Novacor Left Ventricular Assist Device Research Articles

The contribution of microembolic signals (MES) detection in cardioembolic stroke

Summary Background Cardioembolic stroke accounts for about one third of all strokes. Microembolic signals (MES) are frequently found in patients with acute stroke. The role of MES in cardioembolic stroke is less well investigated. Methods Medline based literature review of clinical trials linking MES and stroke with cardiac sources of various risks. Results MES are a rare finding in patients with cardioembolic stroke as well as in sources of potential cardiac embolism (e.g. myocardial infarction, atrial fibrillation, left ventricular thrombus). The low number of patients with MES and the low number of MES during the investigation times leads to a limited statistical power of positive and negative findings. MES in patients with artificial heart valves and the DeBakey left ventricular assist device (LVAD) are predominantly gaseous and do not correlate with stroke risk. In patients with the Novacor LVAD, MES strongly correlate with stroke risk. Conclusion Currently, the role of MES in cardioembolic stroke is only limited due to both, the low prevalence of MES and the number of MES per investigation. Larger studies would be needed to strengthen this role.

Allosensitization in bridge to transplant Novacor left ventricular assist device patients: analysis of long-term outcomes with regard to acute rejection and chronic allograft vasculopathy☆

The true relevance of allosensitization in patients benefiting from left ventricular assist device (LVAD) as bridge to transplant (BTT) is still debated. Available registry data referred to numerous devices precluding LVAD-specific analysis. Therefore, we studied all patients with Novacor LVAD prior to transplantation. From 1985 to 2006, 37 Novacor LVADs were implanted as BTT, with 30 patients surviving to transplantation (81%). Post-LVAD sensitization was determined for anti-HLA-class I and class II IgGs. Study endpoints were overall survival and/or graft loss, > or =3A cellular rejection and chronic allograft vasculopathy (CAV). The results from LVAD patients were compared to non-LVAD primary heart transplant recipients (n=318). After LVAD insertion, 5 out of 27 patients available for analysis developed anti-HLA antibodies (18.5%). The mean anti-HLA titer after Novacor LVAD implantation was 14% [SD 31]. Actuarial 5- and 10-year patient/graft survival for LVAD and non-LVAD transplant recipients were 73% and 55%, and 70% and 55%, respectively (p=NS). Overall prevalence of rejection > or =3A was 23.3 % (LVAD group) and 18.9% (non-LVAD group) (p=NS). At follow-up, the respective incidence of CAV was 8% (LVAD group) and 32.4% (non-LVAD group) (p<0.01). However, mean follow-up was significantly different for LVAD and non-LVAD patients, 46 vs 90 months (p<0.001). In this study, allosensitization occurred infrequently after Novacor LVAD implantation. Secondly, analysis of outcome variables shows that Novacor-LVAD BTT patients can anticipate similar survival to non-LVAD patients, thus minimizing the impact of allosensitization after LVAD implantation.

Chronic Mechanical Circulatory Support for Inotrope-Dependent Heart Failure Patients Who Are Not Transplant Candidates: Results of the INTrEPID Trial

This study evaluated the impact of left ventricular assist device (LVAD) support on survival and quality of life in inotrope-dependent heart failure patients ineligible for cardiac transplantation. The role for LVADs as a bridge to cardiac transplantation has been established, but data supporting their role as permanent therapy in nontransplant candidates are limited. The INTrEPID (Investigation of Nontransplant-Eligible Patients Who Are Inotrope Dependent) trial was a prospective, nonrandomized clinical trial comparing LVAD with optimal medical therapy (OMT). Fifty-five patients with New York Heart Association functional class IV symptoms who failed weaning from inotropic support were offered a Novacor LVAD. Eighteen of these patients did not receive an LVAD owing to patient preference (n = 14) or unavailability of the device (n = 4) but consented to follow-up and constitute a contemporaneous control group. The LVAD and OMT patients were well matched for demographic and disease severity measures, except OMT patients had a lower mean serum sodium (128 mg/dl vs. 134 mg/dl; p = 0.001) and a higher mean blood urea nitrogen concentration (59 vs. 40; p = 0.02). The LVAD-treated patients had superior survival rates at 6 months (46% vs. 22%; p = 0.03) and 12 months (27% vs. 11%; p = 0.02). Adverse event rates were higher in the OMT group. Eighty-five percent of the LVAD-treated patients had minimal or no heart failure symptoms. Five LVAD patients and 1 OMT patient improved sufficiently while on therapy to qualify for cardiac transplantation. Inotrope-dependent heart failure patients who are ineligible for transplantation have a high short-term mortality rate and derive a significant survival advantage from "destination" mechanical circulatory support.

