Experimental

VII. Other cardiac assist devices

A. Prosthetic replacement of the right ventricular wall (1974)

Summary

The role of the right ventricle  (RV) in circulation, the function of the right ventricular myocardium, the contribution of the RV to normal hemodynamics, and the effects of damage to the RV on the circulation have been studied previously. This study was designed to test the relationship between the musculature and function of the RV. Since many types of congenital heart disease are now potentially correctable by surgery, the possibility of completely bypassing the RV is of particular importance. In our experiments, various portions the RV were excised and replaced with a prosthetic patch made of dacron and hemodynamic data were collected.

In acute experiments, 23 dogs were divided in 3 groups according to the amount of the resected RV free wall. Their survival (11/23 dogs successfully resuscitated from surgery) and data collected 3 hours after completion of surgery in these surviving dogs are shown below. There were only mild hemodynamic changes in the surviving dogs.

In chronic experiments, 10 dogs were studied. Approximately 75% of the wall of  the RV was removed and replaced by the patch, baseline data were recorded, dogs were allowed to recover. Six dogs died within 17 days after surgery from various causes. Hemodynamic data were again collected after approx. 4 and 7 months in the 4 surviving dogs. Their general health was good. Their hemodynamic function was normal and differed little from pre-operative hemodynamic values. The cineangiograms showed that the RV contracted and emptied well and during systole, the septum moved towards the RV space and the RV anterior wall moved toward the septum, reducing the RV volume.

Pathologic examination showed good healing along the suture line with smooth and well-organized fibrous layer of pseudo-intima, including a single-celled layer of endothelium over the blood/tissue surface covering. The patch was uniformly wrinkled with reduced surface area (to 35-45% as compared to 75% of the free wall at the time of surgery). This was accompanied by elongation of the remaining wall of the RV

The results reported here indicate that in dogs the LV alone, in the absence of a kinetic RV, is capable of maintaining normal hemodynamics (when the RV free wall is replaced by a non-distensible and non-contractile dacron patch.  

Publication:

Ventricular performance following ablation and prosthetic replacement of right ventricular myocardium. Sawatani, S; Mandell, G; Kusaba, E; Schraut, W; Cascade, P; Wajszczuk, W J; Kantrowitz, A. Trans Am Soc Artif Intern Organs. 20 B: 629-36, 1974.
 

B.  Dynamic Aortic patch – an auxiliary ventricle (1974)

Summary

The Dynamic Aortic Patch (DAP) is a permanent device, a prosthesis developed in this laboratory for implantation in the descending aorta. It is activated in a manner similar to the intra-aortic balloon. Initial problems with clot formation on its blood contact surface have been overcome and its hemodynamic effectiveness was established. In the present study emphasis is placed on materials and configurations which enhance long-term performance of the implant. Findings based on prolonged in vivo performance with this auxiliary ventricle (DAP) in dogs are presented. Different materials and configuration of the device and pumping durations were tested.

In the series of tests, using dynamic aortic patches with silicone rubber chambers and conduits, no material failure occurred in vivo.   However, in vitro testing indicated that the flex life of the material was limited to less than continuous use.   Devices, with segmented polyurethane pumping chambers and steel coil reinforced polyurethane conduits, performed satisfactorily, particu­larly when the conduit was attached at the end of the pumping chamber.   One animal from the second series, with the polyurethane implant activated for 16 months, is alive and healthy. Aortic tear at the implantation site was the most frequent cause of death.   By slackening the conduit and observing a careful double row suture technique, the incidence of aortic tear in the first post-operative month was considerably reduced.  

The commonest complications of the implantation procedure were intrathoracic infec­tion and infections at the transcutaneous connector.   While intrathoracic infections invariably proved fatal to the animal, infections at the transcutaneous connector were locally controlled without much difficulty.

Observations of the dynamic aortic patch post-mortem confirm the growth of a pseudointima layer on the dacron velour surface of the prosthesis and explain the lack of thromboembolism formation during the studies.

In the present investigation segmented polyurethane appears to be an excellent material for use in the DAP.    It should be noted that when the device functioned poorly, it was due to errors in design and construction, rather than material failure.    The end-feed configuration of the prosthesis lends itself well for long-term in vivo implantation and to continuous activation.

Publication:

Long-term in vivo testing of an auxiliary ventricle. Kiso I, Schraut W, Wajszczuk W, Moskowitz MS, Freed P, Kantrowitz A. Transactions - American Society for Artificial Internal Organs. 1974; 20 B:637-42.

