Heart failure therapy at the turn of the century

Cell-based cardiac pumps and tissue-engineered ventricles

Mortalities resulting from cardiovascular disorders remain high, with an urgent need to develop novel treatment modalities. Tissue-engineering therapies aim to provide cell-based alternatives to conventional options. Significant technological advancements have occurred during the last decade towards the fabrication of functional 3D heart muscle in vitro. More recent research has focused on the development of cell-based cardiac pumps and tissue-engineered ventricles. The global objective of this collective work is to simulate the functional performance of the left ventricle, utilizing completely cell-based options. Current prototypes have shown several physiological performance metrics, including the ability of these devices to generate intraluminal pressure upon electrical stimulation. This review will highlight the transition from tissue engineering 3D heart muscle to cell-based cardiac pumps/ventricles.

Engineering the heart piece by piece: state of the art in cardiac tissue engineering

According to the National Transplant Society, more than 7000 Americans in need of organs die every year owing to a lack of lifesaving organs. Bioengineering 3D organs in vitro for subsequent implantation may provide a solution to this problem. The field of tissue engineering in its most rudimentary form is focused on the developed of transplantable organ substitutes in the laboratory. The objective of this article is to introduce important technological hurdles in the field of cardiac tissue engineering. This review starts with an overview of tissue engineering, followed by an introduction to the field of cardiovascular tissue engineering and finally summarizes some of the key advances in cardiac tissue engineering; specific topics discussed in this article include cell sourcing and biomaterials, in vitro models of cardiac muscle and bioreactors. The article concludes with thoughts on the utility of tissue-engineering models in basic research as well as critical technological hurdles that need to be addressed in the future.

Myocardial engineering in vivo: formation and characterization of contractile, vascularized three-dimensional cardiac tissue

Engineering cardiac tissue in three dimensions is limited by the ability to supply nourishment to the cells in the center of the construct. This limits the radius of an in vitro engineered cardiac construct to approximately 40 microm. This study describes a method of engineering contractile three-dimensional cardiac tissue with the incorporation of an intrinsic vascular supply. Neonatal cardiac myocytes were cultured in vivo in silicone chambers, in close proximity to an intact vascular pedicle. Silicone tubes were filled with a suspension of cardiac myocytes in fibrin gel and surgically placed around the femoral artery and vein of adult rats. At 3 weeks, the tissues in the chambers were harvested for in vitro contractility evaluation and processed for histologic analysis. By 3 weeks, the chambers had become filled with living tissue. Hematoxylin and eosin staining showed large amounts of muscle tissue situated around the femoral vessels. Electron micrographs revealed well-organized intracellular contractile machinery and a high degree of intercellular connectivity. Immunostaining for von Willebrand factor demonstrated neovascularization throughout the constructs. With electrical stimulation, the constructs were able to generate an average active force of 263 microN with a maximum of 843 microN. Electrical pacing was successful at frequencies of 1 to 20 Hz. In addition, the constructs exhibited positive inotropy in response to ionic calcium and positive chronotropy in response to epinephrine. As engineering of cardiac replacement tissue proceeds, vascularization is an increasingly important component in the development of three-dimensional structures. This study demonstrates the in vivo survival, vascularization, organization, and functionality of transplanted myocardial cells.

Positive pressure ventilation in the management of acute and chronic cardiac failure: a systematic review and meta-analysis

Chronic heart failure (CHF) is a common condition and is associated with excess morbidity and mortality, in spite of the many advances in its treatment. Chronic stable heart failure is also associated with an increased incidence of sleep-related breathing disorders, such as central sleep apnoea (CSA) and Cheyne Stokes respiration (CSR). Continuous positive airways pressure (CPAP) has been shown to alleviate the symptoms of CHF, improve left ventricular function and oxygenation. To a certain extent, CPAP also abolishes sleep-related breathing disorders in patients with chronic heart failure. In patients with acute pulmonary oedema, the use of positive pressure ventilation improves cardiac haemodynamic indices, as well as symptoms and oxygenation, and is associated with a lower need for intubation. However, some studies have cast doubts about its safety and suggest a higher rate of myocardial infarction associated with its use. In our opinion, non-invasive positive pressure ventilation and CPAP offers an adjunctive mode of therapy in patients with acute pulmonary oedema and chronic heart failure, who may not be suitable for intubation and in those not responsive to conventional therapies. Non-invasive ventilation also helps to improve oxygenation in those patients with exhaustion and respiratory acidosis. Many trials are still ongoing and the results of these studies would throw more light on the present role of non-invasive ventilation in the management of CHF.

Continuous Renal Replacement Therapy for Management of Overhydration in Heart Failure

An estimated 4.8 million Americans are diagnosed with heart failure. Of those, 5% to 10% meet criteria for the refractory state of the disease. While therapeutic interventions continue to evolve with the changing conceptualization of heart failure pathophysiology, overhydration and its deleterious sequelae remain a problem for those in the refractory state. The incidence of heart failure continues to rise in older individuals. As baby-boomers age across America, greater focus on new, more effective therapies must be considered for treatment of this disease. Continuous renal replacement therapy (CRRT) is one such treatment. The gentle removal of fluid and metabolites while maintaining electrolyte balance helps reduce the effects of overhydration in patients with heart failure. Increasing use of the therapy in the refractory state of heart failure is generating support for early initiation as it continues to demonstrate positive effects. Reduction in edema, attenuation of the sympathoadrenal cascade, and improved respiratory status have all been documented using the therapy. The intent of this article is to provide information for advanced practice nurses and direct care providers regarding CRRT for the treatment of heart failure refractory to typical therapy.