It is a kilometre from my front door in Brighton to the local park, all downhill. A 45-year-old man, jogging not very fast, should be able to complete the journey without stopping; without fighting for breath; without feeling sick. Also, he should not be assailed by dread, feeling that the universe has suddenly turned a shade darker, soured, curled at the edges.

That is how I knew something was very wrong on New Year’s Eve 2019. It was around 2pm and I had made it three-quarters of the way when something detonated behind my ribs. The pain was familiar at first. Tediously so. I would often get a tight, burning sensation across my chest when running. It slowed me down but never stopped me in my tracks. I would get home panting too hard for words, my face flashing red and white. “Are you all right?” my wife would ask. “Yeah... just… gimme… a… second.” I thought that was normal in a man my age. Exercise was supposed to hurt a bit, and I took the pain in my chest as a barometer of unfitness. Breathing that doesn’t burn was a luxury for the younger man, I thought. But I had angina and called it middle age.

By 3pm on New Year’s Eve I was on a hospital trolley, still in my running kit. It wasn’t hard for the doctor to diagnose the problem.

Doctor (hurriedly): Have you taken any illegal drugs, Mr Behr?
Me (defensively): What, ever?
Doctor: Today, in the past 24 hours.
Me: Oh, right. No.
Doctor: Do you know of any family history of heart disease?
Me: Yes. Both sides.

Cardiac calamity had been advancing in a pincer movement down the generations towards me. My paternal grandfather had died from a heart attack. My dad had a triple bypass a few years ago. But the case history that felt pressingly relevant that afternoon was a man called Eric Rink, my mother’s father. One Sunday morning in Cape Town, 12 years before I was born, Eric had gone to play golf as he often did on the weekend, always returning in time for lunch. But that day lunch waited and waited until it was cold; Eric never came home. His heart had stopped. He was 45. His daughter, my mother, was 14, the same age as my eldest.

There are no safe heart attacks, but the variety I had is notoriously lethal: occlusion to the left anterior descending artery. That is the main power line to the left ventricle, which is the piston in the pump that supplies oxygen to the body. A plaque caused by fatty deposits that have built up over years splits open and obstructs the artery. A clot forms at the site and blocks the blood flow completely. The more old-fashioned cardiologists call it the “widow-maker”. I probably could have just about made it to the park, at a walking pace, if I had forced myself to carry on. But it is unlikely I would have made it home.

***

The decision to turn back took maybe 30 seconds. The pain was much more severe than usual and the nausea was new, as was the shimmering sense of doom. I told myself it couldn’t be a heart attack, because that would be preposterous – and inconvenient. We had guests coming for dinner. Not wanting a heart attack seemed like a good reason why I couldn’t be having one. It was the sort of thing that happened to other people. Then I remembered Eric Rink and lurched crookedly up the hill. By the time I got through the front door, I didn’t have enough breath to call for help.

My wife drove me to the hospital, staying heroically focused at the wheel while I wound down my window, chasing the oxygen that seemed to be fleeing my lungs. The roads were empty, it being New Year’s Eve. I tried to walk into A&E and explain the situation to reception, but found instead that collapsing on the floor communicated the necessary data more efficiently. “Next time, call an ambulance,” I heard someone say. Pro tip, I thought, but I’m not planning on making this a regular gig.

I told myself that everything would be all right; that heart attacks are not always the death sentence they used to be, thanks to advances in medical technology. But it also occurred to me that there is a moment in every parent’s life when we see our children for the last time, and that I might already have passed that moment without knowing to say goodbye.

Emergency angioplasty is a marvel of science. A catheter is inserted via a small cut to the wrist, up the arm, over the shoulder and into the heart. The obstruction is found and fixed with stents: tiny inflatable tubes that reinforce the artery wall. I was conscious but full of morphine, which does strange things to one’s sense of time. It felt as if the whole thing passed in minutes, but some of those minutes took years. The inflation of the stent temporarily reblocks the artery that has been smooshed open by the catheter, so it feels as if you are having a whole new heart attack. Then the balloon inside the stent is withdrawn, and blood can rush through. Every cell of your body gives a little cheer, like a nation of drought-stricken farmers celebrating the first drops of rain on parched fields. When the surgeon loaded up a second stent, I braced myself. I didn’t want the nice, cool rain feeling to stop. “Could you just give me a moment?” I asked. He shook his head. “Time is very much of the essence here, Mr Behr.”

