A Miniaturized Centrifugal Pump for Assist Circulation

Abstract: The newly developed Nikkiso HMS–15 is a miniaturized centrifugal pump. It has an impeller diameter of only 50 mm and a priming volume of only 25 ml. A totally new approach was applied to develop this very small pump. The new pump showed comparable hemolysis with pumps twice as big (e. g., the most widely used coneshaped centrifugal pump [index of hemolysis, 0. 005]). This finding refutes the belief that the pump diameter must be sufficiently large in size. Clinical application for cardiac assist was performed for 48 h without any thrombus formation despite low heparin dosage. Also, the pump showed quite favorable blood trauma when applied as a pump for cardiopulmonary bypass during open heart surgery. The compactness, the high controllability, and the system versatility proved to be very effective for clinical application. This pump is considered very reliable for its highly optimized design.     

Pulsatile Augmentation Device for Extracorporeal Circulation

Abstract: A device has been designed, constructed, and tested to provide pulsatile pressure/flow to a standard extracorporeal bypass circuit. The pulsatile augmentation device is pneumatically driven similar to an artificial heart ventricle except that there are no valves. It is constructed of polyurethane by vacuum forming and high frequency welding. Drivers used are a modified Arrow-Kontron in-traaortic balloon pump or the Utah artificial heart driver. In vitro testing with fresh bovine blood demonstrated acceptable blood compatibility and hemodynamic function. In vivo testing for 4 h in a right and left heart extracorporeal bypass circuit showed good pulse augmentation in pulmonary and systemic bypass circuits. The device shows promise for adding pulse to standard cardiopulmonary bypass and to extracorporeal right heart circulatory assist circuits.     

Hemodynamic evaluation of a new left ventricular assist device: an integrated cardioassist catheter as a pulsatile left ventricle-femoral artery bypass

We developed a new left ventricular (LV) assist catheter (transaortic valve from LV to femoral artery) that is implemented percutaneously and exerted as a synchronous pulsatile partial LV flow support with conventional intraaortic balloon pump (IABP) driving system and centrifugal pump system. We investigated whether this pulsatile LV-aorta bypass is superior to the IABP from a hemodynamic viewpoint. Ten dogs with profound heart failure were placed on this device, and hemodynamic measurements were performed under on-off study of this system. The results revealed a significant increase of mean aortic pressure, total cardiac output, and myocardial blood flow, and a significant reduction of left atrial (LA) pressure and LV afterload estimated by diastolic pressure-time index/tension-time index (DPTI/TTI) measurement compared with baseline values and also with IABP exertion alone. These findings suggest that this system is of clinical value for supporting an impaired LV that is intractable under IABP counterpulsation.     

Clinical Experience of Assisted Circulation with a Centrifugal Pump at Tokyo Women's Medical College

Abstract: In postpericardiotomy patients, the use of pulsatile pumps is limited in a semielective fashion to patients whose postoperative marginal hemodynamics are expected preoperatively. Since 1989, 25 patients have under-gone assisted circulation with a centrifugal pump: 15 (60%) were weaned from the pump, and 7 (28%) survived. In 1988, we heparin-coated the Bio-Pump using the Carmeda technique and developed a totally heparin-coated left heart bypass system together with heparin-coated cannulas and tubing. Four postpericardiotomy patients underwent left heart bypass with this system without heparin for 2 to 9 days. No thrombus was detected in the system. Left heart bypass with a centrifugal pump has been used as a supportive method in surgical repair of thoracic or thoracoabdominal aortic aneurysm. To over-come intraoperative hypothermia and hypoxia, we used a small membrane oxygenator with a heat exchanger in 11 patients, and postoperative recovery dramatically improved. We also developed a preassembled percutaneous cardiopulmonary support (PCPS) system with an automatic priming function using Terumo's straight path centrifugal pump and small membrane oxygenator in cooperation with the Terumo Corporation. This system was used in a patient with cardiogenic shock after acute myocardial infarction. The setup and priming took only 5 min, and 2.5-3.5 L/min of flow was obtained.     

