By David Benoit

Fear jolted Jamie Dimon awake in the dark morning hours of March 5.

U.S. coronavirus cases numbered only around a hundred, but markets were flashing warning signs. It was 4 a.m., and the JPMorgan Chase & Co. chief executive dialed up his top lieutenants to deliver a message that couldn't wait: The economy is in trouble.

Mr. Dimon hung up the phone and lay down on the couch to read the morning papers. He felt a rip in his chest. He sat up with a gasp and called his doctor. "Jamie, take a cab," the doctor told him. "You don't have time for an ambulance."

Hours later, Mr. Dimon was clinging to life, surgeons perched above his chest repairing a gash in the artery that delivers blood from the heart to the rest of the body.

"I knew I might not make it," Mr. Dimon told The Wall Street Journal in his first interview about the aortic tear. The CEO's near-death experience came as the U.S. economy was hurtling toward its own crisis. The twin emergencies would test JPMorgan's foundations even more severely than the 2008 financial crisis.

The bank serves half of all U.S. households and 400 of the Fortune 500. For more than a decade, a booming economy lifted JPMorgan's fortunes. The bank, in turn, supported the economy's growth, lending to millions of businesses and consumers. By March, the coronavirus was threatening to punch a hole in that system.

For Mr. Dimon, it was the ultimate test of a career-spanning obsession with what he calls the fortress balance sheet -- a capital position so strong that the bank could withstand any crisis. Had he built a fortress that could withstand this onslaught? And would the fortress hold, even without him?

Mr. Dimon recovered from his near-fatal heart injury. But for a few weeks, as the coronavirus ravaged the economy, the nation's most famous banker wasn't at the head of America's biggest bank.

The economy is getting better, too. Unemployment has improved every month since April, and vaccines have put the pandemic's end in sight. The stock market has rebounded to set new records.

Mr. Dimon, out of step with some who see those factors fueling a steady recovery, is worried. He thinks the growth is fragile.

A nationwide surge in coronavirus infections and new restrictions could lead to more layoffs, depressed spending and a fresh round of small-business failures. The bank's customer data, he said, paint a picture of an uneven recovery. The unemployed are running dangerously low on savings and cutting back on the basics; the wealthy are buying second homes and new cars.

This week's passage by Congress of a new $900 billion stimulus plan, if ultimately signed into law, will help, but it won't fix the structural defects that allowed the chasm to open up in the first place, Mr. Dimon said. That, he said, requires an aggressive policy response. Absent one, he fears, the economy won't fully recover. And a tepid economy is bad news for JPMorgan.

"Everything is fubar," Mr. Dimon was telling some staff earlier this year.

Mr. Dimon's 15th year as the CEO was supposed to be a good one.

JPMorgan closed out 2019 with $36 billion in profit -- eight times its 2004 earnings. Its stock hit an all-time high, pushing the value of the shares Mr. Dimon owns above $1 billion for the first time.

The early part of the year was packed with travel, starting with the opening number on every global CEO's dance card: the World Economic Forum in Davos, Switzerland. It was late January, and the coronavirus had sickened hundreds of people in China. That did little to damp the mood at the annual gathering of the world's business and political elite. Standing with former British Prime Minister Tony Blair, a longtime adviser to the bank, Mr. Dimon shook hands in a receiving line at a cocktail reception.

From Davos, Mr. Dimon went to Washington for another annual gathering of the rich and famous, the Alfalfa Club dinner. Then it was a retreat for the bank's top 200 senior leaders. From there, he went to Miami, where clients of JPMorgan's private bank for the ultrarich heard from Prince Harry and Meghan Markle. Covid-19 was still a distant worry; the U.S. had only a handful of confirmed cases.

Mr. Dimon was feeling under the weather but chalked it up to all the travel. Still, to be safe, he skipped the handshakes. When he came down with a fever, he stayed in his hotel room.

At JPMorgan's annual investor day on Feb. 25, Mr. Dimon hinted he was hunting for acquisitions, sending Wall Street into a tizzy. As a young, brash deal maker in the 1990s, Mr. Dimon helped assemble a global banking behemoth -- Citigroup Inc. But JPMorgan hadn't done a big deal since the financial crisis, when it scooped up failing Bear Stearns and Washington Mutual.

Mr. Dimon demurred when an analyst asked if the coronavirus would hit the bank's results.

"I have this nightmare somehow in Davos all of us who went there got it. And then we all left and spread it," he said. "The only good news from that is it might have just killed the elites. So I just don't know, we'll just have to wait and see. I'm not sure it helps to guess."

