Characterization of the natural history of cervical heterotopic heart transplantation with echocardiography

Background: Limitations of the dog model of orthotopic heart transplantatio n to study rejection include the need for extracorporeal circulation and tr ansfusions. Heterotopic cervical heart transplantation may improve on these limitations. It is not known whether the natural history after heterotopic transplant is similar to that after orthotopic grafting. Methods: Twenty-one dogs underwent cervical heterotopic heart transplantati on. Serial echocardiographic studies were performed 1 to 3 hours after surg ery; at 24 hours, 48 hours later, and immediately before killing (5 to 7 da ys). Results: LV diastolic and systolic areas were elevated immediately,after tr ansplantation (4.95 +/- 1.49 cm(2) and 3.36 +/- 1.18 cm(2) respectively) bu t decreased at 24 hours (3.93 +/- 1.20 cm(2), p = 0.0003 and 2.44 +/- 0.96 cm(2), p = 0.16). Thereafter, a progressive increase in LV diastolic and sy stolic areas was observed until sacrifice (5.53 +/- 2.20 cm(2) and 4.59 +/- 2.14 cm(2), p < 0.001 vs 24 hours). LV fractional area shortening (FAS) an d fractional volume change were depressed immediately after transplantation (28.2 +/- 12.8% and 40.4 +/- 12.3%, respectively), but increased at 24 hou rs (35.7 +/- 10.0%, p = 0.11 and 50.3 +/- 4.0%, p = 0.02). FAS decreased at 48 hours to 19.6 +/- 11.1% (p = 0.01 vs 24 hours). The centractility index es were markedly reduced before killing (FAS = 14.0 +/- 8.2% and LVEF = 18. 4 +/- 1.3%, p < 0.0005 vs 24 hours). The thickness of the interventricular septum increased from 11.9 +/- 2.0 mm at baseline to 14.4 +/- 4.2 mm before sacrifice (p = 0.007). Conclusion: The evolution of dogs after heterotopic cervical heart transpla nt is comparable to that after the more standard orthotopic graft. Consider ing its multiple practical advantages including the easy echocardiographic follow-up; heterotopic transplantation may become a very practical model to use for the study of rejection after heart transplantation.