Are Ventricular Assist Devices Underutilized?

Abstract A dramatic shift in the durability and reliability of ventricular assist device (VAD) therapy is taking hold due to the newer generations of continuous flow VADs that are either in clinical trials or under consideration by the Food and Drug Administration (FDA) for commercial approval. To expand the pool of potential mechanical circulatory support (MCS) patients, device reliability will need to prove to be greatly enhanced over previous generations of VADs and functional capacity and quality of life will need to improve substantially over baseline. Improved patient selection should have the simultaneously beneficial effects of improving outcomes while expanding the MCS patient population. The critical factors determining the likelihood of expansion of the MCS field include, but are not limited to, improvements in technology and its reliability, training and education of all advanced heart failure caregivers, improving availability of MCS geographically, and a shift in patient selection to a population more likely to benefit from MCS therapy . (J Card Surg 2010;25:421‐424)     

Clinical Application of Left Ventricular Assist Devices

In Japan, 32 patients have had application of monoventricular and biventricular assist devices during the past three years. Five of the 32 patients treated by the Fall of 1986 have successfully achieved long-term survival. In this paper we describe our experience with the Tomasu and Pierce VAD in a total of four and two patients, respectively. Four of the six patients could be successfully weaned from the VAD and two of them were long-term survivors. Nonsynchronizing pumping of the VADs was effective, as well as synchronizing pumping. Anticoagulant therapy is highly recommended during the use of the VAD although there was no significant incidence of thromboembolism or thrombus in the devices in this clinical series.     

Percutaneous Deactivation of Left Ventricular Assist Devices

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Optimal Control Algorithm for Pneumatic Ventricular Assist Devices: Its Application to Automatic Control and Monitoring of Ventricular Assist Devices

Abstract We developed a control and monitoring unit for pneumatic ventricular assist devices (VADs), which provides optimal fill and empty control and real-time evaluation of pump performance. The flow signal of the inflow cannula is integrated every beat to yield pump filling volume per pump diastole. The ejection signal is triggered when pump filling reaches a preset level. The instantaneous mean flow of each beat (stroke volume/cycle length) is compared with the previous beat, and the threshold level is readjusted to optimize flow. This feedback loop is repeated every beat, and pump filling is immediately adjusted to yield maximum pump flow. Simultaneously the mean flow of every 10 beats is compared with that of the previous 10 beats; then, the ejection time is readjusted to optimize flow. Initial clinical application of this unit supports its effectiveness and reliability.     

Pediatric Heart Transplantation Bridged With Ventricular Assist Devices

Heart transplantation (HTx) is indicated in children with end-stage heart failure or complex inoperable congenital defects. Because of the shortage of pediatric donor hearts, various bridge techniques have been used in pediatric patients to prolong patient survival until a suitable heart becomes available. We reviewed medical records of several pediatric patients in whom bridging with ventricular assist devices was used. All of the patients survived HTx, and are alive and well with no neurologic sequelae. They are NYHA functional class I. Thus, morbidity and mortality were acceptable in this high-risk group of pediatric patients with a ventricular assist device bridging to HTx.     

Detection of Premature Ventricular Contractions on a Ventricular Electrocardiogram for Patients With Left Ventricular Assist Devices

The ventricular electrocardiogram (v‐ECG) was developed for long‐term monitoring of heartbeats in patients with a left ventricular assist device (LVAD) and does not normally have the functionality necessary to detect additional heart irregularities that can progress to critical arrhythmias. Although the v‐ECG has the benefits of physiological optimization and counterpulsation control, when abnormal heartbeats occur, the v‐ECG does not show the distinct abnormal waveform that enables easy detection of an abnormal heartbeat among normal heartbeats on the conventional ECG. In this study, the v‐ECGs of normal and abnormal heartbeats are compared with each other with respect to peak‐to‐peak voltage, area, and maximal slopes, and a new method to detect abnormal heartbeats is suggested. In a series of animal experiments with three porcine models (Yorkshire pigs weighing 30–40 kg), a v‐ECG and conventional ECG were taken simultaneously during LVAD perfusion. Clinical experts found 104 abnormal heartbeats from the saved conventional ECG data and confirmed that the other 3159 heartbeats were normal. Almost all of the abnormal heartbeats were premature ventricular contractions (PVCs), and there was short‐term tachycardia for 3 s. A personal computer was used to automatically detect abnormal heartbeats with the v‐ECG according to the new method, and its results were compared with the clinicians' results. The new method found abnormal heartbeats with 90% accuracy, and less than 15% of the total PVCs were missed.     

