The Journal of Thoracic and Cardiovascular Surgery, Vol 98, 266-274, Copyright © 1989 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Sequentially paced heterotopic heart transplant in the left chest provides improved circulatory support for the failed left ventricle. A potential biologic bridge to orthotopic transplantation
ST Raza, SK Tam, SC Sun, R Laurance, B Berkovitz, R Shemin and LH Cohn
Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass.
Acute experimental transplantation of an allograft heart in a heterotopic
position was performed in 14 sheep. The donor heart was implanted in the
left side of the chest with left atrial, aortic, and pulmonary artery
anastomoses. Hemodynamic studies were performed to evaluate the physiologic
effects of the procedure, particularly when recipient left ventricular
failure was produced by inflow and outflow obstruction. Pacing techniques
were developed and tested to coordinate the rhythm of the two hearts either
synchronously or sequentially with variable intervals between
depolarization of the two hearts. Hemodynamic studies were performed to
evaluate the rhythm that would most optimize the physiology. The cardiac
index remained essentially unchanged when the dominant circulatory support
was shifted from recipient left ventricle to donor left ventricle by
producing recipient left ventricular failure (3.79 +/- 0.6 to 3.30 +/- 0.8,
p = no significant difference). Consistent and reliable paced rhythms were
achieved in each case. The cardiac index was significantly higher when the
hearts were paced sequentially rather than synchronously (3.76 +/- 0.5
versus 3.29 +/- 0.5, p less than 0.04). Allograft donor hearts small in
size or slightly inadequate otherwise, which may be unsuitable for
orthotopic heart transplantation, may still be used heterotopically for
short-term support. Their use would maximize the use of all donor organs
and the survival of patients awaiting a suitable organ. Further, it may
also be possible to use sequentially paced xenografts heterotopically for
short-term left ventricular assistance as a bridge to orthotopic heart
transplantation.