Decoding Postinfarction Left Ventricular Pseudoaneurysm

Abstract

Recognizing true from pseudo left ventricular aneurysm after myocardial infarction is paramount to guide clinical management and determine need for surgical urgency. We discuss a case of a postinfarction pseudoaneurysm that poses unique anatomic challenges and may hold a secret “DaVinci code” beyond current diagnostic criteria. (Level of Difficulty: Advanced.)

Central Illustration

History of Presentation

A 60-year-old man with multiple cardiovascular risks initially presented with an acute inferolateral ST-segment elevation myocardial infarction (MI). He underwent emergent coronary angiography and successful primary percutaneous coronary intervention with 2 drug-eluting stents to a large first obtuse marginal branch of the left circumflex artery (culprit vessel; right dominant system) (Figure 1). Given high thrombus burden integrilin (eptifibatide) infusion was initiated while awaiting full effect of the P2Y₁₂ inhibitor. However, it was discontinued 50 minutes later because of moderate pericardial effusion and cardiac tamponade noticed on bedside transthoracic echocardiography (TTE); mildly decreased left ventricular (LV) systolic function with inferolateral hypokinesis. Emergent pericardiocentesis confirmed hemopericardium. No evidence of coronary artery rupture was found on repeat coronary angiography. The patient recovered well and was discharged on day 3 on optimal goal-directed heart failure medical therapy.

Learning Objectives

• •To gain insight into anatomy of the LV pseudoaneurysm following an acute transmural MI using multimodality imaging modalities.
• •To highlight the importance of history of presentation into clinical decision making in patients presenting with LV aneurysm formation after coronary reperfusion therapy.

Figure 1.

Emergent Coronary Angiography

(A) Occluded first obtuse marginal branch (arrows) with an intracoronary wire in situ before percutaneous coronary intervention and (B) after reperfusion therapy. (C) Dominant right coronary artery (RCA). LAD = left anterior descending; LCX = left circumflex; RPDA = right posterior descending artery.

The patient was readmitted 20 days later with worsening dyspnea. Contrast-enhanced TTE revealed severe LV systolic dysfunction with an interim formation of a large LV aneurysm with a broad neck within the inferolateral segments (Figure 2A), and no recurrent pericardial effusion. High-resolution cardiac computed tomography (HRCT) angiography helped further characterize the anatomy and remodeling of the LV chamber. A large aneurysmal sac (6.8 × 3.4 cm) involving mid-to-apical lateral LV segments (Figure 2B) with a wide neck measuring 6.1 × 5.9 cm was found with no obvious thrombus (Figure 2C, Video 1). The calculated maximal internal width of the aneurysmal orifice to the maximal parallel internal diameter ratio of 0.95 was greater than that classically expected in pseudoaneurysm and pointed more toward a true aneurysm. HRCT was able to identify thin walls of the LV aneurysm based on low 10.3 HU measurements, compared with the HU ranging from 131.3 to 142.7 within the nonaneurysmal LV segments (Figure 2D); altogether, these findings raised concern for postinfarction pseudoaneurysm formation and contained rupture. Three-dimensional and volume-rendered HRCT reconstruction clearly demonstrated that a large LV aneurysmal sac developed within the distribution of recently occluded and reperfused large obtuse marginal branch (Figure 3, Videos 2, 3, and 4).

Figure 2.

Contrast-Enhanced 2-Dimensional Transthoracic Echocardiography and Anatomic Correlation With High-Resolution Cardiac Computed Tomography

Note a large-sized aneurysm of the left ventricular (LV) lateral wall with a wide neck typically seen in a “true” aneurysm. Thin walls of the LV aneurysmal sac with relatively low Hounsfield Unit (HU) measurements raised concern for contained rupture and “false” or pseudoaneurysm. ∗Body of the LV lateral wall aneurysm.

Figure 3.

Postinfarction Left Ventricular Pseudoaneurysm

High-resolution cardiac computed tomography volume rendering reconstruction (A) and internal view (B) of postinfarction left ventricular pseudoaneurysm. ∗Body of the left ventricular lateral wall aneurysm. OM = obtuse marginal.

Clinical Decision

Both LV “true” and “false” or “pseudo” aneurysms can present with similar symptoms, hemodynamics, physical examination, and nonspecific changes on electrocardiogram.1, 2, 3 Given diagnostic uncertainty based on imaging and high-risk features (recent hemopericardium), a multidisciplinary team approach was taken, including cardiologists, radiologists, and cardiothoracic surgeons, to help facilitate genuinely shared decision making between the care team and the patient regarding high-risk surgery versus conservative approach. Ultimately, the patient accepted perioperative risks and underwent open heart surgery.

Intraoperative gross findings confirmed a large pseudoaneurysm in the lateral LV wall with contained rupture. A bovine pericardial patch was placed on top of the closure line for LV remodeling and hemostasis (Figures 4A to 4C). Histopathological examination revealed a mixture of fibrous/granulation tissue and organizing thrombus without any myocytes (Figures 5A and 5B), ultimately confirming a diagnosis of the LV pseudoaneurysm.

Figure 4.

