Solitary pulmonary hypertension

Diverse forms of pulmonary hypertension remodel the arterial tree to a high shear phenotype

Pulmonary hypertension (PH) is associated with progressive changes in arterial network complexity. An allometric model is derived that integrates diameter branching complexity between pulmonary arterioles of generation n and the main pulmonary artery (MPA) via a power-law exponent (X) in dn = dMPA2(-n/X) and the arterial area ratio β = 2(1-2/X). Our hypothesis is that diverse forms of PH demonstrate early decrements in X independent of etiology and pathogenesis, which alters the arteriolar shear stress load from a low-shear stress (X > 2, β > 1) to a high-shear stress phenotype (X < 2, β < 1). Model assessment was accomplished by comparing theoretical predictions to retrospective morphometric and hemodynamic measurements made available from a total of 221 PH-free and PH subjects diagnosed with diverse forms (World Health Organization; WHO groups I-IV) of PH: mitral stenosis, congenital heart disease, chronic obstructive pulmonary lung disease, chronic thromboembolism, idiopathic pulmonary arterial hypertension (IPAH), familial (FPAH), collagen vascular disease, and methamphetamine exposure. X was calculated from pulmonary artery pressure (PPA), cardiac output (Q) and body weight (M), utilizing an allometric power-law prediction of X relative to a PH-free state. Comparisons of X between PAH-free and PAH subjects indicates a characteristic reduction in area that elevates arteriolar shear stress, which may contribute to mechanisms of endothelial dysfunction and injury before clinically defined thresholds of pulmonary vascular resistance and PH. We conclude that the evaluation of X may be of use in identifying reversible and irreversible phases of PH in the early course of the disease process.

Endothelial and smooth muscle cell ion channels in pulmonary vasoconstriction and vascular remodeling

The pulmonary circulation is a low resistance and low pressure system. Sustained pulmonary vasoconstriction and excessive vascular remodeling often occur under pathophysiological conditions such as in patients with pulmonary hypertension. Pulmonary vasoconstriction is a consequence of smooth muscle contraction. Many factors released from the endothelium contribute to regulating pulmonary vascular tone, while the extracellular matrix in the adventitia is the major determinant of vascular wall compliance. Pulmonary vascular remodeling is characterized by adventitial and medial hypertrophy due to fibroblast and smooth muscle cell proliferation, neointimal proliferation, intimal, and plexiform lesions that obliterate the lumen, muscularization of precapillary arterioles, and in situ thrombosis. A rise in cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary artery smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction, while increased release of mitogenic factors, upregulation (or downregulation) of ion channels and transporters, and abnormalities in intracellular signaling cascades are key to the remodeling of the pulmonary vasculature. Changes in the expression, function, and regulation of ion channels in PASMC and pulmonary arterial endothelial cells play an important role in the regulation of vascular tone and development of vascular remodeling. This article will focus on describing the ion channels and transporters that are involved in the regulation of pulmonary vascular function and structure and illustrating the potential pathogenic role of ion channels and transporters in the development of pulmonary vascular disease.

Pathogenic role of store-operated and receptor-operated ca(2+) channels in pulmonary arterial hypertension

Pulmonary circulation is an important circulatory system in which the body brings in oxygen. Pulmonary arterial hypertension (PAH) is a progressive and fatal disease that predominantly affects women. Sustained pulmonary vasoconstriction, excessive pulmonary vascular remodeling, in situ thrombosis, and increased pulmonary vascular stiffness are the major causes for the elevated pulmonary vascular resistance (PVR) in patients with PAH. The elevated PVR causes an increase in afterload in the right ventricle, leading to right ventricular hypertrophy, right heart failure, and eventually death. Understanding the pathogenic mechanisms of PAH is important for developing more effective therapeutic approach for the disease. An increase in cytosolic free Ca²⁺ concentration ([Ca²⁺]_cyt) in pulmonary arterial smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction and an important stimulus for PASMC migration and proliferation which lead to pulmonary vascular wall thickening and remodeling. It is thus pertinent to define the pathogenic role of Ca²⁺ signaling in pulmonary vasoconstriction and PASMC proliferation to develop new therapies for PAH. [Ca²⁺]_cyt in PASMC is increased by Ca²⁺ influx through Ca²⁺ channels in the plasma membrane and by Ca²⁺ release or mobilization from the intracellular stores, such as sarcoplasmic reticulum (SR) or endoplasmic reticulum (ER). There are two Ca²⁺ entry pathways, voltage-dependent Ca²⁺ influx through voltage-dependent Ca²⁺ channels (VDCC) and voltage-independent Ca²⁺ influx through store-operated Ca²⁺ channels (SOC) and receptor-operated Ca²⁺ channels (ROC). This paper will focus on the potential role of VDCC, SOC, and ROC in the development and progression of sustained pulmonary vasoconstriction and excessive pulmonary vascular remodeling in PAH.

