A senior cardiologist says Democratic presidential frontrunner Bernie Sanders should release a single measure of his heart performance to dispel concerns about his health.

Mr Sanders has been facing demands to release his medical records since he suffered a heart attack in October 2019. He initially said he would offer up his full records, but has since said that no more will be released.

Richard Kovacs, president of the American College of Cardiology, told NBC news that to address the question of his heart, Mr Sanders should release the results of a single test: the left ventricular ejection fraction, which measures the volume of blood the heart pushes out when it contracts.

Mr Kovacs said that this measure is routinely used to guide therapy for patients who have experienced heart events, and that it would give a good indication of the progress of Mr Sanders’s recovery.

Mr Sanders said last autumn that releasing medical records was “the right thing to do” and that “the American people have a right to know” whether candidates are in good health.

In pictures: Bernie Sanders celebrates Nevada caucus win Show all 5 1 /5 In pictures: Bernie Sanders celebrates Nevada caucus win In pictures: Bernie Sanders celebrates Nevada caucus win Bernie Sanders and his wife Jane, triumphant at hearing of Nevada Caucus win. in San Antonio Texas on 22 February 2020 Reuters In pictures: Bernie Sanders celebrates Nevada caucus win Bernie Sanders embraces his wife Jane at rally in San Antonio Texas on 22 February 2020 REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win U.S. Democratic presidential candidate Senator Bernie Sanders celebrates with his wife Jane after being declared the winner of the Nevada Caucus as he holds a campaign rally in San Antonio, Texas, U.S., February 22, 2020. REUTERS/Callaghan O'hare REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win Bernie support raises sign and a thumbs-up to the news of Senator Sanders' win REUTERS In pictures: Bernie Sanders celebrates Nevada caucus win Bernie supporter cheer at the news of Sanders' win REUTERS

However, in a more recent interview with NBC, Mr Sanders said that he had released as much medical information “as any other candidate” and that more would not be forthcoming.

“You can start releasing medical records and it never ends,” he said.

Mr Sanders suffered his heart attack while campaigning in Nevada. He spent two-and-a-half days in hospital and had two stents placed in an artery; afterwards, he said he would scale back his travel and event schedule.

Mr Sanders isn’t the only septuagenarian politician whose health has been questioned. Donald Trump has also previously been diagnosed with heart problems, and his junk food-rich diet has drawn criticism and concern.

And during the 2016 presidential campaign, Hillary Clinton’s health became the subject of numerous conspiracy theories, including one that she had Parkinson’s disease and another that she had died and been replaced with a body double.

Those baseless theories were amplified by a genuine incident where Ms Clinton apparently fainted while leaving an event.