Outcomes of PCI in Relation to Procedural Characteristics and Operator Volumes in the United States

Abstract

Background: Professional guidelines have reduced the recommended minimum number to an average of 50 percutaneous coronary intervention (PCI) procedures performed annually by each operator. Operator volume patterns and associated outcomes since this change are unknown.

Objectives: The authors describe herein PCI operator procedure volumes; characteristics of low-, intermediate-, and high-volume operators; and the relationship between operator volume and clinical outcomes in a large, contemporary, nationwide sample.

Methods: Using data from the National Cardiovascular Data Registry collected between July 1, 2009, and March 31, 2015, we examined operator annual PCI volume. We divided operators into low- (<50 PCIs per year), intermediate- (50 to 100 PCIs per year), and high- (>100 PCIs per year) volume groups, and determined the adjusted association between annual PCI volume and in-hospital outcomes, including mortality.

Results: The median annual number of procedures performed per operator was 59; 44% of operators performed <50 PCI procedures per year. Low-volume operators more frequently performed emergency and primary PCI procedures and practiced at hospitals with lower annual PCI volumes. Unadjusted in-hospital mortality was 1.86% for low-volume operators, 1.73% for intermediate-volume operators, and 1.48% for high-volume operators. The adjusted risk of in-hospital mortality was higher for PCI procedures performed by low- and intermediate-volume operators compared with those performed by high-volume operators (adjusted odds ratio: 1.16 for low versus high; adjusted odds ratio: 1.05 for intermediate vs. high volume) as was the risk for new dialysis post PCI. No volume relationship was observed for post-PCI bleeding.

Conclusions: Many PCI operators in the United States are performing fewer than the recommended number of PCI procedures annually. Although absolute risk differences are small and may be partially explained by unmeasured differences in case mix between operators, there remains an inverse relationship between PCI operator volume and in-hospital mortality that persisted in risk-adjusted analyses.

Keywords: bleeding; mortality; myocardial infarction; volume-outcome relationship.

Figure 1. Distribution of annual operator volumes

Operator volumes ranged from 1 to 1121 PCIs per year; the median operator performed 59 PCIs/year. Dashed lines separate operators into low- (< 50 PCIs/year, 4628 operators, 44%), intermediate- (50–100 PCIs/year, 3001 operators, 29%), and high- (> 100 PCIs/year, 2867 operators, 27%) volume operators.

Figure 2. Changes in annual operator volume over the study period

Stacked bar graphs depict the percentage of operators performing < 50, 50–100, and > 100 PCIs annually averaged over the 16 overlapping eight-quarter (two-years) intervals that comprised the study period. Between 43.7 and 44.8% of operators performed < 50 PCIs/year in each interval.

Figure 3. Median annual operator volumes by hospital referral region

Annual operator volumes varied by Dartmouth Health Atlas hospital referral region. In general, regions in the western and southwestern U.S. had the lowest median operator volumes (depicted in lighter purple); northeastern and midwestern regions had higher median operator volumes.

Central Illustration. Procedure Characteristics and In-Hospital Outcomes by Operator Volume

Nearly half of all operators were low-volume operators (performed < 50 PCIs/year). Compared with intermediate- (50–100 PCIs/year) and high- (> 100 PCIs/year) volume operators, low-volume operators worked at lower volume hospitals, performed more emergency PCIs and primary PCIs for STEMI, less frequently used radial access, used more radiographic contrast dye, and more fluoroscopy minutes. Though in-hospital mortality was low (1.6% overall), it was higher for low- and intermediate-volume operators than for high-volume operators.