C. Combined intra-aortic and intra-ventricular pumping in cardiogenic shock – 1978

Summary

Combined intra-aortic and intraventricular counterpulsation for treatment of experimental shock due to myocardial infarction, which was induced in 5 dogs weighing 25-35 kg by ligation of the left anterior coronary artery, is described. The technique is our own original development in which a spherical balloon of only about 5 ml capacity is used for intraventricular counterpulsation. The balloon is fixed to the end of a conventional catheter and it can he introduced into the left ventricle through the large vessels, avoiding thus the necessity of performing a major operation on open chest. By maintaining appropriate working conditions of the whole system (delays, filling time, beginning of the time of collapse of both balloons working in opposite phases: the intraventricular and the intra-aortic) it was possible to achieve a very favourable effect on the haemodynamics, with a nearly 40°/o rise in the aortic blood flow, increased aortic pressure by about 30% and only slight rise of the dP/dt by about 5°/o.

Combined  LVBP + IABP assistance results in a much more favourable haemodynamic effect that intra-aortic counterpulsation or intraventricular assistance alone, (which   increases significantly the requirements for oxygen). The size of the LV balloon should not exceed 1/4-1/5 of the LV ejection fraction.

Publication:

SIMULTANEOUS   INTRA-VENTRICULAR   AND   INTRA-AORTIC COUNTERPULSATION   IN   TREATMENT   OF   EXPERIMENAL   CARDIOGENIC SHOCK. R. J. Zochowski, M. J. Stopczyk, W. Wajszczuk. Kardiologia Polska, vol. 21, No. 4, 349-357, 1978

RYSZARD JACEK  2OCHOWSKI,  MARIUSZ  JAN  STOPCZYK*, WALDEMAR  WAJSZCZUK. Zastosowanie równoczesnego wspomagania wewnątrzkomorowego i wewnątrzaortalnego do leczenia  eksperymentalnego wstrząsu kardiogennego.
Kardiologia Polska, XXI, Nr. 4, 349-357, 1978

Z Kliniki Kardiologii Instytutu Chorób Wewnętrznych AM w Warszawie; kierownik: doc. dr hab. n. med. T. Kraska i z Sinai Hospital of Detroit and Wayne State University, Detroit, Michigan, USA

W pracy przedstawiono metodę skojarzonego zastosowania kontrapulsacji wewnątrzaortalnej i wspomagania wewnątrzkomorowego do leczenia cksperymentalnego wstrząsu zawałowego.

Opisana technika stanowi własne oryginalne rozwiązanie metodyczne, polegające na zastosowaniu do wspomagania wewnątrzkomorowego kulistego balona o pojemności tylko około 5 ml, który zamontowany na końcu konwencjonalnego cewnika daje się wprowadzić do światła lewej komory drogą przeznaczyniową, przez co pozwala uniknąć wykonywania dużego zabiegu operacyjnego na otwartej klatce. Przy zachowaniu odpowiednich warunków pracy obu systemów wspomagających (opóźnienia, czas wypełniania i początek okresu zapadania obu pracujących w przeciwfazie balonów: wewnątrzkomorowego i wewnątrzaortalnego) udało się osiągnąc nadzwyczaj korzystny efekt hemodynamiczny, wyrażający się wzrostem przepływu aortalnego o okolo 40%, rozkurczowego ciśnienia aortalnego o około 30%  przy nieznacznym tylko wzroście dP/dt o okolo 5%.

Skojarzone wspomaganie LVBP + IABP daje w rezultacie znacznie korzystniejszy efekt hemodynamiczny niż sama kontrapulsacja wewnątrzaortalna lub zwiększające w sposób istotny zapotrzebowanie tlenowe wspomaganie wewnątrzkomorowe.

WNIOSKI

1. Przedstawiony model eksperymentalny spełnia w pełni warunki badania wpływu krążenia wspomaganego na hemodynamikę wstrząsu kardiogennego.

2. Krążenie wspomagane przy zastosowaniu dwóch pracujących w przeciwfazie balonów, wewnątrzaortalnego i wewnątrzkomorowego przynosi korzystny efekt hemodynamiczny, wyraźnie większy niż w przypadku stosowania jedynie kontrapulsacji wewnątrzaortalnej (IABP) lub wewnątrzkomorowej (LVBP).

3. Zastosowanie do wspomagania wewnątrzkomorowego balona nieprzekraczającego 1/4-1/5 objętości wyrzutowej lewej komory jest całkowicie wystarczające dla osiągnięcia korzystnego efektu hemodynamicznego i czyni tą metodę możliwą do zastosowania bez otwierania klatki piersiowej.