Development of an Ultracompact Integrated Heart-Lung Assist Device

A novel integrated heart-lung assist device has been developed as a simple to use portable cardiopulmonary support system. The device comprises a centrifugal pump and an artificial lung, which is located around the pump, in an all in one system. The special membrane employed precludes plasma breakthrough in protracted use and enables preprimed setup. Test lungs consisting of the same membrane preserved gas exchange function well after 3 months of preprimed storage. The entire blood contacting surface is treated with covalent heparin bonding to impart good antithrombogenicity. Heparin bonded test lungs could be continuously perfused without systemic anticoagulation as long as 36 days in a venoarterial bypass chronic animal study using goats. The prototype device (diameter, 126 mm; height, 59 mm; membrane area, 0.85 m2; priming volume, 180 ml) demonstrated 9 L/min pump output at a 400 mm Hg pressure head and 180 ml/min oxygen and 110 ml/min carbon dioxide transfer rates at 5 L/min blood flow. We conclude that this device has potential to be the next generation cardiopulmonary support system.     

Dependence of Baroreceptor-Mediated Sympathetic Outflow on Biventricular Assist Device Driving Frequency

Abstract: To investigate the drive condition of the artificial heart from a neurophysiological point of view, the dynamic transduction characteristics of the baroreflex system were analyzed by means of sympathetic neurograms. Two pneumatically actuated ventricular assist devices were implanted as biventricular bypasses (BVBs) in adult mongrel dogs to compare the natural heart circulation and prosthetic circulation. After BVB pumping was initiated, the natural heart was electrically fibrillated. Renal sympathetic nerve activity (RSNA) was recorded to analyze sympathetic outflow. Coherence function between the arterial pressure and RSNA was calculated to evaluate the linearity of the baroreflex system. The largest peak coherency was observed when BVB was driven at the frequency of natural heart beat prior to electrical fibrillation, which suggests that the baroreflex system shows the largest linearity at this frequency. These results suggest the possibility that the natural heart heat frequency is the setting frequency at which the baroreflex system transfers the hemodynamic rhythm to the sympathetic outflow.     

Clinical Application of the Ellipsoid Left Heart Assist Device

The ellipsoid left heart assist device (E-LVAD) was implanted in eight patients suffering from intra-operative heart failure. It was not possible to remove these patients from extracorporeal circulation following an intracardiac procedure; therefore, implantation of the E-LVAD was performed during extracorporeal circulation. The inflow connector was pushed forward from a purse-string suture on the right superior pulmonary vein, across the mitral valve and into the left ventricle. The outflow connector was joined to the ascending aorta. In two patients, the artificial heart chamber was removed after complete recovery of the circulation; these patients, however, later died. In six other patients, untreatable right heart failure developed and these patients died with the pump in place. It is concluded, therefore, that the right heart must also be mechanically supported during postoperative heart failure.     

Optimizing the Response From a Passively Controlled Biventricular Assist Device

Recent studies into rotary biventricular support have indicated that inadequate left/right flow balancing may lead to vascular congestion and/or ventricular suckdown. The implementation of a passive controller that automatically adjusts left/right flow during total and partial cardiac support would improve physiological interaction. This has encouraged the development of a biventricular assist device (BiVAD) prototype that achieves passive control of the two rotary pumps' hydraulic output by way of a nonrotating double pressure plate configuration, the hub, suspended between the ventricular assist device (VAD) impellers. Fluctuations in either the VAD's inlet or outlet pressure will cause the hub to translate, and in doing so, affect each pump's hydraulic outputs. In order to achieve partial support, the floating assembly needed to respond to pathologic blood pressure signals while being insensitive to residual ventricular function. An incorporated mechanical spring–mass–damper assembly affects the passive response to optimize the dynamic interaction between the prototype and the supported cardiovascular system. It was found that increasing the damping from a medium to a high level was effective in filtering out the higher frequency ventricular pressure signals, reducing a modified amplitude ratio by up to 72%. A spring response was also identified as being inherent in the passive response and was characterized as being highly nonlinear at the extremes of the floating assembly's translation range. The results from this study introduce a new means of BiVAD control as well as the characterization of a fully passive mechanical physiological controller.     

