(1) Background: Immunoglobulin gamma subclass 4 (IgG4) is a serum protein belonging to the immunoglobulin superfamily. It has a central role in certain immune-mediated conditions defined as IgG4-related disease. There is a paucity of data regarding the potential association of IgG4 and cardiovascular diseases. Our aim is to study the serum levels of IgG4 in patients with ischemic and non-ischemic dilated cardiomyopathy (DCM). (2) Methods: patients with ischemic and non-ischemic DCM were included in this study. Non-ischemic DCM was defined as a left ventricular ejection fraction (LVEF) p p < 0.01). This was altered by gender and smoking. (4) Conclusions: The patients with ischemic DCM had increased serum concentrations of IgG4. Future studies are warranted to explore the potential role of an IgG4-mediated process in patients with heart failure with reduced LVEF.