左心室及双心室辅助装置对缺血心肌的影响

目的 比较左心室辅助装置（LVAD）和双心室辅助装置（BVAD）对缺血心肌再灌注后心脏血流动力学、心肌能量代谢物质和心肌超微结构中线粒体形态的影响。方法 将16只绵羊随机分为LVAD组和BVAD组,每组8只,常温阻断升主动脉25分钟,造成双心室缺血损伤的动物模型。结扎右颈内动脉远端,在心脏复跳后应用转子泵分别行LVAD（左心室－右颈内动脉径路）和BVAD（左心室－右颈内动脉和右心室－肺动脉径路）辅助循环120分钟,测定血流动力学,心肌三磷酸腺苷、磷酸肌酸、观察心肌超微结构变化。结果 施行BVAD或LVAD辅助循环的同时增加容量负荷能够显著改善心脏血流动力学,但LVAD组右心房压显著高于BVAD组（P＜0．05）;BVAD组右心室心肌三磷酸腺苷、磷酸肌酸含量和心肌线粒体比表面值均高于LVAD组（P＜0．05）。结论 BVAD与LVAD更有助于促进双心室缺血损伤心肌的功能恢复。     

Left Ventricular Assist Devices as Alternative to Heart Transplant

The ability of echocardiography to diagnose sources of embolism and the role of the examination in the prediction of thromboembolism are reviewed. In addition, the yield of transthoracic (TTE) and transoesophageal echocardiography (TEE) is analysed in patients with suspected embolism and guidelines are proposed for performing echocardiography in this setting. In general, echocardiography is reliable for diagnosing sources of embolism and this applies in particular to TEE in the case of atrial, valvular, and aortic abnormalities. However, the method is useful for predicting embolism in a few cases only. There is a substantial risk in the event of mobile or protruding thrombi, but screening for these and other markers of thromboembolism seems to be unproductive in most groups of risk patients. Yet, in the presence of atrial fibrillation, echocardiography may be helpful in defining patients with an otherwise normal heart and low risk of embolism - and in defining the relatively rare patient with a clinically low-risk profile but moderate-to-severe left ventricular systolic dysfunction and a high risk of embolism. TEE-guided conversion of atrial fibrillation without weeks of preceding anticoagulation may prove useful, after further investigation. The risk of embolism in relation to the size and mobility of valvular vegetations has remained controversial. In patients with suspected recent embolism, TTE results in less than 5% new therapeutic consequences. In those with a normal TTE, the yield of TEE seems to be equally low. We therefore recommend a selective strategy: TTE and TEE can be omitted when a cardiac source of embolism appears from the clinical setting and in most patients with an obvious predisposition to cerebrovascular disease. However, in the latter cases TTE should be performed if indicated by the clinical situation, e.g. in the presence of fever and murmur. TTE is also recommended when there are no obvious markers of primary vascular disease. To preclude very rare sources of embolism (e.g. atrial thrombi despite sinus rhythm), supplementary TEE is recommended in younger patients in whom primary vascular disease is very unlikely. The diagnosis by TEE of common conditions such as atrial septal aneurysms and patent foramen ovale cannot, however, be taken as proof of the mechanism of a systemic arterial occlusive event; thus it is difficult to change therapy on the basis of such diagnoses.     

