Acute hemodynamic responses to inhaled nitric oxide in patients with limited scleroderma and isolated pulmonary hypertension

Reactivity of pulmonary circulation and right ventricle function to inhaled nitric oxide in systemic sclerosis patients

Systemic sclerosis (SSc) is complicated by pulmonary hypertension and right ventricle (RV) failure in approximately 10% of the patients. Factors influencing the reactivity of pulmonary circulation to vasodilators are not established, while the examination of vasoreactivity is important in determining the treatment, because systemic administration of oral vasodilators can induce severe adverse events in nonresponders. The mechanism of RV failure in SSc is unclear and may result either from increased RV afterload or intrinsic myocardial disease. The aim of the study was to assess the reactivity of pulmonary circulation to inhaled nitric oxide (iNO) and to evaluate its influence on RV function in SSc patients with elevated right ventricle systolic pressure (RVSP). In 60 SSc patients aged 24-73 (58 females, two males; 33 patients with limited SSc and 27 with diffuse SSc), echocardiographic examination with tissue Doppler echocardiography (TDE) was performed. RV function was measured by systolic (S) and early diastolic (E) velocity of tricuspid annulus by TDE. In patients with RVSP >45 mmHg, the reactivity of pulmonary circulation was assessed by iNO test. High-resolution computerized tomography (HRCT) was performed to assess the extent of pulmonary fibrosis. Of 14 SSc subjects with elevated RVSP (13 females, one male; RVSP 47-62 mmHg), positive reaction to iNO was observed in five (RVSP decreased from 51.6 ± 3.7 to 32.24 ± 2.3 mmHg); nine patients were not reactive (RVSP 53.5 ± 5.7 mmHg before iNO vs. 49.6 ± 6.7 mmHg). RV systolic function was decreased in patients with elevated RVSP as compared to the patients with normal pulmonary pressure (S velocity 13.2 ± 1.3 vs. 14.4 ± 1.6 cm/s, respectively, p < 0.05). Significant increase of RV systolic function during iNO test was found in reactive patients only (S velocity before iNO 12.8 ± 1.2 cm/s, during iNO 14.5 ± 1.5 cm/s, p < 0.01). RVSP decrease strongly correlated with S velocity increase (r = 0.95, p < 0.0001). Response to iNO was found only in limited form of SSc; diffuse SSc patients showed no response. Pulmonary fibrosis on HRCT was more frequent in subjects nonreactive to iNO (67% of patients) than in the reactive group (40% of patients). The reactivity of pulmonary circulation to iNO in SSc patients with elevated RVSP was found predominantly in limited form of the disease. Pulmonary fibrosis typical for diffuse SSc was more frequent in nonreactive subjects. Elevated pulmonary pressure plays an important role in RV systolic dysfunction. Pulmonary pressure decrease during iNO test leads to the improvement of RV systolic function. Therapy for right-heart failure in reactive SSc patients should be directed, if possible, at the decrease in pulmonary resistance.

Pulmonary vasodilator testing and use of calcium channel blockers in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) encompasses a number of diseases responsible for a specific set of hemodynamic findings during right heart catheterization. During initial workup, pulmonary vasodilator testing is performed. A positive acute pulmonary vasodilator test predicts better survival and response to calcium channel blocker (CCB) therapy. There is lack of consensus on the preferred agent for determining acute pulmonary vasoreactivity. The ACCP guidelines and the 4(th) World Symposium on Pulmonary Hypertension support the use of intravenous epoprostenol or nitric oxide (NO) as the preferred agents for pulmonary vasodilator testing. A decrease in the mean pulmonary artery pressure by at least 10 mmHg to reach an absolute value of 40 mmHg or less without a decrease in cardiac output is currently considered a positive pulmonary vasodilator test. A positive test by the current recommended criteria is observed in about 10-15% of patients with idiopathic PAH. Approximately half of these patients will experience long-term benefits with CCBs. A positive test may select patients with an earlier or less aggressive form of disease, which may carry a better prognosis. A positive vasodilator test is observed very infrequently in patients with pulmonary arterial hypertension other than idiopathic PAH or anorexigen associated PAH. This article reviews the literature regarding pulmonary vasodilator testing and use of CCB therapy in patients with PAH, while identifying the gaps in knowledge concerning this diagnostic procedure.

