Blood urea monitoring in heart failure patients - an important predictor of mortality

Abstract Background Recent ESC position statement regarding worsening renal failure recommends the use of blood urea monitoring of patients with heart failure with reduced ejection fraction (HFrEF). Although both serum creatinine and blood urea nitrogen are markers for renal dysfunction, blood urea nitrogen levels are also affected by reabsorption in the renal tubules, a process modulated by renin-angiotensin-aldosterone activity, sympathetic nervous activity and arginine-vasopressin activity. Thus, neurohormonal activity is reflected in the BUN/creatinine ratio (bUCR) which effectively ‘normalizes’ BUN for the degree of renal dysfunction, as measured by the creatinine level. Previous studies have demonstrated increased mortality at bUCR >100mmol/l. however, most of the prognostic data has come from patients admitted with acute heart failure. The use of bUCR in patients with chronic HFrHF receiving intensive titration of guideline directed medical therapy (GDMT) has not been studied. Purpose To identify the extent of blood urea monitoring in primary care in HFrEF and whether bUCR remains a significant prognostic indicator despite intensive GDMT. Methods We analysed the electronic health records of all patients referred to the Heart Failure Nurse Service (HFNS) in an NHS population approx. 400,000 in 2022. Inclusion criteria consists of patients with symptomatic heart failure NYHA II-IV with echocardiogram demonstrating HFrEF. Patients were segregated into two cohorts, with a urea/creatinine ratio greater or less than 100mmol/l and analysed. Results Data from 338 patients [mean age 72.3 ± 15.6 years; 218 (64.5%) males; 143 (42.3%) ischaemic cardiomyopathy; 141 (41.7%) AF; 49 (14.5%)] were analysed. Of these, 112 (33.1%) had chronic kidney disease (CKD) with eGFR <60 ml/min/1.73m2 at the time of HF diagnosis and 181 (53.6%) had CKD on discharge from the HFNS. During follow-up, 132 (39%) had further admission with HF and 76 (22.5%) died. Sixty-eight (20.1%) patients did not have blood urea checked despite the availability of serum creatinine. While an eGFR < 60 ml/min/1.73m2 at discharge was associated with a twofold increased risk of death (OR 2.4, 95% CI 1.1-5.3, p=0.029), a bUCR > 100mmol/l at discharge was associated with a four-times greater risk of death (OR 4.2, 95% CI 2.2-7.9, p <0.001). Conclusion Blood urea/creatinine ratio is an important predictor of outcome and can be utilised to help identify at-risk patients with HFrEF despite intensive GDMT.Survival from diagnosis bUCR