Initial United States experience with the Paracor HeartNet⁎⁎Paracor Medical, Inc, Sunnyvale, Calif. myocardial constraint device for heart failure

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

Reshaping the Ventricle From Within: MIRTH (Myocardial Intramural Remodeling by Transvenous Tether) Ventriculoplasty in Swine

MIRTH (Myocardial Intramural Remodeling by Transvenous Tether) is a transcatheter ventricular remodeling procedure. A transvenous tension element is placed within the walls of the beating left ventricle and shortened to narrow chamber dimensions. MIRTH uses 2 new techniques: controlled intramyocardial guidewire navigation and EDEN (Electrocardiographic Radial Depth Navigation). MIRTH caused a sustained reduction in chamber dimensions in healthy swine. Midventricular implants approximated papillary muscles. MIRTH shortening improved myocardial contractility in cardiomyopathy in a dose-dependent manner up to a threshold beyond which additional shortening reduced performance. MIRTH may help treat dilated cardiomyopathy. Clinical investigation is warranted.

Cardio-supportive devices (VRD & DCC device) and patches for advanced heart failure: A review, summary of state of the art and future directions

Congestive heart failure (CHF) is a complicated pathophysiological syndrome, leading cause of hospitalization as well as mortalities in developed countries wherein an irregular function of the heart leads to the insufficient blood supply to the body organs. It is an accumulative slackening of various complications including myocardial infarction (MI), coronary heart disease (CAD), hypertension, valvular heart disease (VHD) and cardiomyopathy; its hallmarks include hypertrophy, increased interstitial fibrosis and loss of myocytes. The etiology of CHF is very complex and despite the rapid advancement in pharmacological and device-based interventional therapies still, a single therapy may not be sufficient to meet the demand for coping with the diseases. Total artificial hearts (TAH) and ventricular assist devices (VADs) have been widely used clinically to assist patients with severe HF. Unfortunately, direct contact between the patient's blood and device leads to thromboembolic events, and then coagulatory factors, as well as, infection contribute significantly to complicate the situation. There is no effective treatment of HF except cardiac transplantation, however, genetic variations, tissue mismatch; differences in certain immune response and socioeconomic crisis are an important concern with cardiac transplantation suggesting an alternate bridge to transplant (BTT) or destination therapies (DT). For these reasons, researchers have turned to mechanically driven compression devices, ventricular restraint devices (VRD) and heart patches. The ASD is a combination of all operational patches and cardiac support devices (CSD) by delivering biological agents and can restrain or compress the heart. Present study summarizes the accessible peer-reviewed literature focusing on the mechanism of Direct Cardiac Compression (DCC) devices, VRD and patches and their acquaintance to optimize the therapeutic efficacy in a synergistic way.

The promising future of ventricular restraint therapy for the management of end-stage heart failure

Complicated pathophysiological syndrome associated with irregular functioning of the heart leading to insufficient blood supply to the organs is linked to congestive heart failure (CHF) which is the leading cause of death in developed countries. Numerous factors can add to heart failure (HF) pathogenesis, including myocardial infarction (MI), genetic factors, coronary artery disease (CAD), ischemia or hypertension. Presently, most of the therapies against CHF cause modest symptom relief but incapable of giving significant recovery for long-term survival outcomes. Unfortunately, there is no effective treatment of HF except cardiac transplantation but genetic variations, tissue mismatch, differences in certain immune response and socioeconomic crisis are some major concern with cardiac transplantation, suggested an alternate bridge to transplant (BTT) or destination therapies (DT). Ventricular restraint therapy (VRT) is a promising, non-transplant surgical treatment wherein the overall goal is to wrap the dilated heart with prosthetic material to mechanically restrain the heart at end-diastole, stop extra remodeling, and thereby ultimately improve patient symptoms, ventricular function and survival. Ventricular restraint devices (VRDs) are developed to treat end-stage HF and BTT, including the CorCap cardiac support device (CSD) (CSD; Acorn Cardiovascular Inc, St Paul, Minn), Paracor HeartNet (Paracor Medical, Sunnyvale, Calif), QVR (Polyzen Inc, Apex, NC) and ASD (ASD, X. Zhou). An overview of 4 restraint devices, with their precise advantages and disadvantages, will be presented. The accessible peer-reviewed literature summarized with an important considerations on the mechanism of restraint therapy and how this acquaintance can be accustomed to optimize and improve its effectiveness.

Exo-organoplasty interventions: A brief review of past, present and future directions for advance heart failure management

Heart failure (HF) is a debilitating disease in which abnormal function of the heart leads to imbalance of blood demand to tissues and organs. The pathogenesis of HF is very complex and various factors can contribute including myocardial infarction, ischemia, hypertension and genetic cardiomyopathies. HF is the leading cause of death and its prevalence is expected to increase in parallel with the population age. Different kind of therapeutic approaches including lifestyle modification, medication and pacemakers are used for HF patients in NYHA I-III functional class. However, for advance stage HF patient's (NYHA IV), ventricle assist devices are clinically use and stem cells are under active investigation. Most of these therapies leads to modest symptoms relief and have no significant role in long-term survival rate. Currently there is no effective treatment for advance HF except heart transplantation, which is still remain clinically insignificant because of donor pool limitation. As HF is a result of multiple etiologies therefore multi-functional therapeutic platform is needed. Exo-organoplasty interventions are studied from almost one century. The major goals of these interventions are to treat various kind of heart disease from outside the heart muscle without having direct contact with blood. Various kind of interventions (devices and techniques) are developed in this arena with the passage of time. The purpose of this review is to describe the theory behind intervention devices, the devices themselves, their clinical results, advantages and limitations. Furthermore, to present a future multi-functional therapeutic platform (ASD) for advance stage HF management.

