A Roberts

Cumulative funnel plots for the early detection of interoperator variation: retrospective database analysis of observed versus predicted results of percutaneous coronary intervention

Objective To use funnel plots and cumulative funnel plots to compare in-hospital outcome data for operators undertaking percutaneous coronary interventions with predicted results derived from a validated risk score to allow for early detection of variation in performance. Design Analysis of prospectively collected data. Setting Tertiary centre NHS hospital in the north east of England. Participants Five cardiologists carrying out percutaneous coronary interventions between January 2003 and December 2006. Main outcome measures In-hospital major adverse cardiovascular and cerebrovascular events (in-hospital death, Q wave myocardial infarction, emergency coronary artery bypass graft surgery, and cerebrovascular accident) analysed against the logistic north west quality improvement programme predicted risk, for each operator. Results are displayed as funnel plots summarising overall performance for each operator and cumulative funnel plots for an individual operator’s performance on a case series basis. Results The funnel plots for 5198 patients undergoing percutaneous coronary interventions showed an average observed rate for major adverse cardiovascular and cerebrovascular events of 1.96% overall. This was below the predicted risk of 2.06% by the logistic north west quality improvement programme risk score. Rates of in-hospital major adverse cardiovascular and cerebrovascular events for all operators were within the 3σ upper control limit of 2.75% and 2σ upper warning limit of 2.49%. Conclusion The overall in-hospital major adverse cardiovascular and cerebrovascular events rates were under the predicted event rate. In-hospital rates after percutaneous coronary intervention procedure can be monitored successfully using funnel and cumulative funnel plots with 3σ control limits to display and publish each operator’s outcomes. The upper warning limit (2σ control limit) could be used for internal monitoring. The main advantage of these charts is their transparency, as they show observed and predicted events separately. By this approach individual operators can monitor their own performance, using the predicted risk for their patients but in a way that is compatible with benchmarking to colleagues, encapsulated by the funnel plot. This methodology is applicable regardless of variations in individual operator case volume and case mix.

Secondary prevention following coronary artery bypass grafting has improved but remains sub-optimal: the need for targeted follow-up

A focused review of secondary preventive medication following revascularisation provides an opportunity to ensure optimal use of these agents. A retrospective analysis of our in-house cardiothoracic surgical database was performed to identify patients undergoing non-emergency, elective surgical revascularisation discharged on four secondary preventive medications: aspirin; beta-blockers; ACE-inhibitors and statins. Of 2749 patients studied, 2302 underwent isolated coronary artery bypass grafting (CABG), mean age 65.5 years (S.D. 9.15). Overall, 2536 (92%) patients were prescribed aspirin. Beta-blockers were prescribed in 2171 (79%) patients overall, in 1096/1360 (81%) of patients with a history of myocardial infarction and in 465/619 (75%) of patients with left ventricular systolic dysfunction (LVSD). Overall, 1518 (55%) patients were prescribed an ACE-inhibitor and 179 (6.5%) an angiotensin receptor blocker (ARB); one of these agents was prescribed in 446/619 (72%) patients with LVSD and 915/1360 (67%) patients with a history of previous myocardial infarction. Overall, 2518 (92%) patients were prescribed a statin. Secondary preventive therapies are prescribed more commonly on discharge after CABG than in previous studies, but there is a continuing under-utilisation of ACE-inhibitors. To maximise the potential benefits of these agents, further study is required to understand why they are not prescribed.

Funnel plots for comparing performance of PCI performing hospitals and cardiologists: demonstration of utility using the New York hospital mortality data.

The New York State Department of Health collects and reports outcome data on the hospitals and cardiologists who perform percutaneous coronary intervention (PCI) to allow them to examine their quality of care. Results are provided in tabular form. However funnel plots are the display method of choice for comparison of institutions and operators, using the principles of statistical process control (SPC). We aimed to demonstrate that funnel plots, which aid a meaningful interpretation of the results, can be derived from the New York PCI dataset.

External Validation of Established Risk Adjustment Models for Procedural Complications after Percutaneous Coronary Intervention

Background: Workable risk models for patients undergoing percutaneous coronary intervention (PCI) are needed urgently. Objective: To validate two proposed risk adjustment models (Mayo Clinic Risk Score (MC), USA and North West Quality Improvement Programme (NWQIP), UK models) for in-hospital PCI complications on an independent dataset of relatively high risk patients undergoing PCI. Setting: Tertiary centre in northern England. Methods: Between September 2002 and August 2006, 5034 consecutive PCI procedures (validation set) were performed on a patient group characterised by a high incidence of acute myocardial infarction (MI; 16.1%) and cardiogenic shock (1.7%). Two external models—the NWQIP model and the MC model—were externally validated. Main outcome measure: Major adverse cardiovascular and cerebrovascular events: in-hospital mortality, Q-wave MI, emergency coronary artery bypass grafting and cerebrovascular accidents. Results: An overall in-hospital complication rate of 2% was observed. Multivariate regression analysis identified risk factors for in-hospital complications that were similar to the risk factors identified by the two external models. When fitted to the dataset, both external models had an area under the receiver operating characteristic curve ⩾0.85 (c index (95% CI), NWQIP 0.86 (0.82 to 0.9); MC 0.87(0.84 to 0.9)), indicating overall excellent model discrimination and calibration (Hosmer–Lemeshow test, p>0.05). The NWQIP model was accurate in predicting in-hospital complications in different patient subgroups. Conclusions: Both models were externally validated. Both predictive models yield comparable results that provide excellent model discrimination and calibration when applied to patient groups in a different geographic population other than that in which the original model was developed.

Heterogeneity of air pollution effects is related to average temperature

Editor—The APHEA project (air pollution and health: a European approach) found that the effects of daily variation in air pollution on mortality were significantly stronger in western Europe than in eastern Europe.1 The authors have put forward several explanations for this inconsistency, all of which, generally speaking, suggest that the small effects found in eastern Europe are an artefact. We propose a less dismissive explanation. Inspired by the Eurowinter study,2 we plotted the relative risk of death in cities in the APHEA project1 against …

Letter by Kelland and Roberts Regarding Article, “Lipid Management to Reduce Cardiovascular Risk: A New Strategy Is Required”

To the Editor: We agree with Drs Superko and King that only by fully appreciating the differences between relative and absolute risk reduction can we determine the best treatment for our patients.1 Using the number needed to treat (NNT; the reciprocal of the absolute risk reduction)2 is a clinically meaningful way of doing this, although, as the authors point out, it is more difficult when comparing studies with varying lengths of follow-up. Superko and King attempt to overcome …