02:32am Thursday 14 December 2017

Study Explores the Connection Between the Brain and the Heart

David Sheps, MD, study leader.

News Article ImageLed by cardiologist David Sheps, MD, professor, Emory University School of Medicine, the five-year study is investigating mental stress-induced ischemia, a lack of blood flow to the heart triggered by psychological stress.

Sheps and his Emory colleagues, cardiologist Arshed Quyyumi, MD, professor of medicine and director of the Emory Cardiovascular Research Institute, and Viola Vaccarino, MD, PhD, professor and chair of the Department of Epidemiology, Rollins School of Public Health, are conducting three related studies involving up to 650 male and female patients with stable coronary heart disease between the ages of 30 and 82.

Genetics

Sheps is studying the role that different types of genes play when it comes to mental stress ischemia. People with different types of genetic makeup may be more or less likely to have this type of ischemia. This could allow doctors to predict which patients are at greater risk with a simple test.

According to Sheps, this is a very important area of research because there is a higher risk of adverse cardiac events and even death in patients who have mental stress-induced ischemia compared to those who do not.

 “This whole area used to be thought of as much more simplistic than we know it is now,” says Sheps. “Patients who develop ischemia, do so based on several different mechanisms.”

Sheps says what is most striking about the vascular system’s response to physical versus mental stress is how different they are. “You can have ischemia in different areas of the heart in response to mental stress versus exercise stress,” explains Sheps. “So, if ischemia were related only to major narrowing of the large arteries, you would expect it to occur in the same area, but that’s not always the case.”

Vascular Role

In another portion of the study, Quyyumi is researching the vascular angle of mental stress ischemia. Evidence shows that ischemia brought on by mental stress can prove more dangerous than ischemia brought on by physical stress and Quyyumi suspects the reason for this lies in the lining of the blood vessels, or the endothelium.

According to Quyyumi, during times of excitement or stress, the adrenal glands secrete hormones that increase heart rate and blood pressure. This increase calls for more blood flow to the heart, which means blood vessels and arteries should dilate to allow blood to flow more freely through the circulatory system.

 But in some people, this does not happen. The very chemicals that increase heart rate and blood pressure instead cause arteries and blood vessels to constrict.

So, Quyummi and his colleagues are measuring nitrous oxide levels in study participants by looking at brachial activity, or blood flow in the arm. They are impeding blood flow in the forearm of participants with a blood pressure cuff and imaging the size of the brachial artery, which extends from the shoulder to the elbow, with ultrasound.

Quyyumi is also measuring arterial stiffness to learn more about how blood vessel function is associated with ischemia and how it differs in people who are developing mental stress-induced ischemia versus those who are not.

The Brain’s Role

Meanwhile, Vaccarino is investigating what role the brain itself plays in mental stress ischemia.

“It’s your nervous system, particularly your autonomic nervous system, but also perhaps other areas of the brain that are involved in cognition, perception, and mood,” says Vaccarino. “All these areas are connected to the autonomic nervous system and could influence your tendency to have mental stress ischemia.”

To test her hypothesis, study participants will speak about an emotionally-charged issue in front of a small audience. Researchers will image the brain before and during the mental stress to see how it responds. Findings in the brain will then be compared with findings in the heart, which will be imaged under a similar mental stress procedure on a different day.

A PET scan will show changes in the brain caused by mental stress, so particular areas will light up, Vaccarino explains. “We want to compare people with mental stress ischemia to those without mental stress ischemia and see if different areas of the brain are involved. In particular, we suspect that brain areas involved in mood states such as depression may be affected.”

“If our results are compelling, we hope they will wake up the health community to pay more attention to the emotional factors in cardiac patients,” she adds.

“Perhaps in the future, we could devise a standardized psychological stress test to use in clinical practice. That may be our next step—to develop a clinical trial on stress reduction.”

To learn more about the study, please contact Emory Health Connections at 404-778-7777 or 1-800-75-Emory.

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The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service.

Contacts:       Jennifer Johnson: 404-727-5696


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