Matthew S. Lemler

Chloral Hydrate Sedation for Pediatric Echocardiography: Physiologic Responses, Adverse Events, and Risk Factors

OBJECTIVE. The physiologic responses to chloral hydrate sedation in the setting of a pediatric echocardiography laboratory have not been well documented; neither has the population at risk been identified adequately. The purpose of this study was to describe the physiologic responses to chloral hydrate sedation, to report the occurrence of adverse events, and to identify any risk factors that predicted these adverse events in children who underwent sedation for echocardiography at our institution. METHODS. We analyzed retrospectively 1095 patients who were sedated for echocardiography. Vital signs and oxygen saturations were recorded every 5 minutes, and adverse events were noted. Potential risk factors for sedation-related adverse events were analyzed. RESULTS. Thirty-eight percent of patients were classified as American Society of Anesthesiologists class 3 or 4, reflecting the significant comorbidity in the study population. Hemodynamic responses to chloral hydrate sedation included ≥20% decreases in heart rate (24% of the patients) and blood pressure (59% of the patients). There were no deaths or permanent morbidity. Adverse events occurred in 10.8% of patients and included apnea (n = 3 [0.3%]), airway obstruction (n = 15 [1.4%]), hypoxia (n = 65 [5.9%]), hypercarbia (n = 40 of 603 [6.6%]), hypotension with poor perfusion (n = 4 [0.4%]), vomiting (n = 4 [0.4%]), and prolonged sedation (n = 36 [3.3%]). No intervention was required in 92.5%, minor interventions were necessary in 7%, and major interventions were required in 0.5% of all patients. Multivariate analysis identified only age younger than 6 months as a predictor for adverse events, whereas cyanosis, hospitalization, American Society of Anesthesiologists class, fasting time, oxygen requirement, and use of additional sedation were not predictors. CONCLUSIONS. Moderate decreases in heart rate and blood pressure, in the absence of clinical deterioration, are expected responses to chloral hydrate sedation in this pediatric population. The majority of adverse events were minor, and major events were uncommon. Infants who were younger than 6 months were found to be at higher risk for serious adverse events.

Coarctation index: identification of recurrent coarctation in infants with hypoplastic left heart syndrome after the Norwood procedure

Assessment of recurrent coarctation after the Norwood procedure by routine measures is complicated by the unusual physiology caused by the presence of a modified Blalock-Tausig shunt with distal aortic arch obstruction. We present a new index that uses 2-dimensional measurement of the reconstructed aortic arch, which is highly sensitive and specific in identifying recurrent coarctation after the Norwood procedure in children with hypoplastic left heart syndrome.

Echocardiography, not chest radiography, for evaluation of cannula placement during pediatric extracorporeal membrane oxygenation

Objective: Optimal cannula position is essential during extracorporeal membrane oxygenation (ECMO). We hypothesize that echocardiography is superior to chest radiography in diagnosing abnormal cannula position during ECMO. Design: Retrospective. Setting: Pediatric hospital. Patients: 100 pediatric patients requiring ECMO. Measurements and Main Results: We reviewed the medical records of all ECMO patients (n = 100), including reports of all echocardiograms (n = 326), during the years 2002–2004. Of the 91 patients who had echocardiograms while on ECMO, 33 had at least 1 echocardiogram for cannula-position evaluation. Of the remaining 58 patients with echocardiograms for reasons other than cannula-position evaluation, 4 (7%) were found to have abnormal cannula position. These included arterial cannula (AC) within 2–4 mm of the aortic valve (n = 2), AC across the aortic valve into the left ventricle (n = 1), and venous cannula (VC) abutting the atrial septum (n = 1). Of the 33 patients with echocardiograms for evaluation of cannula position, 8 (24%) required intervention. Of those 8 patients, 4 required cannula repositioning due to VC in the coronary sinus (n = 1), VC abutting atrial septum (n = 1), AC in left subclavian artery (n = 1), and AC within 3 mm of aortic valve (n = 1). The remaining 4 with normal cannula position required upsizing of the VC (n = 2), increased circuit flow (n = 1), or intravascular volume administration (n = 1). Overall, 12 of 91 patients (13%) required intervention based on echocardiographic findings. Chest radiography did not detect abnormalities of ECMO cannula position in any of the 8 patients with this problem, nor were any additional patients with abnormal cannula position identified by chest radiography. Conclusions: Echocardiography appears to be superior to chest radiography for assessing ECMO cannula position in our institution. A prospective study, including cost analysis, comparing chest radiography and echocardiography, is needed to definitely determine the preferred diagnostic test or sequence of tests to establish ECMO cannula position.

Subclinical cardiotoxicity in childhood cancer survivors exposed to very low dose anthracycline therapy

Subclinical cardiotoxicity occurs in childhood cancer survivors following moderate and high anthracycline doses. However, less is known about the subclinical changes in left ventricular (LV) structure that occur after very low anthracycline doses of ≤100 mg/m2. This study was designed to assess LV function and key structural parameters following very low doses of anthracycline.

