Three-dimensional distribution of myocardial fibrosis in the new J-2-N cardiomyopathic hamster: comparison with electrocardiographic findings.

Using the new J-2-N strain of cardiomyopathic hamster obtained by cross-breeding Bio 14.6 and Golden hamsters, we investigated the three-dimensional distribution of ventricular myocardial fibrosis and compared it with electrocardiographic (ECG) changes. Twelve-lead ECG recordings were made by our own method. The hearts were cut into serial sections and subjected to light microscopic examination. The distribution, density, and volume of myocardial interstitial fibrosis and replacement fibrosis due to myocardial degeneration (F%) were visualized three-dimensionally using the TRI system (TRI; Three-Dimensional Reconstruction Image; Ratoc System Engineering, Tokyo, Japan). Thirty-two J-2-N hamsters were divided into two groups; one group comprised 17 animals with normal hearts and normal ECG findings similar to those of Golden hamsters, and the other group of 15 hamsters had dilated hearts and abnormal ECG findings. In the normal hearts, the F% values for the right ventricle, left ventricle, and ventricular septum were 6.4 +/- 0.94, 6.5 +/- 0.95, and 6.5 +/- 0.98 (mean +/- SD), respectively. The dilated hearts showed marked fibrosis, which was distributed mainly in the middle layer of the left ventricle and the ventricular septum. The corresponding F% values for the hamsters with cardiac enlargement were 19 +/- 2.6, 19 +/- 1.8, and 22 +/- 3.2 (mean +/- SD), respectively. Replacement of myocytes by fibrosis seemed to correspond to abnormal Q waves in the anterior chest leads and left axis deviation of the QRS complex.