American Heart Association

diagnosis and imaging

To TEE or Not to TEE?

Kevin O’Connor, MD

Thomalla G, Upneja M, Camen S, Jensen M, Schröder J, Barow E, Boskamp S, Ostermeier B, Kissling S, Leinisch E, et al. Treatment-Relevant Findings in Transesophageal Echocardiography After Stroke: A Prospective Multicenter Cohort Study. Stroke. 2021.

About one fifth of acute ischemic strokes and transient ischemic attacks stem from cardioembolism. Although cardiac ultrasound is generally recommended as a reasonable diagnostic study, there is ongoing debate on the utility of transthoracic echocardiography (TTE) versus transesophageal echocardiography (TEE). In practice, TTE may be preferred as it is less invasive and easier to obtain but at the expense of decreased sensitivity when evaluating for some pathologies involving the aorta and left atrium. Thomalla et al. designed the Comparative Effectiveness Study of Transthoracic and Transesophageal Echocardiography in Stroke (CONTEST) study to compare the diagnostic yield of treatment-relevant findings (i.e., findings sufficient to justify a change in medication, intervention, or surgery) of TTE and TEE in patients with acute ischemic stroke, transient ischemic attack, or retinal ischemia of undetermined cause. Despite early study termination due to funding cessation, 494 patients were enrolled with 454 undergoing both TTE and TEE.  

The Tissue Clock: “Prediction of Stroke Infarct Growth Rates by Baseline Perfusion Imaging”

Tolga D. Dittrich, MD

Wouters A, Robben D, Christensen S, Marquering HA, Roos YBWEM, van Oostenbrugge RJ, van Zwam WH, Dippel DWJ, Majoie CBLM, Schonewille WJ, et al. Prediction of Stroke Infarct Growth Rates by Baseline Perfusion Imaging. Stroke. 2021.

For the acute treatment of ischemic stroke with endovascular therapy (EVT), the time between symptom onset and therapy initiation is considered crucial so far. However, the trend has shifted in recent years from rigid time windows to more individualized, advanced imaging-based, patient selection for EVT.

CT-based perfusion imaging (CTP) has gained importance in identifying individuals with potentially salvageable brain tissue. Automated perfusion assessments using specialized software (e.g., RAPID) are frequently employed in clinical practice to calculate mismatch volume. For the analysis, two key parameters are defined: the relative cerebral blood flow (rCBF) below 30% as a reflection of the ischemic core volume and the delay to the maximum of the residue function (Tmax) of more than 6 seconds, which defines critically hypoperfused brain tissue. The final infarct volume often corresponds with the ischemic core volume determined at baseline in cases of successful reperfusion. In patients without reperfusion, the size of the hypoperfused brain tissue can be used to predict the final infarct size. However, accurate prediction of final infarct size, especially as a function of reperfusion status, is not possible using these conventional CTP analyses as they only represent snapshots at the time of examination.

ASPECTS Score as a Biomarker to Predict Clinical Outcome

Arooshi Kumar, MD

Liebeskind DS, Saber H, Bhuva P, Xiang B, Yoo AJ, Jadhav AP, Haussen DC, Budzik RF, Bonafe A, Yavagal DR, et al. Serial ASPECTS in the DAWN Trial: Infarct Evolution and Clinical Impact. Stroke. 2021;52:3318–3324.

With the rapid adoption of endovascular therapy (EVT) for selected ischemic stroke patients, there remains a need to identify practical biomarkers to help predict treatment efficacy and clinical outcomes. The Alberta Stroke Program Early CT Score (ASPECTS) grading system is a well-accepted method to capture the degree of brain injury following stroke in the anterior circulation.1,2 While it has emerged as one standard method to quantify degree of ischemia and select candidates for endovascular treatment (EVT), the utility of post-intervention ASPECTS scores remains unclear.

