An evidence-based strategy to screen for pulmonary arterial hypertension in systemic sclerosis

BACKGROUND

Clinical practice guidelines recommend screening all systemic sclerosis (SSc) patients for pulmonary arterial hypertension (PAH) with yearly echocardiograms. There is a paucity of evidence to support these guidelines.

RESEARCH QUESTION

Can a prediction model identify SSc patients with a very low probability of PAH and therefore not requiring annual screening echocardiogram?

STUDY DESIGN AND METHODS

We performed a case-control study of 925 unselected SSc subjects nested in a multi-centered, longitudinal cohort. The probability of PAH for each subject was calculated using the results of multivariate logistic regression models. A cut-off was identified for the estimated probability of PAH below which no subject developed PAH (100% sensitivity).

RESULTS

Study subjects were predominantly female (87.5%), with mean (SD) age 58.6 (11.7) years and disease duration of 18.2 (12.2) years. Thirty-seven subjects developed PAH during 5407.97 person-years of observation (incidence rate 0.68 per 100 person-years). Shortness of breath (SOB), diffusing capacity for carbon monoxide (DLCO) and NT-proBNP were independent predictors of PAH. All SSc-PAH cases had a probability of PAH of >1.1%. Subjects below this cut-off, none of whom had PAH, accounted for 46.2% of the study population.

INTERPRETATION

A simple prediction model identified subjects at very low probability of PAH who could potentially forego annual screening echocardiogram. This represents almost half of SSc subjects in a general SSc population. This study, which is the first evidence-based study for the rational use of follow-up echocardiograms in an unselected SSc cohort, requires validation. The scoring system is freely available online at http://pahtool.ladydavis.ca.

560 The inclusion of pulmonary arterial pressure misclassifies diastolic function using the current EACVI guidelines in pre-capillary pulmonary hypertension

Background

Pulmonary hypertension (PH) can be pre-capillary or post-capillary (PVH) etiology based on left-sided filling pressures and pulmonary vascular resistance. The 2016 EACVI/ASE Recommendations for the Evaluation of Left Ventricular Diastolic Function (LVDF) provides flow-diagrams to categorize patients. Parameters used include left atrial volume, Doppler-derived transmitral and mitral annular velocities, and systolic PA pressure (sPAP). There are no dedicated criteria to assess the diastolic function in pulmonary arterial hypertension (PAH). Additionally, diseases such as scleroderma can result in both PAH and PVH, thus including sPAP may alter LVDF diagnostic reliability in this population.

Purpose

Because elevated PAP is fundamental to PAH, we hypothesized that the EACVI/ASE diastolic function algorithm has a lower predictive value in correctly classifying diastolic function in scleroderma.

Methodology

We performed a single-center retrospective analysis of scleroderma patients who underwent complete echocardiography and comprehensive right and left heart catheterization for PH evaluation. PH categorization was defined using the 6th World Symposium hemodynamic definitions (PAH as mPAP ≥20 mmHg, PCWP ≤15 mmHg, PVR ≥ 3 WU). Diastolic function categorization used 2016 EACVI/ASE recommendations. Index catheterization and echocardiogram closest to cardiac catheterization were analyzed.

Results

260 patients underwent evaluation and 63 were diagnosed with PH. PAH was diagnosed in 35 (age 64 ±10, mPAP 55± 18 mmHg, LVEF 60 ± 6%) and PVH in 28 (age 65 ± 10, mPAP 34 ± 14 mmHg, LVEF 63 ± 6%). Of the PAH patients, 20 had normal LVEDP (≤ 12 mmHg) and 15 increased LVEDP. In the PAH normal LVEDP patients, the EACVI algorithm classified diastolic function as normal in 25%, grade 2 in 5%, Grade 3 in 5%, and "indeterminate" in 65%. In the PAH group with increased LVEDP (> 12 mmHg), 27% were incorrectly identified as normal, 7% as grade 2 dysfunction, and 66% as indeterminate. The diastolic function algorithm has a sensitivity of 27% and specificity of 75% to diagnose a LVEDP ≤ 12 mmHg, with an AUC of 0.508 (p = 0.91). With exclusion of sPAP from the algorithm, indeterminate cases in both PAH groups were reclassified as normal, resulting in improved sensitivity (93%) but poorer specificity (10%), and a similar AUC (0.517, p = 0.72). In PVH patients, the algorithm performed better with a sensitivity of 63% and specificity of 83% to predict LVEDP > 12 mmHg with AUC 0.773, p = 0.017.

Conclusion

In scleroderma patients with PAH, the EACVI diastolic algorithm performs poorly and is confounded by including PAP as a parameter. The sensitivity of the algorithm is improved by the exclusion of sPAP although with reduced specificity. It remains inadequate to reliably diagnose normal LVEDP. While useful in other populations, algorithm modifications including exclusion of PAP, must be employed in suspected scleroderma PAH.

A review of STRIDE-2 and STRIDE-2X: the case for selective endothelin receptor blockade

BACKGROUND

Pulmonary arterial hypertension remains incurable and has previously required difficult parenteral therapy. Endothelin-1(ET-1) is an important mediator of pulmonary arterial hypertension. The recent availability of oral therapies, including endothelin receptor antagonists, has improved ease of use for patients, but most patients remain symptomatic to a significant degree. Two classes of ET-1 receptors have been described, ET(A) and ET(B). It has previously been unclear whether both receptors must be blocked in pulmonary arterial hypertension, or only the ET(A) receptor.

MATERIALS AND METHODS

The Sitaxsentan To Relieve ImpaireD Exercise-2 (STRIDE-2) study followed by STRIDE-2X exposed patients with pulmonary arterial hypertension to the highly selective ET(A) antagonist sitaxsentan (n = 145), or to bosentan (n = 84), a nonselective ET(A) and ET(B) antagonist. The total exposure duration and follow-up period was 1 year. Pre-specified comparisons included time to discontinuation of monotherapy, time to clinical worsening, incidence of elevated hepatic transaminase levels > 3 x upper limit of normal and survival.

