Increased urinary IgM excretion in patients with chest pain due to coronary artery disease.

Background: Micro-albuminuria is a recognized predictor of cardiovascular morbidity and mortality in patients with coronary artery disease. We have previously reported, in diabetic and non-diabetic patients, that an increased urinary excretion of IgM is associated with higher cardiovascular mortality. The purpose of this study was to investigate the pattern of urinary IgM excretion in patients with acute coronary syndrome (ACS) and its correlation to cardiovascular outcome.

Methods: Urine albumin, and IgM to creatinine concentration ratios were determined in 178 consecutive patients presenting with chest pain to the Department of Emergency Medicine (ED) at the University Hospital of Lund. Fifty eight (23 female) patients had ACS, 55 (19 female) patients had stable angina (SA), and 65 (35 female) patients were diagnosed as non-specific chest pain (NS).

Results: Urine albumin and IgM excretions were significantly higher in patients with ACS (p = 0.001, and p = 0.029, respectively) compared to patients with NS-chest pain. During the 2 years follow-up time, 40 (19 female) patients suffered a new major cardiovascular event (ACS, acute heart failure, stroke) and 5 (4 male/1 female) patients died of cardiovascular cause. A high degree of albuminuria and IgM-uria significantly predicted cardiovascular mortality and morbidity (HR = 2.89, 95% CI: 1.48 - 5.66, p = 0.002). Microalbuminuric patients (≥3 mg/mmol) with high IgM-uria (≥0.005 mg/mmol) had a 3-fold higher risk for cardiovascular new events compared to patients with low IgM-uria (RR = 3.3, 95% CI: 1.1 - 9.9, p = 0.001).

Conclusion: In patients with chest pain, an increased urine IgM excretion, is associated with coronary artery disease and long-term cardiovascular complications. Measuring urine IgM concentration could have a clinical value in risk stratification of patients with ACS.