Stalock had been sidelined all season with what the Minnesota Wild classified as an upper-body injury before being claimed by the Oilers on waivers Monday.
Stalock said he showed no symptoms and returned multiple negative tests, but team doctors told him last year he was positive. He underwent examinations that revealed myocarditis, which is an inflammation of the heart muscle and can lead to cardiac arrest. He was told to rest for six weeks.
"Those first couple weeks were scary," Stalock said. "You go on the internet and read stuff and you're like, 'Holy shit.'
"I was completely asymptomatic, but they think because I had no symptoms and had it in my system that because it was right at the time where we were ramping things up with skating and working out and ramping up for the season that my heart was working and working and working and started to get stressed and swell because of the virus in my system."
Stalock continued: "It was mentally draining and very frustrating. Every doctor you talk to, they’re like, 'This is so new, we don’t know what can happen.' And you're like, 'Well, that doesn’t help.'"
Stalock visited a specialist in Boston in mid-January and was given clearance to begin working out again.
Stalock will have to quarantine for two weeks before being eligible to suit up with the Oilers. The 33-year-old owns a .909 save percentage in 151 career appearances.