Brain MRI Pattern Linked to Excess BP Response to Mental Stress

Megan Brooks

August 25, 2017

PITTSBURGH, PA — A pattern of brain activity on functional magnetic resonance imaging (fMRI) may help identify individuals prone to an exaggerated blood-pressure response to psychological stress, say researchers[1].

"The potential clinical implication is that brain imaging may one day be useful in understanding and predicting a person's risk for heart disease," lead researcher Dr Peter Gianaros (University of Pittsburgh, PA) told theheart.org | Medscape Cardiology.

"A next step would be to determine whether interventions to reduce stress and lower heart-disease risk—such as increasing physical activity—alter the pattern of stress-related brain activity that we identified," Gianaros said.

The study was published online August 23, 2017 in the Journal of the American Heart Association.

Brain Phenotype for Stress-Evoked BP Reactivity

People who tend to have exaggerated blood-pressure reactions to psychological stress are at risk for hypertension, adverse clinical cardiovascular events, and premature death from cardiovascular causes, the authors note in their report.

The current study shows, according to the report, that exaggerated blood-pressure reactions to psychological stressors may be determined in part by a "brain phenotype" that is characterized by "reliable" neural activity changes in areas of the brain that regulate cardiovascular physiology during stressful events.

The study included 310 adults, about half women and half men, aged 30 to 51 years participating in the Pittsburgh Imaging Project, an ongoing study of how the brain influences cardiovascular-disease risk. All participants underwent fMRI with concurrent blood-pressure monitoring while completing a standard stressor battery, which included a Stroop task and modified Multi-Source Interference Task (MSIT). Both entail conflict, negative feedback, and responding under time pressure to unpredictable and uncontrollable stimuli.

Participants' average resting blood pressure was systolic 120.6 mm Hg and diastolic 72.4 mm Hg.  As expected, the mental stress tests led to an increase in blood pressure and heart rate in most participants compared with baseline.

Change From Baseline in Blood Pressure, Heart Rate

Parameter, change from baseline MSIT Stroop
Systolic/diastolic blood pressure, mm Hg 3.5/1.4 5.0/22
Heart rate, bpm 6.2 8.1

Using cross-validation and machine-learning techniques, the researchers identified a multivariate pattern of stressor-evoked fMRI activity in a training subsample of 206 patients. This pattern predicted both systolic blood-pressure (P<0.005) and diastolic blood-pressure (P<0.01) reactivity in an independent subsample of 104 participants used for testing and replication.

This pattern was "reliably associated with individual differences" in stressor-evoked systolic blood-pressure reactivity, the researchers report. The brain phenotype for systolic blood pressure accounted for around 9% of the variance in individual differences in stressor-evoked systolic blood-pressure reactivity, with overall accuracies in predicting normative systolic blood-pressures changes ranging from 0.6 to 0.8, they note.

"Brain areas encompassed by the pattern that were strongly predictive included those implicated in psychological stressor processing and cardiovascular responding through autonomic pathways, including the medial prefrontal cortex, anterior cingulate cortex, and insula," they write. 

To their knowledge, this is the largest neurophysiological study of stressor-evoked blood-pressure reactivity and the first to apply cross-validation methods to characterize a "putative brain phenotype for this particular stress-related predictor of CVD risk," they point out.

The researchers note that their findings are based on a group of middle-aged healthy adults at low risk for heart disease and therefore may not be applicable to patients with existing heart disease.

Support for Brain–Heart Link

Asked to comment on the results, Dr Ahmed Tawakol (Massachusetts General Hospital and Harvard Medical School, Boston) said, "A link between stress and disease has been suspected for centuries. More recently, it has become clear that psychosocial stress has an attributable risk for cardiovascular disease that is on-par with major risk factors such as smoking, hypertension, and diabetes. Yet the mechanisms mediating that risk have until recently been poorly understood."

"The study by Gianaros et al used functional MRI imaging, coupled with cutting-edge analytical approaches, to delineate the components of the brain that may produce an exaggerated blood-pressure response to stress. This observation may be important, since an exaggerated stress-induced blood-pressure response is known to associate with an increased risk for subsequent hypertension and cardiovascular disease events," Dr Tawakol told theheart.org | Medscape Cardiology.

"Accordingly," he said, "this study adds to the growing body of work linking altered neural activity to downstream cardiovascular disease. Studies like this may set the stage for subsequent trials to test whether modulating those neural mechanisms (through stress-reduction approaches or novel pharmacotherapies) may attenuate cardiovascular disease risk."

The study was funded by the National Institutes of Health and National Science Foundation. The authors had no relevant financial relationships. Tawakol has received grants from Genentech and Takeda, and personal fees from Takeda, Actelion, AstraZeneca, and Amgen.

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