Analysis of the institutional volume-outcome relations for balloon angioplasty and stenting in the stent era in California

BACKGROUND

Coronary artery stenting has become the predominant form of percutaneous coronary intervention. However, it is not clear whether a better outcome is conferred by stent placement in high-volume, more experienced centers as has been shown with balloon angioplasty. Furthermore, as stent procedures become more common, balloon angioplasty becomes less frequent. Thus, we separately analyzed the outcomes after coronary angioplasty and stenting in a large, unselected population to determine the effect of annual institutional angioplasty or stent volume on in-hospital outcomes after balloon angioplasty or stenting.

METHODS

The California Office of Statewide Health Planning and Development database was queried to obtain discharge data on all patients in 1997 treated with percutaneous transluminal coronary angioplasty (PTCA) or a stent procedure. Hospitals were divided into low-volume (<200 procedures), intermediate-volume (200 to 400 procedures), and high-volume (>400 procedures) institutions as a function of their 1997 PTCA or stent volumes to assess the effect of volume on outcome.

RESULTS

There were 44,276 percutaneous revascularization procedures performed in California in 1997, of which 57% involved coronary stent placement. Mortality rates after PTCA were 2.6%, 1.9%, and 1.4% in low-, intermediate- and high-volume PTCA hospitals, respectively (P <.001). The need for same-day coronary artery bypass grafting (CABG) after PTCA was 2.4%, 2.1%, and 1.2% in low-, intermediate- and high-volume PTCA hospitals, respectively (P <.001). Mortality rates after stent placement were 1.6%, 1.5%, and 1.1% in low-, intermediate-, and high-volume stent hospitals, respectively (P =.022). The need for same-day CABG after stent placement was 1.1%, 1.2%, and 0.8% in low-, intermediate-, and high-volume stent hospitals, respectively (P =.014).

CONCLUSIONS

Short-term results of balloon angioplasty and stent procedures are improved when performed in high-volume hospitals.

Quality in interventional cardiology: towards the future

Interventional cardiology is an example of a medical field in which rapid technological advances have taken place over a short period of time. In the 26 years since the inception of interventional cardiology, there has been an enormous increase in the volume of cases and the number of operators and sites performing coronary angioplasty. Coupled with this, in the last decade we have witnessed tremendous developments in the techniques, materials and adjunctive therapy associated with percutaneous coronary intervention. Health care interventions are intended to benefit patients, but they can also cause harm. The complex combination of processes, technologies and human interaction that constitutes the modern health care delivery system can bring significant benefits. However, it also involves an inevitable risk of adverse events that can, and too often do, happen. The Joint Commission on Accreditation of Healthcare Organizations has defined quality in health care as "the degree to which patient care services increase the probability of desired patient outcomes and reduce the possibility of undesired outcomes, given the current state of knowledge." The establishment of quality standards based on patient outcomes data is a rational means of differentiating the quality of health care in the marketplace. Institutional variation in patients' baseline clinical risks precludes the direct comparison of outcomes across institutions. The application of risk adjustment methodology to account for patient differences in these treatment outcomes is imperative for legitimate comparison of institutional results in the modern era of cardiovascular intervention. The aim of this paper is promote reflection on the importance of quality in interventional cardiology and, simultaneously, to emphasize the role of health professionals in this regard, in daily practice and through their investigations. Another aim is encourage the inclusion of risk adjustment methodology to account for patient differences, and consequently, to make an accurate assessment of the results obtained by different operators and institutions.

Analysis of long-term survival after revascularization in patients with chronic kidney disease presenting with acute coronary syndromes

Ischemic heart disease is the most common cause of death in patients with chronic kidney disease (CKD). Patients with CKD who develop an acute coronary syndrome (ACS) have a poor prognosis, with >70% mortality at 2 years. Despite this heavy burden of disease, the optimal management of ACS in this patient population is unknown. Our goal was to compare the effect of coronary revascularization or medical therapy alone on the long-term survival of patients with CKD presenting with ACS. From 1990 to 1998, data were prospectively collected on 4,758 patients admitted to a coronary care unit with the diagnosis of ACS. Of these, 3,104 had preserved renal function, and 1,654 had significant renal dysfunction, as defined by the National Kidney Foundation in the Kidney Disease Outcomes Quality Initiative classification of kidney function as an estimated glomerular filtration rate of <60 ml/min/1.73 m(2). Long-term survival was assessed and outcomes were compared according to whether patients were treated with medical therapy alone or if they underwent a percutaneous or surgical revascularization procedure. Follow-up information was available in 99% of the patients up to 8 years after the index hospitalization. Of the 1,654 patients with significant renal dysfunction, 64 underwent coronary artery bypass surgery, 232 underwent percutaneous coronary revascularization, 280 underwent a diagnostic cardiac catheterization and were subsequently treated medically, whereas 1,078 were treated with medical therapy alone. Percutaneous coronary revascularization was associated with superior long-term survival. In conclusion, patients with severe CKD and ACS had improved long-term survival when treated with percutaneous coronary revascularization.

