Use of cardiac magnetic resonance imaging to evaluate cardiac structure, function and fibrosis in children with infantile Pompe disease on enzyme replacement therapy

BACKGROUND

Pompe disease (acid α-glucosidase deficiency) is one of several lysosomal storage diseases amenable to treatment with enzyme replacement therapy (ERT). While echocardiography (echo) has been the standard method to evaluate the cardiac response to ERT, cardiac magnetic resonance imaging (CMR) has the advantage of a better tissue definition and characterization of myocardial fibrosis. However, CMR for Pompe disease is not frequently performed due to a high risk of sedation. We report the first use of CMR in a feasible protocol to quantify left ventricular (LV) mass, function, and the presence of myocardial fibrosis in the Pompe population.

METHODS

Children with Pompe disease on ERT were assessed with transthoracic echo and CMR over a 3 year period at a single institution. Echocardiography was performed using standard techniques without sedation. CMR was performed using retrospectively gated and real-time imaging, with and without sedation. LV mass indexed to body surface area (LVMI) and ejection fraction (EF) were measured by both echo and CMR, and evaluated for change over time. Myocardial fibrosis was assessed by CMR with delayed enhancement imaging 5-10 min after gadolinium contrast using single shot inversion recovery sequences with inversion time set to null the signal from normal myocardium.

RESULTS

Seventeen CMR scans were successfully performed in 10 subjects with Pompe disease (median age at first CMR is 9 months, range 1-38 months, 80% male), with sedation only performed in 4 studies. There was a median interval of 5 months (range 0-34 months) from the start of ERT to first CMR (baseline). At baseline, the median indexed LVMI by CMR (140.0 g/m(2), range 43.8-334.0) tended to be lower than that assessed by echo (median 204.0 g/m(2), range 52.0-385.0), but did not reach statistical significance. At baseline, CMR EF was similar to that assessed by echo (55% vs. 55%). Overall, there was no significant decrease in CMR measured LVMI over time (CMR median LVMI at baseline 94 g/m(2) (range 43.8-334) vs. CMR median at most recent study 44.5 g/m(2) (range 34-303), p=0.44). In 5 patients with serial CMR scans over time, LVMI decreased in 2, was similar in 2, and increased in 1 patient with high sustained antibodies to exogenous enzyme. Delayed enhancement was noted in only l separate patient who also had high sustained antibodies to exogenous enzyme.

CONCLUSION

CMR is an imaging tool that is feasible to use to serially follow LVMI and EF in children with Pompe disease on ERT. Real-time imaging is adequate for quantification purposes in these patients and minimizes the need for sedation. Quantitative CMR LVMI is generally lower than echo derived LVMI. Delayed enhancement appears to be a rare finding by CMR in Pompe disease. A further follow-up is necessary to better understand the long term effects of ERT in infantile Pompe survivors, especially those with high sustained antibody titers or advanced cardiac disease at treatment outset.

Linking clinical registry data with administrative data using indirect identifiers: implementation and validation in the congenital heart surgery population

BACKGROUND

The use of clinical registries and administrative data sets in pediatric cardiovascular research has become increasingly common. However, this approach is limited by relatively few existing datasets, each of which contain limited data, and do not communicate with one another. We describe the implementation and validation of methodology using indirect patient identifiers to link The Society of Thoracic Surgeons Congenital Heart Surgery (STS-CHS) Database to The Pediatric Health Information Systems (PHIS) Database (a pediatric administrative database).

METHODS

Centers submitting data to STS-CHS and PHIS during 2004 to 2008 were included (n=30). Both data sets were limited to patients 0 to 18 years old undergoing cardiac surgery. An exact match was defined as an exact match on each of the following: date of birth, date of admission, date of discharge, sex, and center. Likely matches were defined as an exact match for all variables except ±1 day for one of the date variables.

RESULTS

Of 45,830 STS-CHS records, 87.4% matched to PHIS using the exact match criteria and 90.3% using the exact or likely match criteria. Validation in a subset of patients revealed that 100% of exact and likely matches were true matches.

