Age related differences in clinical phenotype, care and outcomes in ambulance attended acute heart failure: a population-based cohort study

Background Patients attended by emergency medical services (EMS) for acute heart failure (HF) are a high-risk population spanning a wide age spectrum, yet age-related differences in clinical characteristics, care and outcomes remain poorly characterised. Objective To evaluate age-related differences in clinical presentation, treatment and outcomes among EMS-attended acute HF. Methods This retrospective population-based cohort study included all EMS encounters for adults with dyspnoea with a hospital-confirmed diagnosis of HF in Victoria, Australia (1 January 2015 - 30 June 2019). EMS data were linked to emergency department (ED) and hospital records. Patients were categorised by age: ≤54, 55-64, 65-74, 75-84 and ≥85 years old. Clinical characteristics, treatment and outcomes were evaluated by age category. Results 25,183 patients with HF were included (mean age 80.3±10.8 years; 51.6% female). Younger patients were more often males from socioeconomically disadvantaged areas with pre-existing chronic kidney disease and asthma, while older patients (≥85 years) were more often females with pre-existing HF, hypertension and atrial fibrillation (all p<0.001). Coronary artery disease was most common at 75-84 years, and cardiometabolic comorbidities and chronic obstructive pulmonary disease at 65-74 years (all p<0.001). EMS were more likely to accurately recognise HF in older age groups, who presented more often with respiratory distress and tachypnoea, and were more frequently treated with supplemental oxygen and glyceryl trinitrate (all p<0.002). Younger patients more commonly had chest pain, hypotension and tachycardia, prompting more non-HF directed therapy such as aspirin, fluids and adrenaline (all p<0.001). Older patients were more likely to be admitted to hospital, but younger patients had higher rates of intensive care admission, non-invasive ventilation and intubation (all p<0.005). In multivariable analyses, older patients (≥85 years) had higher inpatient, 30-day and long-term mortality (adjusted hazard ratio: 3.66, 95% CI 3.03-4.43), but lower rates of EMS reattendance for dyspnoea (adjusted hazard ratio: 0.79, 95% CI 0.66-0.95), compared to younger patients (≤54 years). Conclusions Patients with acute decompensated HF are a heterogenous group with distinct age-related phenotypes that influence diagnosis, treatment and outcomes. Recognising these patterns may enable more precise pre-hospital risk stratification and management.