were introduced in the 1950s; so were thiazide diuretics, which caused less toxicity, and are still used. around the same time, the invention of echocardiography by inge edler and hellmuth hertz in 1954 marked a new era in the evaluation of heart failure. in the 1960s, loop diuretics were added to available treatments of fluid retention, while a patient with heart failure received the first heart transplant by christiaan barnard. over the following decades, new drug classes found their place in heart failure therapeutics, including vasodilators like hydralazine; renin-angiotensin system inhibitors; and beta-blockers. economics in 2011, nonhypertensive heart failure was one of the 10 most expensive conditions seen during inpatient hospitalizations in the u.s., with aggregate inpatient hospital costs more than $10.5 billion. heart failure is associated with a high health expenditure, mostly because of the cost of hospitalizations; costs have been estimated to amount to 2% of the total budget of the national health service in the united kingdom, and more than $35 billion in the united states. research directions some research indicates that stem cell therapy may help. although this research indicated benefits of stem cell therapy, other research does not indicate benefit. there is tentative evidence of longer life expectancy and improved left ventricular ejection fraction in persons treated with bone marrow-derived stem cells. the maintenance of heart function depends on appropriate gene expression that is regulated at multiple levels by epignetic mechanisms including dna methylation and histone post-translational modification. currently, an increasing body of research is directed at understanding the role of perturbations of epigenetic processes in cardiac hypertrophy and fibrotic scarring. notes specifically, in one randomized control trial the patients self-identified as black (defined as of african descent), and in one randomized control trial the patients were defined as black, without further details given.