CONCLUSIONS

This analysis demonstrates that indirect identifiers can be used to create high-quality link between a clinical registry and administrative data set in the congenital heart surgery population. This methodology, which can also be applied to other data sets, allows researchers to capitalize on the strengths of both types of data and expands the pool of data available to answer important clinical questions.

Corticosteroids and outcome in children undergoing congenital heart surgery: analysis of the Pediatric Health Information Systems database

BACKGROUND

Children undergoing congenital heart surgery often receive corticosteroids with the aim of reducing the inflammatory response after cardiopulmonary bypass; however, the value of this approach is unclear.

METHODS AND RESULTS

The Pediatric Health Information Systems Database was used to evaluate outcomes associated with corticosteroids in children (0 to 18 years of age) undergoing congenital heart surgery at 38 US centers from 2003 to 2008. Propensity scores were constructed to account for potential confounders: age, sex, race, prematurity, genetic syndrome, type of surgery (Risk Adjustment in Congenital Heart Surgery [RACHS-1] category), center, and center volume. Multivariable analysis, adjusting for propensity score and individual covariates, was performed to evaluate in-hospital mortality, postoperative length of stay, duration of ventilation, infection, and use of insulin. A total of 46 730 children were included; 54% received corticosteroids. In multivariable analysis, there was no difference in mortality among corticosteroid recipients and nonrecipients (odds ratio, 1.13; 95% confidence interval, 0.98 to 1.30). Corticosteroids were associated with longer length of stay (least square mean difference, 2.18 days; 95% confidence interval, 1.62 to 2.74 days), greater infection (odds ratio, 1.27; 95% confidence interval, 1.10 to 1.46), and greater use of insulin (odds ratio, 2.45; 95% confidence interval, 2.24 to 2.67). There was no difference in duration of ventilation. In analysis stratified by RACHS-1 category, no significant benefit was seen in any group, and the association of corticosteroids with increased morbidity was most prominent in RACHS-1 categories 1 through 3.

CONCLUSION

In this observational analysis of children undergoing congenital heart surgery, we were unable to demonstrate a significant benefit associated with corticosteroids and found that corticosteroids may be associated with increased morbidity, particularly in lower-risk patients.

Globalization of pediatric research: analysis of clinical trials completed for pediatric exclusivity

OBJECTIVE

We evaluated the setting of published studies conducted under the US Pediatric Exclusivity Provision, which provides economic incentives to pharmaceutical companies to conduct drug studies with children.

METHODS

Published studies containing the main results of trials conducted in 1998-2007 under the Pediatric Exclusivity Provision were included. Data were extracted from each study and described, including the therapeutic area of drug studied, number of patients enrolled, number of sites, and location where the study was conducted, if reported.

RESULTS

Overall, 174 trials were included (sample size: 8-27 065 patients); 9% did not report any information regarding the location or number of sites where the study was conducted. Of trials that did report such information, 65% were conducted in >or=1 country outside the United States, and 11% did not include any sites in the United States. Fifty-four countries were represented, and 38% of trials enrolled patients in >or=1 site located in a developing/transition country, including more than one-third of infectious disease, cardiovascular, and allergy/immunology trials.

CONCLUSIONS

The majority of published pediatric trials conducted under the Pediatric Exclusivity Provision included sites outside the United States, and more than one-third of trials enrolled patients in developing/transition countries.

Congenital heart surgery outcomes in Down syndrome: analysis of a national clinical database

OBJECTIVE

We describe patient characteristics and postoperative morbidity and mortality rates for patients with Down syndrome undergoing congenital heart disease surgery.

METHODS

This retrospective cohort study used the Society of Thoracic Surgeons Congenital Heart Surgery Database to compare patient characteristics and postoperative outcomes for patients (0-18 years) with or without Down syndrome who underwent surgery in 2000-2008.

