BOSTON—Women with ischemic heart disease on defibrillator therapy were half as likely as their male counterparts to develop arrhythmic events, regardless of the device implanted, according to a study presented May 9 at the 33rd annual scientific sessions of the Hearty Rhythm Society (HRS). In addition, nonischemic women who received cardiac resynchronization therapy (CRT-D) fared better than nonischemic women who received only implantable cardioverter-defibrillators (ICDs).
Christine Tompkins, MD, of the electrophysiology division at the University of Rochester School of Medicine in Rochester, N.Y., and colleagues used data from the MADIT-CRT study (Multicenter Automatic Defibrillator Implantation Trial – CRT) to evaluate the influence of gender on arrhythmic events. MADIT-CRT originally was designed to assess whether the use a combined ICD-CRT-D would reduce the risk of heart failure and mortality in patients with New York Heart Association Class I and II ischemic cardiomyopathy and Class II nonischemic cardiomyopathy.
“Our initial hypothesis was that women were going to experience less appropriate device therapies for VT [ventricular tachycardia]/VF [ventricular fibrillation] than men,” Tompkins told Cardiovascular Business in an interview.
For their study, they evaluated cardiac arrhythmia rates—defined as the development of VT/VF—or all-cause death in 1,790 patients (1,346 men and 444 women) who were treated with defibrillator therapy and who had documented follow-up in a three-year period.
They found that overall 16.4 percent of the women and 28.2 percent of men experienced VT/VF or death over the three-year period. An analysis of ischemic patients showed that in women with ICD only, the crude event rate was 17 percent vs. 31.8 percent for men, while the rate for CRT-D was 14.9 percent for women vs. 28.2 percent for men. The type of device did not affect outcomes, according to Tompkins.
“Clearly there is something protective about being female,” Tompkins said in reference to women with ischemic heart disease.
In an analysis of crude rates for VT/VF or death, with ICD only nonischemic patients, the event rates for women and men were not statistically different. “There is something inherently different about arrhythmia genesis in women who have ischemic heart disease compared with women with nonischemic heart disease,” Tompkins said.
She suggested that one theory is based on estrogen-mediated effects on cardiac ion channels, specifically a potassium channel that plays in important role during ischemic reperfusion injury.
But in that same nonischemic population, the event rates in women dropped from 22.2 percent with ICD only to 13.2 percent in the presence of CRT-D while in the men it dropped from 27 percent with the ICD only to 24.6 percent with CRT-D.
“Women responded quite well to CRT-D,” Tompkins said, adding that those findings are consistent with earlier research by Arshad et al (J Am Coll Cardiol;57:813-20). “Then that improvement translated into reduced arrhythmic events.”
The researchers concluded that women with ischemic cardiomyopathy had a lower risk of arrhythmic events than did ischemic men and nonischemic men and women. Women tended to have a greater risk reduction with CRT-D than did men.