Makindo Medical Notes

Related Subjects: |Assessing Chest Pain |Acute Coronary Syndrome (ACS) General |Aortic Dissection |Pulmonary Embolism |Acute Pericarditis |Diffuse Oesophageal Spasm |Gastro- oesophageal reflux |Oesophageal Perforation Rupture |Pericardial Effusion Tamponade |Pneumothorax |Tension Pneumothorax |Shingles

The most critical step is to consider the diagnosis of aortic dissection in any patient presenting with chest pain, ensuring it is not misdiagnosed as the far more common myocardial infarction (MI) or pulmonary embolism (PE). Acute anticoagulation treatment for PE or MI can be harmful in aortic dissection, increasing the risk of life-threatening bleeding. Early recognition and appropriate intervention are key, as many cases will require urgent surgical intervention.

Tearing, stabbing rip
Intima has lost its grip
Swift rift prunes each branch
Wide aortic silhouette
CT now to detail threat      
@DrCindyCooper

Aortic dissection should be considered as a potential cause of chest pain or cardiac arrest in late pregnancy and the postpartum period, along with PE. Point-of-care ultrasound (POCUS) can be highly useful in these scenarios.

About Aortic Dissection

• Aortic dissection has a high mortality rate, with approximately 40% of cases being fatal at onset and 10% dying during or immediately after surgery.
• If suspected, an urgent CT Aortogram is essential. Blood pressure should be controlled immediately, especially for Type A dissections.
• Type A dissections require urgent transfer to a cardiothoracic center for surgical repair.
• Reducing the systolic pressure wave (dp/dt) with beta-blockade is crucial to minimize further dissection.
• Chronic aortic dissection, though rare, can develop over several weeks with symptoms of persistent pain or signs of progressive heart failure.

Aortic Anatomy

Aetiology

Younger patients often have connective tissue disorders, while older patients typically present with hypertension or atherosclerosis.

• The aorta is composed of three layers: intima, media, and adventitia.
• A dissection occurs when a tear in the intima allows blood to enter the media layer, creating a false lumen alongside the true lumen.
• Dissections are classified into:
  • Type A: Occurs within a few centimeters of the aortic valve and affects the ascending aorta.
  • Type B: Begins distal to the left subclavian artery, affecting the descending aorta.
• Dissections may extend:
  • Antegrade: Toward the aortic arch and beyond, causing damage to distal branches.
  • Retrograde: Back toward the aortic valve, potentially leading to aortic regurgitation, coronary involvement, or tamponade.
  • Rupture: May result in left-sided pleural effusion and sudden death.
  • Re-entry into the lumen: Blood may re-enter the true lumen, which can stabilize the dissection.

Stanford Classification

• Type A: Involves the ascending aorta and accounts for about two-thirds of cases. Requires urgent surgical intervention.
• Type B: Involves the descending aorta and is typically managed medically with blood pressure control.

DeBakey Classification

• Type I: Originates in the ascending aorta and extends to the aortic arch or beyond. High mortality, often in younger patients.
• Type II: Confined to the ascending aorta. Typically seen in elderly patients with hypertension and atherosclerosis.
• Type III: Begins distal to the left subclavian artery, confined to the descending aorta.

Pathology

Risk Factors

• More common in men than women, and typically occurs in patients over 60 years old.
• Associated with hypertension, atherosclerosis, and connective tissue disorders (e.g., Marfan's syndrome, Ehlers-Danlos syndrome).
• Risk factors include trauma, bicuspid aortic valves, prior cardiac surgery, cocaine use, and pregnancy (third trimester).
• Genetic predispositions and conditions like aortitis (e.g., Takayasu's, giant cell arteritis) also increase risk.

Clinical Presentation

• Suspect aortic dissection in patients with sudden onset of severe, sharp, or "tearing" chest pain radiating to the back.
• Patients often appear acutely unwell, with signs of shock or hypertension.
• Blood pressure may differ significantly between arms.
• Aortic regurgitation murmur and pulmonary oedema may indicate involvement of the aortic valve.
• Syncope is present in approximately 15% of cases due to involvement of major vessels or tamponade.

Complications

• Type A: Proximal dissection can cause:
  • Aortic rupture, cardiac tamponade, or sudden death.
  • Acute aortic regurgitation, leading to heart failure.
  • Stroke due to carotid artery involvement or shearing of the origin of the head and neck vessels.
• Type B: Distal dissection may cause:
  • Spinal cord infarction ("spinal stroke").
  • Mesenteric or renal ischaemia.
  • Left pleural haemothorax, indicating potential rupture.

Investigations

• Blood Tests: U&E, FBC, LFTs, group and cross-match for potential surgery.
• CXR: May show a widened mediastinum or left pleural effusion.
• ECG: May show signs of myocardial ischaemia, especially if the right coronary artery is involved.
• D-Dimer: Often elevated; a normal level may help exclude dissection.
• CT Aortogram: Gold standard for diagnosing aortic dissection, visualizing true and false lumens.
• TOE/TEE: Useful in unstable patients for rapid diagnosis.

Management

• Initial Approach: ABCs, establish IV access, administer oxygen, and monitor closely.
• Analgesia: Manage severe pain with IV morphine 2.5-5 mg.
• Blood Pressure Management: Use IV Labetalol to control BP and reduce shear forces (dp/dt). Nitroprusside may be added if needed.
• Type A Dissection: Requires urgent surgical intervention; time to surgery directly impacts mortality.
• Type B Dissection: Usually managed medically with aggressive BP control using beta-blockers and ACE inhibitors.
• Endovascular Repair: Preferred approach for Type B dissections, using stents to seal the false lumen.

References

• 2014 ESC Guidelines on the Diagnosis and Treatment of Aortic Disease