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Objectives To define whether adults with a Fontan circulation, who have lifelong venous congestion and limited cardiac output, have impaired glomerular filtration rate (GFR) or elevated urinary biomarkers of kidney injury. Methods We measured circulating cystatin C and creatinine (n=70) and urinary creatinine, albumin, kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and N-acetyl glucosaminidase (NAG) (n=59) in ambulatory adult Fontan patients and 20 age-matched and sex-matched controls. Urinary biomarkers were normalised to urine creatinine concentration. Survival free from non-elective cardiovascular hospitalisation was compared by estimated GFR and urinary biomarker levels using survival analysis. Results Cystatin C GFR was lower in the Fontan group compared with controls (114.2±22.8 vs 136.3±12.8 mL/min/1.73 m 2 , p 2 in 14.3% vs 0% of controls. Albumin-to-creatinine ratio (ACR), KIM-1 and NAG were elevated compared with controls; ACR=23.2 (7.6–38.3) vs 3.6 (2.5–5.7) mg/g, p 30 mg/g, was present in 33.9% of the Fontan patients but in none of the controls. Over median 707 (IQR 371–942)-day follow-up, 31.4% of patients had a clinical event. Higher KIM-1 and NAG were associated with higher risk of non-elective hospitalisation or death (HR/+1 SD=2.1, 95% CI 1.3 to 3.3, p=0.002; HR/+1 SD=1.6, 95% CI 1.05 to 2.4, p=0.03, respectively); cystatin C GFR was associated with risk of the outcome (HR/+1 SD=0.66, 95% CI 0.48 to 0.90, p=0.009) but creatinine-based GFR was not (HR/+1 SD=0.91, 95% CI 0.61 to 1.38, p=0.66). Neither ACR nor NGAL was associated with events. Conclusions The Fontan circulation is commonly associated with reduced estimated GFR and evidence for glomerular and tubular injury. Those with lower cystatin C GFR and tubular injury are at increased risk of adverse outcomes.

Background Glomerular filtration rate is a key physiologic variable with a central role in clinical decision making and a strong association with prognosis in diverse populations. Reduced estimated glomerular filtration rate (eGFR) is common among adults with congenital heart disease (ACHD). Methods We conducted a prospective cohort study of outpatient ACHD ≥18 years old seen in 2012-2017. Creatinine and cystatin C were measured; eGFR was calculated using either the creatinine or cystatin C Chronic Kidney Disease–Epidemiology Collaboration equation (CKD-EPICr and CKD-EPICysC, respectively). Survival analysis was performed to define the relationship between eGFR and both all-cause mortality and a composite outcome of death or nonelective cardiovascular hospitalization. Results Our cohort included 911 ACHD (39 ± 14 years old, 49% female). Mean CKD-EPICr and CKD-EPICysC were similar (101 ± 20 vs 100 ± 23 mL/min/1.73 m2), but CKD-EPICr estimates were higher for patients with a Fontan circulation (n = 131, +10 ± 19 mL/min/1.73 m2). After mean follow-up of 659 days, 128 patients (14.1%) experienced the composite outcome and 31 (3.4%) died. CKD-EPICysC more strongly predicted all-cause mortality (eGFR 90 mL/min/1.73 m2: CKD-EPICysC unadjusted HR = 20.2 [95% CI 7.6-53.1], C-statistic = 0.797; CKD-EPICr unadjusted HR = 4.6 [1.7-12.7], C-statistic = 0.620). CKD-EPICysC independently predicted the composite outcome, whereas CKD-EPICr did not (CKD-EPICysC adjusted HR = 3.0 [1.7-5.3]; CKD-EPICr adjusted HR = 1.5 [0.8-3.1]). Patients reclassified to a lower eGFR category by CKD-EPICysC, compared with CKD-EPICr, were at increased risk for the composite outcome (HR = 2.9 [2.0-4.3], P Conclusions Cystatin C–based eGFR more strongly predicts clinical events than creatinine-based eGFR in ACHD. Creatinine-based methods appear particularly questionable in the Fontan circulation.

