Well, yeah, but so do all elite athletes. It's called "athlete's heart." As you exercise, your HR drops, but your heart gets bigger/stronger. Indurain's 28 beats would move about the same amount of blood as Patriot's 60. The difference is when it's pumping along at full speed. If Patriot does 200 BPM and Indurain does 200 BPM, Indruain's (theoretically) pumping twice as much blood, since his heart has twice the capacity.

Indurain was a freak because of his 8 L lung capacity.