Incidence and predictors of left ventricular thrombus by cardiovascular magnetic resonance in acute ST-segment elevation myocardial infarction treated by primary percutaneous coronary intervention: a meta-analysis

Abstract

Introduction: The incidence of left ventricular (LV) thrombus formation in ST-segment elevation myocardial infarction (STEMI) patients in the current era of primary percutaneous coronary intervention (PCI) is not well established. We performed a meta-analysis to assess the actual incidence and predictors of LV thrombus by cardiovascular magnetic resonance (CMR) in STEMI treated by primary PCI.

Methods: We searched MEDLINE and EMBASE databases up to February 2018. We included all studies published as a full-text article, reporting the incidence of LV thrombus by CMR within 1 month following acute STEMI in patients treated by primary PCI. A binary random-effects model was used to estimate the pooled incidence of LV thrombus. The diagnostic performance of transthoracic echocardiography (TTE) as compared with CMR was pooled to obtain the sensitivity and specificity of TTE with CMR as the gold standard. Embolic and bleeding complications of LV thrombus were also evaluated.

Results: Ten studies were included in the meta-analysis. The incidence of LV thrombus by CMR in all-comer STEMI patients (n = 2072) was 6.3% with 96% of LV thrombus occurring in those with anterior STEMI (12.2% incidence). When only anterior STEMI with LVEF< 50% were considered (n = 447), the incidence of LV thrombus was 19.2%. Compared with CMR, the sensitivity of TTE to detect LV thrombus was 29% with a specificity of 98%. The sensitivity of TTE increased to 70% in those with anterior STEMI and reduced LVEF. LV thrombus resolved in 88% of cases by 3 to 6 months. After 1-2 years follow-up, the embolic complication rate was similar at 1.5% (P = 0.25) but the bleeding complication rate was significantly higher (8.8% versus 0.5%, P < 0.001) in the LV thrombus group on triple therapy when compared to the no LV thrombus group on dual antiplatelet therapy.

Conclusion: In the primary PCI era, CMR detection of an LV thrombus post-STEMI remains high with incidence of nearly 20% in anterior STEMI with depressed LVEF. Patients with LV thrombus treated by triple therapy had similar embolic complications but higher bleeding complications than those with no LV thrombus treated with dual antiplatelet therapy. A 3 month follow-up CMR scan to guide anticoagulation duration might help mitigate bleeding risk.

Keywords: Cardiovascular magnetic resonance; Left ventricular thrombus; Primary percutaneous coronary intervention; ST-segment elevation myocardial infarction.

Fig. 1

PRISMA flow diagram of the study selection process. This is the PRISMA flow diagram showing how studies were identified, screening and included in this meta-analysis

Fig. 2

Forest plot of incidence of left ventricular (LV) thrombus by cardiovascular magnetic resonance (CMR) in ST elevation myocardial infarction (STEMI) patients treated by primary percutaneous coronary intervention (PCI). Forest plot showing the overall incidence of LV thrombus in STEMI and those with an anterior STEMI

Fig. 3

Early post-contrast CMR images of LV thrombus from 3 patients with acute STEMI treated by primary PCI. These 4-chamber views from 3 different patients illustrate LV thrombus of different sizes (red arrow) identified from the early post-contrast images acquired at high inversion time to null the avascular thrombus and MVO as black

Fig. 4

Algorithm for the detection of LV thrombus in reperfused STEMI patients in the clinical setting. This algorithm provides guidance on how STEMI patients at risk could be identified and how TTE and CMR could be integrated in the clinical setting to optimize the detection of LV thrombus

Fig. 5

Differences in appearance between LV thrombus and microvascular obstruction (MVO). These are the early and late post-contrast short-axis images from a patient with LV thrombus and MVO. The red arrows show the LV thrombus and the blue arrows delineate the MVO