RESULTS

A total of 45,579 patients (4350 patients with Down syndrome and 41,229 without Down syndrome) were included (median age: 7 months [interquartile range [IQR]: 47 days to 4 years]; 56% male). Patients with Down syndrome were younger at surgery, with the exception of those undergoing tetralogy of Fallot repair or atrioventricular septal defect repair. Mortality rates for patients with or without Down syndrome did not differ significantly. Lengths of stay were prolonged for patients with Down syndrome undergoing atrial septal defect closure (median: 4 days [IQR: 3-5 days] vs 3 days [IQR: 2-4 days]; P < .0001), ventricular septal defect closure (median: 5 days [IQR: 4-8 days] vs 4 days [IQR: 3-6 days]; P < .0001), or tetralogy of Fallot repair (7 days [IQR: 5-10 days] vs 6 days [IQR: 5-9 days]; P < .001) and were associated with postoperative respiratory and infectious complications. Patients with Down syndrome undergoing ventricular septal defect closure had a higher rate of heart block requiring pacemaker placement (2.9% vs 0.8%; P < .0001).

CONCLUSION

In this large, contemporary cohort, Down syndrome did not confer a significant mortality risk for the most common operations; however, postoperative morbidity remained common.

Center variation and outcomes associated with delayed sternal closure after stage 1 palliation for hypoplastic left heart syndrome

OBJECTIVE

There is debate whether primary or delayed sternal closure is the best strategy after stage 1 palliation for hypoplastic left heart syndrome. We describe center variation in delayed sternal closure after stage 1 palliation and associated outcomes.

METHODS

Society of Thoracic Surgeons Congenital Database participants performing stage 1 palliation for hypoplastic left heart syndrome from 2000 to 2007 were included. We examined center variation in delayed sternal closure and compared in-hospital mortality, prolonged length of stay (length of stay > 6 weeks), and postoperative infection in centers with low (< or = 25% of cases), middle (26%-74% of cases), and high (> or = 75% of cases) delayed sternal closure use, adjusting for patient and center factors.

RESULTS

There were 1283 patients (45 centers) included. Median age at surgery was 6 days (interquartile range, 4-9 days), and median weight at surgery was 3.2 kg (interquartile range, 2.8-3.5 kg); 59% were male. Delayed sternal closure was used in 74% of cases (range, 3%-100% of cases/center). In centers with high (n = 23) and middle (n = 17) versus low (n = 5) delayed sternal closure use, there was a greater proportion of patients with prolonged length of stay and infection, and a trend toward increased in-hospital mortality in unadjusted analysis. In multivariable analysis, there was no difference in mortality. Centers with high and middle delayed sternal closure use had prolonged length of stay (odds ratio, 2.83; 95% confidence interval, 1.46-5.47; P = .002 and odds ratio, 2.23; confidence interval, 1.17-4.26; P = .02, respectively) and more infection (odds ratio, 2.34; confidence interval, 1.20-4.57; P = .01 and odds ratio, 2.37; confidence interval, 1.36-4.16; P = .003, respectively).

CONCLUSION

Use of delayed sternal closure after stage 1 palliation varies widely. These observational data suggest that more frequent use of delayed sternal closure is associated with longer length of stay and higher postoperative infection rates. Further evaluation of the risks and benefits of delayed sternal closure in the management of these complex infants is necessary.

Risk factors and comorbidities associated with obesity in children and adolescents after the arterial switch operation and Ross procedure

BACKGROUND

Over 25% of patients with congenital heart disease are obese (OB) or overweight (OW). Unique factors such as activity restriction and early feeding practices may play a role. We evaluated a high-risk cohort predisposed to early coronary artery disease due to past surgery involving coronary artery reimplantation.

METHODS

Patients at our institution who underwent the arterial switch or Ross operation were included. Data collection included chart review and activity and diet questionnaires. The proportion of OB/OW (body mass index > or =85%) was compared to national data. Factors associated with OB/OW were evaluated.

