Response to letter from dr Altmayer regarding publication "Sequential treatment with sildenafil and riociguat in patients with persistent or inoperable chronic thromboembolic pulmonary hypertension improves functional class and pulmonary hemodynamics". (1st February 2019) - Darocha, Szymon; Banaszkiewicz, Marta; Pietrasik, Arkadiusz; Piłka, Michał; Florczyk, Michał; Wieteska, Maria; Dobosiewicz, Anna; Szmit, Sebastian; Torbicki, Adam; Kurzyna, Marcin