Vascular Medicine. Thomas Zeller

occurs most often in the area of the ascending aorta, into the pericardium, leading to cardiac tamponade. However, rupture may also take place into the mediastinum or mediastinal organs (esophagus, trachea), into the pleura, retroperitoneum, or peritoneum. The branches of the aorta may be compromised or occluded, leading to a wide variety of ischemic organ symptoms. In dissection of the ascending aorta, the coronary arteries, carotids and brachial arteries are at risk, while in dissection of the descending aorta the renal arteries, celiac trunk, and pelvic arteries are affected. In dissection of the ascending aorta, the cusps of the aortic valve are often undermined, leading to acute aortic valve regurgitation of varying degrees of severity. The resulting acute volume loading of the left ventricle can cause left ventricular failure and lead to pulmonary edema. Left-sided heart failure is promoted by the perfusion disturbance in the coronary arteries that is often present at the same time if the right coronary or left coronary sinus of the aortic root is involved in the dissection. The prognosis in this condition partly depends on the extent of the dissection. Signs of impending rupture such as pericardial effusion or pleural effusion and widening of the mediastinum, are associated with a mortality rate of more than 50% (Erbel et al. 2001).

      2.1.2.3 Aortitis

      Other diseases of the aorta include the appearance of inflammatory cells in the media or adventitia. This condition is known as aortitis, and again it can be divided into two major categories:

      

Infectious aortitis

      

Aortitis without known infectious pathogens

      Infectious diseases of the aorta with confirmed pathogens can be divided into the following types:

      

Chronic bacterial infections (not necessarily originating in the aorta per se, but often associated with chronic inflammatory changes in the aorta)

      

Acute primary infections of the aorta (mycotic aneurysms)

      

Infections of the aorta after prior surgery (usually involving prosthesis materials made of plastic)

      In aortitis without known infectious pathogens, there is again a distinction into cases involving mainly:

      

The aorta (Takayasu disease) or

      

Other organ systems, with only secondary involvement of the aorta and other arteries (giant cell arteritis, rheumatoid arteritis, Behçet disease) (see also Part C, on vasculitides)

      2.1.2.4 Traumatic aortic rupture

      Traumatic changes in the aorta include primarily traumatic aortic rupture in typical locations—i.e., distal to the origin of the left subclavian artery.

      2.1.2.5 Surgical anatomy

      The aorta is divided into various segments. The segment above the aortic valve up to the sinotubular transition is known as the aortic root. The sinotubular transition marks the boundary between the aortic root and the ascending aorta. The ascending aorta extends from the sinotubular transition to the start of the brachiocephalic trunk. The aortic arch extends from a line lying at right angles proximal to the brachiocephalic trunk to a line lying at right angles distal to the origin of the subclavian artery. The descending aorta is the segment from the left subclavian artery to the aortic hiatus in the diaphragm. The abdominal segment of the aorta is the final section, from the aortic hiatus to the aortic bifurcation.

Table 2.1–1 Normal diameter of the aorta in adults (from Svensson and Crawford 1997).

Segment	Transverse diameter (mm)
Ascending aorta	32
Proximal aortic arch	32
Proximal descending aorta	28
Middle descending aorta	27
Distal descending aorta (at the level of the superior mesenteric artery)	26
Proximal infrarenal aorta	19
Distal infrarenal aorta	17
Common iliac artery	9
Common femoral artery	7

      Familiarity with the diameter of the healthy aorta plays an important role in correct decision-making regarding which type of operation is best suited to each patient. The diameters are listed in Table 2.1-1.

2.1.3 Clinical findings

      The presentation is usually sudden in onset, sometimes in connection with severe physical or psychological stress (with an increase in blood pressure), and less often starting from a state of complete rest. The rupture event is usually associated with dramatic symptoms. The symptoms depend on the location and extent of the dissection, involvement of branching vessels and of the aortic valve, as well as the onset and location of the rupture. The latter can lead to sudden death that is only explained at autopsy. The major symptom is usually extremely severe chest pain radiating to between the shoulder blades.

2.1.4 Differential diagnoses

      Common differential diagnoses include costovertebral syndrome (in which pain is position-dependent and can usually be induced by manual provocation), myocardial infarction (in which the pain center is retrosternal), pulmonary embolism (in which pain is respiration-dependent or there is dyspnea or hyperventilation), acute pleuritis (auscultation), and acute pericarditis (auscultation). More rarely, aortic dissection leads to stroke (with cerebral symptoms such as visual disturbances, syncope, coma, pareses, etc.), perfusion disturbances in the extremities, acute abdomen, or renal infarction (differential diagnosis: embolic occlusion).

      

2.1.5 Diagnosis

      A careful clinical examination of the arterial vascular system usually leads to the first signs suggesting suspected aortic dissection. New systolic and diastolic noise phenomena over the aorta and differences in extremity blood pressure and peripheral pulse require further clarification.

      Laboratory tests. Routine laboratory test parameters show only nonspecific findings (elevated erythrocyte sedimentation rate and C-reactive protein, leukocytosis, etc.). However, they are important for follow-up purposes, for recognizing hemorrhage and organ dysfunction. A specific marker that has recently come into use is an increase in smooth muscle myosin heavy chain (SMMHC) values. ECG. The ECG can reveal nonspecific findings such as left ventricular hypertrophy, ischemic ST changes, and infarct patterns with coronary involvement (20%) or low voltage in pericardial effusions. X-ray. Chest radiography plays a subordinate role nowadays, but can reveal elongation and/or widening of the ascending aorta and aortic arch, and in some cases also mediastinal widening. A tumor process, atelectasis, or pneumothorax can be excluded in the differential diagnosis.

      Transthoracic and transesophageal echocardiography, duplex ultrasonography. Ultrasound diagnosis is the diagnostic method of choice, as it can be carried out