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

M:F =2-5:1Peak incidence in 60-70s

Most common RF

Found in 7-14% of all dissectionMost 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 DissectionCase 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 rule-out, 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, 1.4-23.0) 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 x-ray) 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 perUnit 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, post-thoracotomy, 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