Risk strati cation is required to set an exercise prescription for cardiac rehabilitation, but an optimal scheme for congenital heart disease (CHD) is unknown. We piloted a system based on hemodynamic rather than anatomic factors: Function, Oxygen level, Rhythm, Complex/Coronary anatomy, and Elevated load (FORCE). Feasibility, e cacy, and safety of the FORCE tool were evaluated.Methods: Patients <22 years old participating in the Cardiac Fitness Program at Boston Children's Hospital between 02/2017 and 12/2021 were retrospectively analyzed. Assigned FORCE levels, anatomy, adverse events, tness and exercise test data were collected.Results: Of 63 attempts at FORCE classi cation, 62 (98%) were successfully classi ed while one with restrictive cardiomyopathy was not. Thirty-nine (62%) were FORCE 1, 16 (25%) were FORCE 2, and 7 (11%) were FORCE 3. Almost half of FORCE 1 patients had simple or complex CHD and the majority of FORCE 2 patients had single ventricle CHD. FORCE 3 patients were more likely to have serious arrhythmias or cardiomyopathy than those in FORCE 1 or 2 (p<0.001). Postural orthostatic tachycardia syndrome patients appeared in FORCE 1 only. No adverse events occurred over 958 total sessions. The total number of tness sessions/participant was similar across FORCE levels. Conclusion: It was feasible to risk stratify patients with CHD using a clinical FORCE tool. The tool was effective in categorizing patients and simple to use. No adverse events occurred with tness training over nearly 1,000 exercise training sessions. Adding diastolic dysfunction to the original model may add utility.

Background: Infants with single ventricle heart disease have a 20% mortality rate during the first year of life with most deaths occurring prior to Stage II/Glenn. Although the time after the Stage II procedure is believed to be a lower risk period, significant morbidity and mortality may occur during this time. Methods: Retrospective cohort analysis of infants enrolled in the National Pediatric Cardiology Improvement Collaborative who underwent staged single ventricle palliation from 2016-2021 and survived to Stage II operation. Multivariable logistic regression and classification and regression tree analysis were performed to identify risk factors for the composite of mortality or transplantation between Stage II surgery and the first birthday. Candidate variables (n=75) included sociodemographic, prenatal, birth, anatomic, stage I intra- and post-operative, interstage course, and Stage II operative characteristics. Results: Of the 1455 patients in the cohort who survived to Stage II, the overall event rate was 7% (76 (5%) died and 34 (2%) were referred for transplant). Overall event rates at 30 and 100 days after Stage 2 were 2% and 5%, respectively ( Figure 1A ). Independent risk factors for mortality and transplantation included shunt type and AV valve repair at Stage I, ECMO and reintubation after Stage I, pre-operative weight and ≥ moderate AV valve regurgitation prior to Stage II, Stage II cross-clamp time, and comprehensive Stage II surgery ( Figure 1B). Patient race/ethnicity and socioeconomic status were not associated with worse outcome. Conclusions: Mortality rates after Stage II surgery to 1 year of age remain high ~5%. Some of the risk factors identified have been shown to also predict interstage mortality, whereas others (reintubation, pre-operative weight, and Stage II characteristics) may be unique to the period after Stage II. Further research is needed to understand whether risk factor modification results in improved transplant-free survival.

Background: Patients with pulmonary atresia with intact ventricular septum (PA/IVS) and critical pulmonary stenosis (CPS) managed to a biventricular circulation may eventually require pulmonary valve replacement (PVR) for pulmonary regurgitation (PR). Right ventricular (RV) remodeling after PVR has been well described in tetralogy of Fallot (TOF); we sought to investigate RV volumetric and functional changes in PA/IVS using CMR. Methods: A retrospective cohort of PA/IVS and CPS patients who underwent PVR at Boston Children’s Hospital from 1995-2021 with CMR before and after PVR was matched 1:3 with TOF patients by age at PVR. Patients with initial intervention >2 weeks of age or 1.5 ventricle circulation were excluded. Median regression modeling accounting for matching was performed with reduction in indexed right ventricular end diastolic volume (RVEDVi) post PVR as the primary outcome, adjusting for covariates including tricuspid regurgitation (TR) and PVR valve size. Results: Twenty PA/IVS or CPS patients (cases) were matched with 60 TOF (controls), with median age at PVR 14 years; at median follow-up 8 years post PVR, 95% were NYHA Class I. Pre-PVR RVEDVi was similar between groups (165 vs 167 ml/m 2 , p=0.7), although cases had higher RV EF (51.4 vs 48.6%, p=0.03), TR fraction (23 vs 9%, p=0.008), and a trend toward lower RV mass; PR fraction, LV volumes and EF were similar. Pre-PVR RV free wall and LV longitudinal strain were similar, although LV circumferential strain was worse in cases (-15.6 vs -17.1, p=0.01). At median 2 years after PVR, RVEDVi was similarly reduced from 166 to 118 ml/m 2 (p=0.73), although cases had higher RV EF (52.3% vs 46.9%, p=0.007) with less reduction in indexed RV mass (Δ4.5 vs 9.6 g/m 2 , p=0.02); LV volumes and EF were similar. Post PVR, RV and LV longitudinal strain remained unchanged both within and between groups; LV circumferential strain was similar post PVR and remained lower in cases vs controls. Conclusion: Patients with PA/IVS after PVR demonstrate similar RV remodeling to TOF patients, with lesser reduction in RV mass and comparatively better post RV EF. CMR strain imaging found no significant pre-post differences in RV or LV systolic parameters. Further investigation is needed to evaluate for changes in diastolic parameters.

Risk stratification is required to set an exercise prescription for cardiac rehabilitation, but an optimal scheme for congenital heart disease (CHD) is unknown. We piloted a system based on hemodynamic rather than anatomic factors: Function, Oxygen level, Rhythm, Complex/Coronary anatomy, and Elevated load (FORCE). Feasibility, efficacy, and safety of the FORCE tool were evaluated.Methods: Patients <22 years old participating in the Cardiac Fitness Program at Boston Children’s Hospital between 02/2017 and 12/2021 were retrospectively analyzed. Assigned FORCE levels, anatomy, adverse events, fitness and exercise test data were collected.Results: Of 63 attempts at FORCE classification, 62 (98%) were successfully classified while one with restrictive cardiomyopathy was not. Thirty-nine (62%) were FORCE 1, 16 (25%) were FORCE 2, and 7 (11%) were FORCE 3. Almost half of FORCE 1 patients had simple or complex CHD and the majority of FORCE 2 patients had single ventricle CHD. FORCE 3 patients were more likely to have serious arrhythmias or cardiomyopathy than those in FORCE 1 or 2 (p<0.001). Postural orthostatic tachycardia syndrome patients appeared in FORCE 1 only. No adverse events occurred over 958 total sessions. The total number of fitness sessions/participant was similar across FORCE levels.Conclusion: It was feasible to risk stratify patients with CHD using a clinical FORCE tool. The tool was effective in categorizing patients and simple to use. No adverse events occurred with fitness training over nearly 1,000 exercise training sessions. Adding diastolic dysfunction to the original model may add utility.