Left Ventricular Assist System Research Articles

303: Initial clinical experience with the heartmate II left ventricular assist system

Axial flow left ventricular assist systems (LVAS) offer potential advantages by their simplicity and smaller size. These LVAS have only one moving component, no valves, and no vent or compliance chamber, and are easy to operate. These design characteristics should lead to a high degree of reliability and use in broad patient populations.

Section 10: Surgical Approaches to the Treatment of Heart Failure

Section 10: Surgical Approaches to the Treatment of Heart Failure

Recovery From Hemorrhagic Pulmonary Damage by Combined Use of a Left Ventricular Assist System and Right Ventricular Assist System and Extracorporeal Membrane Oxygenation

A 13-year-old boy developed cardiogenic shock secondary to end-stage dilated cardiomyopathy and extracorporeal life support (ECLS) was initiated. However, pulmonary hemorrhage occurred due to severe pulmonary hypertension. He underwent implantation of a left ventricular assist system (LVAS) and right ventricular assist system (RVAS) plus extracorporeal membrane oxygenation (ECMO) shunting between the right and left atrium. Pulmonary damage was resolved and RVAS-ECMO was terminated after 8 days of support.

Successful bridge to resynchronization therapy with a left ventricular assist system in a patient with idiopathic dilated cardiomyopathy

Implantation of a left ventricular assist system (LVAS) in patients with idiopathic dilated cardiomyopathy (DCM) may improve cardiac function and allow explantation of the device. Generally, an ejection fraction of more than 40% is considered necessary for successful weaning from an LVAS, but less than 10% of DCM patients with an LVAS can achieve such a significant recovery of cardiac function. Cardiac resynchronization therapy, or atrial-synchronized biventricular pacing, has been found to treat congestive heart failure and ventricular dyssynchrony effectively. Here we report on a patient with an LVAS, in whom enough functional recovery could be obtained with resynchronization therapy for the device to be explanted successfully. A 32-year-old man was implanted with a Toyobo-NCVC paracorporeal LVAS to treat his intractable heart failure caused by idiopathic dilated cardiomyopathy. While on the LVAS for 8 months, his cardiac function recovered to some extent. The ejection fraction of his left ventricle (LVEF) improved from 9% to 41%. He chose explantation of the device rather than heart transplantation. Because he occasionally showed a wide QRS pattern on his ECG, epicardial biventricular pacing leads as well as a biventricular pacemaker were implanted on LVAS explantation surgery. An echocardiogram 2 weeks after explantation showed a marked difference in his LVEF by switching his biventricular pacing on and off (40% with biventricular pacing on and 29% with it off). Biventricular pacing may help recovery of cardiac function in selected LVAS patients and contribute to the increase in bridge to recovery cases.

Multiscale Analysis of Surface Thrombosis In Vivo in a Left Ventricular Assist System

Thrombosis limits the success of ventricular assist devices as the demand for alternatives to heart transplants is increasing. This study mapped the occurrence of thrombosis in a left ventricular assist system (LVAS) to better understand the biologic response to these devices. Nine calves divided into two groups were implanted with LVAS for 28 to 30 days. One group was anticoagulated, whereas the second group received no long-term anticoagulation. The blood-contacting poly(urethane urea) surfaces of blood sacs in the LVAS were examined for macroscopic thrombi upon retrieval. The sac was partitioned into eight sections and imaged for thrombi by scanning electron microscopy. No difference in thrombosis was observed macroscopically between the groups. Anticoagulation appeared to result in reduction of platelet-like structures, but the presence of fibrin-like structures remained similar between groups. Regional differences correlating with high and low shear stress regions were observed. At the macroscale, fewer thrombi were recorded in the high shear stress ports. At the microscale, features resembling fibrin were observed primarily in the ports and platelet-like features were common in lower shear stress regions. These variations in thrombosis with anticoagulation and location are likely due to varied fluid dynamics within the LVAS blood sac.

Implantable Left Ventricular Assist Devices

The first bridge to transplant with a left ventricular assist device (LVAD) was preformed over 20 years ago. Since that time, the devices have continued to evolve and now patients are being supported with devices as an alternative to transplantation. The primary indication of end-stage heart failure remains the same but increased knowledge about patient selection, the timing of implant, and patient management have contributed to improved outcomes with decreasing adverse events. Multiorgan failure, right ventricular failure, bleeding, infection, thromboembolism, and device malfunction continue to be the most serious threats to long-term survival in these patients. Despite that, patients who do well are now able to be discharged from the hospital and resume relatively normal lives with the devices. The article reviews 3 of the most widely used LVADs for bridge to transplant therapy: the Thoratec; HeartMate vented electric; and the Novacor Left Ventricular Assist System. Indications, mechanism of operation, clinical problems, and out-of-hospital preparation are outlined.

