Patterns of right aortic arch and mirror-image branching of the brachiocephalic vessels without associated anomalies.

It is unusual to have a right aortic arch with mirror-image branching of the brachiocephalic vessels and no associated congenital cardiac anomalies. Pathogenetic factors of this anomaly, and associated development of the derivatives of the pharyngeal arches, have not been explored extensively. Eleven patients with a mirror-image right aortic arch and no intracardiac anomalies have undergone evaluation at our institution since 1987. Of these, 4 had stenosis (n = 2) or atresia (n = 2) of the proximal left pulmonary artery. These included 2 with bilateral ductus arteriosus. Six patients had a vascular ring formed by a ductus arteriosus or ligamentum arteriosum from the descending aorta to the left pulmonary artery. Six patients were evaluated for deletion within the DiGeorge critical region of chromosome 22q11. All 6 of the patients with a vascular ring underwent division of the ductus arteriosus or ligamentum through a left lateral thoracotomy. None of the patients with stenosis or atresia of the LPA have undergone intervention. Two of the 6 patients who underwent evaluation for chromosome 22q11 deletion were found to have the deletion. At a median follow-up of 7 years (15 months to 12 years), the patients who underwent division of the ring are all alive and asymptomatic. Two of these patients have undergone repeat magnetic resonance imaging, 1 of whom had mild residual tracheal compression. A right aortic arch with mirror-image branching of the brachiocephalic vessels and no associated intracardiac anomalies is extremely uncommon. We have observed two basic patterns of this lesion: (1) with associated abnormalities of the proximal left pulmonary artery, (2) with a vascular ring formed by a ductus arteriosus or ligamentum from the descending aorta to the left pulmonary artery. Pathogenetic considerations are explored, with a focus on flow-related vascular development and the role of deletions within chromosome 22q11.

In vivo, in utero microscopic magnetic resonance imaging: application in a rat model of diaphragmatic hernia.

This article presents a microscopic MR technique for imaging small mammalian fetuses in utero and in vivo which can be used as a tool for studying normal and abnormal development in small animal fetal models, for targeting in utero intervention in such models, and for following development serially. This new method is applied to a rat model of congenital diaphragmatic hernia (CDH). Pregnant Sprague-Dawley rats were fed nitrofen at 9.5 days postcoitus to induce CDH in the fetuses. The dams were imaged to identify fetuses with CDH for targeted in utero intervention, which consisted of fetal tracheal ligation. Following tracheal ligation, the fetuses were followed serially with our MR technique. For MR imaging, the dam was anesthetized with intramuscular ketamine and intraperitoneal pentobarbital. In utero imaging was performed on a 4 Tesla MRI system using a multislice, fast spin echo sequence with a long TR and short effective TE. These results were validated by examining individual fetuses postmortem using high-resolution MR and anatomic dissection. The in utero, in vivo MR technique is highly accurate for diagnosing CDH and following the effects of surgical intervention, and shows promise as a tool for the study of embryogenesis in small animal models. Magn Reson Med 44:331-335, 2000.

Effect of surgical reconstruction on flow profiles in the aorta using magnetic resonance blood tagging.

BACKGROUND: The aorta that has undergone an aorta-pulmonary artery anastomosis may not exhibit the same velocity profile as the nonreconstructed aorta, whose velocity profile is thought to be uniform across the vessel diameter (plug flow). This may have an impact on fluid dynamics and will alter Doppler flow calculations. Our objective was to determine the impact of surgical reconstruction on the velocity and flow profiles of the reconstructed ascending and descending aorta. METHODS: Using a magnetic resonance imaging tagging technique that labels flowing blood (bolus tagging), we studied 22 patients (mean age, 8.6 +/- 4.7 years) who had had a Fontan procedure. A cine sequence labeled the blood and acquired the image after 20 ms in the middle of the ascending aorta and behind the left atrium in the descending aorta. The repetition time was 50 ms. RESULTS: The reconstructed ascending aorta displayed a velocity profile skewed anteriorly, whereas in the nonreconstructed aorta, the velocity profile was flat. Reconstructed aortas also displayed flows that were higher anteriorly, took a longer time to reach maximum velocity, and were less like "plug" flow than the nonreconstructed aorta. The descending aorta, regardless of whether aortic reconstruction was present, displayed velocity profiles (at various phases of systole) skewed posteriorly. CONCLUSIONS: The reconstructed aorta displays disturbed flow, and the velocities across the ascending aortic diameter are more varied than those in aortas without reconstruction and are skewed anteriorly. The descending aortic velocity profile in children is skewed posteriorly, regardless of whether aortic reconstruction is present. This information may help design and build a "better" aortic reconstruction.

A MRI bolus tagging method for observing helical flow in the descending aorta.

We present a MRI bolus tagging method for exploring the helical nature of blood flow in the aorta. Two image series are collected, the first to quantify longitudinal flow (coronal/sagittal imaging plane-transverse saturation plane), the second to measure rotational flow (transverse imaging plane-coronal/sagittal saturation plane). The experimental protocol has been established in healthy adult volunteers and children with normal vasculature. Our results permit immediate visualization of the unique nature of helical flow in each volunteer. We demonstrate evidence of rapid helical twist, no helical twist, and reversal of twist.