The investigated outcome was all-cause mortality.

Results

We included 259 patients (mean age 65 ± 13 years, 53% female) with pulmonary hypertension and classified into groups 1 (n = 103), 2 (n = 26), 3 (n = 80), and 4 (n = 50) according to the current pulmonary hypertension classification system. The median time between pulmonary hypertension diagnosis and inert gas rebreathing was 9 (IQR 0; 36) months. During a median follow-up time of 51 (IQR 20; 68) months, 109 patients (42%) died. Parameters significantly associated with survival (in order of decreasing statistical strength) were diffusion capacity of the lung for carbon monoxide (DLCO), 6-minute walk distance (6-MWD), age, NTpro-BNP, WHO functional class, group 3 pulmonary hypertension, and tricuspid annular plane systolic excursion (TAPSE), while baseline hemodynamics and pulmonary blood flow were not. In multivariable Cox regression analysis, DLCO, age, 6-MWD, and TAPSE remained significant and independent predictors of the outcome. DLCO as the strongest parameter also significantly predicted survival in aetiological subgroups except for group 4.

Conclusions

DLCO is a strong and independent predictor for survival in patients with pulmonary hypertension of different aetiologies, while pulmonary blood flow measured by inert gas rebreathing is not.

Chronic Thromboembolic Pulmonary Hypertension: Evolving Therapeutic Approaches for Operable and Inoperable Disease

Chronic thromboembolic pulmonary hypertension (CTEPH), a rare consequence of an acute pulmonary embolism, is a disease that is underdiagnosed, and surgical pulmonary thromboendarterectomy (PTE) remains the preferred therapy. However, determination of operability is multifactorial and can be challenging. There is growing excitement for the percutaneous treatment of inoperable CTEPH with data from multiple centers around the world showing the clinical feasibility of balloon pulmonary angioplasty. Riociguat remains the only approved medical therapy for CTEPH patients deemed inoperable or with persistent pulmonary hypertension after PTE. We recommend that expert multidisciplinary CTEPH teams be developed at individual institutions. Additionally, optimal and standardized techniques for balloon pulmonary angioplasty need to be developed along with dedicated interventional equipment and appropriate training standards. In the meantime, the percutaneous revascularization option is appropriate for patients deemed inoperable in combination with targeted medical therapy, or those who have failed to benefit from surgery.

Independent Prognostic Value of Pulmonary Diffusing Capacity in Nonsmoking Patients with Chronic Heart Failure

The diffusing capacity of the lung for carbon monoxide (DLCO) is indicative of the alveolar-capillary membrane function. A reduced DLCO is associated with poor prognosis in chronic heart failure (HF). However, the significance of DLCO as an independent prognostic predictor has not been established. Here, we aimed to determine the prognostic value of DLCO in patients with chronic HF.We enrolled 214 patients (139 females, mean age: 63 ± 16 years, left ventricular ejection fraction [LVEF]: 45 ± 21%) with stable chronic HF who underwent pulmonary function tests. Only never smokers were included in the analysis because smoking can decrease DLCO.During a median follow-up period of 2.1 years, 52 patients (24.3%) experienced cardiac events, including unplanned HF admissions, left ventricular assist device (LVAD) implantations, all-cause deaths, and cardiopulmonary arrests (CPAs). The median percent predicted DLCO (%DLCO) was 87.3%. In a Cox regression analysis, a %DLCO of ≤87.3% was independently associated with the cardiac events, even after adjusting for age, sex, systolic blood pressure (SBP), LVEF, anemia, brain natriuretic peptide, estimated glomerular filtration rate (eGFR), and prior HF admission (hazard ratio [HR]: 1.87, 95% confidence interval: 1.03-3.53, P = 0.030).A reduced DLCO is an independent predictor of poor prognosis in nonsmoking patients with chronic HF.

Lung-diffusing capacity for carbon monoxide predicts early complications after cardiac surgery

PURPOSE

Preoperative pulmonary dysfunction has been associated with increased operative mortality and morbidity after cardiac surgery. This study aimed to determine whether values for the diffusing capacity of the lung for carbon monoxide (DL_CO) could predict postoperative complications after cardiac surgery.

METHODS

This study included 408 consecutive patients who underwent cardiac surgery between June 2008 and December 2015. DL_CO was routinely determined in all patients. A reduced DL_CO was clinically defined as %DL_CO < 70%. %DL_CO was calculated as DL_CO divided by the predicted DL_CO. The association between %DL_CO and in-hospital mortality was assessed, and independent predictors of complications were identified by a logistic regression analysis.

RESULTS

Among the 408 patients, 338 and 70 had %DL_CO values of ≥ 70% and < 70%, respectively. Complications were associated with in-hospital mortality (P < 0.001), but not %DL_CO (P = 0.275). A multivariate logistic regression analysis with propensity score matching identified reduced DL_CO as an independent predictor of complications (OR, 3.270; 95%CI, 1.356-7.882; P = 0.008).

CONCLUSIONS

%DL_CO is a powerful predictor of postoperative complications. The preoperative DL_CO values might provide information that can be used to accurately predict the prognosis after cardiac surgery.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000029985.

