Implications of Mean Pulmonary Arterial Wedge Pressure Trajectories in Pulmonary Arterial Hypertension

Rationale: The mean pulmonary arterial wedge pressure (mPAWP) is the critical hemodynamic factor differentiating group 1 pulmonary arterial hypertension (PAH) from group 2 pulmonary hypertension associated with left heart disease. Despite the discrepancy between the mPAWP upper physiologic normal and current PAH definitions, the implications of the initial mPAWP for PAH clinical trajectory are poorly understood. Objectives: To model longitudinal mPAWP trajectories in PAH over 10 years and examine the clinical and hemodynamic factors associated with trajectory membership. Methods: Adult patients with PAH with two or more right heart catheterizations were identified from a multiinstitution healthcare system in eastern Massachusetts. mPAWP trajectories were constructed via group-based trajectory modeling. Feature selection was performed in least absolute shrinkage and selection operator regression. Logistic regression was used to assess associations between trajectory membership, baseline characteristics, and transplant-free survival. Measurements and Main Results: Among 301 patients with PAH, there were two distinct mPAWP trajectories, termed "mPAWP-high" (n = 71; 23.6%) and "mPAWP-low" (n = 230; 76.4%), based on the ultimate mPAWP value. Initial mPAWP clustered around median 12 mm Hg (interquartile range [IQR], 8-14 mm Hg) in the mPAWP-high and 9 mm Hg (IQR, 6-11 mm Hg) in the mPAWP-low trajectories (P < 0.001). After feature selection, initial mPAWP ⩾12 mm Hg predicted an mPAWP-high trajectory (odds ratio, 3.2; 95% confidence interval, 1.4-6.1; P = 0.0006). An mPAWP-high trajectory was associated with shorter transplant-free survival (vs. mPAWP-low, median, 7.8 vs. 11.3 yr; log-rank P = 0.017; age-adjusted P = 0.217). Conclusions: Over 10 years, the mPAWP followed two distinct trajectories, with 25% evolving into group 2 pulmonary hypertension physiology. Using routine baseline data, longitudinal mPAWP trajectory could be predicted accurately, with initial mPAWP ⩾12 mm Hg as one of the strongest predictors.

Is pulmonary arterial hypertension associated with schistosomiasis distinct from pulmonary arterial hypertension associated with portal hypertension?

Pulmonary arterial hypertension associated with schistosomiasis (SchPAH) and pulmonary arterial hypertension associated with portal hypertension (PoPAH) are lung diseases that develop in the presence of liver diseases. However, mechanistic pathways by which the underlying liver conditions and other drivers contribute to the development and progression of pulmonary arterial hypertension (PAH) are unclear for both etiologies. In turn, these unknowns limit certainty of strategies to prevent, diagnose, and reverse the resultant PAH. Here we consider specific mechanisms that contribute to SchPAH and PoPAH, identifying those that may be shared and those that appear to be unique to each etiology, in the hope that this exploration will both highlight known causal drivers and identify knowledge gaps appropriate for future research. Overall, the key pathophysiologic differences that we identify between SchPAH and PoPAH suggest that they are not variants of a single condition.

CT imaging determinants of persistent hypoxemia in acute intermediate-risk pulmonary embolism

The factors associated with persistent hypoxemia after pulmonary embolus (PE) are not well understood. Predicting the need for oxygen post discharge at the time of diagnosis using available CT imaging will enable better discharge planning. To examine the relationship between CT derived imaging markers (automated computation of arterial small vessel fraction, pulmonary artery diameter to aortic diameter ratio (PA:A), right to left ventricular diameter ratio (RV:LV) and new oxygen requirement at the time of discharge in patients diagnosed with acute intermediate-risk PE. CT measurements were obtained in a retrospective cohort of patients with acute-intermediate risk PE admitted to Brigham and Women's Hospital between 2009 and 2017. Twenty one patients without a history of lung disease requiring home oxygen and 682 patients without discharge oxygen requirements were identified. There was an increased median PA:A ratio (0.98 vs. 0.92, p = 0.02) and arterial small vessel fraction (0.32 vs. 0.39, p = 0.001) in the oxygen-requiring group], but no difference in the median RV:LV ratio (1.20 vs. 1.20, p = 0.74). Being in the upper quantile for the arterial small vessel fraction was associated with decreased odds of oxygen requirement (OR 0.30 [0.10-0.78], p = 0.02). Loss of arterial small vessel volume as measured by arterial small vessel fraction and an increase in the PA:A ratio at the time of diagnosis were associated with the presence of persistent hypoxemia on discharge in acute intermediate-risk PE.

Quantitative Interstitial Abnormality Progression and Outcomes in the Genetic Epidemiology of COPD and Pittsburgh Lung Screening Study Cohorts

BACKGROUND

The risk factors and clinical outcomes of quantitative interstitial abnormality progression over time have not been characterized.

RESEARCH QUESTIONS

What are the associations of quantitative interstitial abnormality progression with lung function, exercise capacity, and mortality? What are the demographic and genetic risk factors for quantitative interstitial abnormality progression?

STUDY DESIGN AND METHODS

Quantitative interstitial abnormality progression between visits 1 and 2 was assessed from 4,635 participants in the Genetic Epidemiology of COPD (COPDGene) cohort and 1,307 participants in the Pittsburgh Lung Screening Study (PLuSS) cohort. We used multivariable linear regression to determine the risk factors for progression and the longitudinal associations between progression and FVC and 6-min walk distance, and Cox regression models for the association with mortality.

RESULTS

Age at enrollment, female sex, current smoking status, and the MUC5B minor allele were associated with quantitative interstitial abnormality progression. Each percent annual increase in quantitative interstitial abnormalities was associated with annual declines in FVC (COPDGene: 8.5 mL/y; 95% CI, 4.7-12.4 mL/y; P < .001; PLuSS: 9.5 mL/y; 95% CI, 3.7-15.4 mL/y; P = .001) and 6-min walk distance, and increased mortality (COPDGene: hazard ratio, 1.69; 95% CI, 1.34-2.12; P < .001; PLuSS: hazard ratio, 1.28; 95% CI, 1.10-1.49; P = .001).

INTERPRETATION

The objective, longitudinal measurement of quantitative interstitial abnormalities may help identify people at greatest risk for adverse events and most likely to benefit from early intervention.

Pulmonary arterial pruning is associated with CT-derived bronchiectasis progression in smokers

Loss of small pulmonary arteries measured as the ratio of blood vessel volume in arteries <5 mm2 in cross-section to total arterial blood vessel volume (BV5a/TBVa), with lower values indicating more pruning, was associated with 5-yr progressing CT-derived bronchiectasis in smokers (Odds Ratio (OR) [95% Confidence interval], 1.28 [1.07-1.53] per 5% lower BV5a/TBVa, P = 0.007). Corresponding results in smokers with COPD were: OR 1.45 [1.11-1.89] per 5% lower BV5a/TBVa, P = 0.007. The results support a vascular factor for structural progression of bronchiectasis.

The association of lung function and pulmonary vasculature volume with cardiorespiratory fitness in the community

INTRODUCTION

Cardiorespiratory fitness is not limited by pulmonary mechanical reasons in the majority of adults. However, the degree to which lung function contributes to exercise response patterns among ostensibly healthy individuals remains unclear.

METHODS

We examined 2314 Framingham Heart Study participants who underwent cardiopulmonary exercise testing (CPET) and pulmonary function testing. We investigated the association of FEV₁, FVC, FEV₁/FVC and DLCO with the primary outcome of peak VO₂, along with other CPET parameters using multivariable linear regression. Finally, we investigated the association of total and peripheral pulmonary blood vessel volume with peak VO₂.

