Elevated Serum Levels of IgG4 in Patients with Heart Failure with Reduced Ejection Fraction: A Prospective Controlled Study

SIMPLE SUMMARY: Immunoglobulin is a group of proteins participating in process of inflammation. One of its subtypes is Immunoglobulin Gamma-4 (IgG4) which is related to a rare disease called IgG4-related disease and characterized by a process of fibrosis—deposition of fibers in different organs and inflammation, resulting in tissue damage and dysfunction including the heart muscle and vessels. There is a paucity of information regarding the potential link between of IgG4 and cardiovascular diseases. The purpose of this study is to assess the serum levels of IgG4 in patients with dilated cardiomyopathy (DCM), a disease characterized by cardiac muscle dysfunction of ischemic and non-ischemic origin. Ischemic heart disease is a disease in which heart muscle is damaged by inappropriate blood supply caused by blood vessel obstruction and may cause heart muscle dysfunction. Ninety-eight patients with ischemic and non-ischemic cardiomyopathy were included in this study. The serum concentrations of IgG4 were measured. Patients with DCM had significantly higher levels of IgG4 compared with the healthy control group (77.4 ± 64.0 vs. 50.3 ± 28.8 mg/dL, p < 0.01). Although there was no difference in the total IgG levels in patients with ischemic DCM, the serum concentrations of IgG4 were significantly higher than the corresponding values in the control group (89.8 ± 67.3 vs. 50.3 ± 28.8 mg/dL, p < 0.01). In conclusion, we found that patients with ischemic cardiomyopathy had increased blood levels of IgG4. Additional studies with a larger number of patients are needed to support and explain this finding. ABSTRACT: (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) < 40% without coronary artery disease (CAD). Ischemic DCM was defined as a LVEF < 40% and proven CAD. The serum concentrations of IgG4 were measured by turbidimetry. (3) Results: Overall 98 patients with cardiomyopathy had significantly higher levels of IgG4 compared with the control group (77.4 ± 64.0 vs. 50.3 ± 28.8 mg/dL, p < 0.01). Although there was no difference in the total IgG levels in patients with ischemic DCM, the serum concentrations of IgG4 were significantly higher than the corresponding values in the control group (89.8 ± 67.3 vs. 50.3 ± 28.8 mg/dL; interquartile ranges: 40.4–126.5 vs. 31.8–66.8 mg/dL, 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.