Alterations in sheep fetal right ventricular tissue with induced hemodynamic pressure overload

We report on the cellular and molecular effects of acute and chronic hemodynamic overload on the fetal sheep heart. In one fetus of a twin gestation, the pulmonary artery was banded to create a condition of hemodynamic pressure overload in the right ventricle. The effects of this overload on the right ventricle (RV), left ventricle (LV), and intra-ventricular septum (IVS) of the heart were studied and compared to that in a control, unbanded twin fetus. At the cellular level, the histological data showed that both the size of the nuclei and the overall cell size of cardiac myocytes were increased after five days of banding; although, with one hour of banding no effects were detected at the cellular level. Based on prior studies on connexins which showed their involvement in differentiation, remodeling, and response to load we looked at their expression in control and experimental hearts. At the molecular level, changes in expression of connexin isoforms, the main gap junction protein in the heart, were observed after both one hour and five days of banding. Changes were observed in expression of connexins 40, 43, and 45. For connexin 43 there was a significant reduction confined to the right ventricle, in the chronically treated fetus, whereas, connexins 40 and 45 expression decreased after acute overload. These early molecular changes are significant because the "functional syncytium" of the myocardium is established through the gap junction connections. Alterations in connexin isoform expression affect the development, mechanical, and electrophysiological properties of the heart muscle. These changes may contribute to the ultimate result of continued hemodynamic stress on the right ventricle: heart failure.

Chronic alterations in cardiac mechanics after fetal closed heart operation

Pulmonary artery banding was performed in 8 fetal sheep at 125 days' gestation to evaluate the feasibility of fetal closed cardiac operation. At 135 days' gestation, the fetuses were delivered and the cardiac mechanics were evaluated using a modified Langendorff isolated heart preparation. Two of the 8 fetuses aborted spontaneously 2 and 7 days after operation. Six fetuses (75%) survived the 10 days after delivery. The left ventricular cardiac mechanics in the banded fetuses (group I) were compared with those in 8 control fetuses (group II). All fetal hearts in both groups displayed a significant volume-pressure relationship. The volume-pressure curve was found to be shifted upward and to the left in the fetal hearts after pulmonary artery banding. The left ventricles subjected to increased in utero preload secondary to pulmonary artery banding were capable of generating greater peak systolic and developed pressures. Because the fetal heart manifests a Starling type of preload reserve, as such, it demonstrates that the possibility exists for subsequent fetal development to be altered by intrauterine intervention.

Antithymocyte gamma globulin, low-dosage cyclosporine, and tapering steroids as an immunosuppressive regimen to avoid early kidney failure in heart transplantation

Cyclosporine is a powerful immunosuppressive agent that unfortunately has significant renal toxicity. Two risk factors associated with a high incidence of kidney failure in patients receiving cyclosporine have been described in the literature. In an effort to decrease the possibility of renal toxicity with the use of cyclosporine, we use low-dosage cyclosporine, antithymocyte gamma globulin, and tapering dosages of steroids as an immunosuppressive regimen. Twenty-one patients had orthotopic heart transplants from January 1985 to January 1986. Sixteen of 21 patients or 70% had at least one high risk factor for kidney failure. There were no episodes of acute kidney failure, and the blood urea nitrogen and creatinine levels that were recorded over an average of 8.5 months per patient did not increase significantly from preoperative values. Seventeen of 21 or 81% of the patients are alive and functioning fully. The incidence of rejection per patient was 0.9, and there were no biopsy-proven severe rejections. One patient died at 5 months; the autopsy showed generalized moderate rejection. There were 0.24 episodes of infection per patient, with one patient who died from Pneumocystis pneumonia. With this immunosuppression protocol, early postoperative kidney dysfunction was avoided. The incidences of rejection and infection were within acceptable range, and the quality of life in the 17 survivors is excellent.