Acute aortic syndrome: a term used to describe a constellation of life-threatening aortic diseases that have similar presentation. Major entities that comprise acute aortic syndrome: aortic dissection (AD), intramural hematoma (IMH) and penetrating aortic ulcer (PAU).
Aortic dissection occurs most frequently from this triad followed by IMH.
- Aortic dissection
Definition of AD: dissection occurs when the intima of a blood vessel is damaged and blood enters the space between the layers of the vascular wall, separating (dissecting) them.
The resulting two lumens may be distinguished as a true lumen, encircled by the intima, and a false lumen. The two are separated by a dissection flap or intimal flap. Away from the site of the initial damage, new fissures may develop on other segments of the blood vessel, creating potential re-entry points for the blood from the false lumen into the true lumen. This is referred to as refenestration.
Figure 1 A-B. CTA of an aortic dissection; true lumen (a), false lumen (b), intimal flap (arrow)
- A) longitudinal view B) transversal view
I/1. The classification of aortic dissections
Aortic dissections are classified according to the anatomic location of the entry tear and the time between onset of symptoms and patient presentation. Finally they can be divided into complicated and uncomplicated groups.
Temporal
Acute: within 14 days after the initial onset of symptoms
Subacute: period from 14 days to 90 days
Chronic: after 90 days
Anatomic-based on the location of the intimal tear.
Stanford type A: entry tear is proximal to the origin of left subclavian artery-requires heart surgery
Stanford type B: entry tear is distal to the origin of left subclavian artery-requires vascular surgery
| Occurrence (%) | 60% | 10-15% | 25-30% |
| Type | DeBakey I | DeBakey II | DeBakey III |
| Stanford A (Proximal) | Stanford B (Distal) | ||
Complicated: signs of malperfusion and/or aortic rupture and/or hemodynamic instability
Uncomplicated: paient is hemodynamically stable, without above mentioned complications
I/2. Epidemiology
Incidence: 2.5-3.5/100,000 patients/year.
According to major registers and studies, approximately 70% of these is Stanford A, and approximately 30% is Stanford type B.
I/3. Etiology
Predisposing factors include:
– connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome)
– iatrogenic intimal damage (coronary intervention, intraaortic balloon pump, aortic intervention)
– vasculitis (autoimmune, infective)
– malformations (bicuspid aortic valve, coarctation of the aorta)
– > 5 cm ascending aorta diameter
– cocaine abuse
– hypertension
-trauma
– pregnancy
– long-term steroid treatment
– atherosclerosis.
I/4. Symptoms
Dissections vary dynamically in terms of time and location. Subsequently, they also vary in symptoms, which makes dissections unpredictable.
-most common presentation is excruciating pain depending on the site of dissection: thoracic, dorsal, abdominal
-generally hypertension associates AD, significant increase in blood pressure occurs in 70% of all type B AD cases
– the weakened vascular wall may tear or become permeable, resulting in: cardiac tamponade, hemothorax, retroperitoneal bleeding, and subsequently, hemorrhagic shock
– aortic insufficiency which may develop in acute heart failure.
– circulatory insufficiency of the side branches may lead to:
cardiac (ECG abnormalities, myocardial infarction)
neurological (TIA, stroke, paraparesis, or paraplegia)
extremity (upper or lower limb ischemia)
renal (oliguria, anuria)
visceral (abdominal pain, red currant jelly stool, acute abdomen) symptoms, in any possible combination.
I/5. Diagnosis-CTA
The differential diagnosis of aortic dissection is a difficult task, due to its varied, fluctuating range of clinical symptoms. Thoracoabdominal-pelvic CTA is the only method that can clearly verify the presence of aortic dissection, as well as its site and extent, along with any possible hemorrhaging or circulatory insufficiency on the side branches (malperfusion).
Figure 3. CT angiography of Stanford type B aortic dissection
I/6. Treatment of type B AD
Aortic dissection patients require personalized treatment planning. In case of acute or recently symptomatic type B dissection, close monitoring at an intensive care unit is recommended.
In uncomplicated cases multiple control CTA is required, if there are signs of progression patient needs endovascular treatment or open surgical repair.
- Monitoring of vital signs
-Target systolic blood pressure: 100-120 mmHg
-Pulse: 60/min
- Medical treatment: antihypertensive drugs(in case of hypertonia)+painkillers
-beta-blocker (labetalol)
-vasodilatator (urapidil, nitroglycerin)
-major analgetics
All patients presenting wit AD requires medical treatment! Usually it is sufficient in uncomplicated type B AD cases (if control CTA does not show signs of progression).
Long term therapy includes antihypertensive treatment (primarily with beta-blockers).
