Aortic Dissection

Aortic dissection is caused by a transverse tear in the intima of a vessel. The dissection usually propagates distally, but sometime it may also propagate proximally. It is more common in males than in females and often occurs at 40–60 years of age

Risk Factors/Associations

• Systemic hypertension (70%)
• Marfan’s syndrome
• Bicuspid aortic valve
• Cystic medial necrosis,
• Coarctation of aorta
• Cocaine abuse
• The third trimester of pregnancy
• Blunt chest trauma

Stanford classification of Aortic dissection

• Type A-dissection involving the ascending aorta
• Type B-dissection limited to descending aorta

Clinical Features

• Sudden onset of severe and tearing pain in the front or back of the chest, often in the interscapular area.
• Patients are typically hypertensive. If hypotensive, consider pericardial tamponade, hypovolemia from blood loss, or other cardiopulmonary causes.
• Asymmetrical pulses and blood pressure in the upper limbs.
• Syncope, dyspnoea, and weakness.
• Pts with aortic dissection &/or progressive aortic root dilation can develop aortic regurgitation murmur
  heard best at the left lower sternal border with pt sitting up and leaning forward and holding the breath after full expiration—aortic dissection murmur is heard better on the right sternal border compared to left for primary valvular disease.
• Complication
  • Stroke (carotid artery)
  • Acute Aortic Regurgitation (aortic valve)
  • Hemothorax (pleural cavity)
  • Abdominal pain ( mesenteric artery)
  • Cardiac tamponade (pericardial cavity)
  • Acute Myocardial infarction (coronary artery)

Investigations to confirm aortic dissection

• CXR
  • Findings include widening of the mediastinum and a small left-sided pleural effusion,
• EKG to differentiate from acute myocardial infarction. It shows non-specific ST-T wave changes.
• TEE (Transesophageal Echocardiography) has excellent sensitivity and specificity and is the preferred
  diagnostic study in patients with renal insufficiency or hemodynamic instability.
• CT angiography is the preferred diagnostic study in hemodynamically stable patients; however, it
  requires the use of iodinated contrast agents and should be avoided in patients with renal
  insufficiency. It can reveal an intimal flap separating the true and false lumens In the aorta.
• MR angiography is time-consuming and requires the administration of gadolinium-containing
  contrast agents for contrast enhancement; it should also be avoided in patients with moderate
  to severe renal disease due to the risk of nephrogenic systemic fibrosis.

Treatment

• Type A dissection is preferably treated by emergency surgery
• Type B dissection that is stable is preferably treated by medical measures

• Parenteral administration of a B-blocker is used
• If B-blockers are contraindicated, parenteral CCB  may be used.
• If B-blockers can’t control BP, vasodilators (e.g. sodium nitroprusside or nitroglycerine) may be used.
• Hydralazine and nitroprusside are vasodilators sometimes used in hypertensive emergencies. However, they can cause reflex sympathetic stimulation with consequent rises In heart rate, LV contractility, and aortic wall stress. These changes increase the risk of propagation of a dissection. In patients with aortic dissection, nitroprusside is used as a second-line agent only if SBP remains above goal despite adequate beta-blockade.
• Direct vasodilators (diazoxide and hydralazine) are contraindicated because they increase the force of the left ventricular ejection.
• Avoid using thrombolytics

References

1.https://doi.org/10.1016%2Fs0140-6736%2814%2961005-9