Clinical effectiveness of centrifugal pump to produce pulsatile flow during cardiopulmonary bypass in patients undergoing cardiac surgery

Although the centrifugal pump has been widely used as a nonpulsatile pump for cardiopulmonary bypass (CPB), little is known about its performance as a pulsatile pump for CPB, especially on its efficacy in producing hemodynamic energy and its clinical effectiveness. We performed a study to evaluate whether the Rotaflow centrifugal pump produces effective pulsatile flow during CPB and whether the pulsatile flow in this setting is clinically effective in adult patients undergoing cardiac surgery. Thirty-two patients undergoing CPB for elective coronary artery bypass grafting were randomly allocated to a pulsatile perfusion group (n = 16) or a nonpulsatile perfusion group (n = 16). All patients were perfused with the Rotaflow centrifugal pump. In the pulsatile group, the centrifugal pump was adjusted to the pulsatile mode (60 cycles/min) during aortic cross-clamping, whereas in the nonpulsatile group, the pump was kept in its nonpulsatile mode during the same period of time. Compared with the nonpulsatile group, the pulsatile group had a higher pulse pressure (P < 0.01) and a fraction higher energy equivalent pressure (EEP, P = 0.058). The net gain of pulsatile flow, represented by the surplus hemodynamic energy (SHE), was found much higher in the CPB circuit than in patients (P < 0.01). Clinically, there was no difference between the pulsatile and nonpulsatile groups with regard to postoperative acute kidney injury, endothelial activation, or inflammatory response. Postoperative organ function and the duration of hospital stay were similar in the two patient groups. In conclusion, pulsatile CPB with the Rotaflow centrifugal pump is associated with a small gain of EEP and SHE, which does not seem to be clinically effective in adult cardiac surgical patients.     

A New Blood Pump for Cardiopulmonary Bypass: The HiFlow Centrifugal Pump

Abstract: Centrifugal blood pumps are considered to be generally superior to the traditionally used roller pumps in cardiopulmonary bypass. In our institute a new lightweight centrifugal sealless blood pump with a unique spherical thrust bearing and with a magnetic coupling was developed, the HiFlow. The small design makes the pump suitable for applications in complex devices or close to a patient. Hemolysis tests were carried out in which the BioMedicus pump BP-80 and a roller pump were used as reference. The centrifugal pump HiFlow showed the least blood trauma within the group of investigated pumps. In summary, the HiFlow pump concept with its low priming volume and limited contact surfaces shows great potential for clinical applications in cardiopulmonary bypass. Also, the possibility of using the pump as a short-term assist device with an option of a pulsatile driving mode was demonstrated.     

Clinical Experience with the Sarns Centrifugal Pump

Abstract: Since October 1986, we have had experience with 96 Sarns centrifugal pumps in 72 patients (pts). Heparinless left atrial to femoral artery or aorta bypass was used in 14 pts undergoing surgery on the thoracic aorta with 13 survivors (93%). No paraplegia or device-related complications were observed. In 57 patients, the Sarns centrifugal pump was used as a univentricular (27 pts) or biventricular (30 pts) cardiac assist device for postcardiotomy cardiogenic shock. In these patients, cardiac assist duration ranged from 2 to 434 h with a hospital survival rate of 29% in those requiring left ventricular assist and 13% in those requiring biventricular assist. Although complications were ubiquitous in this mortally ill patient population, in 5,235 pump-hours, no pump thrombosis was observed. Hospital survivors followed for 4 months to 6 years have enjoyed an improved functional class. We conclude that the Sarns centrifugal pump is an effective cardiac assist device when used to salvage patients otherwise unweanable from cardiopulmonary bypass. Partial left ventricular bypass using a centrifugal pump has become our procedure of choice for unloading the left ventricle and for maintenance of distal aortic perfusion pressure when performing surgery on the thoracic aorta. This clinical experience with the Sarns centrifugal pump appears to be similar to that reported with other centrifugal assist devices.     

