Abstract
The use of biological prosthetic valves has increased considerably in recent decades since they have several advantages over mechanical ones, but they still possess the great disadvantage of having a relatively short lifetime. An understudied phenomenon is the flutter effect that causes oscillations in the cusps, which is associated with regurgitation, calcification and fatigue, which can reduce even more the lifetime of bioproteses. In an experimental bench that simulates the cardiac flow, the behavior of a porcine and a bovine pericardium valves was recorded by a high-speed camera to quantify the oscillations of the cusps and an experiment using particle image velocimetry was conducted to study the velocity profiles and shear stresses and their relations with flutter. Results showed that the pericardial valve has lower values of frequencies and amplitudes compared to the porcine valve. Lower velocity values were found in the cusps that did not have flutter, but no relationship was observed between shear stress values and leaflet vibrations. These results may assist in future projects of biological prosthetic valves that have less flutter and longer lifespan.
Highlights
These findings in bovine pericardium are in agreement with other studies that found no oscillations at various flows (Rainer, Christopher, Sadler, & Hilgenber, 1979; Ionescu, 2014) or lower frequency vibrations (Louie et al, 1988; Avelar et al, 2017a).The higher thickness of the cusps, as verified in Table 1, besides higher values of elastic modulus may explain the greater resistance to flutter of the bovine pericardium (Patterson, Howard, & Thornton, 1996; Kalejs et al, 2009; Xiong et al, 2010; Avelar et al, 2017a)
Results differ from the findings of Moore and Dasi (2014), in which flutter was not found in a porcine valve in a similar glycerin solution, the authors studied a 25 mm valve with larger effective orifice area and, a smaller systolic peak velocity at 25 L min.-1, which may have caused the difference in results
The present work focused on the study of flutter in the cusps of a porcine and a bovine pericardium valve and its consequences on the flows in an experimental bench
Summary
The number of adults with heart valve malfunctions and diseases increase every year due to global population aging. The replacement of the biological heart valves with artificial ones has been used to solve part of the cardiovascular problems, such as valve regurgitation, stenosis, among others. Approximately 290,000 patients undergo cardiac valve replacement surgery, a number that is projected to reach 850,000 by the year 2050 (Hasan et al, 2014). Artificial valves still cause innumerous implications and patients have to deal with problems like calcification, possible infections, thrombosis, angina, and others (Dasi, Simon, Sucosky, & Yoganathan, 2009; Nachlas, Li, & Davis, 2017; Motta, Lintas, Fioretta, Hoerstrup, & Emmert, 2018). Studies on valve dynamics can help manufacturers to understand and solve future problems
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