Third-generation continuous flow left ventricular assist devices

Correlation between Myocardial Function and Electric Current Pulsatility of the Sputnik Left Ventricular Assist Device: In-Vitro Study

This study assesses the electric current parameters and reports on the analysis of the associated degree of myocardial function during left ventricular assist device (LVAD) support. An assumption is made that there is a correlation between cardiac output and the pulsatility index of the pump electric current. The experimental study is carried out using the ViVitro Pulse Duplicator System with Sputnik LVAD connected. Cardiac output and cardiac power output are used as a measure of myocardial function. Different heart rates (59, 73, 86 bpm) and pump speeds (7600–8400 rpm in 200 rpm steps) are investigated. In our methodology, ventricular stroke volumes in the range of 30–80 mL for each heart rate at a certain pump speed were used to simulate different levels of contractility. The correlation of the two measures of myocardial function and proposed pulsatility index was confirmed using different correlation coefficients (values ≥ 0.91). Linear and quadratic models for cardiac output and cardiac power output versus pulsatility index were obtained using regression analysis of measured data. Coefficients of determination for CO and CPO models were in the ranges of 0.914–0.982 and 0.817–0.993, respectively. Study findings suggest that appropriate interpretation of parameters could potentially serve as a valuable clinical tool to assess myocardial therapy using LVAD infrastructure.

Comparative assessment of different versions of axial and centrifugal LVADs: A review

Continuous-flow left ventricular assist devices (LVADs) have gained tremendous acceptance for the treatment of end-stage heart failure patients. Among different versions, axial flow and centrifugal flow LVADs have shown remarkable potential for clinical implants. It is also very crucial to know which device serves its purpose better to treat heart failure patients. A thorough comparison of axial and centrifugal LVADs, which may guide doctors in deciding before the implant, still lacks in the literature. In this work, an assessment of axial and centrifugal LVADs has been made to suggest a better device by comparing their engineering, clinical, and technological development of design aspects. Hydrodynamic and hemodynamic aspects for both types of pumps are discussed along with their biocompatibility, bearing types, and sizes. It has been observed numerically that centrifugal LVADs perform better over axial LVADs in every engineering aspect like higher hydraulic efficiency, better characteristics curve, lesser power intake, and also lesser blood damage. However, the clinical outcomes suggest that centrifugal LVADs experience higher events of infections, renal, and respiratory dysfunction. In contrast, axial LVADs encountered higher bleeding and cardiac arrhythmia. Moreover, recent technological developments suggested that magnetic type bearings along with biocompatible coating improve the life of LVADs.

Approach to Complications of Ventricular Assist Devices: A Clinical Review for the Emergency Provider

BACKGROUND

Heart failure is a major public health problem in the United States. Increasingly, patients with advanced heart failure that fail medical therapy are being treated with implanted ventricular assist devices (VADs).

OBJECTIVE

This review provides an evidence-based summary of the current data for the evaluation and management of implanted VAD complications in an emergency department context.

DISCUSSION

With a prevalence of >5.8 million individuals and >550,000 new cases diagnosed each year, heart failure is a major public health problem in the United States. Increasingly, patients with advanced heart failure that fail medical therapy are being treated with implanted VADs. As the prevalence of patients with VADs continues to grow, they will sporadically present to the emergency department, regardless of whether the facility is a designated VAD center. As a result, all emergency physicians must be familiar with the basic principles of VAD function, as well as the diagnosis and initial management of VAD-related complications. In this review, we address these topics, with a focus on contemporary third-generation continuous flow VADs. This review will help supplement the critical care skills of emergency physicians in managing this complex patient population.

CONCLUSIONS

The cornerstone of managing the unstable VAD patient is rapid initiation of high-quality supportive care and recognition of device-related complications, as well as the identification and use of specialist VAD teams and other resources for support. Emergency physicians must understand VADs so that they may optimally manage these complex patients.

Anesthetic management of the patient with a ventricular assist device

The use of long- and short-term mechanical circulatory support in the form of ventricular assist device (VAD) has increased over the last decade. Although cardiothoracic anesthesiologists care for these patients during device placement, increasingly higher numbers of general anesthesiologists are involved in the management of VAD patients during noncardiac surgery and procedures. An understanding of devices, their indications, and complications is essential to the anesthesiologists caring for these patients. We review the anesthetic considerations for the implantation of these devices and concerns when caring for patients with durable and short-term devices already in place.