Factors predicting outcome after pulmonary endarterectomy

Objective

Few studies have reported predictive factors of outcome after pulmonary endarterectomy (PEA) in chronic thromboembolic pulmonary hypertension. The purpose of this study was to determine factors influencing mortality and predictors of hemodynamic improvement after PEA.

Methods

A total of 383 consecutive patients who underwent PEA between January 2005 and December 2009 were retrospectively reviewed. Among them, 150 were fully reevaluated 7.5±1 months after PEA by NYHA class, 6–minute walk distance (6MWD), percentage of predicted carbon monoxide transfer factor (TL_CO) and right heart catheterisation.

Results

Mortality rates at 1 month, 1 year and 3 years were 2.8%, 6.9% and 7.5%, respectively. Preoperative pulmonary vascular resistance (PVR) independently predicted 1-month, 1- and 3-year mortality and age predicted mortality at 1 year and 3 years. Significant improvement in NYHA class and 6MWD were observed and PVR decreased from 773±353 to 307±221 dyn.sec.cm^-5 (p<0.001). In 96 patients (64%), PVR decreased by at least 50% and/or was reduced to lower than 250 dyn.sec.cm^-5. Preoperative cardiac output (CO) and TL_CO predicted hemodynamic improvement.

Conclusion

PEA is associated with an excellent long-term survival and a marked improvement in clinical status and hemodynamics. Some preoperative factors including PVR, CO and TL_CO can predict postoperative outcomes.

Chronic obstructive pulmonary disease in patients with chronic thromboembolic pulmonary hypertension: Prevalence and implications for surgical treatment outcome

OBJECTIVE

The aim of our study was to investigate the prevalence of chronic obstructive pulmonary disease (COPD) in patients with chronic thromboembolic pulmonary hypertension (CTEPH) and examine their impact on the results of pulmonary thrombendarterectomy (PEA).

METHODS

We enrolled 136 patients with CTEPH who scheduled for elective PEA. Pulmonary function tests (PFTs) including full-body plethysmography with bronchodilation test and lung diffusion capacity assessment were performed in all patients prior to surgery treatment. The diagnosis of COPD was verified in accordance with the recommendations of the Global Initiative for Chronic Obstructive Lung Disease 2017. The effect of COPD on perioperative characteristics, complications, in-hospital and one-year mortality of patients with CTEPH were analysed.

RESULTS

In the study group with CTEPH the prevalence of COPD was 23%. In 13% of patients, COPD was first detected. The results of PFTs showed more severe airflow limitations with obstructive pattern in patients with concomitant COPD, as well as a more pronounced decrease in the lung diffusion capacity. The presence of COPD in patients with CTEPH significantly increases the risk of residual pulmonary hypertension in the early postoperative period of PEA (OR = 6.2 (1.90-10.27), P = .002), duration of hospital stay (OR = 1.1 (1.01-1.20), P = .020) and the risk of in-hospital mortality (OR = 4.4 (1.21-16.19), P = .023). The lung diffusion capacity revealed significant negative associations with the duration of hospital stay and in-hospital mortality (OR 0.87 (0.74-0.98), P = .012).

CONCLUSION

COPD in patients with CTEPH significantly increases the risk of residual pulmonary hypertension, in-hospital mortality and increases the duration of hospital stay after PEA.

Effects of exercise training on pulmonary hemodynamics, functional capacity and inflammation in pulmonary hypertension

Pulmonary hypertension (PH) is characterized by severe exercise limitation mainly attributed to the impairment of right ventricular function resulting from a concomitant elevation of pulmonary vascular resistance and pressure. The unquestioned cornerstone in the management of patients with pulmonary arterial hypertension (PAH) is specific vasoactive medical therapy to improve pulmonary hemodynamics and strengthen right ventricular function. Nevertheless, evidence for a beneficial effect of exercise training (ET) on pulmonary hemodynamics and functional capacity in patients with PH has been growing during the past decade. Beneficial effects of ET on regulating factors, inflammation, and metabolism have also been described. Small case-control studies and randomized clinical trials in larger populations of patients with PH demonstrated substantial improvements in functional capacity after ET. These findings were accompanied by several studies that suggested an effect of ET on inflammation, although a direct link between this effect and the therapeutic benefit of ET in PH has not yet been demonstrated. On this background, the aim of the present review is to describe current concepts regarding the effects of exercise on the pulmonary circulation and pathophysiological limitations, as well as the clinical and mechanistic effects of exercise in patients with PH.

Advances in the Evaluation of Respiratory Pathophysiology during Exercise in Chronic Lung Diseases

Dyspnea and exercise limitation are among the most common symptoms experienced by patients with various chronic lung diseases and are linked to poor quality of life. Our understanding of the source and nature of perceived respiratory discomfort and exercise intolerance in chronic lung diseases has increased substantially in recent years. These new mechanistic insights are the primary focus of the current review. Cardiopulmonary exercise testing (CPET) provides a unique opportunity to objectively evaluate the ability of the respiratory system to respond to imposed incremental physiological stress. In addition to measuring aerobic capacity and quantifying an individual's cardiac and ventilatory reserves, we have expanded the role of CPET to include evaluation of symptom intensity, together with a simple "non-invasive" assessment of relevant ventilatory control parameters and dynamic respiratory mechanics during standardized incremental tests to tolerance. This review explores the application of the new advances in the clinical evaluation of the pathophysiology of exercise intolerance in chronic obstructive pulmonary disease (COPD), chronic asthma, interstitial lung disease (ILD) and pulmonary arterial hypertension (PAH). We hope to demonstrate how this novel approach to CPET interpretation, which includes a quantification of activity-related dyspnea and evaluation of its underlying mechanisms, enhances our ability to meaningfully intervene to improve quality of life in these pathologically-distinct conditions.

