Magnetic resonance phase-shift velocity mapping in pediatric patients with pulmonary venous obstruction.

OBJECTIVES: This study evaluated the accuracy, advantages and clinical efficacy of magnetic resonance (MR) phase-shift velocity mapping, in delineating the site and the hemodynamic severity of pulmonary venous (PV) obstruction in patients with congenital heart disease (CHD). BACKGROUND: Magnetic resonance phase-shift velocity mapping of normal pulmonary veins and of obstructed PV pathways have been previously reported in a mainly adult population. METHODS: The study population (33 pts) underwent MR phase-shift velocity mapping of their PV pathways. These results were compared with cardiac catheterization and Doppler echocardiography data. RESULTS: The study population (0.4 to 19.5 years) consisted of a study group (PV pathway obstruction, n = 7) and a control group (no PV obstruction, n = 26). No patients had any left-to-right shunt lesions. The MR imaging displayed precise anatomical detail of the pulmonary veins. Phase velocities in the control group ranged from 20 to 71 cm/s, whereas velocities in the study group ranged from 100 to 250 cm/s (p = 0.002). The MR phase velocities (154 +/- 0.53 cm/s) compared favorably with Doppler echocardiography (147 +/- 0.54 cm/s), (r = 0.76; p = 0.05). The MR velocity mapping was 100% specific and 100% sensitive in detecting PV obstruction, although the absolute gradient measurements among MR phase mapping, echocardiographic Doppler and catheterization did not show statistically significant correlation. CONCLUSIONS: In the absence of any associated left-to-right shunt lesions, PV velocities of 100 cm/s and greater indicated significant obstruction. The MR phase-shift velocity mapping, together with MR spin echocardiography and MR angiography, provides comprehensive anatomic and physiologic data that may obviate the need for further invasive studies.

Improved measurement of pressure gradients in aortic coarctation by magnetic resonance imaging.

OBJECTIVES: This study evaluated whether magnetic resonance imaging (MRI) and magnetic resonance (MR) phase velocity mapping could provide accurate estimates of stenosis severity and pressure gradients in aortic coarctation. BACKGROUND: Clinical management of aortic coarctation requires determination of lesion location and severity and quantification of the pressure gradient across the constricted area. METHODS: Using a series of anatomically accurate models of aortic coarctation, the laboratory portion of this study found that the loss coefficient (K), commonly taken to be 4.0 in the simplified Bernoulli equation delta P = KV2, was a function of stenosis severity. The values of the loss coefficient ranged from 2.8 for a 50% stenosis to 4.9 for a 90% stenosis. Magnetic resonance imaging and MR phase velocity mapping were then used to determine coarctation severity and pressure gradient in 32 patients. RESULTS: Application of the new severity-dependent loss coefficients found that pressure gradients deviated from 1 to 17 mm Hg compared with calculations made with the commonly used value of 4.0. Comparison of MR estimates of pressure gradient with Doppler ultrasound estimates (in 22 of 32 patients) and with catheter pressure measurements (in 6 of 32 patients) supports the conclusion that the severity-based loss coefficient provides improved estimates of pressure gradients. CONCLUSIONS: This study suggests that MRI could be used as a complete diagnostic tool for accurate evaluation of aortic coarctation, by determining stenosis location and severity and by accurately estimating pressure gradients.

Incidence of aneurysm formation after Dacron patch aortoplasty repair for coarctation of the aorta: long-term results and assessment utilizing magnetic resonance angiography with three-dimensional surface rendering.