Left Ventricular Assist for Pediatric Patients With Dilated Cardiomyopathy Using the Medos Vad Cannula and a Centrifugal Pump

Ventricular assist devices for small pediatric patients are expensive and commercially unavailable in Taiwan. We used the Medos ventricular assist device cannula (Medos, Aachen, Germany) and a centrifugal pump to support pediatric patients with dilated cardiomyopathy and decompensated heart failure. From January 2007 to December 2008, three pediatric patients with dilated cardiomyopathy were supported using a centrifugal pump as the left ventricular assist device. The Medos arterial cannula was sutured to the ascending aorta, and the Apex cannula was fixed into the left ventricular apex. When the patient was weaned off of cardiopulmonary bypass, the left ventricular assist device pump was started. The pump flow was gradually titrated according to the filling status of the left ventricle. All the left ventricular assist devices were successfully implanted and functioned well. Two patients on extracorporeal membrane oxygenation had severe lung edema before left ventricular assist device implantation. Both patients required extracorporeal membrane oxygenation for the postoperative period until the pulmonary edema was resolved. Among the three patients, two successfully bridged to heart transplantation after support for 6 and 11 days, respectively. The first patient (10 kg) expired due to systemic emboli 30 days after left ventricular assist device support. In summary, these results suggest that the Medos ventricular assist device cannula and a centrifugal pump is an option for temporary left ventricular assist device support in patients with intractable heart failure and as a bridge to heart transplantation.     

Centrifugal pump as right ventricular assist pump in the treatment of right ventricular failure following resection of left atrial myxoma

A 31-year-old woman had a left atrial myxoma associated with severe pulmonary hypertension and respiratory failure because of incarceration of the tumor to the mitral valve. Emergency surgery was performed, but the patient could not be weaned from cardiopulmonary bypass because of right ventricular failure. A Biomedicus centrifugal pump was used as a right ventricular assist pump. The result was a successful termination of cardiopulmonary bypass. With the support of an intra-aortic balloon pump, the right ventricular assist pump was removed 38 hours after the operation, and the intra-aortic balloon pump was terminated 2 days later. The centrifugal pump is very useful at the majority of centers where the pneumatically activated bi-valved ventricular assist device is unavailable. The Biomedicus centrifugal pump can be easily applied for treatment of perioperative right ventricular failure and is very useful for short-term use without systemic anticoagulants.     

Mechanical support of the failing heart

Intra-aortic balloon pumping (IABP) is presently the supportive treatment of choice for the management of refractory left ventricular power failure.

A dual-chambered intra-aortic balloon mounted on a singlelumen catheter is described, consisting of a distal spherical occluding balloon and a narrow cylindric proximal pumping balloon. This balloon, in contrast to the conventional single-chambered balloon, pumps intra-aortic blood unidirectionally toward the aortic root, thereby effecting a 66–100% greater increment in coronary blood flow. Significant improvement in all measurable indexes of ventricular work have been demonstrated both experimentally and clinically. The dual-chambered intra-aortic balloon effectively interrupts the vicious cycle of cardiogenic shock by increasing coronary blood flow and decreasing ventricular work, thereby improving the balance between oxygen supply and oxygen demand.

System 80, a failsafe mobile cardiac assist console, is discussed in detail as it applies to the total clinical system for dual-chambered IABP. The R wave of the ECG produces balloon deflation in the same diastolic interval, thereby assuring that pump systole can never coincide with ventricular systole. In addition, the system uses the safe soluble gas CO₂ for balloon driving instead of helium, which is insoluble in blood and which can cause lethal sequelae.

Patient management is specially discussed and the results of dual-chambered IABP in 63 patients with an overall survival rate of 63% is detailed.

Intra-aortic balloon pumping/with the dual-chambered intraaortic balloon is the supportive treatment of choice both in medically refractory cardiogenic shock and as an adjunct to the preand postoperative care of selected patients requiring open heart surgery or a myocardial revascularization procedure.

A new valveless pulsatile assist device (PAD) is described that converts roller pump flow into synchronized pulsatile flow. The PAD is actuated by the System 80. The PAD can also be used as an arterial counterpulsator before and after cardiopulmonary bypass. The PAD was employed in 100 adult patients undergoing open heart surgery for coronary artery and/or valvular heart disease. Seventy-three of these patients were New York Heart Association Class 3 or 4 or had ejection fractions of less than 0.3. The device functioned as a hemodynamically effective arterial counterpulsator before and after cardiopulmonary bypass. During bypass pulse pressures of 40–50 mm Hg were readily obtained. Urinary outputs during cardiopulmonary bypass were significantly increased on the PAD when compared to a control group. In addition, during bypass coronary graft blood flow increased an average of 21.4% with the PAD, and after bypass, increased an average of 25.0%. Free plasma hemoglobins after cardiopulmonary bypass were not elevated. Only 1 patient had a perioperative myocardial infarction, and this patient was successfully treated with IABP.

