Grasping the basics of simple transpositions
We'll take you on a trip down surgical memory lane to discuss the various approaches used in treating simple transpositions and why knowing about this is crucial to performing a successful echo.
The surgical approaches used to treat simple transpositions have evolved significantly over the last 60 years. But that's ancient history. All you really need to know is how we treat them today—right? Wrong! In this video, from our Echo Masterclass: Adult Congenital Heart Disease course, we'll take you on a trip down surgical memory lane to discuss the various approaches used in treating simple transpositions and why knowing about this is crucial to performing a successful echo.
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[00:00:00] Simple transposition is when the intracardiac chambers are normally arranged but the vessels arise from the wrong ventricle. Remember the transposition of the great arteries by definition is when the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. Here, the heart has looked normally so the ventricles are in their correct location but there has been abnormal spiraling of the infundibulum
[00:00:30] during embryonic development. The result is these two independent circulations. The oxygen-rich blood on the left side of the heart is never able to deliver the oxygen to the body and the oxygen-poor blood on the right never gets to the lungs to pick up more oxygen. In utero, there's not so much of a problem because the lungs are not working and mixing of blood is facilitated through the patent foramen ovale at atrial level and the patent ductus arteriosus
[00:01:00] at arterial level. At this stage, oxygen is sourced from the placenta but when the baby is born and starts to use the lungs for breathing, changes occur pretty quickly in the first hours to weeks. Spontaneous breathing causes pulmonary vascular resistance to fall and systemic vascular resistance to rise. The umbilical cord is cut and prostaglandins supply stops. Within minutes of birth, the patent foramen ovale starts to close. The patent ductus arteriosus
[00:01:30] closes within 10 to 15 hours of birth. Days to weeks after birth, the umbilical connections are constricted. And so as these normal changes occur, a baby with simple transposition deteriorates pretty quickly and surgery is required urgently. Different treatment strategies have been used over the years. Early on, the focus was to help the child to survive. Let's start back in the 1950s. Before the 50s, this was a fatal circulation [00:02:00] due to the inability to get oxygen to the body so the brain and the gut will become a scheming and multi-organ failure would follow. A few babies survived to about one year of age and it was revealed that they also had a ventricular septal defect. This allowed mixing of the blood and actually helps the circulation. The medical community discovered this and decided if they could find a way to encourage mixing of the blood, the child would do better. One method was to give the child prostaglandin
[00:02:30] E, this would inhibit constriction of the ductus arteriosus leaving the doctors open to facilitate mixing. This strategy is still used today to buy time before going to surgery in the first days of life. Moving forward to the mid-50s and into the '60s, there was surgical experimentation to correct the position of the great arteries but the coronary arteries proved to be a major issue and the experiments were unsuccessful. There was lots of experimentation in many facets
[00:03:00] of life at that time. And whilst the Beatles were gaining fame and everyone seemed to be experimenting with everything, the cardiologist persevered with the transposition patients and some major breakthroughs were made. In the '60s, Dr. William Rashkind developed a percutaneous method of atrial septostomy. The strategy was to create a hole using the patent foramen ovale which already existed. Using the Rashkind procedure, a balloon was fed through the venous system across the patent foramen ovale and inflate
[00:03:30] it. While still inflated, it was pulled back across the interatrial septum increasing the size of the hole. This allowed even more mixing and again, bought time for these tiny little babies. This procedure replaced surgical atrial septectomies. With this procedure alone, some children made it to their early teens. At about the same time, there was the development of the atrial switch operations, a term used to describe the baffling or rerouting of the blood at atrial level,
[00:04:00] which corrects the circulation by getting the oxygen-poor blood to the lungs and sending the oxygen-rich blood to the body. There are two variations of this technique, the Senning Procedure which refashioned atrial septal tissue to redirect the flow, a kind of surgical origami and the Mustard Procedure which achieved the same but used artificial baffles. The echo appearance of both techniques is the same. In patients who had a ventricular septal
[00:04:30] defect, the Rastelli operation was developed which used to ventricular septal patch and a conduit from the right ventricle to the pulmonary artery which is placed outside the heart as seen here. This was a good operation because no coronary artery manipulations were involved and the procedure is still used today. These operations were use widely throughout the '70s and the prognosis for these patients was markedly improved. However, as the patients grew older, the atrial
[00:05:00] switch patients tended to develop heart failure through the '70s, experimentation continued and some success with the arterial switch operation or Jatene procedure was achieved. Not to be confused with a similarly sounding atrial switch procedure which is baffling, the arterial switch procedure improved on the original surgeries from the '50s by correcting the position of the great vessels with careful reimplantation of the coronary arteries. The Jatene or arterial
[00:05:30] switch procedure was widely adopted in the 1980s and today remains the procedure of choice for simple transposition. So why the history lesson? Great question. History is always important but what this means for us in the echo lab is that when we scan a patient who has had a simple transposition repaired, we need to be prepared to assist them using particular techniques. The atrial switch procedure isn't used anymore, but there are still adults in their 30s and 40s who
[00:06:00] had this surgery performed.