Volume Outcome Relationships in the Stent Era
Abstract & Commentary
By Michael H. Crawford, MD Dr. Crawford is Professor of Medicine, Chief of Clinical Cardiology, University of California, San Francisco and Editor of Clinical Cardiology Alert. Dr. Crawford is on the speaker's bureau for Pfizer.
Source: Hannan EL, et al. Volume-Outcome Relationships for Percutaneous Coronary Interventions in the Stent Era. Circulation. 2005;112:1171-1179.
Volume outcome data for percutaneous coronary interventions (PCI) was largely collected and reported in the balloon angioplasty era. Thus, this report from New York state's PCI reporting system from 1998 to 2000 is of interest. This database of over 100,000 cases, which can be adjusted for severity of illness, was interrogated for 3 outcomes: in-hospital mortality, same-day coronary artery bypass surgery (CABG), and same-stay CABG. The interaction of these 3 outcomes and volume was assessed by examining 3 institutional PCI volume thresholds (400, 500, and 600 per year) and 3 operator volume thresholds (75, 100, and 125 per year). The hospital volume threshold with the greatest odds ratio (OR) for death was 400. Hospitals doing < 400 PCIs per year had an OR of 1.98 for mortality vs those with > 400 per year (95% CI, 1.17-3.35). Same-day CABG was also more likely in the <400 PCI hospitals (OR, 2.07, 1.36-3.15), as was same-stay CABG (OR 1.51, 1.03-2.21). By contrast, mortality was not different based upon operator volume thresholds, but same-day CABG surgery (1.65, 1.05-2.6), and same-stay CABG (1.55, 1.10-2.18) were using the 75 threshold. The only significant interaction between hospital and operator volumes was mortality at a hospital volume of < 400 and operator volume at < 75. Hannan and colleagues concluded that high volume hospitals and operators continue to have better PCI outcomes in the stent era.
Commentary
In 1993, the infamous ACC/AHA Guidelines came out recommending the 75 procedures a year threshold for maintaining one's skills to do PCI. This caused a great hue and cry from the small volume operators who sported buttons with a 75 crossed by the encircled red slash mark at the next ACC annual meeting. Their strongest argument against the need for high volumes was in the West where large volume hospitals can be very far away, eg, somewhere in Wyoming to Denver. They argued that it was better to treat the patient in Wyoming by a low volume operator than risk the transfer to Denver. Also, they argued that quality does not always equate with volume. Indeed, I observed one operator who did 100 balloon angioplasties over about 2 years with no serious complications, but he only selected slam dunk cases. Obviously, there are many variables that go into quality work, including innate skill, judgment, quality of training, case selection, and ancillary therapy. In this report there was no difference in morality above or below 75 procedures. Also, another study has shown that the volume threshold may be as low as 30 per year. This study did not test levels below 75. So, insisting on a minimum of 75 cases per year is difficult to support today.
Hospital volume seems to be another issue. In this report it was significantly different, especially above and below 400 per year. However, the absolute event rates are small: The mortality rate in < 400 hospitals was 1.23% vs 0.78% in > 400 hospitals; an absolute difference of about one-half a percent. The rate of same-day CABG was 0.57% < 400 and 0.30% in > 400 hospitals; an absolute difference of about a quarter of a percent. Yet the authors estimated, based upon this data, that if all PCIs in New York were done in > 400 hospitals, the death rate would decline 50% and the same-day CABG rate 34%. It would appear that a high volume center can impact individual operator results because of the value of a well-trained, experienced staff. This is hard to argue with. However, other studies have shown that the threshold could be as low as 200 per year. In this study a lower volume threshold was not assessed. Clearly, there is some number below which quality begins to suffer. This study defined that level as 400. It is certainly < 200, but may be as high as 400.
The major weakness of this study is that because of the influence of the ACC/AHA guidelines, there were few New York operators with < 75 cases per year (7%) and few hospitals with < 400 per year (2.3%). A higher number of low volume operators and hospitals may have shown a different result. An interesting feature of the study is that the PCI mortality rate has decreased, as compared to older balloon angioplasty studies from 0.9% to 0.8%, but more impressively same-day CABG has decreased from 3.43% to 0.91%. Thus, stents have made a big difference in the short-term results of PCI.
Volume outcome data for percutaneous coronary interventions (PCI) was largely collected and reported in the balloon angioplasty era. Thus, this report from New York state's PCI reporting system from 1998 to 2000 is of interest. This database of over 100,000 cases, which can be adjusted for severity of illness, was interrogated for 3 outcomes: in-hospital mortality, same-day coronary artery bypass surgery (CABG), and same-stay CABG.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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