Telemetric detection of cardiac allograft rejection. Correlation of electrophysiological, histological, and biochemical changes during unmodified rejection

Intra-abdominal mismatched heterotopic cardiac allograft transplantation without immunosuppression was performed in eight pigs. Postoperatively, daily electrophysiological studies were carried out either with exteriorized temporary epicardial pacing wires (n = 4) or by a telemetrically controlled implanted pacemaker connected to permanent epicardial pacing leads (n = 4). Electrophysiological studies data were correlated with histopathologic and biochemical findings from daily myocardial biopsies. Electrophysiological studies revealed no significant alteration of sinus or atrioventricular node function, refractoriness, or ventricular pacing threshold. However, ventricular voltage amplitude, measured through the electrodes, decreased steadily with time in all donor hearts and was significantly correlated with histopathologic rejection grade (p less than 0.001) and with adenosine 5'-triphosphate (ATP) depletion (p less than 0.001). Ventricular voltage amplitude less than 75% of baseline occurred 4.5 +/- 1.5 days after transplantation, and this decreased voltage amplitude coincided with a moderate to severe (Grade 2 or 3) histological rejection pattern with a sensitivity of 89% (17 of 19) and a specificity of 77% (17 of 22). Similar changes in voltage amplitude were not found in control hearts. Myocardial tissue ATP values fell significantly from control values with early (Grade 1) rejection (p less than 0.05). Evidence for oxygen free radical injury was indicated by a rise in conjugated dienes of free fatty acids; this increase in diene level occurred 4.3 +/- 1.2 days postoperatively and then regressed during the terminal stages.(ABSTRACT TRUNCATED AT 250 WORDS)

A new technique of experimental heterotopic cardiac transplantation

Heterotopic cardiac transplantation is a useful method for studying allograft rejection. In this study a new technique of cardiac transplantation was carried out, which involved retroperitoneal anastomoses of the donor ascending aorta and main pulmonary artery with the recipient abdominal aorta and inferior vena cava respectively. The procedure was simple and effective and was accomplished with minimal operative mortality and postoperative morbidity. The method allows better access to the allograft for repeated open myocardial biopsies, obviating the limitations of transvenous fluoroscopically directed endomyocardial biopsy. This technique of retroperitoneal heterotopic cardiac transplantation has important advantages compared with similar procedures performed in the neck, abdomen, or thorax.

Effect of low level direct current on in vivo tumor growth in hamsters

A preliminary study has been carried out on the effect of low level direct current on tumor growth using an experimental tumor model developed from an amelanotic melanoma (T1-4) in the hamster. An inoculum of 2 X 10(6) viable cells was injected s.c. on day 0; on day 7 the tumor-bearing animals were randomly divided into treatment and control groups. On days 7 through 11 inclusive, the treatment group was subjected to electrical current (direct current) at levels from 0.1 to 2.4 mA, for 1 h/day under general anesthesia. Control groups were subjected to the same procedures, with the exception that the electrodes were not connected to the current source. On day 14, the animals were killed and autopsied; their tumors were removed, weighed, and sectioned. Treated tumors decreased in mass (as a percentage of controls) from 89% at 0.1 mA to 2% at 2.4 mA. Increased necrosis of the treated tumors was noted macroscopically and microscopically. On histological examination, it was observed that a thin rim of viable cells remained around the periphery after treatment even at the highest current levels. Similar results were obtained with both stainless steel and platinum-30% iridium electrodes. In separate experiments where the animals were allowed to survive after a treatment period (1 h/day for 5 days at 2.4 mA), the viable cells at the periphery developed into tumors whose mass at 28 days posttreatment averaged only 52% of that of the control tumors. The mechanism of growth reduction is unknown but hyperthermia was shown not to be a factor.