STEPTRACKERCARDIOVASCULAR | PATHOLOGY | HIGH-YIELD REVIEW

Aneurysms & Aortic Dissection

Weak walls balloon out (aneurysm) or split apart (dissection) — location points to the cause.

FOCUS ON
Abdominal aneurysm = atherosclerosis, older male smoker. Thoracic aneurysm = cystic medial degeneration (Marfan, Ehlers-Danlos, bicuspid valve) or tertiary syphilis. Dissection = hypertension most often, with tearing pain to the back. Type A involves the ascending aorta and needs surgery; type B gets BP and heart-rate control. Berry aneurysms cause subarachnoid hemorrhage.
LESION
CAUSE · MECHANISM
FEATURES
CLUE · TREATMENT
Abdominal aortic aneurysm
Atherosclerosis → plaque compresses vasa vasorum → medial ischemia + MMP damage; usually infrarenal.
Men > 60, smokers, HTN; often silent pulsatile mass. Rupture: severe abdominal/back pain + hypotension + pulsatile mass
Screen men 65–75 who ever smoked (one-time ultrasound) · repair at ≥ 5.5 cm or fast growth
Thoracic aortic aneurysm
Cystic medial degeneration (Marfan/fibrillin-1, Ehlers-Danlos, Loeys-Dietz, bicuspid valve) + HTN; tertiary syphilis (endarteritis of vasa vasorum).
Ascending aorta / root: aortic regurgitation; compression → hoarseness, dysphagia, cough
Syphilis: "tree-bark" intima
Aortic dissection
Intimal tear → blood splits the media → false lumen. Risks: HTN (most common), Marfan, EDS, bicuspid valve, pregnancy, cocaine, trauma.
Sudden tearing chest pain to the back; unequal arm BPs; widened mediastinum
CT angiography or TEE
Dissection complications
False lumen ruptures or blocks branches.
Cardiac tamponade (top cause of death), aortic regurgitation, MI (coronary ostia), stroke, renal/mesenteric/limb ischemia, hemothorax
Muffled heart sounds + JVD + hypotension → tamponade
Berry (saccular) aneurysm
Thin media at circle of Willis bifurcations; most common at anterior communicating artery.
Associations: ADPKD, Ehlers-Danlos, Marfan, coarctation, HTN, smoking
Rupture → subarachnoid hemorrhage; PCoA aneurysm → painful CN III palsy with dilated pupil
Charcot-Bouchard microaneurysm
Chronic HTN damages lenticulostriate vessels.
Basal ganglia, thalamus
Intraparenchymal hemorrhage
Mycotic aneurysm
Infection weakens the wall — septic emboli from endocarditis, Salmonella bacteremia.
Fever + new aneurysm
Can rupture early
Pseudoaneurysm
Contained rupture: blood held by adventitia or surrounding tissue, not all wall layers.
After femoral catheterization, trauma, post-MI free-wall rupture
Pulsatile groin mass after cath

Mechanism — balloon vs split

AtheromaVasa vasorum compressed
→
Media weakens
→
DilationRadius ↑ → wall tension ↑ (Laplace)
→
Rupture
Cystic medial degeneration+ HTN
→
Intimal tear
→
False lumenPropagates
→
Tamponade · branch occlusion · AR

Stanford type A vs type B

FEATURE
TYPE A
TYPE B
Location
Ascending aorta (± descending)
Descending only, beyond left subclavian
Main dangers
Tamponade, AR, coronary occlusion, stroke
Renal, mesenteric, limb ischemia
Treatment
Emergency surgery
β-blocker first to lower HR and BP; surgery if complicated

How it's tested

COMMON CONFUSIONMarfan causes aortic root dilation and dissection. Atherosclerosis causes abdominal aneurysms. Syphilis causes ascending aneurysms in older patients.
THE TRAPChest pain plus a widened mediastinum should not get thrombolytics or heparin "for MI." Rule out dissection first — anticoagulation can be fatal.
YOUR APPROACHWhere is the lesion (abdomen, thorax, brain)? → the matching wall disease → the complication → treatment by type.

If you see… think…

Older male smoker with pulsatile infrarenal mass → AAA
Sudden back pain + hypotension + pulsatile mass → ruptured AAA
Tall young man, upward lens dislocation, aortic root dilation → Marfan (fibrillin-1)
Tree-bark aortic intima + aortic regurgitation in an older man → tertiary syphilis
Tearing chest pain to the back, arm BPs differ → aortic dissection
Dissection + muffled heart sounds + JVD → cardiac tamponade
Dissection of the ascending aorta → type A — surgery
ADPKD patient with thunderclap headache → ruptured berry aneurysm
Headache + ptosis + dilated pupil, eye down-and-out → PCoA aneurysm on CN III
Pulsatile groin mass after cardiac cath → femoral pseudoaneurysm