Effectiveness of stents in small coronary arteries

This study was prospectively randomized to assess the efficacy and safety of Jo heparin-coated stent deployment in small vessels compared with balloon angioplasty. In 202 patients, restenosis in balloon and stent arms was 49% and 30%, respectively.

Reducing costs and improving outcomes of percutaneous coronary interventions

OBJECTIVE

To describe cost reduction and quality improvement efforts in our percutaneous coronary intervention (PCI) program and how risk adjustment was used to assess the effects of these changes.

STUDY DESIGN

Single center registry analysis.

PATIENTS AND METHODS

Data were collected on 2158 PCIs performed between July 1, 1994, and June 30, 1997. Of these, 1126 PCIs reflected care provided after implementation of competitive bidding for catheterization lab supplies, and efforts to reduce the use of postprocedure heparin and to implement early arterial sheaths removal (postbidding period). Hospital costs were estimated using a microcost accounting method. In-hospital mortality rates during the 2 time periods were compared using standardized mortality ratio estimated with a previously validated risk adjustment model for in-hospital mortality.

RESULTS

Compared with the prebidding period, the postbidding period was characterized by a significantly higher utilization of new technology (coronary stents and atherectomy devices 46% vs 25%; abciximab 19.1% vs 3.7, P<.01), and an overall increase in case complexity. Despite these changes, the average and median postbidding cost per case was dollars 1223 and dollars 1444 lower, respectively, than in the prebidding period. After adjustment for comorbidities, procedure variables, complications, and length of hospital stay, multivariate regression modeling identified the postbidding period as an independent predictor of lower hospital costs (P<.001) with an estimated adjusted cost savings of dollars 460. These cost savings were associated with trends toward a lower observed mortality rate, a higher predicted mortality rate, and a significantly lower standardized mortality ratio (SMR .71; 95% CI 0.48-0.9; P<.05).

CONCLUSION

Despite an increase in case complexity and utilization of new technology, cost reductions can be achieved through competitive bidding for supplies and modifications of periprocedure care. Risk adjustment appears to be a valid tool for assessing the effectiveness of these efforts independently from changes in case mix.

Adjusting for patient differences in predicting hospital mortality for percutaneous coronary interventions in the Clinical Outcomes Assessment Program

BACKGROUND

The Clinical Outcomes Assessment Program (COAP) is a coordinated quality improvement program for percutaneous coronary interventions (PCIs) performed in Washington State hospitals. This study describes the development and testing of models for predicting hospital mortality in patients undergoing PCI.

METHODS

The COAP PCI database contains extensive demographic, medical history, and procedural information. This study included 19,358 consecutive PCIs performed in 27 Washington hospitals in 1999 and 2000. The study population was randomly assigned to development (n = 11,591) and test (n = 7614) sets. Logistic regression mortality models were run in the development set and evaluated in the test set.

RESULTS

The test and development sets were similar in demographic, medical history, and procedural characteristics. The overall hospital mortality rate was 1.6% and was similar in the test and development sets. By means of stepwise logistic regression analysis, cardiogenic shock, age, nonelective priority, elevated creatinine level, ejection fraction, number of diseased vessels, myocardial infarction <24 hours from admission, history of chronic obstructive pulmonary disease, male sex, history of peripheral vascular disease, history of PCI, and history of congestive heart failure were identified as predictors of hospital mortality. When applied to the test set, this model had excellent discrimination (c statistic = 0.87, 95% CI = 0.84-0.90). The model was also evaluated in the Northern New England PCI Registry, with very good results (c statistic = 0.85).

CONCLUSION

Developing risk-adjusted models of mortality and other outcomes is an essential part of the quality improvement process for cardiac revascularization procedures. Because of the rapidly changing nature of PCI, modification of these models in the years to come will be required.

Limitations of current risk-adjustment models in the era of coronary stenting

BACKGROUND

Several risk-adjustment models have been developed to compare outcomes of conventional coronary angioplasty across physicians and institutions. Yet the accuracy of these models in contemporary interventional practice--characterized by the widespread use of stents and novel adjuvant pharmacotherapies--has not been sufficiently studied.

