RESULTS	The distance walked in six minutes increased from baseline in all sildenafil groups ; the mean placebo-corrected treatment effects were 45 m ( +13.0 percent ) , 46 m ( +13.3 percent ) , and 50 m ( +14.7 percent ) for 20 , 40 , and 80 mg of sildenafil , respectively ( P < 0.001 for all comparisons ) .\