Sandra K. Knecht

Decreased Maximal Aerobic Capacity in Pediatric Chronic Kidney Disease

Adult and pediatric patients with ESRD have impaired maximum oxygen consumption (VO(2) max), a reflection of the cardiopulmonary systems ability to meet increased metabolic demands. We sought to determine factors associated with decreased VO(2) max in pediatric patients with different stages of CKD. VO(2) max was measured using a standardized exercise testing protocol in patients with stage 2 to 4 chronic kidney disease (CKD) (n = 46), in renal transplant recipients (n = 22), in patients treated with maintenance hemodialysis (n = 12), and in age-matched healthy controls (n = 33). VO(2) max was similar between children with stage 2 CKD and controls, whereas lower VO(2) max was observed among children with stage 3 to 4 CKD, those treated with hemodialysis, and transplant recipients. In univariate analysis, VO(2) max was significantly associated with body mass index, resting heart rate, C-reactive protein, serum triglycerides, serum creatinine, and measures of diastolic function; no significant associations with left ventricular structure or systolic function were identified. In multivariate regression analysis, patient category versus control and the presence of diastolic dysfunction were independent predictors of lower VO(2) max. These results suggest that aerobic capacity is decreased in the early stages of CKD in children and that lower VO(2) max can be predicted by the presence of diastolic dysfunction, even if systolic function is normal.

Cardiovascular physiology during supine cycle ergometry and dobutamine stress.

PURPOSE This study compared cardiac hemodynamics during supine cycle ergometry and dobutamine stress. METHODS Thirty-two healthy volunteers (19 female, 13 male, 23.5 +/- 3.5 yr old) completed respective tests on separate days and in random order. Heart rate, blood pressure, and cardiac output were recorded at baseline and peak stress. Echocardiographic measures included left ventricular end-diastolic dimension, fractional shortening, heart rate corrected velocity of circumferential fiber shortening, end-systolic wall stress, and the difference between measured and predicted fiber shortening for measured wall stress. RESULTS Compared with peak exercise, dobutamine infusion resulted in lower cardiac output (12 +/- 2 vs 16 +/- 4 l x min(-1), P < 0.0001), heart rates (163 +/- 7 vs 175 +/- 12 beats x min(-1), P < 0.0001), and systolic blood pressure (160 +/- 22 vs 185 +/- 20 mm Hg, P < or = 0.0001). Echocardiography demonstrated smaller left ventricular end-diastolic dimension (4.2 +/- 0.7 vs 4.5 +/- 0.7 cm, P = 0.013), higher fractional shortening (0.55 +/- 0.07 vs 0.50 +/- 0.06%, P < 0.001), higher VCFc (2.07 +/- 0.36 vs 1.54 +/- 0.20 circs x s(-1), P < 0.001) higher VCFdiff (0.94 +/- 0.35 vs 0.48 +/- 0.20 circs x s(-1), P < 0.001), and lower end-systolic wall stress (25 +/- 11 vs 42 +/- 16 g x cm(-2), P < 0.001). The stress-velocity relationship during dobutamine demonstrated higher y-intercept and steeper slope, indicating greater load-independent contractility. CONCLUSION The cardiovascular adaptation to exercise and dobutamine stress differ significantly. Cardiac output during peak exercise is greater than during peak dobutamine secondary to increased heart rate and stroke volume. Despite a greater increase in contractility and decrease in afterload, a smaller increase in cardiac output during dobutamine stress may be secondary to limited ventricular preload.

Exercise Capacity Improves after Transcatheter Closure of the Fontan Fenestration in Children

OBJECTIVES This study evaluated the aerobic capacity, exercise capacity, and arterial oxygen saturation (O(2)Sat) in children before and after transcatheter Fontan fenestration closure. DESIGN Observational study comparing exercise parameters and hemodynamics before and after transcatheter fenestration closure in Fontan patients. OUTCOME MEASURES Working capacity, exercise duration, oxygen consumption (VO(2)), and arterial O(2)Sat were evaluated during aerobic exercise. RESULTS Twenty patients (mean age 11.4 years) underwent standardized exercise testing before and after fenestration closure. Twelve patients underwent cycle ergometry testing (mean age 14.8 years) (group 1), and eight younger patients (mean age 6.4 years) underwent Bruce treadmill testing (group 2). The same exercise protocol was used in each patient before and after fenestration closure (interval between tests: 118 +/- 142 days). Immediately following fenestration closure at cardiac catheterization, cardiac index decreased (3.0 to 2.1 L/minute/m(2)) and Fontan pressure increased (11 +/- 2 to 12 +/- 2 mm Hg) with an increased arterial saturation (92 to 96%) (P < .001). The total group demonstrated no significant change in pre- and postclosure maximal heart rates (164 +/- 21 and 169 +/- 19 bpm). Rest and exercise O(2)Sat increased (89 and 82 to 95 and 92%) (P < .0001). Exercise duration increased (7.7 +/- 1.9 to 9.2 +/- 2.4 minutes) (P < .0005). Maximal VO(2), indexed maximal VO(2), and total working capacity in kilopond-meters (kpm) increased (1.2 +/- 0.5, 27 +/- 7 and 2466 +/- 1012 to 1.3 +/- 0.4 L/minute, 31 +/- 9 mL/kg/minute and 2869 +/- 1051 kpm, respectively) (P < .005). CONCLUSION In children with a univentricular heart after Fontan palliation, transcatheter fenestration closure improves exercise arterial O(2)Sat and aerobic capacity despite a restricted resting cardiac output documented by catheterization immediately after the closure procedure.

Pediatric Exercise Stress Laryngoscopy following Laryngotracheoplasty A Comparative Review

Objective Exercise-induced airway obstruction in pediatric patients is a unique phenomenon with multiple potential etiologies. An accurate diagnosis can be challenging to establish in pediatric patients because they are frequently asymptomatic at rest. Exercise stress laryngoscopy (ESL) is a modality by which pediatric patients can be evaluated under physiologic conditions that produce their symptoms. The purpose of this study was to demonstrate (1) the diagnostic effectiveness of pediatric ESL and (2) the ability of ESL to guide treatment for “normal” and post–airway reconstruction patients with exercise intolerance. Study Design Case series with chart review. Setting Tertiary care children’s hospital. Subjects and Methods Patients undergoing ESL for exercise intolerance were reviewed. Demographics, surgical history, examination findings, and management recommendations were extracted. Results Thirty-seven patients (average age, 13.5 years; range, 5-21 years) were included. There were 14 male and 23 female patients. Airway abnormalities became evident in 56% of patients. Of these, 24% had focal supraglottic collapse, 43% had evidence of paradoxical vocal fold motion, 24% had combined supraglottic and glottic dysfunction, and 9% had distal airway abnormalities. Overall, 18 patients had changes in management after ESL. Twelve patients in this review had histories of laryngotracheoplasty with equivocal findings on operative bronchoscopy. Of these patients, 10 (83%) received focal diagnoses after ESL. Conclusion ESL is a contemporary modality by which complex patients with undiagnosed exercise intolerance can be effectively evaluated. ESL can be an important tool used to guide treatment in pediatric patients with exercise-induced dyspnea after airway reconstruction.