RESULTS

A total of 106 patients were enrolled. Median age was 14.2 years (6.0-19.9 years); 69% were male. Similar to national data, 31% were OB/OW (vs 31%, P = nonsignificant [NS]). There was no difference comparing OB/OW to normal-weight patients in activity restriction (cardiologist documented 27% vs 27%; parent reported 38% vs 42%, P = NS), activity level (9.8 hours/week [1.7-41.2] vs 11.5 [0.8-52.3], P = NS), or early feeding practices (formula vs breastfeeding, caloric fortification, tube feeding). OB/OW patients were more likely to have an OB parent (70% vs 37%, P = .01). Left ventricular mass index was higher in OB/OW patients (48.8 g/m(2.7) [24.4-120.6] vs 37.7 g/m(2.7) [16.5-85.1], P = .01).

CONCLUSIONS

Nearly one third of ASO and Ross patients were OB/OW. Obese/overweight was not found to be related to activity restriction or early feeding practices, but was associated with parental obesity. Obese or OW patients had higher left ventricular mass. Obesity and associated comorbidities may pose additional cardiovascular risk in this unique population who underwent coronary artery reimplantation in childhood.

Accuracy of intraoperative transesophageal echocardiography in the prediction of future neo-aortic valve function after the Ross procedure in children and young adults

OBJECTIVE

Neo-aortic insufficiency (neo-AI) has been noted following the Ross procedure. The purpose of this study was to evaluate the ability of intraoperative transesophageal echocardiography (TEE) to predict future neo-AI in pediatric patients undergoing the Ross from January 1995 to December 2003, who had an intraoperative TEE, and discharge and follow-up transthoracic (TTE) echocardiograms.

DESIGN

Retrospective case series.

PATIENTS

All patients who underwent the Ross procedure at Children's Hospital of Philadephia between January 1995 and December 2003, and had an intraoperative TEE, discharge, and follow-up (>6 months) transthoracic echocardiogram (TTE) (by July 1, 2004) were included.

OUTCOME MEASURES

Grade of neo-AI was assessed on intraoperative TEE, discharge, and follow-up TTE echocardiogram reports.

RESULTS

Follow-up was available in 99/115 (86%) survivors. Median age at Ross was 9.3 years (4 days-34 years). No patient had more than mild neo-AI on intraoperative TEE. At discharge, 2 patients (2%) had moderate neo-AI. At most recent follow-up (median 4.2 years, 8 months-9.3 years), 21 patients (21%) had moderate or greater neo-AI; 9 underwent neo-aortic reintervention. The presence of any neo-AI on intraoperative TEE had 100% sensitivity and negative predictive value for diagnosing moderate or greater neo-AI at discharge. Patients who had mild neo-AI on TEE were more likely to have moderate or greater neo-AI at most recent follow-up than those patients with no neo-AI on TEE (9% vs. 30%, P = 0.01).

CONCLUSION

Intraoperative TEE is an excellent screening tool for the presence of significant neo-AI at the time of hospital discharge. Neo-AI progresses over time after Ross procedure and is more likely to progress in those patients with neo-AI on intraoperative TEE. However, predictive validity decreases over time as neo-AI progresses.

Coronary artery pattern and age impact exercise performance late after the arterial switch operation

OBJECTIVE

The impact of coronary artery pattern on exercise performance after the arterial switch operation is unknown. The purpose of this study was to evaluate the relationship between coronary artery pattern and exercise performance late after the arterial switch operation.

METHODS

Patients who underwent the arterial switch operation and were referred for exercise stress testing between January of 1996 and April of 2005 were included. Univariate and multivariate analyses were performed to identify risk factors for lower maximum heart rate and percent of predicted peak oxygen consumption.