The nitric oxide/cGMP signaling pathway in pulmonary hypertension

This article briefly reviews the background of endothelium-dependent vasorelaxation, describes the nitric oxide/cGMP/protein kinase pathway and its role in modulating pulmonary vascular tone and remodeling, and describes three approaches that target the nitric oxide/cGMP pathway in the treatment of patients with pulmonary arterial hypertension.

Chronic thromboembolic and pulmonary arterial hypertension share acute vasoreactivity properties

BACKGROUND

Pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) are the major classes of pulmonary hypertensive disorders according to the World Health Organization; both lead to right heart failure and death. A better understanding of disease mechanisms has led to the suggestion that the thromboembolic and nonthromboembolic types of pulmonary hypertension may share pathophysiologic features. We therefore compared acute vasoreactivity and proximal pulmonary artery compliance in patients with PAH and CTEPH during the initial diagnostic heart catheterization.

METHODS

Right heart catheterization using a flow-directed Swan-Ganz catheter was performed in patients with CTEPH (n = 22) and PAH (n = 35). Pulmonary hemodynamics were assessed at baseline, during the inhalation of 40 ppm of nitric oxide, and 30 min after the inhalation of 10 mug of iloprost. To assess the proximal pulmonary artery compliance, the pulse pressure (PP) [systolic-diastolic pressure] and the fractional PP (PPf) [divided by the mean pressure] were calculated.

RESULTS

Both vasodilators produced similar hemodynamic improvement, and the difference between CTEPH and PAH was not significant. The baseline PP and PPf did not vary between the two groups.

CONCLUSION

Patients with PAH and CTEPH show similar acute vasoreactivity to inhaled nitric oxide and iloprost, and have similar pulmonary artery compliance. These findings support the presence of some shared pathophysiologic pathways in both disorders and may lead to therapeutic implications in patients with inoperable CTEPH.

Hemodynamics and survival in patients with pulmonary arterial hypertension related to systemic sclerosis

STUDY OBJECTIVES

The goal of this study was to determine whether the survival of patients with pulmonary hypertension related to systemic sclerosis (SScPH) was different from that of patients with other forms of pulmonary arterial hypertension.

DESIGN

Retrospective cohort study.

SETTING

Tertiary care medical center.

PATIENTS

Our cohort was composed of 33 patients with pulmonary hypertension that is sporadic, familial, or related to anorexigen use (PPH) and 22 patients with SScPH who underwent initial pulmonary artery catheterization and vasodilator study at our center between January 1997 and June 2001.

MEASUREMENTS AND RESULTS

Patients with SScPH had somewhat lower percentage of predicted lung volumes than patients with PPH (total lung capacity, 80% vs 92%; p = 0.06) and had lower percentage of predicted diffusion capacity of the lung for carbon monoxide (42% vs 68%; p = 0.0002). Right atrial pressure, pulmonary artery pressure, and cardiac index were similar between the groups. Patients with SScPH and PPH were treated with usual medical therapies, such as digoxin, warfarin, and continuous IV epoprostenol. Despite these similarities, the risk of death in patients with SScPH was higher than in patients with PPH (unadjusted hazard ratio, 2.9; 95% confidence interval, 1.1 to 7.8; p = 0.03). This increased risk appeared to persist after adjustment for a variety of demographic, hemodynamic, or treatment variables.

CONCLUSIONS

Despite having similar hemodynamics, patients with SScPH have a higher risk of death than patients with PPH. Future studies of the mechanism and therapy of pulmonary arterial hypertension should focus on the distinctions between the different forms of this disease.

Pulmonary hypertension associated with connective tissue disease

Pulmonary arterial hypertension is a life threatening complication of several connective tissue diseases including scleroderma (both diffuse and limited scleroderma, or the CREST syndrome--calcinosis cutis, Raynaud's phenomenon, esophageal dysfunction, sclerodactyly, and telangectasia), systemic lupus erythomatosis (SLE), mixed connective tissue disease (MCTD), and less commonly, rheumatoid arthritis (RA) and dermatomyositis/polymyositis. This report reviews the occurrence of this complication, potential etiologies, clinical presentation, and treatment options.

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.

