Echocardiographic Algorithm for Post-Myocardial Infarction LV Thrombus: A Gatekeeper for Thrombus Evaluation by Delayed Enhancement CMR

Abstract

Objectives: The goal of this study was to determine the prevalence of post-myocardial infarction (MI) left ventricular (LV) thrombus in the current era and to develop an effective algorithm (predicated on echocardiography [echo]) to discern patients warranting further testing for thrombus via delayed enhancement (DE) cardiac magnetic resonance (CMR).

Background: LV thrombus affects post-MI management. DE-CMR provides thrombus tissue characterization and is a well-validated but an impractical screening modality for all patients after an MI.

Methods: A same-day echo and CMR were performed according to a tailored protocol, which entailed uniform echo contrast (irrespective of image quality) and dedicated DE-CMR for thrombus tissue characterization.

Results: A total of 201 patients were studied; 8% had thrombus according to DE-CMR. All thrombi were apically located; 94% of thrombi occurred in the context of a left anterior descending (LAD) infarct-related artery. Although patients with thrombus had more prolonged chest pain and larger MI (p ≤ 0.01), only 18% had aneurysm on echo (cine-CMR 24%). Noncontrast (35%) and contrast (64%) echo yielded limited sensitivity for thrombus on DE-CMR. Thrombus was associated with stepwise increments in basal → apical contractile dysfunction on echo and quantitative cine-CMR; the echo-measured apical wall motion score was higher among patients with thrombus (p < 0.001) and paralleled cine-CMR decrements in apical ejection fraction and peak ejection rates (both p < 0.005). Thrombus-associated decrements in apical contractile dysfunction were significant even among patients with LAD infarction (p < 0.05). The echo-based apical wall motion score improved overall performance (area under the curve 0.89 ± 0.44) for thrombus compared with ejection fraction (area under the curve 0.80 ± 0.61; p = 0.01). Apical wall motion partitions would have enabled all patients with LV thrombus to be appropriately referred for DE-CMR testing (100% sensitivity and negative predictive value), while avoiding further testing in more than one-half (56% to 63%) of patients.

Conclusions: LV thrombus remains common, especially after LAD MI, and can occur even in the absence of aneurysm. Although DE-CMR yielded improved overall thrombus detection, apical wall motion on a noncontrast echocardiogram can be an effective stratification tool to identify patients in whom DE-CMR thrombus assessment is most warranted. (Diagnostic Utility of Contrast Echocardiography for Detection of LV Thrombi Post ST Elevation Myocardial Infarction; NCT00539045).

Keywords: cardiovascular magnetic resonance; echocardiography; left ventricular thrombus.

Figure 1. LV Thrombus Detection by Non-Contrast and Contrast Echo

Representative examples of (1A) LV thrombus concordantly detected by non-contrast (left) and contrast (right) echo, and (1B) improved detection of LV thrombus via contrast echo. Images displayed in 4-chamber orientation (thrombus denoted by yellow circle). In both examples, DE-CMR confirmed contrast echo results, as evidenced by thrombus-associated avascularity within the LV apex (images shown in 4-chamber [corresponding to echo], and short axis orientation [inset]). As shown on far right (green arrows), both cases also demonstrated resolution of DE-CMR-evidenced thrombus following treatment with warfarin-based anticoagulation.

Figure 2. LV Thrombus Detection via DE-CMR Despite Negative Echocardiography

Representative example of DE-CMR evidenced thrombus despite negative non-contrast (left) and contrast (right) echo. Note image artifact on non-contrast echo (arrow), which compromised endocardial definition and obscured LV cavity delineation. Contrast echo yielded improved image quality, but failed to detect mural thrombus in the LV apex (yellow circle; 4-chamber and short axis orientation shown).

Figure 3. Receiver Operating Characteristics Curves

Apical LV wall motion score via non-contrast echo (red) yielded improved diagnostic performance compared to EF (blue), as evidenced by higher area under the curve (p=0.01).