Recently, targeted therapy has been developed for idiopathic pulmonary arterial hypertension (IPAH). Studies evaluating the prognosis of IPAH have been conducted in adults. However, there is no nationwide survey of pediatric patients with IPAH regarding the long-term prognosis in Japan. Therefore, we investigated the clinical outcomes of Japanese pediatric patients with IPAH and risk factors for a poor prognosis. This multi-center, retrospective cohort study included pediatric patients with IPAH under the age of 15 years, who were gleaned from the nationwide network of Japanese Society of Pediatric Cardiology and Cardiac Surgery (JSPCCS). The questionnaire was sent to members of JSPCCS in 2015. Patients who were diagnosed with IPAH from 1994 to 2014 were included. The primary endpoint was death or lung transplantation. Ninety-five patients were finally enrolled. Both the mean age at diagnosis and the mean follow-up duration were 7 years. Ninety-five percent of patients had received targeted therapy for IPAH during follow-up. The overall 1, 3, 5, and 10-year event free rate, estimated using Kaplan–Meier survival estimate, was 96, 91, 83, and 74%, respectively. The prognosis was significantly poorer in patients with increased right ventricular systolic pressure (RVp), mean pulmonary artery pressure (mPAP) (≥ 52 mmHg), cardiothoracic ratio (≥ 55%), and levels of B-type natriuretic peptide (BNP) during follow-up (≥ 300 pg/mL) than in those without these parameters. In conclusion, in Japanese children with IPAH, the event-free rate for death or lung transplantation was found to be good. Greater RVp, mPAP, BNP levels during follow-up, and cardiothoracic ratio may be predictive indicators for a poor prognosis.
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