Impact of Increasing Age on Cause-Specific Mortality and Morbidity in Patients With Stage I Non-Small-Cell Lung Cancer: A Competing Risks Analysis

Purpose To perform competing risks analysis and determine short- and long-term cancer- and noncancer-specific mortality and morbidity in patients who had undergone resection for stage I non-small-cell lung cancer (NSCLC). Patients and Methods Of 5,371 consecutive patients who had undergone curative-intent resection of primary lung cancer at our institution (2000 to 2011), 2,186 with pathologic stage I NSCLC were included in the analysis. All preoperative clinical variables known to affect outcomes were included in the analysis, specifically, Charlson comorbidity index, predicted postoperative (ppo) diffusing capacity of the lung for carbon monoxide, and ppo forced expiratory volume in 1 second. Cause-specific mortality analysis was performed with competing risks analysis. Results Of 2,186 patients, 1,532 (70.1%) were ≥ 65 years of age, including 638 (29.2%) ≥ 75 years of age. In patients < 65, 65 to 74, and ≥ 75 years of age, 5-year lung cancer-specific cumulative incidence of death (CID) was 7.5%, 10.7%, and 13.2%, respectively (overall, 10.4%); noncancer-specific CID was 1.8%, 4.9%, and 9.0%, respectively (overall, 5.3%). In patients ≥ 65 years of age, for up to 2.5 years after resection, noncancer-specific CID was higher than lung cancer-specific CID; the higher noncancer-specific, early-phase mortality was enhanced in patients ≥ 75 years of age than in those 65 to 74 years of age. Multivariable analysis showed that low ppo diffusing capacity of lung for carbon monoxide was an independent predictor of severe morbidity ( P < .001), 1-year mortality ( P < .001), and noncancer-specific mortality ( P < .001), whereas low ppo forced expiratory volume in 1 second was an independent predictor of lung cancer-specific mortality ( P = .002). Conclusion In patients who undergo curative-intent resection of stage I NSCLC, noncancer-specific mortality is a significant competing event, with an increasing impact as patient age increases.

An Update on the Management of Chronic Thromboembolic Pulmonary Hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but life-threatening form of pulmonary artery hypertension that is defined as a mean arterial pulmonary pressure greater than 25mmHg that persists for more than 6 months following anticoagulation therapy in the setting of pulmonary emboli. CTEPH is categorized by the World Health Organization as group IV pulmonary hypertension and is thought to be due to unresolved thromboemboli in the pulmonary artery circulation. Among the 5 classes of pulmonary hypertension, CTEPH is unique in that it is potentially curable with the use of pulmonary thromboendarterectomy surgery. Despite an increasing array of medical and surgical treatment options for patients with CTEPH over the past 2 decades, patients commonly present with advanced disease and carry a poor prognosis, thus, the need for early diagnosis and appropriate referral to an expert center. This review article first highlights the epidemiology, pathophysiology, and clinical presentation of CTEPH. The article then provides diagnostic and therapeutic algorithms for the management of the patient with suspected CTEPH.

Effects of Balloon Pulmonary Angioplasty on Oxygenation in Patients With Chronic Thromboembolic Pulmonary Hypertension - Importance of Intrapulmonary Shunt

BACKGROUND

Although balloon pulmonary angioplasty (BPA) improves the hemodynamics and prognosis of patients with inoperable chronic thromboembolic pulmonary hypertension (CTEPH), the mechanisms of improvement in oxygenation remain to be elucidated.

METHODS AND RESULTS

From August 2013 to May 2015, we performed a total of 113 BPA procedures in 24 patients with inoperable CTEPH (mean 4.7 procedures per patient). Median age was 70 [60, 74] years and 18 were female (75%). We examined hemodynamics, respiratory functions, and intrapulmonary shunt before and after the BPA procedure. Mean pulmonary arterial pressure (37 [28, 45] to 23[19, 27] mmHg, P<0.01), pulmonary vascular resistance (517 [389, 696] to 268 [239, 345] dyne/s/cm(5)) and 6-min walk distance (390 [286, 484] to 490 [411, 617] m, P<0.01) were significantly improved after BPA therapy. Furthermore, arterial oxygen partial pressure (PaO2, 54.8 [50.0, 60.8] to 65.2 [60.6, 73.2] %, P<0.01) and intrapulmonary shunt (23.4±6.0% to 19.3±5.0%, P<0.01) were also significantly ameliorated. In the multivariate analysis, decrease in intrapulmonary shunt after BPA was significantly correlated with improvement of both PaO2(r(2)=0.26, P<0.01) and SaO2(r(2)=0.49, P<0.01) after BPA.

