according to definition.

according to definition, the clinical diagnosis of primary pulmonary hypertension (PPH) can be made barely after any secondary cause of pulmonary hypertension is rul gone out In the past, pathologic confirmation of the clinical diagnosis was based forward demonstrating the presence of the so-called plexogenic pulmonary arteriopathy in the absence of any congenital cardiac left-to-right switch It is now recognized that there are no specific histopathologic lesions of PPH and that the diagnosis of this disease requires the shut up integration of clinical symptoms, laboratory investigations, and histopathologic findings. The end of this presentation was to describe the models of histopathologic lesions that can bring forward PPH.

HISTOPATHOLOGIC CLASSIFICATION OF PPH

Table 1 summarizes the outcomes of five large pathology series published during the past 20 years. The great majority of patients with PPH had widespread abnormalities single in the arterial side of the pulmonary circulation at autopsy or lung biopsy and were classified as having pulmonary hypertensive arteriopathy. In a small percentage of cases, the hypertensive changes did involve primarily the venous pulmonary circulation, and the patients were classified as having pulmonary veno-occlusive disease. In about cases, the diagnosis of PPH could not be confirmed histopathologically.

Hypertensive Pulmonary Arteriopathy

Hypertensive pulmonary arteriopathy associated with PPH is a disease of the muscular arteries and arterioles; the elastic arteries point out to secondary changes in the form of dilatation, medial degeneration, and intimal atheromas. Three histopathologic subset of hypertensive pulmonary arteriopathy have been identified forward the basis of the predominant vascular lesion:[1,2] isolated medial hypertrophy (IMH), plexogenic pulmonary arteriopathy (PPA), and thrombotic pulmonary arteriopathy (TPA). Although it is uncertain whether these subset exhibit different pathogenetic mechanisms or different manifestations of the same disease, the distinction is important since it provides an objective basis for evaluating the events of various therapeutic protocols in PPH

IMH--Pulmonary Artery Medial Hypertrophy: Medial hypertrophy is existing in all forms of pulmonary hypertension either as an isolated lesion (IMH) or associated with intimal and/or luminal lesions. a certain number of authors[3,4] have considered IMH an early stage of progressive growth of PPA. Because IMH is a potentially reversible lesion amenable to pharmacologic manipulations, and its progression to classic plexogenic arteriopathy in PPH has not been demonstrated,[1,2] it is preferable to separate the real form of IMH from the classic PPA, in which irreversible vascular lesions predominate. When strict criteria for diagnosis of IMH are applied,[1,2] its incidence among adolescents and adults with PPH is between 2 and 4 percent (Table 1)

Isolated medial hypertrophy is characterized by the agency of an increased thickness of the medial soft muscle and duplication of elastic laminae (Fig 1a [top]) in muscular arteries as well as the disentanglement of a well-formed smooth muscle layer (muscularization) in arterioles (Fig 1b [bottom]). With long-standing disease, the medial sleek muscle may degenerate and be replaced according to fibrous tissue. Whether or not muscle atrophy accounts for failure of certain PPH patients to accord to vasodilators[5] remains to be determined.

[TABULAR DATA OMITTED]

PPA--Plexogenic Pulmonary Arteriopathy: In the absence of congenital heart diseases with left-to-right switchs PPA was considered the underlying pathologic condition of PPH and was characterized by dint of the presence of the plexiform lesions.[3,4] It is now recognized that PPA and plexiform lesions can come to one's mind in pulmonary hypertension secondary to the use of certain appetite suppressants,[6,7] denatured rapeseed oil,[8] and in a certain patients with HIV infection.[9,10] Nevertheless, PPA remains the in the greatest degree common type of pulmonary hypertensive arteriopathy in PPH patients, accounting for about 50 percent of the cases (Table 1) In the PPH-Registry experience, patients with PPA were onward average 10 years younger than patients with the other symbols of arteriopathy, had rapidly progressive disease, and 75 percent were female subjects[2] It is still unclear whether the greater incidence of PPA in young women indicates different pathogenetic mechanisms or a greater reactivity to nonspecific hypertensive stimuli.[11]

Plexogenic pulmonary arteriopathy is characterized through a variable admixture of medial hypertrophy intimal lesions, and a variety of destructive lesions involving the entire arterial wall.[1-4,12]

The intimal lesions are of three types: concentric laminar intimal fibrosis (CLIF), eccentric intimal fibrosis (EIF), and concentric nonlaminar fibrosis (CnLIF).

Concentric laminar intimal fibrosis is the greatest in quantity reliable and constant marker of PPA.[3] It is characterized at concentric, onionskin-like layers of proliferated myofibroblasts and elastic fibers separated by the agency of a variable amount of proteoglycan-rich matrix (Fig 2) Eccentric intimal fibrosis is characterized by dint of cushionlike eccentric patches of intimal fibrosis (Fig 3a [top]), whereas CnLIF is compos of circumferential intimal fibrosis (Fig 3b [bottom]). the one and the other EIF and CnLIF are generally considered the spring of the mural organization of thrombi or emboli and are instant in variable proportion in the couple PPA and TPA[2,7,11,12] (see below).

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