Lack of Sensitization and Equivalent Post-transplant Outcomes With the Novacor Left Ventricular Assist Device

Ventricular assist devices (VADs) are increasingly used to support critically ill heart failure patients awaiting transplantation. Previous work has focused on the Thoratec Heartmate VE device, use of which is associated with pre-formed antibody production. We reviewed our cumulative experience with the Worldheart Novacor VAD as a bridge to transplantation (BTT). From January 1989 through October 2002, 39 patients required a VAD bridge, with 26 of 39 surviving to transplantation. Antibody levels were assessed by complement-dependent cytotoxicity assay at routine intervals and expressed as panel reactive antibody (PRA) levels. Post-transplant allograft rejection, coronary vasculopathy, and survival were compared between Novacor-supported patients and non-VAD transplant recipients. PRA values did not significantly change after VAD implantation (12.4% +/- 11.2% vs 14.8% +/- 12.3%, p = 0.28). Survival for the BTT patients was 80.4%, 75.7%, 64.0%, 64.0%, and 64.0%, respectively, for 1, 3, 5, 7, and 10 years post-transplant, with similar results for non-BTT patients. The freedom from coronary vasculopathy was 90.2%, 90.2%, 72.2%, and 72.2%, respectively, at 1, 3, 5, and 7 years post-transplant. First, to our knowledge, this study is the first to examine the incidence of allosensitization after Novacor implant in detail. In contrast with previous results of work with other VAD systems, as assessed by PRA levels, Novacor patients did not become sensitized. Second, compared with 220 non-BTT patients who received transplants during a similar time frame, Novacor BTT patients had equivalent rejection profiles and survival. Finally, the incidence of transplant-associated coronary artery disease was lower than in previous reports.

Improvement in renal function after left ventricular assist device placement

Background: Worsening renal function is a common consequence of heart failure (HF), and may be improved with circulatory support. The efficacy of left ventricular assist device (LVAD) support to reverse renal insufficiency in end-stage HF has not previously been quantitatively reported, and would be useful to aid in decision-making regarding utilization of LVAD support in the context of bridge-to-transplant (BTT) and destination therapy. Methods: We addressed this question using data derived from 220 patients who underwent Novacor LVAD placement from 1996–03 (190 for BTT and 30 as destination therapy). Creatinine clearance (CrCl), calculated using the Cockroft-Gault formula, was compared among all surviving hospitalized patients who had renal function assessed pre-operative (n=220), at 1 (n=203), 2 (n=178), 3 (n=81), and 4 weeks (n=82) after implant. Paired (same patient, different date) sample t test analyses were then performed for each successive time interval. Similar analyses were performed for patients with baseline CrCl <50 ml/min. Results: Baseline serum creatinine was 1.6±0.7 mg/dl; 60 of patients had CrCl <50 ml/min at implant. Creatinine clearance rose significantly within the first week in the overall study population, from 76.6±46.1 ml/min to 91.8±51.2 ml/min at one week and to 114.9±63.8 ml/min by three weeks. Secondary analysis evaluated patients for whom both pre- and post-implant values were available. This paired sample analysis showed a similar effect (77.0±46.6 pre-implant, rising to 92.1±51.1 ml/min at week 1 (n=202;p<0.01), and from 89.4±49.2 to 95.2±52.4 ml/min (n=171;p=0.01) between weeks 1 and 2. Similar analysis among those with baseline CrCl <50 ml/min showed that the CrCl rose from 36.7±9.2 to 60.1±35.5 (n=55; p<0.01) from pre-implant to week 1 and from 59.7±36.8 to 66.8±47.3 ml/min (n=47; p=0.15) from week 1 to 2. Thirty-seven of the 60 patients with CrCl <50 ml/min (62%) on intra-aortic balloon pump support pre-implant also showed significant improvement in CrCl after LVAD implantation. Overall, 41 of 60 patients (68%) with CrCl <50 improved their creatinine clearance to >50 ml/min during the first 4 weeks after surgery. Conclusion: In patients selected for bridge or destination LVAD support, majority of the patients who demonstrate renal insufficiency that would exclude them from traditional transplant candidacy on the day of LVAD implantation, exhibited substantial improvement in renal function over the first month after device implantation.

Operative strategies to reduce complications in Novacor left ventricular assist device placement.

