From an economic standpoint, definitive recognition of the patient at very low risk for cardiac events is an important objective. Downstream costs in relation to the suspected disease process should then be minimal. The studies that led to our understanding of the role of myocardial perfusion imaging in risk stratification were performed before routine use of ECG-gating. Knowledge of poststress and rest LVEF should add considerably to the precision of risk-stratification. Healthcare providers and clinicians know that myocardial perfusion imaging is not infallible, however, and need to be observant for objective signs of clinical instability.
Many patients have mildly to moderately abnormal scans.
Figure 2 shows a reversible defect inferiorly and inferoseptally, in the distribution of the right coronary artery. O'Keefe et al,6 Iskandrian et al,7 and Marwick et al8 have all shown that prognosis in patients with small defects is excellent with aggressive medical therapy and without surgical or percutaneous intervention. Shaw et al evaluated this in a large multicenter study of patients with chest pain syndromes suggestive of CAD.10 About 5000 patients went directly to angiography, and a similar number had a perfusion study first. Of this second group, only patients with abnormalities on perfusion imaging were referred to angiography. Although patients in the angiography-first group had a higher rate of revascularization, clinical outcomes were the same.