Centrifugal Left Ventricular Assist Device Research Articles

What is the ideal off-test trial for continuous-flow ventricular-assist-device explantation? Intracircuit back-flow analysis in a mock circulation model

Bridge to recovery has become a major goal after left-ventricular-assist-device (LVAD) implantation thanks to recent development in adjunctive therapies. Precise assessment of native heart function under minimum LVAD support is the key for successful LVAD explantation. However, weaning of centrifugal LVADs normally generates diastolic intracircuit backward flow. This retrograde flow may become excessive load for the native heart during off-pump test. The flow itself is an inevitable characteristic of centrifugal pumps. Therefore, evaluating this retrograde flow in vitro is of considerable significance, even if its amount is different from that in clinical settings. The purpose of this study was to assess diastolic backflow of continuous-flow centrifugal LVADs in a mock circulation model. A centrifugal LVAD (EVAHEART, Sun Medical Technology) was installed in a mock circulation model by the left ventricle uptake and the ascending aortic return. Pump flow was measured at the pump rotational speed of 1000, 1500, 2000, and 2500 rpm, and pulse rate of the virtual native heart was varied to 60, 90, and 120 beats/min. After data collection, pump flow was integrated, and forward and backward intracircuit flow were calculated. As a result, nonphysiological reverse flow of approximately 2.0 L/min exists at the rotational speed, providing 0 L/min mean pump flow. An ideal off-test trial condition should be realizing both ± 0 L/min pump flow and no intracircuit backward flow at the same time. We are developing a novel EVAHEART drive mode that can change its rotational speed in synchronization with cardiac cycle with the aim of controlling this retrograde flow with the new drive mode and creating an ideal off-test condition.

Invasive Assessment of Changes in Continuous Flow Left Ventricular Assist Device Function Due to Exercise and Increased Pump Speed

Background: Pump flows from third-generation centrifugal LVAD (left ventricular assist devices) increase with exercise and faster pump speed. We examined haemodynamic differences of these interventions in patients supported by VentrAssist LVAD.

45: U.S. Experience with a Novel Centrifugal LVAD in Bridge to Transplant (BTT) Patients

LATE BREAKING CLINICAL TRIAL. Completion Date: February 2009. Sponsor: Ventracor, Inc. Summary of Objectives: The VentrAssist™ implantable left ventricular assist device (LVAD) is a third generation centrifugal pump with no mechanical bearings (it uses a hydronamically suspended impeller) designed to enhance reliability and decrease adverse events. This trial evaluates the efficacy and safety of the VentrAssist LVAD in BTT patients. The results of this trial will constitute the first report of a major trial of a centrifugal LVAD in the U.S.

Performance Characterization of a Rotary Centrifugal Left Ventricular Assist Device With Magnetic Suspension

The MiTiHeart (MiTiHeart Corporation, Gaithersburg, MD, USA) left ventricular assist device (LVAD), a third-generation blood pump, is being developed for destination therapy for adult heart failure patients of small to medium frame that are not being served by present pulsatile devices. The pump design is based on a novel, patented, hybrid passive/active magnetic bearing system with backup hydrodynamic thrust bearing and exhibits low power loss, low vibration, and low hemolysis. Performance of the titanium alloy prototype was evaluated in a series of in vitro tests with blood analogue to map out the performance envelop of the pump. The LVAD prototype was implanted in a calf animal model, and the in vivo pump performance was evaluated. The animal's native heart imparted a strong pulsatility to the flow rate. These tests confirmed the efficacy of the MiTiHeart LVAD design and confirmed that the pulsatility does not adversely affect the pump performance.

