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Deposition of blood elements on vacuum-formed ventricles in calves. A gross and electron microscopic study
P A DeFeo1, D Wurzel, W Wildevuur
1Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Insights
The Philadelphia Heart System showed minimal thrombus buildup in calf implants over 128 days. This artificial heart device demonstrated stability and reduced thrombogenicity, indicating its potential for long-term use.
Area of Science:
- Biomedical Engineering
- Cardiovascular Research
- Materials Science
Background:
- Thrombogenicity of artificial heart devices is a critical challenge.
- Minimizing thrombus formation is essential for device longevity and patient safety.
Purpose of the Study:
- To evaluate the thrombogenicity of the Philadelphia Heart System.
- To assess thrombus accumulation and pseudoneointima ingrowth in a chronic animal model.
Main Methods:
- Implantation of the Philadelphia Heart System in calf left and right ventricles.
- Evaluation of explanted hearts using gross examination, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
- Assessment of blood-contacting surfaces for thrombus and tissue ingrowth over periods up to 128 days.
Main Results:
- Visible thrombus was primarily located at inflow/outflow valves and atrial cuff.
- A circumferential band of white thrombus around the blood diaphragm junction increased in width over time (1-3 mm at 128 days).
- Microscopic deposits of blood elements, mainly platelets, were uniformly distributed and stable over time; pseudoneointima formation was observed on the Dacron graft.
Conclusions:
- The Philadelphia Heart System demonstrated a capacity for minimizing thrombus accumulation.
- The device remained stable for up to 4 months, suggesting favorable hemocompatibility.
- Further investigation into optimizing graft coverage and reducing localized thrombus may enhance performance.
Abstract:
The thrombogenicity of the Philadelphia Heart System was evaluated by implanting left and right ventricles in calves for periods ranging from 1.5 hours to 128 days. Explanted hearts were examined grossly and by scanning and transmission electron microscopy for accumulation of thrombus and ingrowth of pseudoneointima. Visible material was essentially limited to inflow and outflow valves, atrial cuff, and a circumferential band of white thrombus around the junction of the blood diaphragm with the housing. The band was barely visible at 33 days, but was 1 to 3 mm wide at 128 days. SEM examination revealed microscopic deposits of blood elements, mostly platelets, that were present between 10 days and 128 days. The deposits were rather uniformly distributed over the blood contacting surface and remained constant over time. At 128 days, the Dacron (Meadox Medical, Oakland, NJ) graft was partly covered by a thin layer of tissue composed of multiple layers of cells separated by collagen. New blood vessels were frequently found, but fibrin-rich thrombus was present in some areas. Thus, this system was capable of minimizing thrombus accumulation and remained stable for 4 months.