Defining operative mortality: Impact on outcome reporting

Abstract

Objective: Death is an important outcome of procedural interventions. The death rate, or mortality rate, is subject to variability by definition. The Society of Thoracic Surgeons Adult Cardiac Surgery Database definition of "operative" mortality originally included all in-hospital deaths and deaths occurring within 30 days of the procedure. In recent versions of the Society of Thoracic Surgeons Adult Cardiac Surgery Database, "in-hospital" has been modified to include "patients transferred to other acute care facilities," and "deaths within 30 days unless clearly unrelated to the procedure" has been changed to "deaths within 30 days regardless of cause." This study addresses the impact of these redefinitions on outcome reporting.

Methods: The California Office of Statewide Health Planning and Development hospitalized patient discharge database was queried for the year 2009, the most recent year that data files could be linked to the vital statistics death files to include all-cause mortality. Isolated coronary artery bypass grafting, isolated valve, coronary artery bypass grafting valve, and percutaneous coronary intervention procedures were identified by International Classification of Diseases, Ninth Edition, Clinical Modification procedure codes. Percutaneous coronary intervention procedures were further divided into acute coronary syndrome (percutaneous coronary intervention acute coronary syndrome) and all other percutaneous coronary intervention (percutaneous coronary intervention no acute coronary syndrome). Deaths were counted by 5 methods depending on the time and place of occurrence: (1) in-hospital or during the index hospitalization; (2) in-hospital + connected hospitalization, defined as a transfer to another acute care facility on the same day or within 24 hours of discharge; (3) in-hospital + 30 day, death during index hospitalization or within 30 days after the procedure; (4) in-hospital + connected + 30 day readmission, death during index hospitalization, transfer to acute care facility, or deaths during readmission within 30 days; and (5) in-hospital + connected + 30 day. To study the impact of these operative mortality definitions, we examined 5 different methods to track mortality and performed 2 separate analyses. The first analysis did not exclude any patients, and the second analysis excluded any patient who could not be accurately tracked after hospital discharge.

Results: In the first analysis with no patients excluded, a total of 17% (117/697) of surgical deaths and 31% (409/1324) of percutaneous coronary intervention deaths were counted after the original hospitalization. The highest percentage of posthospital deaths occurred after elective percutaneous coronary intervention: 45% (135/301). In surgical patients, the highest percentage of posthospital deaths occurred in coronary artery bypass grafting procedures: 20% (57/284). In the second analysis, with untrackable patients excluded, hospital deaths included 12% (161/1324) for percutaneous coronary intervention compared with 4% (30/697) for surgical procedures.

Conclusions: A significant percentage of procedural deaths occur after transfer or discharge from the index hospital. This is especially evident in the percutaneous coronary intervention group. These findings illustrate the importance of the definition of "operative" mortality and the need to ensure accuracy in the reporting of data to voluntary clinical registries, such as the Society of Thoracic Surgeons Adult Cardiac Surgery Database and National Cardiovascular Data Registry.

Keywords: CABG; PCI; cardiac surgery; operative mortality; outcome reporting.