Medical specialists asked questions about Mr. Fetterman’s treatment with a defibrillator. They say it would make sense only if he has a different condition that puts him at risk of sudden death, like cardiomyopathy — a weakened heart muscle. Such a heart condition may have caused the blood clot. Or, the doctors say the campaign could be correct about afib causing the clot…

Dr. Lee Schwamm, a stroke specialist at Massachusetts General Hospital and professor of neurology at Harvard Medical School, said doctors do a thrombectomy only when a large artery in the brain is blocked.

“You typically wouldn’t do it for someone with just a little bit of facial droop,” he said. Dr. Schwamm wondered if the doctors who examined Mr. Fetterman in the hospital had noticed other symptoms, like a loss of vision on his left side or lack of awareness of his left side, often called “neglect.”

“These strokes tend to be very severe,” Dr. Schwamm said. “He is fortunate that he went to a hospital that could treat it.”…

Dr. Wan was less sanguine than Dr. Deo about Mr. Fetterman.

“He is at risk for sudden cardiac death,” she said. “For someone on the campaign trail that might raise concerns.”