Evaluation of Cardiac Function after VAD Implantation

Heart failure constitutes a major health problem with a current prevalence of over 5.8 million in the USA and over 23 million worldwide. (Lloyd-Jones, 2010) During the last decades a dramatic increase in the number of heart failure patients and hospitalizations was observed (Curtis et al., 2008) with an incidence of more than 550,000 annually in the USA and a lifetime risk of 20%. Although prevalence increases with age, heart failure can also affect young patients (Lloyd-Jones, 2010; Levy et al, 2002; Lloyd-Jones et al, 2002). It is also estimated that 10% from all HF patients have reached advanced stages of the disease, which is characterized by development of symptoms refractory to standard treatment, often requiring prolonged hospitalizations, intravenous vasoactive medication and diuretics and ultimately, consideration of mechanical support (Ammar et al., 2007). Despite the therapeutic advances in the recent decades and the improvement in prognosis (drugs that counteract neurohormonal activation, devices that prevent or treat lethal arrhythmias and correct dyssynchrony), advanced heart failure remains a lethal clinical syndrome. Mortality rate for patients who had to be hospitalized due to heart failure deterioration is approaching 75% at 5 years; for end stage patients it is almost 80% (Ammar et al., 2007). Cardiac transplantation is currently the best available treatment of advanced heart failure, but it is available to fewer than 2500 patients in the United States each year, when approximately 5–10 people are on the waiting list for each transplant taking place (Taylor et al., 2009). In addition, hundreds of thousands of patients who have severe end-stage heart failure are not eligible for a heart transplant due to concomitant multisystem disease, uncontrolled diabetes, continued tobacco use, or psychosocial limitations; however their condition continuously deteriorates. The limitations of medical therapy in advanced stage heart failure, the lack of donor organ availability, and the large number of patients who do not qualify for transplantation due to contraindications, have spurred interest in mechanical circulatory support (MCS). Since the mid 1980s, for patients experiencing recurrent hospitalizations for heart failure decompensation despite optimal treatment and manifesting symptoms or signs of progressive end organ dysfunction, mechanical support of the circulation with Ventricular Assist Devices (VADs) has a well established and continuously expanding role (Stevenson & Rose, 2003). In addition to short term support of critically ill patients with appropriate devices, long term Left Ventricular Assist Devices (LVADs) have been approved for transplant candidates as bridge to transplantation or for patients suitable for destination