1
|
Tamez D, LaRose JA, Shambaugh C, Chorpenning K, Soucy KG, Sobieski MA, Sherwood L, Giridharan GA, Monreal G, Koenig SC, Slaughter MS. Early feasibility testing and engineering development of the transapical approach for the HeartWare MVAD ventricular assist system. ASAIO J 2014; 60:170-7. [PMID: 24399057 PMCID: PMC4120071 DOI: 10.1097/mat.0000000000000038] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Implantation of ventricular assist devices (VADs) for the treatment of end-stage heart failure (HF) falls decidedly short of clinical demand, which exceeds 100,000 HF patients per year. Ventricular assist device implantation often requires major surgical intervention with associated risk of adverse events and long recovery periods. To address these limitations, HeartWare, Inc. has developed a platform of miniature ventricular devices with progressively reduced surgical invasiveness and innovative patient peripherals. One surgical implant concept is a transapical version of the miniaturized left ventricular assist device (MVAD). The HeartWare MVAD Pump is a small, continuous-flow, full-support device that has a displacement volume of 22 ml. A new cannula configuration has been developed for transapical implantation, where the outflow cannula is positioned across the aortic valve. The two primary objectives for this feasibility study were to evaluate anatomic fit and surgical approach and efficacy of the transapical MVAD configuration. Anatomic fit and surgical approach were demonstrated using human cadavers (n = 4). Efficacy was demonstrated in acute (n = 2) and chronic (n = 1) bovine model experiments and assessed by improvements in hemodynamics, biocompatibility, flow dynamics, and histopathology. Potential advantages of the MVAD Pump include flow support in the same direction as the native ventricle, elimination of cardiopulmonary bypass, and minimally invasive implantation.
Collapse
Affiliation(s)
- Daniel Tamez
- From the *HeartWare, Inc., Miami Lakes, Florida; †Division of Thoracic and Cardiovascular Surgery, Cardiovascular Innovation Institute, University of Louisville, Louisville, Kentucky; ‡Department of Bioengineering, University of Louisville, Louisville, Kentucky; and §Research Resources Facilities (RRF), University of Louisville, Louisville, Kentucky
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
2
|
Second harmonic echocardiography and spontaneous contrast during implantation of a left ventricular assist device. ASAIO J 2010; 56:417-21. [PMID: 20613488 DOI: 10.1097/mat.0b013e3181e9261d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Implantable mechanical left ventricular assist devices (LVADs) are used as a bridge or alternative to heart transplantation. Peroperative transesophageal echocardiography is commonly applied during implantation. Significant air embolism may occur as a result of air leakage at connections and anastomoses when LV filling becomes inadequate, and this must be prevented. Early suspicion and detection of air is mandatory to avoid negative circulatory effects. We hypothesized that monitoring of heart chamber size and occurrence of single air bubbles using second harmonic imaging (SHI) echocardiography may prevent risk for significant air embolism. After implantation of the LVAD in 10 calves, invasive hemodynamic monitoring and epicardial SHI were performed while increasing pump speed. Air bubbles in the ascending aorta were monitored and the left heart visualized for off-line dimensional analysis. Detection of air bubbles in the ascending aorta preceded their appearance in the left ventricle. They occurred exclusively but not always after a decrease in left atrial (LA) size. Decrease in LA pressure did not predict bubble detection or reduction in LA size. We conclude that SHI detects spontaneous ultrasound contrast during implantation of a LVAD and that a decrease in LA size is a warning that air embolism is imminent.
