Jason N. Johnson

Cumulative Radiation Exposure and Cancer Risk Estimation in Children With Heart Disease

Background— Children with heart disease are frequently exposed to imaging examinations that use ionizing radiation. Although radiation exposure is potentially carcinogenic, there are limited data on cumulative exposure and the associated cancer risk. We evaluated the cumulative effective dose of radiation from all radiation examinations to estimate the lifetime attributable risk of cancer in children with heart disease. Methods and Results— Children ⩽6 years of age who had previously undergone 1 of 7 primary surgical procedures for heart disease at a single institution between 2005 and 2010 were eligible for the study. Exposure to radiation-producing examinations was tabulated, and cumulative effective dose was calculated in millisieverts. These data were used to estimate lifetime attributable risk of cancer above baseline using the approach of the Committee on Biological Effects of Ionizing Radiation VII. The cohort included 337 children exposed to 13 932 radiation examinations. Conventional radiographs represented 92% of examinations, whereas cardiac catheterization and computed tomography accounted for 81% of cumulative exposure. Overall median cumulative effective dose was 2.7 mSv (range, 0.1–76.9 mSv), and the associated lifetime attributable risk of cancer was 0.07% (range, 0.001%–6.5%). Median lifetime attributable risk of cancer ranged widely depending on surgical complexity (0.006%–1.6% for the 7 surgical cohorts) and was twice as high in females per unit exposure (0.04% versus 0.02% per 1-mSv effective dose for females versus males, respectively; P<0.001). Conclusions— Overall radiation exposures in children with heart disease are relatively low; however, select cohorts receive significant exposure. Cancer risk estimation highlights the need to limit radiation dose, particularly for high-exposure modalities.

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.

Radiation Protocol for Three‐Dimensional Rotational Angiography to Limit Procedural Radiation Exposure in the Pediatric Cardiac Catheterization Lab

BACKGROUND Three-dimensional rotational angiography (3DRA) offers more detailed anatomic information than 2D digital acquisition (2DDA). Concerns over potentially higher contrast and radiation doses have limited its routine use. OBJECTIVE The primary objective of this study was to compare radiation doses required to obtain 3DRA using a customized low dose radiation protocol with 2DDA. The secondary objective was to compare total procedural radiation in pediatric cardiac catheterization procedures utilizing 3DRA to those that do not. STUDY DESIGN Phantom studies were conducted to establish customized 3DRA protocols for radiation reduction. Comparison of 3DRA and non-3DRA procedures in age-, size- and diagnosis-matched controls was performed. Radiation doses were indexed to body surface area (BSA) to account for differing body habitus as validated from the phantom study. RESULTS Study (n = 100) and control (n = 100) groups were matched for age (10.2 vs. 9.98 years; P = .239) and BSA (1.23 vs. 1.09 m2 ; P = .103). The dose area product (DAP) to acquire a 3DRA was similar to a 5 s, 15 frames/second 2DDA (278 vs. 241 cGy/cm2 ; P = .14). Despite the 3DRA group consisting of more complex interventions, no difference was found in the total procedural Air Kerma and DAP indexed to BSA (244 vs. 249 mGy/m2 ; P = .79 and 3348 vs. 3176 cGy/cm2 /m2 ; P = .48, respectively). The contrast volume to acquire a 3DRA compared to a 2DDA was greater (1.59 vs. 1.01 mL/kg; P < .001). However, no difference was found for the entire procedure (3.8 vs. 4 mL/kg, P = .494). This could have resulted from the need to obtain multiple 2DDAs to achieve the detail of a single 3DRA (11 vs. 7 per study; P < .001). CONCLUSIONS When 3DRA, using the proposed protocols is employed, total procedural contrast and radiation doses are comparable with the sole use of biplane cine-angiograms. These protocols may allow for routine use of 3DRA for congenital cardiac catheterizations.

Right ventricular function after repair of tetralogy of Fallot: a comparison between bovine pericardium and porcine small intestinal extracellular matrix

BACKGROUND The porcine small intestinal extracellular matrix reportedly has the potential to differentiate into viable myocardial cells. When used in tetralogy of Fallot repair, it may improve right ventricular function. We evaluated right ventricular function after repair of tetralogy of Fallot with extracellular matrix versus bovine pericardium. METHOD Subjects with non-transannular repair of tetralogy of Fallot with at least 1 year of follow-up were selected. The extracellular matrix and bovine pericardium groups were compared. We used three-dimensional right ventricular ejection fraction, right ventricle global longitudinal strain, and tricuspid annular plane systolic excursion to assess right ventricular function. RESULTS The extracellular matrix group had 11 patients, whereas the bovine pericardium group had 10 patients. No differences between the groups were found regarding sex ratio, age at surgery, and cardiopulmonary bypass time. The follow-up period was 28±12.6 months in the extracellular matrix group and 50.05±17.6 months in the bovine pericardium group (p=0.001). The mean three-dimensional right ventricular ejection fraction (55.7±5.0% versus 55.3±5.2%, p=0.73), right ventricular global longitudinal strain (-18.5±3.0% versus -18.0±2.2%, p=0.44), and tricuspid annular plane systolic excursions (1.59±0.16 versus 1.59±0.2, p=0.93) were similar in the extracellular matrix group and in the bovine pericardium group, respectively. Right ventricular global longitudinal strain in healthy children is reported at -29±3% in literature. CONCLUSION In a small cohort of the patients undergoing non-transannular repair of tetralogy of Fallot, there was no significant difference in right ventricular function between groups having extracellular matrix versus bovine pericardium patches followed-up for more than 1 year. Lower right ventricular longitudinal strain noted in both the groups compared to healthy children.

