A quarter of cardiac arrest survivors suffer long-term psychological problems such as anxiety, post-traumatic stress disorder and depression.
This additional stress on recovering patients is under diagnosed, researchers wrote in the journal Resuscitation, and doctors have few standard methods for identifying who is at risk.
"Anxiety, depression and PTSD are major concerns after cardiac arrest," said lead author Kathryn Wilder Schaaf, a postdoctoral fellow at Virginia Commonwealth University.
"We have the tools to treat this, it's important to make sure it's identified."
Many long-term care issues for survivors are unknown, experts said, largely because only 10pc of the 382,800 US residents who suffer cardiac arrest each year survive.
Cardiac arrest -- when the heart stops beating suddenly and completely -- is distinct from conditions often labelled as "heart attacks."
In cardiac arrest, if the heart is not restarted quickly, brain damage or death usually results.
Cold therapy, which can protect the brain for a time, and implanted defibrillator devices, which can re-start an arrested heart, have helped to lower the death toll from cardiac arrest, but little is known about what mental and emotional scars may linger among survivors.
Wilder Schaaf and colleagues reviewed 11 studies published between 1993 and 2011 that looked at mental health issues following cardiac arrests experienced outside of a hospital and found problems plaguing anywhere from 15pc to 50pc or more of patients
Months to years after surviving cardiac arrest, about one-third of patients were depressed and nearly two-thirds were experiencing anxiety.
Even PTSD symptoms were surprisingly common, afflicting 19pc to 27pc of survivors.
In reality, however, the long-term mental health state of many cardiac arrest survivors is not typically considered or assessed, but treating mental illnesses in other types of heart patients has been shown to increase long-term survival.
Research suggests that mental health issues have an impact on recovery.
Over a five-year period, survivors of cardiac arrest who did not show signs of PTSD lived three and a half times longer than those with ongoing trauma, according to a 2008 study by Karl-Heinz Ladwig, an epidemiologist at the Helmholtz Zentrum Munchen in Germany.
Stress can affect the nervous system and have an impact on heart rates, as well as worsening chronic inflammation, Ladwig said.
"We have problems convincing cardiologists to understand that depression is a very relevant part of their clinical work," he added.
An avoidance of doctors, medications or follow-up appointments are all signs that a recovering heart patient should seek mental health help.
Peer support groups and smart-phone apps can help the patient develop feelings of safety, experts said.