Short-term duration of follow-up has prevented the full potential of clinical data registries from being realized. As average acute hospital length of stay has shortened, procedural-related deaths and complications are correspondingly more likely to occur after patients have been discharged from the hospital. The use of advanced mechanical and pharmacological support has increasingly prolonged the lives of many critically ill postoperative patients, and such patients may be transferred to long-term critical care facilities on ventilators or dialysis. Deaths among such patients may not occur for months after their index hospital discharge, and these delayed postoperative deaths would not be captured in most existing clinical registries8
. Short-term follow-up is also a major limitation of comparative effectiveness studies of various treatment strategies, such as CABG or PCI for coronary artery disease. Differences in efficacy of alternative treatments are often not apparent for months or years, much longer than the typical endpoints in most clinical registries. Finally, some preoperative risk factors may have little impact on short-term mortality but are major considerations in the longer term, and vice versa.
Some previous studies have assessed the long-term impact of preoperative risk factors, operative and perioperative care processes, and postoperative complications14–28
. Our study focuses specifically on the former, and it addresses the major limitations of these earlier studies. Many are from single institutions and their inferences may be confounded by idiosyncratic hospital practice patterns. Most prior studies include only a few hundred to a few thousand patients and lack the power to identify the full spectrum of factors associated with outcomes. Some studies of long-term CABG mortality have been based solely on large administrative databases. This strategy assures adequate sample size and provides valuable information regarding vital status, readmissions, re-interventions, costs, aggregate resource utilization, and outpatient activities. However, administrative databases have a number of well-known deficiencies that limit their usefulness in clinical research, including misclassification of procedures and diagnoses; unavailability of important clinical variables; inability to distinguish co-morbidities from complications (in the absence of Present on Admission indicators); and focus on narrow patient populations29–34
. There are studies of long-term CABG outcome predictors based on clinical registries, but these are derived from data that are ten to twenty years old and may not reflect current patient severity and surgical practice35, 36
Our study seeks to overcome the inherent limitations of both clinical and administrative data registries by linking the two together. This approach compensates for their individual deficiencies while harnessing their complementary strengths. The resulting linked data retain the granularity and clinical detail of clinical registries while adding long-term outcomes and cost data available in administrative data sources. These linked data are ideally suited to studies of long-term clinical outcomes, comparative effectiveness, resource utilization, and provider performance for particular types of patients.
Using predicted long-term outcomes tailored to their specific risk profiles, patients may more effectively participate in shared decision-making with their providers. Awareness of both the short-term and long-term risks and benefits (e.g., survival, complications, quality of life) might assist patients in deciding whether or not to proceed with surgery. Furthermore, just as short-term outcomes vary among providers, it is possible that long-term outcomes may also vary, and such information could be useful for all stakeholders.
The long-term CABG mortality model described in this report, based solely on preoperative patient characteristics, is only the first of many applications we envision to exploit the advantages of linked registries. In addition to mortality, it will also be possible to study other long-term endpoints such as readmissions, re-interventions, and cumulative costs and resource use. Other models will estimate the effect of intraoperative decisions, such as use of all-arterial grafting or off-pump procedures, on long-term outcomes. Combined with preoperative variables, such information could help determine what specific procedures or perioperative strategies are most useful for specific types of patients. The addition of early postoperative events (e.g., stroke, or mediastinitis) as predictor variables would permit more effective discussions with such patients regarding their long-term health expectations.
Linkages with CMS and other administrative data sources will also enhance the accuracy of outcomes data used to calculate performance metrics such as the STS CABG composite scores37, 38
. For example, ongoing linkages with the Social Security Death Master File or National Death Index would permit continuous input and validation of vital status for patients of all ages, not just the Medicare population39
Linked clinical and administrative data will facilitate the determination of risk-adjusted, long-term freedom from reoperation and readmission not only for surgical procedures but also for a variety of medical devices, such as cardiac valve prostheses. This ability to capture objective long-term patient status, coupled with extensive clinical data from the perioperative period, will be a marked improvement over existing methods for post-market surveillance.
Linkages to other clinical registries will also be useful, and their combined utility will be further enhanced by linking to administrative data, as demonstrated by the ASCERT comparative effectiveness study1
. Furthermore, as payment strategies evolve from a focus on procedures or acute hospitalizations to episodes of care, the ability to link related clinical registries (e.g., cardiology and cardiac surgery) will facilitate the study and implementation of these reimbursement policies. Finally, linkages between clinical and payer registries would provide unique information such as outpatient visits, compliance with medications, and cumulative resource use.