Is a Heart Attack Cardiac Arrest?often used interchangeably,

Heart attack, cardiac arrest, and heart failure are often used interchangeably, but they’re distinct entities.

The first reports were that Fisher had a “heart attack” after becoming unresponsive on a flight to Los Angeles. The Los Angeles Fire Department, which continued the CPR that had been initiated on board and then transported her to the hospital, stated that she had in gone into “cardiac arrest” but had later regained a heartbeat. UCLA Medical Center described the problem as a “cardiac episode.” Family members finally said that even they had no idea what was going on; the cause of Fisher’s illness was simply not known, though she was eventually described as “stable” by Sunday. (“Stable” may sound comforting, but it is medically meaningless—I’m stable, but so are many patients who are on breathing machines in ICUs.)

Many outlets are now reporting that Fisher died following “a massive heart attack.” This was the language family spokesman Simon Halls used when speaking to the New York Times, but when asked for more details, he declined to elaborate.

What was the final cause of death? Heart attack? Cardiac arrest? Heart failure? Cardiac episode? These may sound like similar events. They’re not. (That last one, “cardiac episode,” doesn’t really have any medical meaning at all.)

Heart attacks, cardiac arrest, and heart failure are in fact markedly different entities. Heart attacks, or “myocardial infarctions,” refer to any irreversible cell death to the muscle of the heart. Heart attacks are caused either by the rupturing of small areas of hardened arteries (atherosclerotic plaques), which then travel to smaller vessels and cut off blood supply to the heart muscle itself, or by an imbalance between the supply and demand of oxygen to the heart. (Heart attacks caused by medical procedures are considered separately.)

In a mild heart attack, a small amount of tissue dies. If the area of cell death is small enough, the heart may continue to contract at nearly 100 percent of its previous ability, and the person may not even notice the event. But once a heart attack is large enough, the patient will notice. In a massive heart attack, enough tissue can die to make the heart lose the ability to pump enough blood out to sustain life. Patients usually show up to emergency departments complaining of sudden chest pain that radiates to their arms, neck, face, and sometimes their backs. Less well-known symptoms, such as shortness of breath, are quite common as well. Patients having heart attacks typically appear to be in significant discomfort, but they can usually describe their symptoms, because they tend to be awake, alert, and asking for medicine (we start with aspirin, which has a known benefit in heart attacks).

Heart attacks are rarely diagnosed outside of hospitals. In addition to the clinical symptoms, diagnosing one requires an electrocardiogram and blood testing. (This would be hard if not impossible to do on a plane; for example, the EKG functions on commercially available automated defibrillators do not provide enough information to diagnose heart attacks.)

The short-term mortality rate of a patient admitted to the hospital after a heart attack is relatively low at around 5 percent. The sooner the vessels of the heart can be reopened—usually with a combination of medications and cardiac stents—the more heart tissue survives. Frequently, people survive heart attacks but experience a decrease in exercise tolerance because part of their hearts can no longer squeeze—suddenly, a few steps may feel like a marathon.

On the other hand, cardiac arrest is not a cause of death—essentially, it is death. It’s what happens when the heart stops beating entirely or stops beating well enough to create a blood pressure high enough for a detectable pulse. Patients who show up to emergency departments in cardiac arrest cannot describe their symptoms because they are unconscious and are undergoing life-sustaining chest compressions.

The line between cardiac arrest and death is very thin: When patients arrive at emergency departments in cardiac arrest, we often think of them as having “arrived dead.” We then attempt to revive them using all appropriate measures. By definition, anyone who has ever died has suffered cardiac arrest.

[perfectpullquote align=”left” cite=”” link=”” color=”” class=”” size=””]Cardiac arrest is what happens when the heart stops beating entirely or stops beating well enough.[/perfectpullquote] Cardiac arrest is uniformly fatal without immediate intervention. Even with our best efforts—and despite its depiction on television and in movies—patients who suffer cardiac arrest outside of a hospital setting have less than a 15 percent rate of survival. Fewer survive to hospital discharge, and fewer still resume neurologically intact lives after such events. And for many, the only thing

worse than suffering cardiac arrest would be to survive it—often, those who do have already experienced brain death or persist in a vegetative state.*

Cardiac arrest has many causes, from blood clots in the lungs to a collapsed lung compressing the heart so much that it can’t maintain its normal cycle. The most survivable causes of cardiac arrest are electrical problems of the heart, some of which are indeed caused by heart attacks. Some of these cause what we call “shockable rhythms.” These rhythms, ventricular tachycardia and ventricular fibrillation, have a real chance of responding to jolts of electricity known as defibrillation. Other rhythms, such as asystole (“flat-lining”), do not respond to shocks (again, contrary to television and movies). In fact, most causes of cardiac arrest are not amenable to defibrillation. Unless an immediate cause is obvious (such as a massive electrolyte imbalance in patients on chronic kidney dialysis), even heroic efforts to bring these patients back to life are usually in vain.

Then there’s heart failure—which, we were told, was the cause of death for George Michael. Heart failure is when the efficiency of the pumping heart has been reduced. Every time our heart pumps, it pushes blood out to the rest of the body. When the muscle of the heart loses its ability to pump blood at maximal efficiency, we call it heart failure. As a result, less blood and oxygen reaches other parts of the body. This can cause a kind of liquid traffic jam: If blood isn’t moving forward with each pump, it often ends up backing up in the veins that return blood to the heart. This leads to fluid in the lungs or in other parts of the body, often the lower legs. As heart failure progresses, pumping efficiency becomes so poor that the body’s metabolic demands are no longer met, and blood supply is too low to continue many of the activities we take for granted.

This can happen slowly over time, as a result of chronic elevated blood pressure or high cholesterol or due to drug and alcohol use, among other causes. Alternatively, heart failure can develop suddenly as a result of—you guessed it—a heart attack. It’s possible for a moderate to severe heart attack to kill enough heart muscle that the pump loses its efficiency almost immediately. Most forms of heart failure, however, are chronic. Patients slowly lose exercise tolerance, and eventually any stress on the heart at all can become life-threatening. Heart failure is diagnosed by a cardiac ultrasound that assesses how well the heart is pumping, and treatments include medications to decrease the amount of fluid in the body and others that may help the heart pump more efficiently and even repair itself from past damage. The prognosis can vary greatly, depending on the severity and other risk factors. Some patients have a five-year mortality rate of well under 5 percent, while others may have more than 75 percent of dying in that time frame.

Heart attacks and heart failure can rarely be diagnosed outside of medical settings. Cardiac arrest is different though—it can be diagnosed anywhere, as it seems to have been on the plane Fisher was on. And it is possible that a heart attack caused Fisher’s cardiac arrest, so perhaps all of the reports are correct. Either way, someone on that plane noticed that Fisher had lost consciousness, no longer had a pulse, and thus needed life-sustaining CPR. That person did his or her best. It could have been a medical professional or not—it takes minimal training to recognize these signs and to perform CPR. The odds were never good. But they rarely are with cardiac arrest.

*Correction, Dec. 28, 2016: This story originally misstated brain death and vegetative states as the same. They are distinct. (Return.)