Purpose: Physicians routinely perform cardiac stress testing to diagnose and risk-stratify patients suspected of having coronary heart disease (CHD), but its use has come under intense scrutiny recently because of concerns about explosive growth, the contribution of this growth to high and rising healthcare costs, and potential patient harms related to radiation exposure from radionuclide imaging. However, it is unknown whether trends in its utilization may be attributable to changing population demographics and clinical risk factors.
Method: We analyzed nationally representative cross-sections of adult ambulatory patient visits in the United States, using a sample of 872,498 visits from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey from 1993 to 2010. Patients were excluded if they had prior history of CHD. The main outcomes were survey-weighted measures of referrals for or performance of cardiac stress testing, with or without imaging. Multivariable logistic regression was used to test time trends, with year modeled as a linear predictor, and we included clinical risk factors (smoking, diabetes, dyslipidemia, and hypertension), an indicator for whether the patient's reason for visiting the physician was chest pain, physician specialty, and sociodemographic characteristics, including age, gender, race/ethnicity, geographic location, and insurance status.
Result: The annual number of adult ambulatory visits that resulted in a cardiac stress test being ordered or performed increased steadily from 1.86 million in 1993-1997 (31 in 10,000 visits) to 3.89 million in 2006-2010 (46 in 10,000 visits). After adjusting for clinical and sociodemographic characteristics, there was no evidence of a time trend in stress testing (P=0.48 for trend). However, the portion of cardiac stress tests performed with imaging increased from 64% (95% CI 48%-79%) in 1993-1997 to 87% (95% CI 79%-96%) in 2006-2010 (P<0.001 for trend).
Conclusion: The growth in physicians' use of cardiac stress testing does not appear to represent dynamic changes in over-testing or overuse. However, the increasing use of cardiac stress testing with imaging, much of which exposes patients to radiation, is unlikely to be related to changing patient demographics or clinic risk factors. It therefore supports concerns voiced by professional societies and insurers about inappropriate utilization of cardiac imaging.