OBJECTIVES: Magnetic resonance angiography with three-dimensional surface rendering was performed to determine its value in assessing anatomic detail in patients with suspected aortic aneurysms. BACKGROUND: Dacron patch aortoplasty repair of coarctation of the aorta carries an inherent risk of aneurysm development. Sudden death from aortic rupture prompted discontinuing this operation and evaluating 39 patients (16 girls; mean age 6.3 years, range 10 days to 14.5 years) undergoing repair between January 1976 and October 1987. The aorta ruptured in 10 patients; 6 died at a mean interval of 8.1 years (range 0.75 to 12.4) after repair. All 33 survivors were interviewed and examined. METHODS: Conventional magnetic resonance imaging was performed in 26 patients, magnetic resonance angiography in 18. Angiographic slices were used to reconstruct three-dimensional images. No catheterization or contrast angiography was performed. Surgical intervention was based on clinical findings and magnetic resonance images. RESULTS: Twenty patients (11 girls) developed aneurysms, of which nine were detected in patients studied by magnetic resonance. Ruptures occurred in eight female patients, three of whom were pregnant. Surface renderings accurately defined aortic anatomy or aneurysms in all patients. On follow-up, no aneurysms have been detected in patients with negative magnetic resonance study results. Precise anatomic correlation with operative findings was reported. CONCLUSIONS: Magnetic resonance angiography with three-dimensional surface rendering provides noninvasive, radiation-free and contrast agent-free high resolution images of the thoracic aorta. These images can be reviewed and have three-dimensional form and perspective. These techniques were preferred over invasive angiography by surgeons and clinicians as definitive, risk-free procedures before surgical intervention.

Saphenous vein homograft: a superior conduit for the systemic arterial shunt in the Norwood operation.

BACKGROUND: Excessive pulmonary blood flow increases ventricular volume work in the face of inadequate systemic cardiac output, low diastolic blood pressure, and inadequate coronary perfusion. Using the smallest available 3-mm polytetrafluoroethylene shunts have been successful, although catastrophic shunt thrombosis has occasionally been observed. To avoid thrombosis with a smaller conduit, saphenous vein homografts (SVG) were used to construct the modified Blalock-Taussig (BT) shunts. METHODS: From January 1998 to April 1999, 25 patients weighing 3.1 kg (3.0 kg or less, n = 9), at a mean age of 8.9 days, underwent stage I Norwood using an SVG BT shunt. Common heart defects were aortic atresia (n = 8), mitral atresia and double-outlet right ventricle (n = 5), and unbalanced AVC (n = 5). Mean BT shunt size was 3.2 mm, with 12 patients having shunts that were 3 mm or smaller. RESULTS: Thirty-day hospital mortality was 8% (2 of 25). No shunt thrombosis was seen, despite banding the BT shunt in 3 patients. One patient had BT revision because of an anatomic issue not directly related to the shunt material. CONCLUSIONS: Excellent results may be achieved using SVG BT shunts in the Norwood operation. This conduit seems less likely to thrombose, both acutely and chronically, allowing the use of appropriately smaller-sized shunts in small neonates.

Three-dimensional echocardiographic measurement of right ventricular volume in children with congenital heart disease validated by magnetic resonance imaging.

Measurement of right ventricular volume and function by two-dimensional echocardiography is unreliable because of the asymmetric shape of the right ventricle. The purpose of this study was to validate the accuracy of transthoracic three-dimensional echocardiography in assessing right ventricular volumes in children with congenital heart disease after surgical repair of the defects, by comparison with those measured by magnetic resonance imaging. We examined 13 children after repair of tetralogy of Fallot (10), hypoplastic left heart syndrome (2), or atrial septal defect (1). Each underwent magnetic resonance imaging followed by three-dimensional echocardiography done with a transthoracic 5 MHz, prototype internally rotating omniplane transducer. In both methods, endocardial borders were manually traced and volumetric slices were summated. Close correlation was observed between the two methods (R2 0.91 for end-systolic volumes, 0.90 for end-diastolic volumes, 0.64 for ejection fraction, and 0.92 for interobserver variability). A limits-of-agreement analysis showed no adverse trend between the two methods under values of 100 ml and low variation around the mean values. We conclude that three-dimensional echocardiography measurement of right ventricular volumes correlates closely with magnetic resonance imaging in children with operated congenital heart disease and may allow accurate serial evaluation in these patients.