To that end, a secondary SWIFT analysis demonstrated that post-treatment ASPECTS score was a reliable predictor of 90-day clinical function after stroke for presenting in the early intervention window (< 6hours).3 This study aimed at investigating the relevance of post-treatment ASPECTS score for later presenting window (6-24 hours) patients with ischemic stroke using the DAWN trial results. In this study, the ASPECTS score, initial and after 24 hours, was tabulated from 81 CT-CT pairs, 56 CT-MRI pairs, and 66 MRI-MRI pairs.

Estimating Residual Flow With Thrombus Perviousness and its Effect on Outcome in LVO Stroke

Vignan Yogendrakumar, MD, MSc
@VYogendrakumar

Kappelhof M, Tolhuisen ML, Treurniet KM, Dutra BG, Alves H, Zhang G, Brown S, Muir KW, Dávalos A, Roos YBWEM, et al. Endovascular Treatment Effect Diminishes With Increasing Thrombus Perviousness: Pooled Data From 7 Trials on Acute Ischemic Stroke. Stroke. 2021.

In the context of large vessel occlusion stroke, a growing number of advanced imaging studies are showing us that no two occlusions are alike. The imaging features of a thrombus can provide critical information that can inform us about the effectiveness of a given therapy. For example, the INTERRSeCT study published in 2018 showed that distal thrombus location and increased thrombus permeability were associated with increased rates of spontaneous recanalization with IV thrombolysis.

In this study, Kappelhof and colleagues utilize data from the HERMES dataset to assess thrombus permeability and determine its effect on clinical outcomes in patients who received EVT compared to those who received thrombolysis alone. The authors refer to permeability as “thrombus perviousness” and measured this by co-registering non-contrast CT (NCCT) and single-phase CTA images together and measuring the attenuation increase between NCCT and CTA images (Figure 2). The primary clinical outcome of the study was an ordinal analysis of the mRS.

Figure 2. Thrombus attenuation
increase measurement.
Figure 2. Thrombus attenuation increase measurement.

Author Interview: Dr. Tharani Thirugnanachandran on “Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography”

Dr. Tharani Thirugnanachandran
Dr. Tharani Thirugnanachandran

A conversation with Dr. Tharani Thirugnanachandran, MBChB, stroke researcher, Monash University, Victoria, Australia.

Interviewed by Dr. Andy Lim, MBA, emergency physician, Monash Medical Centre, Victoria, Australia.

They will be discussing the article “Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography,” published in Stroke.

Dr. Lim: Dr. Thirugnanachandran, on behalf of the Blogging Stroke team, it is a pleasure to welcome you to this author interview regarding your publication in Stroke that explored the role of leptomeningeal anastomoses in influencing infarct topography after anterior cerebral artery stroke. Can I start by asking you to give us a brief summary of what you did?

Dr. Thirugnanachandran: Thank you, Dr Lim. Anterior cerebral artery stroke is far less common than middle cerebral artery stroke. So comparatively less attention has been given to it in the literature. Much of our current understanding about it has come from older works taken postmortem or poststroke. In contrast to prior studies, our study was able to give us an insight into what happens to this arterial territory at stroke onset with the use perfusion imaging and a computer model.

Spoiler Alert in ACA Strokes: It’s All About Collaterals

Elena Zapata-Arriaza, MD PhD
@ElenaZaps

Thirugnanachandran T, Beare R, Mitchell M, Wong C, Vuong J, Singhal S, Slater LA, Hilton J, Sinnott M, Srikanth V, et al. Anterior Cerebral Artery Stroke: Role of Collateral Systems on Infarct Topography. Stroke. 2021.

Anterior cerebral artery (ACA) stroke is less frequent when compared with middle cerebral artery (MCA) occlusion, and consequently, mechanical thrombectomies, perfusion studies, pial collateral system or clinical consequences based on the topography of the lesion are less known. With the aim of evaluating the role of the circle of Willis (CoW) and leptomeningeal anastomoses (LA) in modifying regional variation in infarct topography following occlusion of the anterior cerebral artery and its branches, