This study examined the time course of adaptions in insulin sensitivity (IS) in adolescent boys after acute high-intensity interval exercise (HIIE) and moderate-intensity exercise (MIE). Eight boys (15.1±0.4 y) completed three 3-day experimental trials in a randomised order: 1) 8×1 min cycling at 90% peak power with 75 s recovery (HIIE); 2) cycling at 90% of gas exchange threshold for a duration to match work during HIIE (MIE); and 3) rest (CON). Plasma [glucose] and [insulin] were measured before (PRE-Ex), 24 and 48 h post (24 h-POST, 48 h-POST) in a fasted state, and 40 min (POST-Ex) and 24 h (24 h-POST) post in response to an oral glucose tolerance test (OGTT). IS was estimated using the Cederholm (OGTT) and HOMA (fasted) indices. There was no change to HOMA at 24 h or 48 h-POST (all 0.05). IS from the OGTT was higher POST-EX for HIIE compared to CON (17.4%,=0.010, ES=1.06), and a non-significant increase in IS after MIE compared to CON (9.0%, =0.14, ES=0.59). At 24 h-POST, IS was higher following both HIIE and MIE compared to CON (HIIE:=0.019, 13.2%, ES=0.88; MIE: 9.7%, =0.024, ES=0.65). In conclusion, improvements to IS after a single bout of HIIE and MIE persist up to 24 h after exercise when assessed by OGTT.

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It is unclear whether residual anterograde pulmonary blood flow (APBF) at the time of Fontan is beneficial. Pulsatile pulmonary flow may be important in maintaining a compliant and healthy vascular circuit. We, therefore, wished to ascertain whether there was hemodynamic evidence that residual pulsatile flow at time of Fontan promotes clinical benefit. 106 consecutive children with Fontan completion (1999–2018) were included. Pulmonary artery pulsatility index (PI, (systolic pressure–diastolic pressure)/mean pressure)) was calculated from preoperative cardiac catheterization. Spectral analysis charted PI as a continuum against clinical outcome. The population was subsequently divided into three pulsatility subgroups to facilitate further comparison. Median PI prior to Fontan was 0.236 (range 0–1). 39 had APBF, in whom PI was significantly greater (median: 0.364 vs. 0.177, Mann–Whitney p < 0.0001). There were four early hospital deaths (3.77%), and PI in these patients ranged from 0.214 to 0.423. There was no correlation between PI and standard cardiac surgical outcomes or systemic oxygen saturation at discharge. Median follow-up time was 4.33 years (range 0.0273–19.6), with no late deaths. Increased pulsatility was associated with higher oxygen saturations in the long term, but there was no difference in reported exercise tolerance (Ross), ventricular function, or atrioventricular valve regurgitation at follow-up. PI in those with Fontan-associated complications or the requiring pulmonary vasodilators aligned with the overall population median. Maintenance of pulmonary flow pulsatility did not alter short-term outcomes or long-term prognosis following Fontan although it tended to increase postoperative oxygen saturations, which may be beneficial in later life.

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950 Cardiomyopathy / Univentricular heart, heart failure and pulmonary hypertension in congenital heart diseases Methods: Family screening was offered to 2,372 consecutive unrelated patients; 10,000 subjects (43±7 years old, 52% men) were evaluated (mean 4.2 relatives/family), of which 32% were affected and 6% were possibly affected. Familial study was recommended because of an index case with hypertrophic cardiomyopathy (HCM) in 42%, idiopathic dilated cardiomyopathy (DCM) in 17%, arrhythmogenic right cardiomyopathy (ARCM) in 4%, arrhythmogenic left cardiomyopathy (ALCM) in 1%, left ventricular non-compaction (LVNC) in 4%, Brugada syndrome (BS) in 9%, long QT syndrome (LQTS) in 4% and other conditions in 18%. Index case and non-index cases were defined. Results: Familial disease was confirmed in 47%; 51% with HCM, 53% with DCM, 39% with ARCM, 92% with ALCM, 37% with LVNC, 28% with BS, and 35% with LQTS. 606 affected non-index patients were identified (46% meeting HCM, 19% DCM, 6% ARCM, 3% ALVC, 5% LVNC, 9% BS, and 6% LQTS criteria), in whom appropriate risk stratification and medication, if needed, were initiated. 23% had a family history of sudden death. 20% of all affected were athletes (29% of whom were non-index patients). Cardioverter defibrillator (ICD) implantation was indicated in 359 patients (64% for primary and 36% for secondary prevention). 20% of ICD implanted were in non-index cases. Conclusion:The prevalence of familial disease in inherited cardiac conditions is high. Systematic familial study identified a significant number of asymptomatic affected patients who could benefit from early treatment to prevent complications. Dedicated clinics and multidisciplinary teams are needed for proper screening programs.UNIVENTRICULAR HEART, HEART FAILURE AND PULMONARY HYPERTENSION IN CONGENITAL HEART DISEASES P4522 | BEDSIDE Should we leave pulsatile forward flow after the bidirectional Glenn operation?P. Walker-Smith, Q. Chen, H. Weaver, M. Caputo, S. Stoica, A. Parry, R. Tulloh. University Hospitals Bristol NHS Foundation Trust, Bristol Royal Hospital for Children, Bristol, United KingdomBackground: Children with functionally univentricular hearts undergo a treatment pathway to the Fontan operation. A lack of significant pulmonary artery pulse pressure could be deleterious for pulmonary compliance and long term health of the circuit. We wished to try to determine whether the presence of pulsatile flow at the time of the Fontan improved outcome after this operation. Methods: 148 children who underwent Fontan at our institution from 1999 to 2016 underwent cardiac catheterisation to determine pulse pressure, transpulmonary gradient and pulmonary vascular resistance, along with verification of anatomy and function pre-operatively. At Fontan 48 had undergone pulmonary artery band, 56 had previous systemic to pulmonary shunt and 44 had native pulmonary stenosis to protect their pulmonary vasculature. Comparison was made between those with forward flow (group1) at time of Fontan operation and those without (group...