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Biomedical subjects

W J Kolff

Publications and source records attributed to W J Kolff.

At least 253 records · Page 14Linked to original sources
PubMedDate not supplied

Residence time distributions in artificial ventricles.

The time that blood elements remain in an artificial ventricle determines the period during which these blood elements are exposed to damaging factors. We present, for the first time, preliminary studies on the residence time distribution (RTD) of a ventricle as a function of type and orientation of valves (Bjork-Shiley and polyurethane valves). We constructed an open loop mock circulation system which simulates the flow and pressure through the left ventricle, and a drive triggered injection unit which can inject a chemical tracer or radioisotope during one diastolic filling phase. RTD studies were done using a Tc-99m radionuclide tracer and a chemical tracer. A scintillation camera clearly showed the influence of backflow through the artificial heart valves, and the intraventricular washout. Results indicate that 42% of the fluid elements are expelled at the end of the first ventricular beat, i.e., 58% of blood elements stayed behind to experience the second beat; 36% of blood elements expelled in the second beat belonged to those in the first diastole; 17% in the third beat; and 5% in a subsequent number of beats. The RTD was found to vary with the position of the Bjork-Shiley (BS) valves.

Blood Flow Velocity↗
PubMedDate not supplied

Cost of home dialysis versus institutional dialysis.

An actual cost analysis in the summer of 1975 showed that under the most costly of circumstances possible, home dialysis is always much less costly than institutional dialysis. During the first year of dialysis, when a patient must go through the expensive part of being trained for home dialysis in the center and of having the equipment installed, home dialysis even then is between $5,000 and $10,000 less costly than center dialysis. In subsequent years, after the initial outlay, home dialysis will be between $8,000 and $13,000 less costly than center dialysis.

Community Health Centers↗
PubMedDate not supplied

Comparison of an extraaortic counterpulsation device versus intraaortic balloon pumping in severe cardiac failure.

A valveless, single orifice polyurethane ventricle was implanted on the brachiocephalic artery in sheep (n = 14) to provide extraaortic counterpulsation. In parallel, an intraaortic balloon was placed in the descending thoracic aorta. Both devices were pneumatically driven by a standard intraaortic balloon pump (IABP) console at a preload of 40 cc. Severe cardiac failure was induced with high dosages of esmolol. Measured parameters were aortic pressure (PA) and flow (QA), coronary flow (QC), and left ventricular pressure (PLV). Tension time index (TTI), total QA and QC, and end-diastolic aortic pressure (EDP) were computed to compare the efficacy of counterpulsation between assisted and unassisted conditions. Three conditions of inflation/deflation timing were examined: Normal timing (NT), early inflation (EI), and late deflation (LD). Results indicated that extraaortic counterpulsation device actuation yielded statistically significant increases in QC, and significant decreases in EDP and TTI for all timing conditions examined, when compared with unassisted conditions. Flow was significantly increased only for EI and NT timing conditions. Counterpulsation delivered with IABP yielded statistically significant increases in EDP for LD timing, and significant decreases in TTI for NT only. These results indicate that EACD is much less dependent on inflation/deflation timing when compared with IABP. The extraaortic counterpulsation device consistently increases QC and decreases TTI, which enhances the oxygen supply/consumption ratio (S/C) of the left ventricle. The intraaortic balloon pump does not significantly increase S/C in severe cardiac failure, and will increase afterload if deflation timing is not properly set.

Animals↗
PubMedDate not supplied

Evaluation of a stented polyurethane mitral valve prosthesis.

In the search for the perfect valve prosthesis, polyurethane has been used for its excellent physical properties, but thrombosis and embolism have been real problems. The authors investigated the performance and durability of a 23 mm vacuum formed polyurethane Tricuspid Semilunar Valve, in the mitral position. The valve was implanted in eight sheep using standard cardiopulmonary bypass and intermittent aortic cross clamping. Two early failures were due to valve tears. After modification of the manufacturing process, six further valves were implanted in six sheep. All were anticoagulated with warfarin. The valves were calcified on echocardiography and had increasing transvalvular gradients beginning 3 months postoperatively. All six survived and were killed 1-2.5 years after implantation. Despite gross calcification of the leaflets, medium-term function was good. Careful serial sections of brain showed no evidence of thromboembolism. Both kidneys contained small calcium emboli, but no evidence of infarction. Despite calcification, with good medium-term function and no cerebral emboli, this valve may find application in temporary cardiac assist devices.

Animals↗
PubMedDate not supplied

Molded double lumen silicone skin button for drivelines to an artificial heart.

A one-piece transfer molded double skin button allows two drivelines to pass through the skin and reduces the penetration area by 44%. The use of elastomer HP-100 (Dow Corning) without a reinforcing mesh allows some additional features not possible with hand lay-up techniques. These include "S" curved passages for the lines, double sealing rings within the passages, a sleeve, and a flange, all as one piece of silicone. The sealing rings prevent the leakage of air, create a pocket for a glue seal, and anchor the air line. The sleeve prevents the air lines from putting necrosis-causing pressure on the skin. The flange keeps the button from being pulled out, is covered with Dacron velour, and is a barrier against infection. The shape of the device allows the air lines to be tunneled under the skin and exited parallel to the skin.

Catheters, Indwelling↗
PubMedDate not supplied

Soft artificial ventricles for infants and adults, with or without a clamshell.

The quick connect system and mechanical disk valves used in total artificial hearts (TAH) are sources of thrombogenesis and blood damage. Our soft TAH, which has no quick connectors, can be squeezed and bent, making it easily implantable, and blood damage is reduced by the use of trileaflet and biflap polyurethane valves. The soft ventricles were made by vacuum forming, after which the pieces were welded together by radiofrequency heat sealing. A rapid clamshell can be pushed and slipped over the soft heart to prevent deformation of the ventricle. Three calves have had the 60 cc soft TAH implanted, both with and without a clamshell. The cardiac outputs were as high as 7 L/min, without a vacuum applied during diastole. Two lambs received the 20 cc TAH (as an acute experiment); it fit and functioned well. One healthy lamb received a 20 cc left ventricular assist device (LVAD) with a pulsating artificial atrium as a survival experiment. The lamb survived for 8 days, after which the device was removed and the lamb returned to the meadow. Thrombosis in the TAH was minimal, and the plasma free hemoglobin values in all the TAH and LVAD experiments were usually lower than 5 mg/dl and often lower than 2 mg/dl.

Adult↗
PubMedDate not supplied

In vitro ultrasound characterization of a polyurethane trileaflet valve.

Polyurethane synthetic trileaflet valves were compared with commercial prostheses in vitro, in a pulse duplicator using ultrasound to characterize the flow velocities and patterns. Flow-pressure drop behavior was in the middle range of other prosthetic valves. Diastolic regurgitant jets were located by color Doppler ultrasound, and there appeared to be some leakage through the leaflet fold at the commissure. Nevertheless, the closing volumes and closed valve leakage volumes were, on average, lower than other prosthetic valves. Systolic 20 Hz spectral oscillations detected with pulsed Doppler and continuous wave Doppler were attributed to leaflet flutter in the open valve.

Aortic Valve↗