Application Of Left Ventricular Assist Devices Research Articles

Left ventricular assist device for end-stage heart failure: results of the first LVAD destination program in the Netherlands : Towards LVAD destination therapy in the Netherlands?

Left ventricular assist device for end-stage heart failure: results of the first LVAD destination program in the Netherlands : Towards LVAD destination therapy in the Netherlands?

Measuring Nonpulsatile Blood Pressure

We are in a unique era of human physiology: the era of nonpulsatility. The benefits of pulsatile blood pressure (BP) have been debated for decades, but now this debate is growing with the emergence of continuous flow left ventricular assist devices (LVAD) as an accepted therapy for patients with refractory heart failure. The question is this: do humans require pulsatile BP for adequate end-organ function in the acute and chronic settings; or to turn the question around: are humans deleteriously affected by nonpulsatile flow? Article see p 1005 The short- and medium-term outcomes associated with continuous flow LVADs are well known and have significantly improved as compared with first generation pulsatile devices.1–3 Current devices are more durable, with smaller rotors, pumps, and drive lines. Indeed, we have seen a steady rise in the adoption and application of LVADs over the last several years (ie, the HeartMate II continuous flow device was approved for bridge to transplant [BTT] in 2008 and destination therapy [DT] in 2010; the HeartWare device was approved for BTT in 2012). Despite lack of pulsatile flow in the arterial system, end-organ function improves as compared with the preimplant state.2 Nevertheless, we have much to learn about these devices, particularly how to optimize pump speed for long-term use (potentially over the course of decades), …

Dynamic expression profiles of MMPs/TIMPs and collagen deposition in mechanically unloaded rat heart: implications for left ventricular assist device support-induced cardiac alterations

Left ventricular assist devices (LVADs) ameliorate heart failure by reducing preload and afterload. However, extracellular matrix (ECM) deposition after application of LVADs is not clearly defined. The purpose of the present study was to investigate ECM remodeling after mechanical unloading in a rat heart transplant model. Sixty male Lewis rats were subjected to abdominal heterotopic heart transplantation, and the transplanted hearts were pressure- and volume-unloaded. The age- and weight- matched male Lewis rats who had undergone open thoracic surgeries were used as the control. Left ventricle ECM accumulation and the expression/activity of matrix metalloproteinases (MMPs) and tissue inhibitor of matrix metalloproteinases (TIMPs) were measured on the third, seventh, and fourteenth days after transplantation/sham surgery. Compared with the control group, myocardial ECM deposition significantly increased on the seventh and fourteenth days after heart transplantation (P < 0.05) and peaked on the 14th day. The gelatinase activity as well as mRNA expression of MMP-2 and MMP-9 significantly increased after transplantation (P < 0.05). Both mRNA and protein levels of TIMP-1 and TIMP-2 significantly increased compared with those of the control group. Mechanical unloading may lead to adverse remodeling of the ECM of the left ventricle. The underlying mechanism may due to the imbalance of the MMP/TIMP system, especially the remarkable upregulation of TIMPs in the pressure and volume unloaded heart.

Percutaneous Transcatheter Closure of the Aortic Valve to Treat Cardiogenic Shock in a Left Ventricular Assist Device Patient With Severe Aortic Insufficiency

In this case report, we present a patient status post left ventricular assist device implantation complicated by de novo aortic insufficiency. At 8 months postimplant, the patient underwent a reoperative aortic valve repair, without complete closure of the valve. Three months after reoperation, the patient developed cardiogenic shock secondary to recurrent, severe aortic insufficiency. Ultimately, the patient underwent percutaneous, transcatheter closure of the aortic valve with an Amplatzer Cribiform device (AGA Medical Corp, Plymouth, MN). Two months post procedure, the patient remains stable with improved symptoms and functional status, and without evidence of further aortic insufficiency or device migration.

Exchange Techniques for Implantable Ventricular Assist Devices

Implantable left ventricular assist devices (LVADs) are being used to support patients for longer periods because of longer transplant waiting times and the application of LVADs for destination therapy. With longer implant times comes LVAD exchange for component failure or serious device-related infection that cannot be treated medically. LVAD exchange should be performed promptly and planned in accordance with the patient's condition, the type of device previously implanted, and the type used for exchange, as well as whether total system or individual component replacement is required. Most patients who experience pump failure after extended support are in good condition. Preoperatively, patients must be stabilized using standard inotropic and vasoactive medications and undergo a complete workup, including echocardiography. Coagulation abnormalities should be corrected preoperatively. Intraoperatively, continuous transesophageal echocardiography and standard hemodynamic monitoring should be utilized. After opening the chest, LVAD support should be minimized to prevent air entry. Detailed descriptions of the following exchange procedures are presented: Jarvik 2000 to Jarvik 2000, HeartMate (VE or XVE) to HeartMate (VE or XVE), HeartMate (VE or XVE) to HeartMate II, and HeartMate II to HeartMate II. Although more reliable systems may offer longer support times, the need for exchange procedures will likely continue to increase.