Initial Results of European Multicenter Clinical Trial with the Duraheart® Mag-lev Centrifugal Left Ventricular Assist Device

Initial Results of European Multicenter Clinical Trial with the Duraheart® Mag-lev Centrifugal Left Ventricular Assist Device

Partial Support with a Centrifugal Left Ventricular Assist Device Reduces Myocardial Oxygen Consumption in Chronic, Ischemic Heart Failure

Background Left ventricular assist devices (LVAD) are increasingly used for heart failure (CHF); however, the level of optimal support has not been elucidated. We hypothesize that partial LVAD support in an ovine model of microinfarction-induced CHF significantly reduces left ventricular myocardial oxygen consumption (LVVO 2). Methods and Results Microembolization of the circumflex coronary artery was used to induce CHF in 5 sheep (ejection fraction 28 ± 2%). Four months later, animals underwent implantation of a centrifugal LVAD. LVAD flow was incrementally increased from 0% (baseline) to 25%, 50%, and 75% support of the LV. LVVO 2 and stroke work (SW) were calculated at each increment. At baseline, LVVO 2 (μL/100 g LV/beat) measured 43.2 ± 3.4. LVVO 2 decreased to 26.5 ± 8.2, ∗ 20.3 ± 8.9, ∗ and 12.6 ± 6.3 ∗ at 25%, 50%, and 75% support ( ∗ P < .05). SW (mm Hg/mL) measured 1933.0 ± 275.7 at baseline and decreased to 1588.0 ± 204.1, 1181.0 ± 157.2, ∗ and 764.5 ± 171.7 ∗ at 25%, 50%, and 75% support. Cardiac output, heart rate, and left main coronary artery blood flow were unaffected with partial support. Conclusion Complete support with a centrifugal LVAD is not necessary for achieving significant reductions in LVVO 2. Partial support of as little as 25% significantly reduces LVVO 2 in CHF through comparatively minor reductions in cardiac work. This is the first study to examine partial LVAD support in a CHF model.

HeartMate III: pump design for a centrifugal LVAD with a magnetically levitated rotor.

A long-term, compact left ventricular assist device (LVAD), the HeartMate III, has been designed and fabricated, featuring a centrifugal pump with a magnetically levitated rotor. The pump has been optimized by in vitro testing to achieve a design point of 7 L/min against 135 mm Hg at high hydrodynamic efficiency (30%) and to be capable of up to 10 L/min under such a load. Furthermore, the pump has demonstrated no mechanical failures, low hemolysis (4-10 mg/dl plasma free Hb), and low thrombogenicity during six (40, 27, 59, 42, 27, and 49-day) in vivo bovine studies.

Long-term left ventricular assist device use before transplantation.

Between September 1992 and April 1995, 19 patients at the authors' institution received pneumatic, pulsatile left ventricular assist devices (LVADs) for bridging to cardiac transplantation. The mean (+/- SD) age of the patients was 51 +/- 14 years (range, 19-64 years). Nine (47%) patients had end-stage idiopathic cardiomyopathy, five (26%) had ischemic cardiomyopathy, and five (26%) other recipients were in cardiogenic shock caused by acute myocardial infarction (AMI). Fifteen (79%) patients were supported with an intraaortic balloon pump or centrifugal LVAD at the time of LVAD insertion (duration, 5.5 +/- 4.1 days). Aprotinin was given to limit bleeding; heparin, followed by warfarin sodium, was used for anticoagulation. A vigorous exercise and nutrition protocol was followed. Cardiac index averaged 2.94 +/- 0.87 L/min/m2 immediately after the implantation procedure. No patient required placement of a right VAD. Average duration of LVAD support was 45 +/- 39 days (range, 3-153 days). Major complications included bleeding requiring reoperation (three patients); cerebrovascular accident (three patients); and severe dysrhythmias requiring direct current cardioversion (four patients). Fourteen (74%) patients underwent transplantation, with one patient still being mechanically supported. All of the patients receiving transplants were discharged from the hospital. Of the individuals who died while supported with the LVAD, 75% were patients with AMI. Timely application of LVADs as part of the interdisciplinary management of end-stage heart disease has generated excellent results for transplant candidates. Right ventricular dysfunction has not necessitated right VAD placement in the authors' experience. Patients with AMI have a higher risk of death while being supported with the device than do more chronically ill recipients.

