Diagnostic-therapeutic cascade revisited: coronary angiography, coronary artery bypass graft surgery, and percutaneous coronary intervention in the modern era

BACKGROUND

There is wide geographic variation in the use of coronary revascularization in the United States. Rates are closely related to rates of coronary angiography. We assessed the relationship between coronary angiography and coronary artery revascularization by procedure type (coronary artery bypass graft surgery or percutaneous coronary intervention).

METHODS AND RESULTS

Using Part B claims for a 20% sample of the Medicare population, we calculated population-based rates of testing and treatment by region, using events identified in Part B claims as the numerator and the total number of Medicare beneficiaries residing in the area as the denominator and adjusting for regional differences in demographic characteristics with the indirect method. Cardiac catheterization rates varied substantially across regions, from 16 to 77 per 1000 Medicare beneficiaries. The relationship between coronary angiography rates and total coronary revascularization rates was strong (R(2)=0.84). However, there was only a modest association between coronary angiography rates and coronary artery bypass graft surgery rates (R(2)=0.41) with the suggestion of a threshold effect. The association between coronary angiography rates and percutaneous coronary intervention rates was strong (R(2)=0.78) and linear.

CONCLUSIONS

The diagnostic-therapeutic cascade for coronary artery disease differs by therapeutic intervention. For coronary artery bypass graft surgery, the relationship is modest, and there appears to be a testing threshold beyond which additional tests do not result in additional surgeries. For percutaneous coronary intervention, the relationship is very tight, and no threshold appears to exist. Given the results of recent studies of medical versus invasive management of stable coronary disease, patients living in high-diagnostic-intensity regions may be getting more treatment than they want or need.

Cardiologists performing peripheral angioplasties: impact on utilization

CONTEXT

Angioplasty and stent placement for peripheral arterial occlusive disease has traditionally been performed by radiologists and surgeons. However, cardiologists have recently begun to perform these procedures. It is unknown whether this has affected how often the procedure is done.

OBJECTIVE

To assess how the proportion of peripheral angioplastics performed by cardiologists in a geographic area relates to population-based angioplasty rates.

DESIGN

Cross-sectional analysis of all U.S. Medicare beneficiaries undergoing peripheral arterial (i.e., renal, iliac, or lower extremity) angioplasty in 1996 using Part B (physician) claims for cardiovascular procedures. Physician specialty was obtained from the American Medical Association's masterfile and Medicare.

MEASURES

For each of the 306 U.S. hospital referral regions (HRRs), we calculated the proportion of procedures performed by cardiologists and rates of peripheral arterial angioplasty (adjusted for age, sex, and race).

RESULTS

More than 37,000 peripheral arterial angioplastics were performed on Medicare beneficiaries in 1996 (50% for lower extremity, 33% iliac, and 17% renal arterial disease). Cardiologists performed 26% of these procedures overall, including 37% of the renal angioplastics. Few (12%) procedures were done as part of a cardiac catheterization; instead, most were done as a separate procedure. Use of peripheral angioplasty varied more than 14-fold across HRRs (median, 12 procedures per 10,000 beneficiaries; 10th to 90th percentile, 4.1 to 57.9). The mean angioplasty rate in HRRs where cardiologists performed 50% or more of the procedures was almost double that of regions where they performed none (21.9 vs. 12.1 procedures per 10,000 beneficiaries; P < 0.001).

CONCLUSIONS

Cardiologists are performing a substantial proportion of peripheral angioplasties. Rates of these procedures are highest in regions where cardiologists do most of the angioplasties.

Relation between operator and hospital volume and outcomes following percutaneous coronary interventions in the era of the coronary stent

CONTEXT

Studies have found an association between physician and institution procedure volume for percutaneous coronary interventions (PCIs) and patient outcomes, but whether implementation of coronary stents has allowed low-volume physicians and centers to achieve outcomes similar to their high-volume counterparts is unknown.

OBJECTIVE

To assess the relationship between physician and hospital PCI volumes and patient outcomes following PCIs, given the availability of coronary stents.

DESIGN, SETTING, AND PARTICIPANTS

Analysis of data from Medicare National Claims History files for 167 208 patients aged 65 to 99 years who had PCIs performed by 6534 physicians at 1003 hospitals during 1997. Of these procedures, 57.7% involved coronary stents.

MAIN OUTCOME MEASURES

Rates of coronary artery bypass graft (CABG) surgery and 30-day mortality occurring during the index episode of care, stratified by physician and hospital PCI volume.

RESULTS

Overall unadjusted rates of CABG during the index hospitalization and 30-day mortality were 1.87% and 3.30%, respectively. After adjustment for case mix, patients treated by low-volume (<30 Medicare procedures) physicians had an increased risk of CABG vs patients treated by high-volume (>60 Medicare procedures) physicians (2.25% vs 1.55%; P<.001), but there was no difference in 30-day mortality rates (3.25% vs 3.39%; P =.27). Patients treated at low-volume (<80 Medicare procedures) centers had an increased risk of 30-day mortality vs patients treated at high-volume (>160 Medicare procedures) centers (4.29% vs 3.15%; P<. 001), but there was no difference in the risk of CABG (1.83% vs 1. 83%; P =.96). In patients who received coronary stents, the CABG rate was 1.20% vs 2.78% for patients not receiving stents, and the 30-day mortality rate was 2.83% vs 3.94%. Among patients who received stents, those treated at low-volume centers had an increased risk of 30-day mortality vs those treated at high-volume centers, whereas those treated by low-volume physicians had an increased risk of CABG vs those treated by high-volume physicians.

CONCLUSION

In the era of coronary stents, Medicare patients treated by high-volume physicians and at high-volume centers experience better outcomes following PCIs.

Variation in the use of laparoscopic cholecystectomy for elderly patients with acute cholecystitis

HYPOTHESIS

There is regional variation in the use of laparoscopic cholecystectomy (LC) for acute cholecystitis in the New England (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut) Medicare population.

DESIGN

Population-based, cross-sectional study.

SETTING

Hospital service areas (HSAs), small geographic areas reflecting local hospital markets, in New England.

PATIENTS

We identified from the claims database 21 570 Medicare patients undergoing cholecystectomy between 1995 and 1997. Patients with acute calculous cholecystitis but no bile duct stones (n = 6156) were then identified using International Classification of Diseases, Ninth Revision diagnostic codes. To reduce variation by chance, we excluded patients residing in HSAs with fewer than 26 cases, leaving 5014 patients in 77 HSAs.

MAIN OUTCOME MEASURES

For each HSA, we assessed the rate of cholecystectomies performed laparoscopically, mortality, and hospital length of stay.

RESULTS

Overall, 53.5% of patients with acute cholecystitis underwent LC. There was wide regional variation in the rate of patients undergoing laparoscopic surgery, from 30.3% in the Salem, Mass, HSA to 75.5% in the Hyannis, Mass, HSA. Seventeen HSAs had rates below 40%, while 9 had rates above 70%. The average length of stay (7.6 days) was approximately 1 day shorter in HSAs with high rates of patients undergoing LC than in other HSAs. There was no correlation between regional use of laparoscopic surgery and 30-day mortality (3.1% overall).

CONCLUSIONS

The likelihood of elderly patients with acute cholecystitis receiving LC depends strongly on where they live. Efforts to reduce regional variation should focus on disseminating techniques for safe LC in this high-risk population.