CABG Death Rates Vary

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CABG Death Rates Vary
November 27, 2008 (Atlanta, GA) — A new US study has found that sex differences in risk-adjusted death rates for coronary artery bypass grafting (CABG) surgery vary between so-called tier 1 hospitals--those that have the best performance on this outcome--and tier 4 hospitals, the worst-performing ones [ color="blue">1]. DrStevenDCuller (Emory University, Atlanta, GA) and colleagues report their findings in the November 24, 2008 issue of the ArchivesofInternalMedicine.

Women had a higher mortality rate than men overall, with the difference being much less in the better-performing hospitals. The study, which looked at Medicare beneficiaries, used a novel way of ranking hospitals based on the numbers of lives saved, and showed that those of either sex undergoing CABG in the typical top-tier hospitals were significantly less likely to die than those treated in institutions in the other 3 tiers.

Culler told heartwire: "Clearly, people have previously shown that some hospitals are better than other hospitals, and this research supports that. What we have found different is that the difference seems to matter by gender." He added: "What's stunning is that 75% of the observed deaths of either male or female Medicare beneficiaries treated in tier 4 hospitals could be avoided if tier 4 hospitals improved their performance to the average performance of top-tier hospitals."

The difference in average mortality rates across hospital tiers is substantially larger than the overall reduction in CABG mortality that has been achieved over the past decade with clinical advances in performance of the procedure, he added.

How many more times do we have to show that there are differences before we try to figure out why?

Culler believes that it is time to examine why these interhospital differences occur. "What are those top-tier hospitals doing in terms of process, doctor selection, operating-room procedures, etc, that are different from the bottom-tier ones? That's where future research really needs to be done. How many more times do we have to show that there are differences before we try to figure out why?"

In an invited commentary [ color="blue">2], DrsAdrianHernandez and SeanMO'Brien (Duke Clinical Research Institute, Durham, NC) question some of the methodology used by Culler et al, but nevertheless commend them for "bringing attention to the potential lives at stake when there is significant variation in quality of care."

"Striking" Difference Between Tier 1 and Tier 4 Hospitals

The study was a retrospective analysis performed using the US Medicare Provider Analysis and Review (MEDPAR) file of all Medicare beneficiaries who underwent CABG surgery without valve repair or replacement during the 2003 and 2004 fiscal years. Logistic-regression models controlling for demographic characteristics, comorbidities, and cardiac risk factors were used to predict the probability of inhospital mortality. Hospitals performing at least 52 CABG surgeries during a fiscal year (with at least 17 female patients) were ranked into 4 tiers, based on the number of lives saved, calculated as the expected number of risk-adjusted deaths minus the number of actual deaths in the hospital during each fiscal year.

The average risk-adjusted mortality rate (RAMR) was stable, and declined over the two years, from 3.68% in 2003 to 3.61% in 2004. In 2004, the average RAMR ranged from 1.39% in tier 1 hospitals to 6.40% in tier 4 hospitals.

Thus, the relative risk of mortality for CABG surgery in a bottom-tier hospital was 4.4 times that in a top-tier hospital, a finding that Culler etal describe as "striking."

Both male and female Medicare beneficiaries undergoing elective CABG surgery could improve their outcomes by carefully selecting their CABG hospital.

This is "a huge difference," said Culler. "You have a procedure with an average mortality of around 2.5%--two out of 100 patients die--so to lose 15 or save 15 lives [out of a 100] means you're really significantly different from the average. This gives you a way to understand, in layman's terms, how much the quality difference is in some of these hospitals."

Such research helps patients to better select hospitals, he added. "Both male and female Medicare beneficiaries undergoing elective CABG surgery could improve their outcomes by carefully selecting their CABG hospital."

Problem of Poor Performance Applies Equally to Both Sexes

The researchers also found that the sex-specific mortality rate was consistently higher for women in all tiers, with the smallest difference (0.68%) in tier 1 hospitals and the greatest difference (2.67%) in tier 4 hospitals.

So even in the best-performing hospitals, there is a sex differential in mortality rates, the researchers note, adding that this demonstrates the importance of examining hospital CABG outcomes in various subpopulations.

Nevertheless, they add, the "consistency of the sex-based mortality differences across tiers implies the quality problems of poor performers apply equally to male and female patients, especially since the difference in average RAMR between top-performing and lower-performing hospitals is greater than the sex difference in RAMR in the bottom two tiers."

What are the good hospitals doing, if they are consistently ranked at the top, that the bottom ones aren't?

"We really now need to see if we can identify what's different [in the bottom-tier hospitals]," said Culler. "Is it something to do with how the hospital operates: Safety, culture, or whatever you want to call it? What are the good hospitals doing, if they are consistently ranked at the top, that the bottom ones aren't?"

He cites the old adage: "Would you rather have the best doctor in the worst hospital or the worst doctor in the best hospital? I would argue that both are important."

He believes that at least some of this outcome comes down to the quality of the cardiovascular surgeon. "It's a profession that there is some ranking of skill across people that are performing at any time. The real issue is how many doctors are out there that are so good that they can do this procedure at the top-tier-hospital level? Is there a way to rank individual physicians? And are there enough of them that you can have high-quality providers in every one of these hospitals?"

Rankings Should Be Done Over Multiyear Periods

In their commentary, Hernandez and O'Brien say that several steps should be taken "to ensure that hospitals are classified appropriately with robust methodology and that adverse consequences of profiling are minimized."

Important among these is for hospitals to be classified over a multiyear period to provide greater stability in estimates of quality. Culler agreed, telling heartwire that his team has already started doing some groupings of 3 years of outcomes, "so now . . . most hospitals in the sample will have 600 to 1000 CABG procedures."

Hernandez and O'Brien add that significant incentives should be developed and tested to determine whether healthcare can be shifted from centers of convenience to centers of excellence. Culler doesn't necessarily agree with this.

"Many of our bottom-tier hospitals do more procedures than the average hospital in the top tier. It's not that they are not doing enough procedures, it's how they are doing them--they have worse results in both men and women."

"It would be great if you could take the surgical team from one of the best hospitals and put it in one of the worst hospitals to see if outcomes change. That would make it clear that it's not the methodology but that there are truly differences in the way that these groups of providers are performing these services."

  1. Culler SD, Simon AW, Brown PP, et al. Sex differences in hospital risk-adjusted mortality rates for Medicare beneficiaries undergoing CABG surgery. Arch Intern Med 2008; 168:2317-2322. Abstract

  2. Hernandez AF, O'Brien SM. Sex differences in hospital risk-adjusted mortality rates for Medicare beneficiaries undergoing CABG surgery--Invited Commentary. Arch Intern Med 2008; 168:2323-2325. Abstract


face="Verdana" size="1">The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.


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