Corynebacterium endocarditis of a percutaneously placed transcatheter pulmonary valve

We report a case of endocarditis of a transcatheter pulmonary valve-in-valve in a 14-year-old boy with tetralogy of Fallot. He presented with recurrent low-grade fevers, lethargy, and anorexia. Multiple blood cultures grew a gram-positive rod, Corynebacterium pseudodiphtheriticum. He was taken to the operating room for removal of the vegetative endocarditis and pulmonary valve replacement.

Use of 3-D digital subtraction rotational angiography during cardiac catheterization of infants and adults with congenital heart diseases

To compare image quality, radiation and contrast doses required to obtain 3D‐Digital subtraction rotational angiography (3D‐DSRA) with 3D‐Digital rotational angiography (3D‐DRA) in infants (children ≤ 2 years of age) and adults with congenital heart diseases (ACHD).

Aortic Root Size by Echocardiogram Compared With Computed Tomography in Adolescents With Pectus Excavatum.

Purpose: Aortic root dilation is a risk factor for aneurysm and dissection. Echocardiography (echo) is the most frequently used initial screening method for the aortic root, but computed tomography (CT) is a preferred modality because of the ability to reformat the images and obtain measurements without the technical limits of echo image acquisition. There are limited data comparing the 2 modalities in measuring the aortic root. Materials and Methods: This was a retrospective cohort study comparing echo with CT in measuring the aortic root and was conducted at a children’s hospital. Forty adolescents (range, 10 to 18 y) with pectus excavatum were evaluated. Results: In the majority of patients (68%), echo underestimated the aortic root size compared with the CT measurement by at least 1 SD. The average difference between the 2 modalities was 2.5 mm. There was a trend for a greater difference between modalities as the aortic root increased. The severity of the deformity by Haller index did not correlate with greater underestimation of the aortic root size. The shape of the aortic root, ranging from circular to ovoid, also did not contribute to the underestimation of aortic root size by echo. Conclusions: Echo can be used as a screening method for the aortic root, but it can underestimate the aortic root size when compared with CT measurements in pediatric patients with pectus excavatum. This difference was more profound as the diameter of the aortic root increased. Patients with dilated aortic roots on echocardiogram may benefit from biorthogonal measurements offered by other imaging modalities such as CT or magnetic resonance imaging.

Case 2: Acute-Onset Tachypnea, Tachycardia, and Reduced Activity in a 16-Month-Old Girl

1. Michael Perez, MD* 2. T. K. Susheel Kumar, MD* 3. Mayte Figueroa, MD* 4. Jason Johnson, MD* 5. Mohammed Ali Absi, MD* 1. *Department of Pediatric Cardiology and Cardiothoracic Surgery, Le Bonheur Children’s Hospital, University of Tennessee, Memphis, TN. A 16-month-old girl presents to the emergency department with rapid breathing, fatigue, malaise, and drastically diminished activity level of 1-day duration. She has had persistent nasal congestion for the past 2 weeks without fever, cough, or wheezing. She most recently has begun to experience repeated episodes of emesis. The emesis is nonbilious and without blood. Despite persistent emesis, she has managed to keep up with her fluid losses and has normal urine output. She has a history of bilateral hydronephrosis with no other significant medical or family history. On physical examination, her height is 81 cm (75th percentile), weight is 9.9 kg (25th percentile), and head circumference is 45 cm (25th percentile). She has a heart rate of approximately 200 beats per minute, a respiratory rate of 40 breaths per minute, blood pressure of 140/90 mm Hg in her upper extremities and 152/101 mmHg in her lower extremities, temperature of 100.6°F (38.1°C), and oxygen saturation of 99%. She is lethargic, and her radial and femoral pulses are equal, rapid, and thready. She has no murmurs, rubs, or gallops but has crackles (rales) in bilateral posterior lung fields with fair air exchange and no wheezing. Her abdomen is soft without distention or hepatomegaly, and she has no peripheral edema. Electrocardiography reveals sinus tachycardia with slight ST elevation in leads 1 and 2, whereas chest radiography reveals cardiomegaly and bilateral interstitial markings. The results of her initial laboratory …

Response to Letters Regarding Article, “Cumulative Radiation Exposure and Cancer Risk Estimation in Children With Heart Disease”

We thank Harbron, Glatz et al, and Bardo for their compliments and critiques. It is important for our patients that we apply rigorous methods of analysis to identify risks associated with ionizing radiation. All of the cohort studies that predict morbidity decades after exposure have limitations, and our study was no exception. In our article we highlighted many of these limitations.1 We agree with Harbron that organ-specific cancer risk estimates are more reliable than estimates derived from effective dose. We used effective dose for several reasons: (1) although effective dose is not intended for risk estimates, Smith-Bindman et al2 demonstrated reasonable correlation with organ-specific estimates and, in our initial assessment of catheterization organ doses, we reached a similar conclusion; (2) we did not have organ doses for the majority of imaging modalities evaluated and chose to use a consistent methodology across modalities; and (3) despite limitations, effective dose is a better …