Acute Aortic Dissection
1/10/10
FANZCA Study Notes
OHOA page 340-342
Golledge, J (2008) “Acute Aortic Dissection” Lancet 372 pages 55-66
PY Mindmaps
-
the most common catastrophe of the aorta
3 times more common than AAA rupture
3:100,000
type A = involving the ascending aorta -> brachiocephalic artery (surgical treatment)
type B = arch and descending aorta (medical treatment)
surgical repair of arch requires a deep hypothermic arrest
‘cystic medial necrosis’ = pathological finding
HISTORY
- chest pain (ripping, tearing in nature, sudden onset, maximal @ onset)
- anterior chest pain – anterior dissection
- interscapular pain – descending aorta
- severe pain (‘worst ever-pain’)
- sudden onset
- migrating pain
- end-organ symptoms: neurological, syncope, limb paraesthesias, pain or weakness, flank
pain, SOB + haemoptysis
- AR
- HT
- most have IHD
RISK FACTORS
- vascular disease risk (HT, smoking, hyperlipidaemia, old age, previous vascular surgery)
- connective tissue disorders (Mafans, Ehlers-Danlos, Turners, adult polycystic kidney
disease)
- structural anomalies (bicuspid valve, coarctation, vasculitis)
- pregnancy
- recent cardiac catherisation (iatrogenic)
- complications: aortic rupture, AR, AMI, tamponade, end-organ ischaemia
EXAMINATION
-
AR common
hypertension
shock – ominious signs: tamponade, hypovolaemia, vagal tone
heart failure
neurological deficits: limb weakness, paraesthesiae, Horners syndrome
SVC syndrome – compression of SVC by aorta
assymetrical pulses (carotid, brachial, femoral)
haemothorax
Jeremy Fernando (2011)
INVESTIGATIONS
- leukocytosis
- Cr elevation with renal artery involvement
- TNT elevated if dissection causes myocardial ischaemia
- D-dimer – if negative very unlikely
- X-match
- CXR: widened mediastinum (60%), abnormal aortic contour (50%), normal
- ECG: normal, inferior ST elevation c/o right coronary dissection
- work currently being done on biological markers (elastin fragments, d-dimer, smooth
muscle myosin heavy-chain protein)
- TTE: good for AR and tamponade
- TOE: upper ascending aorta and arch not well visualised
- CT aortogram
- MRI
CT vs TOE vs MRI vs Aortogram
Advantages
Disadvantages
CT
- easy availability in emergencies
- high sensitivity and specificity
- assess complications (ischaemic
gut, tamponade, dissection or aorta)
- easier to monitor vs MRI
- quicker than MRI
-
remote location
iodinated contrast
can’t assess AR, LVF or coronaries
radiation exposure
TOE
- bedside
- can detect intimal flap, true and false
lumen, AR, tamponade
- can assess LV function
- no contrast needed
-
semi-invasive
may need anaesthesia/intubation
may cause hypertension
not widely available
special expertise required
oesophageal trauma
doesn’t quantify distal complicat.
MRI
-
- not readily available
- inconvenient (> 30 min)
- limited access and monitoring
- limited applic. (claustrophobia,
pacemakers)
Aortography
- detection of intimal flap and AR
- assess LV function, tamponade, blocked
coronaries)
high sensitivity and specificity
Gadolinium contrast better safety profile
can detect AR
no radiation exposure
cardiac MRI could also be performed
-
not readily available
invasive
contrast load
remote location
CLASSIFICATION
Stanford
A – ascending aorta affected
B – ascending aorta not affected
De Bakey
Jeremy Fernando (2011)
1 – entire aorta affected
2 – confined to the ascending aorta
3 – descending aorta affected distal to subclavian artery
Svensson
1
2
3
4
5
–
–
–
–
–
classic dissection with true and false lumen
intramural haematoma or haemorrhage
subtle dissection without haematoma
atherosclerotic penetrating ulcer
iatrogenic or traumatic dissection
MANAGEMENT
- emergency priorities:
(1) control BP
(2) control bleeding
(3) fluid resuscitation
- type A – surgery, type B – medical unless evidence of rupture, end-organ ischaemia,
uncontrollable HT (?endoluminal repair)
- O2
- wide bore IV access (Swan sheath)
- invasive monitoring
- warn blood bank (x-match 6U + need for other products)
- control HR and BP (aim for P 60-80 and BP 100-120 SBP)
- vasodilators (GTN, labetalol, hydralazine, SNP)
- call cardiothoracic surgeon
INTRAOPERATIVE
-
avoid hypertension on induction
fast, full and forward
dissection and clamps may interfere with arterial monitoring
TXA2
femoral arterial cannulation used for bypass
anticoagulate before bypass
if aortic root involved then patient may need AVR with coronary artery reimplantation
monitor BP after bypass closely
may have dissected into other organs (monitor function)
Circulatory Arrest
- deep hypothermic arrest (DHA) required during arch surgery as it isn’t possible to perfuse
cerebral vessels on bypass
- safe duration = 45min @ 18 C
- other ways of protecting brain; pack head with ice, thiopentone, methylprednisonlone
mannitol, GTN (to prevent vasoconstriction)
- POCD proportional to DHA time
- once circulation arrested -> all infusion and pumps stopped
- when warming do not set FAW to >10 C (prevents burns), start propofol and fix
coagulopathy with products
Jeremy Fernando (2011)
POST-OPERATIVE CARE
- standard care
Jeremy Fernando (2011)