RESULTS

We found lower FEV₁, FVC and DLCO were associated with lower peak VO₂. For example, a one-liter lower FEV₁ and FVC were associated with 7.1% (95% CI: 5.1%, 9.1%) and 6.0% (95% CI: 4.3%, 7.7%) lower peak VO₂, respectively_. By contrast, FEV₁/FVC ratio was not associated with peak VO₂. Lower lung function was associated with lower oxygen uptake efficiency slope oxygen pulse slope, VO₂ at AT, V_E at AT and breathing reserve. In addition, lower total and peripheral pulmonary blood vessel volume were associated with a lower peak VO₂.

CONCLUSION

In a large, community-based cohort of adults, we found lower FEV₁, FVC and DLCO were associated with lower exercise capacity, as well as oxygen uptake efficiency slope and ventilatory efficiency. In addition, lower total and peripheral pulmonary blood vessel volume were associated with lower peak VO₂. These findings underscore the importance of lung function and blood vessel volume as contributors to overall exercise capacity.

Vascular remodeling of the small pulmonary arteries and measures of vascular pruning on computed tomography

Pulmonary hypertension is characterized histologically by intimal and medial thickening in the small pulmonary arteries, eventually resulting in vascular “pruning.” Computed tomography (CT)-based quantification of pruning is associated with clinical measures of pulmonary hypertension, but it is not established whether CT-based pruning correlates with histologic arterial remodeling. Our sample consisted of 138 patients who underwent resection for early-stage lung adenocarcinoma. From histologic sections, we identified small pulmonary arteries and measured the relative area comprising the intima and media (VWA%), with higher VWA% representing greater histologic remodeling. From pre-operative CTs, we used image analysis algorithms to calculate the small vessel volume fraction (BV5/TBV) as a CT-based indicator of pruning (lower BV5/TBV represents greater pruning). We investigated relationships of CT pruning and histologic remodeling using Pearson correlation, simple linear regression, and multivariable regression with adjustment for age, sex, height, weight, smoking status, and total pack-years. We also tested for effect modification by sex and smoking status. In primary models, more severe CT pruning was associated with greater histologic remodeling. The Pearson correlation coefficient between BV5/TBV and VWA% was –0.41, and in linear regression models, VWA% was 3.13% higher (95% CI: 1.95–4.31%, p < 0.0001) per standard deviation lower BV5/TBV. This association persisted after multivariable adjustment. We found no evidence that these relationships differed by sex or smoking status. Among individuals who underwent resection for lung adenocarcinoma, more severe CT-based vascular pruning was associated with greater histologic arterial remodeling. These findings suggest CT imaging may be a non-invasive indicator of pulmonary vascular pathology.

Hypercoagulation in COPD: the clot thickens

There is a growing body of evidence that hypercoagulability is present in stable COPD, involves changes in multiple coagulation factors, and is not simply associated with major causes of inflammation and thrombosis https://bit.ly/3F5NnfN.

Loss of Pulmonary Vascular Volume as a Predictor of Right Ventricular Dysfunction and Mortality in Acute Pulmonary Embolism

BACKGROUND

In acute pulmonary embolism, chest computed tomography angiography derived metrics, such as the right ventricle (RV): left ventricle ratio are routinely used for risk stratification. Paucity of intraparenchymal blood vessels has previously been described, but their association with clinical biomarkers and outcomes has not been studied. We sought to determine if small vascular volumes measured on computed tomography scans were associated with an abnormal RV on echocardiography and mortality. We hypothesized that decreased small venous volume would be associated with greater RV dysfunction and increased mortality.

METHODS

A retrospective cohort of patients with intermediate risk pulmonary embolism admitted to Brigham and Women's Hospital between 2009 and 2017 was assembled, and clinical and radiographic data were obtained. We performed 3-dimensional reconstructions of vasculature to assess intraparenchymal vascular volumes. Statistical analyses were performed using multivariable regression and cox proportional hazards models, adjusting for age, sex, lung volume, and small arterial volume.

RESULTS

Seven hundred twenty-two subjects were identified of whom 573 had documented echocardiography. A 50% reduction in small venous volume was associated with an increased risk of RV dilation (relative risk: 1.38 [95% CI, 1.18-1.63], P<0.001), RV dysfunction (relative risk: 1.62 [95% CI, 1.36-1.95], P<0.001), and RV strain (relative risk: 1.67 [95% CI, 1.37-2.04], P<0.001); increased cardiac biomarkers, and higher 30-day and 90-day mortality (hazard ratio: 2.50 [95% CI, 1.33-4.67], P=0.004 and hazard ratio: 1.84 [95% CI, 1.11-3.04], P=0.019, respectively).

CONCLUSIONS

Loss of small venous volume quantified from computed tomography angiography is associated with increased risk of abnormal RV on echocardiography, abnormal cardiac biomarkers, and higher risk of 30- and 90-day mortality. Small venous volume may be a useful marker for assessing disease severity in acute pulmonary embolism.

Pulmonary Arterial Pruning and Longitudinal Change in Percent Emphysema and Lung Function: The Genetic Epidemiology of COPD Study

BACKGROUND

Pulmonary endothelial damage has been shown to precede the development of emphysema in animals, and vascular changes in humans have been observed in COPD and emphysema.

RESEARCH QUESTION

Is intraparenchymal vascular pruning associated with longitudinal progression of emphysema on CT imaging or decline in lung function over 5 years?

STUDY DESIGN AND METHODS

The Genetic Epidemiology of COPD Study enrolled ever smokers with and without COPD from 2008 through 2011. The percentage of emphysema-like lung, or "percent emphysema," was assessed at baseline and after 5 years on noncontrast CT imaging as the percentage of lung voxels < -950 Hounsfield units. An automated CT imaging-based tool assessed and classified intrapulmonary arteries and veins. Spirometry measures are postbronchodilator. Pulmonary arterial pruning was defined as a lower ratio of small artery volume (< 5 mm2 cross-sectional area) to total lung artery volume. Mixed linear models included demographics, anthropomorphics, smoking, and COPD, with emphysema models also adjusting for CT imaging scanner and lung function models adjusting for clinical center and baseline percent emphysema.

RESULTS

At baseline, the 4,227 participants were 60 ± 9 years of age, 50% were women, 28% were Black, 47% were current smokers, and 41% had COPD. Median percent emphysema was 2.1 (interquartile range, 0.6-6.3) and progressed 0.24 percentage points/y (95% CI, 0.22-0.26 percentage points/y) over 5.6 years. Mean FEV1 to FVC ratio was 68.5 ± 14.2% and declined 0.26%/y (95% CI, -0.30 to -0.23%/y). Greater pulmonary arterial pruning was associated with more rapid progression of percent emphysema (0.11 percentage points/y per 1-SD increase in arterial pruning; 95% CI, 0.09-0.16 percentage points/y), including after adjusting for baseline percent emphysema and FEV1. Arterial pruning also was associated with a faster decline in FEV1 to FVC ratio (-0.04%/y per 1-SD increase in arterial pruning; 95% CI, -0.008 to -0.001%/y).

INTERPRETATION

Pulmonary arterial pruning was associated with faster progression of percent emphysema and more rapid decline in FEV1 to FVC ratio over 5 years in ever smokers, suggesting that pulmonary vascular differences may be relevant in disease progression.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00608764; URL: www.clinicaltrials.gov.

Quantification of Arterial and Venous Morphological Markers in Pulmonary Arterial Hypertension Using Computed Tomography

Background

Pulmonary hypertension is a heterogeneous disease, and a significant portion of patients at risk for it have CT imaging available. Advanced automated processing techniques could be leveraged for early detection, screening, and development of quantitative phenotypes. Pruning and vascular tortuosity have been previously described in pulmonary arterial hypertension (PAH), but the extent of these phenomena in arterial vs venous pulmonary vasculature and in exercise pulmonary hypertension (ePH) have not been described.

Research Question

What are the arterial and venous manifestations of pruning and vascular tortuosity using CT imaging in PAH, and do they also occur in ePH?

