PubMed · 8325048
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E A Agathos, A Starr. 1993. Mitral valve replacement.. https://doi.org/10.1016/0011-3840(93)90015-9
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Although clinically effective, conventional mitral valve surgery has recently been scrutinized because of its high-cost nature. Technologic advances have developed a large assortment of endoscopes and related instruments to treat almost any part of the body using this minimally invasive approach. Consumers have realized that the minimally invasive approach has many benefits including less pain, more rapid wound healing, and faster recovery. Successes seen with video-assisted thoracoscopy along with consumer demand have gained the interest of cardiac surgeons. Recently, a port-access approach to mitral valve repair or replacement has been developed. This article describes this innovative surgical approach, discusses indications and contraindications to the surgery, reviews benefits of the surgery, and examines one institution's approach to the care of this patient population.
BACKGROUND AND AIMS OF THE STUDY: This study compares the cavitation potential of prosthetic heart valves based on valve closing dynamics. METHODS: A laser sweeping technique measured valve closing dynamics (average closing velocity and deceleration) immediately before valve closure. A high-fidelity, piezoelectric pressure transducer was mounted proximal to the mitral valve and measured the high-frequency pressure fluctuations caused by cavitation bubble formation and collapse after valve closure. The band-pass filtered root mean squared (RMS) value of the mitral pressure signal was used as a measure of cavitation intensity. The combination of these two techniques allowed the direct correlation of valve dynamics and cavitation intensity for each valve closure. The effects of three parameters on prosthetic heart valve dynamics and cavitation were examined: valve geometry (Medtronic Hall and Björk-Shiley Monostrut), occluder material (pyrolytic carbon and Delrin), and gap width between the occluder and housing. A dimensional analysis was also performed to investigate the general form of the relationship between valve dynamics and cavitation intensity. RESULTS: For all of the valves investigated in this study, the RMS pressure increased (signifying an increase in cavitation) as the average closing velocity and deceleration increased. In order to compare the cavitation potential of the valves, the RMS pressure was estimated at specific closing velocities using the linear regression of RMS pressure versus average closing velocity for each valve. The effects of valve geometry, occluder material and gap width were then examined at high valve loading conditions (closing velocity of 4.0 m/s). For both pyrolytic carbon and Delrin, the Medtronic Hall valves had significantly higher RMS pressures than did the Björk-Shiley Monostrut valves. For a given valve geometry, the pyrolytic carbon occluder had a significantly higher RMS pressure than the Delrin occluder. The valve gap width did not have a significant effect on RMS pressure. The dimensional analysis revealed the general relationship among average closing velocity, occluder material properties and cavitation intensity. CONCLUSIONS: The results presented here contribute to our fundamental understanding of cavitation on mechanical heart valves.
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