Assessment of Cardiac Function in Adolescents With Duchenne Muscular Dystrophy: Importance of Neurohormones

Initial signs of cardiac dysfunction caused by Duchenne muscular dystrophy are usually detected during adolescence. However, decreased physical activity can allow better tolerance of decreased cardiac function. Mild myocardial dysfunction secondary to ischemic or idiopathic cardiomyopathy is accompanied by elevation of plasma levels of norepinephrine and atrial natriuretic factor. This is considered an adaptation to maintain adequate perfusion. We evaluated neurohormone levels in 17 adolescents (median age 14 years) with Duchenne muscular dystrophy and different degrees of ventricular dysfunction determined by echocardiography. All patients were asymptomatic. Electrocardiographic abnormalities were present in 14 of 17 (82%). Shortening fraction was below normal in 9 of 17 (53%). Norepinephrine plasma levels were elevated in 3, and all had normal atrial natriuretic factor levels. There was no association between fractional shortening and norepinephrine plasma level (P =.66). The majority of younger adolescents with Duchenne muscular dystrophy and abnormal ventricular function do not show signs of inadequate perfusion, as evidenced by normal measurements of neurohormones. (J Child Neurol 2002;17:191-194).

Relation of right ventricular pacing site to left ventricular mechanical synchrony.

Transvenous pacing leads are regularly placed in the right ventricular (RV) apex. Pediatric patients can develop myopathic changes after long-term RV apical pacing. Left ventricular (LV) mechanical dyssynchrony, estimated with echocardiography, may explain the acute decrease in LV function and long-term histopathologic changes. Ts-4w is an established echocardiographic measurement of LV synchrony, using tissue Doppler imaging (TDI). The purpose of this study was to determine whether TDI could identify acute changes in LV synchrony during pacing from different RV sites. We prospectively measured Ts-4w and Doppler-derived cardiac output after 5 minutes of pacing in 19 subjects undergoing catheter ablation. Each subject underwent pacing at 4 sites in random order: high right atrium, high RV septum (septal), RV outflow tract, and RV apex. Ts-4w was measured during sinus rhythm and each pacing protocol, with a value >65 ms defining mechanical dyssynchrony. Ts-4w during high right atrial (32.6 +/- 17.6 ms) and septal (28.9 +/- 10.9 ms) pacing were not different from sinus rhythm (39.5 +/- 15.5 ms). RV apex (85.7 +/- 18.4 ms) and RV outflow tract (84.2 +/- 20.4 ms) pacing induced mechanical dyssynchrony (p <0.0001). In conclusion, TDI demonstrated significant differences in LV synchrony related to pacing site. Ts-4w may be useful to determine ideal lead placement because it correlates with acutely improved hemodynamics.

Hypertrophic Cardiomyopathy in a Neonate Associated with Nemaline Myopathy

Nemaline myopathy is a congenital nonprogressive skeletal muscle disorder with a characteristic rod body formation in the skeletal muscle fibers. Cardiac involvement in nemaline myopathy is rare, although both dilated and hypertrophic cardiomyopathy have been reported. We describe an infant diagnosed with hypertrophic cardiomyopathy and hypotonia on the first day of life. Muscle biopsy confirmed nemaline myopathy at 3 weeks of age. The diagnosis of nemaline myopathy precluded consideration of heart transplantation, thus shifting the focus to comfort care. This is the earliest presentation of hypertrophic cardiomyopathy reported in the literature in the setting of nemaline myopathy. The approach to determining an etiology for hypertrophic cardiomyopathy in an infant is reviewed.

Health-Related Quality of Life and Functional Status Are Associated with Cardiac Status and Clinical Outcome in Children with Cardiomyopathy

OBJECTIVES To measure the health-related quality of life (HRQOL) and functional status of children with cardiomyopathy and to determine whether they are correlated with sociodemographics, cardiac status, and clinical outcomes. STUDY DESIGN Parents of children in the Pediatric Cardiomyopathy Registry completed the Child Health Questionnaire (CHQ; age ≥ 5 years) and Functional Status II (Revised) (age ≤ 18 years) instruments. Linear and Cox regressions were used to examine hypothesized associations with HRQOL. RESULTS The 355 children evaluated at ≥ 5 years (median 8.6 years) had lower functioning (CHQ Physical and Psychosocial Summary Scores 41.7 ± 14.4 and 47.8 ± 10.7) than that of healthy historical controls. The most extreme CHQ domain score, Parental Impact-Emotional, was one SD below normal. Younger age at diagnosis and smaller left ventricular end-diastolic dimension z score were associated independently with better physical functioning in children with dilated cardiomyopathy. Greater income/education correlated with better psychosocial functioning in children with hypertrophic and mixed/other types of cardiomyopathy. In the age ≥ 5 year cohort, lower scores on both instruments predicted earlier death/transplant and listing for transplant in children with dilated and mixed/other types of cardiomyopathy (P < .001). Across all ages (n = 565), the Functional Status II (Revised) total score was 87.1 ± 16.4, and a lower score was associated with earlier death/transplant for all cardiomyopathies. CONCLUSIONS HRQOL and functional status in children with cardiomyopathy is on average impaired relative to healthy children. These impairments are associated with older age at diagnosis, lower socioeconomic status, left ventricular size, and increased risk for death and transplant. Identification of families at risk for functional impairment allows for provision of specialized services early in the course of disease. TRIAL REGISTRATION ClinicalTrials.gov: NCT00005391.

