Several treatments have been developed for pulmonary arterial hypertension (PAH) over the last two decades, with post-market studies reporting an improvement in the prognosis and progression of PAH with their use. However, reported survival rates have been unsatisfactory in western countries with respect current PAH therapies, while no reliable data on their effectiveness has been reported in the Asia Pac rim. Due to the lack of data, Matsubara et al., conducted a retrospective study with Japanese patients with idiopathic pulmonary arterial hypertension/heritable pulmonary arterial hypertension (I/HPAH).
Fifty-six patients at the National Hospital Organization Okayama Medical Center, diagnosed between 1998 and 2012, were selected as participants. The average age of diagnosis was 32 years, with a survival rate of 96% of the patients 5 years after diagnosis, and a 78% survival rate 10 years after diagnosis. The mean survival period from the time of diagnosis while undergoing PAH treatment was 14.9 years.
Among these treated patients, 93% received prostacyclin analogs, 68% endothelia receptor antagonists, and 52% phosphodiesterase type 5 inhibitors. Overall, 75% of the patients were treated with some form of combination therapy.
After 3.7 years of follow-up, a significant improvement in haemodynamic parameters among the Japanese PAH participants was observed. A cardiac index raised from 2.3 to 3.5 L/min per m2, while the mean pulmonary arterial pressure decreased an average of 28 mmHg. The right arterial pressure was reduced from 8 to 5 mmHg, a brain natriuretic peptide improved 67 pg/mL and the 6-minute walk distance increased in 144m.
To avoid other variables, several analyses of baseline variables were assessed. It was found that survival was not predicted by age, gender, hereditary status, or PAH treatment. On the other hand, the BNP level appeared to have a direct effect in the prognosis, while SpO2 values are related with worse survival rates.
This study highlighted several aspects of PAH treatment. First off, the total survival rate was higher than the previously reported for western patients. The authors commented that “there might be a difference in the genetic background between Asians and Caucasians that leads to a different response to treatment.” However, there was a difference in the prognosis with respect to the Chinese patients studied, however, the discrepancy between Chinese and Japanese outcomes is believed a result of a disproportionate percentage of Chinese patients having decided to take inexpensive, generic drugs or discontinue their treatment.
While no formal link between the efficacy of Pulmonary Arterial Hypertension therapies and Japanese PAH patients has been found, this study could lead to future studies on what subtle genetic and/or behavioral factors in Japanese patients facilitate improved outcomes when treated with PAH drugs, which could in turn inform future drug development for the entire Pulmonary Arterial Hypertension patient population.