Collapse
|
3
|
Wang D, Zwischenberger JB, Zhou X, Loran D, Topaz S, Nix C, Qian KX, Traber DL, Kolff WJ. Development of "plug and play" TransApical to aorta VAD. ASAIO J 2007; 53:171-5. [PMID: 17413557 DOI: 10.1097/01.mat.0000249502.80792.8c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Our TransApical to Aorta pump, a simple and minimally invasive left ventricular (LV) assist device, has a flexible, thin-wall conduit connected by six struts to a motor with ball bearings and a turbine extending into the blood path. Pulsatile flow is inherent in the design as the native heart contraction preloads the turbine. In six healthy sheep, the LV apex was exposed by a fifth intercostal left thoracotomy. The pump was inserted from the cardiac apex through the LV cavity into the ascending aorta. Aortic and LV pressure waveforms, pump flow, motor current, and pressure were directly measured. All six cannula pumps were smoothly advanced on the first attempt. Pump implantation was <15 minutes (13.6 +/- 1.8 minutes). Blood flow was 2.8 l/min to 4.4 l/min against 86 +/- 8.9 mm Hg mean arterial blood pressure at maximum flow. LV systemic pressure decreased significantly from 102.5 +/- 5.55 mm Hg to 58.8 +/- 15.5 mm Hg at the fourth hour of pumping (p = 0.042), and diastolic LV pressure decreased from 8.4 +/- 3.7 to 6.1 +/- 2.3 mm Hg (p > 0.05). The pump operated with a current of 0.4 to 0.7 amps and rotation speed of 28,000 to 33,000 rpm. Plasma free hemoglobin was 4 +/- 1.41 mg/dl (range, 2 to 5 mg/dl) at termination. No thrombosis was observed at necropsy.A left ventricular assist device using the transapical to aorta approach is quick, reliable, minimally invasive, and achieves significant LV unloading with minimal blood trauma.
Collapse
Affiliation(s)
- Dongfang Wang
- Cardiothoracic Surgery, The University of Texas Medical Branch, Galveston, Texas 77555-0258, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
4
|
Maruyama O, Numata Y, Nishida M, Yamane T, Oshima I, Adachi Y, Masuzawa T. Hemolysis caused by surface roughness under shear flow. J Artif Organs 2005; 8:228-36. [PMID: 16362520 DOI: 10.1007/s10047-005-0316-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2005] [Accepted: 09/09/2005] [Indexed: 11/30/2022]
Abstract
In this study, the relationship between the degree of roughness of blood contact surfaces under laminar shear flow conditions and the level of hemolysis resulting from this roughness was investigated using a rotational shear stressor. Unlike previous in vitro experiments that used a pumped circuit, the level of hemolysis was directly evaluated under a constant shear flow. In total, 1.8% of the blood contact area was roughened to an arithmetic mean roughness (Ra) value of between 0.4 and 9.2 microm by machine processing and a shear load was applied for 30 min at a shear flow rate of 3750 s(-1). As a result, the threshold Ra value for the induction of hemolysis was found to be between 0.4 and 0.8 microm. In addition, the results of this experiment suggested that the high shear stress resulting from surface roughness plays a major role in determining the level of hemolysis caused by surface roughness.
Collapse
Affiliation(s)
- Osamu Maruyama
- Artificial Organ and Biomaterial Group, Institute for Human Science and Biomedical Engineering, National Institute of Advanced Industrial Science and Technology (AIST), 1-2-1 Namiki, Tsukuba, Ibaraki 305-8564, Japan.
| | | | | | | | | | | | | |
Collapse
|
5
|
Ankersmit HJ, Wieselthaler G, Moser B, Gerlitz S, Roth G, Boltz-Nitulescu G, Wolner E. Transitory immunologic response after implantation of the DeBakey VAD continuous-axial-flow pump. J Thorac Cardiovasc Surg 2002; 123:557-61. [PMID: 11882831 DOI: 10.1067/mtc.2002.120011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND The development of local and systemic infection is a significant risk factor associated with implantation of a ventricular assist device. The immunologic consequence of continuous-flow rotary blood pumps is not known. METHODS Six male adult patients (mean age 47 plus minus 10.3) with end-stage left heart failure received a DeBakey VAD axial-flow pump for use as a bridge to transplantation. (Four patients underwent transplantation after a mean 115 plus minus 14 days; 2 patients are still waiting for the allograft.) RESULTS We prospectively monitored T-cell populations and apoptosis-specific aberrant T-cell activation via CD95 triggering and annexin V binding to lymphocytes, identifying T cells undergoing early phases of apoptosis, within the first 10 weeks. Moreover, soluble death-inducing receptors soluble CD95 and soluble tumor necrosis factor-R1 were evaluated by enzyme-linked immunosorbent assay. CONCLUSION Patients bridged to transplantation by a nonpulsatile ventricular assist device demonstrated an initial pronounced apoptosis-specific immune alteration by increased annexin V binding to CD3 T cells and death-inducing receptors soluble CD95/tumor necrosis factor-R1 (all P <.001). All parameters normalized after 7 weeks to baseline. No blood-borne sepsis was detected, as defined by blood culture, within the first 10 weeks of the cohort study. These results indicate a biphasic immunologic response in patients with end-stage heart failure treated with nonpulsatile ventricular assist devices.
