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High-volume angioplasty centers associated with better adherence to evidence-based guidelines
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High-volume angioplasty centers were more likely to have shorter door-to-balloon times and to give patients guideline-recommended medications when compared with lower-volume centers, study results suggested.
Researchers examined observational data from 29,513 patients presenting with STEMI who underwent primary angioplasty. Among those, 3,900 patients were treated in low-volume centers, 9,008 in medium-volume centers and 16,605 in high-volume centers. The primary outcome measures were door-to-balloon time, length of hospital stay, adherence to evidence-based quality of care measures and in-hospital mortality.
Overall in-hospital mortality among all centers was 3.2% (3.9% low-volume; 3.2% medium-volume; 3% high-volume), and unadjusted and adjusted analyses of in-hospital mortality suggested no difference among the treatments groups. High-volume centers had better door-to-balloon times (88 minutes) than low-volume centers (98 minutes) and medium-volume centers (90 minutes; P<.001 for trend). Medium-volume hospitals but not low-volume hospitals were more likely to reach a door-to-balloon time of 90 minutes or less. Low-volume centers were less likely to prescribe aspirin (OR=0.46; 95% CI, 0.28-0.78); lipid-lowering therapy in patients with LDL >100 mg/dL (OR=0.65; 95% CI, 0.44-0.97); and ACE inhibitors and angiotensin receptor antagonists (OR=0.79; 95% CI, 0.62-1.00). They were also less likely to counsel current smokers regarding cessation compared with high-volume centers, according to the researchers.
Kumbhani D. JAMA. 2009;302:2207-2213.
Contrary to previous reports, the results of this study show that the annual primary angioplasty volume of a given hospital does not affect the rate of in-hospital mortality for patients with acute MI. Specifically, these results tell us that the in-hospital outcome of patients with acute MI would be the same whether the patient was treated in a hospital that does only one primary angioplasty every month or in a hospital that does 18 primary angioplasties every month.
The results of this study should be viewed in a positive perspective, noting the overall low in-hospital mortality for patients undergoing primary percutaneous coronary intervention for acute MI even in low-volume centers. However, this study has several important limitations that make it inadequate to cause any changes in the existing guidelines that set minimal procedural volume for hospitals that do primary PCI.
First, the database used to perform this study depends on voluntary reporting. This means that hospitals can select which procedures to report and can underreport if they choose to (although this is a discouraged practice). In fact, the researchers of this study excluded 122 hospitals from the analysis because of potential underreporting (more than 30 patients during six years). This potentially means that other hospitals in the study could also be underreporting procedures with unfavorable outcomes. Underreporting will have a greater effect in low-volume centers.
Another limitation was that many patients were excluded from the analysis because they were “transferred out” to other centers. This is a common practice in low-volume centers where high-risk and sicker patients are triaged to high-volume centers. The selection bias based on hospital volume is also clear from the fact that patients in the low-volume centers were younger and had lower frequency of congestive HF, prior MI, peripheral arterial disease and chronic obstructive pulmonary disorder compared with high-volume centers. Although risk adjustment using standard statistical techniques is commonly used to equalize the playing field, it remains inadequate to eliminate these fundamental differences among patients in the various study groups.
Finally, even if we accept the results for what they are, there was a 0.9% absolute reduction in mortality in high-volume centers compared with low-volume centers. The fact that this difference did not reach statistical significance may be simply due to the small number of patients in the low-volume centers. The researchers themselves highlight the fact that approximately 7,000 patients will be needed in the low-volume group (instead of 3,000 patients) to have power to show a statistical difference in mortality.
– Issam D. Moussa, MD
Associate Professor
of Medicine,
Director of Endovascular Service,
Weill Medical College of
Cornell University