Cellular pathophysiology and therapy of pulmonary hypertension

The identification of several mutations of the bone morphogenetic protein receptor 2 (BMPR2) gene, a member of the transforming growth factor beta receptor family, gives hope for new insights into the pathophysiology of pulmonary hypertension. Genetic predisposition might dictate the responses of pulmonary artery fibroblasts, smooth muscle cells, and endothelial cells, as well as platelets and leukocytes, or their specific interactions with different extrinsic factors. These cells possess distinct subtypes and interact with each other. Pulmonary hypertension is associated with vasoconstriction, remodeling, and in situ thrombosis of the pulmonary arteries, but the initial events and their relationship to the genetic background are presently unknown. Current therapeutic approaches are based on our knowledge of the physiologic regulation of pulmonary artery tone, pathophysiologic changes, and our clinical experience with different treatment strategies. Beyond diuretics and anticoagulants, prostaglandins are generally accepted therapeutic agents for primary pulmonary hypertension and related diseases, whereas high-dose calcium-channel blockers are reserved for a small subset of patients, those who respond favorably to vasodilators in an acute test. Long-term intravenous prostacyclin infusion has become the most important specific therapy for primary pulmonary hypertension and associated diseases. However, this therapy is hampered by catheter complications and systemic side effects. Alternative application routes of prostacyclin or its stable analogs may avoid these problems. Inhaled application of the prostacyclin analog iloprost results in predominant pulmonary vasodilation with few systemic side effects and may possess clinical efficacy similar to that of intravenous prostacyclin. Inhaled nitric oxide is widely accepted as a screening agent for active responders to vasodilators and has a similar hemodynamic profile as inhaled iloprost, although the percentage of responders is considerably lower. However, there are unsolved toxicologic questions and practical difficulties concerning the safe long-term application of nitric oxide. Combining inhaled vasodilators with phosphodiesterase inhibitors may prolong the duration of the effects and improve the convenience of inhaled therapy for pulmonary hypertension. Therapeutic approaches in the future may aim at the transforming growth factor beta pathway and at the identification of early stages of the disease to prevent further disease progression.

Inhaled nitric oxide in cardiology

Inhaled nitric oxide (INO) allows selective pulmonary vasodilatation with rapidity of action. It is effective in the acute management of reversible pulmonary hypertension in cardiac medical and surgical patients and is also useful in assessing the pulmonary vasodilator capacity in patients with chronic pulmonary hypertension. This review will examine the role of INO in the management of cardiac patients, compared to alternatives where available. The use of INO in cardiac failure, post-operative cardiac patients, patients with congestive cardiac failure or congenital heart disease will also be reviewed. Newer alternatives with prolonged pulmonary activity and simpler administration are also discussed.

Helium inhalation enhances vasodilator effect of inhaled nitric oxide on pulmonary vessels in hypoxic dogs

There are theoretical and experimental indications that the presence of He as a balance gas markedly increase the diffusion velocity of other gases contained in a gas mixture. We allowed dogs with pulmonary vasoconstriction induced by hypoxia to inhale a mixture of 5 parts per million (ppm) of nitric oxide (NO) and O(2) balanced with He (NO in He) instead of N(2) (NO in N(2)). The dilating effect of NO in He and NO in N(2) on the pulmonary artery was evaluated by determining conventional pulmonary hemodynamic parameters, mean pulmonary artery (PA) pressure (MPAP), and pulmonary vascular resistance indexed to body surface area (PVRI), pulmonary impedance (Z), and the recently developed hemodynamic index, time-corrected wave intensity (WI). The main findings in this study were as follows: 1) hypoxia increased MPAP, PVRI, Z at 0 Hz (Z(0)), Z at the first harmonics, characteristic impedance (Z(c)), the reflection coefficient (Gamma), and the first peak of WI; 2) NO in N(2) reduced Z(0) and Gamma; and 3) NO in He reduced the first peak of WI and reduced Z(0) and Gamma more than NO in N(2). The enhanced vasodilatory effect of NO in He might be associated with facilitated diffusion of NO diluted in the gas mixture with He. In conclusion, increased efficacy of NO in He offers the possibility to reduce the inhaled NO concentration.

Inhaled nitric oxide selectively dilates pulmonary vasculature in adult patients with pulmonary hypertension, irrespective of etiology

OBJECTIVES

We sought to compare the responses of patients with pulmonary hypertension from primary and secondary causes (PPH and SPH, respectively) to inhaled nitric oxide (iNO) in the cardiac catheterization laboratory.