Study Design and Methods

A cohort of patients with PAH and ePH and control subjects with available CT angiograms were retrospectively identified to examine the differential arterial and venous presence of pruning and tortuosity in patients with precapillary pulmonary hypertension not confounded by lung or thromboembolic disease. The pulmonary vasculature was reconstructed, and an artificial intelligence method was used to separate arteries and veins and to compute arterial and venous vascular volumes and tortuosity.

Results

A total of 42 patients with PAH, 12 patients with ePH, and 37 control subjects were identified. There was relatively lower (median [interquartile range]) arterial small vessel volume in subjects with PAH (PAH 14.7 [11.7-16.5; P < .0001]) vs control subjects (16.9 [15.6-19.2]) and venous small vessel volume in subjects with PAH and ePH (PAH 8.0 [6.5-9.6; P < .0001]; ePH, 7.8 [7.5-11.4; P = .004]) vs control subjects (11.5 [10.6-12.2]). Higher large arterial volume, however, was only observed in the pulmonary arteries (PAH 17.1 [13.6-23.4; P < .0001] vs control subjects 11.4 [8.1-15.4]). Similarly, tortuosity was higher in the pulmonary arteries in the PAH group (PAH 3.5 [3.3-3.6; P = .0002] vs control 3.2 [3.2-3.3]).

Interpretation

Lower small distal pulmonary vascular volume, higher proximal arterial volume, and higher arterial tortuosity were observed in PAH. These can be quantified by using automated techniques from clinically acquired CT scans of patients with ePH and resting PAH.

What's new in pulmonary hypertension clinical research: lessons from the best abstracts at the 2020 American Thoracic Society International Conference

In this conference paper, we review the 2020 American Thoracic Society International Conference session titled, "What's New in Pulmonary Hypertension Clinical Research: Lessons from the Best Abstracts". This virtual mini-symposium took place on 21 October 2020, in lieu of the annual in-person ATS International Conference which was cancelled due to the COVID-19 pandemic. Seven clinical research abstracts were selected for presentation in the session, which encompassed five major themes: (1) standardizing diagnosis and management of pulmonary hypertension, (2) improving risk assessment in pulmonary arterial hypertension, (3) evaluating biomarkers of disease activity, (4) understanding metabolic dysregulation across the spectrum of pulmonary hypertension, and (5) advancing knowledge in chronic thromboembolic pulmonary hypertension. Focusing on these five thematic contexts, we review the current state of knowledge, summarize presented research abstracts, appraise their significance and limitations, and then discuss relevant future directions in pulmonary hypertension clinical research.

Relationship between Emphysema Progression at CT and Mortality in Ever-Smokers: Results from the COPDGene and ECLIPSE Cohorts

Background The relationship between emphysema progression and long-term outcomes is unclear. Purpose To determine the relationship between emphysema progression at CT and mortality among participants with emphysema. Materials and Methods In a secondary analysis of two prospective observational studies, COPDGene (clinicaltrials.gov, NCT00608764) and Evaluation of Chronic Obstructive Pulmonary Disease Longitudinally to Identify Predictive Surrogate End-points (ECLIPSE; clinicaltrials.gov, NCT00292552), emphysema was measured at CT at two points by using the volume-adjusted lung density at the 15th percentile of the lung density histogram (hereafter, lung density perc15) method. The association between emphysema progression rate and all-cause mortality was analyzed by using Cox regression adjusted for ethnicity, sex, baseline age, pack-years, and lung density, baseline and change in smoking status, forced expiratory volume in 1 second, and 6-minute walk distance. In COPDGene, respiratory mortality was analyzed by using the Fine and Gray method. Results A total of 5143 participants (2613 men [51%]; mean age, 60 years ± 9 [standard deviation]) in COPDGene and 1549 participants (973 men [63%]; mean age, 62 years ± 8) in ECLIPSE were evaluated, of which 2097 (40.8%) and 1179 (76.1%) had emphysema, respectively. Baseline imaging was performed between January 2008 and December 2010 for COPDGene and January 2006 and August 2007 for ECLIPSE. Follow-up imaging was performed after 5.5 years ± 0.6 in COPDGene and 3.0 years ± 0.2 in ECLIPSE, and mortality was assessed over the ensuing 5 years in both. For every 1 g/L per year faster rate of decline in lung density perc15, all-cause mortality increased by 8% in COPDGene (hazard ratio [HR], 1.08; 95% CI: 1.01, 1.16; P = .03) and 6% in ECLIPSE (HR, 1.06; 95% CI: 1.00, 1.13; P = .045). In COPDGene, respiratory mortality increased by 22% (HR, 1.22; 95% CI: 1.13, 1.31; P < .001) for the same increase in the rate of change in lung density perc15. Conclusion In ever-smokers with emphysema, emphysema progression at CT was associated with increased all-cause and respiratory mortality. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Lee and Park in this issue.

Cost-effectiveness microsimulation of catheter-directed thrombolysis in submassive pulmonary embolism using a right ventricular function model

Approximately 30-50% of hemodynamically stable patients presenting with acute pulmonary embolism (PE) have evidence of right ventricular (RV) dysfunction. These patients are classified as submassive PE and the role of reperfusion therapy remains unclear. We sought to identify the circumstances under which catheter-directed thrombolysis (CDT) would represent high-value care for submassive PE. We used a computer-based, individual-level, state-transition model with one million simulated patients to perform a cost-effectiveness analysis comparing the treatment of submassive PE with CDT followed by anticoagulation to treatment with anticoagulation alone. Because RV function impacts prognosis and is commonly used in PE outcomes research, our model used RV dysfunction to differentiate health states. One-way, two-way, and probabilistic sensitivity analyses were used to quantify model uncertainty. Our base case analysis generated an incremental cost-effectiveness ratio (ICER) of $119,326 per quality adjusted life year. Sensitivity analyses resulted in ICERs consistent with high-value care when CDT conferred a reduction in the absolute probability of RV dysfunction of 3.5% or more. CDT yielded low-value ICERs if the absolute reduction was less than 1.56%. Our model suggests that catheter-directed thrombolytics represents high-value care compared to anticoagulation alone when CDT offers an absolute improvement in RV dysfunction of 3.5% or more, but there is substantial uncertainly around these results. We estimated the monetary value of clarifying the costs and consequences surrounding RV dysfunction after submassive PE to be approximately $268 million annually, suggesting further research in this area could be highly valuable.

Advanced Imaging in Pulmonary Vascular Disease

Although the diagnosis of pulmonary hypertension requires invasive testing, imaging serves an important role in the screening, classification, and monitoring of patients with pulmonary vascular disease (PVD). The development of advanced imaging techniques has led to improvements in the understanding of disease pathophysiology, noninvasive assessment of hemodynamics, and stratification of patient risk. This article discusses the current role of advanced imaging and the emerging novel techniques for visualizing the lung parenchyma, mediastinum, and heart in PVD.