Anomalous Left Main Coronary Artery Origin From the Right Sinus of Valsalva: A Novel Echocardiographic Screening Method

Anomalous origin of the left main coronary artery from the right sinus (ALMCA) is a rare entity associated with an increased risk for sudden cardiac death. Although transthoracic echocardiography often is the primary screening tool for the diagnosis, its accuracy remains undefined, resulting in the use of more expensive methods such as cardiac catheterization and magnetic resonance imaging when clinical suspicion exists. This report aims to describe a novel echocardiographic screening method for detecting ALMCA and to apply it retrospectively for patients with confirmed findings intraoperatively and/or on autopsy. All patients with a confirmed diagnosis of ALMCA who presented to our institution from 2004 to 2012 were included in the study. Eight patients had adequate images, including two patients with an initial diagnosis of normal coronary origins. A control group consisted of 35 patients with normal coronaries shown by echocardiogram. Five of these patients had normal coronary artery origins confirmed by magnetic resonance imaging (MRI). Echocardiographic images were reviewed, and the left main coronary was identified in the parasternal long-axis view between the aorta and pulmonary trunk. The angle of the left main coronary course was measured. In patients with ALMCA, the proximal course of the vessel was steeper as it coursed posteriorly. In contrast, the course was almost horizontal in patients with normal coronary origins. Based on these findings, a cutoff angle of 28° is proposed. In the parasternal long-axis view, ALMCA can be identified by its anomalous proximal course. This screening method is reliable and increases the accuracy of transthoracic echocardiograms.

Usefulness of external counterpulsation early postoperatively after the Fontan procedure in children

temic venous return, and reduces ventricular afterload. 1‐3 We hypothesized that EC could benefit patients who underwent the Fontan procedure by improving cardiac output in the early postoperative period. EC had not been studied in the postoperative setting, and had never previously performed in the pediatric population. Therefore, this investigation sought to provide preliminary evidence of EC safety and short-term efficacy in children after Fontan surgery. ••• We performed a prospective, within-patient, controlled investigation of EC in children who underwent the Fontan procedure (fenestrated and nonfenestrated) at Children’ s Medical Center, Dallas, from May 1999 to June 2001. Children were considered for participation in the study if they were consecutive pediatric patients for whom parental consent was obtained, if there was an EC machine available, and if EC cuff sizes were deemed appropriate (pediatric-sized cuff straps able to be tightened over a sheepskin barrier to prevent excessive movement and skin irritation during EC). Patients were excluded from study for the following reasons: significant intraoperative surgical complications that may have compromised postoperative neurologic status (defined as 10 minutes of hypotension off bypass with blood pressure less than the fifth percentile for age), extubation before or immediately upon arrival to the cardiac intensive care unit, presence of a cardiac arrhythmia or paced heart rhythm, invasive line(s) in the femoral or lower extremities, peripheral vascular disease, musculoskeletal anomaly involving the lower extremities, significant and prolonged postoperative hemorrhage (3 ml/kg/ hour persisting for 10 hours after arrival to the cardiac intensive care unit), or aortic insuf ficiency. After admission to the cardiac intensive care unit, each patient was assessed for clinical stability. Blood products and/or volume (5% albumin) were administered and inotropes were adjusted at the discretion of the attending physician based on hemodynamic status, chest tube drainage, hemoglobin level, and degree of anticoagulation. Intravenous fluid was administered before the investigation if systemic perfusion was determined to be clinically poor, or if systolic blood pressure decreased below the fifth percentile for age at any time. The study protocol was initiated while patients were sedated and anesthetized with midazolam and fentanyl, before extubation, and after mediastinal blood loss was controlled (3 ml/kg/hour). Inotropes and vasoactive medications were unchanged during the period of investigation. The study protocol was divided into 3 10-minute periods. During the first period, baseline parameters were measured before initiation of EC. This was immediately followed by a 10-minute EC period, and directly thereafter, a postintervention period. The hemodynamic parameters obtained during all 3 periods included cardiac index (CI) by ascending aortic pulse Doppler echocardiography (averaged over 8 cardiac cycles), 4 vital signs (heart rate, blood pressure), and central venous pressure (CVP). Each parameter was measured every minute during the 3 study intervals, except ascending aortic Doppler flow, which was evaluated every 2 minutes. Echocardiographic determinations of CI were made off-line by a single interpreter who was blinded to the period of testing. Blinded interpretation was feasible because EC does not alter ascending aortic Doppler flow patterns.5 Chest tube output and oxygen saturation were recorded throughout the investigation. EC was performed using the Cardiomedics Cardi