气动泵的不同流量对急性左心衰竭辅助作用的实验研究

目的 用血液动力学、心肌超微结构及神经体液指标评价左室辅助装置（ＬＶＡＤ）的有效性。方法 ,对２０条急笥左心衰犬进行高,中、低流量的１８０ｍｉｎ左室辅助,观察其对上述指标的影响。结果 ＬＶＡＤ可使急性左心衰犬各项血流动力学指标迅速趋于稳定,血浆肾素,血管紧张素Ⅱ,内皮素下降,一氧化氮升高,与心力衰竭时差异有显著意义;使心肌细胞水肿和线粒体肿胀减轻。结论 不同辅助流量对急性左心衰时支持均有效,但以中     

An extravascular left ventricular assist device.

The hemodynamic efficacy and prosthesis-vessel interaction of a pneumatically activated circulatory assist device was investigated in 12 acute and 12 chronic studies in dogs. A polyurethane balloon encased in Dacron-velour cloth was fastened to the descending thoracic aorta with a spiral wrapping of Dacron graft material. Diastolic augmentation was provided by rhythmic inflation and deflation of the balloon. Hemodynamic results, based on 5 dogs with experimental myocardial ischemia, showed that left ventricular systolic peak pressure decreased by 8.2 +/- 1.9%, cardiac output increased by 13.1 +/- 2.8%, and circumflex coronary artery flow rose by 17.5 +/- 2.5%. In the chronic experiments the prosthesis was asynchronously but continuously activated from one to sixteen weeks at 74 cycles per minute. Postmortem examination of the implantation site in all 12 dogs showed that necrosis had developed but was limited to the outer half of the medial layer beneath the pumping chamber and that the aortic wall was compressed to about 70% of its original thickness. Although the method described represents a simple form of providing ventricular assistance, its applicability for long-term circulatory support remains to be evaluated.     

Right ventricular failure after left ventricular assist device implantation: the need for an implantable right ventricular assist device

Right ventricular failure after implantation of a left ventricular assist device is an unremitting problem. Consideration of portal circulation is important for reversing liver dysfunction and preventing multiple organ failure after left ventricular assist device implantation. To achieve these objectives, it is imperative to maintain the central venous pressure as low as possible. A more positive application of right ventricular assistance is recommended. Implantable pulsatile left ventricular assist devices cannot be used as a right ventricular assist device because of their structure and device size. To improve future prospects, it is necessary to develop an implantable right ventricular assist device based on a rotary blood pump.     

Postoperative management of patients undergoing left ventricular assist device implantation

Left ventricular assist devices (LVAD) have become an important option for the treatment of patients with advanced heart failure. Unfortunately, patients undergoing LVAD-implantation still experience considerable perioperative morbidity and mortality. Right ventricular failure, bleeding, infections and device-associated problems represent the major postoperative complications. The present overview summarizes current strategies for preoperative risk estimation and for the prevention and treatment of frequently occurring perioperative complications.     

Initial clinical experience with the Haemopump left ventricular assist device

The Haemopump is an intra-arterial, axial flow, temporary left ventricular assist device. The intra-cardiac pump assembly is connected by a flexible drive shaft to a high speed motor and a drive console. The pump is placed in the left ventricle via the femoral artery, iliac artery or abdominal aorta. Blood is withdrawn from the left ventricle and pumped in a continuous, non-pulsatile fashion into the descending thoracic aorta. We report the use of the Haemopump to provide circulatory assistance in 2 patients with severe graft dysfunction following cardiac transplantation. Both patients were successfully weaned from the Haemopump after 6 and 3 days of support. The first patient subsequently died of overwhelming fungal sepsis and the other remains well 3 months after transplantation with normal left ventricular function. The Haemopump is an effective temporary cardiac assist device for application in severe left ventricular failure.     

Right ventricular failure after left ventricular assist device insertion: preoperative risk factors

Right ventricular failure after left ventricular assist device placement is the major concern on weaning from cardiopulmonary bypass and it is one of the most serious complications in the postoperative period. This complication has a poor prognosis and is generally unpredictable. The identification of pre-operative risk factor for this serious complication is incomplete yet. In order to determine pre-operative risk for severe right ventricular failure after left ventricular assist device support we analyzed preoperative hemodynamics, laboratory data and characteristics of 48 patients who received Novacor (World Heart Corp., Ottawa, ON, Canada). We compared the data from the patients who developed right ventricular failure and the patients who did not. Right ventricular failure occurred in 16% of the patients. There was no significant difference between the groups in demographic characteristics. We identified as preoperative risk factors the pre-operative low mean pulmonary artery and the impairment of hepatic and renal function on laboratory data. Our results confirm in part the findings of the few previous studies. This information may be useful for the patient selection for isolated left ventricular assist device implantation, but other studies are necessary before establishing criteria for patient selection for univentricular support universally accepted.     

