Spiral computed tomography (CT). In addition to displaying the dissection as a double lumen, spiral CT also allows three-dimensional reconstruction, with precise depiction of the longitudinal extent—a prerequisite for planning endoprosthesis treatment. The sensitivity and specificity are both over 95%.
Magnetic resonance imaging (MRI) and magnetic resonance angiography. Like spiral CT, MRI allows three-dimensional reconstruction and identification of intramural hematoma, but it has several limitations in intensive care conditions (including the long examination time). The sensitivity and specificity of the method are both nearly 100%.
Conventional or digital subtraction angiography and coronary angiography. These procedures are now only carried out in exceptional cases and are indicated for assessing coronary heart disease before planned vascular surgery in type B dissections, for example.
2.1.6 Treatment
2.1.6.1 Conservative treatment
Aortic aneurysm
When the diameter of the aneurysm is not large enough for an intervention to be indicated, treatment essentially consists of secondary prophylactic medication, with a low-normal blood pressure level (< 120/85 mmHg) using β-blockers. Administering a statin to reduce inflammation of the vessel wall is generally recommended. Lifting of heavy weights (> 20 kg) is contraindicated.
Aortic dissection
In addition to symptomatic measures such as relieving pain (with morphine) and treating shock (with volume substitution), heart failure, and kidney failure, the classic treatment initially consists of reducing blood pressure, using negatively inotropic agents to reduce wall tension to prevent the dissection from progressing and leading to impending rupture. Sodium nitroprusside is the agent most frequently used for intravenous continuous infusion to achieve a controlled reduction in blood pressure; β-adrenoceptor blockers are used to reduce the speed of pressure increases (intravenous propranolol or esmolol). Blood pressure values should be reduced as much as possible both in the acute situation and during the subsequent course, ideally to 100–120 mmHg, and this usually requires multiple treatments. Even during initial treatment of the patient in the intensive care unit, noninvasive examinations have to be carried out and a cardiovascular surgery team (from the same institution or elsewhere) needs to be alerted. It is essential to ensure an adequate supply of blood, cross-matched if possible.
In type B dissections, the results of surgical treatment in the acute stage are not superior to those with conservative treatment. Most authors therefore recommend that immediate surgery, or alternatively percutaneous endoprosthesis implantation, should only be carried out when there are life-threatening complications such as rupture or ischemic kidney failure (Erbel et al. 2001). As the natural history is much better for type B dissections that are only diagnosed at the chronic stage, these should be treated electively with surgery or endoprosthesis placement, particularly when there are complications. If there are thromboses in the false lumen without substantial constriction of the aortic cross-section or branches, this can be regarded as a favorable course of spontaneous healing.
2.1.6.2 Endovascular and surgical treatment
The treatment options vary depending on which segment of the aorta is affected:
For diseases of the aortic root and ascending aorta, no endoluminal techniques are currently available. Open surgical procedures therefore predominate in this segment of the aorta.
In the area of the aortic arch, it is also mainly open surgical procedures that are used. However, specialized treatment for specific groups of patients is occasionally possible here using endoluminal stenting techniques, in combination with revascularization of the supra-aortic vessels (hybrid procedures).
In the area of the descending aorta, endoluminal treatment for aortic diseases has proved to be superior to open procedures and is now starting to predominate in the treatment of this segment of the aorta.
The thoracoabdominal segment can also be treated with endoluminal stents after debranching of the intestinal arteries in individual cases (hybrid procedure). Despite this, the majority of thoracoabdominal aortic aneurysms are still treated using conventional surgery.
Surgical treatment of the aortic root and ascending aorta in degenerative aneurysms
Supracoronary replacement of the ascending aorta
Supracoronary replacement of the ascending aorta is indicated in patients in whom the aortic root is not affected by disease and the aneurysm is restricted to the ascending aorta. In supracoronary replacement of the ascending aorta, the aorta is completely transected above the coronary arteries and proximal to the aortic clamp in the first step. Attention should be paid here to ensure, firstly, that there is a sufficient margin in the area of the supracoronary segment to allow the anastomosis to be created; and secondly, to ensure also that not too much of the diseased aortic wall remains. After resection of the aorta, both aortic stumps are initially strengthened with a 0.5-cm wide felt strip, which is sutured onto the aortic stump from outside with 4–0 Prolene using mattress sutures. The suture is not initially tied, to ensure that the diameter is not reduced.
The size of the presealed Dacron tube prosthesis is then selected using a folding measuring instrument. The proximal and distal anastomoses are created with 3–0 Prolene using a continuous technique. The proximal anastomosis is done first, and then the distal anastomosis. Air is removed from the prosthesis before blood flow is restored.
Aortic valve replacement and supracoronary replacement of the ascending aorta
Isolated aortic valve replacement in combination with supracoronary replacement of the ascending aorta is always applicable in the presence of significant aortic valve disease with an aneurysm of the ascending aorta, without marked dilation of the root. In this technique, attention should be given to ensuring that a sufficiently long border is left in the supracoronary aortic resection, since otherwise (e.g., when a biological valve is used) problems may arise when creating the proximal anastomosis. Otherwise, both the valve replacement and supracoronary aortic replacement are carried out using the same technique described above.
Replacement of the ascending aorta and aortic root with reconstruction of the aortic valve
In aortic root aneurysms with an intact, delicate aortic valve without structural defects, two surgical techniques are now available making it possible to do without valve replacement (replacement of the aortic root and ascending aorta, combined with reconstruction of the aortic valve). The surgical techniques that can be used in these cases are the David operation and the Yacoub operation.
David operation
There are numerous modifications and variations (David I–V) on the surgical technique first described by Tirone David. The technique preferred by this author is described here.
After administration of cardioplegia, the aortic root is initially dissected. The ascending aorta is then resected and the aortic root is further dissected, with the coronary ostia visible. As a rule of thumb, a 28-mm presealed Dacron tube prosthesis is used in men and a 26-mm presealed Dacron tube prosthesis in women. The size can be checked again using a folding measuring instrument, and it is best to do this at the still-preserved sinotubular junction. The two coronary ostia are then dissected out and the aortic root is dissected until the subannular sutures