During my annual physical on March 1, my doctor, Thomas Nash, suggested that I get a CT angiography test. Not for any urgent reason, he said, but because I hadn’t had one in about five years. He figured it would be the wise thing for a 62-year-old like me to do.

I agreed—like John Fetterman, who is a decade younger, I can’t take anything for granted anymore—though, having experienced no heart-related symptoms, I expected the CT test to come out clean. I’ve run five marathons, climbed to the base camp of Mount Everest, and, one day last October, hiked 25 miles across Nantucket. That, on top of a regular diet of baby aspirin and prescribed cholesterol and blood-pressure medications, left me feeling as unsuspicious of my health as I was five years earlier.

I scheduled the test for April 6, then promptly postponed it until April 21 because of a conflict with another appointment. In the early afternoon, I showed up at a clinic at Broadway and 84th Street, had some dye pumped into and around my heart, and lay still while the fancy machine took pictures. Twenty minutes later, I was back on the street and off to my house in the Hudson Valley with my wife.

The next day, the journalist Ben Smith, who lives in a town nearby, came over for a visit. We walked Roscoe, my son’s Norfolk terrier that we were babysitting, then headed to a nearby distillery for some local color and a wee dram or two. When I got back home, there was a message on my cell phone from Dr. Nash. He said it was “imperative” that we speak.

“Imperative” is not a word you want to hear from your doctor under any circumstances, much less so after you’ve just had your heart dyed and scanned. When I spoke with him an hour later, he told me the test showed that one of my arteries—affectionately called the “widow-maker”—was 99 percent blocked. He told me I should return immediately to New York City, and that he would arrange for another test, this time at the hospital, to make sure the previous one hadn’t yielded a false positive, although he said he doubted that would be the case here.

A week later, I was on the operating table. While I was fully conscious, the doctors opened an artery in my wrist, pumped more dye toward my heart, and quickly determined that the blockage was real. The doctors also concluded that they could not insert a stent into the artery to open it up and get the blood flowing. Having made that determination, they summarily discharged me back onto East 68th Street. It felt like a rocket launch that had been scrubbed at the last minute.

Later that afternoon, my wife and I met with my new cardiologist—suddenly I had a cardiologist?—who delivered the tough news that, because the artery was too blocked for a stent, I had only two choices. One was to do nothing and take my chances. I still had no symptoms and, because of my relative fitness, had developed “collaterals,” a series of blood pathways that had compensated for the blood not reaching the lower part of the heart through that main artery. It was likely no heart attack was imminent, he said. But if and when I had one—and his case was convincing that it was more when than if—it could be curtains for me.

Suddenly, choice No. 2, heart-bypass surgery, became more attractive. You can’t live your life thinking you could have a heart attack at any moment. But, God, the words “heart-bypass surgery” were overwhelmingly serious, and so was the image of the gifted Len Girardi, my cardiac surgeon, cutting through my sternum and going to town on my heart while I delighted in the sister miracles of anesthesia and the heart-lung machine.

I’m told the way heart disease typically manifests itself is by sudden death, as it did for my friend Tony Horwitz, the former Pulitzer Prize–winning Wall Street Journal reporter and best-selling author, three years ago. Needless to say, this was a very unfortunate turn of events, and one that stunned me and my family. By what can only be characterized as extreme serendipity—what if I hadn’t taken the test that Dr. Nash recommended?—I suddenly faced the daunting but welcome prospect of electing to cheat sudden death, despite having no symptoms. Nothing focuses the mind at night like an execution in the morning, so they say.

I don’t care to relive anytime soon the frightening dawn gurney ride into the operating room on May 12, or the somber order to remove my wedding ring before my extremities swelled up. While Dr. Girardi was in the neighborhood, he also did a second bypass on a smaller artery. Again, not something I want to repeat.

By the time I regained consciousness in the intensive-care unit six or seven hours later, I didn’t have a clue about what had transpired. I awoke to my wife and younger son in my I.C.U. room and realized that I had a breathing tube down my throat. Not exactly the picture of parental invincibility. A friend had warned me about the breathing tube, but it’s an apparatus whose ghastliness you can’t comprehend until it’s already inside of you.

Once that tube was removed three hours later—as well as various other tubes over time—my recovery was rapid and blessedly uneventful. Milestones were achieved quickly. I was up and walking around in a day. Transferred out of the I.C.U. after 36 hours. Strolling out of the hospital unaided into a waiting cab. Exchanging e-mails with my editor at AIR MAIL in no time. Back home after five days. A clean bill of health after three weeks. Back to jogging in two months. Except for the lengthy scar down the middle of my chest, it’s almost like it didn’t happen.

But it did. And that simple test, on April 21, probably saved my life, and certainly extended it. People are busy living, racing around from one important thing to the next. But if your Dr. Nash tells you to get a test, as annoying as it might seem at the time, do it. It just might be the difference between life and death.

William D. Cohan is a Writer at Large for AIR MAIL and the author of such best-selling books as The Last Tycoons, House of Cards, and The Price of Silence. He is a founding partner of Puck. His new book, Power Failure, will be published in November