Left ventricular restoration for ischemic cardiomyopathy and simultaneous implantation of left ventricular assist system actively aiming at bridge to recovery

Left ventricular restoration (LVR) is a useful treatment option for ischemic cardiomyopathy (ICM). However, its current indication is limited for those with relatively stable congestive heart failure symptoms and preserved end-organ function. We report the case of a patient with ICM with cardiogenic shock and end-organ dysfunction who underwent LVR and implantation of a left ventricular assist system (LVAS) as a scheduled operation actively aiming at bridge to recovery.

First Clinical Implant of the VentrAssist Left Ventricular Assist System as Destination Therapy for End-Stage Heart Failure

The VentrAssist device left ventricular assist system, designed for permanent implantation, is a novel centrifugal pump with a hydrodynamically suspended rotor. The first human implant was into a 72-year-old man with New York Heart Association (NYHA) class IV heart failure due to idiopathic dilated cardiomyopathy. The implant and recovery were uneventful, and the patient survives at 17 months, is NYHA class II, and lives at home. This device shows promise in end-stage heart failure for permanent implantation and bridge to transplantation.

Insights from Continued Use of a Novacor Left Ventricular Assist System for a Period of 6 Years

We report a patient supported with the Novacor Left Ventricular Assist System for more than 6 years and chronicle his progress as an illustration of the clinical, practical, and emotional challenges of this therapy and the benefits of an intervention that can return a morbidly ill patient to an essentially normal lifestyle. This experience underlines the importance of patient selection, optimal timing of intervention, and the potential impact of psychologic issues on outcome.

Platelet Activation Markers in Patients With Heart Assist Device

Clinical use of heart assist devices is often associated with thromboembolic complications. We hypothesized that platelets may be activated in patients receiving assist devices and examined expression of the platelet activation markers CD62, CD63, and thrombospondin using flow cytometry in eight patients with Novacor left ventricular assist system (LVAS) or Berlin Heart. Patients with end-stage heart failure had elevated expression of platelet activation markers before insertion of the assist device. While CD62 (P < 0.05) and thrombospondin expression (n.s.) decreased by the 14th postoperative day, the CD63 expression remained elevated (n.s.). A good correlation was found between CD62 and thrombospondin expression (r = 0.72). Bleeding time ex vivo indicated platelet dysfunction during the first 4 weeks after implantation. No relation between expression of platelet activation markers and bleeding time ex vivo were found. In conclusion, expression of the platelet activation markers CD62, CD63, and thrombospondin is increased in patients with end-stage heart failure before device placement and shows prolonged elevation during the assist period. Future studies in larger patient populations are necessary to identify new and specific markers of platelet activation in this clinical setting.

TIME DEPENDENT CHANGES IN SURFACE THROMBOSIS IN LEFT VENTRICULAR ASSIST SYSTEMS

Thrombosis is a dynamic event involving many blood factors over extended periods of time. Although a thrombus may form rapidly, changes continue to occur for days to months. Understanding the dynamics of surface thrombus formation may be important in reducing the incidence of thrombosis in left ventricular assist systems (LVAS). LVAS with poly(urethane urea) blood sacs were implanted in 7 and 9 calves for 3 and 30 days, respectively, and divided in two groups: 1) received warfarin sodium anticoagulation, and 2) received no postoperative anticoagulation after stabilization of the animal. During implant retrieval, the sac was flushed with saline, followed by 1% paraformaldehyde before stopping the pump. Macroscopic thrombi were recorded by location, color, and size. Samples from 8 regions for each sac were imaged by scanning electron microscopy (SEM). The 3-day studies had a higher fraction of sacs with macroscopic thrombi and more macroscopic thrombi on the inlet and outlet. Red thrombi were only seen in 3-day studies. At the microscale, sacs from 3-day studies had spherical structures similar in shape but slightly smaller than platelet-like features seen in 30-day studies. Thrombosis differed with sample location in both studies. Although effects of anticoagulation were undetected at the macroscale, SEM images suggested anticoagulation hindered platelet adhesion at 3 and 30 days. In summary, multiscale analysis of surface thrombosis in vivo in LVAS revealed differences between 3-day and 30-day implants.

Incidence of reoperation to repair/replace the Novacor LVAS

With increasing use of left ventricular assist systems (LVAS) for destination therapy (DT), device reliability and durability become key to successful long-term support. Clinical records from the Novacor LVAS systems were reviewed to quantify device reliability in clinical use.