New mechanisms of pulmonary arterial hypertension: role of Ca²⁺ signaling

Pulmonary arterial hypertension (PAH) is a severe and progressive disease that usually culminates in right heart failure and death if left untreated. Although there have been substantial improvements in our understanding and significant advances in the management of this disease, there is a grim prognosis for patients in the advanced stages of PAH. A major cause of PAH is increased pulmonary vascular resistance, which results from sustained vasoconstriction, excessive pulmonary vascular remodeling, in situ thrombosis, and increased pulmonary vascular stiffness. In addition to other signal transduction pathways, Ca(2+) signaling in pulmonary artery smooth muscle cells (PASMCs) plays a central role in the development and progression of PAH because of its involvement in both vasoconstriction, through its pivotal effect of PASMC contraction, and vascular remodeling, through its stimulatory effect on PASMC proliferation. Altered expression, function, and regulation of ion channels and transporters in PASMCs contribute to an increased cytosolic Ca(2+) concentration and enhanced Ca(2+) signaling in patients with PAH. This review will focus on the potential pathogenic role of Ca(2+) mobilization, regulation, and signaling in the development and progression of PAH.

Primary pulmonary hypertension and pregnancy

Despite the preponderance of primary pulmonary hypertension (PPH) in young female subjects, documented cases of PPH in association with pregnancy are uncommon. During a 12-month period, 73 female patients with PPH were evaluated as potential recipients of a heart-lung transplant; and in six (8 percent), PPH appeared to be related to pregnancy. Histologic confirmation of the diagnosis was available in four patients, and other causes of pulmonary hypertension were excluded as far as possible in the remaining two patients.

Comparison of primary plexogenic arteriopathy in adults and children. A morphometric study in 40 patients

Pulmonary vascular changes were studied in histological sections from 15 children and 25 adults with primary plexogenic arteriopathy. The severity of medial hypertrophy and degree of vasoconstriction were measured in histological sections and there was a close correlation between these two variables in both children and adults. More advanced arterial changes, expressed as an index of pulmonary vascular disease, were more common in adults, and their severity correlated positively with the degree of medial hypertrophy. No such correlation was found in children. There were similar numbers of plexiform lesions per square centimetre in children and adults, so that the differences in the indices of pulmonary vascular disease were mainly due to the intimal changes. Concentric laminar intimal fibrosis was more severe in adults. It is suggested that intensive spastic vasoconstriction results in the development of fibrinoid necrosis and subsequently of plexiform lesions and that this may happen irrespective of the presence of severe intimal fibrosis. This suggests that children with primary plexogenic arteriopathy in whom plexiform lesions have not yet developed are more likely to respond to vasodilator treatment than are adults in whom irreversible changes associated with intimal fibrosis have developed.

Differentiation of patients with primary and thromboembolic pulmonary hypertension

Twenty-five consecutive patients with obliterative pulmonary hypertension were studied. Primary pulmonary hypertension (17 patients) or chronic thromboembolic pulmonary hypertension (eight patients) was diagnosed by pulmonary angiography or autopsy. Clinical symptoms, physical findings, chest roentgenograms, electrocardiograms, and pulmonary function studies did not differentiate the patients with primary pulmonary hypertension (PPH) from those with chronic thromboembolic pulmonary hypertension (TPH). All eight patients with TPH had a lung scan interpreted as high probability for pulmonary emboli while all 17 patients with PPH had a lung scan interpreted as normal or low probability for emboli. While there was close clinical similarity between patients with PPH and TPH, the presence of a normal or low probability lung scan excluded the diagnosis of TPH.

Severe pulmonary hypertension associated with macronodular (postnecrotic) cirrhosis and autoimmune phenomena

The clinical and pathologic findings are reported in seven consecutive patients with progressive and fatal pulmonary hypertension which was not explained by predisposing cardiac or pulmonary diseases. Pulmonary arterial lesions consisted of atherosclerosis of the elastic pulmonary arteries, and medial hypertrophy and concentric laminar fibrosis of the muscular pulmonary arteries in seven patients, plexiform lesions in six patients and necrotizing vasculitis in one patient. Pulmonary emboli were not identified. Five patients had manifestations of autoimmune disease, including laboratory abnormalities (positive antinuclear antibody, positive latex agglutination for rheumatoid factor, hypergammaglobulinemia or antimitochondrial antibody) in four, necrotizing vasculitis in one, Raynaud's phenomenon in two and clinical evidence of multisystem collagen vascular disease in two. Five patients had liver disease which developed prior to or concomitant with the onset of pulmonary hypertension. At autopsy, one patient had prominent periportal fibrosis and four had macronodular (postnecrotic) cirrhosis (active in three and inactive in one). Four of these five patients with liver disease and pulmonary hypertension had evidence of autoimmune phenomena. The findings in the seven patients suggest an association between autoimmune disease, plexogenic pulmonary hypertension and liver disease of the chronic active hepatitis-postnecrotic cirrhosis type.