Management of Prosthetic Valves during Ventricular Assist Device Implantation

Abstract Background: An increasing number of patients requiring ventricular assist devices (VAD) have had previous valvular corrections, including valve repair and valve replacement with mechanical or bioprosthetic valves. The operative and peri‐operative management of these patients has been varied. Methods: A retrospective study of VADs between January 1994 and June 2008 revealed 10 patients with previous prosthetic valves requiring management during and after VAD placement. Three patients were supported postcardiotomy after valve surgery. Two patients were supported due to cardiogenic shock postoperatively. Four patients were supported as a bridge to transplantation. One patient was supported as a destination therapy (DT). Results: The mitral, valve was left untreated during VAD implantation regardless of valve repair or replacement. For aortic valves, the mechanical aortic valve was replaced with tissue valve in two patients and left untreated in one case. One patient had tricuspid valve repair previously and was left untouched. All patients with prosthetic valves in aortic, mitral and tricuspid position during VAD support received anticoagulation therapy. There were four deaths, and four went on to transplantation. One patient was weaned from VAD and discharged from the hospital. One patient received HeartMate I as DT. The most common causes of death were multisystem organ failure (MSOF) and sepsis. One patient had a thromboembolic event. Conclusions: The survival rate of 60% is encouraging when compared to overall survival rates. The most common cause of death was MSOF. Patients with prosthetic valves may be safely managed during VAD support. (J Card Surg 2010;25:601‐605)     

Successful resection of cecal hepatic metastasis extending into the right side of the heart under cardiopulmonary bypass

Resection is the best hope for the cure of colorectal metastasis to the liver. However, surgery is indicated for only a few patients, especially those who have major vascular involvement. We report a 55-year-old woman with a liver metastasis from the cecum that showed a tumor thrombus in the right side of the heart. She had undergone laparoscopic right hemicolectomy for cecal cancer 6 months before, and presented with a palpable mass in the epigastrium. Abdominal ultrasonography, computed tomography, hepatic angiogram, and echocardiography showed a huge mass on the left lobe of the liver, with a tumor thrombus which extended to the right ventricle through the left hepatic vein and inferior vena cava. Tumor thrombectomy, through a right atriotomy, was success-fully performed under cardiopulmonary bypass, followed by left hepatic lobectomy. The patient's postoperative course was uneventful. Received for publication on Oct. 5, 1998; accepted on Jan. 11, 1999     

Clinical Experience with a New Pulsatile Assist Device (PAD®) During Open-Heart Surgery

Until now, it has not been possible to routinely use counterpulsation during open-heart surgery. A new pulsatile assist device (PAD®) has been developed to convert roller pump flow to pulsatile flow in a simple fashion. In addition, the PAD can be used as an arterial counterpulsator before and after cardiopulmonary bypass (CPB).
The PAD® is inserted in the arterial line close to the aortic root. The device consists of a flexible, valveless balloon through which the arterial blood flows. The balloon is contained within a rigid plastic housing which is connected to a standard intra-aortic balloon pump unit, thereby enabling the blood-filled balloon to be squeezed.
The PAD® was employed in 400 adult patients undergoing open-heart surgery for coronary artery and/or valvular heart disease from 1975 to 1978. Seventy-two percent of these patients were categorized in the New York Heart Association (NYHA) Class III or IV, or had ejection fractions of less than 0.3. The device functioned as a hemodynamically effective counterpulsator before and after CPB. Urinary outputs during CPB were more than doubled on the PAD® when compared to a control group. In addition, during CPB, coronary graft blood flow increased an average of 21.4% with the PAD®. Free plasma hemoglobin levels after CPB were not elevated. Only eight patients (2%) had a perioperative myocardial infarction. Six patients were treated with intra-aortic balloon pumping (IABP) and five survived. Total mortality in this series was eight patients (2%).
It is suggested that the PAD® is a simple and reliable device for both intraoperative counterpulsation and creation of pulsatile CPB. More significantly, use of the PAD® may decrease both the incidence of perioperative myocardial infarction and the need for postoperative IABP.     

