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Reuters: "Among 30 patients having a procedure to evaluate their chest pain, researchers found that those who were told they were being given an infusion of a pain-relieving drug did, on average, report a decrease in pain.
But the participants also showed a measurable change in their heart arteries: a slight but distinct narrowing of the vessels.
Exactly what the findings mean, and whether they have implications for heart disease patients, is not clear.
None of the chest-pain patients actually had heart disease; they were told about the "drug" (which was actually harmless saline) only after testing had shown no blockages in their heart arteries.
The key point is that the power of suggestion created an objective change in the blood vessels, according to Drs. Karin Meissner and Joram Ronel of Technical University Munich in Germany.
"The major finding was that the coronary vessels reacted so clearly to a mere psychological intervention," they told Reuters Health in an email.
And the reaction was in a direction opposite to the one researchers had expected to see.
The patients were actually told that the "drug" they were receiving would widen their arteries to relieve their chest pain. Instead, there was a small amount of blood vessel constriction in the group overall.
But that constriction does make biological sense, according to Meissner and Ronel.
In a healthy person who is under stress, the nervous system triggers a widening in the blood vessels so that blood circulation increases to meet the body's needs. When stress fades, the vessels can narrow again.
"When the heart works less," Meissner and Ronel explained, "there is less need for blood supply, and the vessels will be less dilated than in a stressful situation. This is how we interpret our data."
They added, though, that this is the process in a healthy person. The situation may be different in a person with heart disease.
The findings, reported in the American Heart Journal, build on a phenomenon seen in clinical trials studying heart disease. That is, some people receiving placebos (inactive "treatments") report improvements in symptoms like chest pain.
How much of that reaction is due to psychological or even biological effects is unclear.
To examine whether there might be placebo effects on the heart arteries, Meissner and Ronel's team looked at 30 patients who underwent coronary angiography to evaluate chest pain symptoms.
During coronary angiography, a thin tube (catheter) is threaded through a blood vessel into the heart, where a special dye is injected. Using X-rays, doctors can then look for blockages in the heart arteries that may be the source of the chest pain.
The 30 patients were included in this study only after the test turned up no blockages. While still on the exam table, they were randomly assigned to either a "verbal suggestion" group or a control group.
In both groups, patients received an injection of saline into the catheter. Those in the verbal-suggestion group were told it was a drug that would widen their heart arteries and boost blood flow to the heart. Patients in the control group were told nothing.
On average, the study found, the verbal-suggestion group reported a dip in their chest pain after the procedure, while showing some blood vessel narrowing. The opposite was true in the control group: slightly more pain and a little more vessel dilation.
The researchers say they suspect the pain reduction was an "indirect effect" of the verbal suggestion, but they cannot know for sure whether or to what degree the blood vessel changes might have contributed to it.
More studies on this question are still needed, according to Meissner and Ronel. If verbal suggestion does have a measurable effect "at the level of the heart" in people with actual heart disease, they said, that would be important to know."