RESULTS

Sitaxsentan therapy showed significant benefit over bosentan with respect to discontinuation of monotherapy at 1 year (24% vs. 43%, P = 0.002), clinical worsening at 1 year (28% vs. 39%, P = 0.0425), elevated hepatic transaminases at 1 year (4% vs. 14%, P = 0.014) and 1-year survival (96% vs. 88%, P = 0.028).

CONCLUSIONS

STRIDE-2 and its extension, STRIDE-2X, suggest significant benefit of sitaxsentan compared with bosentan, in terms of efficacy and reduced hepatotoxicity. The former may be related to the high ET(A) receptor selectivity of sitaxsentan.

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.

The 6-min walk test (6MW) as an efficacy endpoint in pulmonary arterial hypertension clinical trials: Demonstration of a ceiling effect

BACKGROUND

PAH trials traditionally use 6MW as the primary endpoint. Concerns regarding a "ceiling effect" masking efficacy have led to exclusion of patients with milder disease from most trials (BL 6MW>450 m). STRIDE I evaluated the selective endothelin A receptor antagonist, sitaxsentan (SITAX), in a 12-week randomized, double-blind, trial (178 patients) employing placebo (PBO), 100 mg or 300 mg SITAX orally once daily in PAH and included patients with NYHA class II, congenital heart disease and a BL 6MW>450 m, groups often excluded from previous trials.

METHODS

We analyzed 6MW effects For All Pts (intention-to treat) and those meeting Traditional enrollment criteria, defined as patients with NYHA class III or IV and 6MW< or =450 m at BL with idiopathic PAH or PAH related to connective tissue disease. The 100 mg and 300 mg SITAX arms are pooled based on similar treatment effects on 6MW.

CONCLUSION

Existence of a "ceiling effect" is supported by these data. The magnitude of the treatment effect and statistical power when using 6MW as the endpoint. Comparisons between PAH trials that do not adjust for the effects of differing enrollment criteria require caution.

Pulmonary capillary endothelial dysfunction in early systemic sclerosis

OBJECTIVE

Pulmonary capillary endothelium-bound angiotensin-converting enzyme (PCEB-ACE) activity is a sensitive and quantifiable index of endothelial function in vivo. Systemic sclerosis (SSc) is characterized by endothelial damage and excess collagen formation, causing mainly pulmonary hypertension (PH) in the limited cutaneous SSc (lcSSc) subset and interstitial lung disease with pulmonary interstitial fibrosis (PIF) in the diffuse cutaneous SSc (dcSSc) subset. This study was undertaken to investigate the hypothesis that PCEB-ACE activity is reduced early in SSc, in the absence of PH or PIF.

METHODS

Applying indicator-dilution techniques, we measured single-pass transpulmonary hydrolysis and percent metabolism (%M) of a synthetic ACE substrate and calculated functional capillary surface area (FCSA) in 25 SSc patients and 11 controls. Substrate hydrolysis and %M reflect ACE activity per capillary; FCSA reflects ACE activity per vascular bed.

RESULTS

PCEB-ACE activity was decreased in both SSc subsets. Among patients without PH, substrate hydrolysis and %M were decreased in patients with lcSSc and more profoundly in those with dcSSc; loss of FCSA normalized to body surface area (FCSA/BSA) was observed in dcSSc, but not in lcSSc. High-resolution computed tomography of the lung, performed in all SSc patients, revealed no correlation between substrate %M, hydrolysis, or FCSA/BSA and the degree of PIF; 5 dcSSc and 5 lcSSc patients with no detectable PIF exhibited decreases in hydrolysis and %M, while FCSA/BSA was decreased only in dcSSc.

CONCLUSION

Depression of PCEB-ACE activity, indicating pulmonary endothelial dysfunction, occurs early in SSc, in the absence of PH or PIF, and is more pronounced, at this early pulmonary disease stage, in dcSSc than in lcSSc.

Non-visualization of sentinel lymph node in patients with breast cancer

Histological evaluation of the first draining lymph node (sentinel node) in the axilla of patients with breast cancer has dramatically altered the surgical approach to these patients, with sparing of the axilla if no tumour cells are identified. In a fraction of patients imaged after peri-tumoural injection of the breast, there is no visualization of the sentinel node. We retrospectively analysed the status of patients whose nodes were visualized and of patients whose nodes failed to visualize, to define the variables associated with non-visualization of the sentinel node. Seventy-four breast cancer patients were imaged following peri-tumoural injection of filtered 99Tc(m)-sulfur colloid, immediately and up to 5.5 h post-injection. The scintigraphic data were analysed with reference to the patient's age, histology, grade, site and size of tumour, previous diagnostic procedure and time interval to scan, using univariate analysis and a logistic regression model. A sentinel node was visualized in 53 of 74 women (72%). Comparison of patients with non-visualized versus visualized sentinel nodes disclosed no statistically significant univariate relation to age of the patients (P = 0.10), size of tumour (P = 0.46), site (P = 0.26), histology [invasive ductal carcinoma in 16 of 20 (80%) non-visualized cases, and in 43 of 53 (81%) visualized patients], prior excision biopsy (P = 0.36) and time interval to surgery (P = 0.29). Tumour grade was the only significant variable on univariate analysis (P = 0.03), though multivariate analysis showed that none of the independent parameters were statistically significant. In 39 patients with an upper outer quadrant tumour, the location of the sentinel node was not limited to the axilla and even crossed the midline of the breast. Our results show that none of the independent variables is associated with non-visualization of sentinel lymph node on preoperative lymphoscintigraphy of patients with breast cancer, though the tumour grade may have contributed to non-visualization of this node. The non-axillary drainage from upper outer quadrant tumours suggests the routine use of lymphoscintigraphy prior to axillary dissection.

