Transcript CBP: Aortic Dissection - UBC Critical Care Medicine, Vancouver BC

CBP: Aortic Dissection
Case
• A 64 year old man presents to the emergency
department complaining of sudden sharp 10/10
anterior chest pain with no radiation. His history is
remarkable for hypertension, and type II diabetes, but
no coronary artery disease or risk factors for venous
thromboembolism. His BP is 180/100 on the left, and
162/80 on the right, with no pulsus paradoxus. HR 110,
RR 22, O2 sat 96% on r/a, T 37.2. Physical exam shows
the patient to be in obvious discomfort, with a clear
chest, normal heart sounds, no murmur, and a normal
JVP. There are no focal neurological deficits. The
electrocardiogram shows evidence of LVH, but no other
abnormality. The chest x-ray is on it’s way.
Question 1
• Please go over the ddx of chest pain
Differential diagnoses of Pt admitted to
hospital with acute chest discomfort
G.I. disease
42%
Ischemic hearth disease
31%
Chest wall syndromes
28%
Pericarditis
4%
Pleuritis/Pneumonia
2%
PE
2%
Lung cancer
1.5%
Aortic aneurysm
1%
Aortic stenosis
1%
Herpes zoster
1%
Approach to the patient with
chest discomfort
•Stable/unstable
•Symptoms
•Physical examination
•ECG
•Lab works
•Imaging
The importance of hystory
•Duration of symptoms (i.e. angina 2-10
min, AMI > 30 min, aortic diss abrupt onset)
•Quality of symptoms (i.e. AMI heaviness,
sharp in pericarditis, ripping sens in AD)
•Location (i.e. retrosternal with irradiation in
AMI,interscapular for AD)
Physical examination
• General Appearance
– may suggest seriousness
of symptoms.
• Vital signs
– marked difference in blood
pressure between arms
suggests aortic dissection
• Palpate the chest wall
– Hyperesthesia may be due
to herpes zoster
• Complete cardiac
examination
– pericardial rub
– signs of acute AI or AS
– Ischemia may result in MI
murmur, S4 or S3
• Determine if breath
sounds are symmetric
and if wheezes, crackles
or evidence of
consolidation
Labs
•Troponin
•CK-MB
•Myoglobine
Imaging
•
•
•
•
CXR (i.e. pneumonia, pnx, AD)
CT (i.e. AD, PE)
TEE (signs of pulmonary hypertension, AD)
Aortogram (AD)
Question 1
• Describe the most common classification
systems of aortic dissection (Todd)
Classification systems for Thoracic Aortic
Dissections
• Time course: Acute vs. Chronic
• Anatomical: Ascending, descending or both
• Stanford:
– Type A: Involving the ascending aorta (with or without
descending aortic involvement)
– Type B: Involving only the descending aorta
• De Bakey:
– I: Ascending and Descending aorta
– II: Ascending Aorta only
– III: Descending Aorta only
Question 2
• Describe the pathophysiology of aortic
dissection. (Ibrahim)
Pathophysiology of AAS
Classic Aortic Dissection (AD)
Antegrade Propagation of AD
Retrograde Propagation (Type A)
Intramural Hematoma (IMH)
Penetrating Atherosclerotic Ulcerations
Question 3
• List the major predisposing factors for aortic
dissection. (Noemie)
Risk Factors
Most common RF
Peak incidence in
60-70s
M:F =2-5:1
Found in 714% of all
dissection
Most common in
3rd trimester
Iatrogenic: 5% of all cases, Cardiac cath, AVR.
Trauma @ aortic isthmus
Question 4
• List the most common signs and symptoms of
aortic dissection, and highlight the ones which
have shown the best positive and negative
likelihood ratios. (Erik)
Aortic Dissection
Case Based Presentation:
• Utility of Hx, P/E, and CXR
• Complications of therapy
List the most common signs and
symptoms of aortic dissection,
and highlight the ones which
have shown the best positive
and negative likelihood ratios.
Klompas, JAMA, 2002
The “naked” truth
• Majority of data derived from retrospective
chart reviews.
• Significant selection bias – falsely inflating
both sensitivity and specificity.
• Do not reflect contemporary practice (lower
threshold to scan with 64-MDCT, triple ruleout, etc.)
History
• Most patients with [spontaneous] thoracic
aortic dissection have severe pain of abrupt
onset.
• The absence of pain of sudden onset
substantively decreases the probability of
dissection (negative LR, 0.3; 95% CI, 0.2-0.5);
however, the study design of the reports
precludes accurate assessment of the
sensitivity and specificity of these features.