- Endovascular treatment
-Stentgraft implantation: stent graft is driven through the femoral artery to seal the entry tear, contrast agents help in positioning.
-Goal: 1. coverage of the proximal entry tear, 2. expansion of the true lumen with restoration of flow distally, 3. obliteration of false lumen flow with subsequent complete thrombosis
-Indication: 1. acute complicated type B AD (stentgraft implantation means gold standard treatment in these cases) , 2. should be considered in type B subacute AD based on the aortic morphology, 3. moderate to high surgical risk patients presenting with type B chronic AD with a descending aortic diameter greater than 60mm
-Debranching: if the proximal landing zone (landing zone: sound segment of the aorta, where the proximal and distal ends of a stengraft can be placed) involves the origin of one or more supraaortic branches, debranching is required (otherwise the territory supplied by the covered branch would suffer ischaemic damage).
In this case vascular surgeon should perform an extraanatomic bypass between the supraaortic branches (carotico-carotid crossover bypass, subclavio-carotid transposition etc.).
-In cases of side branch compression need may arise for stent implantation.
- Open surgical repair
Carries a high perioperative mortality and morbidity risk (25-50%).
-Refenestration: resection of the intima flap from the visceral segment of the aorta
-Aorto-aortic interposition: replacement of a segment of the aorta
-Indication: 1. should be considered in low surgical risk patients presenting with aneurysmatic or symptomatic type B chronic AD, 2. complicated type B acute AD if endovascular treatment is contraindicated or following failure of it.
I/6. Summary
Patients presenting with aortic dissection require close monitoring, regular follow-up and tight blood pressure management for the rest of their lives. The weakened vascular wall has a predisposition for dilation, which may lead to post-dissection aneurysm. If an aneurysm reaches a size that requires surgery, surgical risk may be extreme, and treatment may also require replacement of the entire aorta. All available endovascular and open surgery options may be necessary to treat these conditions.
-Aortic dissection usually presents with severe symptoms, rarely remains asymptomatic.
In the differential diagnosis of thoracoabdominal symptoms, dissection should be considered.
-The “gold standard” imaging method is CTA. Apart from aortic dissection, we must also rule out the possibility of acute coronary syndrome and pulmonary embolism (triple rule-out).
-Stanford type A aortic dissection requires immediate cardiac surgery, while Stanford type B dissection requires urgent vascular surgery.
-The treatment of type B is primarily conservative. In the acute phase, this means intensive care: controlled hypotension, analgesics, close clinical and CTA monitoring.
-If treatment-resistant hypertension, unmanageable pain, sudden dilation of the aorta to >4 cm, hemorrhaging, or malperfusion are present, the first option is endovascular surgery. Ideally, this is performed more than 14 days after the onset of the dissection.
-Patients with chronic aortic dissection are always considered asymptomatic, never cured. They require regular lifelong follow-up.
Intramural hematoma (IMH): blood has entered the layers of the aortic wall, but neither intimal damage nor an entry point can be identified, and there is no detectable flow ins. In 50-85% of the cases, IMH develops in the distal thoracic aorta (Figure 5).
Penetrating aortic ulcer is an erosion of the atheromatous plaque of the aorta that reaches the elastic layer. This process often progresses to intramural hematoma, aortic dissection, or pseudoaneurysm.
Complicated IMH: unmanageable pain, increasing IMH, periaortic hematoma, intimal tears, progression
Complicated PAU: unmanageable pain, > 20 mm initial diameter and/or > 10 mm initial depth, involves all layers of the aortic wall, progression.
II/1. Patomechanism
The exact pathomechanism of these diseases is unknown. In case of PAU, the progression of atherosclerotic plaque, while for IMH, the injury of the vasa vasorum is suspected as causative factor.
II/2. Symptoms
Depending on the site of the lesion, strong thoracodorsal or abdominal pain and an increase in blood pressure characterizes both diseases.
II/3. Diagnosis
CTA or MRA is the first-choice imaging modality for both IMH and PAU.
II/4. Treatment
Similar to aortic dissection, PAU and IMH may also be divided into complicated and uncomplicated cases. In complicated cases, progression is much faster, and the risk of complications is higher. In uncomplicated cases, conservative treatment, as described under type B dissections, may be effective. Complicated cases require endovascular intervention (stent graft) or open surgery (if endovascular treatment is contraindicated).
II/5. Summary
-IMH and PAU most commonly occur in the distal thoracic aorta, and present a high risk of aortic dissection and rupture.
-The gold standard imaging diagnostic method is CTA or MRA
-In uncomplicated cases, conservative treatment is recommended; in complicated cases, endovascular surgery is preferred.