Smaller Left Ventricle Size at Noncontrast CT Is Associated with Lower Mortality in COPDGene Participants

Background Smokers with chronic obstructive pulmonary disease (COPD) have smaller left ventricles (LVs) due to reduced preload. Skeletal muscle wasting is also common in COPD, but less is known about its contribution to LV size. Purpose To explore the relationships between CT metrics of emphysema, venous vascular volume, and sarcopenia with the LV epicardial volume (LV_EV) (myocardium and chamber) estimated from chest CT images in participants with COPD and then to determine the clinical relevance of the LV_EV in multivariable models, including sex and anthropomorphic metrics. Materials and Methods The COPDGene study (ClinicalTrials.gov identifier: NCT00608764) is an ongoing prospective longitudinal observational investigation that began in 2006. LV_EV, distal pulmonary venous blood volume for vessels smaller than 5 mm² in cross section (BV5), CT emphysema, and pectoralis muscle area were retrospectively extracted from 3318 nongated, unenhanced COPDGene CT scans. Multivariable linear and Cox regression models were used to explore the association between emphysema, venous BV5, pectoralis muscle area, and LV_EV as well as the association of LV_EV with health status using the St George's Respiratory Questionnaire, 6-minute walk distance, and all-cause mortality. Results The median age of the cohort was 64 years (interquartile range, 57-70 years). Of the 2423 participants, 1806 were men and 617 were African American. The median LV_EV between Global Initiative for Chronic Obstructive Lung Disease (GOLD) 1 and GOLD 4 COPD was reduced by 13.9% in women and 17.7% in men (P < .001 for both). In fully adjusted models, higher emphysema percentage (β = -4.2; 95% confidence interval [CI]: -5.0, -3.4; P < .001), venous BV5 (β = 7.0; 95% CI: 5.7, 8.2; P < .001), and pectoralis muscle area (β = 2.7; 95% CI: 1.2, 4.1; P < .001) were independently associated with reduced LV_EV. Reductions in LV_EV were associated with improved health status (β = 0.3; 95% CI: 0.1, 0.4) and 6-minute walk distance (β = -12.2; 95% CI: -15.2, -9.3). These effects were greater in women than in men. The effect of reduced LV_EV on mortality (hazard ratio: 1.07; 95% CI: 1.05, 1.09) did not vary by sex. Conclusion In women more than men with chronic obstructive pulmonary disease, a reduction in the estimated left ventricle epicardial volume correlated with a loss of pulmonary venous vasculature, greater pectoralis muscle sarcopenia, and lower all-cause mortality. © RSNA, 2020 Online supplemental material is available for this article.

Estimated Ventricular Size, Asthma Severity, and Exacerbations: The Severe Asthma Research Program III Cohort

BACKGROUND

Relative enlargement of the pulmonary artery (PA) on chest CT imaging is associated with respiratory exacerbations in patients with COPD or cystic fibrosis. We sought to determine whether similar findings were present in patients with asthma and whether these findings were explained by differences in ventricular size.

METHODS

We measured the PA and aorta diameters in 233 individuals from the Severe Asthma Research Program III cohort. We also estimated right, left, and total epicardial cardiac ventricular volume indices (eERVVI, eELVVI, and eETVVI, respectively). Associations between the cardiac and PA measures (PA-to-aorta [PA/A] ratio, eERVVI-to-eELVVI [eRV/eLV] ratio, eERVVI, eELVVI, eETVVI) and clinical measures of asthma severity were assessed by Pearson correlation, and associations with asthma severity and exacerbation rate were evaluated by multivariable linear and zero-inflated negative binomial regression.

RESULTS

Asthma severity was associated with smaller ventricular volumes. For example, those with severe asthma had 36.1 mL/m² smaller eETVVI than healthy control subjects (P = .003) and 14.1 mL/m² smaller eETVVI than those with mild/moderate disease (P = .011). Smaller ventricular volumes were also associated with a higher rate of asthma exacerbations, both retrospectively and prospectively. For example, those with an eETVVI less than the median had a 57% higher rate of exacerbations during follow-up than those with eETVVI greater than the median (P = .020). Neither PA/A nor eRV/eLV was associated with asthma severity or exacerbations.

CONCLUSIONS

In patients with asthma, smaller cardiac ventricular size may be associated with more severe disease and a higher rate of asthma exacerbations.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01761630; URL: www.clinicaltrials.gov.

Equipoise in Appropriate Initial Volume Resuscitation for Patients in Septic Shock With Heart Failure: Results of a Multicenter Clinician Survey

PURPOSE

International clinical practice guidelines call for initial volume resuscitation of at least 30 mL/kg body weight for patients with sepsis-induced hypotension or shock. Although not considered in the guidelines, preexisting cardiac dysfunction may be an important factor clinicians weigh in deciding the quantity of volume resuscitation for patients with septic shock.

METHODS

We conducted a multicenter survey of clinicians who routinely treat patients with sepsis to evaluate their beliefs, behaviors, knowledge, and perceived structural barriers regarding initial volume resuscitation for patients with sepsis and concomitant heart failure with reduced ejection fraction (HFrEF) <40%. Initial volume resuscitation preferences were captured as ordinal values, and additional testing for volume resuscitation preferences was performed using McNemar and Wilcoxon signed rank tests as indicated. Univariable logistic regression models were used to identify significant predictors of ≥30 mL/kg fluid administration.

RESULTS

A total of 317 clinicians at 9 US hospitals completed the survey (response rate 47.3%). Most respondents were specialists in either internal medicine or emergency medicine. Substantial heterogeneity was found regarding sepsis resuscitation preferences for patients with concomitant HFrEF. The belief that patients with septic shock and HFrEF should be exempt from current sepsis bundle initiatives was shared by 39.4% of respondents. A minimum fluid challenge of ∼30 mL/kg or more was deemed appropriate in septic shock by only 56.4% of respondents for patients with concomitant HFrEF, compared to 89.1% of respondents for patients without HFrEF (P < .01). Emergency medicine physicians were most likely to feel that <30 mL/kg was most appropriate in patients with septic shock and HFrEF.

CONCLUSIONS

Clinical equipoise exists regarding initial volume resuscitation for patients with sepsis-induced hypotension or shock and concomitant HFrEF. Future studies and clinical practice guidelines should explicitly address resuscitation in this subpopulation.

Arterial Vascular Pruning, Right Ventricular Size, and Clinical Outcomes in Chronic Obstructive Pulmonary Disease. A Longitudinal Observational Study

Rationale: Cor pulmonale (right ventricular [RV] dilation) and cor pulmonale parvus (RV shrinkage) are both described in chronic obstructive pulmonary disease (COPD). The identification of emphysema as a shared risk factor suggests that additional disease characterization is needed to understand these widely divergent cardiac processes.Objectives: To explore the relationship between computed tomography measures of emphysema and distal pulmonary arterial morphology with RV volume, and their association with exercise capacity and mortality in ever-smokers with COPD enrolled in the COPDGene Study.Methods: Epicardial (myocardium and chamber) RV volume (RVEV), distal pulmonary arterial blood vessel volume (arterial BV5: vessels <5 mm2 in cross-section), and objective measures of emphysema were extracted from 3,506 COPDGene computed tomography scans. Multivariable linear and Cox regression models and the log-rank test were used to explore the association between emphysema, arterial BV5, and RVEV with exercise capacity (6-min-walk distance) and all-cause mortality.Measurements and Main Results: The RVEV was approximately 10% smaller in Global Initiative for Chronic Obstructive Lung Disease stage 4 versus stage 1 COPD (P < 0.0001). In multivariable modeling, a 10-ml decrease in arterial BV5 (pruning) was associated with a 1-ml increase in RVEV. For a given amount of emphysema, relative preservation of the arterial BV5 was associated with a smaller RVEV. An increased RVEV was associated with reduced 6-minute-walk distance and in those with arterial pruning an increased mortality.Conclusions: Pulmonary arterial pruning is associated with clinically significant increases in RV volume in smokers with COPD and is related to exercise capacity and mortality in COPD.Clinical trial registered with www.clinicaltrials.gov (NCT00608764).

Pulmonary vascular density: comparison of findings on computed tomography imaging with histology

BACKGROUND

Exposure to cigarette smoke has been shown to lead to vascular remodelling. Computed tomography (CT) imaging measures of vascular pruning have been associated with pulmonary vascular disease, an important morbidity associated with smoking. In this study we compare CT-based measures of distal vessel loss to histological vascular and parenchymal changes.

METHODS

A retrospective review of 80 patients who had undergone lung resection identified patients with imaging appropriate for three-dimensional (3D) vascular reconstruction (n=18) and a second group for two-dimensional (2D) analysis (n=19). Measurements of the volume of the small vessels (3D) and the cross-sectional area of the small vessels (<5 mm2 cross-section) were computed. Histological measures of cross-sectional area of the vasculature and loss of alveoli septa were obtained for all subjects.