Diastolic ventricular support with cardiac support devices: an alternative approach to prevent adverse ventricular remodeling

Heart failure is a global epidemic with limited therapy. Abnormal left ventricular wall stress in the diseased myocardium results in a biochemical positive feedback loop that results in global ventricular remodeling and further deterioration of myocardial function. Mechanical myocardial restraints such as the Acorn CorCap and Paracor HeartNet ventricular restraints have attempted to minimize diastolic ventricular wall stress and limit adverse ventricular remodeling. Unfortunately, these therapies have not yielded viable clinical therapies for heart failure. Cellular and novel biopolymer-based therapies aimed at stabilizing pathologic myocardium hold promise for translation to clinical therapy in the future.

Optimized ventricular restraint therapy: adjustable restraint is superior to standard restraint in an ovine model of ischemic cardiomyopathy

OBJECTIVE

The effects of ventricular restraint level on left ventricular reverse remodeling are not known. We hypothesized that restraint level affects the degree of reverse remodeling and that restraint applied in an adjustable manner is superior to standard, nonadjustable restraint.

METHODS

This study was performed in 2 parts using a model of chronic heart failure in the sheep. In part I, restraint was applied at control (0 mm Hg, n = 3), low (1.5 mm Hg, n = 3), and high (3.0 mm Hg, n = 3) levels with an adjustable and measurable ventricular restraint (AMVR) device. Restraint level was not altered throughout the 2-month treatment period. Serial restraint level measurements and transthoracic echocardiography were performed. In part II, restraint was applied with the AMVR device set at 3.0 mm Hg (n = 6) and adjusted periodically to maintain that level. This was compared with restraint applied in a standard, nonadjustable manner using a mesh wrap (n = 6). All subjects were followed up for 2 months with serial magnetic resonance imaging.

RESULTS

In part I, there was greater and earlier reverse remodeling in the high restraint group. In both groups, the rate of reverse remodeling peaked and then declined as the measured restraint level decreased with progression of reverse remodeling. In part II, adjustable restraint resulted in greater reverse remodeling than standard restraint. Left ventricular end diastolic volume decreased by 12.7% (P = .005) with adjustable restraint and by 5.7% (P = .032) with standard restraint. Left ventricular ejection fraction increased by 18.9% (P = .014) and 14.4% (P < .001) with adjustable and standard restraint, respectively.

CONCLUSIONS

Restraint level affects the rate and degree of reverse remodeling and is an important determinant of therapy efficacy. Adjustable restraint is more effective than nonadjustable restraint in promoting reverse remodeling.

Imaging of mechanical cardiac assist devices

Diagnostic imaging plays an important role in the assessment of patients with mechanical cardiac assist devices. Therefore, it is important for radiologists to be familiar with the basic components, function, and radiographic appearances of these devices in order to appropriately diagnose complications. The purpose of this pictorial essay is to review indications, components, normal imaging appearances, and complications of surgically and percutaneously implanted ventricular assist devices, intra-aortic balloon pumps, and cardiac meshes.

Successful Implantation of a Left Ventricular Assist Device After Treatment With the Paracor HeartNet

The Paracor HeartNet, a ventricular constraint device for the treatment of heart failure (HF), is implanted through a left lateral thoracotomy. It envelopes the heart like a mesh "bag." This method of application raises the question of whether adhesions with the pericardium allow the safe implantation of a left ventricular assist device (LVAD) if HF worsens. A male patient who had undergone implantation of the Paracor HeartNet 42 months earlier presented with advanced HF for cardiac transplantation. The patient's condition deteriorated, and because no suitable organ for transplantation was available, implantation of an LVAD became necessary. Surgery was performed via a median sternotomy without complications. No severe adhesions were found. This is the first report on "how to do" LVAD implantation after Paracor HeartNet implantation with images and information about cutting the constraint. Because the Paracor HeartNet is "wrapped" around the heart, concerns persist that severe adhesions with the pericardium might occur. In this case, LVAD implantation after therapy with the Paracor HeartNet was without complications, and the expected massive adhesions were absent.

Reoperative cardiac surgery after long-term ventricular support therapy

The use of investigational passive support devices continues to be evaluated in the treatment of heart failure. One concern with this technology is the future need for a reoperation such as coronary artery bypass surgery, placement of a left ventricular assist device or cardiac transplantation. In this report, we describe our experience with two patients who required reoperation after long-term use of a passive ventricular support device.

Reversing Left Ventricular Remodeling in Chronic Heart Failure

Chronic heart failure (CHF) has become an epidemic in the United States, with approximately 550,000 new cases annually. With the evolution of pharmacotherapy targeting neurohormonal pathways, the annual mortality in subjects with New York Heart Association (NYHA) class IV CHF has dramatically improved from 52% in the seminal CONSENSUS trial to less than 20% in more recent trials. Suppression of the renin-angiotensin-aldosterone system remains the first line of neurohormonal blockade followed by the addition of selective beta-adrenoreceptor blockers. For patients with NYHA class I and II symptoms, mortality rates have decreased to approximately 5% or less per year with the use of angiotensin-converting enzyme inhibitors, beta-blockers and aldosterone receptor blockers. However, after achieving optimal doses of the indicated pharmacotherapy, and despite the additional benefits obtained with biventricular pacemakers, there are still many patients who continue to experience signs and symptoms of CHF. Recognizing the beneficial effects of the above treatments on left ventricular (LV) remodeling, strategies have been developed to surgically reshape the left ventricle in patients with LV dilation who have associated poor LV function. This review will discuss the techniques and recent developments regarding surgical reshaping of the dilated, dysfunctional, and remodeled left ventricle.