The research in this thesis was limited to the most important signal transduction pathway in the heart and the most frequent drug therapy in heart failure, in order to understand the alterations in the pathophysiology of heart failure patients. Despite the different studies performed, it is still unclear how we can improve the quality of life and prolong survival in patients with heart failure. Other options need to be taken in to consideration for a better therapy of patients with heart failure. Overall, the findings presented in this thesis indicate that cellular changes in heart failure depend on underlying cause and phenotype of the disease.