Surgical Aneurysmectomy After Cardiopulmonary Bypass and Cardiac Arrest

(A) Aneurysm of the lateral wall extending to the apex, left ventricular vent is shown in the aneurysm cavity. Note clear demarcation of whitish damaged myocardium. (B) Linear closure of aneurysm sack with felt, and multiple interrupted stitches placed in viable myocardium around the aneurysm circumferentially. (C) The interrupted stitches used to place a bovine pericardial patch on top of the closure line for left ventricular remodeling and hemostasis.

Figure 5.

Hematoxylin and Eosin Histologic Examination of the Left Ventricular Specimen Confirmed the Diagnosis of Pseudoaneurysm

Aneurysmal specimen revealed fibrous tissue with granulation tissue and organizing thrombus, and no myocardium, consistent with a “false” aneurysm of the heart. (A) Magnification = ×2; (B) ×5.

Discussion

LV aneurysms are rare, but potentially life-threatening sequelae following transmural MI. Early and accurate diagnosis is paramount in directing clinical care because LV pseudoaneurysms prompt surgical emergency, whereas LV true aneurysms rarely rupture.⁴ True postinfarction LV aneurysm is caused by a focal protrusion of all 3 layers of the LV wall (the endocardium, myocardium, and epicardium) ensuring stability. In contrast, LV pseudoaneurysm develops following a focal free wall rupture approximately 10 days to 4 months from coronary occlusion. As a result, hematoma protrudes through the full thickness of the myocardium and becomes contained by adherent pericardium or a scar tissue.1, 2, 3, 4

Differentiation between LV true and false aneurysm remains a clinical and anatomic challenge and accurate diagnosis relies on imaging and pathology. Until the 1990s, left ventriculography used to be the gold standard modality with >85% accuracy.² A characteristic narrow neck and saccular dilatation in the absence of surrounding coronary arteries would support false aneurysm formation.⁵ TTE continues to be the first screening modality using similar criteria; any orifice-to-pseudoaneurysm ratio of <0.5 suggests pseudoaneurysm.⁶ Recent advances in cardiac HRCT angiography³ and cardiac magnetic resonance (CMR) imaging⁷ offer additional 3-dimensional details regarding the LV walls and coronaries. HRCT provides a superior spatial resolution, and scan takes only few minutes; it was the ideal imaging for our patient. However, a definitive diagnosis remains difficult in certain cases. The aneurysmal LV wall can be further delineated by CMR given its tissue characterization ability. Moreover, CMR shows increased sensitivity for pericardial enhancement, which is more commonly observed in LV pseudoaneurysms than true aneurysms,⁷ but it would be technically challenging to perform during orthopnea. Our patient was found to have a large LV outpouching in the territory of the culprit left circumflex coronary artery distribution, 20 days after inferior-lateral ST-segment elevation MI that posed anatomic and diagnostic challenges. Based on infarct location, LV pseudoaneurysm was suspected because of its known stronger predilection for the inferior/posterior and lateral surface.1, 2, 3^,8 There is a paucity of data to support correlation between coronary dominance and postinfarction LV pseudoaneurysm formation. The presence of hemopericardium early post- percutaneous coronary intervention might have, in retrospect, suggested “near miss” myocardial rupture. Interestingly, our patient’s LV aneurysm anatomically mimicked true aneurysm and did not meet current morphological criteria for LV pseudoaneurysm. Initial TTE imaging suggested true LV aneurysm based on a broad neck. Notably, Yeo et al⁸ reported wide neck in postinfarction pseudoaneurysms. Although HRCT displayed orifice-to-pseudoaneurysm ratio ≥0.5,² it also demonstrated thin walls with relatively low HU pointing toward contained rupture. The authors were unable to apply the concept of myocardial “cut-off sign” based on tapering of sac wall thickness seen on HRCT imaging to confidently diagnose a pseudoaneurysm.⁷ Intraoperative examination solidified the diagnoses on false aneurysm that was confirmed by lack of myocardial tissue on histological examination.

This case highlights the anatomic variation and imaging limitations in diagnosing postinfarction LV pseudoaneurysm versus true aneurysm. The authors would like to highlight that current diagnostic criteria may not apply to all cases, therefore additional deductive knowledge and multidisciplinary expertise may be required in some cases to reach a correct diagnosis.

Conclusions

LV pseudoaneurysm formation is a rare and life-threatening complication of acute MI. Postinfarction pseudoaneurysm can present with a “wide neck” and anatomically mimic true LV aneurysm on multimodality imaging. Therefore, orifice-to-pseudoaneurysm ratio should not be solely used as a diagnostic criterion. It our case, HRCT and wall thickness/radiologic density measurements together with clinical context helped overcome diagnostic uncertainty and prompted surgical intervention.

Funding Support and Author Disclosures

The authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Appendix

Video 1

High-resolution cardiac CT helped characterize the anatomy and remodeling of the LV chamber. Note a large aneurysmal sac involving mid and apical lateral LV segments with a wide neck; no obvious thrombus.

Video 2

High-resolution cardiac CT angiography images confirmed a large LV aneurysmal sac developed within the distribution of recently occluded and reperfused large OM branch (marked by yellow arrows)

Video 3

High-resolution cardiac CT angiography volume-rendered reconstruction of postinfarction LV pseudoaneurysm with relation to coronary arteries.

Video 4

High-resolution CT angiography showed an internal 3D rendered view of postinfarction LV pseudoaneurysm.