Once the second stent was in, the pain began to dissipate. My mood overshot relief and landed in a zone of intense conviviality. I was chatty, exuberant. Psychologists call it “survivor elation”. Within hours, I was sending implausibly upbeat messages from my hospital bed, telling friends and family what had happened as if I had just returned from an exotic holiday. I emailed editors at work promising to “resume normal service as soon as possible”.

My heart was operating at around a fifth of healthy capacity. Some damage would be permanent, but some was just stunned muscle that would wake up over the coming weeks. I was discharged with a regime of pharmaceuticals and mild activity. A cardiac nurse talked me through the rules: slow on stairs, no heavy lifting, build up gradually to exercise, avoid stress. What did I do for a living? Journalism. What did I write about? Politics, mostly. Oh, how interesting. Is that stressful?

***

By the end of 2019, everyone in the Westminster press pack was wrung out by Brexit. We had been soaked in the referendum, rinsed by the 2017 general election, drenched in venomous rhetoric. That period was marked by an enervating combination of stasis and crisis. There were long periods of tense political deadlock punctuated with moments of frenzy.

The knife-edge parliamentary votes on May’s deal were particularly nerve-shredding. There was no time between result and deadline. We watched the cursor blink impatiently on a blank screen, poised to shovel it full of words. We spent the day twitchily texting MPs and advisers, swapping information with colleagues and rivals, scanning MPs’ faces from the Commons press gallery, reading body language. What has anyone heard? How are the numbers looking?

I enjoyed the intensity of it. The adrenaline took me back to an earlier time in my career, when I had been a foreign correspondent. But I didn’t envy my reporter friends and colleagues: as a columnist, I was just dabbling, a tourist in their trenches.

Covering the frontline in the battle between leave and remain, however, had some unique toxicity for me personally. Brexit was not just another competition between rival policy positions. The emotional attachments formed on either side went deeper than standard party loyalties. It was beyond stressful: it was distressing.

In the press gallery we talked about “Brexit derangement syndrome” in those MPs who had lost all sense of perspective. Formerly balanced individuals lapsed into a hysterical lather, especially on social media where they were not bound by the restraining conventions of the Commons chamber and had to compete with a million amateur demagogues for approving clicks and retweets. But none of us was immune.

What upset me as a remain voter was not the fact that Britain was leaving the EU, but the assertion that it was unpatriotic to oppose the idea. I hated the rhetoric of betrayal and treason that leavers used to denounce those of us who thought Brexit was a mistake. We were “citizens of nowhere” to Theresa May. When May called the 2017 election, the Daily Mail urged her to “crush the saboteurs”.

Denigration of remainer loyalty was a sequel to the xenophobic element in the 2016 referendum campaign – selling separation from the EU as protection from incoming migrant hordes. That was straight-up nationalism and it stirred a visceral anxiety about the character of Brexit, quite aside from any arguments about economics and trade. It clawed at the seam where I felt connected to the country I called home.

My parents had migrated to Britain in 1970 because apartheid South Africa was intolerable. Their grandparents had been part of the mass emigration of Lithuanian Jews in the first decades of the 20th century. Eric Rink had started life as Eliyahu Rinkunsky, the oldest of three brothers. His father saw the rising tide of antisemitic hatred and evacuated the family to a new life in a different hemisphere. He died not long after. The Rinkunskys got out in time, beating the odds, which for Lithuanian Jews were among the worst in Europe. Less than 5% of a thriving prewar community survived Nazi occupation.

There is one photo in which Eric looks like me, taken on the day he and his two brothers were demobilised after the second world war. Their berets are askew, their eyes bright but tired. I only noticed the resemblance when I scoured a digital scan of the picture from my bed in the cardiac recovery ward. It was strangely comforting to find the features that rhymed with mine. Something in the line of the chin, the nose, the heart.

