Update, Oct. 4, 2019: The Sanders campaign released a statement on Friday evening stating that the senator had a heart attack on Tuesday evening. Sanders spent three nights in the hospital in Nevada, and is expected to return home to Vermont this weekend. “After two and a half days in the hospital, I feel great, and after taking a short time off, I look forward to getting back to work,” Sanders said in the statement.

A 78-year-old man with a medical history of gout and diverticulitis comes to the emergency department after developing chest discomfort while at a work function.

The patient’s overall clinical scenario is concerning enough that he is admitted to the hospital, where interventional cardiologists urgently perform a procedure called a cardiac catheterization. When the doctors inject dye into the major coronary arteries that supply blood to the heart, they find that one of them is so severely blocked that they must immediately place two stents in an effort to restore normal blood flow and hopefully prevent cardiac tissue around it from dying.

Based on the information his campaign has released, this scenario seems to be what happened to Bernie Sanders on Tuesday evening. Without a close look at Sanders’ medical chart, it’s impossible to make a definitive diagnosis, and I have not reviewed the details of his case other than what has been reported to the media by his campaign. But even the scant information we have—that he had stents inserted overnight following an acute cardiac episode—is enough to be able to say: This was very likely a heart attack.

I asked the Sanders’ campaign directly if they could confirm that this was or was not a heart attack. They declined to comment on the record. On Wednesday evening, the Wall Street Journal ran a story that originally stated a spokesperson for Sanders said the senator “didn’t suffer a heart attack,” but that story was later updated to remove that assertion. The story now states that the spokesperson said “more tests would be run to determine that diagnosis.”

A myocardial infarction, the medical term for a heart attack, is defined as an acute injury to the muscle of the heart, accompanied by clinical evidence of inadequate blood supply. This is usually confirmed with a blood test called a cardiac troponin that detects evidence of the damage (this testing takes hours, not days). The threshold that must be reached to raise a doctor’s suspicion of a heart attack is not high. New chest pain or pressure certainly suffices. Pain or new shortness of breath, whether with exertion or at rest, also suffices. But even less obvious symptoms such as sweating, jaw pain, or sudden arm tingling are enough to spur an immediate investigation.

When symptoms are obviously related to the chest, we call them “anginal.” We know that Sanders presented to the doctors with classic anginal symptoms, and that he underwent cardiac catheterization urgently, because the campaign told us so. We can therefore interpolate a great deal about what the emergency doctors and cardiologists likely discovered. If his bloodwork and his electrocardiogram had both been normal, there would have been no need to rush him to the cardiac catheterization suite in such a short time frame (it’s possible some doctors would rush him for catheterization even if those tests were normal, but that would only happen if the patient’s symptoms were extremely bad). The fact that the time frame for this was so accelerated indicates that at least one of those two findings was present, and thus the senator almost certainly met the clinical definition of a heart attack.

The suspicion that Sanders was experiencing a heart attack would have been confirmed in the cardiac catheter suite when his cardiologists found at least two blockages in one of his coronary arteries that required and were amenable to stents. We don’t know whether the fact that he had two stents placed in one artery is evidence of a limited heart attack or the opposite.

Some commentators have been hedging about whether Sanders had a heart attack or not. Here’s why that hedging is likely unnecessary: Other than a heart attack, there are two scenarios that would require coronary stent placement: unstable angina and stable angina. Stable angina is defined as chest pain (or similar symptoms) that do not change over time, and the information the campaign gave about him experiencing chest pain suddenly, during an event, suggests this is not what Sanders experienced.

That leaves unstable angina as the only alternative to a heart attack. Unstable angina is an increasingly controversial topic among experts. In essence, unstable angina is progressive coronary artery narrowing that causes worsening symptoms, but is not necessarily accompanied by new EKG findings or abnormal blood tests. It’s basically an impending heart attack, a ticking time bomb, in which the cardiac muscle has not yet died—but could crumple at any minute. Patients can have unstable angina for minutes, days, weeks, or even longer. While patients with unstable angina who receive stents often feel better afterward and heart attacks are prevented in a small number of them, the risks of the procedure are considered so dangerous—including bleeding, and even the possibility of inducing a heart attack—that only patients with severe risks and/or severe symptoms should undergo cardiac catheterization.

It’s also true that some patients bounce back quickly and essentially return to normal.

So, again, taken together, the facts we know are that Sanders required two stents and that this occurred in an acute clinical scenario. This means that either it was a heart attack or that it was unstable angina. Unstable angina carries just as poor a prognosis as many, though not all, heart attacks.

Recovery from a heart attack varies. Often people are tired, and most can expect a reduction in their tolerance for exercise and stress. Some are immobilized and require prolonged rehabilitation. It’s also true that some patients bounce back quickly and essentially return to normal. Without more information, we just don’t know what the scenario is for the senator.

Given that Sanders is running for president at the age of 78, I’d suggest it is perfectly reasonable to want to know whether he has just experienced a heart attack and how extensive the damage was. Patients who have had heart attacks have lower life expectancies and are far more likely to have strokes. If he’s going to continue in the race, he certainly should expect to disclose a bit more information about his health.

The opinions expressed in this article are solely those of the author and do not reflect the views and opinions of Brigham and Women’s Hospital.