BACKGROUND

Pulmonary hypertension can lead to right ventricular pressure overload and failure. Although vasodilators are effective as therapy in patients with PPH, less is known about their role in adults with SPH. Inhaled nitric oxide can accurately predict the response to other vasodilators in PPH and could be similarly utilized in SPH.

METHODS

Forty-two patients (26 to 77 years old) with pulmonary hypertension during cardiac catheterization received iNO. Demographic and hemodynamic data were collected. Their response to iNO was defined by a decrease of > or =20% in mean pulmonary artery (PA) pressure or pulmonary vascular resistance (PVR).

RESULTS

Mean PA pressures and PVR were lower during nitric oxide (NO) inhalation in all patients with pulmonary hypertension. Seventy-eight percent of patients with PPH and 83% of patients with SPH were responders to iNO. A trend was seen toward a greater response with larger doses of NO in patients with SPH. Nitric oxide was a more sensitive predictor of response (79%), compared with inhaled oxygen (64%), and was well tolerated, with no evidence of systemic effects. Elevation in right ventricular end-diastolic pressure appeared to predict poor vasodilatory response to iNO.

CONCLUSIONS

Nitric oxide is a safe and effective screening agent for pulmonary vasoreactivity. Regardless of etiology of pulmonary hypertension, pulmonary vasoreactivity is frequently demonstrated with the use of NO. Right ventricular diastolic dysfunction may predict a poor vasodilator response.

Hemodynamic effects of epoprostenol in patients with systemic sclerosis and pulmonary hypertension

STUDY OBJECTIVES

To determine the cause of pulmonary hypertension (PH) in systemic sclerosis (SSc) patients since PH can occur because of pulmonary arteriopathy, pulmonary parenchymal destruction, and left ventricular cardiac dysfunction.

DESIGN AND SETTING

Consecutive case series in a university hospital.

PATIENTS

Nine SSc patients with PH (mean pulmonary artery pressure, 41 mm Hg), with (n = 6) or without (n = 3) concomitant interstitial lung disease (ILD).

METHODS

Acute infusion of epoprostenol was begun at 2 ng/kg/min and was titrated upward at a rate of 2 ng/kg/min every 30 min until symptomatic complications developed or pulmonary artery vascular resistance (PVR) was reduced by 50%.

RESULTS

Eight of nine patients demonstrated a reduction of > or = 20% in PVR, suggesting that vasoreactivity is common despite the presence of significant ILD. A single patient had no response to infusion with unchanged hemodynamics and oxygenation. One patient developed hypoxemia as cardiac output increased, suggesting a worsening of ventilation/perfusion matching or the presence of an anatomic shunt. Acute pulmonary edema developed in one patient at an infusion rate of 6 ng/kg/min. The results of cardiac catheterization suggested that pulmonary edema was caused by SSc heart disease.

CONCLUSION

SSc patients with ILD have diverse and sometimes multiple causes of PH that can be determined by short-term epoprostenol infusion. Beneficial effects can be obtained from epoprostenol despite extensive ILD.

Inhaled iloprost to treat severe pulmonary hypertension. An uncontrolled trial. German PPH Study Group

BACKGROUND

Inhaled aerosolized iloprost, a stable prostacyclin analogue, has been considered a selective pulmonary vasodilator in the management of pulmonary hypertension.

OBJECTIVE

To assess the efficacy of inhaled iloprost in the treatment of life-threatening pulmonary hypertension.

DESIGN

Open, uncontrolled, multicenter study.

SETTING

Intensive care units and pulmonary hypertension clinics at six university hospitals in Germany.

PATIENTS

19 patients who had progressive right-heart failure despite receiving maximum conventional therapy (12 with primary pulmonary hypertension, 3 with pulmonary hypertension related to collagen vascular disease without lung fibrosis, and 4 with secondary pulmonary hypertension).

INTERVENTION

Inhaled iloprost, 6 to 12 times daily (50 to 200 microg/d).

MEASUREMENTS

Right-heart catheterization and distance walked in 6 minutes at baseline and after 3 months of therapy.

RESULTS

During the first 3 months of therapy, New York Heart Association functional class improved in 8 patients and was unchanged in 7 patients. Four patients died, 3 of right-heart failure and 1 of sepsis. The acute hemodynamic response to inhaled iloprost was predominant pulmonary vasodilatation with little systemic effect at baseline and at 3 months (data available for 12 patients). Hemodynamic variables were improved at 3 months, and the distance walked in 6 minutes improved by 148 m (95% CI, 4.5 to 282 m; P = 0.048). Of the 15 patients who continued to use inhaled iloprost, 8 stopped: Four had lung transplantation, 1 switched to intravenous prostacyclin therapy, and 3 died. Seven patients are still receiving inhaled iloprost (mean +/-SD) duration of therapy, 536 +/- 309 days; mean dosage, 164 +/- 38 microg/d).