RESULTS

The 2D cross-sectional area of the vasculature on CT imaging was associated with the histological vascular cross-sectional area (r=0.69; p=0.001). The arterial small vessel volume assessed by CT correlated with the histological vascular cross-sectional area (r=0.50; p=0.04), a relationship that persisted even when adjusted for CT-derived measures of emphysema in a regression model.

CONCLUSIONS

Loss of small vessel volume in CT imaging of smokers is associated with histological loss of vascular cross-sectional area. Imaging-based quantification of pulmonary vasculature provides a noninvasive method to study the multiscale effects of smoking on the pulmonary circulation.

Dynamic right ventricular-pulmonary arterial uncoupling during maximum incremental exercise in exercise pulmonary hypertension and pulmonary arterial hypertension

Despite recent advances, the prognosis of pulmonary hypertension (PH) remains poor. While the initial insult in PH implicates the pulmonary vasculature, the functional state, exercise capacity, and survival of such patients are closely linked to right ventricular (RV) function. In the current study, we sought to investigate the effects of maximum incremental exercise on the matching of RV contractility and afterload (i.e. right ventricular-pulmonary arterial [RV-PA] coupling) in patients with exercise PH (ePH) and pulmonary arterial hypertension (PAH). End-systolic elastance (Ees), pulmonary arterial elastance (Ea), and RV-PA coupling (Ees/Ea) were determined using single-beat pressure-volume loop analysis in 40 patients that underwent maximum invasive cardiopulmonary exercise testing. Eleven patients had ePH, nine had PAH, and 20 were age-matched controls. During exercise, the impaired exertional contractile reserve in PAH was associated with blunted stroke volume index (SVI) augmentation and reduced peak oxygen consumption (peak VO₂ %predicted). Compared to PAH, ePH demonstrated increased RV contractility in response to increasing RV afterload during exercise; however, this was insufficient and resulted in reduced peak RV-PA coupling. The dynamic RV-PA uncoupling in ePH was associated with similarly blunted SVI augmentation and peak VO₂ as PAH. In conclusion, dynamic rest-to-peak exercise RV-PA uncoupling during maximum exercise blunts SV increase and reduces exercise capacity in exercise PH and PAH. In ePH, the insufficient increase in RV contractility to compensate for increasing RV afterload during maximum exercise leads to deterioration of RV-PA coupling. These data provide evidence that even in the early stages of PH, RV function is compromised.

Pulmonary Vascular Distensibility and Early Pulmonary Vascular Remodeling in Pulmonary Hypertension

BACKGROUND

Exercise stress testing of the pulmonary circulation may uncover decreased pulmonary vascular (PV) distensibility as a cause of impaired aerobic exercise capacity and right ventricular (RV)-pulmonary arterial (PA) uncoupling. As such, it may help in the differential diagnosis of unexplained dyspnea, including pulmonary hypertension (PH) and/or heart failure with preserved ejection fraction (HFpEF). We investigated rest and exercise invasive pulmonary hemodynamics, ventilation, and gas exchange in patients with unexplained dyspnea, including 44 patients with HFpEF (of whom 20 had a normal pulmonary vascular resistance [PVR] during exercise [ie, passive HFpEF] and 24 had a higher than normal exercise PVR), 22 patients with exercise PH, 19 patients with pulmonary arterial hypertension (PAH), and 24 age- and sex-matched normal control subjects.

METHODS

A PV distensibility coefficient α (%/mm Hg) was determined from multipoint PV pressure-flow plots. RV-PA coupling was quantified from the analysis of RV pressure curves to determine ratios of end-systolic to arterial elastances (Ees/Ea). Aerobic exercise capacity was estimated by peak oxygen consumption.

RESULTS

The α coefficient decreased from 1.35 ± 0.58%/mm Hg in control subjects and 1.1 ± 0.48%/mm Hg in patients with passive HFpEF to 0.62 ± 0.32%/mm Hg in exercise PH, 0.54 ± 0.27%/mm Hg in HFpEF with high exercise PVR, and 0.18 ± 0.16%/mm Hg in PAH. On multivariate analysis, PV distensibility was associated with decreased Ees/Ea and maximal volume of oxygen consumed.

CONCLUSIONS

PV distensibility is an early and sensitive hemodynamic marker of PV disease that is associated with RV-PA uncoupling and decreased aerobic exercise capacity.

Right Ventricular-Arterial Uncoupling During Exercise in Heart Failure With Preserved Ejection Fraction: Role of Pulmonary Vascular Dysfunction

BACKGROUND

Right ventricular (RV) dysfunction is associated with shortened life expectancy in heart failure with preserved ejection fraction (HFpEF). The contribution of pulmonary vascular dysfunction to RV dysfunction in HFpEF is not well understood.

METHODS

We investigated rest and exercise invasive pulmonary hemodynamics, ventilation, and gas exchange in 67 patients with HFpEF (of whom 28 had an abnormal pulmonary vascular response during exercise referred to as HFpEF+PVR group and 39 had a normal pulmonary vascular response during exercise referred to as HFpEF group) and in 21 matched control subjects.

RESULTS

Both groups of patients with HFpEF had a markedly decreased peak oxygen consumption (Vo₂), decreased oxygen delivery, and impaired chronotropic response. Single beat analysis of RV pressure waveforms was used to compute the end-systolic elastance (Ees) and pulmonary arterial elastance (Ea). Right ventricular-pulmonary artery (RV-PA) coupling was measured as the ratio of Ees/Ea. Exercise was associated with a preserved Ees response but a decreased Ees/Ea in patients with HFpEF with a normal PVR response, indicating partially preserved RV contractile reserve. In HFpEF+PVR, exercise-induced increase in Ees was markedly reduced, resulting in decreased Ees/Ea and RV-PA uncoupling. Patients with HFpEF+PVR with an exercise-induced decrease in Ees/Ea had lower pulmonary artery compliance, lower peak Vo₂, and lower stroke volume than patients with HFpEF.

CONCLUSIONS

We conclude that RV-PA uncoupling is common in HFpEF and is caused by both intrinsic RV contractile impairment and afterload mismatch. Resting and dynamic RV-PA uncoupling in HFpEF is driven by an increase in RV pulsatile rather than resistive afterload. However, with the additive effects of increased RV resistive afterload, RV-PA uncoupling worsens dynamically during exercise.

Disease Staging and Prognosis in Smokers Using Deep Learning in Chest Computed Tomography

RATIONALE

Deep learning is a powerful tool that may allow for improved outcome prediction.

OBJECTIVES

To determine if deep learning, specifically convolutional neural network (CNN) analysis, could detect and stage chronic obstructive pulmonary disease (COPD) and predict acute respiratory disease (ARD) events and mortality in smokers.

METHODS

A CNN was trained using computed tomography scans from 7,983 COPDGene participants and evaluated using 1,000 nonoverlapping COPDGene participants and 1,672 ECLIPSE participants. Logistic regression (C statistic and the Hosmer-Lemeshow test) was used to assess COPD diagnosis and ARD prediction. Cox regression (C index and the Greenwood-Nam-D'Agnostino test) was used to assess mortality.

MEASUREMENTS AND MAIN RESULTS

In COPDGene, the C statistic for the detection of COPD was 0.856. A total of 51.1% of participants in COPDGene were accurately staged and 74.95% were within one stage. In ECLIPSE, 29.4% were accurately staged and 74.6% were within one stage. In COPDGene and ECLIPSE, the C statistics for ARD events were 0.64 and 0.55, respectively, and the Hosmer-Lemeshow P values were 0.502 and 0.380, respectively, suggesting no evidence of poor calibration. In COPDGene and ECLIPSE, CNN predicted mortality with fair discrimination (C indices, 0.72 and 0.60, respectively), and without evidence of poor calibration (Greenwood-Nam-D'Agnostino P values, 0.307 and 0.331, respectively).