Comparison of infections in the CardioWest TAH, the Novacor Left Ventricular Assist System and the Thoratec Ventricular Assist Device in 137 patients

Comparison of infections in the CardioWest TAH, the Novacor Left Ventricular Assist System and the Thoratec Ventricular Assist Device in 137 patients

Clinical results with an ePTFE inflow conduit for mechanical circulatory support

Background Neurologic complication is an adverse event associated with mechanical circulatory support. To decrease the incidence of embolic cerebrovascular accidents (CVA) during support with the Novacor left ventricular assist system (LVAS), an expanded polytetrafluoroethylene (ePTFE) inflow conduit has been developed and introduced clinically. Methods Using clinical data from Europe and Canada, we conducted a retrospective analysis of the incidence of embolic CVA with the ePTFE inflow conduit ( n = 88) in comparison with the previously used polyester inflow conduits ( n = 310, including Vascutek® n = 155 and Cooley® n = 155). We calculated freedom from embolic CVA, risk reduction for embolic CVA, and linearized rates of embolic CVA. Results A significant decrease in the incidence of embolic CVA was demonstrated with the ePTFE conduit (ePTFE 10% vs polyester 23%, p = 0.002). Kaplan-Meier analysis of freedom from embolic CVA at 180 days after implantation was 86% for the ePTFE group vs 72% for the polyester group (log-rank test, 0.0185). We also found an associated risk reduction of 55% in CVA occurrence in the ePTFE group when compared with the Polyester group (hazard ratio, 0.445; 95% confidence limit, 0.222–0.890; p = 0.0221). Linearized CVA rates also were decreased at all time intervals after implantation in the ePTFE group. Conclusions Preliminary clinical results with the newly introduced ePTFE inflow conduit provide compelling evidence that the ePTFE conduit material significantly decreases thromboembolic complications during mechanical circulatory support with the Novacor LVAS.

IMPROVED RESULTS WITH THE NOVACOR LVAS USING NEW EPTFE INFLOW CONDUITS AND INTENSIFIED ANTICOAGULATION MANAGEMENT

P646 Aims: The inflow conduit (IFC) of the Novacor left ventricular assist system (LVAS) has been implicated in embolic complications. We report on our single-centre experience with recently introduced ePTFE IFCs and intensified anticoagulation regimen on outcome following Novacor LVAS implantation. Methods: 33 patients implanted with the Novacor LVAS between July 1994 and February 2004 were studied and divided into two groups: group I (n=23, before 2000) received a low-porosity, woven polyester IFC or a gelatin-sealed, knitted polyester IFC. Group II (n=10, since 2000) received an ePTFE IFC. Patients in Group I were anticoagulated with phenprocoumone and acetylic acid or clopidrogel. Patients in Group II additionally received tirofiban perioperatively and after discharge INR self-monitoring was established. Results: Mean age was 43±2.5 years in Group I and 49±3.7 years in Group II, with mean LVAS support duration of 167±36 and 67±18 days respectively. The incidence of neurologic dysfunction was 8/23 (34.8%) in Group I versus 0/10 in Group II (p=0.035). Embolic cerebrovascular accidents occurred in 2/23 (8.7%) and 0/10 patients respectively (p=0.479). Cerebral hemorrhage occurred in 1/23 (4.3%) and 0/10 patients. Survival on LVAS in Group I was 65.2% and 70% in Group II. Conclusions: The combination of ePTFE IFCs and intensified anticoagulation management provided a significant reduction in neurological dysfunction without increased incidence of bleeding in our limited experience. Continuous improvements in safety performance of the Novacor LVAS increases its suitability for destination therapy.

Long-term Circulatory Support – The Left Ventricular Assist System for Advanced Heart Failure

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COMPLIANCE CHAMBER PERFORMANCE IN THE FIRST CLINICAL APPLICATION OF THE Arrow LionHeart??? LVAS

The Arrow LionHeart™ Left Ventricular Assist System (LVAS) is a completely implanted system that employs a compliance chamber implanted in the pleural space. The chamber compensates for displaced blood stroke volume and atmospheric pressure changes. The segmented polyurethane chamber is discoid-shaped (5 in. dia., 0.5 in. thick). The system has been implanted in 29 patients in Europe and 10 patients in the U.S. The longest surviving patient is alive more than 1100 days post implantation. All Lhambers performed satisfactorily, allowing normal pump output over a wide range of conditions. Fourteen compliance measurements were collected from 10 patients. The working range was found to be −50 to + 14 cc (84 cc volume change) over a pressure of −20 to + 5 mmHg 125 mmHg range). Six compliance measurements were made within the first 2 postop months, and eight were made between 7 months and 2 years. Overall compliance was 3.39 cc/mmHg (95% CI: 2.7, 4.06). Repeated assessments showed no significant changes in compliance over time. Refill intervals were typically monthly, but ranged from 2- 6 weeks. The gas loss rate was estimated to be 2–3 day with the system filled with room air. Gas loss rates measured during pre-clinical animal testing were not significantly different, averaging 2 cc/day (95% CI: 1.2, 2.8). The compliance chamber allows for an intact-skin system that may contribute to improved quality of life for long term LVAS patients.

Is center specific implantation volume a predictor of clinical outcomes with mechanical circulatory support?