People on both sides of the Brexit divide had intimate reasons for identifying with their cause. I was one of the remainers who admired the European project as the continent’s collective repudiation of bloodthirsty nationalism. The Europe that I voted for in 2016 represented the antithesis of forces that had driven my great-grandparents into exile and murdered those of their relatives who stayed behind. It pained me that the argument for Britain’s alignment with that ideal was being lost, and it frightened me that the winners were so vindictive in victory.

It pained me, too, that there was no consolation in the party I had always supported. There had been antisemitism on the left before 2015, when Jeremy Corbyn became leader, but under him the party was more hospitable to the prejudice. Corbyn was a magnet for every ultra-left crank and fanatic whose fixation on the evils of “Zionism” shaded into conspiracy theories about Jews plotting behind the scenes, pulling the financial strings of a puppet government.

Observing that trend was grim enough, but the stressful part was writing about it amid a culture of indifference that permeated the wider British left. To criticise Corbyn in print was to invite a torrent of abuse online. His hardcore supporters said the charge of antisemitism was itself a devious plot against the leader, more evidence of the conspiracy. The more squeamish fellow-travellers agreed that the whole thing stank, but held their noses anyway and campaigned for Labour.

That complicity animated a pungent hereditary fear: no matter how rooted Jews felt in a country, a movement, a culture, one day there will come along a mob carrying tools to dig us up, telling us we don’t truly belong. It is the cautionary tale our grandparents told about keeping a suitcase packed and a passport close at hand. “At least we are finding out who would have hidden us in their attic,” one Jewish friend said to me. We laughed because it wasn’t even a joke.

The combination of Brexit and Corbynism had me in a state of fizzing unease. Even when I looked composed or sounded detached in print, I was inwardly pacing in knotted agitation. I slept too little, ate and drank too much. I was distracted at home, impatient and shouty with my children. In photos from that winter I look puffy and grey. I knew that social media was the main pipeline bringing anger and anxiety into every corner of my waking life. I tried to ration my use during the 2019 election campaign, relying on other sources to find out what was going on. But by then I had already been contaminated. The stress was in the atmosphere of British politics, a fine chemical mist that coated everything. It was absorbed through my skin. It got into my blood, into my heart.

***

A doctor showed me the aftermath in flesh at one of my outpatient check-ups in March last year. I was recovering well but worried about this new coronavirus that was starting to dominate the news. There were reports that it was merciless with cardiac patients. Did 45 count as young or old in the eyes of this disease, I asked? The consultant paused for some mental arithmetic. “Think of yourself as more like 55 to 60.”

He brought up a video of my recent ultrasound scan on his computer and with a pencil indicated a narrow strip of dead muscle. It moved stiffly, while the rest of the heart pulsed; a notch of scarred tissue, burned up while the oxygen supply had been cut off during the heart attack. I had destroyed a decade’s supply of heart in around three hours. “We still don’t know much about this virus,” the doctor concluded. “Be careful. You could do without it.”

I was taking twice-weekly cardiac rehabilitation classes. We gathered in the middle of the day in a leisure centre. I was the youngest, although there was one patient, not much older, who had also had the “widow-maker” heart attack. He had waited two hours for an ambulance. When he reached the hospital he went into ventricular fibrillation, flatlined, and had to be yanked back from death’s grip with high-voltage paddles. “The lights went out,” was all he remembered of the experience. Time is very much of the essence, Mr Behr, I thought.

The classes reminded me of the driver speed awareness course I had once taken as penance for doing 40 in a 30mph zone. There was the same chastened schoolboy vibe: a room full of people, the overwhelming majority men, who needed reminding about the cardiac highway code. We had lectures on what to eat; how to manage stress. We learned about the various pharmaceuticals we were taking. There was an instructional video in which actors played out medical emergencies. There was a coy film to reassure us that it was safe for heart patients to have sex. “Most people have a rather exaggerated idea of how much physical exertion is involved,” said the on-screen doctor. No one dissented.