CONCLUSIONS

A deep-learning approach that uses only computed tomography imaging data can identify those smokers who have COPD and predict who are most likely to have ARD events and those with the highest mortality. At a population level CNN analysis may be a powerful tool for risk assessment.

EXPRESS: Statement on imaging and pulmonary hypertension from the Pulmonary Vascular Research Institute (PVRI)

Pulmonary hypertension (PH) is highly heterogeneous and despite treatment advances it remains a life-shortening condition. There have been significant advances in imaging technologies, but despite evidence of their potential clinical utility, practice remains variable, dependent in part on imaging availability and expertise. This statement summarizes current and emerging imaging modalities and their potential role in the diagnosis and assessment of suspected PH. It also includes a review of commonly encountered clinical and radiological scenarios, and imaging and modeling-based biomarkers. An expert panel was formed including clinicians, radiologists, imaging scientists, and computational modelers. Section editors generated a series of summary statements based on a review of the literature and professional experience and, following consensus review, a diagnostic algorithm and 55 statements were agreed. The diagnostic algorithm and summary statements emphasize the key role and added value of imaging in the diagnosis and assessment of PH and highlight areas requiring further research.

Pulmonary Artery-Vein Classification in CT Images Using Deep Learning

Recent studies show that pulmonary vascular diseases may specifically affect arteries or veins through different physiologic mechanisms. To detect changes in the two vascular trees, physicians manually analyze the chest computed tomography (CT) image of the patients in search of abnormalities. This process is time consuming, difficult to standardize, and thus not feasible for large clinical studies or useful in real-world clinical decision making. Therefore, automatic separation of arteries and veins in CT images is becoming of great interest, as it may help physicians to accurately diagnose pathological conditions. In this paper, we present a novel, fully automatic approach to classify vessels from chest CT images into arteries and veins. The algorithm follows three main steps: first, a scale-space particles segmentation to isolate vessels; then a 3-D convolutional neural network (CNN) to obtain a first classification of vessels; finally, graph-cuts' optimization to refine the results. To justify the usage of the proposed CNN architecture, we compared different 2-D and 3-D CNNs that may use local information from bronchus- and vessel-enhanced images provided to the network with different strategies. We also compared the proposed CNN approach with a random forests (RFs) classifier. The methodology was trained and evaluated on the superior and inferior lobes of the right lung of 18 clinical cases with noncontrast chest CT scans, in comparison with manual classification. The proposed algorithm achieves an overall accuracy of 94%, which is higher than the accuracy obtained using other CNN architectures and RF. Our method was also validated with contrast-enhanced CT scans of patients with chronic thromboembolic pulmonary hypertension to demonstrate that our model generalizes well to contrast-enhanced modalities. The proposed method outperforms state-of-the-art methods, paving the way for future use of 3-D CNN for artery/vein classification in CT images.

Longitudinal Modeling of Lung Function Trajectories in Smokers with and without Chronic Obstructive Pulmonary Disease

RATIONALE

The relationship between longitudinal lung function trajectories, chest computed tomography (CT) imaging, and genetic predisposition to chronic obstructive pulmonary disease (COPD) has not been explored.

OBJECTIVES

1) To model trajectories using a data-driven approach applied to longitudinal data spanning adulthood in the Normative Aging Study (NAS), and 2) to apply these models to demographically similar subjects in the COPDGene (Genetic Epidemiology of COPD) Study with detailed phenotypic characterization including chest CT.

METHODS

We modeled lung function trajectories in 1,060 subjects in NAS with a median follow-up time of 29 years. We assigned 3,546 non-Hispanic white males in COPDGene to these trajectories for further analysis. We assessed phenotypic and genetic differences between trajectories and across age strata.

MEASUREMENTS AND MAIN RESULTS

We identified four trajectories in NAS with differing levels of maximum lung function and rate of decline. In COPDGene, 617 subjects (17%) were assigned to the lowest trajectory and had the greatest radiologic burden of disease (P < 0.01); 1,283 subjects (36%) were assigned to a low trajectory with evidence of airway disease preceding emphysema on CT; 1,411 subjects (40%) and 237 subjects (7%) were assigned to the remaining two trajectories and tended to have preserved lung function and negligible emphysema. The genetic contribution to these trajectories was as high as 83% (P = 0.02), and membership in lower lung function trajectories was associated with greater parental histories of COPD, decreased exercise capacity, greater dyspnea, and more frequent COPD exacerbations.

CONCLUSIONS

Data-driven analysis identifies four lung function trajectories. Trajectory membership has a genetic basis and is associated with distinct lung structural abnormalities.

3D Pulmonary Artery Segmentation from CTA Scans Using Deep Learning with Realistic Data Augmentation

The characterization of the vasculature in the mediastinum, more specifically the pulmonary artery, is of vital importance for the evaluation of several pulmonary vascular diseases. Thus, the goal of this study is to automatically segment the pulmonary artery (PA) from computed tomography angiography images, which opens up the opportunity for more complex analysis of the evolution of the PA geometry in health and disease and can be used in complex fluid mechanics models or individualized medicine. For that purpose, a new 3D convolutional neural network architecture is proposed, which is trained on images coming from different patient cohorts. The network makes use a strong data augmentation paradigm based on realistic deformations generated by applying principal component analysis to the deformation fields obtained from the affine registration of several datasets. The network is validated on 91 datasets by comparing the automatic segmentations with semi-automatically delineated ground truths in terms of mean Dice and Jaccard coefficients and mean distance between surfaces, which yields values of 0.89, 0.80 and 1.25 mm, respectively. Finally, a comparison against a Unet architecture is also included.

Interstitial Features at Chest CT Enhance the Deleterious Effects of Emphysema in the COPDGene Cohort

Purpose To determine if interstitial features at chest CT enhance the effect of emphysema on clinical disease severity in smokers without clinical pulmonary fibrosis. Materials and Methods In this retrospective cohort study, an objective CT analysis tool was used to measure interstitial features (reticular changes, honeycombing, centrilobular nodules, linear scar, nodular changes, subpleural lines, and ground-glass opacities) and emphysema in 8266 participants in a study of chronic obstructive pulmonary disease (COPD) called COPDGene (recruited between October 2006 and January 2011). Additive differences in patients with emphysema with interstitial features and in those without interstitial features were analyzed by using t tests, multivariable linear regression, and Kaplan-Meier analysis. Multivariable linear and Cox regression were used to determine if interstitial features modified the effect of continuously measured emphysema on clinical measures of disease severity and mortality. Results Compared with individuals with emphysema alone, those with emphysema and interstitial features had a higher percentage predicted forced expiratory volume in 1 second (absolute difference, 6.4%; P < .001), a lower percentage predicted diffusing capacity of lung for carbon monoxide (DLCO) (absolute difference, 7.4%; P = .034), a 0.019 higher right ventricular-to-left ventricular (RVLV) volume ratio (P = .029), a 43.2-m shorter 6-minute walk distance (6MWD) (P < .001), a 5.9-point higher St George's Respiratory Questionnaire (SGRQ) score (P < .001), and 82% higher mortality (P < .001). In addition, interstitial features modified the effect of emphysema on percentage predicted DLCO, RVLV volume ratio, 6WMD, SGRQ score, and mortality (P for interaction < .05 for all). Conclusion In smokers, the combined presence of interstitial features and emphysema was associated with worse clinical disease severity and higher mortality than was emphysema alone. In addition, interstitial features enhanced the deleterious effects of emphysema on clinical disease severity and mortality.

Pruning of the Pulmonary Vasculature in Asthma. The Severe Asthma Research Program (SARP) Cohort

RATIONALE

Loss of the peripheral pulmonary vasculature, termed vascular pruning, is associated with disease severity in patients with chronic obstructive pulmonary disease.