Implantation of the Left Ventricular Assist Device

Development of mechanical devices for support of the failing heart is a major goal in cardiac surgery. The application of left ventricular assist device (LVAD) is a promising approach in the case of severe and otherwise untreatable cardiac failure. In our experience we have used two external centrifugal pumps for the extracorporeal biventricular cardiac support in a post-transplantation patient who experienced severe rejection six months after heart transplantation. Our own series includes a total of ten implantations of LVAD's with six patients who could be weaned from the device but only one long-term survivor. The clinical results are not encouraging which suggests that the heart of the patient who needs an LVAD has been damaged beyond any chance for later recovery. Obviously timing is the most crucial aspect of the decision to implant the device. It would appear that orthotopic implantation of the transplanted heart remains the method of definitive treatment.     

Successful treatment of intracardiac progression and metachronous multiple brain metastases from primary lung cancer

We report a rare case of squamous cell carcinoma of the lung extending into the left atrium via the pulmonary vein. The tumor tissue including the thrombus was resected enbloc under cardiopulmonary bypass. Despite adjuvant chemotherapy, multiple brain metastases developed, but they were eradicated by stereotactic radiosurgery. The patient is still diseasefree 48 months after the resection. This case serves to demonstrate the validity of multidisciplinary treatment for locally advanced lung cancer.     

Successful recovery from a massive pulmonary artery tumor embolism occurring during surgery for renal cell carcinoma

We report herein on a case of renal cell carcinoma with retrohepatic inferior vena cava tumor thrombus in which intraoperative cardiac arrest from a massive pulmonary embolism was managed successfully with emergency sternotomy and cardiopulmonary bypass, followed by the removal of the primary site and pulmonary artery embolus.     

Development of the Baylor Gyro Permanently Implantable Centrifugal Blood Pump as a Biventricular Assist Device

The Baylor Gyro permanently implantable centrifugal blood pump (Gyro PI pump) has been under development since 1995 at Baylor College of Medicine. Excellent results were achieved as a left ventricular assist device (LVAD) with survival up to 284 days. Based on these results, we are now focusing on the development of a biventricular assist device (BVAD) system, which requires 2 pumps to be implanted simultaneously in the preperitoneal space. Our hypothesis was that the Gyro PI pump would be an appropriate device for an implantable BVAD system. The Gyro PI 700 pump is fabricated from titanium alloy and has a 25 ml priming volume, pump weight of 204 g, height of 45 mm, and pump diameter of 65 mm. This pump can provide 5 L/min against 100 mm Hg at 2,000 rpm. In this study, 6 half-Dexter healthy calves have been used as the experimental model. The right pump was applied between the infundibular of the right ventricle and the main pulmonary artery. The left pump was applied between the apex of the left ventricle and the thoracic descending aorta. As for anticoagulation, heparin was administered at the first postoperative week and then converted to warfarin sodium from the second week after surgery. Both pump flow rates were controlled maintaining a pulmonary arterial flow of less than 160 ml/kg/min for the sake of avoidance of pulmonary congestion. Blood sampling was done to assess visceral organ function, and the data regarding pump performance were collected. After encountering the endpoint, which the study could not keep for any reasons, necropsy and histopathological examinations were performed. The first 2 cases were terminated within 1 week. Deterioration of the pump flow due to suction phenomenon was recognized in both cases. To avoid the suction phenomenon, a flexible conduit attached on the inlet conduit was designed and implanted. After using the flexible inflow conduit, the required power and the rotational speed were reduced. Furthermore, the suction phenomenon was not observed except for 1 case. There was no deterioration regarding visceral organ function, and pulmonary function was maintained within normal range except for 1 case. Even though the experimental animal survived up to 45 days with the flexible inflow conduit, an increase in power consumption due to thrombus formation behind the impeller became a problem. Lower rotational speed, which was probably produced by the effectiveness of the flexible inflow conduit, was speculated to be one of the reasons. And the minimum range of rotational speed was 1,950 rpm in these 6 BVAD cases and the previous 3 cases of LVAD. In conclusion, 6 cases of BVAD implantation were performed as in vivo animal studies and were observed up to 45 days. The flexible inflow conduit was applied in 4 of 6 cases, and it was effective in avoiding a suction phenomenon. The proper rotational speed of the Gyro PI 700 pump was detected from the viewpoint of antithrombogenicity, which is more than 1,950 rpm.