Ch. 7 Chest and Back Pain

Question 1

What is the significance of an increased pulse pressure in aortic dissection?

Answer 1

Pts with aortic insufficiency will present with a widened pulse pressure. Diastolic pressure decreases due to regurgitation, while systolic pressure increases 2/2 increased SV as a result of backflow of blood from aorta (inc. preload)

Question 2

What is the initial event leading to an aortic dissection?

Answer 2

Progressive separation of aortic wall that results from tear in intima that progresses into media, essentially splitting aorta into inner layer of intima and inner media and an outer layer of outer media and adventitia.

Result: two lumens (true and false)

As blood flows into false lumen, the tear propagates and false lumen enlarges. Eventually, secondary tears may develop, which allow blood to reenter true lumen. The tear is a direct consequence of aortic wall shear stress.

Question 3

Why are patients with Marfan’s Syndrome at inc. risk for aortic dissection?

Answer 3

Marfan’s = CD disease that has AD mode of transmission

• Primary defect involves misfolding of fibrillin proteins, which can result in cystic medial necrosis of large vessels (i.e. aorta)

Question 4

How are aortic dissections classified?

Answer 4

• Debakey
  
  • Type I: Ascending and descending
  • Type II: Ascending ONLY
  • Type III: Descending ONLY
• Stanford
  
  • A: ascending aorta/aortic arch **REQUIRES SURGERY +/- Descending aorta distal to takeoff of L subclavian a
  • B: Descending aorta ONLY **NONOPERATIVE

Question 5

What is the first step in mgmt of an aortic dissection (pre-op tx)?

What is the post-op tx?

Answer 5

PRE-OP

Since high BP will propagate tear, it is critically important to maintain a low BP.. usually between 100 and 110 mmHg systolic. Best done with sodium nitroprusside & IV beta-blockers (decrase shear forces on aorta by decreasing dp/dt… change in pressure/change in time… i.e. esmolol).

** Patients with significant AR or tamponade should NOT receive bb ** (Will worsen hypotension –> cardiac arrest)

POST-OP

Lifetime control of BP and monitoring of aortic size

Question 6

1. What is the etiology? (6)
2. Note three other sequelae.

Answer 6

1. Etiology:
   
   1. HTN (most common)
   2. Marfan’s syndrome
   3. Bicuspid aortic valve
   4. Coarctation of the aorta
   5. Cystic medial necrosis
   6. Proximal aortic aneurysm
2. Three other sequelae:
   
   1. Cardiac tamponade; Beck’s triad (distant heart sounds, inc CVP with JVD, dec. BP)
   2. Aortic insufficiency–diastolic murmur
   3. Aortic arterial branch occlusion/shearing, leading to ischemia in the involved circulation (i.e., unequal pulses, CVA, renal insufficiency, bowel ischemia, claudication)

Question 7

1. What is the possible cause of MI in a patient with aortic dissection?
2. What is a dissecting aortic aneurysm?
3. What are the EKG signs of the following disorders:
   
   1. Atrial fibrillation
   2. PVC
   3. Ventricular aneurysm
   4. Ischemia
   5. Infarction
   6. Pericarditis
   7. RBBB
   8. LBBB
   9. WPW
   10. 1st degree A-V block
   11. 2nd degree A-V block
   12. Wenckebach phenomenon
   13. 3rd degree A-V block

Answer 7

1. Dissection involving the coronary arteries or underlying LAD
2. Misnomer! Not an aneursym!
3. EKG findings:
   
   1. Afib: irregularly irregular
   2. PVC: Wide QRS
   3. Ventricular aneurysm: ST elevation
   4. Ischemia: ST elevation/ST depression/flipped T waves
   5. Infarction: Q waves
   6. Pericarditis: ST elevation throughout leads
   7. RBBB? wide QRS and “rabbit ears” or R-R in V1 or V2
   8. LBBB? wide QRS and “rabbit ears” or R-R in V5 or V6
   9. WPW: Delta wave = slurred upswing on QRS
   10. 1st: Prolonged P-R interval (0.2 sec)
   11. 2nd: Dropped QRS; not all P waves transmit to produce ventricular contraction
   12. Wenckebach: 2nd degree block with progressive delay in P-R interval prior to dropped beat
   13. 3rd degree: Complete A-V dissociation; random P wave and QRS