Abstract 20524: Assessment of Coronary Microcirculation in a Swine Animal Model
Background: Coronary microvascular condition has important prognostic implications. Although several different dynamic indices, such as coronary flow reserve (CFR), zero-flow pressure (Pzf), true microvascular resistance (TMR) and angiography based microvascular resistance (IMRa) have been developed, the reliabilities of them are still not clarified.
Methods and Results: 15 anesthetized swine were instrumented with a transit-time ultrasound flow probe on the proximal segment of LAD. A coronary pressure wire was advanced into the distal segment of LAD. Adenosine was used to produce maximum hyperemia. Microspheres (50–100μm) were gradually injected into the LAD to create microvascular dysfunction. An extravascular occluder was placed on the proximal LAD to produce an epicardial stenosis. Contrast material injections were made into the left coronary during image acquisition. Volumetric blood flow from the flow probe (Q), coronary pressure (Pa), distal coronary pressure (Pd), right atrium pressure (Pv) and ECG were continuously recorded. CFR was calculated as the ratio of blood flow at hyperemia to baseline. The instantaneous Q was plotted against the simultaneously measured Pd, and the X-intercept of the slope was calculated as Pzf. Angiography based blood flow (Qa) was calculated by using a time-density curve based on the first-pass distribution analysis technique. TMR and IMRa were determined by dividing Pa-Pv by Q and Qa, respectively, during hyperemia. A total of 268 measurements of CFR, Pzf, TMR and IMRa were made. Two series of ROC curves were made: (1) normal epicardial artery model (N model) and (2) epicardial 75% area stenosis model (S model). The areas under the ROC curve for CFR, Pzf, TMR, IMRa were 0.885, 0.800, 0.921, 0.883 and 0.693, 0.698, 0.783, 0.772, respectively. Especially in S model, both TMR and IMRa were significantly more reliable indices to detect the microvascular deterioration compared with CFR and Pzf.
Conclusion: Compared with CFR and Pzf, TMR and IMRa provided a more accurate assessment of the microcirculation. And this reliability was more predominant in case where the epicardial stenosis existed. Thus, angiography based IMR may be a less invasive method for specific assessment of coronary microvascular condition.
- © 2010 by American Heart Association, Inc.