Pulmonary capillary endothelium-bound angiotensin-converting enzyme activity in acute lung injury

BACKGROUND

Pulmonary capillary endothelium-bound (PCEB) angiotensin-converting ectoenzyme (ACE) activity alteration is an early, sensitive, and quantifiable lung injury index in animal models. We hypothesized that (1) PCEB-ACE alterations can be found in patients with acute lung injury (ALI) and (2) PCEB-ACE activity correlates with the severity of lung injury and may be used as a quantifiable marker of the underlying pulmonary capillary endothelial dysfunction.

METHODS AND RESULTS

Applying indicator-dilution techniques, we measured single-pass transpulmonary hydrolysis of the synthetic ACE substrate (3)H-benzoyl-Phe-Ala-Pro (BPAP) in 33 mechanically ventilated, critically ill patients with a lung injury score (LIS) ranging from 0 (no lung injury) to 3.7 (severe lung injury) and calculated the kinetic parameter A(max)/K(m). Both parameters decreased early during the ALI continuum and were inversely related to APACHE II score and LIS. Hydrolysis decreased with increasing cardiac output (CO), whereas 2 different patterns were observed between CO and A(max)/K(m).

CONCLUSIONS

PCEB-ACE activity decreases early during ALI, correlates with the clinical severity of both the lung injury and the underlying disease, and may be used as a quantifiable marker of underlying pulmonary capillary endothelial dysfunction.

Heparin-like molecules inhibit pulmonary vascular pericyte proliferation in vitro

Proliferation of vascular pericytes (PCs), smooth muscle-like cells found in the distal microvasculature, contributes to vascular remodeling in pulmonary hypertension. The factors controlling lung PC quiescence in normal states are poorly understood. We demonstrate that exogenous heparin and heparan sulfate proteoglycans inhibit rat lung PC proliferation in vitro as does pulmonary vascular subendothelial matrix, particularly its heparan sulfate component. Heparin inhibits the intracellular alkalinization essential to proliferation, and we show that inhibition of alkalinization by 5-(N, N-dimethyl)amiloride also reduces PC proliferation. As shown by DNA staining and fluorescence-activated cell sorting analysis, heparin does not induce apoptosis in PCs. However, heparin maintains lung PCs in the G(0)/G(1) growth phase. Heparin induces production of p21, a potent inhibitor of cyclin-dependent kinases, thereby potentially identifying a fundamental mechanism by which heparin inhibits proliferation in smooth muscle-like cells. These studies establish additional similarities between lung PCs and smooth muscle cells and provide further understanding of growth control in the lung microvasculature. They also further support the rationale that heparin-like molecules might be therapeutically beneficial in pulmonary hypertension.

Continuous intravenous epoprostenol for pulmonary hypertension due to the scleroderma spectrum of disease. A randomized, controlled trial

BACKGROUND

Pulmonary hypertension is a progressive and often fatal complication of the scleroderma spectrum of disease for which no treatment has been proven effective in a randomized trial.

OBJECTIVE

To determine the effect of epoprostenol on pulmonary hypertension secondary to the scleroderma spectrum of disease.

DESIGN

Randomized, open-label, controlled trial.

SETTING

17 pulmonary hypertension referral centers.

PATIENTS

111 patients with moderate to severe pulmonary hypertension.

INTERVENTION

Epoprostenol plus conventional therapy or conventional therapy alone.

MEASUREMENTS

The primary outcome measure was exercise capacity. Other measures were cardiopulmonary hemodynamics, signs and symptoms of pulmonary hypertension and scleroderma, and survival.

RESULTS

Exercise capacity improved with epoprostenol (median distance walked in 6 minutes, 316 m at 12 weeks compared with 270 m at baseline) but decreased with conventional therapy (192 m at 12 weeks compared with 240 m at baseline). The difference between treatment groups in the median distance walked at week 12 was 108 m (95% CI, 55.2 m to 180.0 m) (P < 0.001). Hemodynamics improved at 12 weeks with epoprostenol. The changes in mean pulmonary artery pressure for the epoprostenol and conventional therapy groups were -5.0 and 0.9 mm Hg, respectively (difference, -6.0 mm Hg [CI, -9.0 to -3.0 mm Hg), and the mean changes in pulmonary vascular resistance were -4.6 and 0.9 mm Hg/L per minute, respectively (difference, -5.5 mm Hg/L per minute [CI, -7.3 to -3.7 mm Hg/L per minute). Twenty-one patients treated with epoprostenol and no patients receiving conventional therapy showed improved New York Heart Association functional class. Borg Dyspnea Scores and Dyspnea-Fatigue Ratings improved in the epoprostenol group. Trends toward greater improvement in severity of the Raynaud phenomenon and fewer new digital ulcers were seen in the epoprostenol group. Four patients in the epoprostenol group and five in the conventional therapy group died (P value not significant). Side effects of epoprostenol therapy included jaw pain, nausea, and anorexia. Adverse events related to the epoprostenol delivery system included sepsis, cellulitis, hemorrhage, and pneumothorax (4% incidence for each condition).

CONCLUSIONS

Continuous epoprostenol therapy improves exercise capacity and cardiopulmonary hemodynamics in patients with pulmonary hypertension due to the scleroderma spectrum of disease.

Mitral stenosis obscuring the diagnosis of plexogenic pulmonary arteriopathy and familial pulmonary hypertension

A patient who died after surgery for critical mitral stenosis was found to have underlying unrecognised plexogenic pulmonary arteriopathy and familial pulmonary hypertension. The importance of recognising familial pulmonary hypertension is discussed, together with the contribution of genetic and other risk factors to plexogenic pulmonary arteriopathy.

Continuous infusion of epoprostenol improves the net balance between pulmonary endothelin-1 clearance and release in primary pulmonary hypertension

BACKGROUND

Primary pulmonary hypertension results from progressive narrowing of the precapillary pulmonary vasculature. A variety of endothelial abnormalities have been identified, including a net reduction in pulmonary clearance of the vasoconstrictor and smooth muscle mitogen endothelin-1. In many patients, net pulmonary release of endothelin-1 is observed. Chronic infusions of epoprostenol (prostacyclin) improve functional capacity, survival, and hemodynamics in patients with advanced primary pulmonary hypertension. We hypothesized that the epoprostenol infusions, as compared with conventional therapy, might alter the abnormal pulmonary endothelin-1 homeostasis.

