Contrast-enhanced anatomic imaging as compared to contrast-enhanced tissue characterization for detection of left ventricular thrombus

Abstract

Objectives: This study sought to compare contrast-enhanced anatomic imaging and contrast-enhanced tissue characterization (delayed-enhancement cardiac magnetic resonance [DE-CMR]) for left ventricular (LV) thrombus detection.

Background: Contrast echocardiography (echo) detects LV thrombus based on anatomic appearance, whereas DE-CMR imaging detects thrombus based on tissue characteristics. Although DE-CMR has been validated as an accurate technique for thrombus, its utility compared with contrast echo is unknown.

Methods: Multimodality imaging was performed in 121 patients at high risk for thrombus due to myocardial infarction or heart failure. Imaging included 3 anatomic imaging techniques for thrombus detection (contrast echo, noncontrast echo, cine-CMR) and a reference of DE-CMR tissue characterization. LV structural parameters were quantified to identify markers for thrombus and predictors of additive utility of contrast-enhanced thrombus imaging.

Results: Twenty-four patients had thrombus by DE-CMR. Patients with thrombus had larger infarcts (by DE-CMR), more aneurysms, and lower LV ejection fraction (by CMR and echo) than those without thrombus. Contrast echo nearly doubled sensitivity (61% vs. 33%, p < 0.05) and yielded improved accuracy (92% vs. 82%, p < 0.01) versus noncontrast echo. Patients who derived incremental diagnostic utility from DE-CMR had lower LV ejection fraction versus those in whom noncontrast echo alone accurately assessed thrombus (35 +/- 9% vs. 42 +/- 14%, p < 0.01), with a similar trend for patients who derived incremental benefit from contrast echo (p = 0.08). Contrast echo and cine-CMR closely agreed on the diagnosis of thrombus (kappa = 0.79, p < 0.001). Thrombus prevalence was lower by contrast echo than DE-CMR (p < 0.05). Thrombus detected by DE-CMR but not by contrast echo was more likely to be mural in shape or, when apical, small in volume (p < 0.05).

Conclusions: Echo contrast in high-risk patients markedly improves detection of LV thrombus, but does not detect a substantial number of thrombi identified by DE-CMR tissue characterization. Thrombi detected by DE-CMR but not by contrast echo are typically mural in shape or small in volume.

Figure 1. Apical Thrombus by Anatomic and Tissue Characterization Imaging

(1A) Representative example of apical thrombus (circle) concordantly detected by anatomic imaging (left, contrast echo 4-chamber, cine-CMR 2-chamber) and DE-CMR (center). (1B) Representative example of discordance between anatomic imaging and DE-CMR. DE-CMR identified a small mural thrombus (circle) within the apex. Cine-CMR and contrast echo were interpreted as negative. For both examples, surgical resection enabled thrombus verification based on histopathology (right, H&E stain, low power), which demonstrated thrombus with associated fibroblasts (asterisk).

Figure 2. Non-Apical Thrombus Despite Negative Anatomic Imaging

Representative example of non-apical thrombus detection by DE-CMR despite negative anatomic imaging. Non-contrast and contrast echo (left, 2-chamber view) were negative for thrombus. Cine-CMR (middle) identified thrombus, attributable to acquisition of both short and long axis images. DE-CMR (right, 2-chamber view) identified a large mural thrombus (circle) adjacent to the basal inferior wall.

Figure 3. Thrombus Size in Relation to Echo Detection

Apical thrombi detected by contrast echo were larger than those missed, with a similar trend for non-contrast echo (data shown as mean±SD).