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Susan Harch, MBBS, BmedSc; Helen Whitford, MBBS; Catriona McLean, BSc, MBBS, MD
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Affiliations: Drs. Harch, Whitford, and Mclean are affiliated with The Alfred Hospital.

Correspondence to: Susan Harch, MBBS, BmedSc, The Alfred Hospital, Commercial Rd, Prahran, Melbourne, VIC 3181, Australia; e-mail: susanharch@gmail.com


Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).


© 2009 American College of Chest Physicians


Chest. 2009;136(4):1181-1182. doi:10.1378/chest.09-1431
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We thank Montani and colleagues for their response to our article,1 which suggested that pulmonary venoocclusive disease (PVOD) should be considered as an alternative diagnosis in patients with pulmonary arterial hypertension who do not respond to medical therapy. We recognize that the reported rate of PVOD in this study is higher than that previously documented in literature on pulmonary hypertension. This may be attributable to two factors. First, the study was performed in a selected group of patients with pulmonary hypertension who had not responded to medical therapy and for whom, consequently, an alternative diagnosis was more likely. Second, a novel stain using routine smooth muscle actin immunohistochemistry with a Verhoeff elastin counterstain allowed concurrent examination of the vessel elastic lamina and smooth muscle hypertrophy in any one vessel. In conjunction with vessel microanatomical location, this enabled accurate differentiation between arterial and venous vessels, and allowed qualitative assessment of the occlusion as smooth muscle cells or fibrous tissue proliferation within the vessel wall. Smooth muscle actin immunohistochemistry with Verhoeff elastin counterstaining may have enabled higher and more accurate detection of PVOD.

We acknowledge the limited clinical data available in the study. We agree that conclusions regarding the usefulness of high-resolution CT scanning in the diagnosis of PVOD are inherently flawed due to the limited data. We are also unable to draw accurate conclusions about the differences in the parameters of noninvasive diagnostic investigations, such as pulmonary function tests, due to the small sample sizes of PVOD and arterial only pulmonary arterial hypertension cases.

Our finding that pulmonary edema did not occur in PVOD patients who received prostanoid therapy also differs from those of previous reports. Although pulmonary edema is a possible and serious adverse effect of prostanoid therapy, these findings suggest that careful use of low-dose prostanoid analogues with slow titration may be appropriate in this pulmonary hypertension subgroup.

We agree that a noninvasive approach to the diagnosis of PVOD should be pursued if possible. However, in some cases the failure to respond to medical therapy may be the best indicator of PVOD, and in these patients early listing for lung transplantation is recommended.

Financial/nonfinancial disclosures: The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Harch S, Whitford H, McLean C. Failure of medical therapy in pulmonary arterial hypertension: is there an alternative diagnosis? Chest. 2009;135:1462-1469. [PubMed] [CrossRef]
 

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Harch S, Whitford H, McLean C. Failure of medical therapy in pulmonary arterial hypertension: is there an alternative diagnosis? Chest. 2009;135:1462-1469. [PubMed] [CrossRef]
 
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