Key result
Sham mitral and aortic valve replacement surgeries in sheep resulted in an average of 4.2 renal infarcts, which was not significantly different from the 4.7 infarcts observed in non-surgical controls.
Why the study?
Sheep are the standard preclinical model for assessing novel heart valve safety, but the anatomic and pathologic effects of invasive surgery, including cardiopulmonary bypass, remain unknown.
Does sham valve replacement surgery with cardiopulmonary bypass cause background anatomic and pathologic changes in sheep compared to no surgery?
Does sham valve replacement surgery with cardiopulmonary bypass cause background anatomic and pathologic changes in sheep compared to no surgery?
Sham valve replacement surgery with cardiopulmonary bypass in sheep is associated with background anatomic and pathologic changes, notably renal infarcts, which are exacerbated by additional surgical interventions but not significantly different from non-surgical controls, serving as a critical baseline for preclinical device testing.
Answers are grounded in this paper and cite their sources.
Sham controls in sheep may isolate surgical effects from novel valves; leaves open standardized preclinical benchmarks before clinical translation.
Purpose Sheep are the standard preclinical model for assessing safety of novel replacement heart valves, yet the anatomic and pathologic effects of invasive surgery, including those involving cardiopulmonary bypass (CPB), are unknown. Thus, we aimed to determine the gross, hematologic and biochemical effects of sham mitral and aortic replacement valve procedures in sheep to establish a useful control for evaluation of novel replacement valves. Methods Six control sheep were examined without any surgical intervention. Six sham mitral valve replacements (MVR) and six sham aortic valve replacements (AVR) were performed on 12 sheep. Complete blood counts and serum biochemistry were performed throughout the study. Sheep were sacrificed with a necropsy performed at 90 days. Results Renal infarcts (RIs) were the most frequently observed lesion, averaging 4.7 in control sheep, 2.5 with MVR and 5.8 with AVR. The number of infarcts strongly correlated with total estimated area of infarcted kidney (r = .84, p < .01). Additional cardiac interventions were significantly correlated with increased numbers of RIs (r = .85, p < .01). There was no correlation between number of RIs and time on CPB, or between AVR and MVR procedures. Conclusion The sheep model for AVR and MVR requires invasive surgery and CPB, which are associated with background anatomic and pathologic changes, especially in cases with additional surgical cardiac interventions. These findings serve as a critical control for future evaluation and development of novel replacement valves in order to distinguish device-related safety issues from expected outcomes of the surgical procedure and normal background changes in sheep.
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Faustich et al. (2021) studied Healthy sheep (preclinical model) (n=18). Sham mitral or aortic valve replacement surgery with cardiopulmonary bypass vs. No surgical intervention was evaluated on Average number of renal infarcts (p=0.96). Sham mitral and aortic valve replacement surgeries in sheep resulted in an average of 4.2 renal infarcts, which was not significantly different from the 4.7 infarcts observed in non-surgical controls.
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