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PubMedDate not supplied

In vivo evaluation of a permanently implantable thermal ventricular assist system.

The System 7 pump/actuator/engine combination has demonstrated biologic compatibility and physiologic effectiveness and responsiveness in five TVAS in vivo studies. The recent 75-day implant supports the feasibility of extended reliability of the system components. Postoperative system maintenance was necessary only because of the nonhermetic design of System 7. However, the ability to pump 11 l/min at 120 beats/min, synchronize at beat rates of 144 beats/min, and pump against mean arterial pressures of more than 150 mmHg while maintaining hematologic and biochemical values within physiologic range sets a very optimistic stage for System 8 hardware. A System 8 concept is shown in Figure 14. The System 8 hardware will include a thermal salt package capable of providing completely untethered circulatory support for a nominal 8-h period. Recharge will be accomplished with a transcutaneous transformer in 1 h. Thermal management problems become minimal, with an average energy input of 15.8 W (peak of 24.9 W). The human preclinical testing of System 8 will start in 1988.

Animals↗
PubMed1996

[Terminal cardiac failure. Circulatory assist devices].

There is a great variety of circulatory assist devices because of the diversity of clinical applications, age of the patient, required performances, energy used for activation... The oldest assistance device is intra-aortic balloon counterpulsation. There are two groups of devices: light, partial and short-term assist devices versus total, sophisticated and long-term machines. Examples of the first group are the Hemo-pump and Centrifugal pumps. Many of the second group are pneumatically driven: either external heterotopic uni/biventricular assist devices (Thoractec, Medos) or implantable heterotopic left ventricle (TCI), or orthotopic and implantable total artificial heart (Jarvik-CardioWest). The aim to assist the left ventricle over a longer period of time has lead laboratories to develop electrically powered ventricles implanted in the abdominal wall like the Novacor or HeartMate Systems. Because these new devices make patients more independent, they open the way for chronic applications as an alternative to transplantation.

Adult↗
PubMed1976

The use of intra-aortic balloon pumping in cardiac surgical patients.

Experience in the use of intra-aortic balloon pumping for moribund cardiac surgical patients over a 10-month period is presented. Of the 11 patients reported, 5 survived and have left hospital. The mechanism of diastolic augmentation of the circulation is discussed and the details of its clinical use are outlined.

Adult↗
PubMed1989

Technique and results with a roller pump left and right heart assist device.

During the last 10 years we have inserted a roller pump-driven left heart assist device in 72 patients and a right heart assist device in 7 patients for profound heart failure after a variety of cardiac surgical procedures. In addition a percutaneous left heart assist device (transseptal insertion of left atrial cannula via a femoral vein) was employed in 5 patients with profound cardiogenic shock after acute myocardial infarction. Thirty patients (41.7%) were weaned from the left heart assist device and 21 (29.2%) were discharged from the hospital. Two patients (40.0%) were weaned from the right heart assist device, but both later died during the postoperative period. Of the 5 patients in whom a percutaneous left heart assist device was inserted, 4 underwent successful emergency percutaneous transluminal coronary angioplasty, but all 5 patients died. Causes of death included severe coagulopathy, irreversible extensive myocardial infarction and cardiac failure, refractory arrhythmias, severe "shock" lung, and multisystem failure. In summary, satisfactory results can be achieved with a roller pump-driven left and right heart assist device for severe postoperative heart failure. Further experience should be obtained with the percutaneous technique to assess its efficacy in treating patients with acute myocardial infarction and cardiogenic shock.

Assisted Circulation↗
PubMed1986

Use of a venous assist device after repair of complex lesions of the right heart.

Sixteen patients underwent hemodynamic evaluation of a venous assist device after complex operations on the right side of the heart. The device consists of an inflatable abdominal binder attached to a Jobst extremity pump causing intermittent external compression of the abdomen. In addition, six of these patients were evaluated using total lower body compression for comparison. Modifications of the Fontan procedure were performed in 14 patients, mitral valve anuloplasty and tricuspid valve replacement in 1 patient and reconstruction of the right ventricular outflow tract for treatment of pulmonary atresia with intact septum in 1 patient. The patients' ages ranged from 23 months to 31 years (mean 10.7 +/- 1.8 years). Systemic blood pressure, right and left atrial pressures, heart rate and arterial-mixed venous oxygen saturation difference were recorded in each patient with and without the device in place. With the venous assist device, mean systolic pressure increased from 95 +/- 4 to 122 +/- 3 mm Hg (p less than 0.05) and diastolic pressure rose from 57 +/- 3 to 70 +/- 3 mm Hg (p less than 0.05). Left atrial pressure increased from 7 +/- 1 to 15 +/- 1 mm Hg and right atrial pressure from 15 +/- 1 to 23 +/- 1 mm Hg (both p less than 0.05). In addition, arterial-mixed venous oxygen saturation difference decreased from 29% without the device to 23% with the device in place (p less than 0.05). Total lower body compression gave similar results to intermittent abdominal compression alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Baylor multipurpose circulatory support system for short- to long-term use.