METHODS

The principal published predictive models for inhospital mortality after angioplasty were validated in 11,681 patients undergoing coronary stenting and 6475 patients undergoing balloon-only procedures in the Society for Cardiac Angiography and Interventions registry from July 1996 to December 1998. We examined the 2 components of model accuracy: discrimination, as determined by the c-index; and calibration, as measured by the Hosmer-Lemeshow statistic and predicted-versus-observed probability plots.

RESULTS

The discriminative properties of the models were preserved in the validation cohort and did not differ statistically from one another (c-indexes 0.85-0.89). Hosmer-Lemeshow statistics, however, showed poor fit (P <.001), with all 3 models substantially overestimating the risk of adverse outcomes. Although recalibration of the models achieved satisfactory goodness of fit, laboratory-specific ratings differed depending on the model applied.

CONCLUSIONS

Predictive models developed in the era of conventional angioplasty cannot be applied directly to current interventional practice. Although recalibration restores model fit, application of different recalibrated models yields inconsistent assessment of laboratory performance. Development of new, widely generalizable models is warranted, but such models will require continued reassessment as medical technology evolves and practice patterns change.

Endovascular therapy for stenosis of the petrous or cavernous portion of the internal carotid artery: percutaneous transluminal angioplasty compared with stent placement

OBJECT

The effects of percutaneous transluminal angioplasty (PTA) and stent placement for stenosis of the petrous or cavernous portion of the internal carotid artery (ICA) were compared.

METHODS

Twenty-four patients with symptomatic, greater than 60% stenosis of the petrous or cavernous portion of the ICA were treated using PTA or stent placement; 15 were treated with PTA and nine with stent insertion. Initial and follow-up results (> 3 months posttreatment) were compared in each group. Stenotic portions of the ICA were successfully opened in 13 of 15 patients in the PTA group, and in all nine patients in the stent-treated group. In one case in the PTA group stent delivery was attempted; however, the device could not pass through the vessel's tortuous curve, and PTA alone was performed in this case. Postoperatively, the mean stenotic ratio decreased from 72.1 to 29.6% in the PTA group, and from 75.6 to 2.2% in the stent-treated group. In four patients in the PTA group, stenoses greater than 50% were demonstrated on follow-up angiography performed at 3 to 6 months after PTA. In the stent-treated group, no restenosis was encountered, although in one case acute occlusion of the stent occurred; the device was recanalized with PTA and infusion of tissue plasminogen activator. This case was the only one of the 24 in which any neurological deficits related to the endovascular procedure occurred. Stent placement brought a greater gain in diameter than did PTA at the initial and late follow-up period; this gain was statistically significant.

CONCLUSIONS

Stent placement is more effective than PTA for stenosis of the petrous or cavernous portion of the ICA from the viewpoint of initial and late gain in diameter.

Low-risk percutaneous coronary interventions without on-site cardiac surgery: two years' observational experience and follow-up

BACKGROUND

We studied the safety and efficacy of performing low-risk elective and acute infarct percutaneous coronary interventions at a community hospital without cardiac surgical capability.

METHODS

Immanuel St Joseph's Hospital is located 85 miles from St Mary's Hospital, which is the nearest center with on-site cardiac surgery. All components of the Mayo Clinic percutaneous coronary intervention program were replicated at Immanuel St Joseph's Hospital, including a telemedicine system to enable real-time consultation with interventional and cardiac surgical colleagues during procedures.

RESULTS

From March 1999 to June 2001, 196 patients underwent elective percutaneous coronary intervention at Immanuel St Joseph's Hospital. Procedural success was achieved in 195 (99.5%) patients, with 1 (0.5%) inhospital death. At mean follow-up of 8.2 months, 2 (1.0%) additional patients died of noncardiac causes and 15 (7.7%) patients required target vessel revascularization. From March 2000 to June 2001, 89 patients underwent primary percutaneous coronary intervention for acute myocardial infarction. Procedural success was achieved in 83 (93.3%) patients, with 3 (3.4%) inhospital deaths. At 30-day follow up, no additional patients died, had recurrent myocardial infarction, or required target vessel revascularization. No patients required transfer to another facility for emergent cardiac surgery for a procedure-related complication.

CONCLUSIONS

Low-risk elective and acute infarct percutaneous coronary interventions can be performed with safety and efficacy at a community hospital without cardiac surgical capability by following rigorous standards.

