ECG-gated cardiac CT to detect cardiac thrombi in ischemic stroke: a practical way forward?

Defining the etiology of ischemic stroke is paramount for optimal secondary prevention. Despite wide screening, up to 50% of ischemic stroke cases the diagnostic work-up turns out negative, with no cardioembolic, atherothrombotic or specific cause fully explaining the vascular event¹.

Finding a cardioembolic origin of an ischemic stroke opens the way to anticoagulation, which has clear advantage in the prevention of embolism compared to antiplatelets. Beyond atrial fibrillation, a leading cause of cardioembolic stroke, other sources of cardiac embolism exist, including cardiac thrombi². In this Issue of the European Stroke Journal, Leon Rinkel and the Amsterdam UMC team led by Jonathan Coutinho report the results from the Mind the Heart study, a prospective cohort study investigating the yield of cardiac CT in acute ischemic stroke³. Overall, 452 consecutive patients underwent ECG-gated cardiac CT during hyperacute stroke imaging, with 38 being found with cardiac thrombi (8.4%). Location of the thrombus spanned left atrial appendage (82%), left atrium (5%) and left ventricle (18%). Interestingly, trans-thoracic echocardiogram was performed in 350 patients and only identified two cases of cardiac thrombi (vs 38 with ECG-gated cardiac CT).

People with cardiac thrombus had a high frequency of atrial fibrillation (40% of cases), and had sub-therapeutic INR levels (<2) in 44% of cases. People with cardiac thrombus received similar reperfusion strategies compared to patients without cardiac thrombi detected, but the presence of cardiac thrombus was an independent predictor of poor functional outcome (OR for shift analysis 2.22, ranging 1.16 to 4.23), and carried a 3% absolute higher risk of recurrent stroke³.

Overall, three main themes emerge from this brilliant research. First, as cardiac thrombi are more frequently detected in patients with atrial fibrillation, the relationship between atrial fibrillation and a lower rate of recovery might have finally come to light. Indeed, if echocardiography fails to detect 36/38 cases of thrombus in a cardiac chamber, one might wonder how many can be missed during standard diagnostic work-up in relation to timing of ascertainment and specificity. Therefore – second point – one might argue in favour of implementing a time-sparing diagnostic technique in the clinical routine, at least for patients at high risk of cardiac thrombus. Finally, immersed as we are in over-diagnosis and over-treatment, we should note that identifying a cardiac thrombus has direct impact on management, with anticoagulation to be started early on. As the standard diagnostic work-up with transthoracic echocardiography would likely result unremarkable, cardiac CT seems worth of implementation to test its yield on a larger scale.