CONCLUSIONS

These results indicated that BPA improved not only pulmonary hemodynamics but also oxygenation with a resultant decrease in intrapulmonary shunt. (Circ J 2016; 80: 2227-2234).

Severe Pulmonary Arteriopathy Is Associated with Persistent Hypoxemia after Pulmonary Endarterectomy in Chronic Thromboembolic Pulmonary Hypertension

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) is characterized by occlusion of pulmonary arteries by organized chronic thrombi. Persistent hypoxemia and residual pulmonary hypertension (PH) following successful pulmonary endarterectomy (PEA) are clinically important problems; however, the underlying mechanisms remain unclear. We have previously reported that residual PH is closely related to severe pulmonary vascular remodeling and hypothesize that this arteriopathy might also be involved in impaired gas exchange. The purpose of this study was to evaluate the association between hypoxemia and pulmonary arteriopathy after PEA.

METHODS AND RESULTS

Between December 2011 and November 2014, 23 CTEPH patients underwent PEA and lung biopsy. The extent of pulmonary arteriopathy was quantified pathologically in lung biopsy specimens. We then analyzed the relationship between the severity of pulmonary arteriopathy and gas exchange after PEA. We observed that the severity of pulmonary arteriopathy was negatively correlated with postoperative and follow-up PaO2 (postoperative PaO2: r = -0.73, p = 0.0004; follow-up PaO2: r = -0.66, p = 0.001), but not with preoperative PaO2 (r = -0.373, p = 0.08). Multivariate analysis revealed that the obstruction ratio and patient age were determinants of PaO2 one month after PEA (R2 = 0.651, p = 0.00009). Furthermore, the obstruction ratio and improvement of pulmonary vascular resistance were determinants of PaO2 at follow-up (R2 = 0.545, p = 0.0002). Severe pulmonary arteriopathy might increase the alveolar-arterial oxygen difference and impair diffusion capacity, resulting in hypoxemia following PEA.

CONCLUSION

The severity of pulmonary arteriopathy was closely associated with postoperative and follow-up hypoxemia.

Diffusion Capacity and Mortality in Patients With Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction

OBJECTIVES

This study sought to investigate the prognostic importance of a low diffusion capacity of the lung for carbon monoxide (DLCO) in patients with a catheter-based diagnosis of pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF).

BACKGROUND

In patients with pulmonary arterial hypertension, a low DLCO is associated with poor outcome. It is unclear whether the same is true in patients with PH-HFpEF.

METHODS

This study retrospectively analyzed clinical characteristics, smoking history, lung function measurements, chest computed tomography, hemodynamics, and survival in 108 patients with PH-HFpEF. The presence of post-capillary PH was determined by right heart catheterization. Patients with moderate or severe lung function abnormalities were excluded.

RESULTS

On the basis of previous studies and receiver-operating characteristic curve analysis, the study cohort was divided into patients with a DLCO <45% of the predicted value (DLCO<45%, low DLCO; n = 52) and patients with a DLCO ≥45% of the predicted value (DLCO≥45%; n = 56). DLCO<45% was associated with male sex (odds ratio [OR]: 2.71; 95% confidence interval [CI]: 1.05 to 6.99; p = 0.039) and smoking history (OR: 5.01; 95% CI: 1.91 to 13.10; p < 0.001). There were no correlations between DLCO and other lung function parameters and hemodynamics. Compared with patients with DLCO≥45%, patients with DLCO<45% had a significantly worse outcome (survival rate at 3 years 36.5% vs. 87.8%, p < 0.001 by log-rank analysis). Cox proportional hazard analysis identified DLCO<45% as an independent predictor of death (hazard ratio: 6.6; 95% CI: 2.6 to 16.9; p < 0.001).

CONCLUSIONS

In patients with PH-HFpEF, a low DLCO is strongly associated with mortality.

Lung function in pulmonary hypertension

Breathlessness is a common symptom in pulmonary hypertension (PH) and an important cause of morbidity. Though this has been attributed to the well described pulmonary vascular abnormalities and subsequent cardiac remodelling, changes in the airways of these patients have also been reported and may contribute to symptoms. Our understanding of these airway abnormalities is poor with conflicting findings in many studies. The present review evaluates these studies for the major PH groups. In addition we describe the role of cardiopulmonary exercise testing in the assessment of pulmonary arterial hypertension (PAH) by evaluating cardiopulmonary interaction during exercise. As yet, the reasons for the abnormalities in lung function are unclear, but potential causes and the possible role of inflammation are discussed. Future research is required to provide a better understanding of this to help improve the management of these patients.

Saudi guidelines on the diagnosis and treatment of pulmonary hypertension: 2014 updates

The Saudi Association for Pulmonary Hypertension (previously called Saudi Advisory Group for Pulmonary Hypertension) has published the first Saudi Guidelines on Diagnosis and Treatment of Pulmonary Arterial Hypertension back in 2008.[1] That guideline was very detailed and extensive and reviewed most aspects of pulmonary hypertension (PH). One of the disadvantages of such detailed guidelines is the difficulty that some of the readers who just want to get a quick guidance or looking for a specific piece of information might face.

