Mechanical Auxiliary Ventricle Research Articles

Imaging of ventricular assist devices and their complications.

L efi ventricular assist devices (LVADs) are surgically implanted mechanical devices that perform the work of the left ventricle as a bridge to cardiac transplantation in patients with endstage heart failure. Insertion of an LVAD may unmask failure of the right ventricle, necessitating insertion of a night ventricular assist device (RVAD). The first ventricular assist device (VAD). a U-shaped, first-generation mechanical auxiliary ventricle (AVCO-Everett Research Laboratory. Everett, MA). was implanted in 1966 [11. Estimates have been made that, by the year 2010, approximately 70.000 patients a year may be eligible for VAD placement, at a cost of $ 17,000-50,000 a unit 12-4]. VADs have successfully provided ambulatory support for more than 500 days in a single patient [5]. With the severe shortage of organ donors, the implantable LVAD is being considered as a more permanent device for heart failure, as an alternative to transplantation. Reported complications from VAD placement include pneumothonax. hemothorax. infection. thromboembolism, bowel obstruction, and mechanical failure [69]. This essay reviews the radiographic and CT features of the Heartmate VAD (Thenmocardiosystems. Woburn. MA) and the Thonatec VAD (Thonatec Medical. Berkeley. CA) and their complications, based on the clinical course and imaging studies of 32 patients who underwent LVAD (ii = 32) and RVAD (ii = 8) placement at this institution between 1990 and 1996.

A Mechanical Auxiliary Ventricle

The mechanical auxiliary ventricle (MAV) is an avalvular, inseries left ventricular assist device (LVAD) comprised of a 60 cc Biomer blood pump implanted in the descending thoracic aorta, a percutaneous access device (PAD), and an external pneumatic drive. In four calves the MAV was implanted and activated intermittently for 192, 249, 423, and 785 days, respectively; no anticoagulants were administered. When the animals were killed, the implants were retrieved, and autopsies, including gross, light microscopic, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) examinations, were performed. The MAV was securely attached to the aorta in every animal. A thin, even smooth, pseudoneointimal layer (PNI) contiguous with the aorta at the level of the suture line covered the MAV's blood-contacting surface. Areas of calcification beneath the PNI, expected in growing animals with implanted pumping devices, were noted. At autopsy there was no evidence of thrombosis or infection in the regions of the blood pump or the PAD. These findings confirm the calves' benign histologic response to the MAV, and together with the results of hematologic and biochemiccal studies, and bench tests of system components being reported elsewhere, indicate the system's readiness for limited clinical investigation in selected patients with chronic congestive failure.

Challenge to conventional treatment for myocardial failure-mechanical assist.

Use of a prosthesis for temporary or permanent circulatory support in left ventricular failure has been investigated by our group for over 12 years. Experiences with both a U-shaped mechanical auxiliary ventricle (MAV) and the intraaortic balloon pump showed that in-series devices can stabilize the failing circulation. Studies with a MAV based on the balloon pump, the dynamic aortic patch (DAP) indicated that this system too is hemodynamically effective. In addition, data from extensive in vivo studies indicated that when its intravascular surface is made of Electrolour (Dacron velour backed by polyurethane with a negative electrical charge), the frequency of thromboembolism is greatly diminished. Following initial activation of the DAP in a patient with advanced chronic congestive failure, his hemodynamic parameters rapidly approached normal values: mean pulmonary artery and end-diastolic pressures were reduced, cardiac output increased, and myocardial metabolism changed from anaerobic to aerobic. The patient's cardiac function gradually improved, allowing his return to his home. The patient died on the 96th postoperative day after three months of improved cardiac function. Autopsy disclosed the DAP to be functional. A stable fibrin layer had formed on its intravascular surface; there were no signs of embolization. The DAP represents a promising approach to long-term ventricular support. For more than twelve years, our group has been interested in the possibility of using a mechanical prosthesis, not for total heart replacement, but rather for partial temporary or permanent circulatory support. In the first several years of work following this approach, we concentrated on the development of a permanently implantable system for in-series ventricular assistance. This work led to the study of several configurations of a mechanical auxiliary ventricle which gave effective circulatory support in laboratory and clinical studies [1,2]. The problem of achieving satisfactory interaction between blood and prosthesis was not resolved in these studies, but we were sufficiently encouraged by the hemodynamic effects to look into the possibility of working with the temporary support system initially proposed by Moulopoulos, Topaz, and Kolff [3].

