Transendocardial Delivery of Extracellular Myocardial Markers by Using Combination X-ray/MR Fluoroscopic Guidance: Feasibility Study in Dogs

Abstract

To demonstrate the feasibility of using a combination of x-ray fluoroscopic and magnetic resonance (MR) fluoroscopic (ie, x-ray/MR fluoroscopy) guidance for left ventricular (LV) catheterization and transendocardial delivery of extracellular tissue markers. Experiments were performed in six dogs by using an x-ray/MR fluoroscopy system. The arterial guide wire and catheter were advanced into the heart with x-ray fluoroscopic guidance. The dogs were injected with 0.5, 1.0, and 2.0 mL of iohexol. For passive catheter tracking, a steady-state free precession MR imaging sequence was used. A steerable dual-lumen catheter was used to transendocardially inject a mixture of gadodiamide (0.05 mol/L) plus Evans blue dye (3%). An electrocardiographically gated dual-inversion-recovery MR imaging sequence was used to visualize the myocardial delivery of the gadodiamide-blue dye mixture. A high concentration of gadodiamide (0.5 mol/L) was used to demarcate the borders of the area of interest, or "hit the target." Blood pressure, heart rate, and oxygen saturation were measured before and after the intervention. Analysis of variance, Scheffé, and paired Student t tests were used for data analysis. LV catheterization via arterial access was feasible with two-dimensional x-ray fluoroscopic and three-dimensional MR fluoroscopic guidance. Delivery of the gadodiamide-blue dye mixture and the consequences of the procedure were monitored with MR imaging. Gadolinium-enhanced regions were bright on T1-weighted MR images, but they varied in size as a function of injectant volume. The mean sizes of these regions were 1.5% +/- 0.6 of the LV after the 0.5-mL injection of the mixture and 7.0% +/- 0.5 of the LV after the 2.0-mL injection (P <.001, Scheffé test). The corresponding mean sizes of the blue dye-enhanced regions were 2.3% +/- 0.6 and 8.3% +/- 0.4, respectively (P <.001). A high concentration of gadodiamide caused signal intensity loss around the gadolinium-enhanced regions. Transendocardial delivery of potential therapeutic solutions is feasible with x-ray/MR fluoroscopic guidance. The injection catheter can be navigated with MR imaging guidance to hit the target.