METHODS AND RESULTS

Using a subset of patients from a larger randomized study comparing epoprostenol plus conventional therapy (n=11 in the present study) with conventional therapy alone (n=7 in the present study), we determined the ratio of plasma endothelin-1 levels in systemic arterial blood leaving the lung to levels in mixed venous blood entering the lung both before randomization and after 88 days of continuous therapy. There were no differences between the 2 groups before therapy, but by day 88, the epoprostenol-treated group had a greater proportion of patients (82%) with an arterial/venous ratio <1 than did the conventional therapy group, in which only 29% of patients had a ratio <1 (P<0.05).

CONCLUSIONS

These results suggest that continuous epoprostenol therapy may have a beneficial effect on the balance between endothelin-1 clearance and release in many patients with primary pulmonary hypertension and may provide one explanation for the salutary effect of epoprostenol in this disease.

Pulmonary capillary endothelium-bound angiotensin-converting enzyme activity in humans

BACKGROUND

Pulmonary endothelium has metabolic functions including the conversion of angiotensin I to angiotensin II by angiotensin-converting ectoenzyme (ACE). In this study, we have validated an indicator-dilution technique that provides estimations of dynamically perfused capillary surface area (DPCSA) in humans, and we have characterized pulmonary endothelial ACE in vivo.

METHODS AND RESULTS

In 12 adults, single-pass transpulmonary (one or both lungs) hydrolysis of the specific ACE substrate 3H-benzoyl-Phe-Ala-Pro (3H-BPAP) was measured and expressed as % metabolism (%M) and v=-ln(1-M). We also calculated Amax/Km, an index of DPCSA. %M (70.1+/-3.2 vs 67.9+/-3.1) and v (1.29+/-0.14 vs 1. 20+/-0.12) were similar in both lungs and the right lung, respectively, whereas Amax/Km//body surface area decreased from 2460+/-193 to 1318+/-115 mL/min per square meter.

CONCLUSIONS

Pulmonary endothelial ACE activity can be assessed in humans at the bedside by means of indicator-dilution techniques. Our data suggest homogeneous pulmonary capillary ACE concentrations and capillary transit times (tc) in both human lungs, and similar tc within the normal range of cardiac index. Amax/Km in the right lung is 54% of total Amax/Km in both lungs, suggesting that Amax/Km is a reliable and quantifiable index of DPCSA in humans.

Effects of endotoxin on lung pericytes in vitro

Lipopolysaccharide released during bacterial sepsis causes acute lung injury and ARDS. Pulmonary microvascular injury is a feature of ARDS, and vascular remodeling develops, leading to pulmonary hypertension. Pericytes in the lung circulation proliferate and contribute to the remodeling seen in experimental sepsis. It is unknown whether endotoxin can directly stimulate pericyte growth or induce contraction. We show that lipopolysaccharide from Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae increases rat lung pericyte proliferation in vitro by up to 72% on day 7 of exposure (P < 0.001), with E. coli being most potent. Lipid A is the active portion of the lipopolysaccharide, with equal activity at one-tenth the dose of lipopolysaccharide. Endotoxin's mitogenic effect requires the presence of serum, consistent with the requirement for a soluble CD14 receptor in the serum. Using FACS analysis, the pericytes lack surface CD14 receptors. Lipopolysaccharide exposure rapidly increases intracellular calcium and induces contraction of pericytes plated onto silicone membranes. Thus, endotoxin is a direct mitogen for lung pericytes in vitro and also induces pericyte contraction. Endotoxin, present in lung tissue early during sepsis, might directly contribute to the vascular remodeling in sepsis-induced lung injury.

Evaluation of right ventricular systolic pressure during incremental exercise by Doppler echocardiography in adults with atrial septal defect

STUDY OBJECTIVES

Pulmonary hypertension is the most important complication in patients with atrial septal defect (ASD), but its role in limiting exercise has not been examined. This study sought to evaluate exercise performance in adults with ASD and determine the contribution of elevated pulmonary artery pressure in limiting exercise capacity.

DESIGN

We used Doppler echocardiography during exercise in 10 adults (aged 34 to 70 years) with isolated ASD (New York Heart Association class I, II) and an equal number of matched control subjects. Incremental exercise was performed on an electrically braked upright cycle ergometer. Expired gases and VE were measured breath-by-breath. Two-dimensional and Doppler echocardiographic images were obtained at rest prior to exercise to determine ASD size, stroke volume (SV), shunt ratio (Qp:Qs), right ventricular outflow tract (RVOT) size, and right ventricular systolic pressure at rest (RVSPr). Doppler echocardiography was repeated at peak exercise to measure right ventricular systolic pressure during exercise (RVSPex).

RESULTS

Resting echocardiography revealed that RVOT was larger (21+/-4 vs 35+/-8 mm, mean+/-SD; p=0.0009) and RVSPr tended to be higher (17+/-8 vs 31+/-8 mm Hg; p=0.08) in ASD; however, left ventricular SV was not different (64+/-23 vs 58+/-23 mL; p>0.05), compared with control subjects. Despite normal resting left ventricular function, ASD patients had a significant reduction in maximum oxygen uptake (VO2max) (22.9+/-5.4 vs 17.3+/-4.2 mL/kg/min; p=0.005). RVSPex was higher (19+/-8 vs 51+/-10 mm Hg; p=0.001) and the mean RVSP-VO2 slope (1+/-2 vs 18+/-3 mm Hg/L/min; p=0.003) and intercept (17+/-4 vs 27+/-4 mm Hg; p=0.05) were higher in the ASD group. VO2max correlated inversely with both RVSPr (r=-0.69; p=0.007) and RVSPex (r=-0.67; p=0.01).

CONCLUSION

These findings suggest that adults with ASD have reduced exercise performance, which may be associated with an abnormal increase in pulmonary artery pressure during exercise.

Effects of long-term infusion of prostacyclin (epoprostenol) on echocardiographic measures of right ventricular structure and function in primary pulmonary hypertension. Primary Pulmonary Hypertension Study Group

BACKGROUND

Right heart failure is an important cause of morbidity and mortality in primary pulmonary hypertension. In a recent prospective, randomized study of severely symptomatic patients, treatment with prostacyclin (epoprostenol) produced improvements in hemodynamics, quality of life, and survival. This article describes the echocardiographic characteristics of participants in this trial; the relationship of echocardiographic variables to hemodynamic parameters, exercise capacity, and quality of life; and the echocardiographic changes associated with prostacyclin therapy.

METHODS AND RESULTS

The 81 patients enrolled in this multicenter trial were randomized to treatment with a long-term infusion of prostacyclin in addition to conventional therapy (n = 41) or conventional therapy alone (n = 40) for 12 weeks. Echocardiograms and assessments of hemodynamics, exercise capacity, and quality of life were performed before and after the treatment phase. On baseline evaluation, patients had marked right ventricular dilatation and dysfunction, abnormal septal curvature, and significant tricuspid regurgitation with a high regurgitant velocity. Pericardial effusions were common. More pronounced abnormalities in right heart structure and function were associated with higher pulmonary arterial and mean right atrial pressures, lower cardiac index, and impaired exercise capacity but had no predictable relationship to quality-of-life indicators. The 12-week infusion of prostacyclin had beneficial effects on right ventricular size, curvature of the interventricular septum, and maximal tricuspid regurgitant jet velocity.

CONCLUSIONS

The echocardiographic manifestations of severe primary pulmonary hypertension reflect abnormalities in hemodynamics and exercise capacity. Prostacyclin has beneficial effects on right heart structure and function that may contribute to the clinical improvement and prolonged survival observed with this drug.

A comparison of continuous intravenous epoprostenol (prostacyclin) with conventional therapy for primary pulmonary hypertension

BACKGROUND

Primary pulmonary hypertension is a progressive disease for which no treatment has been shown in a prospective, randomized trial to improve survival.

METHODS

We conducted a 12-week prospective, randomized, multicenter open trial comparing the effects of the continuous intravenous infusion of epoprostenol (formerly called prostacyclin) plus conventional therapy with those of conventional therapy alone in 81 patients with severe primary pulmonary hypertension (New York Heart Association functional class III or IV).

RESULTS

Exercise capacity was improved in the 41 patients treated with epoprostenol (median distance walked in six minutes, 362 m at 12 weeks vs. 315 m at base line), but it decreased in the 40 patients treated with conventional therapy alone (204 m at 12 weeks vs. 270 m at base line; P < 0.002 for the comparison of the treatment groups). Indexes of the quality of life were improved only in the epoprostenol group (P < 0.01). Hemodynamics improved at 12 weeks in the epoprostenol-treated patients. The changes in mean pulmonary-artery pressure for the epoprostenol and control groups were -8 percent and +3 percent, respectively (difference in mean change, -6.7 mm Hg; 95 percent confidence interval, -10.7 to -2.6 mm Hg; P < 0.002), and the mean changes in pulmonary vascular resistance for the epoprostenol and control groups were -21 percent and +9 percent, respectively (difference in mean change, -4.9 mm Hg/liter/min; 95 percent confidence interval, -7.6 to -2.3 mm Hg/liter/min; P < 0.001). Eight patients died during the study, all of whom had been randomly assigned to conventional therapy (P = 0.003). Serious complications included four episodes of catheter-related sepsis and one thrombotic event.

CONCLUSIONS

As compared with conventional therapy, the continuous intravenous infusion of epoprostenol produced symptomatic and hemodynamic improvement, as well as improved survival in patients with severe primary pulmonary hypertension.

Platelet-activating factor stimulates lung pericyte growth in vitro

Platelet-activating factor (PAF) is released from activated leukocytes and endothelial cells in sepsis, lung injury, and the adult respiratory distress syndrome. With these disorders, pulmonary hypertension develops, partly due to muscularization of the microvasculature by proliferation of pericytes. PAF may be a mediator of this process. Therefore, we examined the effects of PAF on in vitro growth of rat lung pericytes. Compared with control growth, semisynthetic PAF (10(-9) M) stimulated the 7-day mean growth of proliferating pericytes by 31% in medium with serum and 29% without serum and of previously growth-arrested pericytes by 12% with serum and 23% without serum. These effects were blocked by the PAF-receptor blocker CV-3988. PAF also increased [3H]thymidine incorporation into pericytes by 79%. Synthetic 16:0 PAF stimulated pericyte growth, but 18:0 PAF did not. PAF exposure did not induce apoptosis in pericytes. Thus PAF compounds, similar to those found in vivo, stimulate lung pericyte growth in vitro. PAF may act as a direct cytokine on cells involved in muscularization of the pulmonary vessel walls.

Short-term pulmonary vasodilation with L-arginine in pulmonary hypertension

BACKGROUND

Endothelial dysfunction may contribute to the pathogenesis of pulmonary hypertension through impaired production of the endothelium-derived vasodilator nitric oxide (NO). L-Arginine, the substrate for NO synthase (NOS), has a vasodilatory effect in systemic vascular beds and can correct abnormal endothelium-dependent vasodilation. It has been suggested that these two effects of L-arginine are mediated through NOS metabolism and enhanced NO production. Therefore, we assessed the short-term pulmonary hemodynamic effects of exogenous L-arginine in patients with pulmonary hypertension of various origins.

