Relationship of Stress Test Findings to Anatomic or Functional Extent of Coronary Artery Disease Assessed by Coronary Computed Tomography Angiography-Derived Fractional Flow Reserve

Abstract

Background. In the United States, functional stress testing is the primary imaging modality for patients with stable symptoms suspected to represent coronary artery disease (CAD). Coronary computed tomography angiography (CTA) is excellent at identifying anatomic coronary artery disease (CAD). The application of computational fluid dynamics to coronary CTA allows fractional flow reserve (FFR) to be calculated noninvasively (FFRCT). The relationship of noninvasive stress testing to coronary CTA and FFRCT in real-world clinical practice has not been studied. Methods. We evaluated 206 consecutive patients at Loyola University Chicago with suspected CAD who underwent noninvasive stress testing followed by coronary CTA and FFRCT when indicated. Patients were categorized by stress test results (positive, negative, indeterminate, and equivocal). Duke treadmill score (DTS), METS, exercise duration, and chest pain with exercise were analyzed. $\text{Lesions}\ge 50\%\text{stenosis}$ were considered positive by coronary CTA. $\text{FF}{\text{R}}_{\text{CT}}<0.80$ was considered diagnostic of ischemia. Results. Two hundred and six patients had paired noninvasive stress test and coronary CTA/FFRCT results. The median time from stress test to coronary CTA was 49 days. Average patient age was 60.3 years, and 42% were male. Of the 206 stress tests, 75% were exercise (70% echocardiographic, 26% nuclear, and 4% EKG). There were no associations of stress test results with $\text{CAD}>50\%$ or $\text{FF}{\text{R}}_{\text{CT}}<0.80$ ( $p=0.927$ and $p=0.910$ , respectively). Of those with a positive stress test, only 30% (3/10) had $\text{CAD}>50\%$ and only 50% (5/10) had $\text{FF}{\text{R}}_{\text{CT}}<0.80$ . Chest pain with exercise did not correlate with $\text{CAD}>50\%$ or $\text{FF}{\text{R}}_{\text{CT}}<0.80$ ( $p=0.66$ and $p=0.12$ , respectively). There were no significant correlations between METS, DTS, or exercise duration and FFRCT ( $r=0.093$ , $p=0.274$ ; $r=0.012$ , $p=0.883$ ; and $r=0.034$ , $p=0.680$ ; respectively). Conclusion. Noninvasive stress testing, functional capacity, chest pain with exercise, and DTS are not associated with anatomic or functional CAD using a diagnostic strategy of coronary CTA and FFRCT.