The uncertainty stems from how Fetterman’s campaign and his wife, Gisele, have characterized his heart condition: a common, irregular rhythm called atrial fibrillation (A-fib). They said the A-fib led to his May 13 stroke, and that is indeed a common cause of stroke. But when he got the defibrillator four days later, they said the device was implanted to treat the A-fib.

But that’s not what defibrillators are for, leading cardiologists not involved in his care to suggest that Fetterman, 52, has another heart condition the campaign hasn’t disclosed.

“It doesn’t make sense,” Anthony Pearson, a St. Louis-based cardiologist who writes The Skeptical Cardiologist blog, said of the campaign’s account of Fetterman’s health…

While stressing that they have no direct knowledge of Fetterman’s medical situation, Cooper and Pearson said a defibrillator would never be implanted unless a patient had another condition besides A-fib.

That could mean some underlying heart condition was resulting in both A-fib and an increased risk of sudden cardiac arrest. Or it could mean the A-fib had been going on for a long time, leading to a weakened heart muscle that would necessitate the use of a defibrillator.