All efforts were made to develop this guideline in an easy-to-read form, making it very handy and helpful to clinicians dealing with PH patients to select the best management strategies for the typical patient suffering from a specific condition. This Guideline was designed to provide recommendations for problems frequently encountered by practicing clinicians involved in management of PH. This publication targets mainly adult and pediatric PH-treating physicians, but can also be used by other physicians interested in PH.

Pulmonary Endarterectomy

Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary hypertension (PH) remains underdiagnosed. It is imperative that all patients with PH be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary thromboendarterectomy (PTE) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications.

Impact of kidney function and urinary protein excretion on pulmonary function in Japanese patients with chronic kidney disease

BACKGROUND

Although the cardiorenal relationship in chronic kidney disease has been investigated, information about the lung-kidney relationship is limited. Here, we investigated the impact of kidney function and urinary protein excretion on pulmonary dysfunction.

METHODS

The data from pulmonary function tests and kidney function (estimated glomerular filtration rate [eGFR] and urinary protein) between 1 April 2005 and 30 June 2010 were selected from our laboratory database. Data were classified into 4 categories according to eGFR and proteinuria. Category 1, eGFR ≥60 ml/min/1.73 m(2) and urinary protein <0.3 g/gCr; category 2, eGFR <60 ml/min/1.73 m(2) and urinary protein <0.3 g/gCr; category 3, eGFR ≥60 ml/min/1.73 m(2) and urinary protein ≥0.3 g/gCr; and category 4, eGFR <60 ml/min/1.73 m(2) and urinary protein ≥0.3 g/gCr. Pulmonary function data were evaluated according to these 4 categories.

RESULTS

A total of 133 participants without major respiratory disease, abnormal computed tomography and smoking history were enrolled. Hemoglobin (Hb)-adjusted percentage carbon monoxide diffusing capacity (%DLCO) in category 4 (46.2 ± 7.5) and category 2 (63.6 ± 17.8) were significantly lower than in category 1 (75.8 ± 18.9) (P < 0.05). In addition, Hb-adjusted %DLCO was weakly correlated with eGFR in participants with urinary protein <0.3 g/gCr (R = 0.30, P = 0.001). Hb-adjusted %DLCO was strongly correlated with eGFR in participants with urinary protein ≥0.3 g/gCr (R = 0.81, P < 0.001). Other pulmonary function test markers (percentage (%) vital capacity, % forced expiratory volume in one second (FEV1), FEV1/forced vital capacity, % total lung capacity, and % residual volume) were not significantly different between categories.

CONCLUSION

This study suggests that decreased eGFR is associated with decreased %DLCO in proteinuric patients.

Chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) is a disease with high mortality and few treatment options. This article reviews the epidemiology of CTEPH and identifies risk factors for its development. The pathobiology and the progression from thromboembolic events to chronically increased right-sided pressures are discussed. The diagnosis and assessment of CTEPH requires several modalities and the role of these is detailed. The pre-operative evaluation assesses peri-operative risk and determines the likelihood of benefit from PTE. Pulmonary thromboendarterectomy (PTE) remains the treatment of choice in appropriate patients. Nonsurgical therapies for CTEPH may provide benefit in patients who cannot be offered surgery.

Diagnosis of pulmonary arterial hypertension

Accurate diagnosis of pulmonary arterial hypertension can be challenging and often requires a high index of clinical suspicion. Use of a variety of noninvasive tests can help define the population of patients in whom invasive cardiac catheterization should be pursued. An understanding of the historical, physical exam, electrocardiographic, radiographic, and echocardiographic clues in the diagnosis is important. A ventilation-perfusion scan and careful assessment for left-to-right shunting are mandatory to avoid missing reasons for pulmonary hypertension that may require nonpharmacologic management. Right heart, and sometimes concomitant left heart, catheterization is required to establish the diagnosis and distinguish pulmonary arterial from pulmonary venous hypertension.

Loss of alveolar membrane diffusing capacity and pulmonary capillary blood volume in pulmonary arterial hypertension

Background

Reduced gas transfer in patients with pulmonary arterial hypertension (PAH) is traditionally attributed to remodeling and progressive loss of pulmonary arterial vasculature that results in decreased capillary blood volume available for gas exchange.

Methods

We tested this hypothesis by determination of lung diffusing capacity (DL) and its components, the alveolar capillary membrane diffusing capacity (D_m) and lung capillary blood volume (V_c) in 28 individuals with PAH in comparison to 41 healthy individuals, and in 19 PAH patients over time. Using single breath simultaneous measure of diffusion of carbon monoxide (DL_CO) and nitric oxide (DL_NO), DL and D_m were respectively determined, and V_c calculated. D_m and V_c were evaluated over time in relation to standard clinical indicators of disease severity, including brain natriuretic peptide (BNP), 6-minute walk distance (6MWD) and right ventricular systolic pressure (RVSP) by echocardiography.

Results

Both DL_CO and DL_NO were reduced in PAH as compared to controls and the lower DL in PAH was due to loss of both D_m and V_c (all p < 0.01). While DL_CO of PAH patients did not change over time, DL_NO decreased by 24 ml/min/mmHg/year (p = 0.01). Consequently, D_m decreased and V_c tended to increase over time, which led to deterioration of the D_m/V_c ratio, a measure of alveolar-capillary membrane functional efficiency without changes in clinical markers.

