From the article:
Researchers at the Intermountain Medical Center Heart Institute in Murray, Utah, which is the flagship facility for the Intermountain Healthcare system, studied 5,695 men between the ages of 53 and 71. The men, all patients at Intermountain Healthcare hospitals, had initial low testosterone levels.
Researchers found that men who received testosterone supplementation to achieve normal or high testosterone levels had reduced overall rates of major adverse cardiac events at one and three years after their initial low levels of testosterone were measured, compared to other men who had persistently low levels of testosterone. The lower rate of cardiac events included a reduction in the adjusted risk of death and a reduction in heart attacks.
[…]
Smaller studies have been conducted on testosterone replacement therapy and its cardiovascular effects in men, with different results. While it is known that low levels of testosterone pose an increased cardiovascular risk, the risks versus benefits of supplementation have not been clearly identified.