Heart Failure Therapy Benefits Women More Than Men?
But study finds they're less likely than males to receive pacemaker that synchronizes heartbeats
Current guidelines call for the use of CRT in patients with a "QRS duration" of 150 milliseconds or longer. QRS duration is the time required for electrical conduction in the heart, and longer times indicate delayed electrical function.
But the FDA analysis found that women with a QRS of 130 to 149 milliseconds enjoyed a substantial benefit from CRT that men with that same QRS did not. When provided at that range, CRT reduced women's risk of heart failure or death by 76 percent, but provided no benefit to men.
"Women actually respond reasonably well, even when their QRS duration is anywhere from 129 to 149 milliseconds," Tomaselli said.
Differences in women's physiology and the way they experience heart disease likely explain why they are better served by cardiac resynchronization therapy, Strauss and Tomaselli said.
Women's hearts are smaller, which means that even shorter delays in their QRS duration could have a more negative impact on their heart, Tomaselli said.
"One can imagine that in women, a time delay of 140 milliseconds in an overall smaller heart might be a reflection of more dyssynchronous contraction than in a man with the same QRS delay," he said.
Women also are more likely than men to have heart failure that is not related to a prior heart attack, Strauss said. Patients who have not had a heart attack are more likely to benefit from CRT.
In addition, FDA researchers found that women are more likely than men to suffer the specific heart problem that CRT best helps, an electrical disorder called left bundle branch block.
"In left bundle branch block, there is a large delay between the pumping of the different walls of the heart," Strauss said. "CRT fixes this problem by correcting this delay and causing the heart walls to move at the same time again."
About 85 percent of women in the clinical trials had left bundle branch block, compared with 68 percent of men, the analysis showed.
These findings highlight the importance of enrolling more women in clinical trials and performing gender-specific analysis of the benefits, Strauss said.