ICDs are devices used to help prevent death from arrhythmias, a change from the normal sequence of electrical impulses, causing abnormal rapid and irregular heart rhythms.
DEFINITE, a trial of 458 patients, showed women had higher rates of death from all causes after ICD placement. But new analysis showed this was due to an increase in non-cardiovascular causes of death.
This study is good news for women, because initial results from the DEFINITE trial (Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation) did not show a survival benefit from ICD placement in women with this type of heart failure. However, after further analysis, researchers believe ICDs did prevent death from arrhythmias.
"Initially we observed that in women there did not seem to be a survival benefit from ICD placement," said Alan Kadish, M.D., professor of medicine, Feinberg School of Medicine, Northwestern University in Chicago, Ill. "We were concerned about that and wanted to look more closely. What we found is that ICD placement in women did prevent death from arrhythmias."
Kadish said that a significant number of women died from miscellaneous causes such as heart failure not due to arrhythmia, cancer, infection and stroke. "None of these appeared to be a complication of defibrillator placement," he said. "It appears to be a statistical aberration; a matter of bad luck in a small number of patients."
Although further study is warranted, women with this type of heart failure should be offered an ICD to prevent death from life-threatening heart rhythms, he said. "The reason for the lack of perceived benefit was not because the ICD was not working," Kadish said. While ICD implantation did not reduce overall death in women, it did prevent arrhythmic death, he said. "We need more work to prove that prevention with ICD placement is as beneficial in women as men. But we suspect that it is," Kadish said.
All enrolled patients had mild to moderately severe cardiomyopathy with lowered left ventricular function due to non-ischemic heart failure. Patients were randomized to standard medical drug therapy including ACE (angiotensin converting enzyme) inhibitors and beta blockers or standard drug therapy plus ICD placement. Another 240 patients, who refused participation or had medical reasons for not being enrolled, were placed on a registry to be followed. All were followed for 2.5 years.
Cardiomyopathy is a disease of the heart muscle that causes the heart to become bigger and weaker. The heart loses its ability to pump blood and, in some instances, heart rhythm is disturbed, leading to irregular heartbeats. The most common cause is narrowed arteries that feed the heart, called ischemic cardiomyopathy. However, the heart failure in this group of patients was not due to a lack of blood flow but to various factors such as infections (mostly viral), heredity, alcohol abuse, toxins, and other medical conditions.
The researchers tried to recruit an equal number of men and women, but only about 29 percent of patients in the treatment group were women, and only approximately one-fourth of those in the registry were women. "This indicates that the disease may be more common in men," Kadish said.
The researchers found there was a significant reduction in arrhythmic death in patients who received an ICD, but deaths from all causes were reduced only in men. Men had a 40 percent reduction in death from all causes, while women had no reduction.
The researchers also found that women had a higher incidence of non-cardiac deaths than men. Of the 11 women who died in the ICD group, 73 percent of the deaths were not due to heart problems. In contrast, only 47 percent of the 17 male deaths in the ICD group were due to non-cardiac causes.
Women were more often non-white than men (42 percent vs. 29 percent), but no significant differences existed in age, heart failure class or left ventricular ejection fraction due to sex.
None of the women receiving ICDs died from arrhythmia, the most common cause of death in this type of heart failure. Yet, four women in the standard therapy treatment group (those without ICDs) died from arrhythmia.
In men, three patients receiving ICDs died from arrhythmia, while 10 in the standard therapy died.
The study was not designed to look at men and women separately. However, there is strong "confirmatory evidence that the ICD should be placed in men and women" with non-ischemic cardiomyopathy. "The level of evidence is less in women than in men, but in the interim they should not be treated any differently," Kadish said.
Co-authors are Rebecca J. Quigg, M.D.; Andi Schaechter, B.S.N.; Haris Subacius, M.A.; Adam Howard B.S.; Alaa Shalaby, M.D. and N.A. Mark Estes, M.D.
Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position. The American Heart Association makes no representation or warranty as to their accuracy or reliability.