Heart transplant and left ventricular assist device costs.

BACKGROUND: With the increasing clinical success of left ventricular assist devices (LVADs), physicians need to measure device cost efficacy to determine the societal value of this technology. Today's large clinical volume allows comparison of the costs of this innovation as compared with orthotopic heart transplant (OHT). METHODS: We evaluated hospital cost and reimbursement for patients who were discharged after LVAD implantation and returned to the hospital for OHT. To control for patient-specific variables, LVAD therapy and OHT therapy were compared in the same patient; that is, only those patients who received an LVAD were discharged, and returned for OHT were studied. Length of stay (LOS), re-admissions and outpatient services were analyzed, including their respective total actual hospital cost (TAHC) and net revenue (NR). Time periods analyzed were the same for LVAD and OHT. RESULTS: From the LVAD population at Columbia-Presbyterian Medical Center, 36 patients were discharged following HeartMate vented electric (VE) implantation and re-admitted for OHT between December 1996 and June 2000. Mean pre-LVAD implantation LOS was 21.3 +/- 24.1 days. Post-LVAD LOS was 36.8 +/- 22.2 days vs 18.2 +/- 12.2 days post-OHT (p < 0.001). Mean length of LVAD support was 123.4 +/- 77.7 days. Overall total costs for LVADs exceeded that of OHT, whereas revenue was relatively lower. TAHC post-LVAD averaged $197,957 +/- 77,291, whereas TAHC post-OHT averaged $151,646 +/-53,909 (p = 0.005). NR averaged $144,756 +/- 96,656 post-LVAD vs $178,562 +/- 68,571 post-OHT (p = 0.09). LVAD patients had more re-admissions compared with OHT: 1.2/123 days (+/- 1.7) vs 0.3/123 days (+/- 0.6), respectively (p = 0.005). The average LOS during a re-admission was similar between the 2 groups (LVAD 5.6 days [+/- 10.6] vs OHT 9.6 days [+/- 8.2]; p = 0.18). OHT was associated with a significantly greater number of outpatient services compared with LVAD (9.7 [+/- 6.1] vs 3.0 [+/- 4.7]; p < 0.001). In contrast to OHT, revenues did not match the costs of LVAD therapy. CONCLUSIONS: LVAD implantation is associated with longer LOS and higher cost for initial hospitalization compared with OHT. LVAD patients have higher re-admission rates compared with OHT but similar costs and LOS. OHT is associated with a greater number of outpatient services. Reimbursements for LVAD therapy are relatively low, resulting in significant lost revenue. If LVAD therapy is to become a viable alternative, improvements in both cost-effectiveness and reimbursement will be necessary.     

Fungal left ventricular assist device endocarditis

BACKGROUND: Infection remains as the most serious complication and represents a significant threat to patients during long-term mechanical circulatory support. Fungal infection is a particularly worrisome complication and left ventricular assist device (LVAD) endocarditis does pose a serious threat. METHODS: One hundred and sixty-five patients underwent TCI Heartmate LVAD implantation between July 1991 and December 1999 at our institution. Detailed medical records were kept prospectively for all patients, and a variety of infection-related endpoints were analyzed on patients with fungal LVAD endocarditis. RESULTS: Thirty-seven patients (22%) developed fungal infections during LVAD support. Five (3%) of those met our criteria for the diagnosis of fungal LVAD endocarditis. Microbial portals of entry were identifiable in all cases. Infections were managed successfully in 4 patients (80%). CONCLUSIONS: The successful management of fungal LVAD endocarditis currently requires early recognition of potentially nonspecific signs and symptoms, and timely institution of antifungal therapy. In some cases with device-specific manifestations of LVAD endocarditis, device removal and replacement is necessary. In patients with clinical manifestations of sepsis and fungal driveline site or pocket infections without positive blood culture, urgent transplantation may be the appropriate management. In the setting of shortage in the donor supply, device removal and replacement is necessary.     

Multicenter clinical evaluation of the HeartMate 1000 IP left ventricular assist device.

