Co-presidents Daniel Pinto and Gordon Smith have stepped up to lead America’s biggest bank during Mr Dimon’s recovery, in addition to their current roles leading its investment bank and retail bank.

“The good news is that it was caught early and the surgery was successful. He is awake, alert and recovering well,” the duo said in a memo to colleagues, shareholders and clients on Thursday evening.

Mr Dimon, a 63-year-old non-smoker who exercises regularly, experienced chest pains on Thursday morning and went to hospital in New York, a person familiar with the situation told the Financial Times.

JPMorgan did not give any guidance on how long Mr Dimon would be away from the office. Patients typically stay in hospital for two to three days after surgery to repair aortic dissections, according to materials published by NYU Langone Health. Recovery times at home can vary.

An influential voice on everything from healthcare to politics, and once touted as a potential candidate for the US presidency, Mr Dimon is one of Wall Street’s best-known figures and its longest-serving chief executive.

During his fifteen years at the helm, JPMorgan emerged as dominant player in the post-financial crisis era, culminating in last year’s profits which set a global record for the most earned by a bank in a single year.

Mr Dimon promised more of the same when he hosted the bank’s annual investor day in New York just last week, pointing to opportunities to grow in new geographic markets and digital channels.

“The bottom line is that Mr. Dimon is often viewed as a steady hand for the banking industry during turbulent times (like we are in now), so not having him at the helm of JPM is a modest negative,” Brian Kleinhanzl, analyst at KBW wrote in a note to clients.

He added, however, that Mr Smith and Mr Gordon have “deep experience at JPM and have run JPM’s largest segments, so we believe there will not be a near-term impact from the medical issues that arose today”.

JPMorgan shares slid a further 1.5 per cent to $112.66 in after-market trading on Thursday, having slumped almost 5 per cent during the day as the banking sector was hit by earnings fears.

In their note to clients, Mr Pinto and Mr Smith said this is “a time for all of us to stay focused on our important responsibilities”. JPMorgan’s lead director Lee Raymond said the bank had “exceptional leaders across our businesses and functions - led by our outstanding CEO and co-presidents”.

“Our company will move forward together with confidence as we continue to serve our customers, clients, communities and shareholders,” Mr Raymond added.

Mr Dimon was treated for throat cancer in 2014 and was given the all clear at the end of that year.

In 2018, the banker said he would continue to lead JPMorgan for “approximately five more years”. He revised this in January, however, telling journalists: “My statement stays the same, it’s five years. When and if we ever set an actual retirement date, we’ll let you know.”

Mr Pinto and Mr Gordon are seen as the most likely successors should Mr Dimon step down more immediately. Over a longer horizon, Marianne Lake, the former chief financial officer and head of consumer lending, is seen as a strong contender, along with Jenn Piepszak, the current chief financial officer.