A multipurpose circulatory support system has been developed as both a temporary and permanent device in total artificial hearts (TAHs) and ventricular assist devices (VADs). The multipurpose concept was derived from the development of a totally implantable electromechanical, one-piece TAH. The blood pump is pneumatically driven in short-term use and is electromechanically driven in long-term or permanent use. Both TAH and VAD versions consist of the same components, except for the actuation mechanism. The common components are a compact pumping chamber with the same configuration, a blood contacting surface biolized with gelatin, a pusher-plate, a Hexsyn rubber diaphragm (University of Akron, Akron, OH) and bovine pericardial valves. Both TAHs and VADs have 63 ml of stroke volume, and the VADs are compact compared with other available investigational device exemption devices. Currently, 1 week survival has been achieved using the electromechanical TAH and 2 week survival using the electromechanimcal VAD without anticoagulation. Results suggest that the currently developed system could be applied in varied patients as a temporary device after cardiotomy, a long-term device for bridge to transplantation, or a permanent device for end-stage heart disease.

Assisted Circulation↗
PubMedDate not supplied

An approach to reducing hemolysis in an axial-flow blood pump.

In an attempt to decrease hemolysis caused by an axial-flow blood pump, we studied whether specific speed (Ns) at a design point (determined by flow in m3/min, pump head in m, and pump speeds in rpm), should be kept within the existing engineering standard range (1000 < Ns < 2500) or whether pump speed should be reduced to a minimum (Ns < 1000). Four pumps (A: 14,000 rpm, B: 18,000 rpm, C: 22,000 rpm, and D: 26,000 rpm), each with an impeller 11.8 mm in diameter, were designed to accommodate a flow rate of 5 L/min and a pressure head of 100 mmHg. At this design point, the Ns of each pump was calculated as A:758, B:974, C:1191, and D:1407. Pump performance was observed, and the total efficiency of each pump was calculated. The hemolysis index (HI) was calculated after simultaneous testing in duplicate of all four pumps using fresh goat blood (anticoagulated with citrate-dextrose solution) in a closed mock-loop circuit. Total efficiency of each pump was calculated as A:49%, B:50%, C:45%, and D:22%. In the first hemolytic test, HIs were measured as A:0.066, B:0.18, and C:0.13; a water seal failed in pump D. In the second test, HIs were B:0.077, C:0.0499, and D:0.12; a bearing failed in pump A. It is concluded that a lower level of hemolysis is associated with a pump speed in the minimum range at the design point, even though Ns is outside the standard range.

Animals↗
PubMed2004

Developments in mechanical support as a bridge to cardiac transplant.

With the increasing incidence of congestive heart failure and limited numbers of donor hearts for transplantation, mechanical circulatory support devices are being used with greater frequency in Canada. The indications for device use, types of available pumps and centres performing these procedures are presented. A review of the results of use of these devices in Canada indicates that they may be a reasonable alternative for patients who might otherwise die without intervention. The cost implications of more widespread use of these pumps are not insignificant and must be compared with other life-saving technologies.

Assisted Circulation↗
PubMedDate not supplied

Cardiac assistance by atrial or ventricular cardiomyoplasty.