Malaria control in central Malaita, Solomon Islands. 1. The use of insecticide-impregnated bed nets.

The present study investigated the use of insecticide-impregnated bed nets by communities in central Malaita, Solomon Islands. Qualitative and quantitative data were collected by: (1) questionnaire administration to 124 care-givers of children aged 0-10 years of age; (2) 20 focus group discussions; (3) two structured observations of bed net re-impregnation, and (4) interviews with key informants. Ninety-four percent of all care-givers had bed nets, but only 62% had sufficient bed nets for all household members. Fifty-two percent used bed nets throughout the year and 70% of care-givers reported that all their children slept under bed nets. Although coastal householders considered malaria and mosquitoes more of a problem than inland householders, overall bed net compliance did not differ. Factors affecting bed net ownership were cost and community expectation of free bed nets. Bed net use was affected by four factors: (1) seasonality (99% used bed nets during the rainy season, 52% used them all year); (2) mosquito nuisance (59% of respondents reported that protection against mosquitoes was the main reason for using a bed net); (3) weather (68% of care-givers would not use a bed net if the weather was hot), and (4) low density of mosquitoes (respondents who used bed nets as protection against mosquito nuisance were more likely not to use bed nets when mosquitoes were few than those who used bed nets for malaria protection (odds ratio (OR), 3.9; 95% confidence interval (CI), 1.4-12.0). Protection against malaria was the main reason children slept under bed nets. Children from households where bed nets were used for malaria protection were more likely to sleep under bed nets than children from households where nets were used as protection from mosquitoes only (OR, 2.7; 95% CI, 1.3-5.9). Other factors that affected children's bed net use were, age (users were significantly younger than non-users; chi(2)=7.9, degrees of freedom=1, P=0.005) and sufficiency of bed nets (OR, 2.0; 95% CI, 1. 3-7.0).

Malaria control in central Malaita, Solomon Islands 2. Local perceptions of the disease and practices for its treatment and prevention.

Government health policy for malaria control in Solomon Islands has three main objectives: (1) early diagnosis and treatment of malaria at a health service; (2) reduction of human-vector contact through widespread use of insecticide-impregnated bed nets; and (3) provision of malaria chemoprophylaxis for pregnant women. Social research was carried out in thirteen villages in central Malaita to determine local attitudes toward malaria and to estimate the level of participation in malaria control activities. Interviews with 124 care-givers who had children 0-10 years of age, 20 focus group discussions and four evening structured observations were research methods used. Antimalarial drugs were the most favoured treatment, and use of traditional medicines and healers were reportedly minimal. Twenty-five percent of respondents reported keeping chloroquine at home and 42% said they would use chloroquine before seeking diagnosis and treatment from a health service. Structured observations suggest that protection against mosquitoes is poor during the evening. Fifty-two percent of respondents reported using fire and 32% said they used bed nets to protect themselves from mosquitoes. Participants had contradictory beliefs on the threat of malaria during pregnancy and the safety of taking chloroquine prophylaxis. Implications of malaria treatment and prevention practices are discussed, and recommendations for improving malaria control are presented.

Three-dimensional magnetic resonance imaging evaluation of pediatric tracheobronchial tree.

Magnetic resonance imaging (MRI) of the airway has recently emerged as a diagnostic tool for evaluating tracheobronchial obstruction in pediatric patients. Computer-assisted reconstructions of transaxial images have enabled three-dimensional reconstructions of the airway to be manipulated in any plane and visualized in relation to adjacent anatomical structures. Eight patients in whom magnetic resonance imaging was used to diagnose a variety of airway obstructive lesions are presented. A protocol for the evaluation of pediatric tracheobronchial obstruction is presented, with the role of three dimensionally reconstructed MR imaging emphasized.

Electrocardiographic predictors of right ventricular volume measured by magnetic resonance imaging late after total repair of tetralogy of Fallot.