Collapse
Affiliation(s)
- Hendrik Jan Ankersmit
- Department of Surgery, General Hospital Vienna University, Währinger Gürtel 18-20, 1090 Vienna, Austria.
| | | | | | | | | | | | | |
Collapse
|
6
|
Wieselthaler GM, Schima H, Hiesmayr M, Pacher R, Laufer G, Noon GP, DeBakey M, Wolner E. First clinical experience with the DeBakey VAD continuous-axial-flow pump for bridge to transplantation. Circulation 2000; 101:356-9. [PMID: 10653824 DOI: 10.1161/01.cir.101.4.356] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND A shortage of donor organs and increased numbers of deaths of patients on the waiting list for cardiac transplantation make mechanical circulatory support for a bridge to transplantation a standard clinical procedure. Continuous-flow rotary blood pumps offer exciting new perspectives. METHODS AND RESULTS Two male patients (ages 44 and 65 years) suffering from end-stage left heart failure were implanted with a DeBakey VAD axial-flow pump for use as a bridge to transplant. In the initial postoperative period, the mean pump flow was 3.9+/-0.5 L/min, which equals a mean cardiac index (CI) of 2.3+/-0.2 L. min(-1). m(-2). In both patients, the early postoperative phase was characterized by a completely nonpulsatile flow profile. However, with the recovery of heart function 8 to 12 days after implantation, increasing pulse pressures became evident, and net flow rose to 4.5+/-0.6 L/min, causing an increase of mean CI up to 2.7+/-0.2 L. min(-1). m(-2). Patients were mobilized and put through regular physical training. Hemolysis stayed in the physiological range and increased only slightly from 2. 1+/-0.8 mg/dL before surgery to 3.3+/-1.8 mg/dL 6 weeks after implantation. CONCLUSIONS The first clinical implants of the DeBakey VAD axial-flow pump have demonstrated the device to be a promising measure of bridge-to-transplant mechanical support.
Collapse
Affiliation(s)
- G M Wieselthaler
- Department of Cardiothoracic Surgery, University of Vienna, Austria.
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Tomioka J, Mori T, Yamazaki K, Koyanagi H. Sealing properties of mechanical seals for an axial flow blood pump. Artif Organs 1999; 23:708-11. [PMID: 10463493 DOI: 10.1046/j.1525-1594.1999.06407.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A miniature intraventricular axial flow blood pump for left ventricular support is under development. One of the key technologies required for such pumps is sealing of the motor shaft. In this study, to prevent blood backflow into the motor side, mechanical seals were developed and their sealing properties investigated. In the experimental apparatus, the mechanical seal separated the bovine blood on the chamber side from the cooling water on the motor side. A leakage of the blood was measured by inductively coupled plasma (ICP) light emission analysis. The rate of hemolysis was measured by the cyanmethemoglobin method. Frictional torque acting on the shaft was measured by a torque transducer. In the experiments, the rotational speed of the shaft was changed from 1,000 to 10,000 rpm, and the contact force of the seal faces was changed from 1.96 to 4.31 N. To estimate lubrication regimes, the Stribeck curve, a diagram of the coefficient of friction against the bearing characteristic G number, was drawn. The results of the experiments showed that both the leakage of blood and the rate of hemolysis were very small. The friction loss was also very small. The mechanical seal was operated in various lubrication regimes, from a fluid lubrication regime to a mixed lubrication regime.
