LV thrombus detection by routine echocardiography: insights into performance characteristics using delayed enhancement CMR

Abstract

Objectives: This study sought to evaluate performance characteristics of routine echo for left ventricular thrombus (LVT).

Background: Although the utility of dedicated echocardiography (echo) for LVT is established, echo is widely used as a general test for which LVT is rarely the primary indication. We used delayed-enhancement cardiac magnetic resonance (DE-CMR) as a reference to evaluate LVT detection by routine echo.

Methods: Dedicated LVT assessment using DE-CMR was prospectively performed in patients with left ventricular systolic dysfunction. Echoes were done as part of routine clinical care. Echo and CMR were independently read for LVT and related indexes of LVT size, shape, and image quality/diagnostic confidence. Follow-up was done for embolic events and pathology validation of LVT.

Results: In this study, 243 patients had routine clinical echo and dedicated CMR within 1 week without intervening events. Follow-up supported DE-CMR as a reference standard, with >5-fold difference in endpoints between patients with versus without LVT by DE-CMR (p = 0.02). LVT prevalence was 10% by DE-CMR. Echo contrast was used in 4% of patients. Echo sensitivity and specificity were 33% and 91%, with positive and negative predictive values of 29% and 93%. Among patients with possible LVT as the clinical indication for echo, sensitivity and positive predictive value were markedly higher (60%, 75%). Regarding sensitivity, echo performance related to LVT morphology and mirrored cine-CMR, with protuberant thrombus typically missed when small (p ≤ 0.02). There was also a strong trend to miss mural thrombus irrespective of size (p = 0.06). Concerning positive predictive value, echo performance related to image quality, with lower diagnostic confidence scores for echoes read positive for LVT in discordance with DE-CMR compared with echoes concordant with DE-CMR (p < 0.02).

Conclusions: Routine echo with rare contrast use can yield misleading results concerning LVT. Echo performance is improved when large protuberant thrombus is present and when the clinical indication is specifically for LVT assessment.

Figure 1. Follow-up Endpoints in Relation to Imaging Findings

Stratification of patients with follow-up according to presence or absence of thrombus by DE-CMR yielded over a 5-fold difference in study endpoints (TIA, CVA, or pathology-verified thrombus) between groups whereas stratification according to echo thrombus yielded a 1.8 fold difference (red = thrombus +, blue = thrombus−).

Figure 2. Typical Example of LV Thrombus Assessment by Routine Echo and Dedicated DE-CMR

Routine echo (2A) demonstrates absence of thrombus but prominent near field artifact within the LV apex resulting in suboptimal image quality. DE-CMR (2B) demonstrates a large mural thrombus adherent to the LV anterior wall (asterisk) as well as absence of apical thrombus. Note that thrombus on DE-CMR appears black on long TI (left) and etched on standard TI (right) imaging. DE-CMR findings were confirmed by direct surgical inspection of the LV and histopathology examination (2C) (H&E stain, high power) of surgically resected material, which demonstrated a thrombus with organizing features (prominent collagen and fibrin content) adjacent to the LV anterior wall.

Figure 3. Imaging Results Concerning LV Thrombus

Echo results concerning the diagnosis of thrombus stratified by cine- and DE-CMR findings (red = thrombus +, blue = thrombus −). Both echo sensitivity (3A) and positive predictive value (3B) were higher among cases in which thrombus was also evidenced by cine-CMR vs. those in which cine-CMR was negative. While cine-CMR appropriately detected thrombus in an additional 7 patients with negative echo, both tests were negative in 9/24 patients with thrombus by DE-CMR tissue characterization.