Heart

 

2. Findings and Diagnosis

 

 

Left Ventricular (LV) Pseudoaneurysm (PSA): Definition and Imaging Contributions

🔎 Definition

A left ventricular (LV) pseudoaneurysm (PSA) is a contained myocardial rupture, where blood escapes through a full-thickness defect in the ventricular wall but is contained by the pericardium or surrounding adhesions rather than true myocardium. Unlike a true aneurysm, which has a wide neck and contains thinned myocardial tissue, a pseudoaneurysm has a narrow neck, lacks myocardial integrity, and has a high risk of rupture (30-45%).

---

📡 Role of Imaging in LV PSA Diagnosis

🩺 Echocardiography (TTE & TEE)

🔹 Transthoracic Echocardiography (TTE)

• First-line test but limited for posterior basal PSAs due to rib interference.
• Can detect abnormal outpouching with a narrow neck and identify thrombus.

🔹 Transesophageal Echocardiography (TEE) (Gold Standard for Posterior PSA)

• Best for posterior/basal pseudoaneurysms.
• Provides high-resolution imaging of the pseudoaneurysm neck and flow characteristics.

🔹 Contrast Echocardiography

• Enhances visualization of neck size and flow communication with the LV.
• Helps distinguish thrombus vs. perfused pseudoaneurysm cavity.

🔹 Doppler Findings:
✔ To-and-fro flow across the narrow neck (hallmark of PSA).
✔ Bidirectional swirling flow in the cavity (may resemble the Yin-Yang sign, seen in arterial pseudoaneurysms).
✔ Abnormal systolic expansion of the sac, unlike normal LV contraction.

---

🖥️ CT and MRI: Advanced Imaging for PSA

🔸 CT Angiography (CTA)

• Best for detailed anatomical assessment of the pseudoaneurysm, its neck size, and relationship with surrounding structures.
• Thin-wall outpouching with a narrow neck and possible thrombus.
• Better than echocardiography for evaluating posterior or lateral wall pseudoaneurysms.

🔸 Cardiac MRI

• Gold standard for tissue characterization (differentiate thrombus from perfused lumen).
• Cine MRI shows dyskinesis and paradoxical expansion of the pseudoaneurysm.
• Late gadolinium enhancement (LGE) helps differentiate between true and false aneurysms.

---

🛠 Key Imaging Differences: LV PSA vs. True Aneurysm

Feature	LV Pseudoaneurysm	True LV Aneurysm
Neck Width	Narrow (<50% of sac diameter)	Wide (>50% of sac diameter)
Wall Composition	No myocardium (fibrous pericardium or scar)	Thinned but intact myocardium
Flow Pattern (Doppler)	To-and-fro across neck, bidirectional flow in sac	No significant flow through the aneurysm
CT/MRI Appearance	Thin-walled outpouching, narrow neck, possible thrombus	Broad-based bulge, wide neck, preserved myocardium
Rupture Risk	High (~30-45%) → Requires surgery	Low → Managed conservatively unless symptomatic

---

🔬 Clinical Importance

🚨 LV PSA requires urgent surgical intervention due to high rupture risk.
🚨 Echocardiography (TTE/TEE), CT, and MRI play complementary roles in early detection and differentiation from true aneurysms.

1. A 72-year-old male with a history of an inferior myocardial infarction presents with dyspnea and exertional fatigue. A transthoracic echocardiogram (TTE) reveals a thin-walled, dyskinetic outpouching of the posterior basal left ventricular wall with a narrow neck and bidirectional blood flow at the communication site. What is the most likely diagnosis?

A) Left ventricular thrombus
B) Left ventricular pseudoaneurysm
C) Left ventricular true aneurysm
D) Pericardial cyst
E) Aortic dissection

✅ Correct Answer: B) Left ventricular pseudoaneurysm

Explanation:

• The narrow neck and to-and-fro flow on Doppler suggest a pseudoaneurysm (PSA) rather than a true aneurysm.
• Pseudoaneurysms are contained ruptures, commonly occurring in the posterior basal wall after an inferior MI, as seen here.