RESULTS

Fifty-three patients were included; 72% were male. The median age at the arterial switch operation was 5 days (1 day to 3.6 years); 32% had concurrent ventricular septal defect repair. The time from the arterial switch operation to exercise stress testing was 14.1 years (7.7-20.6 years). There were 37 patients with the usual coronary artery pattern, and 16 patients (30%) with variant coronary artery patterns. At exercise stress testing, there was no difference in respiratory exchange ratio (1.16 +/- 0.1 for both), indicating similar effort. Compared with patients with the usual coronary artery pattern, patients with variant coronary artery patterns had a significantly lower maximum heart rate (177 +/- 16 beats/min [89% predicted] vs 186 +/- 11 beats/min [93% predicted], respectively, P = .04). Percent of predicted peak oxygen consumption was not significantly different between patients with the usual coronary pattern and patients with variant coronary artery patterns (89% +/- 20% vs 80% +/- 17%, respectively, P = .12). In multivariate analysis, variant coronary artery patterns (P = .03) and ventricular septal defect (P = .004) were predictors of significantly lower maximum heart rate and were associated with a trend toward lower percent of predicted peak oxygen consumption (P < .09). Longer follow-up time was the strongest predictor of lower percent of predicted peak oxygen consumption (P < .001).

CONCLUSIONS

Variant coronary artery patterns are associated with chronotropic impairment, and longer follow-up time is the strongest predictor of diminished aerobic capacity late after arterial switch operation.

The Relationship Between Neo-Aortic Root Dilation, Insufficiency, and Reintervention Following the Ross Procedure in Infants, Children, and Young Adults

OBJECTIVES

The purpose of this study was to describe the relationship between neo-aortic root size, neo-aortic insufficiency (AI), and reintervention at mid-term follow-up.

BACKGROUND

Data on neo-aortic valve function and growth after the Ross procedure in children are limited.

METHODS

A total of 74 of 119 Ross patients from January 1995 to December 2003 had > or =2 follow-up echocardiograms at our institution and were included. Neo-aortic dimensions were converted to z-scores and modeled over time. Kaplan-Meier analysis was used to assess freedom from neo-aortic outcomes, and predictors were identified through multivariate analysis.

RESULTS

Median age at Ross was 9 years (range 3 days to 34 years). Over 4.7 years (range 3 months to 9.3 years) follow-up, there was disproportionate enlargement of the neo-aortic root (z-score increase of 0.75/year [p < 0.0001]). Neo-AI progressed > or =1 grade in 36% of patients and > or =2 grades in 15%. Nine patients (12%) had neo-aortic reintervention at 2.0 years (range 1.1 to 9.5 years) after the Ross procedure owing to severe neo-AI (n = 7), neo-aortic root dilation (n = 1), and neo-aortic pseudoaneurysm (n = 1). At 6 years after the Ross procedure, freedom from neo-aortic reintervention was 88%. Freedom from neo-aortic root z-score >4 was only 3% and from moderate or greater neo-AI was 60%. Longer follow-up time was associated with neo-aortic root dilation (p < 0.0001). Prior ventricular septal defect (VSD) repair predicted neo-AI (p = 0.02) and reintervention (p = 0.03). Prior aortic valve replacement (p = 0.002) also predicted neo-AI. Neo-aortic root dilation was not associated with neo-AI or reintervention.

CONCLUSIONS

At mid-term follow-up after the Ross procedure, neo-aortic root size increases significantly out of proportion to somatic growth, and neo-AI is progressive. Prior VSD repair and aortic valve replacement were associated with neo-AI and reintervention.

Midterm outcomes and predictors of reintervention after the Ross procedure in infants, children, and young adults

OBJECTIVES

This study assessed the type, time course, and risk factors for right and left ventricular outflow tract reinterventions after the Ross procedure in a population of infants, children, and young adults.

METHODS

Patients who underwent the Ross procedure between January 1995 and June 2004 were included (n = 121 consecutive patients). Kaplan-Meier and hazard analyses of right and left ventricular outflow tract reinterventions were performed, and predictors of reintervention were identified through multivariate analysis.

