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Influence of Contrast Agent Dose and Ultrasound Exposure on Cardiomyocyte Injury Induced by Myocardial Contrast Echocardiography in Rats¹

¹ From the Departments of Radiology (D.L.M., C.D.), Internal Medicine (Cardiology) (P.L., W.F.A.), Pathology (D.G.), and Cell and Developmental Biology (C.A.E.), University of Michigan Medical Center, 3315 Kresge III, 200 Zina Pitcher Pl, Ann Arbor, MI 48109-0553. From the 2004 RSNA Annual Meeting. Received August 25, 2004; revision requested October 29; revision received November 19; accepted December 20. Supported by U.S. Public Health Service grant EB00338, awarded by the National Institutes of Health, Department of Health and Human Services. Address correspondence to D.L.M. (e-mail: douglm{at}umich.edu).

View larger version (75K): [in a new window]   Figure 1. EB dye–stained (red fluorescent) cardiomyocytes. A, Photomicrograph of a formalin-fixed rat heart section visualized at confocal microscopy. Nuclei are counterstained with 4',6-diamidine-2-phenylindole (blue), which localizes all nuclei in all cells, including cardiomyocytes, neutrophils, and endothelial cells. Concentrations of blue 4',6-diamidine-2-phenylindole–stained nuclei represent inflammatory cell infiltration associated with the red EB dye–stained cardiomyocytes. B, Fluorescence photomicrograph of a fresh-frozen rat heart section. The stained cardiomyocytes and other structures such as an arterial wall (a) appear bright red. Scale bars represent 50 µm.

View larger version (83K): [in a new window]   Figure 2. Photomicrographs of cardiomyocyte injury in a formalin-fixed rat heart section stained with hematoxylin. A, Transmitted light image of the section shows an area of inflammatory cell infiltration outlined in blue. B, Fluorescence image of the same region shows EB-stained cells outlined in red. EB dye staining reveals injured cardiomyocytes in addition to cells in areas of inflammatory cell infiltration. Scale bars represent 50 µm.

View larger version (18K): [in a new window]   Figure 3. Graphs illustrate results of PRPA exposure-response experiments. A, EB-stained (fluorescent) cell counts in fresh-frozen rat heart sections are plotted against ultrasound PRPAs. B, Numbers of premature heartbeats recorded during myocardial contrast echocardiography of the rat hearts sampled in A. EB-stained cell count and number of premature heartbeats had a similar dependence on PRPA.

View larger version (22K): [in a new window]   Figure 4. Graph comparison of EB-stained (fluorescent) cell counts and numbers of premature heartbeats at end-systolic versus end-diastolic triggering. The cardiomyocyte injury was not significantly different between the two trigger points. At end diastole, the heart was partially refractory to further contraction, and this partial refraction led to a reduced number of premature heartbeats.

View larger version (22K): [in a new window]   Figure 5. Graphs illustrate results of contrast agent dose-response experiments. A, EB-stained (fluorescent) cell counts in fresh-frozen rat heart sections are plotted against contrast agent doses, with a nonlinear regression curve fitted to the data. B, Numbers of premature heartbeats recorded during myocardial contrast echocardiography of the rat hearts sampled in A. EB-stained cell counts and numbers of premature heartbeats increased rapidly with increasing contrast agent dose at low doses, but they leveled off at high doses.