Editing Aortic dissection


Most common catastrophic event affecting the aorta

== Definitions: ==

* Intra-mural haematoma - clinical picture of acute dissection but no blood flow in false lumen or any observable intimal lesions
** Manage same as acute aortic dissection

== Pathophysiology ==

* Intimal tear followed by blood surging antegrade (common) or retrograde (uncommon)
* Cleaves between intima and media, creating a false lumen
* Typical tear is transverse, not circumferential
* Fenestrations occur downstream at branch vessel ostia, allowing blood to re-enter the true lumen, and thus continue to flow through the false lumen
* Malperfusion syndromes
** The anatomy of the dissection dictates which arteries are malperfused
** The more compressed the true lumen is, the higher your index of suspicion for visceral and renal ischaemia should be
**

== Classification ==

* Temporal
** Acute - 14 days or less since onset of symptoms
** Subacute - 14-90 days
*** Best time to consider performing elective TEVAR due to pliable flap
** Chronic - >90 days
*** Flap stiff and fibrotic
* Anatomic
** '''DeBakey''' - original system in 1965 - based on origin of intimal tear and extent of dissection
*** Type I: Dissection originates in the ascending aorta, extends through the aortic arch, and continues into the descending aorta and/or abdominal aorta for a varying distance.
*** Type II: Dissection originates in and is confined to the ascending aorta.
*** Type IIIa: Dissection originates in the descending aorta and is limited to same.
*** Type IIIb: Dissection involves descending and variable extents of the abdominal aorta.
** '''Stanford''' - origin of entry tear alone
*** A: Involves any ascending aorta (proximal to brachiocephalic artery)
**** At Austin, managed by '''Cardiac Surgery'''
**** >60% of presentations are acute type A
*** B: originates in the descending aorta (distal to left subclavian artery)
**** Typically originates a few cm distal to subclavian, and the false lumen will be formed on the left posterolateral aspect of the aorta in 80%. This means the coeliac, SMA and right renal arteries will come off the true lumen, but the left renal comes from the false lumen. 
**** Complicated: rupture, impending rupture, malperfusion, refractory pain/hypertension
**** Uncomplicated = aggressive medical therapy
**** At Austin, managed by '''Vascular Surgery'''
** Debate over what to do with dissections originating between brachiocephalic and left subclavian arteries - neither cardiac nor vascular surgeons like them, it seems.
*

== Risk factors: ==

* Older age
** Type A peaks 50-60 yo
** Type B peaks 60-70 yo
* HTN (70%)
* Structural abnormalities of aortic wall
** Bicuspid aortic valve
** Coarctation of aorta
** Annuloaortic ectasia
** Chromosomal abnormalities
** Aortic arch hypoplasia
** Marfans/Ehlers-Danlos (present in 50% of dissections younger than 40)
* Men 4:1
* Most common between 6am-12pm
* Most common in winter
* Pregnancy, especially with pre-eclampsia
* Cocaine

== Presentation ==

* Pain: acute, severe, 10/10, tearing/ripping
** Present in 93%, with 85% reporting an abrupt onset.
** Mostly anterior for type A, back for type B
** Can localise in abdomen for any dissection
* Hypertension 
** 70% type B, 30% type A
** Often refractory to medical management
* Often listless, sense of impending doom
* Can be essentially painless
* Peripheral vascular complications
** Brachiocephalic trunk 14%
** Common carotid 21%
** Left subclavian 14%
** Ileofemoral 35%
** Check for BP difference between arms
* Atypical
** acute paralysis - spinal cord ischaemia in type B
** AKI
** syncope (cardiac tamponade/brachiocephalic involvement)
* Hypotension/shock = cardiac tamponade or dysfunction or ongoing haemorrhage
** Rare for type B

== Investigation ==

* CXR - non-specific, never diagnostic
** Widening of cardiac or aortic silhouette
** Displacement of aortic calcifications
** Pleural effusions - seen with type B, secondary to mediastinal inflammation
* CT
** Sensitivity 83-95%, specificity 87-100%
** Helical CT dissection protocol - CTA
** Look for slit-like compressed true lumen - much higher suspicion for renal/visceral/lower extremity malperfusion
** Performs slightly worse at picking up ascending dissections, very good for type B though

== Management of Type B dissections ==

* Prompt control of blood pressure, and intervene if there is malperfusion or a complication (although it sounds like there is growing evidence for doing TEVAR in more patients)
* Medical
** ICU
*** Art line
*** Telemetry
*** IDC
** The goal is to reduce haemodynamic forces on the flap
** Aim HR 60-70, SBP 100-110 (or mean of 70-70mmHg)
*** Use IV beta blockade, can add vasodilators to further control HTN
*** Avoid nitroprusside or hydralazine initially - increase shear forces in aorta - but can add them after the beta blocker
*** Do not give beta blockers if evidence of diastolic murmur aortic regurg on TTE (exacerbate CCF)
** If hypotension is present, consider complications:
*** Tamponade
*** Rupture
** Once blood pressure is normalised and pain resolved, consider transition to oral anti-hypertensives
** Repeat CT on discharge, then at 6 months. 

Open surgery

* Indications:
** Threatened or actual rupture at the aortic intimal tear in the proximal descending aorta, with no identifiable proximal seal zone
*** Confine resection to proximal descending aorta to prevent spinal cord ischaemia

* TEVAR
** Indications:
*** Rupture if anatomically conducive
** Goals:
*** Stent-graft coverage of the aortic entry tear
*** Induce false lumen thrombosis
*** Expand true lumen
*** Should prevent future aneurysmal degeneration of the outer wall too

== Complications: ==

* 12% of uncomplicated type B dissections who initially have medical therapy become complicated in the first 15 days
* Rupture
* Malperfusion syndromes
** Incidence 25-40%
** Treat with endovascular fenestration or open fenestration

== Follow-up: ==

* Once a dissection has been stable for two scans, it can be followed up yearly

== Prognosis ==

* Mortality of untreated acute dissection (type A and B):
** 22.7% at 6 hours
** 50% within 24 hours
** 68% at one week
* Type A dissections die from cardiac complications, while type B dissections die from visceral compromise
* Mortality with medical management of type B is 10% at 30 days and 10-30% at one year
* Consequence of medical therapy is aneurysmal degeneration of the false lumen outer wall in 40% of patients, and they may need repair

[[Category:Vascular]]