Safety, timing, and outcomes of early post-operative cardiac catheterisation following congenital heart surgery.

OBJECTIVE: The safety of early post-operative cardiac catheterisation has been described following congenital heart surgery. Optimal timing of early post-operative cardiac catheterisation remains uncertain. The aim of this study was to describe the safety of early post-operative cardiac catheterisation and its impact on cardiac ICU and hospital length of stay, duration of mechanical ventilation, and extracorporeal support. METHODS: This single-centre retrospective cohort study compared clinical and outcome variables between "early" early post-operative cardiac catheterisation (less than 72 hours after surgery) and "late" early post-operative cardiac catheterisation (greater than 72 hours after surgery) groups using Chi-squared, Student's t, and log-rank test (or appropriate nonparametric test). RESULTS: In total, 132 patients were included, 22 (16.7%) "early" early post-operative cardiac catheterisation, and 110 (83.3%) "late" early post-operative cardiac catheterisation. Interventions were performed in 63 patients (51.5%), 7 (11.1%) early and 56 (88.9%) late. Complications of catheterisation occurred in seven (5.3%) patients, two early and five late. There were no major complications. Patients in the late group trended towards a longer stay in the cardiac ICU (19 days [7, 62] versus 11.5 days [7.2, 31.5], p = 0.6) and in the hospital (26 days [9.2, 68] versus 19 days [13.2, 41.8], p = 0.8) compared to the earlier group. CONCLUSION: "Early" early post-operative cardiac catheterisation was associated with an overall low rate of complications. Earlier catheterisations trended towards shorter cardiac ICU and hospital length of stays. Earlier catheterisations may lead to earlier recovery for patients not following an expected post-operative course.

Moderators of peak respiratory exchange ratio during exercise testing in children and adolescents with Fontan physiology.

OBJECTIVES: Many patients with Fontan physiology are unable to achieve the minimum criteria for peak effort during cardiopulmonary exercise testing. The purpose of this study is to determine the influence of physical activity and other clinical predictors related to achieving peak exercise criteria, signified by respiratory exchange ratio ≥ 1.1 in youth with Fontan physiology. METHODS: Secondary analysis of a cross-sectional study of 8-18-year-olds with single ventricle post-Fontan palliation who underwent cardiopulmonary exercise testing (James cycle protocol) and completed a past-year physical activity survey. Bivariate associations were assessed by Wilcoxon rank-sum test and simple regression. Conditional inference forest algorithm was used to classify participants achieving respiratory exchange ratio > 1.1 and to predict peak respiratory exchange ratio. RESULTS: Of the n = 43 participants, 65% were male, mean age was 14.0 ± 2.4 years, and 67.4% (n = 29) achieved respiratory exchange ratio ≥ 1.1. Despite some cardiopulmonary exercise stress test variables achieving statistical significance in bivariate associations with participants achieving respiratory exchange ratio > 1.1, the classification accuracy had area under the precision recall curve of 0.55. All variables together explained 21.4% of the variance in respiratory exchange ratio, with peak oxygen pulse being the most informative. CONCLUSION: Demographic, physical activity, and cardiopulmonary exercise test measures could not classify meeting peak exercise criteria (respiratory exchange ratio ≥ 1.1) at a satisfactory accuracy. Correlations between respiratory exchange ratio and oxygen pulse suggest the augmentation of stroke volume with exercise may affect the Fontan patient's ability to sustain high-intensity exercise.

Analyzing the catalytic role of active site residues in the Fe-type nitrile hydratase from Comamonas testosteroni Ni1.

A strictly conserved active site arginine residue (αR157) and two histidine residues (αH80 and αH81) located near the active site of the Fe-type nitrile hydratase from Comamonas testosteroni Ni1 (CtNHase), were mutated. These mutant enzymes were examined for their ability to bind iron and hydrate acrylonitrile. For the αR157A mutant, the residual activity (k cat = 10 ± 2 s(-1)) accounts for less than 1% of the wild-type activity (k cat = 1100 ± 30 s(-1)) while the K m value is nearly unchanged at 205 ± 10 mM. On the other hand, mutation of the active site pocket αH80 and αH81 residues to alanine resulted in enzymes with k cat values of 220 ± 40 and 77 ± 13 s(-1), respectively, and K m values of 187 ± 11 and 179 ± 18 mM. The double mutant (αH80A/αH81A) was also prepared and provided an enzyme with a k cat value of 132 ± 3 s(-1) and a K m value of 213 ± 61 mM. These data indicate that all three residues are catalytically important, but not essential. X-ray crystal structures of the αH80A/αH81A, αH80W/αH81W, and αR157A mutant CtNHase enzymes were solved to 2.0, 2.8, and 2.5 Å resolutions, respectively. In each mutant enzyme, hydrogen-bonding interactions crucial for the catalytic function of the αCys(104)-SOH ligand are disrupted. Disruption of these hydrogen bonding interactions likely alters the nucleophilicity of the sulfenic acid oxygen and the Lewis acidity of the active site Fe(III) ion.

Peak Oxygen Consumption (V̇O 2peak ) Recovery Delay in a Pediatric Fontan Population.

PURPOSE: The purpose of this study is to identify predictors and correlates of VO2RD in youth with Fontan. METHODS: Cardiopulmonary exercise test data was used from a single center, cross-sectional study of children and adolescents (age, 8-21 yr) with Fontan physiology. The VO2RD was determined using time (s) to <90% of V̇O 2peak and categorized as "low" (≤10 s) or "high" (≥10 s). t Tests and χ 2 analysis were used to compare continuous and categorical variables, respectively. RESULTS: The analysis sample included 30 adolescents with Fontan physiology (age, 14.2 ± 2.4 yr; 67% male) with either right ventricular (RV) dominant (40%) or co/left ventricular (Co/LV) dominant (60%) systemic ventricular morphology. There were no differences in V̇O 2peak between the high and low VO2RD groups (high = 1.3 ± 0.4 L·min -1 ; low = 1.3 ± 0.3 L·min -1 ; P = 0.97). VO2RD in participants with RV dominance was significantly greater than in patients with Co/LV dominance (RV = 23.8 ± 15.8 s; Co/LV = 11.8 ± 16.1 s; P = 0.03). CONCLUSIONS: V̇O 2peak was not correlated with VO2RD when analyzed as high/low VO2RD groups. However, morphology of the systemic single ventricle (RV vs Co/LV) may be related to rate of recovery in V̇O 2 after a peak cardiopulmonary exercise test.