Pulmonary hypertension (PH) has been reported to be associated with myeloproliferative neoplasms (MPN) in 5% to 48% of MPN patients—a large variability likely related to the small cohorts of patients previously studied. Based on these earlier studies, both the European Society of Cardiology (ESC) and the European Respiratory Society recognized MPN as a specific cause of PH of unclear and/or multifactorial mechanisms. Now, authors of the largest PH study in patients with Philadelphia chromosome-negative MPN (Ph-MPN) have concluded that the prevalence of PH is lower (3.8%) than has been previously reported.
Several risk factors have been identified for developing PH among patients with Ph-MPN: obstruction of pulmonary vessels by circulating megakaryocytes, smooth muscle hyperplasia due to platelet-derived growth factor, and altered angiogenic status. There is an increased risk for thromboembolic events, and thus a high risk of pulmonary embolism leading to PH. Extramedullary hematopoiesis, a well-known complication of progressive massive fibrosis that involves the presence of circulating marrow progenitors in the lung parenchyma, may also cause PH.
The current prospective, observational cohort study, from March 2015 through June 2016, followed 158 patients with Ph-MPN (median age, 65 years; 50.6% were female; all were white; and the median duration of Ph-MPN at inclusion was 4 years). About half the subjects had polycythemia vera (PV), 34% had essential thrombocytosis (ET), 11% had primary myelofibrosis, 3% had post-ET myelofibrosis, and 2% had post-PV myelofibrosis. Transthoracic echocardiography (TTE) was performed on all 158 patients included in the study. When TTE results were abnormal, further investigations were performed according to current ESC guidelines. The primary study endpoint was the frequency of PH; the secondary endpoint was cause of PH. Once the etiology behind PH was established, no further tests were performed as part of the study.