Magnetic resonance spectroscopy after normal angiography can identify women with chest pain due to abnormal myocardial metabolism, according to an article in the June 15th rapid access issue of Circulation.

Identification of these women, who have a coronary event rate similar to that of women with coronary artery disease, can enable them to avoid repeat hospitalizations for chest pain, as well as cardiac catheterization and other diagnostic procedures, said B. Delia Johnson, Ph.D., lead author of the study.

The Women’s Ischemia Syndrome Evaluation (WISE) studied women who had been referred for coronary angiography because they were experiencing chest pain or had suspected myocardial ischemia. The study population consisted of 74 women who had chest pain and no significant coronary artery disease per angiography and a reference group of 352 women with confirmed coronary artery disease. Among the women without disease, 60 had a normal spectroscopy results and 14 had an abnormal result. Average age was 56 years.

Magnetic resonance spectroscopy detects changes in levels of phosphocreatine (PCr) and adenosine triphosphate (ATP). Reductions in the ratio of phosphocreatine to ATP in myocardial cells indicate abnormal energy metabolism or myocardial ischemia.

During three years of follow-up, 87 percent of women without significant coronary artery disease and a normal spectroscopy study had no clinical cardiac events. In contrast, only 57 percent of patients without significant coronary artery disease and with an abnormal spectroscopy study were event free.

For every 1 percent decrease in the phosphocreatine/ATP ratio, the risk of a heart-related event increased by 4 percent. The higher clinical event rate was due primarily to hospitalization for unstable angina, which led to repeat cardiac catheterizations and increased health care costs.

The investigators concluded that the results are consistent with the concept that chest pain without coronary artery disease is a disorder that primarily affects women. Because spectroscopy detects intracellular metabolic activity, an abnormality in metabolism related to reduced blood flow in the myocardial circulation could underlie the disorder.

No standard approaches to therapy for this condition exist, said Gerald M. Pohost, MD, senior author of the study. Most of the patients do not have conventional risk factors associated with coronary disease, such as hypertension or abnormal cholesterol levels.

“Our results suggest that magnetic resonance spectroscopy will become an important test for evaluating patients who have anginal chest pain in the absence of coronary artery disease, as well as for other conditions,” said Pohost.

Chest pain without coronary artery disease remains a mystery in the cardiology field, Pohost said. Of the 534,000 women who had chest pain and coronary angiography in 2003, 300,000 (56 percent) do not have significant coronary artery disease. That’s compared to fewer than 20 percent of men.

Future studies will focus on trying to identify the underlying cause of the condition, which could lead to more effective treatment.