Physical
• Pulse deficits (positive LR, 5.7; 95% CI, 1.423.0) or focal neurological deficits (positive LR,
6.6-33.0) greatly increase the likelihood of
thoracic aortic dissection in the appropriate
clinical setting.
• The presence or absence of a diastolic
murmur is not useful (positive LR, 1.4;
negative LR, 0.9).
CXR
• A normal aorta and mediastinum on chest
radiograph helps exclude the diagnosis
(negative LR, 0.3; 95% CI, 0.2-0.4) but no
particular radiographic abnormality is
dependably present.
Bare bottom…
• Clinical history, examination, and radiography
can help rule in aortic dissection but are not
sufficiently accurate to rule out the disease.
Question 5
• List the main complications associated with
acute aortic dissection, and briefly explain
how they occur. (Neil)
• Q: List five complications arising from aortic
dissection.
Royal college question:
• List 5 major complications of aortic dissection
Main complications
• 30 % get ischemic complications
• In type I mortality due to complications
increases 1% per hour
• Etiology
– Dynamic obstruction
• Occlusion of true lumen by false lumen
– Static obstruction
• Compression, disruption, thrombosis
List of main complications
• Tamponade
• Acute severe Aortic
insufficiency
• MI
• CVA
• Spinal infarct/paraplegia
• Aortic rupture
• Mesenteric/Renal/Limb
ischemia
• Pseudoaneurysm
Acute Severe Aortic Insuficiency
• Widening of sinotubular
junction causing improper
coaptation
• Diastolic leaflet prolapse from
detachment of aortic leaflet
commisural attachment
• Intimal prolapse
• Murmur is typically heard over
R sternal border
Acute MI
• Occurs in 5 % of Type I
dissections
• Usually involves R
coronary
• Often presents as
complete heart block or
inferior /R sided MI
• Mortality if you
thrombolyse approaches
70%
Neuro complications
• CVA
– 10% of type I’s
– Carotid occlusion
– 5-10% of dissections present with syncope
• Spinal
– Intercostal arteries
– Artery of Adamkiewicz
– Can recover if treated early
Case cont’d…
• The patient’s chest x-ray shows a wide
mediastinum. In the meantime, the patient
reports that he is in agony, and his BP rises to
200/120 on the left.
Question 6
• What is the sensitivity and specificity of CXR
for aortic dissection? List three CXR findings
associated with the condition. (Federico)
CXR
• Sensitivity 60-90%
• Specificity 70%
CXR FINDINGS
•Widening of the mediastinum (63%
type A, 56%type B)
•Doubled shadow of the aortic wall
•Disparity of the size in the ascending
and descending aorta
Question 7
• List the various modalities (other than chest xray) that can be used to diagnose aortic
dissection, noting the sensitivity/specificity,
advantages, and limitations of each (Omar)
Imaging modalities
• TTE, TEE, CT, Aortography
• Perform better in high risk populations
Aortography
• Specificity/Sensitivity: 94% / 88%
• Pros:
– Identify site of origin, branch artery involvement, AI,
coronary extension
• Cons:
– Lengthy, large dye load, $$
– invasive,
– May fail to identify intramural hematoma
Computed Tomography
• Sensitivity/Specificity: 83-100% / 87-100%
– Probably even better with newer generation,
helical, multislice scanners
– Accuracy may approach 100%
Computed Tomography
• Can identify:
– intimal flap, branch vessel involvement, extent of
dissection, false lumen patency, aortic size,
pericardial effusion, end organ ischemia
• Non-invasive
• Cons:
– Contrast material, cannot detect AI or visualize
coronary artery dissection
MRI
• Sensitivity/Specificity: 95-100% / 98%
• Pros:
– Less nephrotoxicity (Gadolinium)
– Non invasive
– Excellent visualization
– New techniques allow for fast scan times (4 mins)
MRI
• Cons:
– Lengthy
– Availability
– Metallic hardware
– Difficult to monitor
ECHO - Transthoracic
• Sens/Spec: 77-80% / 93-96%
• Pros:
– Fast, inexpensive, available
• Cons:
– Operator dependant
– Can only evaluate the aortic root and arch
– Distal ascending Ao and descending Ao not
assessed
– Low sensitivity
ECHO - Transesophageal
• Sens/Spec: 100% / 95%
• Pros:
– Rapid
– Bedside test
ECHO - Transesophageal
• Cons:
– Cannot visualize abdominal aorta
– Sedation
– Relative CI’s: Chest trauma, varices, strictures,
tumours
– “Blind spot”
• Right main stem bronchus obscures visualization of part
of ascending aorta
Case cont’d
• You’re now convinced this guy is dissecting,
and decide to start treatment while waiting
for the chest CT.