The audience laughed.

A few days later, the pandemic officially arrived in New York with the city's first confirmed infection. On March 3, the Federal Reserve moved to blunt the economic effects of the rapidly spreading virus with a half-point rate cut.

Wall Street wasn't laughing anymore. Investors piled into ultrasafe government bonds, sending the yield on the 10-year Treasury below 1% for the first time.

The mood had shifted at JPMorgan, too. Top executives formed a SWAT team to handle the growing crisis. They met several times a day in a conference room belonging to Mary Erdoes, the bank's asset- and wealth-management chief, that was retrofitted with dozens of screens to monitor coronavirus cases, staff and activity around the globe.

Mr. Dimon started drafting a letter to Treasury Secretary Steven Mnuchin and others, laying out his predictions for the virus's economic impact. The bank canceled its annual summit of CEOs.

On March 5, Mr. Dimon was supposed to be at St. Patrick's Cathedral on Fifth Avenue for the funeral of Jack Welch, the longtime General Electric Co. CEO.

Instead, he was 18 blocks uptown at NewYork-Presbyterian Hospital. The details of that morning are crystal clear in Mr. Dimon's memory. Clutching his chest, he replayed the moment the lining of his aorta burst.

"I felt it," Mr. Dimon said. "I thought I heard it."

His wife, Judy, ushered him downstairs and hailed a cab outside their Upper East Side apartment for a short ride to the hospital. He sent his secretary an email saying he didn't feel well and was getting checked out. His right arm ached and the vision in his right eye was sinking into a yellowy darkness.

At the hospital, a surgeon ran a quick test. The blood pressure in Mr. Dimon's left arm was high, with the top number reading 140. But his right arm showed 60, dangerously low.

Half his body wasn't getting enough blood.

A heart surgeon who had once operated on Mr. Dimon's late father explained that he was suffering from an aortic dissection, a tear in the inner wall of the essential artery that delivers blood throughout the body. Mr. Dimon's injury was to the part of the aorta closest to the heart, the ascending section just before the arch that plunges the artery downward.

Left untreated, aortic dissections are typically fatal. Because they are thought to be rare -- in 2018, dissections killed 9,923 in the U.S., according to the Centers for Disease Control and Prevention -- doctors often miss them. Actor John Ritter died after an aortic dissection in 2003. His doctors thought it was a heart attack.

In surgery, the doctor said, they would have a brief window to implant a tube and rebuild his aorta. At any moment, the whole thing could rupture. If that happened, there would be no way to save him.

Mr. Dimon told his wife to call Stacey Friedman, the bank's general counsel.

Ms. Friedman called the bank's lead director. Then she called Daniel Pinto, who runs JPMorgan's corporate and investment bank, and Gordon Smith, the head of its sprawling consumer operations. Together they had risen to become co-presidents and co-chief operating officers, overseeing the bulk of the bank's day-to-day operations.

Mr. Dimon was in surgery, she told them. They were both on deck.

As doctors patched up Mr. Dimon during seven hours of surgery, the board of directors held a vote to implement what they called the "Jamie got hit by a bus" plan -- the bank's emergency succession protocol.

JPMorgan's operating committee, Mr. Dimon's inner circle, gathered that afternoon. They shared word from the doctors and Mr. Dimon's family: The surgery went well but he wasn't out of the woods. Ms. Friedman dialed up officials at the Fed and the Office of the Comptroller of the Currency to tell them what was happening. The bank sent a memo to staff and released it to the press at the same time.

Mr. Pinto caught a plane from London, where he lives, due to arrive in New York at 2 a.m.

That evening, Mr. Dimon surprised his doctors by waking up. He was supposed to be knocked out for a day or two. He wanted his ventilator removed. His wife, his three daughters and two sons-in-law, and his twin brother were all waiting at his bedside.

Over the weekend, Saudi Arabia kicked off an oil price war that sent markets spiraling. On Monday morning, stocks fell so far so fast that they triggered, for the first time in 22 years, a market circuit breaker that halted trading for 15 minutes.

On March 11, Mr. Smith went to Washington, taking Mr. Dimon's place at a White House summit of America's top bankers. The televised meeting was meant to calm jittery markets and reassure the public that the nation's banking system was on solid footing. President Trump asked Mr. Smith how Mr. Dimon was doing.

(MORE TO FOLLOW) Dow Jones Newswires

12-24-20 1012ET