Measuring the levels of sex hormones in blood may identify those likely to suffer a sudden cardiac arrest, a heart rhythm disorder that is fatal in 95 per cent of patients, scientists, including one of Indian-origin, have found.
Researchers found that lower levels of testosterone, the predominant male sex hormone, were found in men who had a sudden cardiac arrest.
Higher levels of estradiol, the major female sex hormone, were strongly associated with greater chances of having a sudden cardiac arrest in both men and women.
"Because sudden cardiac arrest is usually fatal, we are constantly looking for ways to predict which patients are susceptible so we can concentrate on prevention," said Sumeet Chugh, director of the Heart Rhythm Center in the Cedars-Sinai Heart Institute and the Pauline and Harold Price Chair in Cardiac Electrophysiology Research.
"If we wait until someone has a sudden cardiac arrest, it is usually too late for treatment," Chugh said.
Unlike heart attacks (myocardial infarction), which are typically caused by clogged coronary arteries reducing blood flow to the heart muscle, sudden cardiac arrest is the result of defective electrical impulses.
Patients may have little or no warning, and the disorder usually causes nearly instantaneous death. Every year, up to 5 million worldwide die from sudden cardiac arrest.
"This is the first time it has been reported that there is an association between sex hormone levels and sudden cardiac arrest," said Chugh.
"While these findings need to be confirmed by other studies, they suggest that higher testosterone levels in men may offer protection from sudden cardiac arrest and lower levels of estrogen may protect both men and women," he said.
Researchers measured blood hormone levels in 149 patients who had a sudden cardiac arrest, comparing them with levels in 149 patients who had coronary artery disease but did not have sudden cardiac arrest.
They found that men who had sudden cardiac arrests had testosterone levels of 4.4 nanogrammes per millilitre, compared to 5.4 nanogrammes per millilitre for men who did not have sudden cardiac arrest.
Men who had sudden cardiac arrest had estradiol levels of 68 picogrammes per millilitre, compared to 52 picogrammes per millilitre for men who did not have sudden cardiac arrest.
Women who had sudden cardiac arrest had estradiol levels of 54 picogrammes per millilitre, compared to 36 picogrammes per millilitre for the control group.
The study was published in the journal Heart Rhythm.