RESULTS

The median age at the Ross procedure was 8.2 years (4 days to 34 years); 20% were aged less than 1 year. Half of the patients had isolated aortic valve disease; the other half had complex left-sided heart disease. Early mortality (<30 days) was 2.5% (n = 3). There were 2 late deaths (1.7%). Follow-up (median 6.5 years [2.5 months to 10.4 years]) was available for 96% of survivors (n = 111). Right ventricular outflow tract reintervention (n = 22 in 15 patients) was performed 2.0 years (2.0 weeks to 9.8 years) after the Ross procedure because of stenosis in 19 of 22 cases. Freedom from right ventricular outflow tract reintervention at 8 years was 81%. Smaller homograft size was the strongest predictor (P < .001) of right ventricular outflow tract reintervention. Left ventricular outflow tract reintervention (n = 15 in 15 patients) was performed 2.8 years (1.0 months to 11.6 years) after the Ross procedure because of severe neoaortic insufficiency in 10 of 15 patients. Freedom from left ventricular outflow tract reintervention at 8 years was 83%. Native pulmonary valve abnormalities (P < .01), original diagnosis of aortic insufficiency (P < .01), prior aortic valve replacement (P = .01), and prior ventricular septal defect repair (P = .04) predicted left ventricular outflow tract reintervention.

CONCLUSIONS

At midterm follow-up after the Ross procedure, interim mortality is rare. Neoaortic insufficiency and right ventricle to pulmonary artery conduit obstruction are common postoperative sequelae, requiring reintervention in one quarter of patients.

Exercise performance in children and adolescents after the Ross procedure

OBJECTIVES

The Ross procedure is increasingly utilized in the treatment of aortic valvar disease in children and adolescents. Our purpose was to compare pre- and post-operative exercise state in this population.

METHODS

We included patients who underwent the Ross procedure at our institution between January, 1995, and December, 2003, and in whom we had performed pre- and post-operative exercise stress tests. We used a ramp bicycle protocol to measure consumption of oxygen and production of carbon dioxide. Cardiac output was estimated from effective pulmonary blood flow by the helium acetylene re-breathing technique.

RESULTS

We studied 26 patients, having a median age at surgery of 15.7 years, with a range from 7.5 to 24.1 years. The primary indication for surgery in two-thirds was combined aortic stenosis and insufficiency. Median time from the operation to the post-operative exercise stress test was 17.4 months, with a range from 6.7 to 30.2 months. There was a trend toward lower maximal consumption of oxygen after the procedure, at 36.3 plus or minus 7.6 millilitres per kilogram per minute (83.9% predicted) as opposed to 38.6 plus or minus 8.4 millilitres per kilogram per minute (88.5% predicted, p equal to 0.06). Patients after the procedure, however, had significantly increased adiposity, so that there was no difference in maximal consumption of oxygen indexed to ideal body weight before and after the operation. In 20 of the patients, aerobic capacity improved or was stable after the operation. There was no post-operative chronotropic impairment.

CONCLUSIONS

In the majority of patients following the Ross procedure, exercise performance is stable and within the normal range of a healthy age and sex matched population, despite sedentary lifestyles and increased adiposity.

Effect of cardiac rehabilitation on functional outcomes after coronary revascularization

BACKGROUND

Current guidelines recommending cardiac rehabilitation (CR) after coronary revascularization are largely based on early studies that evaluated only a subset of the population and failed to assess the impact of CR on a patient's perception of their functional status. The main objective of this study was to evaluate the impact of CR in a diverse contemporary population on patient functional outcomes.

METHODS

We studied the effect of CR on 6-month SF-36 Physical Functioning (PF) in 700 patients (mean age 67 +/- 11 years, 37% women) who underwent coronary bypass grafting or percutaneous intervention from August 1998 to July 2000.

RESULTS

Overall CR participation was 24%. At baseline, CR participants had higher PF (mean 62.5 vs 52.5, P <.001). After adjusting for baseline clinical variables and PF score, CR was associated with significant improvement in 6-month PF (+5.0, 95% CI 1.0-9.0). This improvement was observed in all patient subgroups, but tended to be greater in magnitude in men versus women, patients aged <70 years versus > or =70 years, and patients with coronary bypass grafting versus patients with percutaneous intervention. CR participants also tended to be more likely to engage in regular exercise (63% vs 55%, P =.06) and modify their diet (82% vs 73%, P =.07). Rates of rehospitalization and repeat revascularization were similar among CR participants and nonparticipants.