My favourite part was the supervised exercise session. We were given monitors to wear and sensible heart rates to maintain. We stepped over things, lifted our knees, trotted up and down, all under the watchful eyes of a nurse armed with a portable defibrillator kit. I learned to feel an accelerated pulse without fear. When I finished the course, I bought my own monitor and started running again, matching my stride to a cardiac beats-per-minute target. The first time I took my monitor for a test run I had to pass the corner where my chest had exploded. When I reached the park, I cried.

I take that running route often now, and award myself a defiant burst of speed. I leap over the ghost of myself lying on the pavement. He is a useful mental companion, the alternative version of me who waited too long in 2019 and missed the escape portal into 2020. He reminds me to take all of my various pills, and to resist the temptations of cake and pastry. (Deliciousness is a tediously reliable indicator of what foods cardiac patients are not supposed to eat.) I can also summon the ghost on the pavement at times of stress, when events in the world look bleak. He reminds me to breathe and not to take it all to heart.

Junk food was easier to quit than junk news, although the same discipline is involved. When a story breaks, I must not binge on instant reaction. I must not serve myself slices of thick, buttery outrage on social media. That was easy in the first weeks back from hospital, when I was off work. I stopped following politics and didn’t miss it. But I knew I would have to reintroduce news to my diet at some point.

In those early weeks, any strong emotion would give me a peculiar sensation, a dull ache rippling across my ribs, radiating out from the solar plexus, announcing the presence of stress before my conscious mind could compute the cause. I went to watch my younger daughter play football – a big match. But I had to leave the stadium because the tension was pinching the air from my lungs.

I wondered how I would cope with a quick print deadline, and whether I would get the tight-chest feeling from exposure to politics. Towards the end of the first month, I sampled a few minutes of Boris Johnson in prime minister’s questions, basking in his majority, and was relieved to discover that his bloviation didn’t interfere with my breathing. What had once been infuriating now looked banal and ridiculous.

I locked myself out of Twitter. I changed the password to an unmemorable sequence of random characters, which I wrote on a scrap of paper and sealed in an envelope. I still use this technique to police my usage, especially over weekends and on holiday. Sometimes I give the password to my wife for safekeeping. My phone is banished from the bedroom. I rediscovered the BBC World Service as a first port of call for news that lifts your eyes to a more global horizon. It puts parochial Westminster squabbles into perspective.

I have not set foot in parliament for over a year. It had taken me years to learn my way around the labyrinthine Palace of Westminster. Now I have a similarly intricate mental map of where the reliable patches of phone reception are at home, for speaking to contacts. I miss being able to read the mood of the Commons chamber, and the extra bits of gossip and intelligence you glean from chats in corridors and impromptu huddles by gothic stairwells. But there isn’t so much of that now anyway, thanks to the pandemic. I followed the final moves of the Brexit endgame last month with numb sadness. The seething anger is still available, and politics is always synthesising new reasons to feel enraged, but I handle the compound differently now. I try to decant it on to the page with less casual spillage into the rest of my life.

The pre-coronavirus world feels remote now anyway, submerged fathoms deep below everything that happened in 2020. I don’t know how much of that is the effect of my lucky escape from 2019, and how much is the effect of successive lockdowns. Months seem to have ticked past in minutes, while days have lasted for months. Time has been elastic, arrhythmic. It reminds me of the morphine.

It sometimes feels as if I counted through the whole of last year in heartbeats. I had not previously known what my natural resting pulse was, or how fast it could safely go. Now I can estimate it fairly accurately just by putting a couple of fingers to my neck. I can trace the progress of my recovery by the average beats-per-minute rate on my runs, recorded by the monitor strapped to my chest and plotted on a graph.

For perspective, I try to run to a place where I can see the horizon. I venture along the Brighton seafront, or up into the South Downs, clocking up around 45km a week – way more than I ever managed (or even attempted) in the years of battling through angina. I can fit into the suit I wore at my wedding 15 years ago. I have read a bit about running technique. It turns out I had developed all sorts of bad habits. The worst was my tendency to stare down, hunched, focused on the ground just in front of me. I’m working to correct that now. The trick is to relax the shoulders, don’t clench the fists, breathe evenly. Look out, look up.

• Rafael Behr will be running 25km to raise money for his local cardiac care charity. To sponsor him, go to justgiving.com/fundraising/rafael-behr.