The original Novacor left ventricular assist device (LVAD) implant procedure has been extensively modified since its introduction. Our goal is to describe, in a concise and comprehensive fashion, the status of this evolution as we currently employ it at our institution. We will also investigate the possible impact of the adoption of this current methodology on the incidence of perioperative hemorrhage at our institution. The number of units of blood transfused on the day of implant surgery and the incidence of reexploration for postoperative hemorrhage were compared between the early group of consecutive patients implanted before adoption of the described implant strategy (n = 10) and the late group of consecutive patients implanted after uniform implementation of this methodology (n = 20). Operative and immediate postoperative hemorrhage, as demonstrated by the number of blood transfusions on the day of implant surgery, was significantly reduced in the group of consecutive patients implanted after adoption of these techniques when compared to the group of patients implanted prior to technical modification. The currently utilized Novacor LVAD implant procedure is described in detail. The amount of blood transfused on the implant day has significantly decreased since the uniform adoption of the current procedure, suggesting that the degree of perioperative hemorrhage has been favorably affected. Although implantation complications can be surgeon, device, institution and patient-specific, the strategies employed in the current implant procedure may be helpful at other heart failure centers.

Recent improvements in outcome with the novacor left ventricular assist device

Background: The Novacor implantable, electrically powered, wearable, left ventricular assist device (LVAD) has been used as a bridge to transplantation at our institution since 1994. Recent changes in protocol have resulted in a decreased incidence of infections, thromboembolism, and mortality. Methods: We reviewed the medical records of all 43 patients who received implantable LVADs at the Mount Sinai Medical Center. After 1998, a number of protocol modifications were instituted. Vascular grafts were changed from a low-porosity, woven polyester (Cooley) to a gelatin-sealed, knitted polyester graft (Vascutek), the devices were implanted pre-peritoneally rather than in the posterior rectus sheath, and extensive drainage of the chest and pre-peritoneal pocket was used. The following anti-coagulation regimen was used: low-molecular-weight Dextran for 1 day, initiated after chest tube drainage <50 cc/hour; then IV heparin for 10 to 14 days, beginning at 500 U/hour, slowly increasing partial thromboplastin time to 1.5 to 2 × control; and finally Coumadin, maintaining the international normalized ratio at 2.5 to 3.5. Daily aspirin, 325 mg, was begun on post-operative Day 7. We compared 22 patients who electively underwent surgery before the changes, Group I, with 18 patients treated thereafter, Group II. Results: Groups I and II were well matched with regard to age (47 vs 44 years); cause of heart failure (idiopathic, 50% vs 44%; ischemic, 50% vs 56%), and duration of support (79 vs 76 days). The incidence of thromboembolic cerebrovascular events was significantly less in Group II (6%) than in Group I (23%), p = 0.025. The incidence of bleeding increased mildly in Group I. Pocket infections occurred in 27% of Group I patients vs 11% of Group II patients, p = 0.018. Only 2 patients (11%) in Group II died while receiving device support, vs 7 (32%) in Group I, p = 0.019. Conclusion: Our results indicate that pre-peritoneal implantation, use of a new generation of vascular grafts, extensive drainage, and a more restricted anti-coagulation regimen improve outcome after Novacor LVAD implantation for advanced heart failure.

Predictors of Severe Right Ventricular Failure After Implantable Left Ventricular Assist Device Insertion: Analysis of 245 Patients

Insertion of an implantable left ventricular assist device (LVAD) complicated by early right ventricular (RV) failure has a poor prognosis and is largely unpredictable. Prediction of RV failure after LVAD placement would lead to more precise patient selection and optimal device selection. We reviewed data from 245 patients (mean age, 54+/-11 years; 85% male) with 189 HeartMate (77%) and 56 Novacor (23%) LVADs. Ischemic cardiomyopathy predominated (65%), and 29% had dilated cardiomyopathy. Overall, RV assist device (RVAD) support was required after LVAD insertion for 23 patients (9%). We compared clinical and hemodynamic parameters before LVAD insertion between RVAD (n=23) and No-RVAD patients (n=222) to determine preoperative risk factors for severe RV failure. By univariate analysis, female gender, small body surface area, nonischemic etiology, preoperative mechanical ventilation, circulatory support before LVAD insertion, low mean and diastolic pulmonary artery pressures (PAPs), low RV stroke work (RVSW), and low RVSW index (RVSWI) were significantly associated with RVAD use. Elevated PAP and pulmonary vascular resistance were not risk factors. Risk factors by multivariable logistic regression were preoperative circulatory support (odds ratio [OR], 5.3), female gender (OR, 4.5), and nonischemic etiology (OR, 3.3). The need for circulatory support, female gender, and nonischemic etiology were the most significant predictors for RVAD use after LVAD insertion. Regarding hemodynamics, low PAP and low RVSWI, reflecting low RV contractility, were important parameters. This information may lead to better patient selection for isolated LVAD implantation.

