Biomedical subjects

W G Kim

Publications and source records attributed to W G Kim.

58 records · Page 4Linked to original sources

PubMedDate not supplied

Analysis of the interventricular pressure waveform in the moving-actuator total artificial heart.

Right and left filling pressures are important parameters in the automatic control of a total artificial heart (TAH) within normal physiologic ranges. Our TAH is composed of a moving actuator, right and left ventricles, and an interventricular space (IVS) enclosed by a semirigid housing. During operation of the TAH, the IVS volume is changed dynamically by the difference between the ejection volume of one ventricle and the inflow volume of the other. We measured the interventricular pressure (IVP) waveform by using a pressure sensor and analyzed the relationship between the IVP and the preload condition. From in vitro and in vivo experiments, we found that the measured filling pressures were linearly related to the negative peak value of the IVP. Additionally, we found that we could use the time interval from actuator start to the positive peak value of the IVP (outflow valve opening) as a useful parameter to estimate the blood filling volume of the diastole ventricle.

Animals↗

PubMedDate not supplied

Chronic heart failure model with sequential ligation of the homonymous artery and its diagonal branch in the sheep.

We report a reliable chronic heart failure model in sheep using sequential ligation of the homonymous artery and its diagonal branch. After a left anterior thoracotomy in Corridale sheep, the homonymous artery was ligated at a point approximately 40% of the distance from the apex to the base of the heart, and after 1 hour, the diagonal vessel was ligated at a point at the same level. Hemodynamic measurements were done preligation, 30 minutes after the homonymous artery ligation, and 1 hour after diagonal branch ligation. The electrocardiograms were obtained as needed, and cardiac function was also evaluated with ultrasonography. After a predetermined interval (2 months for five animals and 3 months for two animals), the animals were reevaluated in the same way as before, and were killed for postmortem examination of their hearts. All seven animals survived the experimental procedures. Statistically significant decreases in systemic arterial blood pressure and cardiac output and increases in pulmonary artery capillary wedge pressure were observed 1 hour after sequential ligation of the homonymous artery and its diagonal branch. Untrasonographic analyses demonstrated variable degrees of anteroseptal dyskinesia and akinesia in all animals. The data from animals at 2 months after coronary artery ligation showed significant increases in central venous pressure, pulmonary artery pressure, and pulmonary artery capillary wedge pressure. Left ventricular enddiastolic dimension and left ventricular end-systolic dimension on ultrasonographic studies were also increased. Electrocardiography showed severe ST elevation immediately after the ligation and pathologic Q waves were found at 2 months after ligation. The thin walled infarcted areas with chamber enlargement were clearly seen in the hearts removed at 2 and 3 months after ligation. In conclusion, we could achieve a reliable ovine model of chronic heart failure using a simple concept of sequential ligation of the homonymous and diagonal arteries. This animal model was comparable to the clinical situation.

Animals↗

PubMedDate not supplied

SPUU-PEO-heparin graft copolymer surfaces. Patency and platelet deposition in canine small diameter arterial grafts.

The influence of an SPUU-PEO-Heparin (B-PEO-HEP) copolymer coated blood contacting surface on patency and platelet deposition in small diameter (4 mm i.d.) Biomer grafts was investigated using a canine model. Grafts were implanted in the bilateral carotid and femoral arteries. B-PEO-HEP coated grafts still showed patency after 3 days. Control Biomer grafts occluded before 24 hr. (postoperatively). SEM of the luminal surfaces of the Biomer grafts demonstrated large amounts of adherent platelets with distorted morphologies, while B-PEO-HEP grafts did not. In platelet studies, B-PEO-HEP grafts showed significantly less platelet adhesion than Biomer grafts. The improved blood compatibility of B-PEO-HEP graft co-polymer coatings attests to their usefulness for coating or casting.

Animals↗

PubMedDate not supplied

A solar cell system for extension of battery run time in a moving actuator total artificial heart.

An implantable total artificial heart (TAH) system has strong dependence upon the external battery performance for operation. Even under sophisticated battery management control, the usable external battery performance continues to decrease, which limits TAH performance. One of the ways to overcome this energy problem is to use a solar system (SS). An SS can provide electrical power for the partial TAH drive or battery recharge. This article presents a new concept for use of the solar cell for obtaining double external battery performance. To achieve it, numeric simulations were carried out to obtain the proper magnitude of solar parameters. In the TAH used, the battery power for a cardiac output of 4-6 L/min is approximately 17 W/20 min. From simulated results, the optimal power and voltage of the SS were found to be 7 W, Voc = 27 V in the case of the 24 V motor. Each solar cell includes Voc = 0.5 V, Isc = 37 mA/cm2, FF (fill factor) = 0.77, and efficiency = 10%. Based on the simulation, the effect of solar power capacity on battery run time was studied. With use of 6.5 W SS (W 304 x H 245 x D 16 mm, 1.1 kg), battery performance decreased in vitro from 100% (fully charged) to > 55% vs 0% in the conventional battery system after 20 min operation. However, it dropped to below 20% when using W SS (W 192 x H 192 x D 16 cm, 0.6 kg). The results showed doubled battery run time could be obtained compared with a system without the SS. It was concluded that the proposed SS can be put to practical use as a future energy source for a TAH.

Biomedical Engineering↗