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Idiopathic pulmonary arterial hypertension (IPAH) represents pulmonary arterial hypertension in its purest form. By definition, IPAH exists when an underlying cause of the pulmonary arterial hypertension (PAH) cannot be identified. It is a rare disease with a poor prognosis and is characterized by luminal obliteration of small pulmonary arteries. The overall result is increased resistance to pulmonary blood flow, increasing pulmonary artery pressure (PAP), and ultimately, right ventricular failure and death.
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Women are affected more commonly than men, with a female-to-male ratio of approximately 1.7:1. Cruelly, there is a predilection for IPAH to affect otherwise normal young women of childbearing age. The mean age for developing the condition is approximately 40 years, but it can occur at any age. Elderly patients often have other coexisting cardiac and respiratory disease, making the diagnosis of pure IPAH more challenging.
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Most patients with IPAH present with exertional dyspnea, developing over months or years. This classical, although nonspecific, symptom is thought to be due to the inability of the right heart to raise output on exertion. Chest pain, syncope, and peripheral edema are more common in advanced IPAH and indicate right ventricular failure.1,2
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The clinical signs of IPAH include right ventricular heave, loud pulmonary component of the second heart sound, a pansystolic murmur of tricuspid regurgitation, and a right ventricular third sound. Jugular venous distension, hepatomegaly, peripheral edema, ascites, and cold extremities indicate patients in a more advanced state with right ventricular failure at rest. Central cyanosis may also be present in advanced cases.
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Unfortunately, the absence of findings on clinical examination and nonspecific symptoms frequently lead to a delay in referral to the appropriate specialist center and, subsequently, a delay in diagnosis and treatment. Symptoms are often initially attributed to poor physical fitness, especially in overweight patients, and the diagnosis only becomes apparent with the development of chest pain, syncope, or edema.
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The chest radiograph may give the first clue to the presence of IPAH, providing invaluable information on the heart size, the lung parenchyma, and the pulmonary vasculature.
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The main chest radiograph features of IPAH consist of enlargement of the main pulmonary arteries and rapid tapering of the vessels as they extend to the periphery of the lungs, giving rise to peripheral oligemia. The heart, particularly the right-sided chamber, is usually enlarged but may be of normal size (Fig. 24–1).
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Ventilation/Perfusion Scan
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