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BACKGROUND: Up to one-half of childhood sarcomeric hypertrophic cardiomyopathy (HCM) presents before the age of 12 years, but this patient group has not been systematically characterized. OBJECTIVES: The aim of this study was to describe the clinical presentation and natural history of patients presenting with nonsyndromic HCM before the age of 12 years. METHODS: Data from the International Paediatric Hypertrophic Cardiomyopathy Consortium on 639 children diagnosed with HCM younger than 12 years were collected and compared with those from 568 children diagnosed between 12 and 16 years. RESULTS: At baseline, 339 patients (53.6%) had family histories of HCM, 132 (20.9%) had heart failure symptoms, and 250 (39.2%) were prescribed cardiac medications. The median maximal left ventricular wall thickness z-score was 8.7 (IQR: 5.3-14.4), and 145 patients (27.2%) had left ventricular outflow tract obstruction. Over a median follow-up period of 5.6 years (IQR: 2.3-10.0 years), 42 patients (6.6%) died, 21 (3.3%) underwent cardiac transplantation, and 69 (10.8%) had life-threatening arrhythmic events. Compared with those presenting after 12 years, a higher proportion of younger patients underwent myectomy (10.5% vs 7.2%; P = 0.045), but fewer received primary prevention implantable cardioverter-defibrillators (18.9% vs 30.1%; P = 0.041). The incidence of mortality or life-threatening arrhythmic events did not differ, but events occurred at a younger age. CONCLUSIONS: Early-onset childhood HCM is associated with a comparable symptom burden and cardiac phenotype as in patients presenting later in childhood. Long-term outcomes including mortality did not differ by age of presentation, but patients presenting at younger than 12 years experienced adverse events at younger ages.

BACKGROUND: Maximal left ventricular wall thickness (MLVWT) is a risk factor for sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM). In adults, the severity of left ventricular hypertrophy has a nonlinear relationship with SCD, but it is not known whether the same complex relationship is seen in childhood. The aim of this study was to describe the relationship between left ventricular hypertrophy and SCD risk in a large international pediatric HCM cohort. METHODS: The study cohort comprised 1075 children (mean age, 10.2 years [±4.4]) diagnosed with HCM (1-16 years) from the International Paediatric Hypertrophic Cardiomyopathy Consortium. Anonymized, noninvasive clinical data were collected from baseline evaluation and follow-up, and 5-year estimated SCD risk was calculated (HCM Risk-Kids). RESULTS: MLVWT Z score was <10 in 598 (58.1%), ≥10 to <20 in 334 (31.1%), and ≥20 in 143 (13.3%). Higher MLVWT Z scores were associated with heart failure symptoms, unexplained syncope, left ventricular outflow tract obstruction, left atrial dilatation, and nonsustained ventricular tachycardia. One hundred twenty-two patients (71.3%) with MLVWT Z score ≥20 had coexisting risk factors for SCD. Over a median follow-up of 4.9 years (interquartile range, 2.3-9.3), 115 (10.7%) had an SCD event. Freedom from SCD event at 5 years for those with MLVWT Z scores <10, ≥10 to <20, and ≥20 was 95.6%, 87.4%, and 86.0, respectively. The estimated SCD risk at 5 years had a nonlinear, inverted U-shaped relationship with MLVWT Z score, peaking at Z score +23. The presence of coexisting risk factors had a summative effect on risk. CONCLUSIONS: In children with HCM, an inverted U-shaped relationship exists between left ventricular hypertrophy and estimated SCD risk. The presence of additional risk factors has a summative effect on risk. While MLVWT is important for risk stratification, it should not be used either as a binary variable or in isolation to guide implantable cardioverter def