KMA-Greenfield filter placement for chronic pulmonary hypertension

Over a period of four years, 23 patients had the diagnosis of chronic pulmonary hypertension made on the basis of elevated resting pulmonary arterial pressures above 30 mmHg mean. Clinical features included dyspnea (100%), previous thromboembolism (43%), congestive failure (39%), venous thrombosis (35%), syncope (30%), lung disease (22%), recent trauma (22%), hemoptysis (17%) and precordial pain (17%). Pulmonary angiograms showed embolic occlusion in all but four patients, who were considered to have primary pulmonary hypertension. KimRay-Greenfield((R)) vena caval filters were inserted in 18 patients. Three of them were in refractory shock at the time, and only the one who had successful intraluminal catheter embolectomy survived. These patients have been followed an average of 23 months with two embolic deaths, one from the right atrium and one bypassing a filter misplaced in the right iliac vein (overall mortality 22%). There has been no other known recurrent embolism, but one patient developed hematuria from the filter. The five patients who did not receive a filter have all died after intervals up to 18 months. Recurrent thromboembolism was documented in three and suspected in one patient with known embolic disease who died suddenly. Regardless of etiologic factors, pulmonary hypertension with cor pulmonale is associated with a high incidence of fatal thromboembolism. In our experience, maximal protection is afforded by long-term anticoagulation therapy and the placement of a venacaval filter.

Amniotic fluid embolism

The statement that amniotic fluid embolism is the most dangerous and untreatable condition in obstetrics appears to be true. It must be suspected in any patient who collapses or bleeds excessively during labour or the immediate post-partum period. Attempts should be made to secure a definitive diagnosis in life by examination of blood obtained from the right side of the heart and the sputum for elements of amniotic fluid. Lung scanning is a useful aid to diagnosis. The principal factors that have been implicated in the clinical syndrome of amniotic fluid embolism are anaphylaxis, vascular obstruction by particulate matter, vascular spasm due to prostaglandins and possibly some other vasoactive substances, and the possibility that all the changes could be explained by disseminated intravascular coagulation as a primary event. Further work is required to elucidate the relative contributions of these various factors. Due to the suddeness of the catastrophe and the very high mortality, haemodynamic data in humans is virtually non-existent. With improved methods of resuscitation it is to be hoped that the mortality rate will be reduced and that such data will become available. In this way it might become possible to apply the results of animal research and indicate the most effective method of treatment.

Pulmonary vascular changes in scleroderma

To determine the incidence and significance of pulmonary vascular changes in scleroderma, all necropsy reports of patients with scleroderma who died at the Massachusetts General Hospital were analyzed and correlated with clinical data. The records of 30 such patients were available. Fourteen had moderate or marked abnormalities in the pulmonary arterial tree. Nine of these 14 patients had predominantly respiratory symptoms. The arterial changes consisted pathologically of intimal and medial hyperplasia affecting pulmonary arteries of all sizes. Of the eight patients with the most severe pathologic changes in the pulmonary arteries, five had slight or no interstitial fibrosis. Three of these five patients had rapidly progressive respiratory failure and severe pulmonary hypertension leading to death. Such cases form a distinct clinicopathologic entity of malignant pulmonary hypertension in scleroderma, comparable to the better recognized entity of malignant renal hypertension in scleroderma.

Pulmonary venoocclusive disease

Pulmonary venoocclusive disease has been established as a definite clinical entity characterized by congestive cardiac failure with pulmonary arterial hypertension, chronic interstitial pulmonary edema, and normal wedge pressure on cardiac catheterization. This disease was diagnosed and confirmed in a patient during life. A review of the 32 patients reported earlier has been done in an attempt to fine possible etiological agents. Early recognition and treatment with anticoagulants, methylprednisolone, aspirin, and dipyridamole may improve the prognosis.

De subitaneis mortibus. XVII. Multifocal stenoses due to fibromuscular dysplasia of the sinus node artery

The sinus node artery was focally narrowed by fibromuscular dysplasia in two examples of sudden unexpected death reported here. Although both cases had additional histological abnormalities in the conduction system of the heart, the more striking feature was the focal fibromuscular dysplasia. These findings are discussed in relationship to a large number of similar examples of focal fibromuscular dysplastic narrowing of the sinus node artery observed in other victims of sudden unexpected death, considering some possible mechanisms for lethal electrical instability of the heart and also the possible pathogenesis of such fibromuscular dysplasia.

Regression of primary pulmonary hypertension

A girl who presented in childhood with advanced primary pulmonary hypertension and whose condition later improved is described. This is the first time to our knowledge that documented regression of the disease has been reported.

Perfusion lung scanning in obliterative pulmonary hypertension

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Thromboembolic pulmonary hypertension of unusual cause in a teenager

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Primary pulmonary hypertension of unusually long duration

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Primary pulmonary hypertension, cerebrovascular malformation, and lymphoedema feet in a family

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Primary pulmonary hypertension: familial occurrence

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