Using liquid chromatography tandem mass spectrometry to evaluate medication non-adherence in patients admitted with decompensated heart failure

Background Medication nonadherence in heart failure (HF) is common and may contribute to recurrent hospitalisations, but its prevalence in patients admitted with decompensation is not well defined using biochemical testing. Aims To determine the prevalence and clinical correlates of medication non-adherence in patients with established HF admitted with decompensation. Methods We studied consecutive patients with known HF admitted to our tertiary cardiology centre with decompensated HF between June 2025 and January 2026. Urine samples were obtained on admission and analysed by liquid chromatography–tandem mass spectrometry for prescribed HF medications, including renin–angiotensin–aldosterone-system inhibitors (RAASi), beta-blockers (BB), mineralocorticoid receptor antagonists (MRA), Sodium-glucose co-transporter-2 inhibitors (SGLT2i) and diuretics. Medication non-adherence was defined as non-detection of ≥1 prescribed medication in the urine sample. Results Fifty-three patients were included [median (IQR) age 79 (71-85) years; 59% male; 77% Caucasian]. Median (IQR) LVEF 45 (30-52)%; 40% HFrEF (LVEF<40%), 24% HFmrEF (LVEF 41-49%), 36% HFpEF (LVEF≥50%). Median (IQR) NT-proBNP 6023 (2846-15002) ng/L. Forty-three percent (N=23) had ≥4 comorbidities [ischaemic heart disease (42%); atrial fibrillation (53%); hypertension (66%), chronic kidney disease (77%)]. Median number of prescribed medications were 10 (IQR 8-14); RAASi (70%), BB (72%), MRA (25%), SGLT2i (45%), diuretics (83%). Overall, 34 (64%) patients were non-adherent to ≥1 prescribed HF medication; 30% non-adherent to one medication, 21% and 13% to two and three medications respectively. Class-specific non-adherence was highest for SGLT2i (36%) and diuretics (30%). (Figure) Among patients with HFrEF, 71% (15/21) were non-adherent to ≥1 disease-modifying agents [24% non-adherent to RAASi, 5% BB, 33% MRA and 52% SGLT2i]. Compared with adherent patients, those who were non-adherent had more comorbidities (median 4 vs 3, p=0.009), higher pill burden (median 13 vs 8 medications, p<0.001) and lower LVEF (median 41 vs 49%, p=0.04). After adjusting for age and sex, number of prescribed medications (OR 1.40 per additional medication, 95% CI 1.13–1.73; p=0.002) and number of comorbidities (OR 2.30 per additional comorbidity, 95% CI 1.14–4.64; p=0.02) were independently associated with non-adherence. Length of stay (LOS) in hospital was similar for non-adherent versus adherent patients [median (IQR) 9 (6-18) vs 8 (7-13) days, p=0.79]; 2 in-hospital deaths occurred in the non-adherent group. Conclusion In patients with known HF admitted with decompensation, nearly two-thirds were non-adherent to prescribed medications. Higher pill burden and multimorbidity were independently associated with non-adherence. Non-adherence testing during admission may help identify patients for targeted adherence intervention to reduce recurrent HF hospitalisations.