This study examined the relationship between implant center volumes and survival rate for implantation of mechanical circulatory support (MCS) devices. Using the Novacor left ventricular assist system (LVAS) Registry, the study cohort consisted of 1,348 patients with established outcomes from 97 centers stratified by the implant center volume: 1-10 implants (n = 199, 65 centers), 11-25 implants (n = 189, 12 centers), 26-50 implants (n = 445, 13 centers), and more than 51 implants (n = 515, 7 centers). Regression and correlation analyses were performed. Regression analysis found a negative impact on survival for centers performing 1-10 implants, with an odds ratio of 1.73 (95% confidence interval, 1.28-2.34; p < 0.001). Composite results from the first 10 implants of each larger volume center were then compared with the group with 1-10 implants, demonstrating that centers with larger volumes had superior results, even in the early patient experience (61% versus 46% transplanted/weaned, p < 0.001). However, when annualized outcomes (i.e., outcomes by calendar year) were determined for each center, no significant correlation was found between the outcomes and annualized frequency of implantation (R2 = 0.003, n = 422). Although the total number of implants performed at a specific center appeared to impact clinical outcomes, no correlation was found between annualized frequency of implant and clinical outcome.

Distal thoracic aorta hemodynamics during exercise with continuous flow left ventricular assist system.

Continuous flow left ventricular assist systems (LVAS) are being discussed as a destination therapy. LVAS patients will have expanded activity of daily life, including exercise. In this study, we analyzed the effects of exercise on blood flow in the distal thoracic aorta of LVAD implanted animals. Five calves with a continuous flow LVAS exercised on treadmill at two different pump flow rates (PFR), 60-80% (high PFR) and 25-30% (low PFR) of pulmonary artery flow rate. Pump, pulmonary artery and descending thoracic aorta flow waves were recorded before, during and after exercise. Systolic and diastolic flow volume in each cardiac cycle in pump and descending thoracic aorta flow was calculated. (1) Average flow rates - Pulmonary artery and descending thoracic aorta flow rates increased with heart rate during exercise and there was no difference between groups. (2) Pump flow wave - Pump regurgitation increased temporally during exercise at both PFRs, but sustained incidences of regurgitation after exercise were only observed at low PFR. Systolic and diastolic pump flow volume decreased during exercise at both PFRs, but systolic volume increased and diastolic volume decreased significantly after exercise at low PFR. (3) Descending thoracic aorta flow wave - At high PFR, systolic volume of descending thoracic aorta increased but diastolic flow volume decreased during exercise. At low PFR, both systolic and diastolic volume of the descending thoracic aorta decreased during exercise, but systolic volume increased and diastolic volume decreased after exercise. Systolic volume of the descending thoracic aorta in low PFR was significantly greater and diastolic volume was less than those in high PFR during and after exercise. Exercise temporarily increases pump regurgitation with continuous flow LVAS support. Average flow rate of the descending thoracic aorta was maintained by compensation from increased heart rate, although the diastolic flow of the descending thoracic aorta decreased after exercise at the lower pump flow rate. Further study will be needed to evaluate whether or not this flow decrease causes hemodynamic and/or an oxygen delivery mismatch to peripheral tissue.

Function, eligibility, outcomes, and exercise capacity associated with left ventricular assist devices: exercise rehabilitation and training for patients with ventricular assist devices.

and Drug Administration in the United States, the most widely used of which are systems from Thoratec (formerly Thermo Cardiosystems) (Pleasanton, Calif) and Worldheart’s Novacor (formerly Novacor) (Ottawa, Ontario, Canada). Left ventricular assist devices have been designed with a variety of drive systems, including pneumatic and electric systems. The pneumatic devices significantly limit the patients’ daily function as a result of the sizable mobile external control unit (73 pounds for the Heartmate LVAD).9 The electric devices have two external batteries that can be worn in a shoulder holster or on a belt, allowing for 4 to 6 hours of tether-free support.10 Of the available pneumatic mechanical cardiac assist systems, two are extracorporeal devices (ABIOMED BVS 5000, Danvers, Mass; and Thoratec VAD, Pleasanton, Calif). Both of these units have been used in clinical situations wherein body surface area was less than1.5 m2.11 They seem to be preferred for patients who have been on cardiopulmonary bypass support, and those who require biventricular support.11 Currently, the electric intracorporeal LVAD devices produced by Worldheart (Novacor Left Ventricular Assist System [LVAS]) and Thoratec (Heartmate VE) are the preferred device for function of the LVAD, quality of life, and success in bridging to transplantation or recovery. Moreover, the implantable LVAD may reduce the need in specific cases for heart transplantation, with early intervention and rehabilitation in select cases.12 The current directions of mechanical assistance include development of new total artificial hearts,13 extracardiac assist devices,14 and the new generation of assist R E V I E W A R T I C L E