Delphine Yung

Outcomes of Children With Cardiomyopathy Listed for Transplant: A Multi-institutional Study

BACKGROUND Dilated (DCM), restrictive (RCM), and hypertrophic (HCM) cardiomyopathies (CM) in children have varying clinical courses and therapeutic options. Heart transplantation (HTx) offers a chance for long-term survival; but outcomes after listing have not been well defined. METHODS A multi-institutional registry of 3,147 patients listed for HTx (January 1993-December 2006) was used to compare outcomes of 1,320 children with CM (42%) and 1,827 with non-CM (58%) etiologies. Comparisons were made between sub-groups: 1,098 DCM (83%), 145 RCM (11%), and 77 HCM (6%). RESULTS CM patients had a waitlist mortality of 17% vs 32% for non-CM patients (p < 0.0001), with no difference between the CM sub-groups. Risk factors were younger age, black race (relative risk [RR], 1.65; p = 0.009), mechanical ventilation (RR, 3.17; p < 0.001), and extracorporeal membrane oxygenation (RR, 2.16; p < 0.001). Ten-year survival after listing was 66% for CM vs 53% for non-CM (p < 0.0001). HCM and RCM patients aged < 1 year at the time of listing had the highest waitlist mortality and the lowest overall survival. CM patients had a better 10-year survival after HTx (68% vs 61%, p < 0.0001). Risk factors for death early after HTx included mechanical ventilation at HTx (RR, 3.07; p < 0.001), longer ischemic time (RR, 1.27; p = 0.01), and earlier era (RR, 1.77; p = 0.002). Late risk factors included black race (RR, 3.01; p < 0.001), HCM or RCM (RR, 1.93; p = 0.007), and older age (RR, 1.9; p < 0.001). CONCLUSION Children with CM have a lower waitlist mortality and better survival post-HTx than children with a non-CM diagnosis. DCM patients have the best and HCM or RCM patients aged younger than 1 year have the worst overall outcomes.

Cardiopulmonary exercise function among patients undergoing transcatheter pulmonary valve implantation in the US Melody valve investigational trial

OBJECTIVES We assessed the hypothesis that there is an improvement in clinical and physiologic parameters of cardiopulmonary exercise testing (CPET) after implantation of a transcatheter pulmonary valve (TPV). BACKGROUND Transcatheter pulmonary valve provides a new tool for treating conduit stenosis and regurgitation in patients with right ventricle (RV) to pulmonary artery conduit dysfunction. METHODS Patients who underwent a TPV placement between January 2007 and January 2010 (N = 150) were investigated with a standardized CPET protocol before and at 6 months after TPV placement. Cardiopulmonary exercise testing was performed on a mechanically braked cycle ergometer with respiratory gas exchange analysis. RESULTS Six months post TPV, small but statistically significant improvements were observed in the maximum workload (65.0% ± 18.8% to 68.3% ± 20.3% predicted, P < .001) and the ratio of minute ventilation to CO(2) production at the anaerobic threshold (30.8 ± 4.7 to 29.1 ± 4.1, P < .001). There was no significant change in peak oxygen consumption (VO(2)). Patients with pre-TPV hemodynamics consistent with RV dysfunction and patients with a lower pre-TPV peak VO(2) tended to have the greatest improvement in peak VO(2). The correlation between TPV-related improvements in peak VO(2) and baseline clinical variables were weak, however, and these variables could not be used to reliably identify patients likely to have improved peak VO(2) after TPV. CONCLUSION In patients with RV to pulmonary artery conduit dysfunction, TPV is associated with modest improvement in exercise capacity and gas exchange efficiency during exercise.

Bronchodilator Delivery During Simulated Pediatric Noninvasive Ventilation

BACKGROUND: Noninvasive ventilation (NIV) is usually applied using bi-level positive airway pressure devices, and many of these devices use a single-limb patient circuit with an integrated leak port to purge the circuit of exhaled carbon dioxide. Sometimes bronchodilator therapy is indicated in pediatric patients, but there have been no studies of the optimal nebulizer position, with respect to leak, during pediatric NIV. We hypothesized that there would be no differences in albuterol delivery with a vibrating-mesh nebulizer between 3 different positions/exhalation leak valve combinations in the patient circuit during simulated pediatric NIV. METHODS: A simulated upper airway model was attached to a lung model that simulated spontaneous breathing. A noninvasive ventilator equipped with heated wire circuit and heated humidifier was attached to the lung model via a pediatric oronasal mask. Albuterol (5 mg) was delivered with a vibrating-mesh nebulizer, at 3 different circuit position/leak condition combinations: prior to the humidifier and leak valve; between the humidifier and leak valve; and integrated within the mask and after the leak. Albuterol was captured on a filter and quantified with chromatography. RESULTS: Greater albuterol mass was delivered to the filter with the nebulizer integrated into the mask than at any other testing condition (P < .001). In the conditions where the nebulizer was placed prior to the exhalation leak valve, greater drug delivery was observed when the nebulizer was placed proximal to the mask (position 2) than when placed prior to the humidifier (position 3, P = .002). CONCLUSIONS: Albuterol delivery during simulated pediatric NIV was affected by the position of the nebulizer in relation to the expiratory leak valve and the nebulizers distance from the filter. A vibrating-mesh nebulizer placed intra-mask may provide a better alternative for medication delivery than those previously used during pediatric NIV.

Correlating Haller Index and cardiopulmonary disease in pectus excavatum.

