STEP 1 — MCQs (NO answers here)

MCQ 1 — Direction of Thrombus Propagation

Relative to blood flow, thrombi tend to:

a. Never propagate

b. Propagate toward the heart

c. Propagate away from the heart in all vessels

d. Always stay strictly at their point of origin

e. Only form in veins

MCQ 2 — Arterial vs Venous Growth Direction

From the point of attachment, arterial and venous thrombi extend:

a. Arterial: with flow; Venous: retrograde

b. Arterial: retrograde; Venous: in direction of flow

c. Both in direction of flow

d. Both retrograde

e. Neither extend significantly

MCQ 3 — Embolus-Prone Segment

The part of a thrombus most likely to embolize is:

a. The firmly attached base

b. The propagating, poorly attached portion

c. Only the central core

d. Only lines of Zahn

e. The valve attachment point only

MCQ 4 — Lines of Zahn

Lines of Zahn are:

a. Areas of calcification

b. Laminations of pale platelet/fibrin layers alternating with darker red cell–rich layers

c. Pure red cell clumps without fibrin

d. Seen only in postmortem clots

e. Seen only in capillaries

MCQ 5 — Significance of Lines of Zahn

Presence of classic lines of Zahn generally indicates:

a. Postmortem clotting in stagnant blood

b. Antemortem thrombus formed in flowing blood

c. A purely venous origin

d. A purely arterial origin

e. Only infective vegetations

MCQ 6 — Postmortem Clots vs Antemortem Venous Thrombi

Postmortem clots characteristically:

a. Are firm, gray-white, and attached to wall

b. Are gelatinous, have a dark red dependent portion and a yellow “chicken fat” upper portion, and are not attached to wall

c. Show clear lines of Zahn

d. Are always mural

e. Are indistinguishable from red thrombi

MCQ 7 — Mural Thrombi

Thrombi occurring in heart chambers or in the aortic lumen are best described as:

a. Vegetations

b. Mural thrombi

c. Red thrombi

d. Stasis clots

e. Postmortem clots

MCQ 8 — Causes of Cardiac Mural Thrombi

Cardiac mural thrombi are promoted by:

a. Only hypertension

b. Abnormal myocardial contraction or endomyocardial injury

c. Increased plasma volume only

d. Excess fibrinolysis

e. Always congenital defects

MCQ 9 — Aortic Thrombosis Predisposition

Aortic thrombosis is especially promoted by:

a. Normal laminar flow

b. Ulcerated atherosclerotic plaques and aneurysmal dilation

c. High platelet count alone

d. Isolated anemia

e. High HDL levels

MCQ 10 — Arterial Thrombi Characteristics

Arterial thrombi are typically:

a. Non-occlusive and RBC-rich

b. Occlusive and platelet-rich

c. Purely fibrin without cells

d. Only found in veins of the legs

e. Only due to hypercoagulability

MCQ 11 — Venous Thrombi Characteristics

Venous thrombi (phlebothrombosis) are:

a. Rarely occlusive and usually small

b. Almost invariably occlusive and often form long casts towards the heart

c. Confined only to portal vein

d. Always sterile vegetations

e. Composed only of platelets

MCQ 12 — “Red” or Stasis Thrombi

Venous thrombi are called “red” or “stasis” thrombi because:

a. They are composed only of fibrin

b. They form in high-velocity arterial flow

c. They contain abundant enmeshed red cells due to sluggish venous circulation

d. They form only after death

e. They have calcified heads

MCQ 13 — Common Venous Sites

The veins most commonly involved in venous thrombosis are:

a. Veins of upper extremities

b. Portal and hepatic veins

c. Veins of lower extremities

d. Dural sinuses

e. Ovarian veins only

MCQ 14 — Other Venous Sites

Under special circumstances, venous thrombi may be found in all EXCEPT:

a. Dural sinuses

b. Portal vein

c. Hepatic vein

d. Pulmonary veins

e. Periprostatic, ovarian, and periuterine plexuses

MCQ 15 — Attachment and Consistency: Red Thrombi vs Postmortem Clot

Typical red thrombi are:

a. Gelatinous, unattached, with chicken-fat layering

b. Firm, focally attached to vessel walls, with gray fibrin strands

c. Entirely yellow and fatty

d. Always intramyocardial

e. Only found on valves

MCQ 16 — Vegetations

Thrombi on heart valves are called:

a. Aneurysms

b. Vegetations

c. Red thrombi

d. Lines of Zahn

e. Phlebothromboses

MCQ 17 — Infective Endocarditis

Large friable thrombotic masses on valves in the presence of bacteremia or fungemia are characteristic of:

a. Nonbacterial thrombotic endocarditis

b. Libman-Sacks endocarditis

c. Infective endocarditis

d. Postmortem clot

e. Fat embolism

MCQ 18 — Nonbacterial Thrombotic Endocarditis (NBTE)

Sterile vegetations developing on noninfected valve edges in hypercoagulable states are termed:

a. Infective endocarditis

b. Nonbacterial thrombotic endocarditis

c. Libman-Sacks endocarditis

d. Rheumatic endocarditis

e. Verrucous endocarditis from SLE

MCQ 19 — Libman-Sacks Endocarditis

Sterile, verrucous vegetations on valves in association with systemic lupus erythematosus are called:

a. Infective endocarditis

b. Nonbacterial thrombotic endocarditis

c. Libman-Sacks endocarditis

d. Marantic endocarditis from cancer

e. Rheumatic vegetations

STEP 2 — ANSWERS + SHORT EXPLANATIONS

MCQ 1 — b

Thrombi propagate toward the heart along the vessel or chamber.

