Abstract 12836: Quantification of Coronary Microvascular Resistance using Angiographic Images for Volumetric Flow Measurement
Background: Structural coronary microcirculation abnormalities are important prognostic determinants in clinical settings. However, an accurate assessment of the index of microvascular resistance (IMR) requires the use of an invasive wire technique to measure coronary flow velocity. A first-pass distribution analysis (FPA) technique to measure volumetric coronary blood flow has previously been validated. The purpose of this study was the in vivo validation of the IMR measurement technique using FPA for flow measurement.
Methods: 12 anesthetized swine (37±6 kg) were instrumented with a transit-time ultrasound flow probe on the proximal segment of the LAD. Adenosine (400μg/kg/min) was used to produce maximum hyperemia. Contrast material injections (3 ml/sec for 3 sec) were made into the left coronary ostium during image acquisition. The images were corrected for x-ray scatter before logarithmic transformation. A region of interest in the LAD arterial bed was drawn to generate time-density curves. Volumetric blood flow measurements (Qa) were made in the LAD with the use of a time-density curve and the consideration that blood was momentarily replaced with contrast during the injection. Volumetric blood flow from the flow probe (Qp), coronary pressure (Pa) and right atrium pressure (Pv) were continuously recorded. Flow probe based IMR (IMRp) and angiography based IMR (IMRa) were measured as Pa-Pv divided by Qp and Qa, respectively. Furthermore, microspheres (50–100μm) were gradually injected into the LAD to create a model of microvascular dysfunction.
Results: A total of 258 measurements of Qp, Qa, IMRp and IMRa were made. Qa showed a strong correlation with the reference standard Qp (Qa=0.90Qp +6.6 ml/min, r2=0.91, p<0.001). IMRa correlated linearly with IMRp with good correlation coefficient (IMRa=0.88IMRp+0.05 mmHg/ml/min, r2=0.91, p<0.001). Additionally, the Bland-Altman analysis showed a close agreement between IMRa and IMRp.
Conclusion: An angiographic technique that does not require a wire for quantification of IMR was validated using a swine animal model. This study provides an angiographic method to measure IMR that can potentially be used to evaluate the microvascular condition during routine coronary arteriography.
- © 2010 by American Heart Association, Inc.