Conclusions

The findings indicate that lower than normal gas transfer in PAH is due to loss of both D_m and V_c, but that deterioration of D_m/V_c over time is related to worsening membrane diffusion.

Evaluation of patients with chronic thromboembolic pulmonary hypertension for pulmonary endarterectomy

Pulmonary hypertension as a result of chronic thromboembolic disease (CTEPH) is potentially curable with pulmonary endarterectomy surgery. Consequently, correctly diagnosing patients with this type of pulmonary hypertension and evaluating these patients with the goal of establishing their candidacy for surgical intervention is of utmost importance. And as advancements in surgical techniques have allowed successful resection of segmental-level chronic thromboembolic disease, the number of CTEPH patients that are deemed suitable surgical candidates has expanded, making it even more important that the evaluation be conducted with greater precision. This article will review a diagnostic approach to patients with suspected chronic thromboembolic disease with an emphasis on the criteria considered in selecting patients for pulmonary endarterectomy surgery.

Exercise intolerance in pulmonary arterial hypertension

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

Examination of the carbon monoxide diffusing capacity (DL(CO)) in relation to its KCO and VA components

The single-breath carbon monoxide diffusing capacity (DL(CO)) is the product of two measurements during breath holding at full inflation: (1) the rate constant for carbon monoxide uptake from alveolar gas (kco [minute(-1)]) and (2) the "accessible" alveolar volume (Va). kco expressed per mm Hg alveolar dry gas pressure (Pb*) as kco/Pb*, and then multiplied by Va, equals Dl(CO); thus, Dl(CO) divided by Va (DL(CO)/Va, also called Kco) is only kco/Pb* in different units, remaining, essentially, a rate constant. The notion that DL(CO)/Va "corrects" DL(CO) for reduced Va is physiologically incorrect, because DL(CO)/Va is not constant as Va changes; thus, the term Kco reflects the physiology more appropriately. Crucially, the same DL(CO) may occur with various combinations of Kco and Va, each suggesting different pathologies. Decreased Kco occurs in alveolar-capillary damage, microvascular pathology, or anemia. Increased Kco occurs with (1) failure to expand normal lungs to predicted full inflation (extrapulmonary restriction); or (2) increased capillary volume and flow, either globally (left-to-right intracardiac shunting) or from flow and volume diversion from lost or damaged units to surviving normal units (e.g., pneumonectomy). Decreased Va occurs in (1) reduced alveolar expansion, (2) alveolar damage or loss, or (3) maldistribution of inspired gases with airflow obstruction. Kco will be greater than 120% predicted in case 1, 100-120% in case 2, and 40-120% in case 3, depending on pathology. Kco and Va values should be available to clinicians, as fundamental to understanding the clinical implications of DL(CO). The diffusing capacity for nitric oxide (DL(NO)), and the DL(NO)/DL(CO) ratio, provide additional insights.

A pulmonary hypertension gas exchange severity (PH-GXS) score to assist with the assessment and monitoring of pulmonary arterial hypertension

Submaximal exercise gas analysis may be a useful method to assess and track pulmonary arterial hypertension (PAH) severity. The aim of the present study was to develop an algorithm, using exercise gas exchange data, to assess and monitor PAH severity. Forty patients with PAH participated in the study, completing a range of clinical tests and a novel submaximal exercise step test, which lasted 6 minutes and incorporated rest (2 minutes), exercise (3 minutes), and recovery (1 minute) ventilatory gas analysis. Using gas exchange data, including breathing efficiency, end-tidal carbon dioxide, oxygen saturation, and oxygen pulse, a pulmonary hypertension gas exchange severity (PH-GXS) score was developed. Patients were retested after about 6 months. There was significant separation between healthy controls and patients with moderate PAH (World Health Organization [WHO] class I/II) and those with more severe PAH (WHO class III/IV) for breathing efficiency, end-tidal carbon dioxide, oxygen saturation, and oxygen pulse. The PH-GXS score was significantly correlated with WHO class (r = 0.51), 6-minute walking distance (r = -0.59), right ventricular systolic pressure (r = 0.49), log N-terminal pro-B-type natriuretic peptide (r = 0.54), and pulmonary vascular resistance (r = 0.71). The PH-GXS score remained unchanged in 22 patients retested (1.50 ± 0.92 vs 1.48 ± 0.94), as did WHO class (2.3 ± 0.8 vs 2.3 ± 0.8) and 6-minute walking distance (455 ± 120 vs 456 ± 103 m). Small individual changes were observed in the PH-GXS score, with 8 patients improving and 8 deteriorating. In conclusion, the PH-GXS score differentiated between patients with PAH and was correlated with traditional clinical measures. The PH-GXS score was unchanged in our cohort after 6 months, consistent with traditional clinical metrics, but individual differences were evident. A PH-GXS score may be a useful way to track patient responses to therapy.

The usefulness of submaximal exercise gas exchange to define pulmonary arterial hypertension

BACKGROUND

The 6-minute walk test is widely used to characterize activity tolerance and response to therapy in pulmonary arterial hypertension (PAH) but provides little information about cardiopulmonary pathophysiology. The aim of the present study was to determine whether measures of pulmonary gas exchange during relatively light exercise could differentiate between PAH patients and healthy individuals and also stratify disease severity.

