Michael Bloomberg's campaign called on his 2020 Democratic rival Sen. Bernie Sanders, I-Vt., to release further information on his heart health, after Bloomberg's campaign made public on Thursday doctor's letters attesting that the former New York City mayor's "outstanding health" enables him to run for office.

Bloomberg's last annual health exam was on July 25 and the 78-year-old billionaire underwent an annual cardiac stress test at the Johns Hopkins Hospital, according to a letter from his internist, Dr. Stephen Sisson.

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According to test results, Bloomberg had "normal" left ventricular cavity size, function and ejection at 60-65 percent. He also had an "excellent" exercise capacity, and his doctor says he's in "great physical shape" and exercises several times a week, plays golf and maintains an active pilot's license.

Sisson also disclosed that Bloomberg takes a blood thinner, a beta-blocker and medication to control his cholesterol. He also has had small skin cancers removed and is treated for arthritis and heartburn, "both of which are well controlled."

"There are no medical concerns, present or looming, that would prevent him from serving as President of the United States," Sisson wrote.

Bloomberg and Sanders are both 78 years old and the oldest candidates in the crowded Democratic field. Closely behind them in age are former vice president Joe Biden, 77, and Sen. Elizabeth Warren, D-Mass., who is 70. Their Republican rival, President Trump, is 73 years old.

The newly released letters follow a squabble between Sanders, the Democratic front-runner for the party's nomination, and Bloomberg, the wealthiest candidate in the race who has bombarded states crucial to his success on Super Tuesday with millions of dollars worth of advertising, outspending each one of his opponents.

At the Democratic debate on Tuesday hosted in South Carolina ahead of the state's primary, Sanders attempted to deflect a question about releasing his full medical records following a heart attack he suffered in October, by pointing to Bloomberg -- who underwent a similar stent procedure as Sanders did -- over two decades ago.

"I think the one area maybe that Mayor Bloomberg and I share -- you have two stents, as well," Sanders said.

"25 years ago," Bloomberg said.

"Well, we both have two stents," Sanders said. "It's a procedure that is done about a million times a year."

"Mr. Bloomberg underwent coronary stent placement for a blocked coronary artery in 2000," Sisson's letter said. "He has not had a myocardial infarction, and cardiac stress testing has shown no evidence of damage to his heart. Heart function is normal, and exercise capacity is excellent."

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"Releasing this single scientific number about heart health could start to put to rest any concerns about Senator Sanders' secrecy about his recent heart attack," Stu Loeser, a spokesperson for Bloomberg's campaign said in a statement. "Mike Bloomberg's doctor shared Mike's number, will Senator Sanders ask his doctor to do the same?"