The initial data suggest that the PAD is a simple and reliable device for both intraoperative counterpulsation and for the creation of pulsatile cardiopulmonary bypass. More significantly, use of the PAD may decrease both the incidence of perioperative myocardial infarction and the need for postoperative IABP.     

The use of a biventricular assist device for postcardiotomy profound biventricular failure

A 58-year-old woman who could not be weaned from cardiopulmonary bypass was treated with a biventricular assist device (BVAD) using a centrifugal pump for the left side and a pneumatic pulsatile pump for the right side. At the initiation of the BVAD support, predominant right ventricular failure was recognized and therefore weaning was begun from the left side. The left ventricular assist device was discontinued after 87 h and the patient was finally weaned from the right ventricular assist device after 205 h. Despite the complete recovery of cardiac function, the patient developed renal failure followed by an intractable infection and died of multiple organ failure on the 59th postoperative day (POD).     

Centrifugal blood pumps for various clinical needs

During the past 10 years, different types of blood pumps were developed to address various clinical needs. The Nikkiso centrifugal blood pump was developed for cardiopulmonary bypass application. This blood pump has been widely used in Japan in more than 20% of the cardiopulmonary bypass procedures. The Kyocera C1E3 Gryo pump was developed for short-term circulatory assistance and extracorporeal membrane oxygenation application for up to 2 weeks. This blood pump has been clinically used for up to 28 days without any blood clot formation. Through Phase I of the Japanese government New Energy and Industrial Technology Development Organization (NEDO) program, a chronically implanted centrifugal pump for left ventricular assistance was developed. This pump has already demonstrated its effectiveness, safety, and durability as a 2 year blood pump through in vitro and in vivo experiments. Currently, it is in the process of being converted from an experimental to a clinical device. Through Phase II of the NEDO program, a permanently implantable biventricular assist centrifugal blood pump system is under development. It has demonstrated that the previously mentioned left ventricular assist device blood pump is easily converted into a right ventricular assist pump by simply adding a spacer between the pump and the actuator. This communication discusses the historical development strategies for centrifugal blood pumps and their current status for different clinical needs.     

Preload-responsive, pulsatile-flow, externally valved pump: cardiopulmonary bypass

Currently two pumps are used for cardiopulmonary bypass, the roller pump and the centrifugal or vortex pump. Both are steady-flow pumps. The procedure of cardiopulmonary bypass possesses a finite morbidity and mortality. The degree to which steady flow is responsible for this morbidity and mortality remains to be clarified, but investigators have established the fact that a physiologic degree of pulsatile flow must be achieved before its beneficial results, such as normal systemic resistance and absence of lactate production, can be demonstrated. Availability of a satisfactory pulsatile pump for cardiopulmonary bypass has been a problem in the past but the pump presented here may satisfy this need. It produces physiologic pulsatility with rate dependent ejection time equal to or less than that of humans (413 microseconds minus 1.7 times heart rate), and it is preload-responsive, varying its pumping rate and output with filling pressure. The pump is externally valved to minimize hemolysis, which has been demonstrated in two laboratory studies to be significantly less than with the roller pump. It produces pulsatile flow through membrane oxygenators. The pump is thought to have potential for several clinical applications in addition to (1) pulsatile-flow cardiopulmonary bypass, including (2) left, right, or combined transthoracic QRS synchronized ventricular assist, (3) femoral vein to femoral artery QRS synchronized left ventricular assist, (4) adult or infant ECMO, (5) pulsatile flow hemodialysis. In the latter, spallation and embolization of hemodialysis tubing particles should not be a problem as has proved to be the case with the present hemodialysis pump.     

