Mark McClellan

OBJECTIVE: To determine the effect of more intensive treatments on mortality in elderly patients with acute myocardial infarction (AMI). DESIGN: Analysis of incremental treatment effects using differential distances as instrumental variables to account for unobserved case-mix variation (selection bias) in observational Medicare claims data (1987 through 1991). MAIN OUTCOME MEASURES: Survival to 4 years after AMI. RESULTS: Patients who receive different treatments differ in observable and unobservable health characteristics, biasing estimates of treatment effects based on standard methods of adjusting for observable differences. Patients' differential distances to alternative types of hospitals are strong independent predictors of how intensively an AMI patient will be treated and appear uncorrelated with health status. Thus, differential distances approximately randomize patients to different likelihoods of receiving intensive treatments. Comparisons of patient groups that differ only in differential distances show that the impact on mortality at 1 to 4 years after AMI of the incremental ("marginal") use of invasive procedures in Medicare patients was at most 5 percentage points; this gain was achieved during the first day of hospitalization and therefore appears attributable to treatments other than the procedures. Admission to a hospital treating a high volume of AMI patients was associated with an effect on mortality at 4 years of less than 1 percentage point, again arising on day 1. Patients living in rural areas experienced acute mortality that was an additional 0.6 percentage-point higher, after controlling for less access to intensive treatments. CONCLUSIONS: For elderly patients with AMI, the aspects of treatment most affecting long-term survival relate to care within the first 24 hours of admission. The survival benefits from greater use of catheterization and revascularization procedures appear minimal in marginal patients.

We describe an econometric technique, instrumental variables, that can be useful in estimating the effectiveness of clinical treatments in situations when a controlled trial has not or cannot be done. This technique relies upon the existence of one or more variables that induce substantial variation in the treatment variable but have no direct effect on the outcome variable of interest. We illustrate the use of the technique with an application to aggressive treatment of acute myocardial infarction in the elderly.

“Defensive medicine” is a potentially serious social problem: if fear of liability drives health care providers to administer treatments that do not have worthwhile medical benefits, then the current liability system may generate inefficiencies much larger than the costs of compensating malpractice claimants. To obtain direct empirical evidence on this question, we analyze the effects of malpractice liability reforms using data on all elderly Medicare beneficiaries treated for serious heart disease in 1984, 1987, and 1990. We find that malpractice reforms that directly reduce provider liability pressure lead to reductions of 5 to 9 percent in medical expenditures without substantial effects on mortality or medical complications. We conclude that liability reforms can reduce defensive medical practices.

BACKGROUND: Patients with end-stage renal disease are known to have decreased survival after myocardial infarction, but the association of less severe renal dysfunction with survival after myocardial infarction is unknown. OBJECTIVES: To determine how patients with renal insufficiency are treated during hospitalization for myocardial infarction and to determine the association of renal insufficiency with survival after myocardial infarction. DESIGN: Cohort study. SETTING: All nongovernment hospitals in the United States. PATIENTS: 130 099 elderly patients with myocardial infarction hospitalized between April 1994 and July 1995. MEASUREMENTS: Patients were categorized according to initial serum creatinine level: no renal insufficiency (creatinine level < 1.5 mg/dL [<132 micromol/L]; n = 82 455), mild renal insufficiency (creatinine level, 1.5 to 2.4 mg/dL [132 to 212 micromol/L]; n = 36 756), or moderate renal insufficiency (creatinine level, 2.5 to 3.9 mg/dL [221 to 345 micromol/L]; n = 10 888). Vital status up to 1 year after discharge was obtained from Social Security records. RESULTS: Compared with patients with no renal insufficiency, patients with moderate renal insufficiency were less likely to receive aspirin, beta-blockers, thrombolytic therapy, angiography, and angioplasty during hospitalization. One-year mortality was 24% in patients with no renal insufficiency, 46% in patients with mild renal insufficiency, and 66% in patients with moderate renal insufficiency (P < 0.001). After adjustment for patient and treatment characteristics, mild (hazard ratio, 1.68 [95% CI, 1.63 to 1.73]) and moderate (hazard ratio, 2.35 [CI, 2.26 to 2.45]) renal insufficiency were associated with substantially elevated risk for death during the first month of follow-up. This increased mortality risk continued until 6 months after myocardial infarction. CONCLUSIONS: Renal insufficiency was an independent risk factor for death in elderly patients after myocardial infarction. Targeted interventions may be needed to improve treatment for this high-risk population.

The concept of accountable care organizations (ACOs) has been set forth in recently enacted national health reform legislation as a strategy to address current shortcomings in the U.S. health care system. This paper focuses on implementation issues related to these organizations, building on some initial examples. We seek to clarify definitions and key principles, provide an update on implementation in the context of other reforms, and address emerging issues that will affect the organizations' success. Finally, building on the initial experience of several organizations that are implementing accountable care and complementary reforms, we propose a national strategy to identify and expand successful approaches to accountable care implementation.