Question 8
• Outline the principles behind medical
management of aortic dissection, and explain
the physiologic rationale of “anti-impulse”
therapy. (Todd)
It’s not just blood pressure…it’s poor
impulse control!
• dP/dt
– Change in pressure per
Unit of time
Anti-impulse therapy
• Negative inotropy (and thus rate of rise of blood
pressure, as well as mean and peak systolic pressure)
• Negative chronotropy (fewer peak systolic pressures
for the vulnerable vessel to experience)
• Alpha blockade (prevent compensatory
vasoconstriction)
Goal blood pressure: as low as possible without
inducing organ failure….Systolic BP of 100, or MAP of
60-70.
No great evidence; this would be a tough population to
ethically randomize.
Pharmacologic options: with invasive
monitoring
• Esmolol: Beta blocker, bolus and infusion options
– 1 mg/kg (usually about 80 mg) bolus
– 150-300 mcg/kg/min
• Labetalol: alpha-antagonistic properties
– 20 mg IV bolus (may require up to 80 mg over 10 min)
– 0.5-6 mg/min infusion
• Propranolol: 1-10 mg bolus, followed by 3 mg/hr
Others
• Nitroprusside: beware cyanide toxicity (at about 500
mcg/kg). Do not use without beta-blockade (reflex
tachycardia)
– 0.5 mcg/kg/min, titrate in 0.5 increments to max 10
mcg/kg/min
• ACE inhibitors may be used, but given the high risk of renal
failure, and unreliable gut function depending upon the
course of the dissection, they would not be plan A.
• For patients who cannot tolerate beta blockers, non-DHP
calcium channel blockers (verapamil or diltiazem) are viable
options.
• 4. Quit eating fast food and check into rehab.
Again.
Case cont’d
• You start an esmolol infusion and order morphine
for his pain. You insert an arterial line into his left
radial artery and decide to walk over to CT to talk
to the radiologist.
• On your way back from CT, you notice that the
patient’s pressure is now 87/68 with a heart rate
of 120, and large respiratory variations. When
you ask the nurse how much esmolol the patient
is on she tells you that she only gave the
morphine before his pressure dropped.
Case cont’d
• On exam, the patient appears confused, has
distended neck veins, muffled heart sounds,
and is peripherally cool. You put the echo
probe on his chest and note a moderate-sized
pericardial effusion with right atrial and
ventricular diastolic collapse. You order a
bolus, ask for a cardiac needle, and call the
cardiac surgeon who organizes the OR and
intraop TEE, and strongly advises against
pericardiocentesis.
Question 9
• Explain why pericardiocentesis may worsen
outcome in cardiac tamponade secondary to
proximal aortic dissection. (Neil)
• If open communication with aortic root then
pressure rises quickly and results in PEA and
pericardiocentesis likely useless
• BUT, not everyone dies SO….
– Blood in pericardium leaks back through false
lumen
– Communication in some cases is transient
• Stops due to thrombus or intimal flap
Pressure is the key
• As tamponade increases the pressure
gradient between the false lumen and the
pericardium decreases which results in stasis
and thrombus formation.
• Tamponade also compresses the ventricles
decreasing BP and dP/dT which reduces
propagation of dissection
So why is a needle bad?
• By releasing tamponade you
– Increase BP and dP/dT which can worsen
dissection
– Increase the gradient between the false lumen
and pericardial space which may release thrombus
or flap and result in an open communication with
aorta
• Both result in PEA which is usually non
recoverable
Summary
• If stable, get to OR ASAP
• If unstable, do pericardiocentesis, but
consider only removing enough blood to
maintain hemodynamic stability until the OR
Question 10
• In what settings may it be preferable to delay
or completely forego surgery in type A
dissections? (Noemie)
Type A dissection
• Ascending aortic dissection --> surgical emergency
• Mortality 90% at 2 weeks if treated non-surgically 1
• Most common cause of death in Int Reg of A.A.D.
