March 23, 2010 (Atlanta, Georgia) — An unexplained bias against sending women to the cath lab may be the reason women are about twice as likely as men to die within a month of an MI, a study from the European Cardiology Audit and Registration Data Standards (CARDS) data set shows.
A propensity-matched analysis of over 3000 MI patients showed that differences between the drug therapies given to men and women in the study--including aspirin, clopidogrel, beta blockers, and statins--could be explained by differences in baseline characteristics. However, gender differences in the application of invasive treatments such as angioplasty and thrombolysis could not be explained by differences in baseline characteristics. Therefore, the apparent reluctance of the doctors in the study to send women to the cath lab represents "an unrecorded bias," lead investigator Dr François Schiele (University Hospital of Besançon, France) concluded during his presentation of the study results on March 16 at the American College of Cardiology (ACC) 2010 Scientific Sessions.
Furthermore, comparison of men and women matched on baseline characteristics and treatments shows similar in-hospital and 30-day mortality between genders. "That suggests--although it does not prove--that a higher use of invasive procedures and perfusion strategies in women could reduce their mortality," Schiele said.
The researchers analyzed data from 3510 MI patients (32% women) in the CARDS data set in 2006 and 2007. The unadjusted data showed that women admitted for MI were, on average, nine years older than men, had more health problems, received fewer effective treatments for heart attack, and were nearly twice as likely to die, both during the initial hospital stay (9.7% vs 5%) and within 30 days (12.4% vs 7%).
The researchers created a set of 649 matched pairs of men and women based only on their baseline characteristics and then a set of 584 pairs matched both by their characteristics and the treatments they received.
Analysis of the group matched on characteristics found that men were 57% more likely than women to undergo coronary angiography, and men suffering an ST-elevation MI (STEMI) were 72% more likely to be treated with thrombolysis and 24% more likely to be treated with a percutaneous intervention than comparable women. The in-hospital and 30-day mortality rates were lower in men than in women, a difference of 48% and 30%, respectively.
In the second group of pairs, matched on both clinical characteristics and treatments, there were no statistically significant differences in mortality rates between genders, suggesting that when a woman does get the same therapy as a comparable male patient, her chances of survival are the same.
Schiele suggested that doctors may be "reluctant to use angiography in older women because they expect it to be [technically] more difficult [to treat invasively]."
Commenting on the study at the ACC meeting, Dr Rita Redberg (University of California, San Francisco) agreed that the treatment gap between men and women shown in the study could be caused by the perception among interventionists that their female patients are more likely to have complications with thrombolysis or angioplasty. She pointed out that "there are pretty consistent data that women have higher rates of procedural complications and higher rates of bleeding complications than men. That could be limiting some of the invasive treatments we are seeing."
Schiele acknowledged that women are at higher risk for complications, "but maybe with better stents for small arteries and radial access and better antithrombotic regimens, we could safely increase the rates of angioplasty and angiography in women," he said.
Redberg also pointed out that the mortality gap between men and women was especially high among younger patients, perhaps suggesting that younger women are susceptible to an especially "virulent" form of coronary disease, just as breast cancer tends to be more aggressive in younger patients. However, Schiele said the current study is not powered to compare only younger patients, so that question will have to be left to a future trial.
Evidence from another trial presented at the ACC suggests that interventionalists' attempts to improve therapy among women are making progress. Data from the Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles in CAD (SPARC) registry of US patients with no history of heart disease presenting with chest pain examined with advanced imaging found that about twice as many women were referred to the cath lab, and even after adjustment for age, diabetes, test result, type of imaging test, and chest pain, female gender remained a significant predictor of referral to cardiac catheterization.