BACKGROUND: Right ventricular dysfunction occurs in many patients with significant pulmonary valve regurgitation late after initial total repair of tetralogy of Fallot. Methods to predict which of these patients are at increased risk of late morbidity and mortality are not yet known. HYPOTHESIS: This study evaluated electrocardiographic (ECG) predictors of severe right ventricular dilatation determined by magnetic resonance imaging (MRI) volumes in patients with tetralogy of Fallot late after initial corrective repair. METHODS: We retrospectively reviewed the ECGs and MRI right ventricular volume measurements of 20 patients (age 4.4 to 19.3 years, mean 10.0 years) with significant pulmonary valve regurgitation late after repair of tetralogy of Fallot. All patients had enlarged, hypokinetic right ventricles by echocardiography. The patients were grouped based on an indexed right ventricular end-diastolic volume (RVEDV/BSA) of < 102 ml/m2 (Group 1) or > or = 102 ml/m2 (Group 2). We determined the sensitivity, specificity, positive and negative predictive values of QRS duration, and mean frontal plane QRS axis for predicting right ventricular volumes. RESULTS: A maximal QRS duration of > or = 150 ms or a northwest quadrant frontal plane QRS axis had 85% sensitivity, 86% specificity, 92% positive predictive value, and 75% negative predictive value for predicting an RVEDV/BSA of > or = 102 ml/m2. The mean QRS duration was significantly longer in Group 2 than in Group 1 patients (156 ms vs. 125 ms, p = 0.005). CONCLUSIONS: In patients late after repair of tetralogy of Fallot with significant pulmonary valve regurgitation a maximal manually measured QRS duration of > or = 150 ms and/or a frontal plane QRS northwest quadrant axis can predict patients with marked right ventricular enlargement. The presence of either of these findings on the ECG signifies patients who require further evaluation and consideration for pulmonary valve replacement.

Hemodynamic and electrocardiographic effects of early pulmonary valve replacement in pediatric patients after transannular complete repair of tetralogy of Fallot.

In adults, pulmonary value replacement (PVR) shows improvement in right ventricular (RV) volume and function and reduces QRS duration. In addition, RV volume correlates with QRS duration and QRS change. This has not been shown in pediatric patients. The purpose of this study was to evaluate serial magnetic resonance imaging (MRI) and electrocardiogram measurements before and after early PVR in a pediatric population with repaired Tetralogy of Fallot and whether QRS duration and QRS change correlated with RV volume. A retrospective review of MRIs and electrocardiograms was conducted on 10 patients. Median age at repair was 2.1 +/- 0.7 years, and median age at PVR was 11.5 +/- 2.0 years. There were significant decreases in RV end diastolic volume (EDV)/body surface area (BSA) (p < 0.0004), end systolic volume (ESV)/BSA (p = 0.02), RVEDV/left ventricular (LV) EDV (p < 0.001), RV ejection fraction (p < 0.04), RV stroke volume (SV)/BSA (p < 0.0002), and (RVSV - LVSV)/BSA (p = 0.0007). No significant change in QRS duration occurred (p = 0.08). QRS duration (pre-r = 0.44, p = 0.20; post-r = 0.34, p = 0.33) and QRS change (r = -0.08, p = 0.83) did not correlate with RVEDV. We propose early consideration of PVR in pediatric patients. PVR improves RV volumes and function and may provide beneficial electromechanical effects by slowing the progression of QRS duration.

Right atrial diverticulum presenting as Wolff-Parkinson-White syndrome.

A 7-year-old male presenting with Wolff-Parkinson-White syndrome and tachycardia was suspected by echocardiographic and magnetic resonance imaging evaluation to have an associated pericardial cyst anterior to the right atrium and ventricle. Electrophysiological evaluation demonstrated short antegrade and retrograde accessory connection refractory periods, with inducible orthodromic atrioventricular reentrant tachycardia. Surgical observation revealed a rare congenital right atrial diverticulum bridging the anterior right atrioventricular groove, with the functional accessory connection lateralized to the medial aspect of this structure. Endocardial and epicardial incisions and cryolesions placed along the anterior right atrioventricular groove initially appeared successful, but preexcitation recurred within 4 weeks postoperatively.