Rotary mechanical circulatory support systems

A detailed survey of the current trends and recent advances in rotary mechanical circulatory support systems is presented in this paper. Rather than clinical reports, the focus is on technological aspects of these rehabilitating devices as a reference for engineers and biomedical researchers. Existing trends in flow regimes, flow control, and bearing mechanisms are summarized. System specifications and applications of the most prominent continuous-flow ventricular assistive devices are provided. Based on the flow regime, pumps are categorized as axial flow, centrifugal flow, and mixed flow. Unique characteristics of each system are unveiled through an examination of the structure, bearing mechanism, impeller design, flow rate, and biocompatibility. A discussion on the current limitations is provided to invite more studies and further improvements.

Perioperative management of patients with left ventricular assist devices undergoing noncardiac surgery

Aim:

The aim of this study was to describe our institutional experience, primarily with general anesthesiologists consulting with cardiac anesthesiologists, caring for left ventricular assist device (LVAD) patients undergoing noncardiac surgery.

Materials and Methods:

This is a retrospective review of the population of patients with LVADs at a single institution undergoing noncardiac procedures between 2009 and 2014. Demographic, perioperative, and procedural data collected included the type of procedure performed, anesthetic technique, vasopressor requirements, invasive monitors used, anesthesia provider type, blood product management, need for postoperative intubation, postoperative disposition and length of stay, and perioperative complications including mortality.

Statistical Analysis:

Descriptive statistics for categorical variables are presented as frequency distributions and percentages. Continuous variables are expressed as mean ± standard deviation and range when applicable.

Results:

During the study, 31 patients with LVADs underwent a total of 74 procedures. Each patient underwent an average of 2.4 procedures. Of the total number of procedures, 48 (65%) were upper or lower endoscopies. Considering all procedures, 81% were performed under monitored anesthesia care (MAC). Perioperative care was provided by faculty outside of the division of cardiac anesthesia in 62% of procedures. Invasive blood pressure monitoring was used in 27 (36%) procedures, and a central line, peripherally inserted central catheter or midline was in place preoperatively and used intraoperatively for 38 (51%) procedures. Vasopressors were not required in the majority (65; 88%) of procedures. There was one inhospital mortality secondary to multiorgan failure; 97% of patients survived to discharge after their procedure.

Conclusion:

At our institution, LVAD patients undergoing noncardiac procedures most frequently require endoscopy. These procedures can frequently be done safely under MAC, with or without consultation by a cardiac anesthesiologist.

Arterial pulsatility under phasic left ventricular assist device support

The aim of this study is to understand whether the phasic Continuous Flow Left Ventricular Assist Device (CF-LVAD) support would increase the arterial pulsatility. A Micromed DeBakey CF-LVAD was used to apply phasic support in an ex-vivo experimental platform. CF-LVAD was operated over a cardiac cycle by phase-shifting the pulsatile pump control with respect to the heart cycle, in 0.05 s increments in each experiment. The pump flow rate was selected as the control variable and a reference model was used to operate the CF-LVAD at a pulsatile speed. Arterial pulse pressure was the highest (9 mmHg) when the peak pump flow is applied at the peak systole under varying speed CF-LVAD support over a cardiac cycle while it was the lowest (2 mmHg) when the peak pump flow was applied in the diastolic phase. The mean arterial pressure and mean CF-LVAD output were the same in each experiment while arterial pulse pressure and pulsatility index varied depending on the phase of reference pump flow rate signal. CF-LVAD speed should be synchronized considering the timing of peak systole over a cardiac cycle to increase the arterial pulsatility. Moreover, it is possible to decrease the arterial pulsatility under counter-pulsating CF-LVAD support.

Ventricular assist devices (VAD) therapy: new technology, new hope?

Ventricular assist devices are commonly utilized in the treatment of end-stage heart failure. Advances in continuous flow technology have improved efficiency, size, implantability, extended support, and overall patient outcomes. This has led to an expanded role of left ventricular assist device (LVAD) clinical use and applications. This review describes the advances and current state of LVAD devices and provides a future outlook for this technology.