was aortic rupture and visceral ischemia
Circulation 2000; 102(19Suppl3):248-I252
Contraindications
• Stroke
– Relative contraindication
– concerned about transformation into hemorrhagic
stroke with anticoagulation and reperfusion
Ann Thorac Cardiovasc Sur 2009, 15(5):285-293
Contraindications
• Delayed presentation: 48-72HR
– Can optimize clinical condition prior to surgery
Ann Thorac Surg 2007;83:1593-1602
Contraindications
• Prior AVR
– Can operate semi-electively
– Protected against AI
– “Dissection cannot cross a
suture line” 1
– RCA is protected by suture
– Adhesions decrease chance of free rupture in
pericardial sac
1. Ann Thorac Cardiovasc Sur 2009, 15(5):285-293
Contraindications
• Comorbidities:
– Age, ARF, shock, redo surgery
– If high risk surgery , could consider medical
management
Ann Thorac Surg 2007;83:1593-1602
Question 12
• What are the indications for intervention in
type B aortic dissection? (Ibrahim)
Indications for Intervention in
Type B
• Persistent Chest Pain
• Involvement of side branch compromising
vital organ perfusion
• Impending rupture (Rapid aortic expansion,
periaortic hematoma, hemomediastinum)
Endovascular Interventions
1. Branch vessel stent placement,
2. Percutaneous Aortic balloon Fenestration
(PAF),
3. Aortic stent placement,
4. Stent-graft placement over the intimal entry
tear restores normal blood flow in the true
lumen and induces thrombosis of the false
lumen
Indications for PAF
• (1) Mesentric ischemia;
• (2) Renal failure or pain due to renal artery
obstruction;
• (3) Severe renovascular hypertension, which is
difficult to control medically secondary to renal
artery obstruction;
• (4)Paraplegia or paraparesis due to spinal artery
involvement;
• (5) severe peripheral ischemia with rest pain or
severe claudication
Pawan et al, Ther Adv Cardiovasc Dis, 2008
Case cont’d
• The patient goes to the OR where the TEE shows a
dissection of the proximal aorta with mild aortic
insufficiency, and a pericardial effusion with evidence
of tamponade physiology. An urgent median
sternotomy is performed and a tense pericardium is
noted. After the patient is placed on cardiopulmonary
bypass, the pericardium is opened, revealing a
substantial amount of organized thrombus and blood.
Further examination reveals a short, circumferential
dissection of the proximal ascending aorta (see figure).
Case cont’d
• The aortic root and valve were replaced with a
stentless bioprosthetic composite graft, and
the patient comes off-pump easily. The CSICU
is full, and you agree to accept the patient to
the ICU post-op.
Question 12
• What are the main complications that occur
post thoracoabdominal aortic surgery? (Erik)
Complications
following
Thoracoabdominal
aneurysm repair
by system involved
Respiratory Failure
• Although there is continued focus on spinal
cord ischemic injury and postoperative renal
failure, postoperative respiratory failure
remains the most commonly reported
complication in the many published series.
• Multiple etiologies: lung isolation, postthoracotomy, diaphragmatic injury, phrenic
nerve injury, TRALI, ARDS, etc.
Renal Failure
• Pre-AKIN/RIFLE classification.
• In one analysis aortic cross-clamp time >100 minutes
was the single intraoperative variable associated with
postoperative renal failure (Kashyap et al., 1997).
• Intraoperative hypotension (SBP <70 mm Hg for > 10
mins) trended toward significance with regard to
postop renal failure, but was only significant in
association with perioperative death.
• Patients who experienced postoperative renal failure
had an approximately 10-fold increased risk of
perioperative death.
Neurological Events
• Spinal cord injury of any sort remains one of the
greatest fears after thoracoabdominal aneurysm
repair.
• Spinal cord injury is divided into immediate
deficits and delayed deficits. Delayed-onset
deficits continue to occur in some 10% of
patients, and although these are often partial and
reversible and with acceptable functional
outcomes, continued vigilance to perioperative
care, especially the avoidance of hypotension.
Cardiovascular Events
• Cardiovascular complications occur in ~14% of
patients:
– myocardial infarction 4%
– arrhythmia 8-10%
– congestive heart failure 2%
– unstable angina <1%
• Standard clinical management.
Question 13
• How would you manage a patient with signs
of paraplegia post-thoracoabdominal aortic
surgery? (Omar)
Paraplegia
• Nothing earth shattering here…
• Try to correct, or at least limit, amount of
ischemia to the cord
– Increase MAP
– Decrease spinal ICP
Paraplegia
• Increase MAP till neurologic recovery is seen
or limit of MAP reached
– Safe upper limit of MAP defined by surgeon
– Volume resuscitate
– Transfuse, as needed
– Liberal use of inotropic support
• Esp with neurogenic shock
• May require high doses
Paraplegia
• Lumbar CSF drains
– ICP goal of 8 – 12
– Cap at 12 – 24hrs
– Remove at 36 – 48 hrs