The Frozen Elephant Trunk (FET) procedure is a surgical technique used to repair the thoracic aorta, the largest artery in the body, which carries blood from the heart. The name combines a reference to a large animal’s appendage with a term suggesting extreme cold. This article explains the origins of this terminology by examining the surgical device, the original technique it replaced, and the protective measures required during the operation.
Understanding the Surgical Need
The thoracic aorta, which runs through the chest, is organized into three main segments: the ascending aorta, the aortic arch, and the descending aorta. The aortic arch gives rise to the main arteries supplying blood to the head and upper extremities. When diseases like extensive aortic aneurysms or complex aortic dissections affect this region, a large portion of the vessel often needs repair.
An aneurysm is a ballooning of the vessel wall, while a dissection involves a tear in the inner layer, allowing blood to split the layers of the wall. Repairing these conditions is challenging because they often span from the arch into the descending aorta. Traditional open surgery on both segments requires extensive access and carries significant risk, making a single, comprehensive repair necessary.
Deconstructing the “Elephant Trunk” Analogy
The term “Elephant Trunk” originates from a technique developed by German surgeon Dr. Hans Borst in the 1980s. This original procedure was a planned two-stage operation to manage extensive aortic disease. The first stage involved replacing the aortic arch with a synthetic tube graft.
The key feature was that the downstream end of this prosthetic graft was left unsecured and deliberately long. This free-floating segment extended into the descending thoracic aorta, hanging there unsupported. This visual resemblance—a long, dangling tube inside the body—led surgeons to coin the term “elephant trunk.”
The purpose of this dangling graft was to simplify the second operation, which would occur months later. During the second surgery, the surgeon would locate the “trunk” and connect a new graft to it, extending the repair down the descending aorta. The analogy marked a staged approach to a difficult surgical problem.
The Meaning of “Frozen”
The addition of the word “Frozen” signifies the transformation of the original technique into a single-stage, or “hybrid,” repair. This term has a dual meaning, referencing both the device and the patient’s state during the procedure. The device is a specialized hybrid graft that includes a conventional fabric tube for the arch replacement, with a self-expanding metal stent attached to the end.
The stent portion is deployed into the descending aorta, effectively freezing the disease progression by stabilizing the vessel wall. “Frozen” also refers to the deep hypothermic circulatory arrest (DHCA) required to safely implant the device.
During DHCA, the patient’s core body temperature is significantly lowered, often to around 20 degrees Celsius, which allows the surgeon to temporarily stop blood circulation. This extreme cooling protects the brain and other organs from damage while the surgeon works in a bloodless field.
The Hybrid Procedure and Patient Outcomes
The modern FET procedure synthesizes open surgery with endovascular stenting, creating a single-stage solution. The hybrid graft, once deployed, stabilizes the diseased descending aorta by providing structural support. This stented segment works to seal off the inner tear in the aorta, which encourages positive aortic remodeling.
The stent graft promotes the thrombosis, or clotting, of the false channel created by a dissection. By stabilizing the aorta in one session, the FET procedure eliminates the need for the second open surgery required by the traditional “Elephant Trunk” technique. This single-stage approach avoids the complications and mortality associated with the waiting period between the two operations.
This repair has led to improved long-term outcomes, including five-year survival rates reported to be over 80 percent. The implanted stent also serves as a secure landing zone, making any future endovascular interventions on the more distant aorta simpler. By addressing extensive aortic disease comprehensively in one operation, the FET procedure has become the preferred method for treating these life-threatening conditions.