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Faster door-to-balloon times and better adherence to guidelines at hospitals with a high volume of angioplasties don't translate to better early survival, a registry study revealed.

Hospitals that did more than 70 primary percutaneous coronary interventions (PCI) each year did not have lower inhospital mortality rates compared with lower volume hospitals, (multivariate adjusted P=0.38 to P=0.49), found Deepak L. Bhatt, MD, MPH, of Brigham and Women's Hospital in Boston, and colleagues.

This was surprising given the faster door-to-balloon times and greater use of evidence-based therapies at high volume centers reported by Bhatt's group in the Nov. 25 issue of the Journal of the American Medical Association.

Prior studies have suggested that these quality measures do improve outcomes, so the study may simply have included too few truly low-volume centers or had too short a follow-up period, the researchers cautioned.

But the results were reassuring given that more than a third of U.S. hospitals participating in the American Heart Association's Get with the Guidelines initiative performed angioplasty despite not meeting the recommended 36 primary angioplasties per year threshold for volume, the researchers wrote.

These results don't mean volume doesn't matter at all, nor do they discount guidelines for procedural volume or door-to-balloon time, cautioned Issam D. Moussa, MD, of New York-Presbyterian Hospital in New York City, who wasn't involved in the study.

There were too many statistical and design issues for the observational study to change the guidelines, although "certainly it's enough to revisit the issue," said Moussa, a spokesperson for the Society for Cardiovascular Angiography and Interventions.

Bhatt agreed that volume is important, just not across the ranges seen in contemporary practice in hospitals actively pursuing quality improvements like those in the study, he said.

The number of procedures performed is increasingly being used as a surrogate for quality of care, with some organizations refusing to contract care for their employees to hospitals that don't meet this standard, Bhatt's group noted.

"Our study makes a case against such volume criteria," they wrote.

Angioplasty volume was an important predictor in older published registry studies in ST-segment elevation MI (STEMI), but times have changed, they said.

Improvements in angioplasty techniques and adjunctive pharmacotherapy, such as regular use of stents and routine dual antiplatelet therapy, over the past few years have seen significant standardization nationwide, with evidence-based therapies much more widely adopted and practiced, Bhatt's group said.

The same kind of standardization in surgery erased the significance of hospital surgical volume in mortality as well, they noted.

In that sense, the Get With the Guidelines campaign appears to have been a success in angioplasty, Moussa commented.

To see what effect volume has in contemporary practice, Bhatt's group analyzed data on 29,513 STEMI patients who had primary angioplasty recorded in the AHA's Get With the Guidelines-Coronary Artery Disease registry from 2001 through 2007.

These procedures were performed at 166 angioplasty-capable hospitals across the country, which had primary angioplasty volumes ranging from nine to 225 per year.

Overall, 65% of the centers met the minimum 36-procedure threshold recommended by the AHA and American College of Cardiology.

Compared with centers that fell under the threshold and those with an intermediate 36-to-70 volume, hospitals in the highest tertile with more than 70 procedures annually had the lowest door-to-balloon times (88 minutes versus 98 and 90, P<0.001 for trend).

After adjustment for patient and hospital characteristics, medium-volume hospitals remained just as likely to achieve the recommended door-to-balloon time of 90 minutes or less (P=0.79), although the same was not true for low-volume hospitals (odds ratio 0.72, P=0.03).

Full adherence to "key" quality of care measures -- acute use of aspirin and beta-blockers, discharge prescription for aspirin and beta blockers, lipid-lowering therapy when needed, ACE inhibitors or angiotensin-receptor blockers for eligible patients, and counseling on smoking cessation -- was less common at low-volume versus high-volume hospitals (OR 0.68, P=0.02), as was most of its components.

But medium-volume centers were no less likely to perform any quality of care measure than high-volume centers.

Among the outcomes, length of stay was similar between all three groups (P=0.13 for trend).

Inhospital mortality rates were 3.9% in low volume facilities, 3.2% with medium volume, and 3.0% in high volume hospitals (P=0.26 low versus high and P=0.99 for medium versus high).

The mortality differences remained insignificant through sequential multivariable analysis, when considering volume as a continuous variable (P=0.95), and regardless of the thresholds used.

In addition to statistical underpowering for the high versus low comparison, the researchers also noted that the study was limited by use of voluntarily submitted data from medical chart review at hospitals actively engaged in quality improvement without a control set or data on individual operator volume.

"It is conceivable that low-volume hospitals may be performing as well as other hospitals because they have one or two high-volume operators," Bhatt's group concluded.

Also, patients treated at low-volume centers appeared to be younger and less sick -- factors that multivariate analysis likely couldn't completely account for, Moussa said. "They are fundamentally different patients."

Further studies are needed to corroborate the results with longer-term follow-up and in cohorts treated with stents and newer adjunctive therapies, the researchers said.

Despite the caveats, AHA spokesperson Alice Jacobs, MD, of Boston University, said that ACC/AHA guidelines committees will review the new evidence to determine whether a change in the volume recommendations for the performance of primary angioplasty is warranted.

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