Abstract 16927: Cardiovascular Magnetic Resonance Stress Perfusion Imaging Predicts One Year Outcomes Following Equivocal or Uncertain Stress Study

Introduction: Patients with equivocal nuclear stress test (SPECT) results are at higher risk for cardiac events compared to those with normal studies. Cardiovascular magnetic resonance stress perfusion imaging (SCMR) identifies individuals with coronary artery disease (CAD) with high sensitivity and specificity, with excellent spatial resolution, and without ionizing radiation. The utility of SCMR testing is uncertain in individuals with prior equivocal stress results. Hypothesis: SCMR provides high prognostic capability to risk stratify patients after equivocal or uncertain SPECT studies. Methods: We retrospectively analyzed patients from 2011 to 2019 with equivocal or uncertain SPECT studies subsequently referred for SCMR within a 6 month window. Equivocal studies included qualifying wording such as significant artifact or technical difficulty. Uncertain studies included documented suspicion of false positive or false negative results. Adverse outcomes were defined as cardiovascular death or obstructive CAD found on unplanned coronary angiography (CA). Results: 151 patients met inclusion criteria: mean age 58, male 88 (58%). At one year, the negative predictive value of SCMR was 0.97; 122 patients with negative SCMR had a total of 4 events including 1 cardiovascular death and 3 obstructive CAD on CA. 27 patients had positive SCMR for ischemia, of which 9 patients were referred for CA and all demonstrated obstructive CAD. 18 patients were medically managed without adverse events. 2 patients were noted to have non-diagnostic SCMR and subsequent CA showed no significant CAD. Conclusion: Following equivocal or uncertain SPECT, SCMR demonstrated high 1-year prognostic capability with negative predictive value of 0.97 for adverse outcomes and high positive predictive value for obstructive CAD. SCMR may represent a reasonable, noninvasive option should additional risk stratification be required in this clinical setting.

Abstract 14381: Patient-specific Fluid Structure Interaction Simulations of Anomalous Origins of Right Coronary Arteries in Adults Correlate With Measured Instantaneous Wave-free Ratio

Introduction: Anomalous coronaries are associated with ischemia and sudden death, but the recommendation to undergo surgery is often uncertain, especially for asymptomatic individuals with an anomalous aortic origin of the right coronary artery (AAORCA). For risk stratification, dobutamine-stress instantaneous wave-free ratio (iFR) is increasingly used. Meanwhile, advances in fluid-structure interaction (FSI) modeling have enabled the simultaneous simulation of blood flow and tissue deformation that may elucidate the mechanism of ischemia in AAORCA. Hypothesis: We hypothesized that the iFR simulated by patient-specific FSI models of AAORCA correlates with the measured iFR at rest and dobutamine-stress, and the hemodynamic mechanism is mainly due to the intramural geometry. Methods: Using the Simvascular software package, we constructed 6 FSI models of the AAORCA which encompassed the aortic root, the intramural course (if present), and coronary outlets coupled to lumped parameter networks that included the dynamic microvascular compression. Each model was customized to the patients’ computed tomography angiography, vitals, and cardiac output. Results: All 6 AAORCAs had an interarterial course, and all but one had an intramural course. Measured iFRs ranged from 0.98 to 0.95 at rest, and from 0.95 to 0.80 with dobutamine-stress. The FSI model yielded realistic pressures and flows waveforms (Fig. 1). After we tuned the resistances to achieve flow rates at stress to be triple those at rest, the FSI simulations adequately matched the measured iFR (r = 0.85, RMSE = 0.04). Conclusions: Patient-specific FSI modeling is a promising non-invasive tool to assess the hemodynamic effects of AAORCA including the intramural course. However, the iFR’s sensitivity to the flow rate suggests a future role for quantitative stress-perfusion imaging to augment the iFR measurements for AAOCA risk stratification.

CMR applications

Assessment of cardiac morphology, function, and pathology requires the use of different pulse sequences (spin echo, gradient echo, hybrid echo), preparation pulses to manipulate image contrast, and data acquisition strategies such as parallel imaging, single-shot versus segmented acquisition, or contrast versus non-contrast imaging techniques. This chapter presents some of the main cardiac applications: morphology and function, stress perfusion imaging, viability assessment using late gadolinium enhancement, flow quantification, angiography, and fat suppression techniques. For each application, a description of its use within the clinical context is provided, along with the main sequence parameters and their effect on image contrast, acquisition time, and image quality.