Fundus fluorescein angiographic findings in patients who underwent ventricular assist device implantation

Disruption of microcirculation in various tissues as a result of deformed blood rheology due to ventricular assist device (VAD) implantation causes novel arteriovenous malformations. Capillary disturbances and related vascular leakage in the retina and choroidea may also be seen in patients supported by VADs. We aimed to evaluate retinal vasculature deteriorations after VAD implantation. The charts of 17 patients who underwent VAD implantation surgery for the treatment of end-stage heart failure were retrospectively reviewed. Eight cases (47.1%) underwent pulsatile pump implantation (Berlin Heart EXCOR, Berlin Heart Mediprodukt GmbH, Berlin, Germany); however, nine cases (52.9%) had continuous-flow pump using centrifugal design (HeartWare, HeartWare Inc., Miramar, FL, USA). Study participants were selected among the patients who had survived with a VAD for at least 6 months, and results of detailed ophthalmologic examinations including optic coherence tomography (OCT) and fundus fluorescein angiography (FA) were documented. All of the 17 patients were male, with a mean age of 48.5 ± 14.8 years (15-67 years). Detailed ophthalmologic examinations including the evaluation of retinal vascular deteriorations via FA were performed at a mean of 11.8 ± 3.7 months of follow-up (6-18 months). Mean best-corrected visual acuity and intraocular pressure were found as logMAR 0.02 ± 0.08 and 14.6 ± 1.9 mm Hg, respectively in the study population. Dilated fundoscopy revealed severe focal arteriolar narrowing in two patients (11.8%), and arteriovenous crossing changes in four patients (23.5%); however, no pathological alteration was present in macular OCT scans. In patients with continuous-flow blood pumps, mean arm-retina circulation time (ARCT) and arteriovenous transit time (AVTT) were found to be 16.8 ± 3.0 and 12.4 ± 6.2 s, respectively; whereas those with pulsatile-flow blood pumps were found to be 17.4 ± 3.6 and 14.0 ± 2.1 s in patients (P=0.526 and P=0.356, respectively). FA also revealed a tendency for increased frequency of dye leakage from the optic disc in our study population. Except for remarkable delays in both ARCT and AVTT as well as a tendency for increased frequency of dye leakage from the optic disc, ophthalmologic evaluations revealed no other significant pathology or vascular deterioration in the retina that could be attributed to artificial heart systems.

Immunosuppression decreases inflammation and increases AAV6-hSERCA2a-mediated SERCA2a expression

The calcium pump SERCA2a (sarcoplasmic reticulum calcium ATPase 2a), which plays a central role in cardiac contraction, shows decreased expression in heart failure (HF). Increasing SERCA2a expression in HF models improves cardiac function. We used direct cardiac delivery of adeno-associated virus encoding human SERCA2a (AAV6-hSERCA2a) in HF and normal canine models to study safety, efficacy, and the effects of immunosuppression. Tachycardic-paced dogs received left ventricle (LV) wall injection of AAV6-hSERCA2a or solvent. Pacing continued postinjection for 2 or 6 weeks, until euthanasia. Tissue/serum samples were analyzed for hSERCA2a expression (Western blot) and immune responses (histology and AAV6-neutralizing antibodies). Nonpaced dogs received AAV6-hSERCA2a and were analyzed at 12 weeks; a parallel cohort received AAV-hSERCA2a and immunosuppression. AAV-mediated cardiac expression of hSERCA2a peaked at 2 weeks and then declined (to ~50%; p<0.03, 6 vs. 2 weeks). LV end diastolic and end systolic diameters decreased in 6-week dogs treated with AAV6-hSERCA2a (p<0.05) whereas LV diameters increased in control dogs. Dogs receiving AAV6-hSERCA2a developed neutralizing antibodies (titer ≥1:120) and cardiac cellular infiltration. Immunosuppression dramatically reduced immune responses (reduced inflammation and neutralizing antibody titers <1:20), and maintained hSERCA2a expression. Thus cardiac injection of AAV6-hSERCA2a promotes local hSERCA2a expression and improves cardiac function. However, the hSERCA2a protein level is reduced by host immune responses. Immunosuppression alleviates immune responses and sustains transgene expression, and may be an important adjuvant for clinical gene therapy trials.