Aortic dissection Flashcards
Discuss risk factors for the development of dissection
Structural aortic abnormalities
- Bicuspid aortic valve – interferes with laminar flow and reorients the flow of blood towards the aortic wall
- Aortic coarctation
- -Connective tisseu disorder (marfans, loeys dietz, Ehlers-Danlos syndroms)
- HTN (including that mediated by cocaine or other mechanisms)
- Atherosclerosis
- Prior cardiac sugery
- known aneurysm
- prior aortic surgery
-pregnancy
Vascultis
Discuss briefly pathophysiology
– progressive weakening of vasomedia leads to increase movement with normal heart beat
leads to tear in intama
haematoma can propagate either retro or antegrade
Discuss classifications of dissection
Standford classification is the most commonly used system
-Type A dissections involve the ascending aorta and account for approximatly 62% of all dissection
Type B involve only the descending aorta
Type A dissection are more often lethal - and call for a different management than those confined to the distal aorta
Debakey classification based on orgin and propogation
Type 1- orginated in the acending aorta and propogates at least to the arch
Type 2- originated and is confined to the ascending aorta
Type 3- originated in the descending aorta and propogates distally
Acute - less than 2 weeks
Sub acute 2-6 weeks
Chronic >6 weeks
Discuss clinical features of aortic dissection
Pain is the most common symptom - excruciating, occurs abruptly and is most severe at onset - described as sharp more often than tearing or ripping
Migratory pain is consistent with dissection
-Anterior chest pain is associated with the ascending aorta, neck and jaw pain with the arch and interscapular pain with the descending aorta
Syncope occurs in 9% of dissection cases
Neurological symptoms such as focal weakness or change in mental state occur in up to 17% of cases
Aortic regurg occurs in up to 32% of pateints and is more common with type A dissections -
Should examine for haemorrhage or tamponade
Pulse pulse deficts can be helpful but if present only have around a 30% sensirtivity
In up to 3% of cases a proximal dissection can dissect into the ostium of a coronary vessel can cause myocardial ischaemia – usually right ostium leading to inferior posterior infarct
Discuss Ix of dissection
-ve D-dimer suggest dissection is an unlikley diagnosis
ADviSED trial
ECG- exclude features of MI
-LVH signs are also present in 26% of cases reflected long standing HTN
CXR- abnormal in 80-90% of cases – rarely specific or diagnostic
- mediastinal widening is present in up yo 61% of cases - may occur in any portion of the aorta and may be difficult to differentiate from aortic tortuosity
- Double density appearance of the aorta suggesting true and false channels
- – localisezed buldge along a normally smooth aortic contour
- – doisparity in the caliber between the descending and ascending aorta
- obliteration of the arotic knob
- displacement of the trachea or NGT to the right by dissection
ECHO - Insensitive for detecting aortic dissection as it does not visualize the aortic arch or much of the descending
- can exclude pericardial effusion or tamponade physiology
- TOE is sensitive for detecteding aortic dissection (98 sens,95 spec)
CT- Reliable with high sens (100%) and spec (98%)
-Finding suggestive of dissection include dilation of the aorta, indentification of an intamal flap and clear demonstration of the flase and true lumens
MR- 98% sens and spec
Discuss management of dissection
ABCD
Pain– opioid pain relief - controlls pain and reduces sympathetic outflow
The aim of therapy in aortic dissection is twofold
1) reduce HTN – patient are most often HTN
2) decrease rate of rise of arterial pulse to diminish shearing forces
-Target BP of 100-120mg systolic and heart rate of <60 is a good target
B-blockers are the mainstay of treatment - isolated vasodilators such as SNIP reflexively increase HR and require co-comittent B blockade
Esmolol and labetalol are titratable short acting beta blockers which are affective in dissection
- esmolol given as a bolus of 500 mic/kg followed by infusion of 50mic/kg/min to a max of 200mic/kg/min- often require vasodilating agent to augment HTN effects
- Labetalol has both alpha and beta affets - given as an initial serious of 20mg IV boluses every 10-20 minutes incrementally increased to a max of 80mg IV until a heart rate of 60 or 300mg is given - maintenance infusion of 1-2mg/min given after this
- if patient normotensive should still have blockade to maintain HR of 60
SNIP at a initial infusion dose of 0.5-3mic/kg/min is the first line vasodilator – necessatates b blocker use concomitantly
GTN inferior as has less arterial dilation
Nicardipine can be used as an alternative second line agent in those who tolerate b blockade poorly – nil inotropic depressent and minimal reflex tachyardiqa
Discuss operative and intervention repair
Type A dissection require prompt surgical intervention - the aortic segment containing the original intimal tear is resected when possible with graft replacement of the ascending aorta to redirect blood flow into the true lumen - in hospital mortality rate of 27% surgically treated compared to 56%^ with medical management
Type B intervention is less clear - they are categorized into two groups based on associated symptoms
- complicated - any dissection with end organ ischaemia, leaking or rupture, aortic dilation or intractable pain
- uncomplicated stable asymptomatic patients
Complicated type B are traditional.y treated surgically although in the past decade this practice has been challenged - thoracic endovascular aneurysm repair (TEVAR) have been replacing surgery for complicated type B dissection
Indications for surgical repair/endoluminal stenting in type B
- Leaking or ruptured aorta
- End organ ischaemia
- extension of dissection despite appropriate medical therapy
- refractory pain
- severe uncontrollable HTN
Uncomplicated Type B are treated conservatively
Discuss disposition
Talk to vascular about everyone - type A need urgent referral
Type B chronic or subchronic have already survived they period of highest mortality
Discuss Aortic dissection detection risk score
Decision making tool for CTA vs stoping workup for Aortic dissection
Score if any of the following
1) Any high risk condition
- Marfan syndrome
- family history of aortic disease
- known aortic vlave disease
- recent aortic manipulation
- Known TAA
2) ANy high risk pain feature
- chest back or abdo pain described as abrupt onset, severe intensity or ripping/tearing
3) Any high risk exam feature
- evidecne of perfusion deficit (pulse pulse deficit, systolic BP differential, of focal neuro deficit plus pain)
- new aortic insufficiency murmur
- Hypotension or shock
If 1 or less and d-dimer >500 can stop, other wise CTA if 2 or more CTA without d-dimer
