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

Picture it — where aortic disease sits

Abdominal aneurysmBelow the renal arteries, fusiform — atherosclerosis.

Thoracic aneurysmAscending aorta — cystic medial degeneration (Marfan), syphilis, bicuspid valve.

Dissection — Stanford AInvolves the ascending aorta → surgery.

Dissection — Stanford BBeyond the left subclavian → usually medical.

True aneurysmAll three wall layers bulge.

PseudoaneurysmWall breached; blood held in by surrounding tissue.

Schematic diagrams, not to scale. Red = abnormal.

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