OBJECTIVES

To determine if pulmonary vascular pruning is associated with asthma severity and exacerbations.

METHODS

We measured the total pulmonary blood vessel volume (TBV) and the blood vessel volume of vessels less than 5 mm2 in cross-sectional area (BV5) and of vessels less than 10 mm2 (BV10) in cross-sectional area on noncontrast computed tomographic scans of participants from the Severe Asthma Research Program. Lower values of the BV5 to TBV ratio (BV5/TBV) and the BV10 to TBV ratio (BV10/TBV) represented vascular pruning (loss of the peripheral pulmonary vasculature).

MEASUREMENTS AND MAIN RESULTS

Compared with healthy control subjects, patients with severe asthma had more pulmonary vascular pruning. Among those with asthma, those with poor asthma control had more pruning than those with well-controlled disease. Pruning of the pulmonary vasculature was also associated with lower percent predicted FEV1 and FVC, greater peripheral and sputum eosinophilia, and higher BAL serum amyloid A/lipoxin A4 ratio but not with low-attenuation area or with sputum neutrophilia. Compared with individuals with less pruning, individuals with the most vascular pruning had 150% greater odds of reporting an asthma exacerbation (odds ratio, 2.50; confidence interval, 1.05-5.98; P = 0.039 for BV10/TBV) and reported 45% more asthma exacerbations during follow-up (incidence rate ratio, 1.45; confidence interval, 1.02-2.06; P = 0.036 for BV10/TBV).

CONCLUSIONS

Pruning of the peripheral pulmonary vasculature is associated with asthma severity, control, and exacerbations, and with lung function and eosinophilia.

Differences in Respiratory Symptoms and Lung Structure Between Hispanic and Non-Hispanic White Smokers: A Comparative Study

Background: Prior studies have demonstrated that U.S. Hispanic smokers have a lower risk of decline in lung function and chronic obstructive pulmonary disease (COPD) compared with non-Hispanic whites (NHW). This suggests there might be racial-ethnic differences in susceptibility in cigarette smoke-induced respiratory symptoms, lung parenchymal destruction, and airway and vascular disease, as well as in extra-pulmonary manifestations of COPD. Therefore, we aimed to explore respiratory symptoms, lung function, and pulmonary and extra-pulmonary structural changes in Hispanic and NHW smokers. Methods: We compared respiratory symptoms, lung function, and computed tomography (CT) measures of emphysema-like tissue, airway disease, the branching generation number (BGN) to reach a 2-mm-lumen-diameter airway, and vascular pruning as well as muscle and fat mass between 39 Hispanic and 39 sex-, age- and smoking exposure-matched NHW smokers. Results: Hispanic smokers had higher odds of dyspnea than NHW after adjustment for COPD and asthma statuses (odds ratio[OR] = 2.96; 95% confidence interval [CI] 1.09-8.04), but no significant differences were found in lung function and CT measurements. Conclusions: While lung function and CT measures of the lung structure were similar, dyspnea is reported more frequently by Hispanic than matched-NHW smokers. It seems to be an impossible puzzle but it's easy to solve a Rubik' Cube using a few algorithms.

Ventricular Geometry From Non-contrast Non-ECG-gated CT Scans: An Imaging Marker of Cardiopulmonary Disease in Smokers

RATIONALE AND OBJECTIVES

Imaging-based assessment of cardiovascular structure and function provides clinically relevant information in smokers. Non-cardiac-gated thoracic computed tomographic (CT) scanning is increasingly leveraged for clinical care and lung cancer screening. We sought to determine if more comprehensive measures of ventricular geometry could be obtained from CT using an atlas-based surface model of the heart.

MATERIALS AND METHODS

Subcohorts of 24 subjects with cardiac magnetic resonance imaging (MRI) and 262 subjects with echocardiography were identified from COPDGene, a longitudinal observational study of smokers. A surface model of the heart was manually initialized, and then automatically optimized to fit the epicardium for each CT. Estimates of right and left ventricular (RV and LV) volume and free-wall curvature were then calculated and compared to structural and functional metrics obtained from MRI and echocardiograms.

RESULTS

CT measures of RV dimension and curvature correlated with similar measures obtained using MRI. RV and LV volume obtained from CT inversely correlated with echocardiogram-based estimates of RV systolic pressure using tricuspid regurgitation jet velocity and LV ejection fraction respectively. Patients with evidence of RV or LV dysfunction on echocardiogram had larger RV and LV dimensions on CT. Logistic regression models based on demographics and ventricular measures from CT had an area under the curve of >0.7 for the prediction of elevated right ventricular systolic pressure and ventricular failure.

CONCLUSIONS

These data suggest that non-cardiac-gated, non-contrast-enhanced thoracic CT scanning may provide insight into cardiac structure and function in smokers.

Pulmonary vascular morphology as an imaging biomarker in chronic thromboembolic pulmonary hypertension

Patients with chronic thromboembolic pulmonary hypertension (CTEPH) have morphologic changes to the pulmonary vasculature. These include pruning of the distal vessels, dilation of the proximal vessels, and increased vascular tortuosity. Advances in image processing and computer vision enable objective detection and quantification of these processes in clinically acquired computed tomographic (CT) scans. Three-dimensional reconstructions of the pulmonary vasculature were created from the CT angiograms of 18 patients with CTEPH diagnosed using imaging and hemodynamics as well as 15 control patients referred to our Dyspnea Clinic and found to have no evidence of pulmonary vascular disease. Compared to controls, CTEPH patients exhibited greater pruning of the distal vasculature (median density of small-vessel volume: 2.7 [interquartile range (IQR): 2.5-3.0] vs. 3.2 [3.0-3.8]; P = 0.008), greater dilation of proximal arteries (median fraction of blood in large arteries: 0.35 [IQR: 0.30-0.41] vs. 0.23 [0.21-0.31]; P = 0.0005), and increased tortuosity in the pulmonary arterial tree (median: 4.92% [IQR: 4.85%-5.21%] vs. 4.63% [4.39%-4.92%]; P = 0.004). CTEPH was not associated with dilation of proximal veins or increased tortuosity in the venous system. Distal pruning of the vasculature was correlated with the cardiac index (R = 0.51, P = 0.04). Quantitative models derived from CT scans can be used to measure changes in vascular morphology previously described subjectively in CTEPH. These measurements are also correlated with invasive metrics of pulmonary hemodynamics, suggesting that they may be used to assess disease severity. Further work in a larger cohort may enable the use of such measures as a biomarker for diagnostic, phenotyping, and prognostic purposes.

DERIVATION OF A TEST STATISTIC FOR EMPHYSEMA QUANTIFICATION

Density masking is the de-facto quantitative imaging phenotype for emphysema that is widely used by the clinical community. Density masking defines the burden of emphysema by a fixed threshold, usually between -910 HU and -950 HU, that has been experimentally validated with histology. In this work, we formalized emphysema quantification by means of statistical inference. We show that a non-central Gamma is a good approximation for the local distribution of image intensities for normal and emphysema tissue. We then propose a test statistic in terms of the sample mean of a truncated non-central Gamma random variable. Our results show that this approach is well-suited for the detection of emphysema and superior to standard density masking. The statistical method was tested in a dataset of 1337 samples obtained from 9 different scanner models in subjects with COPD. Results showed an increase of 17% when compared to the density masking approach, and an overall accuracy of 94.09%.

Pulmonary artery enlargement is associated with right ventricular dysfunction and loss of blood volume in small pulmonary vessels in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease causes significant morbidity and concomitant pulmonary vascular disease and cardiac dysfunction are associated with poor prognosis. Computed tomography-detected relative pulmonary artery (PA) enlargement defined as a PA to ascending aorta diameter ratio >1 (PA:A>1) is a marker for pulmonary hypertension and predicts chronic obstructive pulmonary disease exacerbations. However, little is known about the relationship between the PA:A ratio, pulmonary blood volume, and cardiac function.