CONCLUSIONS

CR after coronary revascularization is associated with improved functional outcomes and adoption of secondary preventive measures. Innovative strategies to facilitate CR enrollment and tailoring programs to better address the needs of all patient subgroups would extend these benefits to more eligible patients.

Coronary artery pattern and outcome of arterial switch operation for transposition of the great arteries: a meta-analysis

BACKGROUND

Prior studies of coronary pattern and outcome after arterial switch operation (ASO) for transposition of the great arteries (TGA) have been hindered by limited statistical power. This meta-analysis assesses the effect of coronary anatomy on post-ASO mortality, both overall and adjusted for time.

METHODS AND RESULTS

A literature search revealed 9 independent series that reported post-ASO mortality by coronary pattern in a total of 1942 patients. Odds ratios comparing all-cause mortality in patients with usual versus variant coronary patterns were calculated and combined by use of an empirical Bayesian model. Single coronary patterns, both of which loop around the great vessels, were associated with significant mortality (OR 2.9, 95% CI 1.3 to 6.8), whereas looping patterns that arose from 2 separate ostia were not (OR 1.2, 95% CI 0.8 to 1.9). This latter group includes patients with the most common variant, circumflex from right coronary artery. Patients with an intramural coronary artery had the greatest mortality (OR 6.5, 95% CI 2.9 to 14.2). Overall, patients with any variant coronary pattern had nearly twice the mortality seen in those with the usual pattern (OR 1.7, 95% CI 1.3 to 2.4). Single ostium patterns and intramural coronary arteries remained associated with significant added mortality after adjustment for time-trend effects.

CONCLUSIONS

Over the past 2 decades, patients with common coronary variants have undergone ASO without added mortality compared with those with the usual coronary pattern. Those with intramural or single coronary arteries have significant added mortality that has persisted over time.

Oral antihypertensive trial design and analysis under the pediatric exclusivity provision

BACKGROUND

The Best Pharmaceuticals for Children Act provides a 6-year extension to the economic incentives offered to drug manufacturers under the Pediatric Exclusivity Provision, for providing requested information on drugs used in children, which includes >50 oral antihypertensive medications. Guidelines were published outlining specific requirements for the design and analysis of trials to provide the requested information.

METHODS

We review the design and analysis requirements, along with recruitment and eligibility guidelines, for dose-ranging studies of oral antihypertensives in children in light of ethical and methodologic issues unique to pediatric research. We also discuss examples of trials conducted to date and the implications and limitations of legislative efforts.

RESULTS

Four possible trial types are outlined in the guidelines. Trial C, which uses a randomized withdrawal phase after treatment, has been used most often. Avoidance of a true placebo arm may enhance patient recruitment and minimize ethical concerns at the expense of a more complicated design and analysis. In addition, this trial involves little risk for manufacturers because patent extension does not depend on the outcome of the trial.

CONCLUSIONS

Studies being conducted under the Pediatric Exclusivity Provision will provide valuable information concerning dosing and efficacy for several antihypertensive medications used in children. New legislation may stimulate study of drugs without remaining patent life, but data on safety, long-term outcomes, and the youngest pediatric age groups are also needed for a full understanding of all issues pertinent to pediatric use.

Cardiac rehabilitation in the elderly

BACKGROUND

Although patients >/=65 years old account for the majority of cardiac admissions and procedures in the United States, studies of cardiac rehabilitation have traditionally focused on younger patients. Only recently has the effectiveness of cardiac rehabilitation in the elderly population begun to receive more attention.

METHODS

We present a comprehensive literature review of studies that have looked specifically at the effectiveness of cardiac rehabilitation in the elderly. We discuss the methodologic limitations of studies to date, compare outcomes among elderly rehabilitation patients with those of younger patients, and examine barriers to participation among the elderly.

