P10 Defining cardiac MRI change thresholds based on how a patient feels, functions and survives post pulmonary arterial hypertension treatment

IntroductionTo identify minimally important differences (MIDs) for cardiac MRI metrics based on FDA recommendations for a clinical outcome measure that should reflect how a patient feels, functions or survives.MethodsConsecutive treatment-naïve patients with pulmonary arterial hypertension between 2010 and 2022 who had two cardiac MRI scans (at baseline prior to treatment and 12 months following treatment) were identified from the ASPIRE registry. All patients were followed up for one additional year after the second scan. For both scans, cardiac measurements were obtained from a validated fully automated segmentation tool. The MID in cardiac MRI metrics was determined using two distribution-based (0.5 standard deviation and minimal detectable change) and two anchor-based methods (change difference and generalised linear model regression) benchmarked to how a patient “feels” (emPHasis-10 questionnaire), “functions” (incremental shuttle walking test) or “survives” for one-year mortality to changes in cardiac MRI measurements.Results254 patients with PAH were included (aged 53±16 years, 79% female, and 66% categorised as intermediate risk based on 2022 ESC/ERS risk score,). We identified a 5% absolute increase in RV ejection fraction and a 17ml decrease in RV end-diastolic or end-systolic volumes as the MIDs for improvement. Conversely, a 5% decrease in RV ejection fraction and a 10ml increase in RV volumes were associated with worsening.ConclusionThis study establishes clinically relevant cardiac MRI MIDs for how a patient feels, functions or survives in response to PAH treatment. Our results should aid the management of patients in the clinic by identifying clinically meaningful changes in key cardiac MRI metrics and aid researchers by informing power calculations and the selection of endpoints for clinical studies using cardiac MRI.