New Model for the Assessment of Transcatheter Aortic Valve Replacement Devices in Sheep

Preclinical Models of Cardiac Disease: A Comprehensive Overview for Clinical Scientists

For recent decades, cardiac diseases have been the leading cause of death and morbidity worldwide. Despite significant achievements in their management, profound understanding of disease progression is limited. The lack of biologically relevant and robust preclinical disease models that truly grasp the molecular underpinnings of cardiac disease and its pathophysiology attributes to this stagnation, as well as the insufficiency of platforms that effectively explore novel therapeutic avenues. The area of fundamental and translational cardiac research has therefore gained wide interest of scientists in the clinical field, while the landscape has rapidly evolved towards an elaborate array of research modalities, characterized by diverse and distinctive traits. As a consequence, current literature lacks an intelligible and complete overview aimed at clinical scientists that focuses on selecting the optimal platform for translational research questions. In this review, we present an elaborate overview of current in vitro, ex vivo, in vivo and in silico platforms that model cardiac health and disease, delineating their main benefits and drawbacks, innovative prospects, and foremost fields of application in the scope of clinical research incentives.

6-Month Evaluation of a Transcatheter Aortic Valve (Myval) in a Novel Ovine, Supra-Aortic Banding Model

The aim of the study was to evaluate a balloon expandable transcatheter heart valve (THV) system (Myval) at 6-month follow-up in ovine banding model. Eleven THV systems were implanted via carotid approach. There were 2 procedure-related deaths and 2 premature deaths. At 6 months all valves that completed follow-up (n = 7) were functional, with no significant regurgitation, calcification, thrombi, or vegetation. Mean pressure gradient was 21.9 ± 11 mm Hg, maximum velocity = 3.3 ± 1 m/s, and ejection fraction was 53.3 ± 6%. Myval THV showed optimal hemodynamic performance and biocompatibility.

Establishing Background Pathologic Changes of Valve Replacement Surgery in Sheep

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.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13239-021-00563-6.