Methane concentrations have been measured along salinity profiles in nine tidal estuaries in Europe (Elbe, Ems, Thames, Rhine, Scheldt, Loire, Gironde, Douro and Sado). The Rhine, Scheldt and Gironde estuaries have been studied seasonally. A number of different methodologies have been used and they yielded consistent results. Surface water concentrations ranged from 0.002 to 3.6 µM, corresponding to saturation ratios of 0.7 to 1580 with a median of 25. Methane concentrations in the fresh-water end-members varied from 0.01 to 1.4 µM. Methane concentrations in the marine end-members were close to saturation offshore and on the order of 0.1 µM in estuarine plumes. Methane versus salinity profiles in river-dominated, stratified estuaries (Rhine and Douro) appeared rather erratic whereas those in the well mixed, long-residence time estuaries (Elbe, Ems, Thames, Scheldt, Loire, Gironde and Sado) revealed consistent trends. In these systems dissolved methane initially decreases with increasing salinity, then increases to a maximum at intermediate to high salinities before decreasing again going offshore. Tidal flats and creeks were identified as a methane source to estuarine waters. The global estuarine flux of methane to the atmosphere has been calculated by combining the median water-air methane gradient (68.2 nmol dm-3) with a global area weighted transfer coefficient and the global area of estuaries. Estuaries emit 1.1 to 3.0 Tg CH4 yr-1, which is less than 9% of the global marine methane emission. [KEYWORDS: Douro, Elbe, emission, Ems, estuaries, Gironde, Loire, methane, Rhine, rivers, Sado, Scheldt, Thames], Methane concentrations have been measured along salinity profiles in nine tidal estuaries in Europe (Elbe, Ems, Thames, Rhine, Scheldt, Loire, Gironde, Douro and Sado). The Rhine, Scheldt and Gironde estuaries have been studied seasonally. A number of different methodologies have been used and they yielded consistent results. Surface water concentrations ranged from 0.002 to 3.6 µM, corresponding to saturation ratios of 0.7 to 1580 with a median of 25. Methane concentrations in the fresh-water end-members varied from 0.01 to 1.4 µM. Methane concentrations in the marine end-members were close to saturation offshore and on the order of 0.1 µM in estuarine plumes. Methane versus salinity profiles in river-dominated, stratified estuaries (Rhine and Douro) appeared rather erratic whereas those in the well mixed, long-residence time estuaries (Elbe, Ems, Thames, Scheldt, Loire, Gironde and Sado) revealed consistent trends. In these systems dissolved methane initially decreases with increasing salinity, then increases to a maximum at intermediate to high salinities before decreasing again going offshore. Tidal flats and creeks were identified as a methane source to estuarine waters. The global estuarine flux of methane to the atmosphere has been calculated by combining the median water-air methane gradient (68.2 nmol dm-3) with a global area weighted transfer coefficient and the global area of estuaries. Estuaries emit 1.1 to 3.0 Tg CH4 yr-1, which is less than 9% of the global marine methane emission. [KEYWORDS: Douro, Elbe, emission, Ems, estuaries, Gironde, Loire, methane, Rhine, rivers, Sado, Scheldt, Thames]

Concentrations of nitrous oxide (N2O), oxygen, nitrate, and ammonium, as well as nitrification activity were determined along the salinity gradient of the Schelde Estuary, Northwest Europe, in October 1993, March 1994, and July 1996, The entire estuary was always supersaturated with N2O. Concentrations ranged from 338 nmol dm(-3) (31 times supersaturated) in the O- 2-poor upper estuary, down to about 10 nmol dm(-3) (slight supersaturation) at the mouth of the estuary. Nearly all N2O was lost to the atmosphere within the estuary rather than being transported to the open sea. The mean annual emission from the Schelde estuary to the atmosphere was estimated to be 2.8 X 10(8) g. Per unit area, this flux is large when compared to data published for other estuaries. Nitrification in the water column was the main source of N2O. The oxygen gradient along the estuary controlled the location and intensity of nitrification. In the upper estuary, the maximum nitrification activity was 6.4 mu mol N dm(-3) h(-1). The N2O yield, associated with nitrification, varied spatially and seasonally. Between 0.1% and 0.4% of the oxidised NH4+ was converted to N2O. The total amount of N2O in the estuary appeared to be controlled by the NH4+ concentration of the river water which entered the estuary. [KEYWORDS: nitrous oxide (N2O); nitrification; gas emission Schelde estuary Coastal marine ecosystems; trace gases; nitrosomonas-europaea; sw netherlands; nitric-oxide; elbe estuary; fresh-water; n2o; denitrification; rates], Concentrations of nitrous oxide (N2O), oxygen, nitrate, and ammonium, as well as nitrification activity were determined along the salinity gradient of the Schelde Estuary, Northwest Europe, in October 1993, March 1994, and July 1996, The entire estuary was always supersaturated with N2O. Concentrations ranged from 338 nmol dm(-3) (31 times supersaturated) in the O- 2-poor upper estuary, down to about 10 nmol dm(-3) (slight supersaturation) at the mouth of the estuary. Nearly all N2O was lost to the atmosphere within the estuary rather than being transported to the open sea. The mean annual emission from the Schelde estuary to the atmosphere was estimated to be 2.8 X 10(8) g. Per unit area, this flux is large when compared to data published for other estuaries. Nitrification in the water column was the main source of N2O. The oxygen gradient along the estuary controlled the location and intensity of nitrification. In the upper estuary, the maximum nitrification activity was 6.4 mu mol N dm(-3) h(-1). The N2O yield, associated with nitrification, varied spatially and seasonally. Between 0.1% and 0.4% of the oxidised NH4+ was converted to N2O. The total amount of N2O in the estuary appeared to be controlled by the NH4+ concentration of the river water which entered the estuary. [KEYWORDS: nitrous oxide (N2O); nitrification; gas emission Schelde estuary Coastal marine ecosystems; trace gases; nitrosomonas-europaea; sw netherlands; nitric-oxide; elbe estuary; fresh-water; n2o; denitrification; rates]