A unique pacemaker coupled with an implanted defibrillator benefits women with a specific kind of heart failure particularly well, according to new studies. However, it’s important to get the word out that women often don’t fit inside traditional treatment envelopes.
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Even though women do especially well with cardiac resynchronization therapy devices combined with an implanted defibrillator (CRT-D), existing guidelines are based on male physiology, so some women don’t receive treatment.
Experts now realize how important it is to tailor treatment criteria separately for men and women in order to ensure women receive the treatments they need.
Your heart’s messaging system
Your heart receives and processes electrical signals that keep it beating steadily and efficiently. Sometimes problems occur that interfere with that communication system. One type of signal problem is called left bundle branch block, (LBBB), which desynchronizes the pumping action of the heart.
Every heartbeat leaves an electronic signature which is recorded on an ECG. Physicians and pacing specialists interpret this for clues about your heart’s health. Among many other elements, the QRS complex interval helps experts determine whether or not you could benefit from CRT-D. The QRS interval refers to the tracing of waves on an electrocardiogram. Doctors consider CRT-D treatment if a patient has LBBB and a longer than normal QRS interval. The trouble is, women naturally tend to have shorter QRS intervals than men, so they don’t qualify under established guidelines for treatment.
Timing is off for women heart patients
Cardiac electrophysiologist Niraj Varma, MD, PhD has studied this issue. He says there’s a treatment gap regarding CRT-D and women because researchers focused more on men when they originally studied the treatment. “Women have been underrepresented in most ICD (implantable cardioverter defibrillator) and CRT trials. We know that for many reasons, women may fare better with CRT than their male counterparts,” he says.
One of the difficulties that women face in seeking treatment is that they more often have shorter QRS intervals than men. This difference is due to physiology and has little to do with the progress of any disease.
Current standards specify that patients with mild heart failure and a QRS interval of at least 150 milliseconds qualify for CRT-D treatment.
An unintended consequence of this biological difference is that many women fall under the 150-millisecond cutoff for CRT-D therapy treatment. Researchers established the 150-millisecond benchmark after studying many male subjects. Few if any women participated in any protocol studies.
Study: Women need separate treatment guidelines
Dr. Varma recently published results of a study about this issue. “Current guidelines which are based on QRS dichotomization, may exclude women because their QRS duration has to be interpreted differently,” he says.
To resolve some of these uncertainties, the study examined congestive heart failure CRT experience over the last decade, controlling for other factors in an equally weighted comparison between men and women with significant (Class III) heart failure and LBBB.
Dr. Varma says the results confirmed that the treatment response relationship is better described by a sex-specific factor and not by the 150 millisecond guideline. “Any single QRS value has different implications between genders,” he says. “Exercising QRS dichotomization by 150 milliseconds for CRT prescription according to current guidelines, though effective in men, denies therapy to a large contingent of appropriate female patients.”
Meta study confirms CRT-D benefit for women
In a subsequent meta study of completed research, the Center for Devices and Radiological Health of the U.S. Food and Drug Administration also found that women who had mild heart failure benefited from CRT-D therapy more than their male counterparts and that these women benefited even though they had a QRS interval of less than 150 milliseconds.
Women with LBBB and a QRS interval between 130 and 149 milliseconds had a significant (76 percent) reduction in death or heart failure. These are women who fall below the current guidelines and who otherwise might have died or suffered more serious heart failure.
What this means for you
The message learned is that certain standards cannot apply across gender lines and that women need individual heart studies and treatment protocols. You can find out if you would benefit from CRT-D and other therapies by taking a short health quiz online and then following up with your physician.