METHODS

The study comprised 40 PAH patients and 25 matched controls. Each completed a sub-maximal exercise test, consisting of 2 minutes of rest, 3 minutes of exercise, and 1 minute of recovery. Ventilation, pulmonary gas exchange, arterial oxygen saturation (Sao(2)), and heart rate were measured throughout using a simplified gas analysis system.

RESULTS

A number of gas exchange variables differentiated PAH patients and controls. End-tidal CO(2) (P(ET)co(2)) and Sao(2) were lower in PAH vs controls (31 ± 7 vs 39 ± 3 mm Hg and 89% ± 5% vs 95% ± 2%, respectively, p < 0.05). Breathing efficiency (V(E)/Vco(2) ratio) was poorer in PAH vs controls (42 ± 10 vs 33 ± 5, p < 0.05). In addition, P(ET)co(2) and V(E)/Vco(2) discriminated between different severities of PAH.

CONCLUSIONS

Gas exchange variables obtained during light sub-maximal exercise differentiated PAH patients from healthy controls and also between different severities of PAH. Sub-maximal exercise gas exchange may be a useful end point measure in a PAH population.

Reduction in membrane component of diffusing capacity is associated with the extent of acute pulmonary embolism

Acute pulmonary embolism (PE) often decreases pulmonary diffusing capacity for carbon monoxide (DL,CO), but data on the mechanisms involved are inconsistent. We wanted to investigate whether reduction in diffusing capacity of alveolo-capillary membrane (DM) and pulmonary capillary blood volume (Vc) is associated with the extent of PE or the presence and severity of right ventricular dysfunction (RVD) induced by PE and how the possible changes are corrected after 7-month follow-up. Forty-seven patients with acute non-massive PE in spiral computed tomography (CT) were included. The extent of PE was assessed by scoring mass of embolism. DL,CO, Vc, DM and alveolar volume (VA) were measured by using a single breath method with carbon monoxide and oxygen both at the acute phase and 7 months later. RVD was evaluated with transthoracic echocardiography and electrocardiogram. Fifteen healthy subjects were included as controls. DL,CO, DL, CO/VA, DM, vital capacity (VC) and VA were significantly lower in the patients with acute PE than in healthy controls (P < 0.001). DM/Vc relation was significantly lower in patients with RVD than in healthy controls (P = 0.004). DM correlated inversely with central mass of embolism (r = -0.312; P = 0.047) whereas Vc did not. DM, DL,CO, VC and VA improved significantly within 7 months. In all patients (P = 0.001, P = 0.001) and persistent RVD (P = 0.020, P = 0.012), DM and DL,CO remained significantly lower than in healthy controls in the follow-up. DM was inversely related to central mass of embolism. Reduction in DM mainly explains the sustained decrease in DL,CO in PE after 7 months despite modern treatment of PE.

Pulmonary hypertension after ventriculoatrial shunt implantation

Object

Ventriculoatrial (VA) shunts inserted for the treatment of hydrocephalus are known to be a risk factor for pulmonary hypertension. The aim of this study was to evaluate the incidence of pulmonary hypertension among adult patients with VA shunts.

Methods

All patients who had received a VA shunt at one of two institutions between 1985 and 2000 were invited for a cardiopulmonary evaluation. The investigation included a thorough history taking, clinical examination, echocardiography, and pulmonary function testing including diffusing capacity of the lung for carbon monoxide (DLCO). Pulmonary hypertension was defined as systolic pulmonary artery pressure > 35 mm Hg at rest.

Results

The study group consisted of 86 patients, of whom 38 (44%) could be examined. The patients' mean age was 47.1 ± 18.4 years; the median interval between shunt insertion and cardiopulmonary evaluation was 15 years (range 5–20 years). Of the 38 patients, 20 (53%) had Doppler velocity profiles of tricuspid regurgitation that were adequate for the estimation of pulmonary artery systolic pressure. Doppler-defined pulmonary hypertension was observed in 3 patients (8%), 2 of whom underwent right heart catheterization. Chronic thromboembolic pulmonary hypertension was confirmed in both patients, and medical therapy, including anticoagulation, was started. The VA shunt was removed in both cases and replaced with a different type of device. Pulmonary function tests revealed a restrictive pattern in 15% and typical obstructive findings in 9% of patients. In 30% of patients the DLCO was less than 80% of predicted, and blood gas analysis showed hypoxemia in 6% of patients. No significant differences in pulmonary function tests were noted between the patients with and without echocardiographic evidence of pulmonary hypertension. However, patients with pulmonary hypertension had significantly lower DLCO values.

Conclusions

The authors detected pulmonary hypertension by using Doppler echocardiography in a significant proportion of patients with VA shunts. It is therefore recommended that practitioners perform regular echocardiography and pulmonary function tests, including single-breath DLCO in these patients to screen for pulmonary hypertension to prevent hazardous late cardiopulmonary complications.

Does reduced lung diffusing capacity for carbon monoxide predict the presence of pulmonary hypertension?

