The significance of atrial monophasic action potentials for monitoring rat cardiac allograft rejection.

BACKGROUND

Changes in the monophasic action potential may be used for detecting early acute rejection in the transplanted rat heart.

METHODS

Heterotopic heart transplantations were performed in allogeneic and syngeneic rats. During atrial pacing, monophasic action potentials were simultaneously recorded in the right atrium and ventricle of the transplanted hearts on postoperative days 1, 3, and 5. The amplitude and duration of monophasic action potentials, atrioventricular conduction time, and cardiac intervals were analyzed. Histopathologic examination for rejection was performed on postoperative days 1, 3, and 5.

RESULTS

In the allogeneic group, monophasic action potential amplitude progressively decreased, and monophasic action potential duration gradually increased after heart transplantation in the atrium and ventricle. With rejection, the amplitude decreased to a greater extent, and monophasic action potential duration increased to a greater extent in the atrium than in the ventricle on day 3. The atrioventricular conduction time increased on day 5, but the cardiac interval did not change. An inverse correlation between histopathologic grade and the monophasic action potential amplitude, and a positive correlation between histopathologic grade and the monophasic action potential duration existed for both the atrium and ventricle. These electrophysiologic and histopathologic changes were not observed in the syngeneic group.

CONCLUSIONS

We conclude that right atrial monophasic action potentials may be a useful and reliable indicator of early acute heart transplant rejection.