Georgia Tech has teamed with pediatric cardiologists and surgeons to develop new technologies to improve surgical planning for one of the most complex congenital heart defects in infants.
Although the normal heart has two ventricles - lower chambers of the heart used for pumping blood through the body - some babies are born with just one lower chamber. Considered one of the most complex congenital heart defects, single-ventricle often leads to congestive heart failure if not repaired.
Patients with this defect often undergo multiple surgeries to reconfigure the pulmonary and systemic systems in operations called "Fontan Repairs." Staged over several years, these surgeries are an option used for treating the single-ventricle defect. Following the procedures, a variety of outcomes from good to poor have been reported.
In an effort to develop optimal surgical designs based on the child's anatomy, a team of biomedical engineers and pediatric cardiologists and surgeons have announced that they have begun developing improved technologies to assist surgeons in surgical planning of the Fontan surgery. These technologies could advance surgical methods by more specifically tailoring the procedure to the patient and possibly enhancing the patient's quality of life following the procedure.
The team is funded by a $5.1 million award from the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH).
"Optimization of the Fontan procedure is a clinical problem," said Ajit Yoganathan, Regents Professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "Our goal is to improve the efficiency of this procedure, which is commonly utilized today."
The team, led by Georgia Tech, consists of several members from three other institutions. Together they have collaborated in the development of improved imaging technologies for use in the pediatric group. The lead co-investigators and institutions involved are: Yoganathan at Georgia Tech; Shiva Sharma, a pediatric cardiologist at Sibley Heart Center at Children's Healthcare of Atlanta; Carol Lucas, a professor of biomedical engineering at the University of North Carolina at Chapel Hill (UNC); and Mark Fogel, a pediatric cardiologist at the Children's Hospital of Philadelphia.
A Multi-Institutional Approach
Various aspects of the research will be divided among the four institutions based on each institution's specialties and expertise.
Engineering and computational studies will be conducted primarily at Georgia Tech, while patient recruitment and MRI studies will be performed at Children's Healthcare of Atlanta, Children's Hospital of Philadelphia and UNC.
Engineering tools such as computational fluid dynamic studies and the development of glass models of the heart with different Fontan surgery connections will be performed at Georgia Tech and UNC. UNC will also conduct animal studies.
Recruitment, care and study of Fontan patients will be conducted at Children's Healthcare of Atlanta, UNC and Children's Hospital of Philadelphia. Non-invasive, 3-D MRI anatomic and flow studies on Fontan patients will be performed to serve as input data for the in-vitro and computational modeling studies.
Central to the study is understanding the single-ventricle defect, its anatomy and physiology in order to improve surgical configurations and planning. The investigators are hoping their research will yield important information and better options to assist surgeons in determining the optimal surgical treatment for these young heart patients.
"The main focus of this research is to give surgeons a tool with which to predict not only the outcome of a Fontan procedure, but also the best possible configuration," Yoganathan said. "This is done by optimization. In order to optimize the design of the Fontan procedure we know that the repair should maximize the flow of blood. This is crucial in a heart that has only a single ventrical as the pumping chamber for all blood. "
Shiva Sharma, M.D., pediatric cardiologist at Children's Healthcare of Atlanta explains that currently, surgery for complex congenital heart disease is based on the surgeons experience. "The utilization of computational fluid dynamics (CFD) introduces a more scientific approach using computer and graphic technology to correct heart defects For the first time, computer technology is being used to assist surgeons in correcting single ventricle defects in the most efficient way. Furthermore, this will enable customization of the Fontan repair to suit a patient's unique anatomy and physiology. This is a paradigm shift."
In the U.S., two out of every 1,000 babies are born with single ventricle defects. A look at the Internet shows dozens of web sites set up by parents of infants born with a single ventricle to share updates, photos and even advice.
Surgical operation procedures vary for single ventricle patients, depending on factors such as age, symptom status or condition of the lung blood vessels. The most popular procedure used to correct the problem is called the total cavopulmonary connection (TCPC) - the method on which the research team will focus.
The Fontan Procedure
The Fontan Procedure involves an anatomical reconfiguration that diverts the blood flow coming to the right side of the heart directly to the lungs, so that the heart no longer has to pump blood to the lungs.
The operation seeks to separate the heart into two circulations and allow oxygen-poor blood (blue) to go to the lungs and oxygen-rich blood (red) to go to the body. By substantially reducing the mixing of blue and red blood, the body receives a normal or near-normal oxygen supply. It also reduces the risk of a stroke or other complications, and decreases the workload on the single ventricle.
To separate the deoxygenated blood and oxygenated blood, doctors create a baffle, or wall, in the right atrium to prevent the deoxygenated blood from returning to the heart. The right atrium is then attached to the pulmonary artery, so that all of the returning deoxygenated blood flows straight to the lungs. Since this causes an increase in pressure in the systemic veins returning blue blood from the body, a small hole is created in the wall, acting as a pressure relief valve while the child becomes used to its new circulation.
During this procedure, the infant is placed under general anesthesia and special monitoring IVs are placed. The chest is entered through the chest bone. The patient is connected to a heart/lung bypass machine during the surgery. Once the heart is stopped and emptied, the blood flow from the inferior vena cava (the dark, unoxygenated blood returning from below the diaphragm) is diverted towards the pulmonary artery.
After The Procedure
After surgery the child usually takes a number of days to recover from the anesthesia, the use of the heart-lung bypass equipment and the surgery. Initially, the child will be on a ventilator and may need support from IV medicines and a temporary pacemaker. Once the breathing tube is out, the main goals for the child's recovery are to return to normal physical activity. For the medium to long-term, a spectrum of outcomes from excellent functional ability to severe limitation with many hospitalizations is seen.
"The ultimate goal of our research is to improve this long-term functional outcome of all our patients," Sharma said. "This prospective, multi-institutional study will need to be done and we propose to show the surgical optimization done under with this technology translates into improved functional outcome."