Application of Hybrid Matrix Metalloproteinase-Targeted and Dynamic 201 Tl Single-Photon Emission Computed Tomography/Computed Tomography Imaging for Evaluation of Early Post-Myocardial Infarction Remodeling.

BACKGROUND: The induction of matrix metalloproteinases (MMPs) and reduction in tissue inhibitors of MMPs (TIMPs) plays a role in ischemia/reperfusion (I/R) injury post-myocardial infarction (MI) and subsequent left ventricular remodeling. We developed a hybrid dual isotope single-photon emission computed tomography/computed tomography approach for noninvasive evaluation of regional myocardial MMP activation with Tc-99m-RP805 and dynamic Tl-201 for determination of myocardial blood flow, to quantify the effects of intracoronary delivery of recombinant TIMP-3 (rTIMP-3) on I/R injury. METHODS: Studies were performed in control pigs (n=5) and pigs following 90-minute balloon occlusion-induced ischemia/reperfusion (I/R) of left anterior descending artery (n=9). Before reperfusion, pigs with I/R were randomly assigned to intracoronary infusion of rTIMP-3 (1.0 mg/kg; n=5) or saline (n=4). Three days post-I/R, dual isotope imaging was performed with Tc-99m-RP805 and Tl-201 along with contrast cineCT to assess left ventricular function. RESULTS: The ischemic to nonischemic ratio of Tc-99m-RP805 was significantly increased following I/R in saline group (4.03 +/- 1.40), and this ratio was significantly reduced with rTIMP-3 treatment (2.22 +/- 0.57; P=0.03). This reduction in MMP activity in the MI-rTIMP-3 treatment group was associated with an improvement in relative MI region myocardial blood flow compared with the MI-saline group and improved myocardial strain in the MI region. CONCLUSIONS: We have established a novel hybrid single-photon emission computed tomography/computed tomography imaging approach for the quantitative assessment of regional MMP activation, myocardial blood flow, and cardiac function post-I/R that can be used to evaluate therapeutic interventions such as intracoronary delivery of rTIMP-3 for reduction of I/R injury in the early phases of post-MI remodeling.