Effect of operator and institutional volume on clinical outcomes after percutaneous coronary interventions performed in Canada and the United States: A brief report from the Enhanced Suppression of the Platelet glycoprotein IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) study
M Madan, J Nikhil, AS Hellkamp , KS Pieper , M Labinaz , EA Cohen , CE Buller , WJ Cantor , P Seidelin, J Ducas , RG Carere , MK Natarajan , JC O'Shea , JE Tcheng , for the ESPRIT Investigators
BACKGROUND: The Enhanced Suppression of the Platelet glycoprotein
IIb/IIIa Receptor with Integrilin Therapy (ESPRIT) trial compared
the use of eptifibatide with placebo in 2064 coronary intervention
patients. It was previously reported that Canadian patients had reduced
rates of 30-day and one-year death, myocardial infarction (MI) or targetvessel
revascularization (TVR) compared with patients in the United
States (US).
OBJECTIVE: To examine whether operator or institutional volume differences
explain the regional variation in clinical outcome.
METHODS AND RESULTS: Each site received an operator and institutional
volume survey. Fifty-seven sites (62%) returned complete data on
1338 patients. In this smaller cohort, Canadian patients had reduced rates
of 30-day and one-year death, MI or TVR compared with US patients
(6.3% versus 10.3% and 14.9% versus 20.1%, respectively; P<0.05 for both
comparisons). Among 176 physicians with a median of 13 years experience,
the median operator volume was 200 cases per year. Operators with
fewer than 100 cases per year had higher rates of 30-day death, MI or TVR
(13.2% versus 8.7%; P=0.18) and large MI (7.7% versus 3.3%; P=0.06)
than those with 100 or more cases per year. The median institutional volume
was 1064 cases per year. Canadian and US centres had similar operator
and institutional volumes. By multivariate modelling, operator volume
was not predictive of adverse clinical events. However, the rates of 30-day
and one-year death, MI or TVR fell by 3% for every 100 patients treated by
the institution (OR 0.97; P=0.058 and P=0.002, respectively). Enrollment
in Canada was associated with improved outcomes at 30 days (OR 0.50;
P=0.001) and one year (OR 0.66; P=0.001) despite inclusion of volume
variables in the models.
CONCLUSIONS: In the ESPRIT study, institutional volume was associated
with a modest reduction in risk of death, MI or TVR over short- and
long-term follow-up periods. The Canadian and US investigators and
institutions selected in ESPRIT had similar annual procedural volumes.
Therefore, volume variables did not explain the differential risk of clinical
events observed for patients enrolled in the two countries.
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