Impact of Medical Liability Reform on Coronary Artery Disease Management

Physicians often report practicing “defensive medicine,” including ordering marginally beneficial tests and interventions to reduce medical malpractice liability. However, prior studies report weak evidence that malpractice reform affects physician behavior or overall healthcare spending. The emphasis in most prior studies on overall healthcare costs may obscure the impact of caps on specific clinical decisions. We study a specific clinical setting –testing and treatment for possible coronary artery disease (CAD).

CAD is the leading cause of death in the United States. Chest pain is the second most common complaint in the emergency department and missed myocardial infarction is one of the most important causes of malpractice lawsuits. Because unrecognized CAD can have catastrophic outcomes, physicians are understandably cautious in their testing and intervention decisions. Testing and intervention for CAD are common, and many believe that these procedures are overused. Unfortunately, CAD symptoms are often non-specific and highly variable. Clinical guidelines about which patients with suspected CAD symptoms should be tested are quite general, and test results can be ambiguous. Clinicians must exercise judgment on who should be tested, whether to begin with an initial non-invasive stress test or more definitive left-heart catheterization (LHC), whether to proceed from an ambiguous initial stress test to LHC, and whether to revascularize patients with obstructive CAD, through percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).

We used a difference-in-differences research design to compare changes in CAD testing and treatment in New-Cap States to changes in 20 states without damage caps (No-Cap States). We used the 5% national, Medicare fee-for-service random sample from 1999-2013 to study the behavior of 97,821 physicians who have ordered or performed CAD related treatments during the sample period.

We examine changes, following cap adoption, in the rates at which physicians order ischemic evaluation for possible CAD, the type of initial evaluation (stress testing or LHC), LHC referral rates following stress test, and revascularization rates following ischemic evaluation. Physicians in New-Cap States substantially altered their CAD testing and intervention practices following damage cap adoption, relative to control physicians. They conducted a similar number of ischemic evaluations (New-Cap versus No-Cap difference -0.05%; 95% CI -8.0%, +7.9 %), but performed fewer definitive but invasive LHC tests (-24%, 95% CI -40%, -7%; P<0.01) and more less-definitive but non-invasive stress tests (+8%, 95% CI -4%, +19%; P=0.18). There are some important downstream effects as well. Physician in New-cap states referred fewer stress-tested patients for LHC (-21%, 95% CI -40%, -2%; P=0.03). Revascularization following ischemic evaluation also declined in New-Cap states, relative to No-Cap States (-23%, 95% CI -40%, -4%; P=0.02). These findings suggest that physicians tolerate greater clinical uncertainty in CAD testing and treatment if they face lower malpractice risk. Our study is the first to find evidence for large effects of malpractice risk on physician behavior.