CONCLUSIONS

Inhaled iloprost may offer a new therapeutic option for improvement of hemodynamics and physical function in patients with life-threatening pulmonary hypertension and progressive right-heart failure that is refractory to conventional therapy.

Systemic sclerosis-associated pulmonary hypertension: short- and long-term effects of epoprostenol (prostacyclin)

OBJECTIVE

To evaluate the short- and long-term effects of intravenous epoprostenol in patients with pulmonary hypertension (PH) associated with systemic sclerosis (SSc).

METHODS

Sixteen patients with SSc-associated PH and New York Heart Association (NYHA) class III or IV symptomatology underwent right heart catheterization for determination of baseline hemodynamic values. Vasoreactivity was assessed with either inhaled nitric oxide or intravenous adenosine. After a medication washout period, all patients received intravenous epoprostenol in incrementally increasing doses; tolerance was assessed according to symptoms and hemodynamic findings at each dose increment and at the conclusion of the medication trial. Once a stable medication regimen was established, patients were discharged and followed up as outpatients for assessment of symptoms and exercise tolerance as measured by change in the NYHA class. Repeat hemodynamic testing was performed in 4 patients at 1 year and in 2 patients at 2 years of treatment.

RESULTS

Therapeutic response to epoprostenol, defined by a reduction in the pulmonary vascular resistance of > or =25%, was achieved in the short-term treatment period in 13 of 16 patients (81.3%). Improvement in symptoms and exercise tolerance occurred in all patients, and a significant short-term hemodynamic response was observed. Followup hemodynamic tests revealed persistent favorable responses in all 4 of the patients studied.

CONCLUSION

Most patients with PH secondary to SSc manifest favorable hemodynamic responses to epoprostenol in the short term. Long-term epoprostenol was generally well tolerated and provides a potential therapeutic option for patients with PH secondary to SSc.

Inhaled prostacyclin and iloprost in severe pulmonary hypertension secondary to lung fibrosis

Pulmonary hypertension is a life-threatening complication of lung fibrosis. Vasodilator therapy is difficult owing to systemic side effects and pulmonary ventilation-perfusion mismatch. We compared the effects of intravenous prostacyclin and inhaled NO and aerosolized prostacyclin in randomized order and, in addition, tested for effects of oxygen and systemic calcium antagonists (CAAs) in eight patients with lung fibrosis and pulmonary hypertension. Aerosolized prostaglandin (PG)I(2) caused preferential pulmonary vasodilatation with a decrease in mean pulmonary arterial pressure from 44.1 +/- 4.2 to 31.6 +/- 3.1 mm Hg, and pulmonary vascular resistance (RL) from 810 +/- 226 to 386 +/- 69 dyn. s. cm(-)(5) (p < 0.05, respectively). Systemic arterial pressure, arterial oxygen saturation, and pulmonary right-to-left shunt flow, measured by multiple inert gas analysis, were not significantly changed. Inhaled NO similarly resulted in selective pulmonary vasodilatation, with RL decreasing from 726 +/- 217 to 458 +/- 81 dyn. s. cm(-)(5). In contrast, both intravenous PGI(2) and CAAs were not pulmonary selective, resulting in a significant drop in arterial pressure. In addition, PGI(2) infusion caused a marked increase in shunt flow. Long-term therapy with aerosolized iloprost (long-acting PGI(2) analog) resulted in unequivocal clinical improvement from a state of immobilization and severe resting dyspnea in a patient with decompensated right heart failure. We concluded that, in pulmonary hypertension secondary to lung fibrosis, aerosolization of PGI(2) or iloprost causes marked pulmonary vasodilatation with maintenance of gas exchange and systemic arterial pressure. Long-term therapy with inhaled iloprost may be life saving in decompensated right heart failure from pulmonary hypertension secondary to lung fibrosis.