OBJECTIVE

The objective of this study was to determine whether reduced lung diffusing capacity for carbon monoxide (DLCO) predicts the presence of pulmonary hypertension (PH) in heterogeneous group of patients.

METHODS

Consecutive patients who underwent pulmonary function and transthoracic echocardiographic testing within a 6-month period were retrospectively identified by chart review. Right ventricular systolic pressure (RVSP) was measured using Doppler echocardiography. PH was defined as a RVSP >30 mm Hg. Patients were divided into 2 major groups: those whose RVSP was < or =30 mm Hg and those whose RVSP was >30 mm Hg. PH was classified as mild (RVSP = 31-40 mm Hg), moderate (RSVP = 41-60 mm Hg) and severe (RVSP >60 mm Hg).

RESULTS

A total of 398 patients were entered into the study: 264 (66.3%) with PH and 134 (33.7%) without PH. Patients with PH were older, had a lower mean percentage of predicted values for forced vital capacity (%FVC), for DLCO (%DLCO) and for DLCO corrected for alveolar volume (%DLCO/VA) than those without PH. Multivariate analysis identified age and %FVC as independent predictors of PH [odds ratios and 95% confidence intervals of 1.038 (1.020-1.056) and 0.972 (0.955-0.988), respectively]. There was a weak, but significant negative correlation between RVSP and %DLCO (r = -0.205, P = 0.001), but there was no correlation between RVSP and %DLCO/VA. Neither %DLCO nor %DLCO/VA was found to be independent predictors of PH.

CONCLUSION

In a heterogeneous group of patients, %DLCO and %DLCO/VA do not independently predict the presence of PH.

Membrane diffusion- and capillary blood volume measurements are not useful as screening tools for pulmonary arterial hypertension in systemic sclerosis: a case control study

BACKGROUND

There is no optimal screening tool for the assessment of pulmonary arterial hypertension (PAH) in patients with systemic sclerosis (SSc). A decreasing transfer factor of the lung for CO (TLCO) is associated with the development of PAH in SSc. TLCO can be partitioned into the diffusion of the alveolar capillary membrane (Dm) and the capillary blood volume (Vc). The use of the partitioned diffusion to detect PAH in SSc is not well established yet. This study evaluates whether Dm and Vc could be candidates for further study of the use for screening for PAH in SSc.

METHODS

Eleven SSc patients with PAH (SScPAH+), 13 SSc patients without PAH (SScPAH-) and 10 healthy control subjects were included. Pulmonary function testing took place at diagnosis of PAH. TLCO was partitioned according to Roughton and Forster. As pulmonary fibrosis in SSc influences values of the (partitioned) TLCO, these were adjusted for fibrosis score as assessed on HRCT.

RESULTS

TLCO as percentage of predicted (%) was lower in SScPAH+ than in SScPAH- (41 +/- 7% vs. 63 +/- 12%, p < 0.0001, respectively). Dm% in SScPAH+ was decreased as compared with SScPAH- (22 +/- 6% vs. 39 +/- 12%, p < 0.0001, respectively), also after adjustment for total fibrosis score (before adjustment: B = 17.5, 95% CI 9.0-25.9, p = < 0.0001; after adjustment: B = 14.3, 95% CI 6.0-21.7, p = 0.008). No difference was found in Vc%. There were no correlations between pulmonary hemodynamic parameters and Dm% in the PAH groups.

CONCLUSION

SScPAH+ patients have lower Dm% than SScPAH- patients. There are no correlations between Dm% and hemodynamic parameters of PAH in SScPAH+. These findings do not support further study of the role of partitioning TLCO in the diagnostic work- up for PAH in SSc.

Pulmonary capillary endothelial metabolic function in chronic thromboembolic pulmonary hypertension

BACKGROUND

Chronic thromboembolic pulmonary hypertension (CTEPH) causes physical plugging of large pulmonary arteries as well as a distal micro-vasculopathy. Pulmonary endothelium is an active metabolic tissue in normal humans. The effects of CTEPH on pulmonary endothelial metabolism are unknown.

OBJECTIVES

We studied pulmonary capillary endothelium-bound angiotensin converting enzyme (ACE) activity as an index of endothelial metabolism in patients with CTEPH.

PATIENTS/METHODS

We measured single-pass transpulmonary per cent metabolism (%M) and hydrolysis of an ACE synthetic substrate and calculated functional capillary surface area (FCSA), normalized to body surface area (BSA), in 13 patients with CTEPH and 23 controls.

RESULTS

Mean %M for CTEPH (71.6 +/- 4.0% SE) was similar to controls (74.7 +/- 2.7%). Substrate hydrolysis (v) was similar for CTEPH (1.47 +/- 0.22) and controls (1.51 +/- 0.11). However, FCSA/BSA was reduced (P < 0.01) for CTEPH (1530 +/- 218 mL min(-1)*m(-2)) as compared with controls (2948 +/- 245).

CONCLUSIONS

The metabolically functional pulmonary capillary bed is reduced in CTEPH. However, because %M and hydrolysis are preserved, this points to a reduction in functional capillary surface area rather than reduced ACE activity on the pulmonary capillary endothelial cell. The reduction in functional capillary surface area may just be a result of decreased capillary recruitment because of upstream vascular plugging by chronic organized thrombus.