Invited commentary

Invited commentary

Late-Onset Driveline Infections: The Achilles’ Heel of Prolonged Left Ventricular Assist Device Support

A successful left ventricular assist device (LVAD) long-term support in an outpatient setting demands that device-related complications are reduced to a minimum. We hypothesized that late onset driveline infections have serious implications on the anticipated application of LVAD as permanent therapy. Between 1996 and 2005, 73 patients were implanted with the Novacor (World Heart Corp, Ottawa, Ontario, Canada; n = 35) or the HeartMate (Thoratec Corp, Pleasanton, CA; n = 38) as either bridge to transplantation (n = 44) or destination therapy (n = 29). Our analysis focused on patients with late-onset infection (> or = 30 days) of the driveline exit site with prior clinical healing of all incisions. Late driveline infections developed in 17 patients (23%) at a median of 158 days (intraquartile range [IQR]: 68 to 213 days) after implantation. The median duration of support in this subgroup was 400 days (IQR, 283 to 849 days). Despite an aggressive treatment algorithm, repeat surgical revision was needed in 12 patients, up to six times in 2 individuals. In 6 patients, the infection progressed to pump pocket infections that led to urgent heart transplantation (n = 4) or explantation (n = 2). The individual risk that a driveline infection would develop dramatically increased with the duration of support, reaching 94% at 1 year. Multivariate analysis identified duration of support (p < 0.001) and documented trauma at the driveline exit site (p < 0.001) as independent predictors of infection. Number and duration of readmissions to the hospital significantly increased (p < 0.001), and long-term follow-up for survival (4.4 +/- 2.2 years, 100% complete) showed a trend towards impaired outcome after driveline infection (5-year survival: 41% versus 70%, p = 0.10). Long-term LVAD support in the current series was jeopardized by late-onset driveline infections, which occurred in all patients with support duration longer than 1 year. Once driveline infections developed, they were difficult to control and significantly increased morbidity.

Left ventricular assist device bridge therapy for acute myocardial infarction

Background. Patients with acute myocardial infarction (AMI) complicated by cardiogenic shock have a high mortality rate. Current treatment modalities remain suboptimal for these patients.Methods. From April 1995 to March 1998, 7 patients were identified as having AMI associated with cardiogenic shock. All received intraaortic balloon pump assistance, in addition to maximal inotropic support.Results. The mean preoperative cardiac index was 2.0 ± 0.3 L/min/m2 and pulmonary capillary wedge pressure was 23 ± 6 mm Hg. Three patients received thrombolytic therapy and 4 patients underwent percutaneous transluminal coronary angioplasty without success. Left ventricular assist devices (LVADs) were implanted as bridge therapy to heart transplantation. One patient died from recurrence of a ventricular septal defect during LVAD support. Six patients were transplanted successfully after mean LVAD support of 59 ± 33 days. Five patients are alive and well at a mean follow-up of 898 ± 447 days. One patient died 3 days after transplantation from acute allograft dysfunction.Conclusions. Timely application of LVADs as bridge therapy to heart transplantation in these critically ill patients can be lifesaving, and should be investigated further.

Flow characteristics and required control algorithm of an implantable centrifugal left ventricular assist device.

As the clinical application of LVADs has increased, attempts have been made to develop smaller, less expensive, more durable and efficient implantable devices using rotary blood pumps. Since chronic circulatory support with implantable continuous-flow LVADs will be established in the near future, we need to determine the flow characteristics through an implantable continuous-flow LVAD. This study describes the flow characteristics through an implantable centrifugal blood pump as a left ventricular assist device (LVAD) to obtain a simple non-invasive algorithm to control its assist flow rate adequately. A prototype of the completely seal-less and pivot bearing-supported centrifugal blood pump was implanted into two calves, bypassing from the left ventricle to the descending aorta. Device motor speed, voltage, current, flow rate, and aortic blood pressure were monitored continuously. The flow patterns revealed forward flow in ventricular systole and backward flow in diastole. As the pump speed increased, an end-diastolic notch became evident in the flow profile. Although the flow rate (Q [l/min]) and rotational speed (R [rpm]) had a linear correlation (Q = 0.0042R - 5.159; r = 0.96), this linearity was altered after the end-diastolic notch was evident. The end-diastolic notch is considered to be a sign of the sucking phenomenon of the centrifugal pump. Also, although the consumed current (I [A]) and flow rate had a linear correlation (I = 0.212Q + 0.29; r = 0.97), this linearity also changed after the end-diastolic notch was evident. Based upon the above findings, we propose a simple algorithm to maintain submaximal flow without inducing sucking. To maintain the submaximal flow rate without measuring flow rate, the sucking point is determined by monitoring consumed current according to gradual increases in voltage.

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.

Treatment of Acute Myocardial Infarction with Cardiogenic Shock using Left Ventricular Assist Device

We have treated ten cardiogenic shock patients after acute myocardial infarction (AMI) with a left ventricular assist device (LVAD). These patients were later divided into three groups: the first group with ventricular septal perforation, the second with aorto-coronary bypass grafting (ACBG) before LVAD implantation and the third group without ACBG. LVAD maintained the systemic circulation in each group, and cardiac function recovered enough to remove LVAD in 70% of the total patients. Two of three patients in the first group were discharged from hospital. Two weaned cases in the second group died of multiple organ failure and one was discharged, and hemorrhagic necrosis was seen in the bypassed area of the myocardium. One patient of the third group could not be weaned from LVAD because of respiratory failure though his heart function began to recover. Another case in the third group underwent bypass grafting after removal of LVAD. However ACBG surgery should be done very carefully because a patient in shock is occasionally intolerant to major surgery. In all groups, the major cause of death was multiple organ failure which was probably caused by the prolonged low output condition prior to LVAD application. In the light of this experience, it appears that LVAD should be applied before irreversible damage occurs to major organs, including the heart itself. To ensure the timely application of LVAD, some way must be found to introduce systematic application of LVAD into the normal course of AMI treatment.