Cardiovascular imaging is a source of innovation and controversy for the health care community. Cardiologists and radiologists are now capable of obtaining high quality images that describe myocardial function and perfusion, define risk of major clinical events, and show coronary anatomy without need for invasive instrumentation.(1) At the same time there is concern that the rapid dissemination of cardiovascular imaging is a prime example of a costly technology that is enthusiastically embraced without appropriate supporting scientific evidence.(2,3)
During the past five years, medical imaging has grown substantially, with Medicare Part B costs alone increasing from $6.89B in 2000 to $14.11B in 2005 (105%) of which an estimated 1/3 is cardiovascular.(3,4) In addition, there is inconsistent use, with some areas of the country having utilization rates 10 times those of others.(5) There is no clear explanation for the rapid growth; it cannot be ascribed entirely to aging of the population, changing disease rates, or improved outcomes.(3,4) The “value” of imaging in terms of improved health outcomes or reduced cardiovascular events remains subjective, with limited evidence, often generated with flawed research methodology,(6).(7) There are also concerns that imaging can cause harm(8,9), that there are few rigorous regulatory controls, and that utilization is at least in part driven by self referral(10) and, in some cases, even direct-to-consumer advertising(11).
A commonly cited model for efficacy in imaging describes six hierarchical tiers of evidence: technical efficacy, diagnostic accuracy, diagnostic thinking, therapeutic efficacy, patient outcome, and societal efficacy.(12–14) A recently convened American College of Cardiology - Duke University think tank on imaging quality in cardiovascular medicine, (15) noted that imaging research has primarily focused on diagnostic and prognostic accuracy, with little work directed at determining the direct impact of imaging on patient outcomes. As a result, among 745 recommendations for cardiovascular imaging in ACC and AHA guidelines, only 1% are based on level A evidence.(16) In contrast, in cancer medicine randomized trials have been completed or are under way for assessing the ability of imaging technologies to prevent major clinical events due to breast(17) or lung cancer.(18)