Elephant Trunk Operation
Diagram of Operation
The elephant trunk procedure is a two part procedure. the first part consists pf placing a tube of Dacron in the descending aorta via the open aortic arch. Its proximal end is anchored, and the distal end floats free. At a second operation via a left thoracotomy the aorta is cross clamped distal to the left subclavian, and then opened revealing the Dacron placed at the previous operation. This means that dissection is much easier.
Another option although less tried and tested in some cases is the frozen elephant trunk.
Aneurysmal disease of the arch and proximal descending aorta.
Not fit enough for the second part of the procedure, the left thoracotomy, usually due to poor PFTs. These patients are sometimes better served by the frozen elephant trunk
Patients with aortic aneurysms usually require multiple tests to evaluate the aorta. The best method for optimal imaging of the thoracic and thoracoabdominal aorta is somewhat institution-specific, based on the availability of imaging equipment and expertise. Although physical examination may detect large infrarenal abdominal aortic aneurysms, thoracic involvement of a palpable aortic aneurysm is rarely suspected during physical examination unless the abdominal component is so extensive that the cephalic projection cannot be palpated because of the costal margins. Plain chest x-rays may demonstrate widening of the descending thoracic aortic shadow, which may be highlighted by a rim of calcification outlining the dilated aneurysmal aortic wall. Aneurysmal calcium may also be seen in the upper abdomen on a standard x-ray made in the anterior, posterior, or lateral projections. Enough calcification may be present in the aortic wall to make the diagnosis of aneurysms in 65% to 75% of cases. A negative plane chest roentgenogram does not exclude the diagnosis of aortic aneurysm.
Ultrasonography, although useful in evaluating infrarenal abdominal aortic aneurysms, is not useful for imaging the thoracic or suprarenal aorta primarily because of overlying lung tissue. The advantages of ultrasonography are wide availability, low cost, portability, noninvasiveness, lack of ionizing radiation, and rapid examination. When the definitive neck of an infrarenal abdominal aortic aneurysm cannot be demonstrated at the level of the renal arteries, thoracoabdominal aortic involvement should be suspected.
Transesophageal echocardiography provides access to the proximal aorta, and complements transabdominal ultrasonography. The technique requires considerable technical skill both in obtaining adequate images and in interpretation. The technique is excellent for determining the presence of dissection but has limitations in evaluating the region of the transverse aortic arch and upper abdominal aorta.
Simple chest roentgenogram, EPA (A) and lateral (B), demonstrating calcified rim in the aortic wall of a thoracoabdominal aortic aneurysm.
Classical aortography remains the mainstay for preoperative evaluation of patients with thoracoabdominal aortic aneurysms. It has the ability to define the extent of aneurysm, branch vessel involvement, and branch vessel stenotic lesions. Risks of aortography include renal toxicity from the large volumes of contrast material required to adequately fill large aneurysms. There is the additional risk of embolization from laminated thrombus secondary to manipulation of intraluminal catheters. Anterior, posterior, oblique, and lateral views are obtained simultaneously to obtain satisfactory information regarding branch vessels. Patients with suspected renal and/or visceral ischemia, aorto-iliac occlusive disease, horseshoe kidney, or peripheral aneurysms should be considered for aortography prior to TAAA repair.
Aortography is performed in a well-hydrated patient who is also receiving intravenous fluids. Routinely, 1000 mL of 5% dextrose and Ringer's lactate solution with 25 g of mannitol are given intravenously immediately prior to the procedure and are continued at 100 mL per hour following study. If at all possible, operation is delayed for 24 hours or longer to determine the effects of angiography on renal function and to permit diuresis of the contrast agent. If renal insufficiency occurs or is worsened, the surgical procedure is postponed until renal function returns to normal or is satisfactorily stabilized.
Computed tomography scanning is widely available and provides access to the entire thoracic and abdominal aorta. In addition to diagnosis, information regarding location and extent is provided. Major branch vessels including the celiac, superior mesenteric, renal, and iliac arteries, left subclavian, and virtually all adjacent organs are imaged. Although not widely available, computer programs can construct sagittal, coronal, and oblique images as well as three-dimensional reconstructions. Computed tomography scanning, which is contrast-enhanced, provides information regarding the aortic lumen, mural thrombus, presence of aortic dissection, intramural hematoma, mediastinal or retroperitoneal hematoma, aortic rupture, and periaortic fibrosis associated with inflammatory aneurysms. Although angiography remains the "gold standard" for evaluating aortic occlusive disease, improvements in computed tomography (CT) and magnetic resonance imaging (MRI) are leading to strategies that provide excellent images without the morbidity or cost of angiography. Because of improvements in noninvasive imaging modalities and a stroke risk of 0.6% to 1.2% with angiography, the role of diagnostic angiography for aortic arch vessels is becoming limited.
Computed tomography (CT) scan demonstrating large calcified thoracoabdominal aortic aneurysm with intraluminal laminated thrombus.
A clinically valuable advance in recent times has occurred in the area of spiral CT images. Sophisticated spiral CT hardware and CT protocols are important for good results, but the image quality is equally dependent on software. Traditionally, only limited hard copies of selected views are provided to surgeons; this may exclude a great deal of the information that is available from the volume of data acquired by spiral CT. To make the best use of CT angiography (CTA) and multiplanar reconstructions or multiplanar reformats (MPRs), a CT workstation is used to scroll through multiple axial or sagittal cross-sections in a "cine" mode. This approach to viewing can be very helpful in clarifying the patient's anatomy, following a structure from one slice to the next in rapid succession. For these reconstruction methods, if the spiral CT data are stored digitally in a computer hard drive, they may be viewed from many different perspectives without exposing the patients to any additional radiation or contrast.
An important advantage of magnetic resonance angiography (MRA) over computed tomography angiography (CTA) is that it uses nontoxic gadolinium instead of nephrotoxic contrast. Additionally, the patient avoids exposure to ionizing radiation. MRI employs radiofrequency energy and a strong magnetic field to produce images. MRA provides the same volume of information as does CTA with regards to image processing, but further provides information on relative quantity of blood flow and an appearance similar to conventional angiography. Additionally, the technique can provide a three-dimensional anatomical analysis. MRA imaging of the aorta can elucidate information on wall composition, wall thickness, and intraluminal thrombus, whereas conventional aortography only depicts the lumen. A current limitation of MRA is the susceptibility to artifacts created by ferromagnetic materials. Although expensive, the technology is widely available and has the capability of accessing the entire aorta. MRA images can more clearly distinguish arteries and veins from viscera and other surrounding tissue.
Due to size discrepancy of the graft and the aorta for the creation of the proximal elephant trunk procedure the Dumbo graft or flanged graft has been introduced (see below).
Diagram of Operation
Typical patients that may be suitable for the elephant trunk procedure.
Staged Aortic Replacement with Elephant Trunk
False aneurysm formation
Routine with yearly CT or MRI