Implantable left ventricular assist device for patients with postinfarction ventricular septal defect

J Thorac Cardiovasc Surg 2002;124:400-1

Alterations in coagulation after implantation of a pulsatile Novacor LVAD and the axial flow micromed DeBakey LVAD

Background. The MicroMed DeBakey left ventricular assist device (LVAD) is a chamber and valveless axial flow blood pump. We investigated parameters of the coagulation system in patients after implantation of the axial flow LVAD and patients following implantation of a pulsatile Novacor LVAD. Methods. Six consecutive patients of both groups were investigated over a period of 6 weeks after implantation. β-Thromboglobulin, platelet factor 4, factor XIIa, thrombin/antithrombin complexes, plasmin/α 2-antiplasmin complexes, and D-Dimer levels were measured. Results. With the exception of the plasmin/α 2-antiplasmin levels in the Novacor group, all parameters were elevated in both groups. The levels of β-thromboglobulin, platelet factor 4, factor XIIa, and plasmin/α 2-antiplasmin were significantly increased in the axial flow LVAD group. Conclusions. The axial flow LVAD strongly influences the systems of contact activation and fibrinolysis. The elevation of platelet proteins appears to follow platelet damage. Although no thromboembolic events were observed in both groups, elevation of thrombin/antithrombin complexes provides convincing evidence of an increased activation of the coagulation system and the concomitant risk for the development of thromboembolism.

Novacor LVAD bridge to transplantation in peripartum cardiomyopathy

We report the case of a 22-year-old woman suffering from peripartum cardiomyopathy who was successfully bridged to cardiac transplantation with a Novacor left ventricular assist device (LVAD). Her course with the device is presented and emphasis is put on the size mismatch between the patient and the device, a fact with normally precludes the implantation of the Novacor LVAD.

Indications, Function, and Complications of the Left Ventricular Assist Device During Chronic Implantation

This is a review of the use of the left ventricular assist device (LVAD) in patients with refractory heart failure and will emphasize our experience with the pneumatic HeartMate (Thermo Cardiosystems, Inc., Woburn, MA) LVAD. Principles with this device should be similar to other implanted pneumatic and electric LVADs, including the Baxter Novacor (Deerfield, IL) LVAD.

Right Ventricular Support after Implantation of a NOVACOR Left Ventricular Assist Device

The objective was to determine which factors might help to predict the need for mechanical right ventricular support following insertion of a left ventricular assist device (LVAD). A retrospective analysis was performed on 24 patients with cardiomyopathies who had insertion of a LV AD as a bridge to heart transplantation at Presbyterian University Hospital during the period 1987 to 1991. Group 1 consisted of 18 patients who could be adequately supported with the LVAD alone, while Group 2 consisted of 6 patients who required additional support with a right ventricular assist device. Group 2 exhibited longer periods of hypotension on cardiopulmonary bypass, increased inotropic support and decreased right ventricular ejection fraction at time of chest closure postLVAD.

Long-Term Clinical Use of the Novacor Left Ventricular Assist Device as a Bridge to Transplantation

The Novacor left ventricular assist device (NLVAD) is an implantable, electrically powered, pulsatile circulatory assist device undergoing clinical investigation. This report reviews the 33-day bridge-to-transplant course of a patient presenting in cardiogenic shock after acute myocardial infarction who could not be weaned from cardiopulmonary bypass following emergency coronary artery revascularization. Cardiac output was satisfactory during the entire 33-day period: 4.2 ± 0.8 1/min (± SD) during the first week and 6.3 ± 0.9 thereafter. Haptoglobin remained low (30 ± 4 mg%), suggesting mild hemolysis, but plasma hemoglobin remained normal throughout and the patient required only 600 ml of blood after the first two postoperative days. Renal impairment (peak creatinine = 2.9 mg/dl on day three) was attributed to preoperative hypotension and resolved by day seven. The clinical course included pneumonia and hypoxic encephalopathy, both of which resolved. There were no thromboembolic complications or device-related infections. The patient underwent orthotopic cardiac transplantation on day 33. This case demonstrates the long term clinical efficacy and safety of the NLVAD in the setting of cardiogenic shock after massive myocardial infarction as a bridge-to-transplant support system.