RESULTS

The majority of studies published to date have been small observational case series. Despite these limitations, these studies generally show consistent improvements in exercise capacity, cardiac risk factors, and quality-of-life parameters in elderly cardiac rehabilitation patients. These benefits appear to be similar to those seen in younger patients. In spite of this, participation rates among the elderly are low, primarily because of less aggressive referral.

CONCLUSIONS

Although further studies are necessary, the current literature shows that cardiac rehabilitation is associated with improved outcomes after a cardiac event, regardless of age. However, innovative recommendation and referral strategies are needed because few elderly patients actually enroll.

Representation of elderly persons and women in published randomized trials of acute coronary syndromes

CONTEXT

Elderly persons and women were underrepresented in randomized controlled trials (RCTs) prior to 1990. Since then, efforts have been made to correct these biases, but their effect is unclear.

OBJECTIVE

To determine whether the percentage of elderly persons and women in published clinical trials of acute coronary syndromes has increased and how this enrollment compared with disease prevalence.

DATA SOURCES

The MEDLINE and Cochrane databases were searched for English-language articles from January 1966 to March 2000 regarding myocardial infarction, unstable angina, or acute coronary syndromes. Additional data sources included meta-analyses, review articles, and cardiology textbooks. Estimates of community-based myocardial infarction rates came from the National Registry of Myocardial Infarction and the Worcester Heart Study.

STUDY SELECTION

Published RCTs of acute coronary syndrome patients were included and trials enrolling 50 patients or fewer, those without clinical end points, papers published in a language other than English, and unpublished manuscripts were excluded. Of 7645 studies identified, 593 RCTs were selected for review.

DATA EXTRACTION

The RCTs were abstracted by 2 of the authors for year of publication, source of support (ie, funding), pharmacotherapy, study phase, number of study sites, trial location, number of patients, mean age of the study population, and any age exclusion criteria for enrollment.

DATA SYNTHESIS

The number of published RCTs with explicit age exclusions has declined from 58% during 1966-1990 to 40% during 1991-2000. Trial enrollment of patients aged 75 years or older increased from 2% for studies published during 1966-1990 to 9% during 1991-2000, but remains well below their representation among all patients with myocardial infarction (37%) in the United States. Enrollment of women has risen from 20% for studies published between 1966-1990 to 25% during 1991-2000, but remains well below their proportion of all patients with myocardial infarction (43%) in the United States.

CONCLUSIONS

Attempts at making cardiovascular RCTs more inclusive appear to have had limited success; thus, women and elderly persons remain underrepresented in published trial literature relative to their disease prevalence. Because safety and efficacy can vary as a function of sex and age, these enrollment biases undermine efforts to provide evidence-based care to all cardiac patients.

Regulation of netrin-1a expression by hedgehog proteins

Netrins, a family of growth cone guidance molecules, are expressed both in the ventral neural tube and in subsets of mesodermal cells. In an effort to better understand the regulation of netrins, we examined the expression of netrin-1a in mutant cyclops, no tail, and floating head zebrafish embryos, in which axial midline structures are perturbed. Netrin-1a expression requires signals present in notochord and floor plate cells. In the myotome, but not the neural tube, netrin-1a expression requires sonic hedgehog. In embryos lacking sonic hedgehog, the sonic-you locus, netrin-1a expression is reduced or absent in the myotomes but present in the neural tube. Embryos lacking sonic hedgehog express tiggy-winkle hedgehog in the floor plate, suggesting that, in the neural tube, tiggy-winkle hedgehog can compensate for the lack of sonic hedgehog in inducing netrin-1a expression. Ectopic expression of sonic hedgehog, tiggy-winkle hedgehog, or echidna hedgehog induces ectopic netrin-1a expression in the neural tube, and ectopic expression of sonic hedgehog or tiggy-winkle hedgehog, but not echidna hedgehog, induces ectopic netrin-1a expression in somites. These data demonstrate that in vertebrates netrin expression is regulated by Hedgehog signaling.