Mechanical circulatory support system (MCSS)

The heart failure is the only major cardiovascular disease that continues to increase over time, with an estimate prevalence of 1.1-2% both in the United States and in Europe. Furthermore, congestive heart failure is a major health problem with a high mortality rate Heart failure is not a specific disease, but a constellation of signs and symptoms arising from different causes: post-hypertensive cardiomyopathy, primary myocardial disease, post-ischemic cardiomyopathy, valvular disease, abnormal ventricular filling and congenital heart disease. Heart transplantation, as ultimate and effective therapy, is limited by the availability of donor hearts. Since decades researchers have been working to solve this problem by developing Mechanical Circulatory Support Systems (MCSS), that can replace or assist the failing heart. Short-term and intermediate-term ventricular assist devices are used frequently to bridge patients with severe heart failure to recovery. The early TAHs and VADs were mainly driven from an external pneumatic drive unit. The latest generation TAHs and long-term assist devices are electrically powered, ultracompact, totally implantable, and have small wearable drive/control consoles, allowing patients to return to their daily activities. The VADs are mechanical blood pumps that can support or replace the function of the failing left ventricle, right ventricle, or both ventricles. The VADs do not require removal of the native heart and therefore can be used as a bridge to transplantation as well as a temporary support system in patients with expected myocardial recovery. DeBakey reported successful LV assist of patients who could not be weaned from the heart-lung machine [1]. The two primary goals of MCSS are to provide adequate perfusion of the vital organs and to decrease cardiac work until the time of heart recovery or heart transplantation. It is often applied in case of acute heart failure after cardiac surgery (postcardiotomy cardiogenic shock), when weaning from extracorporeal circulation is impossible, in cardiogenic shock due to acute myocardial infarction, in acute myocarditis, in acute rejection of transplanted heart or in high-risk patient percutaneous coronary procedures. Other indication can be evolving myocardial infarction: in fact, mechanical unloading of the left ventricle, by reducing energy requirements of the myocardium, can significantly limit the size of infarct [2]. By the supported site, the VADs can be divided into three main groups. 1.Left ventricular assist devices (LVADs) blood is withdrawn from either the pulmonary veins, left atrium or the apex of the LV and returned to the ascending aorta. Atrial cannulation is easier to perform and is less traumatic for the heart in comparison to the apical cannulation; it is preferred for a temporary LV support. Left ventricular cannulation via the apex provides a better LV unloading as well as a better VAD performance. For that reason the apical cannulation is preferred for LV assist as a bridge to transplantation. 2.Right ventricular assist devices (RVADs): blood is withdrawn from the right atrium and returned to the main pulmonary artery. 3.Bi-ventricular devices (BiVADs): the BiVADs are actually a combination between LVAD and RVAD, and could be seen as a functional replacement of the heart. Furthermore, the VADs can be categorised into Intra-Aortic Balloon Pump (IABP), pulsatile and non-pulsatile VADs [3]. The type of ventricular support as well as the device used differs from patient to patient according to the experience and individual preference of the surgical team and the perspective for ventricular recovery. In current application, for the high severity of the illnesses of target population, there is a general consensus of the scientific panels of minimising ethical conflicts and shifting to rigorous surveillance studies. It is generally underlined the vital role and need of Multicenter Registries [4]. Some of the factors that should be considered in making a decision on which device to use for long-term assistance should include anticoagulation, univentricular vs bi-ventricular failure, mobility, protocol to discharge home and size of patients [5]. Except the IABP, the most frequently implanted devices in Europe are the pneumatic VADs, followed by TAH, centrifugal pumps, and the electromechanical VADs [6]. The main complications during the early phases of mechanical assist are bleeding, right-sided heart failure in case of LVAD, air embolism, progression of multiorgan failure; in the late post-surgical phases the most common complications are infections, thromboembolism and failure of the device [7]. Hemolysis has been observed with centrifugal and axial-flow LVADs [8].