Left Ventricular Thrombi: Insights from Cardiac Magnetic Resonance Imaging

Abstract

Objective: Cardiovascular magnetic resonance imaging (CMR) late gadolinium enhancement technique (LGE) detects thrombus rather than anatomical presence based on tissue properties and is theoretically highly accurate. The present study's goal was to compare the diagnostic accuracy obtained with various CMR techniques and transthoracic echocardiography to diagnose left ventricular thrombus and evaluate the prevalence and perspectives of left ventricular (LV) thrombus among patients with impaired systolic left ventricular function. Methods: In a single academic referral center, a retrospective database review of all CMR assessments of the established left ventricular thrombus was carried out in 206 consecutive patients with reduced systolic function for five years. To assess thrombus risk factors, clinical and imaging parameters were analyzed. Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), echocardiography, and cine-CMR sequence accuracy have been identified. LV structural parameters were quantified to detect markers for thrombus and predictors of the additive usefulness of contrast-enhanced thrombus imaging. Comparisons against LGE-CMR were made, which was used as the standard. Results: A 7.8 percent prevalence of left ventricular thrombus was identified by LGE-CMR. Cine-CMR increased the diagnostic efficiency for echocardiographic thrombus identification in this group, with sensitivity increasing from 50 percent by echocardiography to 75 percent by cine-CMR (p = 0.008). Dark blood CMR (DB-CMR) has better sensitivity and accuracy than echocardiography (p < 0.001), comparable to cine-CMR. The transmural infarct size was an independent marker for thrombus after correction for the LVEF and LV volume while considering only CMR parameters. There were significantly higher embolic events (HR = 71.33; CI 8.31-616.06, p < 0.0001) in LV thrombus patients detected by LGE-CMR. Conclusion: CMR imaging was more sensitive to left ventricular thrombi identification compared with transthoracic echocardiography. An additional parameter available from LGE-CMR and shown as an independent risk factor for left ventricular thrombus is the myocardial scar.

Keywords: cardiac MRI; late gadolinium enhancement; left ventricular thrombi.

Figure 1

Examples of discordance between echocardiography and CMR. (A) Echocardiography was interpreted as negative. (B: arrow) LV apical thrombus demonstrated on cine-CMR, (C: arrow) DB-CMR, (D: arrow) standard LGE-CMR with an inversion time of 250–350 ms, and (E: arrow) long inversion time with inversion time = 600 ms. LGE-CMR. (D: dashed arrows) Myocardial scar at the anteroseptal segment of the left ventricle was demonstrated on LGE-CMR. Surgical resection enabled thrombus verification based on histopathology (not shown). (CMR: Cardiac magnetic resonance imaging, LGE-CMR: Late gadolinium enhancement sequence, DB-CMR: Dark blood sequence).

Figure 2

Example of false-negative cine-CMR and DB-CMR. Echocardiography was interpreted as negative (not shown). LV apical thrombus was not detected on (A) cine-CMR and (B) DB-CMR. LV apical thrombus was demonstrated on standard LGE-CMR with an inversion time of (C: arrow) 250–350 ms and (D: arrow) long inversion time with inversion time = 600 ms. This patient subsequently obtained antithrombotic medication after CMR. (CMR: Cardiac magnetic resonance imaging, LGE-CMR: Late gadolinium enhancement sequence, DB-CMR: Dark blood sequence).

Figure 3

Kaplan–Meier curve for embolic events for the patients with LV thrombus detected by LGE-CMR (red line) and the patients who did not discover LV thrombus by LGE-CMR (blue line).

Figure 4

The receiver operating characteristic (ROC) curves of the left ventricular thrombi diagnostic performance from cine-CMR (solid blue line), DB-CMR (dashed green line), and echocardiography (dotted red line).