A Physiological Controller for Turbodynamic Ventricular Assist Devices Based on Left Ventricular Systolic Pressure

The current article presents a novel physiological feedback controller for turbodynamic ventricular assist devices (tVADs). This controller is based on the recording of the left ventricular (LV) pressure measured at the inlet cannula of a tVAD thus requiring only one pressure sensor. The LV systolic pressure (SP) is proposed as an indicator to determine the varying perfusion requirements. The algorithm to extract the SP from the pump inlet pressure signal used for the controller to adjust the speed of the tVAD shows robust behavior. Its performance was evaluated on a hybrid mock circulation. The experiments with changing perfusion requirements were compared with a physiological circulation and a pathological one assisted with a tVAD operated at constant speed. A sensitivity analysis of the controller parameters was conducted to identify their limits and their influence on a circulation. The performance of the proposed SP controller was evaluated for various values of LV contractility, as well as for a simulated pressure sensor drift. The response of a pathological circulation assisted by a tVAD controlled by the introduced SP controller matched the physiological circulation well, while over‐ and underpumping events were eliminated. The controller presented a robust performance during experiments with simulated pressure sensor drift.     

Preconditioning With Levosimendan Before Implantation of Left Ventricular Assist Devices

In this retrospective study, we investigated the impact of preconditioning of the right ventricle with the calcium sensitizer levosimendan immediately before left ventricular assist device (LVAD) implantation on outcome and survival. Nine consecutive LVAD patients (seven suffering from dilative cardiomyopathy and two from ischemic cardiomyopathy) with echocardiographic and invasive evidence of right heart insufficiency received levosimendan with 0.1 μg/kg body weight/min for 24 h before implantation of the assist device (seven HeartWare and two Jarvik 2000). Administration of levosimendan was safe and had not to be discontinued in any patient. We observed no relevant side effects. Twelve‐month survival after implantation of the LVAD was 89% representing a superior outcome compared with the fifth INTERMACS registry data with 75% survival. Two temporary extracorporeal membrane‐oxygenation implantations were necessary due to intraoperative right ventricular dysfunction. Only one patient died 5 weeks after LVAD implantation of multiorgan failure, five patients were successfully transplanted, and three patients underwent LVAD implantation for destination therapy. Levosimendan might improve clinical outcome and survival when used as pretreatment in patients with right heart insufficiency prior to LVAD implantation. However, we recommend a larger controlled trial in the future to confirm our preliminary results.     

Sexual Concerns of Patients With Implantable Left Ventricular Assist Devices

The growing field of implantable left ventricular assist devices (LVADs) lacks studies that evaluate the sexual and psychosocial concerns of LVAD patients. The aim of this prospective study was to determine the sexual and psychosocial behaviors of these patients. A sexual and psychosocial survey was conducted in patients who underwent the implantation of LVAD. Inclusion criteria were patients who were discharged home. The survey consisted of 17 questions with main focus on the sexual life and activities. The survey was sent to 38 patients. Twelve patients had either no partners or did not respond to the survey. Data of the remaining 26 patients with a mean age of 54 ± 13 years old were analyzed. The mean time between LVAD implantation and the first sexual activity was 16 ± 13 weeks (6–42 weeks). Following LVAD implantation, there was a steady improvement in the physical condition and quality of life. However, a remarkable decrease in the degree of satisfaction with sexual life following LVAD implantation (5.5 ± 2.2 vs. 4.1 ± 2.5) was observed (P = 0.05) (a scale of 1–7, with 7 being very satisfied and 1 not satisfied). Decreasing sexual activities after LVAD implantation was mainly to avoid partner disappointment, sudden cardiac arrest, and LVAD failure. There is a notable reduction in the degree of satisfaction with sexual life after LVAD implantation. The majority of the patients avoid discussing this issue with their physicians. Psychological and psychosocial support of LVAD patients is mandatory to improve their life quality.