Sen. Bernie Sanders Bernie SandersMcConnell accuses Democrats of sowing division by 'downplaying progress' on election security The Hill's Campaign Report: Arizona shifts towards Biden | Biden prepares for drive-in town hall | New Biden ad targets Latino voters Why Democrats must confront extreme left wing incitement to violence MORE (I-Vt.), a leading Democratic presidential candidate who suffered a heart attack last year, said Sunday his campaign has released the "substantive" part of his medical records.

"We have released as much documentation as any other candidate," Sanders said on NBC's "Meet the Press," when questioned on the release of his records.

"No other candidates had a heart attack," NBC's Chuck Todd Charles (Chuck) David ToddSunday shows - Trump team defends coronavirus response Strzok: 'I continue to believe that Donald Trump is compromised by the Russians' GOP chair defends Trump messaging on masks: 'To say that he should have known then what we know now isn't really fair' MORE followed up, noting Sanders pledged in September to release his records before a vote was cast. He made the pledge about a month before his heart attack.

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"No other candidate is doing four of five events a day, running all over this country," Sanders responded.

"You can start releasing medical records and it never ends," Sanders added. "We have released the substantive part of all our medical records, we have doctors who are, cardiologists who are, confirming I am in good health. I am in good health."

Todd asked Sanders what changes he's made that his doctors suggested since his heart attack.

Sanders said he is trying to "walk a bit more," but his schedule doesn't always allow it. He is also trying to sleep "a little better."

"I'm feeling great," he said.

Sanders released three letters from his doctors at the end of December declaring him healthy.

The letters were released after the 78-year-old candidate briefly left the trail in October after suffering a heart attack and undergoing a procedure to receive stents.