Pulmonary hypertension in patients with Philadelphia-negative myeloproliferative neoplasms: a single-center retrospective analysis of 225 patients

Clinical Phenotype and Outcomes of Pulmonary Hypertension Associated with Myeloproliferative Neoplasms: A Population-based Study

Rationale: Precapillary pulmonary hypertension (PH) is a rare and largely unrecognized complication of myeloproliferative neoplasms (MPNs), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (MF). Objectives: To describe characteristics and outcomes of MPN-associated PH. Methods: We report clinical, functional, and hemodynamic characteristics, classification, and outcomes of patients with PV, ET, or primary MF in the French PH registry. Measurements and Main Results: Ninety patients with MPN (42 PV, 35 ET, 13 primary MF) presented with precapillary PH with severe hemodynamic impairment, with a median mean pulmonary arterial pressure and pulmonary vascular resistance of 42 mm Hg and 6.7 Wood units, respectively, and impaired clinical conditions, with 71% in New York Heart Association functional classes III/IV and having a median 6-minute-walk distance of 310 m. Half of the patients were diagnosed with chronic thromboembolic PH (CTEPH); the other half were considered to have group 5 PH. MF was preferentially associated with group 5 PH, whereas PV and ET were generally related to CTEPH. Proximal lesions were diagnosed in half of the patients with CTEPH. Thromboendarterectomy was performed in 18 selected patients with high risk of complications (5 early deaths). Overall survival at 1, 3, and 5 years was 67%, 50%, and 34% in group 5 PH and 81%, 66%, and 42% in CTEPH, respectively. Conclusions: PH is a life-threatening condition potentially occurring in MPN. There are multiple mechanisms, with equal diagnoses of CTEPH and group 5 PH. Physicians should be aware that PH strongly affects the burden of patients with MPN, especially in group 5 PH, with unknown pathophysiological mechanisms.

Pulmonary hypertension in patients with chronic myeloid leukemia

Dasatinib, a tyrosine kinase inhibitor (TKI), induces pulmonary hypertension (PH) in patients with chronic myeloid leukemia (CML). However, information on other TKIs is limited.We retrospectively analyzed PH prevalence by reviewing transthoracic echocardiography (TTE) findings in a population of Korean CML patients treated with TKI at a single hospital between 2003 and 2020. PH was defined as a high PH probability according to the European Society of Cardiology/European Respiratory Society (ESC/ERS) guidelines.Of the 189 patients treated with TKI(s) during the study period, 112 (59.3%) underwent TTE. Among the 112 patients treated with a TKI for a median of 40.4 months (range: 1.1-167.2 months), PH was found in 12 (10.7%), most frequently in those treated with dasatinib (ie, in 3 [7.5%] of 40 of those treated with imatinib, 1 [3.1%] of 32 of those treated with nilotinib, and 8 [21.6%] of 37 of those treated with dasatinib). PH resolved in 4 (50.0%) of the 8 dasatinib-treated patients after discontinuation of the agent. One nilotinib-treated and all three imatinib-treated patients recovered from PH. In multivariate analyses, age >60 years, dasatinib treatment, and positive cardiopulmonary symptoms/signs at the time of transthoracic echocardiography were statistically significant risk factors for developing PH.These results show that PH is induced not only by dasatinib, but also by imatinib and nilotinib. Careful screening for PH during any TKI treatment may thus be warranted in patients with CML.

Myeloproliferative neoplasm-driving Calr frameshift promotes the development of pulmonary hypertension in mice

Frameshifts in the Calreticulin (CALR) exon 9 provide a recurrent driver mutation of essential thrombocythemia (ET) and primary myelofibrosis among myeloproliferative neoplasms (MPNs). Here, we generated knock-in mice with murine Calr exon 9 mimicking the human CALR mutations, using the CRISPR-Cas9 method. Knock-in mice with del10 [Calr^{del10/WT (wild−type)} mice] exhibited an ET phenotype with increases of peripheral blood (PB) platelets and leukocytes, and accumulation of megakaryocytes in bone marrow (BM), while those with ins2 (Calr^ins2/WT mice) showed a slight splenic enlargement. Phosphorylated STAT3 (pSTAT3) was upregulated in BM cells of both knock-in mice. In BM transplantation (BMT) recipients from Calr^del10/WT mice, although PB cell counts were not different from those in BMT recipients from Calr^WT/WT mice, Calr^del10/WT BM-derived macrophages exhibited elevations of pSTAT3 and Endothelin-1 levels. Strikingly, BMT recipients from Calr^del10/WT mice developed more severe pulmonary hypertension (PH)—which often arises as a comorbidity in patients with MPNs—than BMT recipients from Calr^WT/WT mice, with pulmonary arterial remodeling accompanied by an accumulation of donor-derived macrophages in response to chronic hypoxia. In conclusion, our murine model with the frameshifted murine Calr presented an ET phenotype analogous to human MPNs in molecular mechanisms and cardiovascular complications such as PH.