Digital Radiographic Quantification of Myocardial Blood Flow Around a Transmyocardial Laser Channel in Rabbit Hearts

Microheterogeneity of regional myocardial blood flows in low-perfused rat hearts evaluated by double-tracer digital radiography

Using (3)H- and (125)I-labeled desmethylimipramine (DMI) for regional flow tracers, we established a two-time measurement method for the spatial pattern of myocardial perfusion in cross-circulated rat hearts. Myocardial extractions and retentions of these tracers were confirmed to be satisfactory; however, the latter were less than 90% after 3 min at a perfusion rate of 2.9 ml/min/g, limiting the present application to a short-time perfusion measurement. Distributions of myocardial depositions were separated by subtraction digital radiography with 400-microm pixel resolution. Its feasibility was examined by regression analysis between local deposition densities of (3)H- and (125)I-DMI injected simultaneously. The slope, y-intercept, and correlation coefficient (r) of the regression line were 0.98+/-0.04, 0.02+/-0.04, and 0.95+/-0.03, respectively, indicating the validity of the present image subtraction technique. The spatial pattern of myocardial perfusion in response to flow reduction was evaluated by the injections of (3)H- and (125)I-DMI, respectively, before and after a nearly 70% flow reduction. A significant correlation between normalized density distributions of these tracers was found in both subepicardium (r=0.77+/-0.12) and subendocardium (r=0.73+/-0.20), indicating the stable pattern of myocardial perfusion. However, the coefficient of variation of tracer densities showed a decrease of subendocardial flow heterogeneity from 35+/-15% to 31+/-16%. Thus, flow differences between originally high- and low-flow regions in subendocardium were reduced on a relative basis during low perfusion.

Pretreatment With Transmyocardial Revascularization Might Improve Ischemic Myocardial Function Performed With Cell Transplantation

BACKGROUND

Cells transplanted into the myocardial infarct areas might be lost because of the lack of blood supply to these myocardium areas. The hypothesis that pretreatment with angiogenic therapy induced by transmyocardial revascularization (TMR) might improve ischemic myocardial function, followed by cell transplantation was tested.

METHODS AND RESULTS

After the ligation of the left anterior descending coronary artery, rats were treated with TMR. Two weeks, embryonic stem cells were transplanted into an injured heart. Four weeks after cell transplantation, cardiac function was assessed by homodynamic measurements. Capillary density and infarct size in the infarct myocardium were measured by using a previous experimental method. Graft histology and morphology was also evaluated. Four weeks after the operation, myocardial infarct (MI) rats treated with TMR and cell transplantation showed significantly higher cardiac function in hemodynamic measurements (p < 0.01) than that of MI rats receiving cell transplantation or TMR alone. A significant increase in capillary density and reduction in infarct size was observed in the MI rats that received a combined therapy (p < 0.01).

CONCLUSION

Pretreatment of an infarct region of the heart with angiogenesis induced by TMR can enhance the efficacy of a cell graft and attenuate the progression of cardiac dysfunction in the rat model.