in Infants and Children with Right Ventricular Outflow Tract Obstruction
Erin E. Birmingham, MD; Abhineet M. Sharma, MD; Salil Ginde, MD; and Randy R. Richardson, MD
Key Words
Right Ventricular Outflow Tract Obstruction, Cardiac Computed Tomography Angiography, Coronary Artery Anomalies.
Introduction
Approximately 19% of congenital heart defects involve some degree of Right Ventricular Outflow Tract (RVOT) obstruction.[1] These obstructions can be at the level of the pulmonary valve, infundibulum, proximal branches, or distal branches of the pulmonary artery.[2] The severity of the clinical presentation is usually dependent on the severity of RVOT obstruction and can range from an asymptomatic infant to one that is severely cyanotic.
FIGURE 1 Prominent Conal Branch in a case of Tetralogy of Fallot (a, b) and Double-Outlet Right Ventricle (c). Color-coded 3D reconstructions. Anterior views of the heart showing the morphologic left ventricle (salmon), right ventricle (violet), aorta (a: red and b: neutral), and coronary arteries (red). In the case of Tetralogy of Fallot (a, b) The right coronary artery (yellow arrow) arises correctly from the right coronary sinus, however there is a prominent conal branch (white arrow) that arises off the RCA and courses anteriorly and slightly to the left. The left coronary artery has normal anatomy. This patient was found to have a constellation of findings compatible with TOF with subpulmonic pulmonary stenosis with post stenotic dilitation. In the case of DORV (c), the right coronary comes off the right coronary sinus as expected, however there is a prominent conal branch (white arrow) crossing over both the left and right outflow tracts.
Many of these cases of RVOT obstruction mentioned above have associated Coronary Artery (CA) anomalies, known as prepulmonary coronary arteries. In this anomaly the coronary courses anterior to the pulmonary artery or RVOT.[3] These prepulmonary coronary artery anomalies are associated with one or more cardiac malformations and alter surgical management if present.[5,6] The prepulmonary coronary artery anomalies reviewed in this study include a prominent conal branch (Figure 1), a Left Coronary Artery (LCA) crossing in front of the RVOT (Figures 2, 3, 4), and a duplicated Left Anterior Descending Artery (LAD) (Figure 5). All of these anomalies can be inadvertently damaged during surgical repair. In most of the cases of RVOT obstruction, the mainstay of treatment is interventional or intracardiac surgical management; however, the location of the CA anomalies can greatly affect what would otherwise be a routine surgical approach for a particular type of RVOT obstruction. Identifying these anomalies with the proper imaging modality prior to surgery can aid in the appropriate preoperative planning and avoid potentially life-threatening complications. The detection of coronary anomalies in children is challenging because they have smaller vessels, in addition to greater cardiac and respiratory motion compared with adult patients.[7] When evaluating the coronary arteries in Congenital Heart Disease (CHD), it is most important to determine the exact origin, number, course, and termination of the arteries.[3]
Cardiac computed tomography with multidetector-row computed technology is a novel modality that can be used as a “one-stop shop” to non-invasively evaluate the coronary arteries, cardiac morphology, and cardiac function. It is also useful to assess coronary morphology and patency prior to and following surgical intervention for Congenital Heart Disease.[8] Here, we compiled the largest number of coronary artery anomalies in RVOT obstruction evaluated by Coronary Computed Tomography Angiography (CCTA) in one study. Our study aimed to demonstrate the utility of CCTA as an imaging modality for the diagnosis of CA anomalies in cases of RVOT obstruction and CHD.
Materials and Methods
We retrospectively reviewed 220 standard preoperative CCTA exams in infants and children performed over the period between 03/28/2005 and 09/18/2010 at St. Joseph’s Hospital and Medical Center in Phoenix, Arizona. All images were obtained as a part of preoperative protocol. Of the 220 exams, we found 67 patients with RVOT obstruction. Of the 67 patients, there were a total of 37 males and 30 females, ranging in age from 1 day to 15 years (Mean: 312 days; Median: 7 days). CCTA was performed with a 64-slice multi-detector CT, with prospective EKG gating, followed by three-dimensional reformations. Our institution’s current technique for CTA with 3D reconstruction uses prospective gating with padding to capture functional source data with less radiation. Images were captured from the thoracic inlet to the upper abdominal cavity. The clinically indicated 3D data set was acquired only once and was also used to assess the quality of the coronary images.
A Kruskal-Wallis analysis was used to see if there was a significant difference in the frequency of CA in the specific subtypes of RVOT. A Chi-squared test was utilized to see if there was a statistically significant difference in the frequency of CA anomalies in our RVOT population when compared to the overall population based on two studies.[9-11]
The data analysis was approved by the institutional review board at St. Joseph’s Hospital and Medical Center. A waiver for informed consent was obtained. Literature was accessed through the PubMed search database using the phrases right ventricular outflow tract obstruction, coronary artery anomalies, cardiac computed tomographic angiography, and post-operative complications of Congenital Heart Disease.
To read the full article, please go to the September 2016 Issue of CCT.