PreLoad-responsive,Pulsatile-Flow,Externally Valved Pump: Cardiopulmonary Bypass

Currently two pumps are used for cardiopulmonary bypass, the roller pump and the centrifugal or vortex pump. Both are steady-flow pumps. The procedure of cardiopulmonary bypass possesses a finite morbidity and mortality. The degree to which steady flow is responsible for this morbidity and mortality remains to be clarified, but investigators have established the fact that a physiologic degree of pulsatile flow must be achieved before its beneficial results, such as normal systemic resistance and absence of lactate production, can be demonstrated. Availability of a satisfactory pulsatile pump for cardiopulmonary bypass has been a problem in the past but the pump presented here may satisfy this need. It produces physiologic pulsatility with rate dependent ejection time equal to or less than that of humans (413 µs minus 1.7 times heart rate), and it is preload-responsive, varying its pumping rate and output with filling pressure. The pump is externally valved to minimize hemolysis, which has been demonstrated in two laboratory studies to be significantly less than with the roller pump. It produces pulsatile flow through membrane oxygenators. The pump is thought to have potential for several clinical applications in addition to (I) pulsatile-flow cardiopulmonary bypass, including (2) left, right, or combined transthoracic QRS synchronized ventricular assist, (3) femoral vein to femoral artery QRS synchronized left ventricular assist, (4) adult or infant ECMO, (5) pulsatile flow hemodialysis. In the latter, spallation and embolization of hemodialysis tubing particles should not be a problem as has proved to be the case with the present hemodialysis Pump.     

A pulsatile assist device (PAD) for use during cardiopulmonary bypass

A pulsatile assist device (PAD) has been developed to convert roller pump flow to pulsatile flow in a simple fashion. The device can also be used as an arterial counterpulsator before and after cardiopulmonary bypass. The PAD has been used in 125 adult patients undergoing open-heart operations for coronary artery or valvular heart disease or the combination. Ninety-two patients were in New York Heart Association Functional Class III or IV or had ejection fractions of less than 0.3. The PAD functioned as a hemodynamically effective arterial counterpulsator before and after perfusion. All patients were successfully weaned from bypass with the PAD. There has been 1 intraoperative death and 2 late deaths. Only 1 patient had a perioperative myocardial infarction, and this person was successfully treated with intraaortic balloon pumping. We believe the PAD is a simple and reliable device for intraoperative counterpulsation and for the creation of pulsatile cardiopulmonary bypass. More important, use of the PAD may decrease both the incidence of perioperative myocardial infarction and the need for postoperative intraaortic balloon pumping.     

Effects of pulsatile cardiopulmonary bypass on carbohydrate and lipid metabolism

The influence of pulsatile perfusion on carbohydrate and lipid metabolism was examined in 40 patients (20 pulsatile and 20 non-pulsatile) who underwent open-heart surgery. The pulsatile assist device was used for pulsatile cardiopulmonary bypass during aortic cross-clamping only, and samples of the mixed venous blood were taken every 20 minutes. There were no statistically significant differences between pulsatile and non-pulsatile groups with respect to plasma levels of glucose, insulin, glucagon, free fatty acids and ketone bodies. However, an increase in the plasma level of noradrenaline was significantly suppressed in the pulsatile group, and triglyceride levels were significantly higher in the pulsatile than in the non-pulsatile group. These data suggest that pulsatile flow attenuates the catecholamine stress response to cardiopulmonary bypass and has a protective effect on liver function during bypass.     

Experience with the Sarns centrifugal pump in postcardiotomy ventricular failure.

The reported clinical use of the Sarns centrifugal pump (Sarns, Inc./3M, Ann Arbor, Mich.) as a cardiac assist device for postcardiotomy ventricular failure is limited. During a 25-month period ending November 1988, we used 40 Sarns centrifugal pumps as univentricular or biventricular cardiac assist devices in 27 patients who could not be weaned from cardiopulmonary bypass despite maximal pharmacologic and intraaortic balloon support. Eighteen men and nine women with a mean age of 60.4 years (28 to 83) required assistance. Left ventricular assist alone was used in 12 patients, right ventricular assist in 2, and biventricular assist in 13. The duration of assist ranged from 2 to 434 hours (median 45). Centrifugal assist was successful in weaning 100% of the patients. Ten of 27 patients (37%) improved hemodynamically, allowing removal of the device(s), and 5 of 27 (18.5%) survived hospitalization. Survival of patients requiring left ventricular assist only was 33.3% (4/12). Complications were common and included renal failure, hemorrhage, coagulopathy, ventricular arrhythmias, sepsis, cerebrovascular accident, and wound infection. During 3560 centrifugal pump hours, no pump thrombosis was observed. The Sarns centrifugal pump is an effective assist device when used to salvage patients who otherwise cannot be weaned from cardiopulmonary bypass. Statistical analysis of preoperative patient characteristics, operative risk factors, and postoperative complications failed to predict which patients would be weaned from cardiac assist or which would survive.     

