Primary pulmonary hypertension

Peripheral airway obstruction in primary pulmonary hypertension

BACKGROUND

As there is controversy about changes in lung function in primary pulmonary hypertension (PPH), lung mechanics were assessed with a focus on expiratory airflow in relation to pulmonary haemodynamics.

METHODS

A cross sectional study was performed in 64 controls and 171 patients with PPH (117 women) of mean (SD) age 45 (13) years, pulmonary artery pressure (PAPmean) 57 (15) mm Hg, and pulmonary vascular resistance 1371 (644) dyne.s/cm(5).

RESULTS

Mean (SD) total lung capacity was similar in patients with PPH and controls (98 (12)% predicted v 102 (17)% predicted, mean difference -4 (95% confidence interval (CI) -7.89 to -0.11); residual volume (RV) was increased (118 (24)% predicted v 109 (27)% predicted, mean difference 9 (95% CI 1.86 to 16.14); and vital capacity (VC) was decreased (91 (16)% predicted v 102 (10)% predicted, mean difference -11 (95% CI 15.19 to -6.80). RV/TLC was increased (117 (27)% predicted v 97 (29)% predicted, mean difference 20 (95% CI 12.3 to 27.8)) and correlated with PAPmean (r=0.31, p<0.001). In patients with PAPmean above the median of 56 mm Hg, RV/TLC was further increased (125 (32)% predicted v 111 (22)% predicted, mean difference -14 (95% CI -22.2 to -5.8)). Expiratory flow-volume curves were reduced and curvilinear in patients with PPH.

CONCLUSIONS

Peripheral airway obstruction is common in PPH and is more pronounced in severe disease. This may contribute to symptoms. Reversibility of bronchodilation and relation to exercise capacity need further evaluation.

Early endosomal regulation of Smad-dependent signaling in endothelial cells

Transforming growth factor beta (TGFbeta) receptors require SARA for phosphorylation of the downstream transducing Smad proteins. SARA, a FYVE finger protein, binds to membrane lipids suggesting that activated receptors may interact with downstream signaling molecules at discrete endocytic locations. In the present study, we reveal a critical role for the early endocytic compartment in regulating Smad-dependent signaling. Not only is SARA localized on early endosomes, but also its minimal FYVE finger sequence is sufficient for early endosomal targeting. Expression of a SARA mutant protein lacking the FYVE finger inhibits downstream activin A signaling in endothelial cells. Moreover, a dominant-negative mutant of Rab5, a crucial protein for early endosome dynamics, causes phosphorylation and nuclear translocation of Smads leading to constitutive (i.e. ligand independent) transcriptional activation of a Smad-dependent promoter in endothelial cells. As inhibition of endocytosis using the K44A negative mutant of dynamin and RN-tre did not lead to activation of Smad-dependent transcription, the effects of the dominant-negative Rab5 are likely to be a consequence of altered membrane trafficking of constitutively formed TGFbeta/activin type I/II receptor complexes at the level of early endosomes. The results suggest an important interconnection between early endosomal dynamics and TGFbeta/activin signal transduction pathways.

Failure of resting echocardiography and cardiac catheterization to identify pulmonary hypertension in two patients with type I Gaucher disease

Pulmonary hypertension (PHT) is a complication of Gaucher disease. Screening with echocardiography is recommended for Gaucher patients. Two patients naive to enzyme replacement therapy are presented in whom resting echocardiography revealed no evidence of PHT. One of the patients also had normal pulmonary artery pressures at cardiac catheterization. The diagnosis of PHT was made with open lung biopsy in one patient and dobutamine echocardiography in the other. In both cases, diagnosis of PHT altered patient management. Resting echocardiographic assessment may fail to identify PHT in patients with Gaucher disease.

Hyperthyroidism and pulmonary hypertension

In recent years, many authors have described several cases revealing an association between hyperthyroidism and pulmonary hypertension (PH). This observational study was designed to evaluate the incidence of PH in hyperthyroidism and was set in a department of internal medicine and pulmonary diseases with an out-patients department of endocrinology. Thirty-four patients, 25 women and nine men, with a mean age of 38 +/- 15 SD years participated. Twenty had Graves' disease and 14 had a nodular goitre. The patients were divided into two equally matched groups: those with a recently diagnosed hyperthyroidism, taking no drugs (group 1; n = 17) and those in a euthyroid state taking methimazole (group 2; n= 17). Transthoracic Doppler echocardiography was performed and systolic pulmonary artery pressurements of (PAPs) was determined by the tricuspid regurgitation method using the Bernoulli equation. Measurements of triiodothyronine, tetraiodothyronine, free thyroxine (Ft4), thyroid-stimulating hormone (TSH) and antithyroglobulin and antimicrosomal antibodies were also taken. We found a mild PH in seven patients of group 1 and in none of group 2. The mean +/- SD systolic pulmonaryartery pressurewas 28.88 +/- 6.41 in group 1 and 22.53 +/- 1.84 ingroup 2 (P<0.0001). A correlation was found between the TSH value and PAPs (r = -082;P < 0.001) and Ft4 and PAPs (r = 0 85; P < 0.001) in group 1. These findings indicate the presence of a frequent association between PH and hyperthyroidism. We suggest that hyperthyroidism be included in the differential diagnosis of PH.