Dynamic cardiomyoplasty was conceived to enhance cardiac performance by assisting myocardial contraction. Technically, this procedure consists of placing a pedicled latissimus dorsi muscle flap around the heart and subsequent muscle electrostimulation in synchrony with ventricular systole. Three types of dynamic cardiomyoplasty can be considered. (1) Atrial or ventricular reinforcement is accomplished by wrapping the latissimus dorsi muscle flap around the heart to support hypokinetic or akinetic areas secondary to congenital or acquired diseases. The atrial reinforcement may be performed to improve atrial output after Fontan-type procedures. (2) Ventricular substitution is performed to replace a portion of the ventricular wall. Autologous pericardium is used to create a neoendocardium and facilitate hemostatic closure of the ventricle. The pedicled latissimus dorsi is then secured to replace the resected myocardium. (3) The two previous techniques of ventricular substitution and reinforcement are combined. This reconstructive procedure, which normalizes the ventricular geometrical shape, is particularly useful after extended cardiac resections, such as is done in treatment of large ventricular aneurysms, cardiac tumors, or echinococcal cyst formations. At present, improvement in ventricular function has been obtained in 12 patients at our institution. Preoperative severe cardiac dysfunction was present in all of these patients (New York Heart Association functional class III or IV). Postoperative echocardiography, multigated acquisition scan, and hemodynamic studies demonstrate an improvement in ventricular function and no impairment of ventricular compliance by the muscle flap. After a mean follow-up period of 18 months, all patients are in functional class I or II. We believe that dynamic cardiomyoplasty prolongs and improves the quality of life of patients suffering from severe chronic and irreversible myocardial dysfunction by improving ventricular contraction and limiting cardiac dilatation.

Assisted Circulation↗
PubMed1989

[A case of biventricular assist with centrifugal pumps after operation of ventricular septal perforation following acute myocardial infarction].

We applied biventricular assist using centrifugal pumps on a 64-year-old male who has undergone an operation against post-myocardial infarction with ventricular septal perforation. The pump flow was maintained at the level of 2.5 l/m2 in CI, and the pulse pressure 30 to 50 mmHg with IAPB. Complete hemostasis has been achieved prior to use heparin to control the patient's ACT around 200 sec. on the third pumping day. The patient's cardiac function improved in a few days at the beginning, but did not recover enough for weaning from the assist devices. He died on the 8th pumping day, and the autopsy revealed massive old myocardial infarction which is considered to be the major obstacle against the recovery of the cardiac function. There was no edema in any organs. Centrifugal pumps are very useful for ventricular assist in availability and in economy. Its efficacy is comparable with pulsatile ventricular assist devices especially when applied with IABP though there still exists controversy as for the superiority of pulsatile flow in ventricular assist.

Assisted Circulation↗
PubMed1986

[Anatomical and hemodynamic evolution at midpoint follow-up with the assisted heart in heterotopic heart transplantation. Apropos of 21 cases].

Between November 1978 and March 1985, 27 cardiac transplant operations were performed at the Arnault Tzanck Institute; Barnard's heterotopic method was used in 21 cases. In 16 cases, follow-up was prolonged to assess the effects on the assisted receiving heart. In the first postoperative hours the receiving heart is often more effective than the graft. There were no pathological consequences due to the two different rhythms. The increased pressures in the right cavities of the receiving heart decreased but sometimes this look several weeks. The volume of the left atrium decreased. Left ventricular contraction was unchanged in some cases but in others it improved significantly. This was accompanied by an average decrease of 20 mm in echocardiographic left ventricular end diastolic internal dimension. This technique of heterotopic assistance seems particularly suitable for advanced stages of cardiomyopathy with stage IV pulmonary hypertension.

Assisted Circulation↗
PubMedDate not supplied

Anatomic interaction between the right and left ventricles during univentricular and biventricular circulatory support.

Left heart unloading with a prosthetic ventricle has been shown to result in a leftward shift of the interventricular septum, changing the geometry and possibly the performance of the right heart. The effects of univentricular and biventricular support on septal shifting were compared. In 10 anesthetized pigs Thoratec left (LPV) and right prosthetic ventricles (RPV) were connected from the LV apex to the ascending aorta and the right atrium to the pulmonary artery, respectively. Each heart was instrumented with ultrasonic crystals for LV and RV free wall-to-septum dimensions, RV and LV pressures, and cardiac output (CO). LV and RV end-diastolic pressure and dimensions (EDD), and peak systolic pressures (PSP) and dimensions were analyzed on a computer under control conditions, and during EKG synchronized RPV, LPV, and biventricular (BPV) support. During LPV the septum shifted to the left, and during RPV it shifted to the right, with LVEDD and RVEDD changing in opposite directions under each condition. With BPV septal position changed in the same way as with LPV, although to a smaller degree. The amount of septal movement was linearly related to the change in transseptal gradient produced by the prosthetic ventricles. Each 10 mmHg decrease in left minus right transseptal pressure gradient resulted in a 22% reduction (r = 0.83) in LVEDD and a 27% increase (r = 0.87) in RVEDD at end-diastole, and a 2% reduction (r = 0.87) in LV dimensions and a 2% increase (r = 0.83) in RV dimensions at peak systole.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