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Article Summary
Idiopathic Pulmonary Fibrosis and Pulmonary Hypertension: Connecting the Dots

Nathan SD, Noble PW, Tuder RM. Am J Respir Crit Care Med. 2007;175:875-880.

Introduction:

• There is a growing interest in the role of the pulmonary vasculature in the pathogenesis and progression of idiopathic pulmonary fibrosis (IPF)
• Pulmonary hypertension (PH), a manifestation of pulmonary vascular disease, has recently been recognized as an important predictor of mortality in IPF
• This article summarizes the current state of knowledge regarding pulmonary vascular abnormalities and PH in IPF, and explores the impact of PH on morbidity and mortality in this disease

Findings:

• Pulmonary hypertension is common in IPF, with a prevalence of 32%–85%
• Predicting survival in IPF using traditional measures of disease severity has been challenging. Change in forced vital capacity is the most robust variable, but it lacks sensitivity
• The presence of PH and its functional correlate, decreased exercise capacity as measured by 6-minute walk testing, are strongly predictive of mortality in IPF
• Our current hypotheses regarding the mechanism of PH in IPF involve both pulmonary artery vasoconstriction from regional hypoxemia and pulmonary artery remodeling as a consequence of the primary fibroproliferative process
• Noninvasive identification of PH in patients with IPF is challenging. Clinical variables, pulmonary function values, echocardiography, and brain natriuretic peptide levels lack sufficient accuracy
• Although early data suggest treatment with pulmonary vasodilators may be beneficial in patients with PH and IPF, it remains unclear whether treatment improve functional status or survival

Expert Opinion:

Nathan and colleagues highlight the recent data surrounding the role of the pulmonary vasculature in patients with IPF. It remains unclear whether pulmonary vascular abnormalities are central to the pathobiology of this disease, or are secondary complications of a primarily fibroproliferative process. Regardless, it is increasingly clear that the presence of pulmonary hypertension is an important predictor of survival in patients with IPF.

How do we use this information in the care of patients with IPF? First, clinicians should be aware of the relationship between PH and survival, and incorporate this knowledge into their prognostic discussions with patients. Second, patients with suspected PH by history or physical examination should undergo right heart catheterization, as noninvasive tests lack accuracy in its diagnosis. Third, it is my belief that patients with documented PH and IPF should be considered for therapy with pulmonary vasodilator agents. This recommendation is based on biological plausibility and the lack of alternative effective therapies for this disease. Clearly this issue needs to be studied in well-designed clinical trials.

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