Patient management after noninvasive cardiac imaging: A commentary on the reported results from SPARC

Abstract

A paper was recently published which summarized some of the observations gleaned from the Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles Coronary Artery Disease (SPARC), which concluded that ‘‘overall, noninvasive testing had only a modest impact on clinical management of patients referred for clinical testing.’’ 1 The design of this prospective multicenter registry of patients referred for either stress SPECT, PET, or coronary CT angiography (CCTA) had previously been published. 2 In this recent publication, 1 90-day post-test rates of catheterization and changes in medical therapy were assessed in 1,703 patients without a history of known CAD and an intermediate to high likelihood of CAD. Of the entire group undergoing noninvasive testing, 9.6% underwent cardiac catheterization by 90 days post-testing. With respect to the imaging results, 74% of the patients had normal studies, 18% were mildly abnormal, and only 8% had moderate-to-severe abnormal findings. Since slightly \50% of the patients with moderately or severely abnormal noninvasive test results were referred for catheterization, the authors suggested that perhaps this represented ‘‘undertreatment of higher risk patients.’’ Interestingly, 39% of patients who had SPECT imaging and 28% who had PET studies who were referred for catheterization had no significant obstructive CAD. It would be interesting to know more about these patients. Surprisingly, only 30% and 49% of patients with moderate-severe abnormal SPECT and PET scans, respectively, had multivessel CAD at catheterization. Furthermore, only about one-third of patients with moderate-to-severe abnormal nuclear imaging studies were revascularized. Does this imply that the criteria for moderate-severe SPECT and PET scans overestimated the extent and severity of underlying CAD as determined by a modest catheterization rate, a low prevalence of multivessel disease and a rather low rate of revascularization? The SPARC investigators also surmized from this registry data of 1,703 patients who had noninvasive imaging studies, that changes in post-imaging medical therapy in those with abnormal scans were suboptimal according to what was expected from guideline-based evidence. For example, among patients with moderatelyto-severely abnormal study results, 24% of patients were not receiving aspirin, 44% were not receiving a beta blocker, and 23% were not receiving a lipid-lowering drug at 90 days after the index imaging study. The authors stated that ‘‘the fact that approximately onethird of patients with high-risk study results were not taking key medications after imaging suggests that a component of patient undertreatment is present as well 1 .’’ With respect to the perceived suboptimal rate of referral to catheterization and suboptimal medical therapy post imaging in patients who exhibited abnormal scan results, the authors of this SPARC study cautioned that, ‘‘in light of the costs associated with cardiovascular imaging, it is problematic to justify the use of testing that will not be incorporated into subsequent patient care 1 .’’ Are the rather dire conclusions and implications of this SPARC registry study really warranted or an overreaction? First of all, was the original decision for referral for noninvasive imaging in these patients appropriate? Since 90% of the patients had either chest pain, dyspnea, or both, and their mean age was 62 years with nearly two-thirds having hypertension and an elevated cholesterol, and 30% having diabetes, it certainly appears that this group of patients were appropriately referred for imaging to detect CAD and assess prognosis. The fact that 74% of the entire group had normal or nonobstructive imaging results is an important outcome since we have know for a long time that normal radionuclide imaging studies and normal coronary anatomy are associated with an good prognosis. For example, patients with normal exercise SPECT results have a \1.0% annual rate of death or nonfatal infarction. 3 A major value of noninvasive imaging, not highlighted by the SPARC investigators, is to identify this low-risk group that either does not have CAD as the cause of symptoms or may have very mild CAD. Such patients are most often spared the cost, risk, and discomfort of a