Survivors of Heart Emergencies at Higher Risk for Cognitive Problems

Cardiac arrest is an extremely serious medical event, and one that frequently ends in the death of the patient. "Survival is actually terrible," says David Vorchheimer, MD, cardiologist at the Montefiore Einstein Center for Heart and Vascular Care in New York City. "Survival is 10 percent or less in patients who sustain out of the hospital cardiac arrest, but is substantively improved if the victim received bystander CPR [cardiopulmonary resuscitation]."

Cardiac arrest occurs when the heart rhythm becomes chaotic and the normally organized contraction of heart muscle is lost; blood is no longer pumped and the heart suddenly stops beating. Unfortunately, "It's not uncommon," says Umesh Gidwani, MD, director of the Cardiac Intensive Care Unit of The Mount Sinai Hospital Medical Center in New York City. "About half million people a year suffer a cardiac arrest in the United States, and the incidence increases with age and underlying heart disease."

And even those who survive don’t necessarily have a rosy future: Half of cardiac arrest patients experience problems with cognitive functions such as attention and memory. Why is this? Doctors have theorized that the lack of oxygen to the brain causes the persistent neurological problems. But a recent study found that people who lived after a heart attack also showed signs of mild brain damage—even though the heart attack survivors had not experienced obvious oxygen deprivation. (In a heart attack, unlike cardiac arrest, blood flow to the heart is interrupted. This can happen when there’s a blood clot or blockage from built-up cholesterol and other substances in an artery, a vessel that carries blood from the heart.)

The study on brain function, led by researchers at Lund University in Sweden, focused on 950 cardiac arrest patients in Australia and Europe. Within six months of suffering cardiac arrest, half the patients had died. The survivors were followed with cognitive screening tests. Subsequently, 300 of the survivors took more detailed tests, and these were compared with a control group made up of heart attack patients.

Interestingly, the mild brain damage was evident in both groups: "We thought there would be a clear difference between the groups, because the heart attack patients had not been exposed to any oxygen deficiency in the brain," writes Tobias Cronberg, MD, PhD, associate professor at Lund University and consultant neurologist at Skane University Hospital in Lund, according to Medical News Today. "However, they had signs of mild brain damage to almost the same extent as the cardiac arrest patients."

So researchers think the cognitive problems could instead be due to the same risk factors that patients with a variety of heart problems face: namely diabetes, high blood pressure, and high cholesterol—providing ever more reasons to keep these common conditions under control.

What Can Be Done to Preserve Brian Function in Heart Patients?

To reduce the risk of cognitive problems in patients who suffer heart emergencies, doctors typically lower the patient’s core temperature. "If the person's core temperature is kept down for a couple of days and then slowly warmed up, this can preserve neurological function," explains James Ip, MD, a cardiologist at Perelman Heart Institute of New York-Presbyterian/Weill Cornell Medical Center in New York City. But "There is some debate over how long to cool the person, and at what temperature. The person must be kept sedated during the process, so you can’t ask them how they are doing."

The Lund university researchers found that cooling patients’ bodies to 36º C (96.8º F) helped patients survive—and preserved their cognitive abilities.

Karl Kern, MD, of the University of Arizona, called the study "very well done," but noted that other research is needed to validate the results. In the meantime, he says, it is sensible for everyone to try to reduce their risk factors for heart problems: "Everyone should pay attention to the things they can change, and work on changing them," Kern says. "These include factors like high cholesterol and obesity."

To keep your heart healthy, get regular exercise, quit smoking, and watch your caffeine intake, Gidwani advises. "In general, just lead a healthy lifestyle."

David Vorchheimer, MD, reviewed this article.


James Ip, MD. Phone interview June 11, 2015.

David Vorchheimer, MD. Phone interview June 10, 2015.

Umesh Gidwani, MD. Phone interview June 10, 2015.

"Cardiac Arrest Statistics." American Heart Association. Page updated January 1, 2015.

"Cognitive Problems Are Common After Cardiac Arrest." Medical News Today. Last updated 21 April 2015.

Cronberg, T. et al. "Neurologic Function and Health-Related Quality of Life in Patients Following Targeted Temperature Management at 33°C vs 36°C After Out-of-Hospital Cardiac Arrest: A Randomized Clinical Trial." JAMA Neurology. 72, 6 (2015):634-41.