ROC methodology within a monitoring framework

Receiver operating characteristic (ROC) methodology is widely used to evaluate and compare diagnostic tests. Generally, each diagnostic test is applied once to each subject in a population and the results, reported on a continuous scale, are used to construct the ROC curve. We extend the standard method to accommodate a framework in which the diagnostic test is repeated over time to monitor for occurrence of an event. Unlike the usual situation in which event status is static, the problem we address involves event status that is not constant over the monitoring period. Subjects generally are classified as non-events, or controls, until they experience events that convert them to cases. Viewing the data as incomplete discrete failure time data with time-varying covariates, potentially useful diagnostic markers can be related appropriately in time with the true condition and varying amounts of information per individual can be taken into account. The ROC curve provides an assessment of the performance of the test in combination with the schedule of testing. Within this framework, a computational simplification is introduced to calculate variances and covariances for the areas under the ROC curves. Periodic monitoring for reperfusion following thrombolytic treatment for acute myocardial infarction provides a detailed example, whereby the lengths of the testing interval combined with different diagnostic markers are compared.

Adherence to practice guidelines: the role of specialty society guidelines

BACKGROUND

Physician adherence to guidelines is often poor, but the reasons have not been completely studied. We investigated whether physician adherence to guidelines for percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG) varied by source, development methods, or the extent of their evidence-base.

METHODS AND RESULTS

We assessed adherence to guidelines developed by the American College of Cardiology/American Heart Association (ACC/AHA) for PTCA (1988 and 1993) and for CABG (1990) and guidelines developed by RAND for PTCA and CABG in 1990. We randomly sampled patients on Medicare who were undergoing coronary angiography in 5 states in 1991 and 1992, extracting clinical and laboratory data from medical records and using computer programs to classify the appropriateness of each procedure. A total of 543 PTCA and 676 CABG procedures were studied. By use of the 1988 ACC/AHA guidelines, 30% of PTCAs were rated class III (inappropriate), whereas 24% were class III by use of the 1993 guidelines. Only 1.5% of CABG procedures were class III with ACC/AHA guidelines. By use of RAND guidelines, 12% of PTCA and 9% of CABG procedures were classified as inappropriate.

CONCLUSIONS

Adherence to guidelines is higher when the recommendations are supported by evidence from randomized clinical trials (CABG). The credibility of the source and familiarity with the guidelines do not ensure compliance. When evidence is lacking, as with PTCA at the time of this study, guideline recommendations may lag behind appropriate changes in clinical practice. More frequent revisions coupled with on-line access have the potential to make guidelines more useful.

Regional variation in the management of acute myocardial infarction in the province of Quebec

BACKGROUND

Previous studies have shown that there are differences in acute myocardial infarction (AMI) management in Canada and in the United States. However, there has been little research to evaluate regional variations in AMI treatment and outcomes for Canadian patients.

OBJECTIVE

To determine whether regional variation in the management of AMI in Quebec has an impact on patient mortality and morbidity.

PATIENTS AND METHODS

Discharge summary and physician claims databases for 76,012 patients with AMI were used between January 1, 1988 and December 31, 1995 to build 16 cohorts for the administrative regions of the province of Quebec. The clinical characteristics, prescription medications, cardiac procedure use, readmissions for cardiac complications and mortality across the different regions were compared.

RESULTS

After adjusting for age and sex, discharge prescriptions resulted in the following ranges: angiotensin-converting enzyme inhibitors 34% to 46% of patients, acetylsalicylic acid 49% to 77%, beta-blockers 32% to 54%, calcium channel blockers 25% to 48%, lipid-lowering drugs 4% to 16% and nitrates 76% to 86%. Procedure use varied considerably across the province during the initial 10 days post-AMI (catheterization 3% to 28%; percutaneous coronary intervention 1% to 8%, and coronary artery bypass surgery 0 to 2%), as well as one year after discharge (27% to 47%, 8% to 17%, and 6% to 12%, respectively). Some variation was observed for cardiac complications after one year (unstable angina 9% to 21%; congestive heart failure and recurrent myocardial infarction, no major variation). However, there was no significant regional variation observed for one-year and three-year mortality rates (19% to 22% and 27% to 31%, respectively).

CONCLUSIONS

There was marked regional variation in the rates of discharge prescriptions for cardiac medications and cardiac procedures in patients who have had an AMI in Quebec. These results suggest that the type of treatment received for an AMI depends on the region in which the patient lives. This variation appeared to affect readmission rates for unstable angina, but had no impact on mortality or other cardiac complications post-AMI.