The Hemolysis Test of the Gyro C1E3 Pump in Pulsatile Mode

Abstract: While a centrifugal pump is generally used for nonpulsatile blood flow, it can also produce a pulsatile flow by alternating the impeller rotational speed (rpm) periodically. However, there is concern that this centrifugal pump pulsatile mode may induce added hemolysis as a result of the repeated acceleration and deceleration of rpm. Thus, a hemolysis study of the pulsatile modes of the Gyro C1E3 centrifugal pump (Gyro-P) was conducted. The results were then compared with the nonpulsatile mode of the same Gyro pump (Gyro-N) and the nonpulsatile BioMedicus BP-80 (Bio-N) pump. Three different conditions were simulated: left ventricular assist device (LVAD), cardiopulmonary bypass (CPB), and percutaneous cardiopulmonary support (PCPS). The beating rate of the Gyro-P was set at 40 bpm, with repetition of 2 different impeller speeds (the lower rpm being 70% of the higher speed). The 2 impeller speeds were set to obtain the same average flow as that of the nonpulsatile mode. The hemolysis results of the Gyro-P were comparable to or better than those of the Bio-N, and no excessive hemolysis was observed, compared to the Gyro-N. In conclusion, the Gyro-P had an excellent hemolytic characteristic and generated no excessive hemolysis in most clinical usage conditions. With the concern of hemolysis eliminated, this pulsatile mode may have various possible advantages.     

Centrifugal blood pump with a hydraulically-levitated impeller for a permanently implantable biventricular assist device

A permanently implantable biventricular assist device (BVAD) system has been developed with a centrifugal pump which is activated by a hydraulically-levitated impeller. The pump impeller floats hydraulically into the top contact position; this position prevents thrombus formation by creating a washout effect at the bottom bearing area, a common stagnant region. The pump was subjected to in vitro studies using a pulsatile mock circulation loop to confirm the impeller's top contact position and the swinging motion produced by the pulsation. Eleven in vivo BVAD studies confirmed that this swinging motion eliminated blood clot formation. Twenty-one pumps im-planted for up to three months did not reveal any thrombosis in the pumps or downstream organs. One exception was a right pump which was exposed to severe low flow due to the kinking of the outflow graft by the accidental pulling of the flow meter cable. Three ninety-day BVAD studies were achieved without thrombus formation.     

Percutaneous cardiopulmonary support with heparin-coated circuits in postcardiotomy cardiogenic shock. Efficacy and comparison with left heart bypass.

OBJECTIVE: Percutaneous cardiopulmonary support, a simplified form of venoarterial bypass, using totally heparin-coated circuits, has recently come into clinical use. To clarify its efficacy in postcardiotomy cardiogenic shock to aid weaning from cardiopulmonary bypass, we compared results of percutaneous cardiopulmonary support with those of left heart bypass using a centrifugal pump. METHODS: We reviewed 18 patients treated between 1991 and 1998 who could not be weaned from cardiopulmonary bypass. Nine were aided by totally heparin-coated percutaneous cardiopulmonary support (PCPS group), and 9 supported by left heart bypass using a centrifugal pump (LHB group). In both groups, activated clotting time was controlled at 150-200 seconds using minimal doses of heparin as needed. RESULTS: Weaning and survival rates were higher in the PCPS group than in the LHB group (100% vs 55.6%, and 66.7% vs 22.2%). The PCPS group had a smaller amount of blood loss and needed a smaller amount of blood components in the immediate postoperative period. One percutaneous cardiopulmonary support patient required surgical re-exploration for postoperative bleeding (11.1%), but no clinical thromboembolic event occurred in the PCPS group. In the LHB group, 5 patients underwent surgical re-exploration for postoperative bleeding (55.6%), and 2 underwent thrombus extirpation in the left ventricle (22.2%). CONCLUSIONS: Although this study was retrospective and historical backgrounds could have been involved, our data suggest that totally heparin-coated percutaneous cardiopulmonary support system appears more effective as an aid to weaning from cardiopulmonary bypass and in short-term circulatory support for patients in postcardiotomy cardiogenic shock.