Background— Exercise oscillatory ventilation (EOV) refers to regular oscillations in minute ventilation (V E ) during exercise. Its presence correlates with heart failure severity and worse prognosis in adults with acquired heart failure. We evaluated the prevalence and predictive value of EOV in patients with single ventricle Fontan physiology. Methods and Results— We performed a cross-sectional analysis and prospective survival analysis of patients who had undergone a Fontan procedure and subsequent cardiopulmonary exercise test. Data were reviewed for baseline characteristics and incident mortality, heart transplant, or nonelective cardiovascular hospitalization. EOV was defined as regular oscillations for >60% of exercise duration with amplitude >15% of average V E . Survival analysis was performed using Cox regression. Among 253 subjects, EOV was present in 37.5%. Patients with EOV were younger (18.8±9.0 versus 21.7±10.1 years; P =0.02). EOV was associated with higher New York Heart Association functional class ( P =0.02) and V E /V CO 2 slope (36.8±6.9 versus 33.7±5.7; P =0.0002), but not with peak V O 2 (59.7±14.3 versus 61.0±16.0% predicted; P =0.52) or noninvasive measures of cardiac function. The presence of EOV was associated with slightly lower mean cardiac index but other invasive hemodynamic variables were similar. During a median follow-up of 5.5 years, 22 patients underwent transplant or died (n=19 primary deaths, 3 transplants with 2 subsequent deaths). EOV was associated with increased risk of death or transplant (hazard ratio, 3.9; 95% confidence interval, 1.5–10.0; P =0.002) and also predicted the combined outcome of death, transplant, or nonelective cardiovascular hospitalization after adjusting for New York Heart Association functional class, peak V O 2 , and other covariates (multivariable hazard ratio, 2.0; 95% confidence interval, 1.2–3.6; P =0.01). Conclusions— EOV is common in the Fontan population and strongly predicts lower transplant-free survival.

We hypothesized that cystatin C estimated glomerular filtration rate (eGFR) would be superior to creatinine eGFR for predicting clinical events in adults with congenital heart disease (ACHD). We measured creatinine & cystatin C in outpatients ≥18 yo with CHD. eGFR was calculated using the Chronic

Background: Adults with congenital heart disease (ACHD) comprise a growing, increasingly complex population. The Boston Adult Congenital Heart Disease Biobank is a program for the collection and storage of biospecimens to provide a sustainable resource for scientific biomarker investigation in ACHD. Methods: We describe a protocol to collect, process, and store biospecimens for ACHD or associated diagnoses developed based on existing literature and consultation with cardiovascular biomarker epidemiologists. The protocol involves collecting urine and ∼48.5 mL of blood. A subset of the blood and urine undergoes immediate clinically relevant testing. The remaining biospecimens are processed soon after collection and stored at −80°C as aliquots of ethylenediaminetetraacetic acid (EDTA) and lithium heparin plasma, serum, red cell and buffy coat pellet, and urine supernatant. Including tubes with diverse anticoagulant and clot accelerator contents will enable flexible downstream use. Demographic and clinical data are entered into a database; data on biospecimen collection, processing, and storage are managed by an enterprise laboratory information management system. Results: Since implementation in 2012, we have enrolled more than 650 unique participants (aged 18-80 years, 53.3% women); the Biobank contains over 11,000 biospecimen aliquots. The most common primary CHD diagnoses are single ventricle status-post Fontan procedure (18.8%), repaired tetralogy of Fallot with pulmonary stenosis or atresia (17.6%), and left-sided obstructive lesions (17.5%). Conclusions: We describe the design and implementation of biospecimen collection, handling, and storage protocols with multiple levels of quality assurance. These protocols are feasible and reflect the size and goals of the Boston ACHD Biobank.