BACKGROUND The Haller Index (HI) has become standard for determining the severity of pectus excavatum. We compared patterns of cardiopulmonary dysfunction and their relationship with HI in patients with pectus excavatum. METHODS We performed cardiopulmonary exercise testing and chest computed tomography scans on 90 patients with pectus excavatum deformities at a regional pediatric hospital. RESULTS The median HI was 4.9 in patients with combined dysfunction, 4.4 in patients with isolated pulmonary dysfunction, 3.6 in patients with isolated cardiac dysfunction, and 3.4 in patients with normal function. HI varied significantly by disease group (P < .009). HI was significantly lower in patients with normal forced vital capacity than with abnormal forced vital capacity (P = .001). However, HI was similar in patients with normal and abnormal oxygen pulse (P = .24) or peak oxygen consumption (P = .37). CONCLUSIONS Fifty-nine percent of patients had cardiac and/or pulmonary limitation. A HI greater than 3.6 is associated with pulmonary dysfunction, but not cardiac dysfunction.

The Impact of Heart Failure Severity at Time of Listing for Cardiac Transplantation on Survival in Pediatric Cardiomyopathy

BACKGROUND The survival benefit of heart transplantation in adult heart failure is greatest for the sickest patients and negligible for patients not requiring inotropic or mechanical support. We hypothesized a similar survival benefit of heart transplantation for childhood cardiomyopathies with heart failure. METHODS A merged data set of children registered in both the Pediatric Cardiomyopathy Registry and the Pediatric Heart Transplant Study was used to assess differences in mortality before and after transplant in patients with different levels of heart failure severity. Severity was scored 2 if mechanical ventilatory or circulatory support was required, 1 if intravenous inotropes were required, or 0 if no support was required. RESULTS For 332 eligible children, 12-month mortality after listing was 9% for those with a severity score of 0 (n = 105), 16% with a score of 1 (n = 118), and 26% with a score of 2 (n = 109; p = 0.002) with a 3%, 8%, and 20% mortality with severity scores at listing of 0, 1, and 2, respectively, occurring before transplant. Patients listed with a score of 0 frequently deteriorated: 50% received an allograft or died before transplant with severity scores of 1 or 2. The risk of deterioration increased with previous surgery (relative risk, 3.84; p = 0.03) in the short-term and with lower left ventricular mass z-score at time of presentation (relative risk, 1.74; p = 0.003) in the longer-term. CONCLUSION Pediatric cardiomyopathy patients who require high levels of support receive a survival benefit from heart transplantation that is not shared by patients not requiring intravenous inotropic or mechanical support.

Upper thoracic shape in children with pectus excavatum: Impact on lung function

Pectus excavatum (PE) can present with respiratory complaints in childhood. However severity of the PE, measured by the Pectus Severity Index (PSI), correlates only modestly with reduced vital capacity (VC). We hypothesized that another upper thoracic feature, a pectus gracilis (PG) or slender chest, co‐exists with PE, and impacts lung function.

StepWatch stride counting: Accuracy, precision, and prediction of energy expenditure in children

INTRODUCTION Accuracy and precision of the StepWatch (SW) was tested in typically developing youth (TDY) with the prediction of oxygen consumption derived from stride counts. METHODS Ten TDY (5 boys, 5 girls) with an average age 14.1 years (SD=2.2) enrolled. Participants underwent treadmill cardiopulmonary exercise testing (CPET) wearing two SW devices at 1, 2, 3, and 4 miles per hour (mph). RESULTS Average sign-corrected disagreement for strides counted between the 2 monitors was 0.4 (0.52), 0.2 (0.42), 0.1 (0.32), and 0.1 (0.32) for 1, 2, 3, and 4 mph, respectively. The ratio of SW counts to observed manual counts averaged 100.03% with ICC=0.995. Oxygen consumption equations were derived from resting and walking VO(2), age, gender, and stride counts. CONCLUSIONS Excellent accuracy and precision was documented for treadmill walking speeds up to 4 mph while VO(2) per number of strides taken appears to decrease with age and is lower in girls.

Iloprost drug delivery during infant conventional and high-frequency oscillatory ventilation.

Iloprost is a selective pulmonary vasodilator approved for inhalation by the Food and Drug Administration. Iloprost has been increasingly used in the management of critically ill neonates with hypoxic lung disease. This in vitro study was designed to test the hypothesis that aerosol drug delivery could be effectively administered to infants with both conventional ventilation and high-frequency oscillatory ventilation (HFOV). A neonatal test lung model configured with newborn lung mechanics was ventilated with a conventional ventilator and an HFOV with standard settings. A vibrating-mesh nebulizer was placed (1) proximal to the patient airway in the inspiratory limb between the humidifier probe and patient wye (conventional) as well as between the vent circuit and the endotracheal tube (ETT) for HFOV and (2) between the ventilator and humidifier (distal). Iloprost was nebulized in three separate runs using three new nebulizers in each of the circuit locations. A collecting filter was placed at the distal end of the ETT for each trial. Iloprost was quantified using high-performance liquid chromatography. The percentage of nominal dose delivered was greater with the nebulizer placed proximal to the airway for conventional ventilation (10.74% ± 2%) and HFOV (29% ± 2%) than with it placed in the distal position (2.96% ± 0.2% vs. 0.96% ± 0.8%, respectively; P < 0.05). Drug delivery in proximal position was nearly threefold greater during HFOV than during conventional ventilation. In conclusion, iloprost drug delivery was best achieved when the nebulizer was placed proximal to the patient airway during neonatal mechanical ventilation. Drug delivery appears to be more efficient during HFOV than during conventional ventilation.