The first Massachusetts public report of PCI risk-adjusted mortality was released in 2005, for cases performed during 2003, and demonstrated comparable performance by all Massachusetts hospitals, as measured by the “Standardized Mortality Incidence Rate” (SMIR) [11
]. The state-wide unadjusted in-hospital mortality following PCI was 1.71% (n=12,657 total PCI cases for the last nine months of 2003). Results from this report indicated that Brigham and Women’s Hospital (BWH) outcomes were within expectations given our case-mix, though higher risk patients appeared to experience slightly worse outcomes compared with statewide averages than the lower risk population (neither difference was statistically significant). Given the impact of the report on external assessment of the quality of care at our institution, we undertook a detailed exploration of the factors associated with mortality following PCI. Between January2003 and December 2005 there were 85 in-hospital deaths out of 5050 patients receiving PCI performed at BWH, with an unadjusted mortality rate of 1.68%. While only 2.69% of patients had presented in cardiogenic shock, these patients represented more than 54% of the mortality following PCI with such patients experiencing a 68-fold increase in the risk of death as compared with patients not presenting in shock.
As shown in , 44.7% of patients who died prior to hospital discharge had at least one severe acute medical condition present before the index PCI procedure that were not accounted for in the data collection instrument used by the state mandated effort (the ACC-NCDR) [12
]. Typical examples of such severe acute co-morbidities included advanced malignancy, active infection, acute stroke, peri-operative myocardial infarction following major non-cardiac surgery, and anoxic brain injury.
Characteristics of patients who died following PCI at Brigham and Women’s Hospital from 2003 to 2005
We sought to examine the mortalities further through detailed review of the clinical record and angiograms in an effort to classify the deaths into 1 of 3 categories; 1) no complication of the procedure thought to have contributed to death, 2) complication of procedure possibly related to patient’s death, and 3) procedural complication materially contributing to the patient’s death. Charts and films were reviewed independently by 2 board certified interventional cardiologists blinded to both the identity of the patient and the performing interventional cardiologist. Determinations of causality were made based on major neurologic, vascular, or cardiac complications occurring during the procedure or during the hospitalization following the PCI. Examples include intracerebral hemorrhage, major vascular complications requiring surgery or leading to hemodynamic instability, coronary complications including dissection and loss of vessel or acute or subacute stent thrombosis. Of the 85 deaths, 11 (13%) were categorized as being related to a complication of the PCI procedure. A further 7 (8%) were determined to be possibly related to the PCI procedure. The majority of deaths (67/85, 79%), however, had no identifiable complication of the procedure which was plausibly related to the patient’s death.
Based on this analysis, we sought to improve the performance of the standard risk prediction model by adding available pre-procedural data elements including: presentation with neurologic compromise following a presenting cardiac arrest, history of malignancy, in-hospital onset of acute coronary syndrome (for example following non-cardiac surgery), and presentation to hospital with sepsis. The revised model was then tested using a backward selection algorithm on a boot-strap developed multivariate risk model utilizing our single center PCI experience since 2005. This analysis of 4,921 consecutive PCI cases demonstrated that the addition of the four additional covariates modestly improved the discrimination of the model, with an improvement in the area under the ROC curve from 0.919 to 0.937. However this improvement was not statistically significant, with a pair-wise comparison for improvement in model discrimination having a p-value of 0.171, despite adequate power (>80%) to detect a difference between the two models.
While inconclusive, this initial analysis suggests that there may be additional value to expanding the existing risk prediction models to include high risk markers available at case presentation. In support of this hypothesis is the evidence from MA which has recently begun to use a composite additional risk factor (“compassionate use PCI”) in the risk adjustment model for MA PCI outcomes for 2006. The “compassionate use” variable was developed to identify uniquely high risk cases which were taken for PCI when the long term prognosis of the patient was unclear to the operator, but when there was a class I indication for emergent revascularization. These included survivors of cardiac arrest with neurologic impairment in the setting of STEMI, use of percutaneous ventricular support systems to facilitate high risk PCI, and survivors of multiple cardiac arrests en-route to the hospital. Implicit in the rationale for using mortality as an endpoint of quality is that deaths are a reasonable surrogate for the overall quality of the care being provided. These data, however, illustrate less than one quarter of all deaths were possibly related to the PCI procedure itself.
Given the complexity and acuity of the patients treated with PCI, our analysis would suggest that overall mortality for a given provider is greatly influenced by the severity of illness of the patients the operator is willing to take to a procedure. We hypothesize that the impact of severity of illness may be underappreciated by current risk models and could significantly impact the estimation of quality of care by reporting agencies. However, the analysis above is based on a single center’s experience, and may not be representative of centers who do not perform within the State’s mortality predication expectation. Nonetheless, it would seem prudent to consider the addition of adjudicated outcomes of whether a death following PCI was either likely or possibly related to the procedure; as unrelated deaths in cases with clear indications for PCI procedures ought not be counted “against” institutions or operators.