MR imaging of the pediatric airway.

The mainstays of initial evaluation of the airway in infants and children are chest radiography and esophagography. Magnetic resonance (MR) imaging is frequently used next to diagnose specific abnormalities and obviates angiocardiography. MR imaging usually allows distinction between a double aortic arch and a right aortic arch with an aberrant left subclavian artery. In cases of pulmonary artery sling, MR imaging enables full evaluation of the vascular anatomy and may also demonstrate the tracheobronchial anomalies. MR imaging may aid in diagnosis of innominate artery compression syndrome by demonstrating the extent of the tracheal luminal narrowing, the tracheal configuration, the structure causing the compression, and the size of the thymus. Finally, MR imaging usually allows distinction of long-segment tracheal stenosis from tracheomalacia and is especially helpful in cases of isolated stenosis. Three-dimensional reconstructions are also useful in assessing relationships between vascular structures and the adjacent trachea.

Prostaglandin-induced hyperostosis. A case report.

The use of prostaglandin-E1 (PGE1) to maintain patency of the ductus arteriosus in infants with ductal-dependent congenital heart disease is now well established. A 2.5-month-old child with cyanotic heart disease who required long-term PGE1 infusions; developed widespread periosteal reactions during the course of therapy. Prostaglandin-induced subperiosteal hyperostosis should now be considered in the differential diagnosis of neonatal cortical proliferation.

Two-dimensional coronary MR angiography without breath holding.

PURPOSE: To determine whether breath holding can be eliminated in two-dimensional magnetic resonance (MR) imaging of the coronary arteries by using real-time respiratory gating. MATERIALS AND METHODS: Thirty-one subjects (20 healthy volunteers, 11 patients) underwent MR imaging. In 13 subjects, a respiratory monitoring belt was used, and in 18 subjects, a navigator echo was used. MR imaging was performed with breath holding, respiratory gating, and respiratory gating with two signals acquired. Three reviewers conducted a blinded review of the images, and overall image quality was rated on a scale from 1 (poor) to 5 (excellent). RESULTS: Respiratory gating with two signals acquired provided image quality superior to that with breath-hold imaging (3.7 vs 3.0, respectively; P < .05). Measurements of signal-to-noise ratio (14.5 for respiratory gating with two signals acquired and 11.9 for breath holding) supported the results of the image review. Navigator-echo gating provided better image quality than the monitoring belt (3.7 vs 3.1, respectively; P < .05). CONCLUSION: Breath holding may be eliminated by gating image acquisition to a real-time monitor of respiratory position. Respiratory gating enables improved resolution by means of acquisition of multiple signals, provides aligned sections of coronary arteries, and improves patient tolerance.

Pediatric great vessel anomalies: initial clinical experience with spiral CT angiography.

PURPOSE: To evaluate the use of spiral computed tomographic (CT) angiography for the diagnosis of pediatric great vessel anomalies. MATERIALS AND METHODS: Techniques used in adult CT angiography were modified to allow imaging of 15 children aged 1 month to 12 years. Two-dimensional axial images and three-dimensional shaded surface display images of the airway and great vessels were generated from volumetric CT data and evaluated prospectively. Findings were correlated with results obtained at surgery (five patients), autopsy (one patient), bronchoscopy (one patient), or other imaging studies (eight patients). RESULTS: In 14 patients, CT angiography accurately demonstrated vessel anomalies, including double or right aortic arch (seven cases), aberrant subclavian artery (six cases), innominate artery compression syndrome (one case), unilateral pulmonary artery agenesis (one case), and pulmonary artery enlargement (three cases). One patient had normal vasculature. CONCLUSION: CT angiography is feasible in children and can be used to delineate abnormal great vessel anatomy.