From clinical trials to public health policy: the path from imaging to screening

Perfusion Impairment in Patients with Normal-appearing Coronary Arteries: Identification with Contrast-enhanced MR Imaging

PURPOSE

To prospectively determine the feasibility of using first-pass magnetic resonance (MR) imaging to distinguish between myocardial segments in patients with coronary artery disease (CAD) of different degrees of obstruction and those in patients with normal-appearing coronary arteries.

MATERIALS AND METHODS

The study was approved by the institutional ethics committee, and all patients provided informed consent. First-pass contrast material-enhanced MR imaging was performed at rest and after the infusion of dipyridamole in 37 patients (29 men, eight women; mean age, 57.2 years +/- 10.5 [standard deviation]) who had positive exercise test results or a clinical history of CAD. Myocardial segments were divided into five groups according to the degree of obstruction in the supplying artery. Signal intensity upslope, peak signal intensity, and time to peak signal intensity, as well as hyperemia-to-rest (HR) ratios for each of these three variables, were analyzed for each segment by using a generalized linear model.

RESULTS

Signal intensity upslope in patients with normal coronary arteries at angiography was significantly higher than that in patients with CAD (P < .001). Signal intensity upslope for segments in patients without CAD was significantly different from that for normal-appearing segments in patients with CAD (P < .001). Signal intensity upslope (P < .05) and peak signal intensity (P < .01) enabled the differentiation of segments with more than 70% reduction in luminal diameter from those in all other groups. HR ratios demonstrated findings that were similar to those obtained by using each signal intensity variable alone.

CONCLUSION

First-pass MR imaging can be used to distinguish segments with different degrees of obstructive CAD. Importantly, MR imaging can help identify segments with impaired perfusion and normal-appearing coronary arteries in patients with CAD and can demonstrate obstructive lesions in other territories.

Cost-effectiveness of new tests to diagnose and treat coronary heart disease

This article provides a review of the methods applied in defining cost-effectiveness as well as a review of the limited evidence base for defining incremental cost-effectiveness ratio of cardiovascular imaging when compared with an office-based risk assessment using the Framingham risk score. To date, there is a growing body of evidence that suggests that screening may be cost-effective in patients with an intermediate Framingham risk score. However, much of this evidence is derived from decision models or simulations that may not adequately represent the use of imaging evidence as it may be derived from "real world" or randomized trial data. Thus, we await additional evidence from large cohort studies or well-controlled clinical trials to define optimal economic efficiency strategies that may include the use of cardiovascular imaging in the screening of patients at risk for coronary heart disease.