LV Aneurysm and Pseudoaneurysm

True LV aneurysm and pseudoaneurysm are two of the most consequential words in an echocardiography report to get right or wrong — both can present as an outpouching of the LV contour after acute myocardial infarction, yet one is a stable, usually medically managed finding and the other is a surgical emergency. This page covers the differential between them specifically; the remaining mechanical complications of MI — ventricular septal rupture, papillary muscle rupture, and free wall rupture itself — have their own dedicated page.

Two Genuinely Different Processes, Not Two Names for One Thing

A true LV aneurysm is thinned, fibrotic myocardium — structurally continuous with the rest of the ventricular wall, formed by infarct expansion and remodeling. A pseudoaneurysm is a contained free wall rupture: its wall is composed of organized thrombus and pericardium, not myocardium at all, held together only because the rupture has been sealed by adjacent structures rather than genuinely healed. This isn’t a subtle distinction — it’s the entire reason the two findings are managed so differently, and it’s worth holding in mind as the organizing fact behind every feature described below.

Epidemiology and Timing

• True LV aneurysm occurs in roughly 8–15% of infarcts overall, rising to 10–22% specifically with a first anterior MI. It forms from myocardial thinning and dilation beginning as early as 24 to 72 hours after acute MI, though it may not become clearly apparent on imaging for about 5 days. Without intervention, it carries a notably elevated mortality — roughly 60% at three years in historical series.
• Pseudoaneurysm is comparatively rare, accounting for about 3% of all AMI cases, though it also occurs after cardiac surgery, blunt chest trauma, or endocarditis — not exclusively as a post-infarction finding. It is a common cause of death within the first two weeks after acute MI (5–10%), reflecting its genuine, ongoing risk of free rupture at any point after formation.

Location and Culprit Vessel: A Clean, Useful Contrast

The two entities cluster in genuinely different locations, tied to different culprit vessels — worth checking directly against the territory already identified using the framework on Coronary Territories and Infarct Localization:

	True aneurysm	Pseudoaneurysm
Typical location	LV apex	Basal inferior-posterior wall
Typical culprit vessel	LAD occlusion	Circumflex or RCA occlusion

This distribution isn’t a coincidence — it reflects where each mechanism (gradual expansion versus a genuine wall tear) tends to occur anatomically, and it’s a useful piece of corroborating evidence whenever the neck geometry itself is ambiguous.

The Key Discriminator: Neck Width

The single most reliable echocardiographic feature separating the two is the neck — the width of the communication between the LV cavity and the aneurysmal sac, relative to the sac’s own maximal diameter.

• True aneurysm: a wide neck, with the aneurysmal segment gradually tapering into the ventricle rather than communicating through a discrete, narrow opening.
• Pseudoaneurysm: a narrow neck — specifically, an entry diameter less than half the maximal diameter of the pseudoaneurysm cavity itself. This ratio is worth measuring explicitly rather than estimating visually, given how much management hinges on getting this right.

Additional Echocardiographic Features

True Aneurysm

• Thin, bright (echogenic), dyskinetic myocardial segment.
• A genuine diastolic contour abnormality — the aneurysm deforms the ventricle in both systole and diastole, distinct from simple dyskinesis, which deforms the wall only during systole. This is a useful bedside clue even before formally measuring the neck: diastolic deformation implies a more established, anatomically fixed process than dyskinesis alone.
• Associated thrombus is common, given the stasis created by the akinetic-to-dyskinetic segment — see Intracardiac Thrombus and Sources of Embolism for the complete diagnostic approach to LV thrombus, which applies directly here.

Pseudoaneurysm

• A discrete akinetic, dilated area communicating with the LV through the narrow neck described above.
• Systolic expansion of the pseudoaneurysm cavity itself — worth watching for directly on a cine loop, since it reflects the sac genuinely filling under LV systolic pressure through the rupture site.
• Frequently contains thrombus lining its wall — and this is worth stating as a genuine diagnostic hazard rather than a passing detail: this thrombus lining can be mistaken for a thick myocardial wall on a cursory read, precisely the kind of error that could lead to reassuring a patient with a surgical emergency that they have a benign, thick-walled structure instead.
• To-and-fro blood flow through the site of rupture, detectable by pulsed or color-flow Doppler — a genuinely distinctive Doppler sign, reflecting flow moving back and forth through the narrow communication rather than the more uniform flow pattern seen across a true aneurysm’s wide neck.