METHODS AND RESULTS

During continuous hemodynamic monitoring, 10 subjects with pulmonary hypertension (mean pulmonary artery pressure [PAP], 54 +/- 5 mm Hg [mean +/- SEM]) received a 30-minute control infusion of hypertonic saline followed by a 30-minute infusion of 500 mg/kg of L-arginine. The hemodynamic effects of L-arginine were compared with those of prostacyclin titrated to maximally tolerated doses. The hemodynamic response to L-arginine was also studied in 5 subjects with heart failure but without pulmonary hypertension (mean PAP, 20 +/- 2 mm Hg) and 5 healthy control subjects. In subjects with pulmonary hypertension, infusion of L-arginine reduced mean PAP by 15.8 +/- 3.6% (P < .005) and pulmonary vascular resistance (PVR) by 27.6 +/- 5.8% (P < .005) compared with decreases of 13.0 +/- 5.5% (P < .005) and 46.6 +/- 6.2% (P < .005), respectively, with prostacyclin. L-Arginine infusion also increased the mean plasma level of L-arginine from 59 +/- 6 mumol/L to 10,726 +/- 868 mumol/L (P < .005), which was associated with a significant increase in the plasma level of L-citrulline, the immediate product of NOS metabolism of L-arginine. Moreover, the peak plasma level of L-citrulline correlated significantly with the reductions in mean PAP (r = .71, P < .05) and PVR (r = .70, P < .05), consistent with vasodilation mediated by NOS metabolism of exogenous L-arginine and increased NO production. L-Arginine also had a modest hypotensive effect in healthy control subjects and reduced systemic vascular resistance in subjects with heart failure in the absence of pulmonary hypertension. However, only small reductions in absolute pulmonary vascular resistance were observed in this latter group in response to L-arginine that did not reach significance.

CONCLUSIONS

An exaggerated short-term pulmonary vasodilatory response to L-arginine in patients with pulmonary hypertension suggests a relative impairment in pulmonary vascular endothelial NO production that may contribute to increased pulmonary vascular tone and thus be important in the pathophysiology of pulmonary hypertension.

Endothelin-1 in acute lung injury and the adult respiratory distress syndrome

Endothelial damage is a hallmark of acute lung injury. Endothelial mediators may increase pulmonary vascular tone and induce pulmonary arterial muscularization, thereby contributing to the pulmonary hypertension seen with acute lung injury. We measured plasma levels and net pulmonary clearance of endothelin-1, a potent endothelium-derived vasoconstrictor peptide and smooth muscle mitogen, in 26 patients with early acute lung injury, the adult respiratory distress syndrome, and pulmonary hypertension. Nineteen had another data collection at clinical improvement or worsening. Control subjects (n = 25) had no pulmonary hypertension or lung injury. Initial mixed venous and systemic arterial plasma endothelin-1 levels were elevated (4.6 +/- 0.6 SEM and 4.9 +/- 0.6 pg/ml, respectively) as compared with control subjects (0.9 +/- 0.1 and 0.6 +/- 0.1 pg/ml). The systemic arterial/venous endothelin-1 ratio was 1.1 +/- 0.1 (0.7 +/- 0.1 in control subjects), indicating a reduction in normal net pulmonary endothelin-1 clearance. With clinical improvement, as compared with clinical worsening, mean plasma endothelin-1 levels, arterial/venous ratio, and pulmonary arterial pressure fell significantly towards normal. Thus, patients with acute lung injury have marked early increases in circulating plasma endothelin-1 levels, associated with abnormal pulmonary endothelin-1 metabolism. These abnormalities reverse in patients who recover. Through its actions, endothelin-1 could contribute to the pulmonary hypertension seen in acute lung injury.

Expression of endothelin-1 in the lungs of patients with pulmonary hypertension

BACKGROUND

Pulmonary hypertension is characterized by an increase in vascular tone or an abnormal proliferation of muscle cells in the walls of small pulmonary arteries. Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide with important mitogenic properties. It has therefore been suggested that endothelin-1 may contribute to increases in pulmonary arterial tone or smooth-muscle proliferation in patients with pulmonary hypertension. We studied the sites and magnitude of endothelin-1 production in the lungs of patients with various causes of pulmonary hypertension.

METHODS

We studied the distribution of endothelin-1-like immunoreactivity (by immunocytochemical analysis) and endothelin-1 messenger RNA (by in situ hybridization) in lung specimens from 15 control subjects, 11 patients with plexogenic pulmonary arteriopathy (grades 4 through 6), and 17 patients with secondary pulmonary hypertension and pulmonary arteriopathy of grades 1 through 3.

RESULTS

In the controls, endothelin-1-like immunoreactivity was rarely seen in vascular endothelial cells. In the patients with pulmonary hypertension, endothelin-1-like immunoreactivity was abundant, predominantly in endothelial cells of pulmonary arteries with medial thickening and intimal fibrosis. Likewise, endothelin-1 messenger RNA was increased in the patients with pulmonary hypertension and was expressed primarily at sites of endothelin-1-like immunoreactivity. There was a strong correlation between the intensity of endothelin-1-like immunoreactivity and pulmonary vascular resistance in the patients with plexogenic pulmonary arteriopathy, but not in those with secondary pulmonary hypertension.

CONCLUSIONS

Pulmonary hypertension is associated with the increased expression of endothelin-1 in vascular endothelial cells, suggesting that the local production of endothelin-1 may contribute to the vascular abnormalities associated with this disorder.

Hemodynamic differences between continual positive and two types of negative pressure ventilation

In seven anesthetized dogs, ventilated with matching lung volumes, tidal volumes, and respiratory rates, we compared the effects on cardiac output (CO), arterial venous oxygen saturation difference (SaO2 - SVO2), and femoral and inferior vena cava pressure (1) intermittent positive pressure ventilation with positive end-expiratory pressure (CPPV); (2) iron-lung ventilation with negative end-expiratory pressure (ILV-NEEP); (3) grid and wrap ventilation with NEEP applied to the thorax and upper abdomen (G&W-NEEP). The values of CO and SaO2 - SVO2 with ILV-NEEP were similar to those with CPPV. However, with G&W-NEEP as compared with ILV-NEEP, mean CO was greater (2.9 versus 2.6 L/min, p = 0.02) and mean (SaO2 - SVO2) was lower (26.6% versus 28.3%, p = NS). Mean PFEM-IVC was higher with G&W-NEEP than with the other types of ventilation. We conclude that (1) ILV-NEEP is hemodynamically equivalent to CPPV and (2) G&W-NEEP has less adverse hemodynamic consequences. has less adverse hemodynamic consequences.

