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At least 199 records · Page 11Linked to original sources
PubMed1995

Transient pressure at closing of a monoleaflet mechanical heart valve prosthesis: mounting compliance effect.

An in vitro experimental study was performed to investigate the mounting compliance effect on the occluder closing dynamics and the transient pressure at the closing of the mitral Medtronic Hall (MH) mechanical heart valve (MHV). The closing velocity and the transient pressure were simultaneously measured at heart rates of 70, 90, 120, and 140 beats/minute with cardiac outputs of 5.0, 6.0, 7.5, and 8.5 liters/minute, respectively. The experiment was conducted under simulated physiologic ventricular and aortic pressures in a pulsatile mock flow loop. The characteristics of the transient pressure were investigated by detailed mapping of the transient pressure field in the atrial chamber using high frequency pressure transducers. Simultaneous measurements of the occluder closing velocity and the transient pressure around the seat stop of the MH showed that the transient pressure generated on the inflow side dropped below the vapor pressure of liquid during the occluder's sudden deceleration at closing. The amplitude of the transient pressure reduction (TR) was proportional to the occluder approaching velocity. The development of the transient pressure in the rigid and flexible mountings were significantly different. In the rigid mounting (RM), the pressure was reduced below the liquid's vapor pressure and maintained below -350 mmHg for approximately 180 microseconds. Strong signals of high frequency pressure oscillations (HPO) were recorded in the transient pressure traces. The timing of the HPO was found to be consistent with that of the cavitation bubble collapse as observed by others. In the flexible mounting (FM), TR also occurred, but recovered quickly and was followed immediately by a positive pressure spike. Relatively weak HPO appeared in the transient pressure trace. The mapping of the transient pressure field showed that both the transient pressure reduction (on the major orifice side) or rise (on the minor orifice side) as well as the HPO were locally generated near the valve occluder surface. The transient pressure attenuated with distance away from the occluder surface. The HPO were detectable as far as 40 mm away from the occluder surface. The rigid mounting pressure signals showed characteristically two occurrences of high frequency pressure oscillations. The HPO with smaller amplitude occurred first after the initiation of the TR, followed by a burst of strong HPO at about 450 microseconds. It is believed that they were the result of the collapse of cavitation bubbles. The strong HPO did not appear in the flexible mounting signals. The study indicated that the mounting compliance played a significant role in the MHV cavitation inception and the subsequent bubble growth. It also suggested the possibility of detecting the cavitation by using a high frequency pressure transducer positioned in the atrial chamber.

Biomechanical Phenomena↗
PubMed1980

[Pregnancy in women wearing a heart valve prosthesis: 5 case histories (author's transl)].

The study of a personal series of five pregnancies and the review of 130 cases published enabled us to recall the physiological, clinical and therapeutic sides of the "pregnancy-heart valve prothesis" combination. Maternal mortality remains at 3%; morbidity, essentially in the form of haemorragic or thrombo-embolic accidents, comes to 45%. We insist on the importance of a pregnancy planned and accepted both by the cardiologist and the obstetrician as contraception is a difficult problem with these patients, classical oestroprogestative methods and intra-uterine devices being too much of a risk. An intake of a progestagen in small doses combines efficiency with innocuity.

Adult↗
PubMed2001

[Use of cytochrome C in the prevention of myocardial reperfusion injury during heart valve prosthesis implantation under conditions of extracorporeal circulation].

Cytochrome C used at the postischemic period causes a rapid reestablishment of coronary circulation, hemodynamic parameters, prevents activation of lipid peroxidation in reoxygenation of the heart after prolonged total myocardial ischemia in patients with acute bacterial endocarditis in whom the prostheses of heart valves had been fulfilled. Parallel with the positive inotropic effect, Cytochrome C reduces the postloading and, as a result, transfers the cardiac muscle to a more profitable regimen. At the end of the myocardial ischemia period Cytochrome C provides rapid and effective recovery of the bioelectrical function of the heart, improves its pumping function, thus allowing the dose and duration of inotropic stimulation of the myocardium at the postischemic period to be reduced, lowers pulmonary resistance and finally leads to less postoperative intrahospital lethality from acute heart failure.

Animals↗