METHODS AND RESULTS

A single-center prospective cohort study of patients with chronic obstructive pulmonary disease was conducted. Clinical characteristics and computed tomography metrics, including the PA:A and pulmonary blood vessel volume, were measured. Ventricular functions, volumes, and dimensions were measured by cine cardiac MRI with 3-dimensional analysis. Linear regression examined the relationships between clinical characteristics, computed tomography and cardiac MRI metrics, and 6-minute walk distance. Twenty-four patients were evaluated and those with PA:A>1 had higher right ventricular (RV) end-diastolic and end-systolic volume indices accompanied by lower RV ejection fraction (52±7% versus 60±9%; P=0.04). The PA:A correlated inversely with total intraparenchymal pulmonary blood vessel volume and the volume of distal vessels with a cross-sectional area of <5 mm(2). Lower forced expiratory volume, PA:A>1, and hyperinflation correlated with reduced RV ejection fraction. Both PA diameter and reduced RV ejection fraction were independently associated with reduced 6-minute walk distance.

CONCLUSIONS

The loss of blood volume in distal pulmonary vessels is associated with PA enlargement on computed tomography. Cardiac MRI detects early RV dysfunction and remodeling in nonsevere chronic obstructive pulmonary disease patients with a PA:A>1. Both RV dysfunction and PA enlargement are independently associated with reduced walk distance.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00608764.

Understanding the contribution of native tracheobronchial structure to lung function: CT assessment of airway morphology in never smokers

Background

Computed tomographic (CT) airway lumen narrowing is associated with lower lung function. Although volumetric CT measures of airways (wall volume [WV] and lumen volume [LV]) compared to cross sectional measures can more accurately reflect bronchial morphology, data of their use in never smokers is scarce. We hypothesize that native tracheobronchial tree morphology as assessed by volumetric CT metrics play a significant role in determining lung function in normal subjects. We aimed to assess the relationships between airway size, the projected branching generation number (BGN) to reach airways of <2mm lumen diameter –the site for airflow obstruction in smokers- and measures of lung function including forced expiratory volume in 1 second (FEV₁) and forced expiratory flow between 25% and 75% of vital capacity (FEF 25–75).

Methods

We assessed WV and LV of segmental and subsegmental airways from six bronchial paths as well as lung volume on CT scans from 106 never smokers. We calculated the lumen area ratio of the subsegmental to segmental airways and estimated the projected BGN to reach a <2mm-lumen-diameter airway assuming a dichotomized tracheobronchial tree model. Regression analysis was used to assess the relationships between airway size, BGN, FEF 25–75, and FEV₁.

Results

We found that in models adjusted for demographics, LV and WV of segmental and subsegmental airways were directly related to FEV₁ (P <0.05 for all the models). In adjusted models for age, sex, race, LV and lung volume or height, the projected BGN was directly associated with FEF 25–75 and FEV₁ (P = 0.001) where subjects with lower FEV₁ had fewer calculated branch generations between the subsegmental bronchus and small airways. There was no association between airway lumen area ratio and lung volume.

Conclusion

We conclude that in never smokers, those with smaller central airways had lower airflow and those with lower airflow had less parallel airway pathways independent of lung size. These findings suggest that variability in the structure of the tracheobronchial tree may influence the risk of developing clinically relevant smoking related airway obstruction.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0181-y) contains supplementary material, which is available to authorized users.

Morphologic Response of the Pulmonary Vasculature to Endoscopic Lung Volume Reduction

INTRODUCTION

Endoscopic Lung Volume Reduction has been used to reduce lung hyperinflation in selected patients with severe emphysema. Little is known about the effect of this procedure on the intraparenchymal pulmonary vasculature. In this study we used CT based vascular reconstruction to quantify the effect of the procedure on the pulmonary vasculature.

METHODS

Intraparenchymal vasculature was reconstructed and quantified in 12 patients with CT scans at baseline and 12 weeks following bilateral introduction of sealants in the upper lobes. The volume of each lung and each lobe was measured, and the vascular volume profile was calculated for both lower lobes. The detected vasculature was further labeled manually as arterial or venous in the right lower lobe.

RESULTS

There was an increase in the volume of the lower lobes (3.14L to 3.25L, p=0.0005). There was an increase in BV5, defined as the volume of blood vessels with cross sectional area of less than 5mm², (53.2ml to 57.9ml, p=0.03). This was found to be correlated with the increase in lower lobe volumes (R=0.65, p=0.02). The changes appear to be symmetric for veins and arteries with a correlation coefficient of 0.87 and a slope of near identity.

CONCLUSION

In the subjects studied, there was an increase, from baseline, in BV5 in the lower lobes that correlated with the change in the volume of the lower lobes. The change appeared to be symmetric for both arteries and veins. The study illustrates the use of intraparenchymal pulmonary vascular reconstruction to study morphologic changes in response to interventions.

Preoperative pulmonary vascular morphology and its relationship to postpneumonectomy hemodynamics

RATIONALE AND OBJECTIVES

Pulmonary edema and pulmonary hypertension are postsurgical complications of pneumonectomy that may represent the remaining pulmonary vasculature's inability to accommodate the entirety of the cardiac output. Quantification of the aggregate pulmonary vascular cross-sectional area (CSA) has been used to study the development of pulmonary vascular disease in smokers. In this study, we applied this technique to demonstrate the potential utility of pulmonary vascular quantification in surgical risk assessment. Our hypothesis was that those subjects with the lowest aggregate vascular CSA in the nonoperative lung would be most likely to have elevated pulmonary vascular pressures in the postoperative period.

MATERIALS AND METHODS

A total of 61 subjects with postoperative hemodynamics and adequate imaging were identified from 159 patients undergoing pneumonectomies for mesothelioma. The total CSA of blood vessels perpendicular to the plane of computed tomographic (CT) scan slices was computed for blood vessels <5 mm(2) (CSA 5 mm). This measurement expressed as a percentage of lung parenchyma area (CSA 5%) was compared to postoperative hemodynamic measurements obtained by right heart catheterization.

RESULTS

In patients where a contrasted CT scan was used (n = 26), CSA 5% was correlated with postoperative day 0 minimum cardiac index (R = 0.37, P = .03) but not with the maximum pulmonary arterial pressures. In patients with noncontrast CT scans (n = 35), CSA 5% was inversely correlated with postoperative day 0 maximum pulmonary arterial pressures (R = 0.43, P = .03) but not with the minimum cardiac index. The preoperative perfusion fraction of the nonsurgical lung did not correlate with postoperative hemodynamics.

CONCLUSIONS

CSA of pulmonary vasculature with an area ≤5 mm(2) has potential in estimating the ability of pulmonary vascular bed to accommodate postsurgical changes in pneumonectomy.

Blood glucose dynamics

Measurement of blood glucose concentration is central to the diagnosis and treatment of diabetes. Although there are large numbers of historic glucose measurements in individuals with diabetes, until recently there have been very few data sets that were recorded continuously or sampled frequently enough to reveal intrinsic blood glucose dynamics, or the change in blood glucose with time. There have even fewer such recordings from individuals not having diabetes to serve as a therapeutic target. As a result, blood glucose dynamics have generally not been used in the diagnosis or treatment of the disease. Although present blood glucose monitoring is based largely on discrete measurements, future monitoring will likely focus on analysis of blood glucose excursions. New measurements are now being obtained, and there is a need for new methods of analysis to extract the maximal information from the data. Several approaches are demonstrated here for characterization of blood glucose dynamics, and a patient profiling system is proposed. An example of new insights is the observation that there are four time scales of blood glucose variations in individuals without diabetes, and these time scales are modified or lost in diabetes.