Women's Heart Advisor January 2012 Issue

You Can Lower Your Risk of Sudden Cardiac Death

Managing any heart arrhythmias, diabetes or other cardiac risk factors can help protect against this threat to postmenopausal women.

Most women are aware that their risk for heart attack increases after menopause. But a recent study found that many women with coronary artery disease (CAD) may actually be at even higher risk for a  different type of event called sudden cardiac death, or SCD. In a study of postmenopausal women published in the Archives of Internal Medicine  online on July 25, 2011, SCD was responsible for 54 percent of cardiac deaths and 27 percent of all deaths—a much higher percentage than expected.

SCD is Not a Heart Attack
A heart attack is caused when blood flow to the heart muscle is blocked by a clot or obstructive fatty plaque. SCD is different: It is generally caused by a malfunction of the heart’s electrical system that simply causes the heart to stop beating. Unless CPR or a defibrillator is used, death occurs within one hour.

Approximately 250,000 to 300,000 men and women in the U.S. die from SCD each year. Because it can occur in people who do not have advanced coronary artery disease, SCD is hard to predict. In fact, the only known predictor is a poor left ventricular ejection fraction (LVEF), a measure of pumping ability used in heart failure. Yet fewer than one-third of patients who die from SCD have ejection fractions low enough to consider an implantable defibrillator.

Women and SCD
Several large studies have found that women with SCD are less likely than men to have known cardiovascular disease or low ejection fractions. In the large Nurses Health Study, more than two-thirds of women with SCD had no history of heart disease. Other studies have shown that both traditional risk factors for CAD and nontraditional factors, such as depression, increase the risk of SCD in women.

However, little information was available on the risk factors for SCD specifically in women with CAD. The Archives study set out to fill this information gap.

In the study, researchers analyzed data from the 2,763 participants in the Heart and Estrogen/Progestin Replacement Study (HERS), a clinical trial investigating the cardiac effects of hormone replacement therapy (HRT) on postmenopausal women with CAD. Over the 6.8-year followup period, 136 of the 254 deaths from cardiac causes were attributed to SCD. There was no difference between the number of women who experienced SCD or any cardiac event among those assigned to HRT and those who received placebo, so HRT could not be blamed.

Which Factors Increase Risk
When the researchers examined the baseline characteristics of the participants, they discovered a close relationship between SCD and previous heart attack, heart failure, poor kidney function (glomerular filtration rate less than 40 mL/min/1.73 m2), atrial fibrillation, physical inactivity and diabetes. The presence of any risk factor doubled the risk of SCD: three or more risk factors increased the risk 10 times.

Although a low LVEF (less than 35 percent) is still considered the greatest risk factor for SCD, these risk factors were better predictors of SCD than LVEF alone and increased the risk in patients with low LVEF.

The authors hoped physicians will use this new finding to reinforce the need for women to remain active, control their diabetes and comply with medications given for heart attack and heart failure.