For some heart attack survivors, psychological stress may be a better predictor of a future heart attack or death from heart disease than physical stress, according to researchers presenting at the American College of Cardiology's Annual Scientific Session Together with World Congress of Cardiology.
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Their study, which included more than 300 individuals who had suffered a heart attack, people with myocardial ischemia induced by psychological stress were twice as likely to experience a repeat heart attack than people with ischemia that had not been induced by mental stress.
The study, which lead investigator Viola Vaccarino says is the first study of its kind to assess comparatively young survivors of heart attack, suggests that factoring in mental stress may help clinicians improve their assessment of risk for repeat heart attack or cardiovascular death among heart attack survivors.
About myocardial ischemia and stress tests
Myocardial ischemia occurs when a reduced blood flow to the heart stops the heart muscle from receiving enough oxygen.
Conventional stress tests to check blood flow and the risk for heart problems involve exercising on a treadmill or taking a medication that induces a similarly fast heart rate to that seen during exercise.
In the current study, researchers from Emory University set out to explore whether myocardial ischemia caused by psychological stress was associated with repeat heart attack or death among people who had survived a heart attack and how testing for this type of stress compares with traditional, physical stress testing.
Of 306 participants (aged between 22 and 61 years, mean age 50), those who had experienced a heart attack in the previous eight months, those whose myocardial ischemia was caused by psychological stress were at a twice the risk of repeat heart attack or cardiovascular death, compared with those who had ischemia without psychological stress.
"In our study, myocardial ischemia provoked by mental stress was a better risk indicator than what we were able to see with conventional stress testing,” says Vaccarino.
These data point to the important effect that psychological stress can have on the heart and on the prognosis of patients with heart disease. It gives us tangible proof of how psychological stress, which is not specifically addressed in current clinical guidelines, can actually affect outcomes."
Dr. Viola Vaccarino, Emory University
What did the study involve?
Two types of stress testing were performed. For mental stress testing, participants underwent myocardial perfusion imaging after giving a speech to an intimidating audience. For physical stress testing, participants underwent the conventional testing that involves exercise or medication.
Overall, 16% of participants had experienced myocardial ischemia triggered by psychological stress, while 35% had suffered ischemia without mental stress. This suggests that conventional myocardial ischemia brought on by exercise or medication occurs more frequently than mental stress ischemia.
How many people had a heart attack or died?
Over a median three-year follow-up for the primary outcome of either repeat myocardial ischemia or cardiovascular death, 10% (28) of participants experienced a repeat heart attack and two died as a result of heart problems.
Among patients with myocardial ischemia triggered by psychological stress, the incidence of a repeat heart attack or cardiovascular death was double that among those without ischemia caused by mental stress, at 20% versus 10%.
The association between mental stress and heart attack or death remained the same after clinical risk factors and depression symptoms had been adjusted for.
Conventional stress myocardial ischemia, on the other hand, was not significantly associated with repeat heart attack or death.
"Patients who developed ischemia with mental stress had more than two times the risk of having a repeat heart attack or dying from heart disease compared with those who did not develop ischemia during mental stress," says Vaccarino. "What this means is that the propensity to have a reduction in blood flow to the heart during acute psychological stress poses substantial future risk to these patients."
If this restricted blood flow to the heart occurred in a real-life setting, it could cause dangerous arrythmia or a heart attack, she adds.
Mechanism of risk differs between mental- and physical-stress ischemia
Vaccarino says that, interestingly, the team also found that ischemia related to mental stress and ischemia related to physical stress were not associated with one another, indicating different pathological mechanisms.
"This points to the fact that stress provoked by emotions has a distinct mechanism of risk for heart disease and its complications compared with physical stress," she says
Since the sample size was small, Vaccarino and colleagues could not tell whether the risk for adverse outcomes differed between subgroups - by race, gender or previous experience of trauma, for example.
They now intend to conduct a study involving a larger population over a longer follow-up period to investigate whether certain individuals with mental stress-induced ischemia are at more risk of negative cardiovascular outcomes than others.