High procedure and patient success rates, combined with a low event rate and improved procedural characteristics, support further use of the hybrid algorithm for a broad community of appropriately trained CTO operators.

Phosphodiesterase Type 5 is the main factor regulating cyclic guanosine monophosphate hydrolysis and downstream signaling in human PASMCs. The antiproliferative effects of this signaling pathway may be significant in the chronic treatment of pulmonary hypertension with PDE5 inhibitors such as sildenafil.

Sildenafil added to conventional treatment reduces RV mass and improves cardiac function and exercise capacity in patients with PAH, WHO functional class III. Safety monitoring is important until more experience is obtained.