Collapse
Affiliation(s)
- J Tomioka
- Department of Mechanical Engineering, Waseda University, Tokyo, Japan
| | | | | | | |
Collapse
|
8
|
Yamazaki K, Litwak P, Tagusari O, Mori T, Kono K, Kameneva M, Watach M, Gordon L, Miyagishima M, Tomioka J, Umezu M, Outa E, Antaki JF, Kormos RL, Koyanagi H, Griffith BP. An implantable centrifugal blood pump with a recirculating purge system (Cool-Seal system). Artif Organs 1998; 22:466-74. [PMID: 9650667 DOI: 10.1046/j.1525-1594.1998.06156.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A compact centrifugal blood pump has been developed as an implantable left ventricular assist system. The impeller diameter is 40 mm, and pump dimensions are 55 x 64 mm. This first prototype, fabricated from titanium alloy, resulted in a pump weight of 400 g including a brushless DC motor. The weight of a second prototype pump was reduced to 280 g. The entire blood contacting surface is coated with diamond like carbon (DLC) to improve blood compatibility. Flow rates of over 7 L/min against 100 mm Hg pressure at 2,500 rpm with 9 W total power consumption have been measured. A newly designed mechanical seal with a recirculating purge system (Cool-Seal) is used for the shaft seal. In this seal system, the seal temperature is kept under 40 degrees C to prevent heat denaturation of blood proteins. Purge fluid also cools the pump motor coil and journal bearing. Purge fluid is continuously purified and sterilized by an ultrafiltration unit which is incorporated in the paracorporeal drive console. In vitro experiments with bovine blood demonstrated an acceptably low hemolysis rate (normalized index of hemolysis = 0.005 +/- 0.002 g/100 L). In vivo experiments are currently ongoing using calves. Via left thoracotomy, left ventricular (LV) apex descending aorta bypass was performed utilizing an expanded polytetrafluoroethylene (ePTFE) vascular graft with the pump placed in the left thoracic cavity. In 2 in vivo experiments, the pump flow rate was maintained at 5-9 L/min, and pump power consumption remained stable at 9-10 W. All plasma free Hb levels were measured at less than 15 mg/dl. The seal system has demonstrated good seal capability with negligible purge fluid consumption (<0.5 ml/day). In both calves, the pumps demonstrated trouble free continuous function over 6 month (200 days and 222 days).
Collapse
|
9
|
Araki K, Anai H, Oshikawa M, Nakamura K, Onitsuka T. In vitro performance of a centrifugal, a mixed flow, and an axial flow blood pump. Artif Organs 1998; 22:366-70. [PMID: 9609342 DOI: 10.1046/j.1525-1594.1998.06142.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We specially devised 3 types of turbo pumps, a centrifugal pump (CFP), a mixed flow pump (MFP), and an axial flow pump (AFP), and analyzed their in vitro performance. The common structural design elements were an impeller diameter of 20 mm and sealless magnet couple driving. In vitro tests were carried out using heparinized fresh bovine blood. The hemolysis was comprehensively evaluated at 7-16 points by changing the flow rate and pressure head (mapping of hemolytic property). The maximum efficiency (motor output to pump output) was 44.9% at 7,000 rpm, 3.17 L/min, 191 mm Hg in the CFP; 66.3% at 7,000 rpm, 6.9 L/min, 136 mm Hg in the MFP; and 20.6% at 9,000 rpm, 5.54 L/min, 74 mm Hg in the AFP, respectively. The minimum normalized index of hemolysis (NIH) (g/100 L) was 0.038 at 5,000 rpm, 4.60 L/min, 38 mm Hg in the CFP; 0.010 at 7,000 rpm, 8.22 L/min, 100 mm Hg in the MFP; and 0.033 at 7,000 rpm, 2.84 L/min, 48 mm Hg in the AFP, respectively. The best efficiency and NIH were achieved in the MFP.
Collapse
Affiliation(s)
- K Araki
- Medical Informatics, Miyazaki Medical College Hospital, Kiyotake, Japan
| | | | | | | | | |
Collapse
|