Time course of hypoxic right ventricular hypertrophy: protection by HO-1 overexpression. ( a ) Non-Tg mice were exposed to hypoxia (8–10% O 2 ) for 18 h, 5 days (d), or 2–3 weeks (w). Development of RVH after hypoxic exposure was determined by the RV/(LV + S) ratio as described in Materials and Methods . *, P