MCQ 2 — b

• Arterial thrombi: grow retrograde (against flow) from attachment.
• Venous thrombi: extend with direction of blood flow (toward heart).

MCQ 3 — b

The propagating, poorly attached tail is most likely to fragment and embolize.

MCQ 4 — b

Lines of Zahn = alternating pale platelet/fibrin layers and darker RBC-rich layers.

MCQ 5 — b

Lines of Zahn indicate an antemortem thrombus in flowing blood, not a postmortem clot.

MCQ 6 — b

Postmortem clots: gelatinous, dark red dependent part + yellow “chicken fat” top, and not attached to the wall.

MCQ 7 — b

Thrombi in heart chambers or aorta = mural thrombi.

MCQ 8 — b

Cardiac mural thrombi: associated with abnormal myocardial contraction (arrhythmia, dilated cardiomyopathy, MI) or endomyocardial injury (myocarditis, catheter).

MCQ 9 — b

Aortic thrombosis: promoted by ulcerated atherosclerotic plaques and aneurysmal dilation.

MCQ 10 — b

Arterial thrombi: frequently occlusive, typically platelet-rich, often over ruptured atherosclerotic plaque or other vascular injury.

MCQ 11 — b

Venous thrombi: almost always occlusive, may form long casts extending toward the heart.

MCQ 12 — c

Venous thrombi form in sluggish venous circulation, with many enmeshed red cells → “red” or “stasis” thrombi.

MCQ 13 — c

About 90% of venous thromboses occur in veins of the lower extremities.

MCQ 14 — d

Special sites: periprostatic, ovarian, periuterine veins; dural sinuses; portal and hepatic veins. Pulmonary veins are not listed in this context in your text.

MCQ 15 — b

Red thrombi: firm, focally attached to vessel wall, with gray fibrin strands, in contrast to loose postmortem clots.

MCQ 16 — b

Valve thrombi are called vegetations.

MCQ 17 — c

Large, often infected vegetations on damaged valves due to bacteremia/fungemia = infective endocarditis.

MCQ 18 — b

Sterile vegetations on noninfected valves in hypercoagulable states = nonbacterial thrombotic endocarditis.

MCQ 19 — c

Sterile, verrucous endocarditis in SLE = Libman-Sacks endocarditis.

STEP 3 — HIGH-YIELD NOTES (EXAM-READY)

1. General Features of Thrombi

• Location: can form anywhere in the cardiovascular system.
• Site dependence:
• Arterial/cardiac thrombi → usually at sites of endothelial injury or turbulence.
• Venous thrombi → characteristically at sites of stasis.
• Attachment and propagation:
• Thrombi are focally attached to underlying vessel or endocardium.
• They propagate toward the heart:
• Arterial: grow retrograde from point of attachment (against flow).
• Venous: grow with blood flow toward the heart.
• Embolic risk:
• The propagating tail is poorly attached → prone to fragmentation → embolus.

2. Lines of Zahn and Antemortem vs Postmortem Clots

Lines of Zahn

• Gross and microscopic laminations:
• Pale bands → platelets + fibrin.
• Dark bands → RBC-rich layers.
• Found only in thrombi formed in flowing blood.
• Help differentiate antemortem thrombus from postmortem clot.

Postmortem Clots

• Gelatinous, soft; due to blood settling.
• Appearance:
• Dark red dependent lower portion (settled RBCs).
• Yellow “chicken fat” upper portion (serum).
• Typically not attached to vessel wall.
• Contrast with red thrombi, which are:
• Firm.
• Focally wall-attached.
• Contain gray fibrin strands.(antemortem clots)

3. Mural Thrombi

• Definition: thrombi in heart chambers or aortic lumen.
• Cardiac mural thrombi:
• Causes:
• Abnormal myocardial contraction:
• Arrhythmias.
• Dilated cardiomyopathy.
• Myocardial infarction.
• Endomyocardial injury:
• Myocarditis.
• Catheter-induced trauma.
• Aortic mural thrombi:
• Favored by:
• Ulcerated atherosclerotic plaques.
• Aneurysmal dilation.

4. Arterial vs Venous Thrombi

Arterial Thrombi

• Frequently occlusive.
• Classically platelet-rich (white thrombi).
• Mechanism:
• Endothelial injury, especially ruptured atherosclerotic plaques.
• Also vasculitis and traumatic vascular injury.
• Often superimposed on an underlying plaque.

Venous Thrombi (Phlebothrombosis)

• Almost invariably occlusive.
• Often form a long cast of the lumen extending toward the heart.
• Composition:
• Abundant RBCs within fibrin mesh → “red” or “stasis” thrombi.
• Most common sites:
• Lower extremity veins (~90%).
• Other possible sites:
• Upper extremity veins.
• Periprostatic plexus.
• Ovarian and periuterine veins.
• Under special conditions:
• Dural sinuses.
• Portal vein.
• Hepatic vein.

5. Vegetations (Valve Thrombi)

• Definition: thrombotic masses on heart valves.

A. Infective Endocarditis

• Bloodborne bacterial or fungal infections.
• Cause valve damage and large, friable vegetations.
• Vegetations are often loaded with organisms → high embolic and destructive potential.

B. Nonbacterial Thrombotic Endocarditis (NBTE)

• Sterile vegetations.
• Occur on noninfected valves.
• Associated with hypercoagulable states (e.g., advanced cancer).
• Vegetations are usually small, bland thrombi along valve closure lines.

C. Libman-Sacks Endocarditis

• Sterile, verrucous vegetations.
• Occur on valves in systemic lupus erythematosus (SLE).
• Can involve both sides of the valve and sometimes chordae.