Acute effects of nebulised epoprostenol in pulmonary hypertension due to systemic sclerosis

Pulmonary hypertension often has a lethal outcome in systemic sclerosis and the treatment is challenging. Epoprostenol is a potent pulmonary vasodilator and its efficacy has been demonstrated when delivered by the intravenous and aerosolized routes. We report the haemodynamic and functional benefits of epoprostenol administered by inhalation to a spontaneously breathing patient with partially reversible pulmonary hypertension due to systemic sclerosis. Aerosolized epoprostenol, equivalent to the maximum tolerated intravenous dose (31.2 micrograms), produced a 58% fall in pulmonary vascular resistance, increased the cardiac output by 42% and improved functional performance by one MET (3.5 ml kg-1 min-1 of oxygen uptake) without any significant side-effects. Selective distribution of epoprostenol by the inhaled route may offer a new strategy for treatment of pulmonary hypertension.

[Pathology of diseases of extracardiac origin. VI. Disease of the connective tissue and heart]

Connective tissue diseases encompass a wide group of nosologic entities of unknown etiology, characterized by multisystemic organ involvement, sharing an immunologic pathogenetic mechanism, producing a variety of inflammatory manifestations, and whose primary lesion is always a diffuse vasculitis. Any part of the cardiovascular system may be involved, including the pericardium, the myocardium, the endocardium and valves, the coronary arteries, the aorta, the pulmonary vasculature, the peripheral arteries, veins, arterioles, venules, and the capillary beds of almost every organ subsystem. Pathologic studies disclose a high prevalence of heart involvement, but the presence and extent of pathologic findings correlate poorly with clinical manifestations. With the advent of echocardiography-Doppler, milder and earlier cases are now recognized. Although these patients continue under the care of rheumatologists and internists, when cardiac involvement arises, cardiologists must be aware of the characteristics, outcome and management of connective tissue diseases.

Vascular abnormalities in scleroderma

Vascular abnormalities represent a fundamental event in the pathogenesis of systemic sclerosis. This review focuses on key observations that support this view and builds a framework with which to clarify our understanding of how endothelial cell damage may trigger a self-fueling process ending in pathological tissue fibrosis in those susceptible to scleroderma. The studies reviewed in this article pertain to systemic sclerosis patients.

The in vitro pulmonary vascular effects of FK409 (nitric oxide donor): a study in normotensive and pulmonary hypertensive rats

1. Vasorelaxant responses to the nitric oxide (NO) donor, FK409 ((+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide ), were evaluated on precontracted isolated ring preparations of main pulmonary artery and intralobar pulmonary artery from rats. 2. On main pulmonary artery FK409 fully reversed the precontractions. Responses were inhibited by methylene blue but were independent of the endothelium. The potency (-log EC50) of FK409 was the same on preparations contracted with noradrenaline (7.62) or the thromboxane-mimetic, U44619 (7.63). 3. On intralobar pulmonary artery FK409 caused only 80% reversal of the precontraction and was 2 fold less potent than on main pulmonary artery. These differences in maximum response and potency between main and intralobar arteries are in keeping with previous findings with other NO donors. 4. Pulmonary hypertension was induced in rats by chronic exposure to hypoxia (10% O2) for 1 or 4 weeks. Main pulmonary arteries from 1 week hypoxic rats had inherent tone and showed spontaneous contractile activity. In these arteries FK409 reversed not only the precontraction induced by noradrenaline but also the inherent tone. However, FK409 was 17 fold less potent than in control arteries, reflecting previous findings with other NO donors. Main pulmonary arteries from 4 week hypoxic rats had minimal inherent tone and were quiescent and FK409 was 4.5 fold less potent than in control arteries. In intralobar pulmonary arteries from 4 week hypoxic rats FK409 was 12 fold less potent than in controls. 5. Treatment of arteries with either (a) in vitro hypoxic conditions (PO2 of solution in organ bath < 10 mmHg) or (b) superoxide dismutase (SOD; 150 u ml-1) together with catalase (1200 u ml-1) significantly increased the potency of FK409 in preparations from hypoxic rats but had no effect on the potency in control preparations. Neither SOD nor catalase, alone, nor the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester, had any effect on the potency of FK409 in preparations from control or hypoxic rats. 6. It is concluded that the reduction in potency of FK409 seen in pulmonary arteries from rats with chronic hypoxic pulmonary hypertension may be due in part to the presence of one or more reactive oxygen species (either hydroxyl or superoxide plus hydrogen peroxide).