Mechanical circulatory support with a centrifugal pump after open heart surgery.

Since December 1988, a centrifugal ventricular assist device (VAD) was used to support the circulation in 5 patients who could not be weaned from cardiopulmonary bypass (CPB) or developed cardiogenic shock after removal from CPB. Three patients required a left VAD, one needed a right VAD. One patient had biventricular support using a centrifugal left VAD and a diaphragm type right VAD. The duration of the centrifugal VAD support ranged from 6 to 136 (mean 72)h. All patients were weaned from the VAD, but only 2 patients were discharged from the hospital. Two patients died of multiple organ failure, and one died of cardiogenic shock caused by intractable arrhythmia. Infection occurred in all non-survivors, and 2 of them developed renal failure. We conclude that the centrifugal VAD is effective to recover a failing ventricle. The factors related to the unsuccessful recovery were delayed start of the VAD support and major complications such as infection as infection and renal failure.

Left ventricular function in patients with centrifugal left ventricular assist device.

We used blood pool radionuclide angiography to study the left ventricular (LV) ejection fraction (EF) in 17 patients with a centrifugal assist device (AD) placed because of severe postoperative LV dysfunction. During maximal LVAD flow, the 12 patients who could be weaned had a higher LV-EF than the 5 who could not be weaned (18 +/- 12% vs. 9 +/- 2%, p = 0.04). Sequential studies during variable AD flows in 12 patients revealed an increase in LV-EF from 15 +/- 7% at maximal flows to 33 +/- 8% during minimal flows (p less than 0.005) in the 10 patients who could be weaned and no change in LV-EF in 2 patients who could not be weaned. The LV-EF during maximal LVAD flow rates was similar in the 10 patients with long-term survival (192 +/- 129 days) and in the 7 patients with only short-term (9 +/- 6 days) survival (LV-EF 17 +/- 12% vs. 12 +/- 6%, p = ns). The long-term survivors, however, had a substantial increase in LV-EF from 20 +/- 13% to 34 +/- 9% (p less than 0.01), as the LVAD flow was decreased from maximal to minimal, whereas the short-term survivors had an insignificant increase in LV-EF from 12 +/- 7% to 21 +/- 12% (p = ns). The long-term survivors increased the LV-EF from maximal to minimal LVAD flows by 182%, in contrast with the short-term survivors, who increased the LV-EF by only 44%.(ABSTRACT TRUNCATED AT 250 WORDS)

Left Ventricular Function in Patients with Centrifugal Left Ventricular Assist Device

We used blood pool radionuclide angiography to study the left ventricular (LV) ejection fraction (EF) in 17 patients with a centrifugal assist device (AD) placed because of severe postoperative LV dysfunction. During maximal LVAD flow, the 12 patients who could be weaned had a higher LV-EF than the 5 who could not be weaned (18 +/- 12% vs. 9 +/- 2%, p = 0.04). Sequential studies during variable AD flows in 12 patients revealed an increase in LV-EF from 15 +/- 7% at maximal flows to 33 +/- 8% during minimal flows (p less than 0.005) in the 10 patients who could be weaned and no change in LV-EF in 2 patients who could not be weaned. The LV-EF during maximal LVAD flow rates was similar in the 10 patients with long-term survival (192 +/- 129 days) and in the 7 patients with only short-term (9 +/- 6 days) survival (LV-EF 17 +/- 12% vs. 12 +/- 6%, p = ns). The long-term survivors, however, had a substantial increase in LV-EF from 20 +/- 13% to 34 +/- 9% (p less than 0.01), as the LVAD flow was decreased from maximal to minimal, whereas the short-term survivors had an insignificant increase in LV-EF from 12 +/- 7% to 21 +/- 12% (p = ns). The long-term survivors increased the LV-EF from maximal to minimal LVAD flows by 182%, in contrast with the short-term survivors, who increased the LV-EF by only 44%.(ABSTRACT TRUNCATED AT 250 WORDS)