❌ Incorrect Answers:

• A) LV thrombus → Incorrect. Thrombi appear as echogenic filling defects inside the LV but do not have flow communication.
• C) True aneurysm → Incorrect. Aneurysms have a wide neck and lack turbulent Doppler flow.
• D) Pericardial cyst → Incorrect. Cysts are fluid-filled structures and do not have flow communication with the LV.
• E) Aortic dissection → Incorrect. Dissection involves intimal tearing of the aorta, not the LV.

---

2. Which of the following best differentiates a left ventricular pseudoaneurysm from a true aneurysm on CT or MRI?

A) Pseudoaneurysms have a wide neck, while true aneurysms have a narrow neck
B) Pseudoaneurysms contain intact myocardium, while true aneurysms lack myocardium
C) Pseudoaneurysms are at low risk for rupture, while true aneurysms have a high rupture risk
D) Pseudoaneurysms have a narrow neck and lack myocardial wall integrity, while true aneurysms have a wide neck and contain myocardium
E) Both conditions always require immediate surgical repair

✅ Correct Answer: D) Pseudoaneurysms have a narrow neck and lack myocardial wall integrity, while true aneurysms have a wide neck and contain myocardium

Explanation:

• CT and MRI show that pseudoaneurysms have a narrow neck and are composed of pericardial tissue rather than intact myocardium, making them prone to rupture.
• True aneurysms have a wide neck, thinned but intact myocardial wall, and low rupture risk.

❌ Incorrect Answers:

• A) Wide neck in PSA, narrow neck in true aneurysm → Incorrect. The opposite is true; pseudoaneurysms have a narrow neck, true aneurysms have a wide neck.
• B) PSA contains myocardium → Incorrect. Pseudoaneurysms lack myocardial wall integrity.
• C) PSA is low risk for rupture → Incorrect. Pseudoaneurysms are high risk (30-45%), while true aneurysms rarely rupture.
• E) Both need surgery → Incorrect. PSA requires surgery due to rupture risk, while true aneurysms are managed conservatively unless symptomatic.

---

3. A 65-year-old woman undergoes a cardiac MRI for evaluation of a suspected left ventricular aneurysm. Which of the following MRI findings would most strongly support a diagnosis of left ventricular pseudoaneurysm rather than a true aneurysm?

A) Myocardial thinning with late gadolinium enhancement (LGE)
B) Dyskinetic wall motion with paradoxical systolic expansion
C) A narrow-necked communication between the LV cavity and an adjacent outpouching
D) Hypokinetic motion of a broad-based aneurysmal sac
E) Presence of an intraluminal thrombus within the aneurysmal cavity

✅ Correct Answer: C) A narrow-necked communication between the LV cavity and an adjacent outpouching

Explanation:

• The hallmark feature of LV pseudoaneurysm on MRI is a narrow-necked outpouching with no myocardial wall at its base.
• True aneurysms have a wide-necked communication and contain thinned myocardium.

❌ Incorrect Answers:

• A) Myocardial thinning with LGE → Seen in both pseudoaneurysms and true aneurysms.
• B) Dyskinetic wall motion with paradoxical systolic expansion → Both PSA and true aneurysms can show abnormal motion, but PSA is differentiated by neck size.
• D) Hypokinetic broad-based aneurysm → This describes a true aneurysm, not a PSA.
• E) Intraluminal thrombus → Both PSA and true aneurysms may develop thrombus due to stasis.

---

Key Takeaways:

✔ Pseudoaneurysm = Narrow neck, lacks myocardial wall, high rupture risk (30-45%) → Requires surgery.
✔ True aneurysm = Wide neck, contains myocardium, low rupture risk → Often managed conservatively.
✔ Echocardiography (TTE/TEE), CT, and MRI play complementary roles in PSA diagnosis.