Obesity, Metabolic Syndrome, and Pulmonary Hypertension

Pulmonary hypertension may be caused by many different conditions, classified broadly into five categories by the World Symposium on Pulmonary Hypertension. The primary determinants of pulmonary vascular pressure are left atrial pressure, pulmonary vascular resistance, and flow through the pulmonary circulation. In this chapter, the effects of obesity on each of these components are considered. Currently, there is ample evidence that obesity and its attendant systemic diseases play a role in increasing left atrial pressure and may affect flow through the pulmonary vasculature. Hypoxia is a potent pulmonary vasoconstrictor, and increased pulmonary vascular resistance is well described in patients with hypoxemia associated with sleep-disordered breathing or obesity hypoventilation. There is also a growing body of literature that adipose tissue cytokines such as adiponectin, and insulin resistance associated with obesity, may contribute to the development of primary pulmonary vascular diseases such as pulmonary arterial hypertension. In addition to examining the role obesity plays in pulmonary vascular disease etiology, this chapter will review the difficulty that obesity poses to accurately diagnosing and treating pulmonary hypertension.