Contribution of hypoxia to the development of cardiomyopathy in hamsters

Objective: It has been hypothesized that microvascular spasms cause cardiomyopathy. To elucidate the contribution of hypoxia to the development of cardiomyopathy, the newly-developed hypoxia tracer. Tc-99m nitromidazole, was applied to detect myocardial hypoxia in a hamsters model. Methods: Tc- 99m nitromidazole (180 MBq) and I-125 iodoantipyrine (370 kBq) were injected into cardiomyopathic Syrian hamsters or control hamsters at age 10, 25 and 40 weeks (n=6 in each group). The myocardial uptake of Tc-99m nitromidazole was measured and dual tracer autoradiography was performed. Results: Histologic study revealed that the cardiomyopathic hamsters at age 10, 25 and 40 weeks were in the myocytolytic stage, the fibrotic and healing stage, and the hypertrophy and dilation stage, respectively. Tc-99m nitromidazole uptake was significantly greater in the cardiomyopathic hamsters than in the controls at age 25 weeks (cardiomyopathic hamsters, 33.3 ± 4.7% g dose/g; control, 25.2 ± 3.1), whereas there were no significant differences between both strains at age 10 and 40 weeks. The quantified concentration of 1-125 iodoantipyrine in the cardiomyopathic hamster at age 10 weeks was significantly lower than that in the controls. When the Tc-99m nitromidazole uptake was normalized by 1-125 iodoantipyrine concentrations, the cardiomyopathic hamsters at age 25 and 40 weeks showed significantly greater uptake than the controls. Conclusion: The myocardium in cardiomyopathic hamsters was hypoxic at the fibrotic and healing stage and may be hypoxic at the hypertrophy and dilatation stage. This may contribute to the development of cardiomyopathy.