This is a cohort study consisting of 2 patient cohorts. The first cohort will be studied retrospectively, using existing blood samples from different biobanks. Biomarkers will be measured and matched with the etiology of previously diagnosed heart failure by a biomarker panel of heart failure experts. This cohort consists of 100 patients each with (1) ischemic cardiomyopathy, (2) dilated cardiomyopathy and (3) diastolic heart failure. Blood samples will be analyzed for novel biomarkers. Investigators will be seeking biomarker candidate(s) alone or in combination which can predict each category of heart failure etiology with over 85% accuracy and the lowest levels of reclassification. A panel of heart failure experts will be assembled, and the appropriate cut-off values determined. Once this goal has been achieved, the prospective study will go ahead.