Lung scintigraphy in pulmonary capillary hemangiomatosis. A rare disorder causing primary pulmonary hypertension

The authors report the results of lung scintigraphy in two patients with primary pulmonary hypertension caused by pulmonary capillary hemangiomatosis, a rare disorder resulting from the proliferation of histologically normal capillaries in the lung. Perfusion studies revealed a nonhomogeneous pattern with some focal defects, similar to that seen with some other histologic types of primary pulmonary hypertension. The mechanisms underlying this perfusion pattern are unknown.

Increased plasma endothelin-1 in pulmonary hypertension: marker or mediator of disease?

OBJECTIVE

To explore the role of endothelin-1, a potent endothelial-derived vasoconstrictor peptide, in pulmonary hypertension, by measuring its concentration in arterial and venous plasma.

DESIGN

A survey, case series study.

SETTING

University-affiliated hospitals and outpatient clinics.

PATIENTS

Twenty-seven patients with pulmonary hypertension: 7 with primary, and 20 with secondary pulmonary hypertension of various causes. The control groups (n = 16) comprised 8 healthy volunteers and 8 patients with coronary artery disease but without evidence of pulmonary hypertension.

MEASUREMENTS AND MAIN RESULTS

Pulmonary artery pressure was markedly increased (94/43 +/- 23/13 mm Hg) in the patients with pulmonary hypertension. Venous plasma immunoreactive endothelin-1, measured by a specific radioimmunoassay, was significantly higher in patients with pulmonary hypertension (3.5 +/- 2.5 pg/mL, P less than 0.001) than in normal subjects (1.45 +/- 0.45 pg/mL), or patients with coronary disease (0.75 +/- 0.64 pg/mL). The arterial-to-venous ratio of immunoreactive endothelin-1 was significantly greater than unity in primary pulmonary hypertension (2.21 +/- 0.72, P = 0.01), whereas the patients with secondary pulmonary hypertension had a mean ratio not different from 1 (0.97 +/- 0.42). In contrast, the mean arterial-to-venous ratios were significantly less than unity in both control groups (0.59 +/- 0.35, and 0.54 +/- 0.64; P less than 0.02, for normal subjects and coronary disease patients, respectively), indicating a possible clearance of endothelin-1 across the healthy lung.

CONCLUSIONS

Patient with pulmonary hypertension have substantial alterations in plasma immunoreactive endothelin-1, which may reflect changes in net release or clearance of endothelin-1 by the lung. In patients with primary pulmonary hypertension, the high levels in arterial compared with venous plasma suggest pulmonary production of endothelin-1, which may contribute to elevated pulmonary vascular resistance.

Interspecies variation in the cellular phase of blood fibrinolytic activity

In normal humans, whole blood fibrinolytic activity is three to six times greater than that of companion plasma. This additional activity derives from neutrophil enzymes, with possible contributions from other cell types. Rats and dogs are frequently used to study fibrinolysis in animal models of human disease. Compared with humans, rats are relatively neutropenic, whereas dogs have a relative neutrophilic leukocytosis. Interspecies variation in cellular phase fibrinolytic activity has not been examined. We therefore determined whole blood, plasma, and cellular phase fibrinolytic activity in 27 rats and 6 dogs, using a 125I-fibrin solid phase assay. Whole blood and plasma activities were similar in rats, consistent with very low cellular activity. Dogs, however, had high cellular phase activity, making up an average 91% of whole blood activity. These results suggest that blood fibrinolytic mechanisms in rats differ from those in humans and dogs, and that this difference should be considered when studying fibrinolysis in models of human disease.

Endothelin release is inhibited by coculture of endothelial cells with cells of vascular media

Endothelin is a potent vasoconstrictor peptide and a smooth muscle mitogen produced in large amounts by endothelial cells in culture. To determine whether other cellular elements of the vessel wall modify the release or clearance of endothelin, we studied the effect of coculture of endothelial cells with vascular smooth muscle cells or fibroblasts on endothelin release. Endothelial cells were grown to confluence on microcarrier beads and transferred to dishes containing confluent cultures of smooth muscle cells or fibroblasts or control media only. In parallel experiments, endothelial cells on microcarrier beads were incubated in media conditioned by 48-h exposure to smooth muscle cells or fibroblasts. Endothelin concentration was determined by radioimmunoassay (rabbit anti-endothelin-1 serum). Endothelial cells alone released large amounts of endothelin: 169 +/- 60 and 982 +/- 237 pg/10(6) endothelial cells at 4 and 24 h, respectively. Endothelin accumulation was markedly reduced in coculture with smooth muscle cells or fibroblasts by 81 +/- 10 and 49 +/- 5% (P less than 0.05), respectively, at 24 h. This difference could not be explained by smooth muscle cell binding or degradation of endothelin. Furthermore, smooth muscle cell- or fibroblast-conditioned media significantly reduced endothelin release, and twofold concentration of smooth muscle cell-conditioned media fully reproduced the inhibition of endothelin release found in coculture, confirming the presence of a transferable inhibitor. Therefore, we propose that endothelin secretion from endothelial cells may be regulated by an inhibitory factor produced by the vascular media. This mechanism might limit the production of endothelin in intact vessels and thereby protect against excessive vasoconstriction or proliferation of vascular target cells.

