Pulmonary arterial hypertension (PAH) is a disorder characterized by progressive elevation of pulmonary artery pressure (PAP) and vascular resistance in the absence of left-sided cardiac disease, pulmonary vein compression, respiratory disorders, or thromboembolic disease. It is defined by a mean PAP over 25 mmHg at rest or over 30 mmHg with exercise and a pulmonary artery occlusion pressure (PAOP) of less than 15 mmHg. PAH is associated with a poor prognosis. The estimated median survival from diagnosis is 2.8 years and the 1-year and 5-year survival rates are only 68% and 34%, respectively. 1,2 More than 70% of PAH patients will die as a result of right ventricular failure and most of the remainder from dysrhythmia. Predictors of a poor prognosis in PAH are related to the development of right ventricular failure. 1,3,4 The objectives of this review are to examine the pathophysiologic mechanisms leading to the development of right ventricular failure due to PAH, the diagnostic features of right ventricular failure, and the management of chronic right ventricular failure with emphasis on acute decompensation in this setting. Pathophysiology Clinical Manifestations and Hemodynamic DerangementsThe normal right ventricle is a thin-walled (less than 0.6 cm), trabeculated, roughly triangular structure that weighs less than 65 g in men and less than 50 g in women. 5,6 It is designed to empty its volume into a low-impedance, highcapacitance, pulmonary circulation by contracting sequentially from inflow to outflow. The pulmonary circulation can tolerate three-to fourfold increases in right-sided cardiac output without significant increases in PAP. In healthy individuals, pulmonary vascular resistance (PVR) decreases as the cardiac output rises with exercise. 7 In the setting of PAH, PVR does not sufficiently decrease with exercise, resulting in dyspnea and poor exercise capacity.Progressive PAH presents a pressure overload state to the right ventricle, increasing right ventricular workload leading to concentric hypertrophy (Figure 1). The right ventricle compensates: the walls hypertrophy while maintaining a normal or smaller chamber size, resulting in normal or reduced right ventricular wall stress. During this compensated phase of adaptive hypertrophy and normal to reduced wall stress, the ventricle is able to eject blood against the high PVR while maintaining an adequate right-sided cardiac output and normal right atrial pressure. During this phase patients exhibit few symptoms.The right ventricle can compensate only so long, initiating the symptomatic/declining phase (Figure 1). During this phase, with marked, maladaptive right ventricular hypertrophy and variable degrees of interstitial fibrosis, diastolic function may be impaired, altering the right ventricular diastolic pressure-volume relationship and leading to increases in right ventricular end-diastolic and right atrial pressures. With persistent pressure overload, the right ventricle undergoes a remodeling process eventually leading to right ventricular failu...
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