Current management of primary pulmonary hypertension

Primary pulmonary hypertension (PPH) is a rare disorder with an annual incidence of 1 to 2 per million people. The aetiology of this disorder is unknown, but it appears to result from an abnormal interaction of environmental and genetic factors leading to a vasculopathy. The pulmonary arteries in these patients exhibit a spectrum of pathological lesions ranging from the early medial hypertrophy to the end-stage fibrotic plexiform lesions. This characteristic pathology is also observed in pulmonary hypertension resulting from connective tissue disease (particularly systemic sclerosis), HIV infection, portal hypertension and certain toxins. PPH is a condition that is difficult to diagnose and treat, with a median survival of 2.8 years in historical studies. One of the difficulties in treating patients with PHH is that the subacute nature of disease presentation often prevents an accurate diagnosis during the early stages of the illness. Progressive dyspnoea on exertion is the most common presenting symptom. Diagnostic evaluation should include electrocardiography, chest radiograph and echocardiography, and laboratory and other studies to evaluate for secondary causes (e.g. pulmonary function tests, chest computed tomography and ventilation/perfusion scans, pulmonary arteriogram, cardiopulmonary testing, right heart catherisation). PHH is a disorder for which there is no known cure. Current medical and surgical treatment options for patients with PHH include anticoagulation, vasodilators and transplantation. Calcium channel antagonists are currently the oral drugs of choice for the treatment of patients with New York Heart Association (NYHA) Class II disease. These agents, in particular the dihydropyridine compounds, have beneficial effects on haemodynamics and right ventricular function, and possibly increased survival. Epoprostenol is administered by intravenous infusion, and studies have demonstrated short- and long-term improvements in symptoms, haemodynamics and survival. It is well tolerated and has become the treatment of choice for patients with NYHA Class III and IV disease. Inotropic agents are used as a bridge to transplant, which is indicated in patients who do not respond to maximal medical therapy. Experience has shown that single lung, double lung and heart-lung transplantation are approximately of equal efficacy. Currently, single lung transplant appears to be the procedure of choice. Newer agents, such as sildenafil, beraprost and bosentan, are presently being evaluated for the treatment of this disorder. Future study should include elucidation of the pathogenic mechanisms in the development of this vasculopathy, which will hopefully lead to the development of improved treatment options for patients with PHH.

Oxygen therapy improves cardiac index and pulmonary vascular resistance in patients with pulmonary hypertension

STUDY OBJECTIVES

We tested the hypothesis that breathing 100% oxygen could result in selective pulmonary vasodilatation in patients with pulmonary hypertension, including those patients who would not meet current Health Care Finance Administration guidelines for long-term oxygen therapy.

DESIGN, SETTING, AND PATIENTS

From 1996 to 1999, 23 adult patients (mean +/- SEM age, 51 +/- 4 years) with pulmonary arterial hypertension without left-heart failure underwent cardiac catheterization in a university teaching hospital while breathing air and then 100% oxygen.

MEASUREMENTS AND RESULTS

Treatment with 100% oxygen increased arterial oxygen saturation (91 +/- 1% to 99 +/- 0.1%, p < 0.05) and PaO(2) (64 +/- 3 to 309 +/- 28 mm Hg, p < 0.05). Treatment with 100% oxygen also decreased mean pulmonary artery pressure (56 +/- 3 to 53 +/- 2 mm Hg, p < 0.05) and increased cardiac index (2.1 +/- 0.1 to 2.5 +/- 0.2 L/min/m(2), p < 0.05). Calculated mean pulmonary vascular resistance (PVR) decreased from 14.1 +/- 1.4 to 10.6 +/- 1.0 Wood units (p < 0.05). Vasodilatation with 100% oxygen occurred preferentially in the pulmonary circulation (PVR/systemic vascular resistance, 0.53 +/- 0.04 to 0.48 +/- 0.03; p < 0.05). The magnitude of the PVR response to oxygen therapy was correlated only with decreasing patient age (r = 0.45, p < 0.05).

CONCLUSIONS

Treatment with 100% oxygen is a selective pulmonary vasodilator in patients with pulmonary hypertension, regardless of primary diagnosis, baseline oxygenation, or right ventricular function. Development of disease-specific oxygen prescription guidelines warrants consideration.

Pulmonary hypertensive diseases

The commonest causes of pulmonary hypertension are secondary to endstage pulmonary disease or congenital heart disease (including structural abnormalities of the pulmonary veins). Less obvious causes include sleep disordered breathing due to obstructive sleep apnoea or neuromuscular disease, and occult interstitial lung disease. When these have been excluded, the primary pulmonary vascular diseases should be considered. These are primary pulmonary hypertension; pulmonary veno-occlusive disease; pulmonary embolic disease (thromboembolism, and non-thrombotic embolism) and invasive pulmonary capillary haemangiomatosis. The clinical signs and chest X-ray appearances are often non-specific. Echocardiography can often estimate pulmonary artery pressure and exclude congenital heart disease. Right heart catheterization is usually needed to confirm the diagnosis, estimate any reversibility of elevated pulmonary vascular resistance and exclude other causes. Precise diagnosis may require an open lung biopsy. For many of these conditions, treatment is difficult and the prognosis poor unless the child has a lung transplant.

Pulmonary hypertension: diagnostics and therapeutics

Pulmonary hypertension (PH) may develop because of a spectrum of insults to the lungs; in some patients, there seems to be no cause. Noninvasive tests, such as standard chest radiography, electrocardiography, and transthoracic Doppler echocardiography, provide effective screening if PH is suspected. This synopsis focuses on these screening studies and the more common clinical problems, including primary cardiac abnormalities, obstructive sleep apnea, chronic pulmonary embolism, pulmonary parenchymal problems, connective tissue disorders, cirrhosis with portal hypertension, and use of appetite suppressants, that should be considered when PH exists. Treatment options for PH, including intravenous prostacyclin (epoprostenol), and investigational agents such as subcutaneous or oral prostacyclin analogues and oral endothelin receptor antagonists are described.