According to the article Viagra contains the same ingredient as Revatio, which is used to treat high blood pressure.
The article had a few errors. That was one of them, IIRC. Hypertension is the medical name for what is usually called high blood pressure. Revatio is used to treat pulmonary hypertension, i.e. in the lungs, a different malady, and more lethal, IIRC. It was in the news when the FDA warned about the diet drug combo Fen-Phen.
What gets me about ED drugs is the warning that after 4 hours they hint that you have a urologic emergency.