21 Differentiating early dilated cardiomyopathy from physiological adaptations: insights from stress and rest cardiovascular imaging

<h3>Introduction</h3> Exercise-induced physiological changes, such as left ventricular (LV) dilatation and mildly reduced ejection fraction (EF) of 45–54%, are observed not only in elite athletes, but also in individuals who exercise recreationally. Differentiating early dilated cardiomyopathy (DCM) from physiological cardiac adaptations poses a diagnostic challenge, particularly in non-elite athletes. This study aims to improve differentiation between these two entities, investigating both rest and stress parameters. <h3>Methods</h3> Seventy-one participants underwent N-terminal pro-brain natriuretic peptide (BNP) measurements, cardiopulmonary exercise testing (CPET), echocardiography, and cardiovascular magnetic resonance imaging and spectroscopy (CMR/MRS) at rest and stress. Participants were categorised into controls (17%, EF ≥55%), athletes (16%, EF 45–54%), genotype-positive DCM (9%, EF 45–54%), phenotype-positive DCM (25%, EF &lt;45%), and a ‘grey-zone’ cohort (33%, EF 45–54% without clear cause). Participants were followed up 1–3 years later. <h3>Results</h3> The median LV end-diastolic volume was 109 ml/m², with no significant differences between groups (p=0.5). No healthy controls had a NT-proBNP≥125 pg/ml, compared with athletes (9%), genotypes (33%), phenotypes (53%), and grey-zone (12.5%) groups (p=0.003). All athletes had supranormal CPETs (VO2 max as a percentage of predicted≥120%), compared with phenotypes (6%), controls (66%), genotypes (50%) and grey-zone (52%) groups, (p&lt;0.001), with functional limitations seen only in phenotypes. On follow-up, of the grey-zone cohort who returned (n=16), 50% had an improved EF (group one), and 50% a reduced EF (group two). There was no difference in baseline NT-pro BNP, VO₂ max, nor stress E/e’ measurements between groups. On stress CMR/MRS, there was a significant difference between cardiac output (CO) and PCr/ATP when comparing athletes and group two (CO athlete group 17.4 L/min Vs group two 12.0 L/min, p=0.027; and ATP/PCr athlete group 1.76, Vs group two 1.51; p=0.025), but this was not statistically significant for group one (CO 12.8 L/min, p=0.1 and ATP/PCr 1.61, p=0.2). <h3>Conclusion</h3> Multiple diagnostic investigations are available to provide valuable insights in grey-zone individuals, particularly when used in combination. In particular, the use of CMR/MRS to measure CO and PCr/ATP during stress may offer additional discriminatory value, aiding in the assessment of whether a grey-zone individual is more likely to exhibit athletic adaptations or early DCM.