Cellular-phase fibrinolysis and coronary reperfusion during acute myocardial infarction: a study in patients receiving intravenous streptokinase-methylprednisolone therapy

Activation of plasma plasminogen to plasmin is the objective of current strategies for thrombolytic therapy. Although thrombolytic activity in blood involves a large cellular component as well as that in plasma, the contribution of this cellular phase to clinical thrombolysis has not been examined. Using a 125I-fibrin test tube assay, we determined blood, plasma and calculated cellular phase fibrinolytic activities in 39 patients with acute myocardial infarction before, immediately after, and at 2 hours after therapy with an intravenous streptokinase-methylprednisolone regimen. By coronary angiography and time to peak creatine phosphokinase levels, 32 patients had coronary reperfusion and 7 did not. Before streptokinase therapy, cellular phase activity of patients who reperfused was more than 2-fold greater than that of patients who did not reperfuse (p less than 0.001), while plasma activities were identical, suggesting that intrinsic cellular phase activity may be a determinant of the success of subsequent thrombolytic therapy. In both groups, in addition to the expected (and similar) increases in plasma activity, cellular phase activity increased when compared with pre-treatment values (+96% to +248%; p less than 0.001), with accompanying increase in blood granulocyte count (+23% to +65%), indicating that blood cells, as well as plasma, are major contributors to streptokinase-mediated fibrinolysis. Cellular phase stimulation was reproduced in a patient receiving streptokinase without methylprednisolone, and by addition of streptokinase to normal blood in vitro, indicating that streptokinase alone could account for these effects. Increased cellular phase activity in patients who reperfused after streptokinase was similar to that in those who did not reperfuse, when pre-treatment values were considered. These findings indicate that initial cellular phase activity in blood may determine subsequent fibrinolytic response, and that there is a significant cellular phase component to the fibrinolytic response to streptokinase, probably mediated by increased numbers of blood neutrophils, with a possible contribution from increased activity of individual neutrophils.

Regional pulmonary perfusion following human heart-lung transplantation

Ventilation and perfusion scans were obtained in six subjects who had undergone heart-lung transplantation with consequent denervation of the cardiopulmonary axis. Two of the subjects had developed obliterative bronchiolitis, which is believed to be a form of chronic rejection. Their pulmonary function tests demonstrated airflow obstruction and their scintigraphic studies were abnormal. In the remaining four subjects without obstructive airways disease, ventilation and planar perfusion scans were normal. Single photon emission computed tomography imaging of pulmonary perfusion in these patients revealed a layered distribution of blood flow indistinguishable from that of normal individuals. It is concluded that neurogenic mechanisms have little influence on the pattern of local pulmonary blood flow at rest.

Effects of dimethylthiourea on chronic hypoxia-induced pulmonary arterial remodelling and ventricular hypertrophy in rats

Ischemia, followed by reperfusion and restoration of oxygen to tissues, generates hydrogen peroxide which in turn generates injurious free radicals, particularly hydroxyl. Chronic hypoxia may also result in liberation of free radicals. In rats, chronic hypoxia causes pulmonary hypertension, associated with structural remodelling of pulmonary arteries, polycythemia, and vasoconstriction. We studied in rats the effects of dimethylthiourea (DMTU), a hydroxyl and hydrogen peroxide scavenger, on acute hypoxic vasoconstriction, and on the arterial structure and development of polycythemia after chronic hypoxia (FIO2 0.10 for 10 days, daily DMTU). DMTU did not affect acute vasoconstriction nor polycythemia. It significantly reduced muscularization of alveolar wall and alveolar duct arteries, medial thickening of alveolar wall and preacinar arteries, and right ventricular hypertrophy, suggesting reduction of pulmonary hypertension. However, DMTU caused marked growth retardation in both control and hypoxic rats, an effect not previously described. In other rats a similar degree of growth retardation due to reduced food intake failed to prevent the effects of hypoxia, suggesting that DMTU's effect is not through this mechanism. The results of this study support but do not confirm the hypothesis that free radicals may have a role in the pathogenesis of the arterial structural changes in the microcirculation contributing to chronic hypoxic pulmonary hypertension. However, in view of DMTU's effects on growth, definitive testing of the hypothesis will not be possible until other, less toxic, chronic hydroxyl scavengers become available.

Hemothorax and hemopericardium in a patient with Bean's blue rubber bleb nevus syndrome

A patient with Bean's blue rubber bleb nevus syndrome presented with a hemothorax, and 18 years earlier had presented with "idiopathic" hemopercardium and tamponade. Typical hemangiomas were found in the pleura and skin. This is the first report of intrathoracic bleeding with this disorder.

Altered artery mechanics and structure in monocrotaline pulmonary hypertension

Pulmonary hypertension in rats, induced by an injection of monocrotaline, is associated with changes in the wall structure of the pulmonary arterial bed. We have studied the effects of this remodeling on mechanical properties of cylindrical pulmonary artery segments from rats 21 days after monocrotaline (MCT) injection. Resting and active (KCl induced) circumference-tension relationships were established for segments of extrapulmonary and intrapulmonary arteries isolated from the hilum and the fifth lateral branch from the axial pathway (all preacinar). The thicknesses of the vessel wall, the media, and adventitia were measured at several positions around the circumference of the artery by computerized analysis of histological cross sections of the segments fixed at a standard circumference. Resting and active stress were also calculated. The study shows that active circumferential tension and active stress are reduced in vessels from MCT-treated rats. Based on our findings, it is unlikely that altered contractile function of preacinar arteries contributes significantly to the increased vascular resistance seen in this model.

Familial pulmonary capillary hemangiomatosis resulting in primary pulmonary hypertension

We describe the first cases of familial pulmonary capillary hemangiomatosis, a disorder in which capillaries in the lungs proliferate. Three siblings died from primary pulmonary hypertension. One developed pulmonary congestion preterminally after vasodilator treatment. The inheritance pattern seems autosomal recessive. Lung specimens obtained in two siblings showed extensive pulmonary capillary hemangiomatosis, with normal capillaries proliferating into veins and alveoli. Including our patients, four of the nine patients with pulmonary capillary hemangiomatosis have presented with the clinical picture of primary pulmonary hypertension. Thus, pulmonary capillary hemangiomatosis should be considered as a histologic pattern of primary pulmonary hypertension. Most other cases of pulmonary capillary hemangiomatosis have been similar to pulmonary veno-occlusive disease. Recently, disorders involving the proliferation of cytologically normal capillaries have been termed angiogenic diseases. Pulmonary capillary hemangiomatosis may be an angiogenic disease.