U-shaped mechanical auxiliary ventricle.

IN 1966, the implantation of a mechanical auxiliary ventricle in two patients gave evidence that the prosthesis may be feasible as a permanent circulatory-assist device in patients with intractable left ventricular failure.^1,2In this paper modifications of the U-shaped ventricle and results of animal experiments are described. <h3>Materials and Methods</h3> The implantable components of the mechanical ventricle consist of a flexible Dacron-reinforced silicone rubber pumping chamber, an outer casing with an air tube, and myocardial electrodes; the external components include a supply of compressed air, a solenoid valve, and an electronic synchronizing device.³In the experiments reported here, the following modifications of this system were employed: 1. A one-piece housing of resin-coated fiber glass covered with silicone rubber (Fig 1). 2. An improved implantation technique in dogs that facilitates transection of the aortic arch between the two anastomoses. 3. An applanation pressure transducer which can be fitted over

Clinical experience with permanent mechanical circulatory assistance

1. 1. The implantation of a mechanical auxiliary ventricle is described in two patients, with severe refractory congestive heart failure. 2. 2. The prosthetic device assisted the patient's circulation for a period of 12 days of intermittent operation with no detectable damage. 3. 3. There is evidence that clotting in the prosthesis was a result of excessively long arterial graft segments which can be eliminated due to redesign of the device. 4. 4. The mechanical auxiliary ventricle has reached a stage of development where it can be considered practical for an intensive clinical trial in patients with near terminal congestive heart failure. 5. 5. These trials will define the types of patients who can benefit most from this assist device and will allow the development of standardized surgical techniques and long-term operating criteria for the mechanical auxiliary ventricle.

Hemodynamic effects of a mechanical auxiliary ventricle following induced heart failure in dogs

Hemodynamic effects of a mechanical auxiliary ventricle following induced heart failure in dogs

A Clinical Experience With an Implanted Mechanical Auxiliary Ventricle

A mechanical auxiliary ventricle for intermittent permanent assistance was implanted Feb 4, 1966, in a 33year-old man with intractable left ventricular failure due to idiopathic cardiomyopathy. When the ventricle began functioning, systemic pressure was returned to normal as was left auricular pressure. During the immediate postoperative period the patient maintained fair stability with arterial pressure remaining at physiologic levels. The patient's sensorium appeared normal postoperatively. His activity required sedation. No unusual sensations related to the implantation were reported. Despite a good clinical picture, a constantly increasing pulse rate rose to 160 to 180 beats per minute. Eleven hours postoperatively his left auricular and central venous pressure rose sharply while peripheral arterial pressure fell. The patient died 20 hours and 30 minutes following completion of the operation. Cause of death is not fully understood but may be related to prolonged uncontrollable tachycardia.

A clinical experience with an implanted mechanical auxiliary ventricle

A mechanical auxiliary ventricle for intermittent permanent assistance was implanted Feb 4, 1966, in a 33year-old man with intractable left ventricular failure due to idiopathic cardiomyopathy. When the ventricle began functioning, systemic pressure was returned to normal as was left auricular pressure. During the immediate postoperative period the patient maintained fair stability with arterial pressure remaining at physiologic levels. The patient's sensorium appeared normal postoperatively. His activity required sedation. No unusual sensations related to the implantation were reported. Despite a good clinical picture, a constantly increasing pulse rate rose to 160 to 180 beats per minute. Eleven hours postoperatively his left auricular and central venous pressure rose sharply while peripheral arterial pressure fell. The patient died 20 hours and 30 minutes following completion of the operation. Cause of death is not fully understood but may be related to prolonged uncontrollable tachycardia.

Prolonged arterio-arterial pumping in dogs with a mechanical auxiliary ventricle.

Prolonged arterio-arterial pumping in dogs with a mechanical auxiliary ventricle.

Hemodynamic effects of a mechanical auxiliary ventricle following induced heart failure in dogs

Hemodynamic effects of a mechanical auxiliary ventricle following induced heart failure in dogs