When the Diagnosis Is Genuinely Unclear

Echocardiography is the procedure of choice for initial evaluation whenever a post-MI patient develops a new finding suggesting either entity, but image quality and a difficult acoustic window can genuinely limit confidence in distinguishing the two — and given how differently they’re managed, that uncertainty is worth resolving actively rather than hedging in the report.

• Microbubble contrast administration can clarify ambiguous cases, and should be considered whenever diagnostic uncertainty exists — detection of microbubble contrast within the pericardial space, rather than confined to the ventricular cavity, is itself confirmatory of a ruptured, pseudoaneurysm-forming process.
• TEE can add value when transthoracic windows are genuinely inadequate, though neither modality substitutes for careful neck-ratio measurement once adequate images are obtained.
• Any pericardial effusion in a patient with sudden hemodynamic compromise after acute MI should itself raise this differential — see Pericardial Effusion and Cardiac Tamponade for the general assessment framework. An enlarging effusion containing echodense material (thrombus) in this specific clinical context is a highly specific finding for contained or ongoing rupture, and should prompt urgent surgical evaluation rather than routine effusion management.

Why the Distinction Changes Management

Pseudoaneurysm demands a fundamentally different response than true aneurysm, which is the entire clinical reason this differential matters as much as it does:

• Pseudoaneurysm carries a significant, ongoing risk of free rupture and is a common cause of death in the first two weeks after MI — surgical referral is the default once the diagnosis is genuinely suspected, not a finding to monitor expectantly.
• True aneurysm is generally managed medically, reserved for surgical consideration only when it causes refractory heart failure, recurrent thromboembolism despite anticoagulation, or recurrent ventricular arrhythmia arising from the aneurysmal segment’s scarred border zone.

Getting the neck ratio, the location, and the wall composition right isn’t an academic exercise in this specific differential — it’s the difference between appropriately reassuring a patient and sending one who needs emergency surgery home with a benign label instead.

How to Approach a Suspected LV Aneurysm or Pseudoaneurysm: A Practical Sequence

1. Measure the neck ratio explicitly — entry diameter relative to maximal sac diameter — rather than relying on visual impression, given how much hinges on this single measurement.
2. Check the location and presumed culprit vessel against the apex-LAD (true aneurysm) versus inferoposterior-circumflex/RCA (pseudoaneurysm) pattern, using it as corroborating rather than standalone evidence.
3. Assess diastolic contour specifically — genuine diastolic deformation supports true aneurysm over simple dyskinesis.
4. Look for to-and-fro Doppler flow across the neck, a specific sign favoring pseudoaneurysm.
5. Actively consider that a thrombus-lined wall can mimic a thick myocardial wall — don’t let apparent wall thickness alone argue against pseudoaneurysm without checking the neck ratio and flow pattern directly.
6. Use contrast or TEE when uncertainty remains after a careful transthoracic assessment, given the genuinely high stakes of misclassifying either entity.
7. Correlate with the clinical context — new hemodynamic compromise, an enlarging pericardial effusion with echodense material, or presentation within the first two weeks post-MI should all raise suspicion for pseudoaneurysm specifically and prompt urgent surgical discussion.

Clinical Importance

This differential is one of the clearest examples in all of echocardiography where a single measurement — the neck ratio — carries genuinely life-or-death management implications. The underlying mechanism (true myocardial thinning versus a contained rupture) explains every downstream feature: why the locations and culprit vessels differ, why one deforms in diastole and the other doesn’t, and why mistaking a thrombus-lined pseudoaneurysm wall for simple hypertrophy is a genuinely dangerous error rather than a minor misread.