The Thermo Cardiosystems Inc (Woburn, MA) HeartMate 1000 IP left ventricular assist device (LVAD) has been evaluated as a bridge to transplantation in 34 patients for up to 324 days at seven clinical centers in the United States. Sixty-five percent of the patients underwent transplantation, 80% of whom were discharged from the hospital. Six additional control patients, transplant candidates who met the entrance criteria but who did not receive the device, were also included in the study. Although 3 (50%) of the control patients received transplants, all 6 died within 77 days of having met the LVAD inclusion criteria (100% mortality). Complications resulting from use of the device were comparable with those previously reported for all ventricular assist devices, except for thromboembolic events: bleeding, 39%; infection, 25%; and right heart failure, 21%. No device-related thromboembolic events occurred, although 1 patient experienced an event related to a mechanical aortic valve in the native heart. None of the complications had a significant negative association with outcome of the patient except for right heart failure. All survivors had a significant improvement in hepatic function before transplantation. Total bilirubin values were reduced by 60% during LVAD support. No significant differences were observed when total bilirubin values were compared at 30 and 60 days after LVAD support and at 30 and 60 days after transplantation in a cohort of 15 patients (p greater than 0.05). The improvement in renal function was less predictable than that of hepatic function. Creatinine values decreased significantly before transplantation; however, the values measured at 30 and 60 days after transplantation were higher than those measured at the same intervals after LVAD support had been initiated, and this increase is presumably related to the immunosuppressive drugs. In conclusion, the HeartMate 1000 IP LVAD has been shown to be effective in supporting end-stage cardiomyopathy patients to transplantation. Thromboembolism, previously regarded as a serious complication with such devices, has not been a problem with this device. Additional patients are being enrolled into the study to further document the safety and effectiveness of this technology.     

Successful cardiac transplantation after 4 cases of DeBakey left ventricular assist device failure.

Left ventricular assist devices (LVADs) are an established surgical therapy for patients with end-stage heart failure as a bridge to cardiac transplantation. Major disadvantages of these devices are thromboembolic events, bleeding complications, infections, and malfunctions. We report on our experiences with DeBakey LVAD malfunctions requiring LVAD exchange in 4 patients. All patients underwent subsequent cardiac transplantation and are doing well now.     

Intraperitoneal pocket for left ventricular assist device placement.

BACKGROUND: Implantation of the HeartMate Implanted Pneumatic or Vented Electric Ventricular Assist Device requires that the pump be implanted either in the peritoneal cavity or in the abdominal wall. Both sites have been problematic. METHODS: We describe a new technique in which an intraperitoneal pocket is created, using Gore-Tex Dual Mesh Plus Biomaterial with Holes, to contain the ventricular assist device. This shields the ventricular assist device from the peritoneal contents and avoids abdominal wall dissection. Thirty consecutive patients who underwent implantation using this technique were compared with 16 patients who underwent implantation before this technique was in use. RESULTS: Thirty consecutive patients underwent implantation, and 2 of those patients underwent re-implantation because of device failure (16/30 HeartMate Implanted Pneumatic, 14/30 HeartMate Vented Electric, and 2/14 HeartMate Vented Electric replaced with the HeartMate Implanted Pneumatic). Twenty-five patients have undergone explantation. Pocket infections in patients who have had implanted devices for >1 month decreased from 4 of 13 before the pockets were used to 1 of 25 with the intraperitoneal pockets (Fisher's exact test p = 0.038). Two hernia repairs were required after explantation when the biomaterial pocket was used. A decrease in return to surgery for bleeding was noted after the pocket was used (7/16 without the pocket and 3/32 with the pocket; Fisher's exact test, p = 0.010). CONCLUSIONS: Bleeding complications and pocket infections decreased in this early experience. Further study is necessary to confirm the apparent decrease in complication rate by using this new technique in this small cohort of patients.     

Preoperative risk factors for right ventricular failure after implantable left ventricular assist device insertion

Background. Implantable left ventricular assist device (LVAD) insertion complicated by early right ventricular (RV) failure has a poor prognosis and is generally unpredictable.

Methods. To determine preoperative risk factors for perioperative RV failure after LVAD insertion, patient characteristics and preoperative hemodynamics were analyzed in 100 patients with the HeartMate LVAD (Thermo Cardiosystems, Inc, Woburn, MA) at the Cleveland Clinic.

Results. RV assist device support was required for 11 patients (RVAD group). RVAD use was significantly higher in younger patients, female patients, smaller patients, and myocarditis patients. There was no significant difference in the cardiac index, RV ejection fraction, or right atrial pressure between the two groups preoperatively. The preoperative mean pulmonary arterial pressure (PAP) and RV stroke work index (RV SWI) were significantly lower in the RVAD group (p = 0.015 and p = 0.011, respectively). Survival to transplant was poor in the RVAD group (27%) and was 83% in the no-RVAD group.

Conclusions. The need for perioperative RVAD support was low, only 11%. Preoperative low PAP and low RV SWI were significant risk factors for RVAD use.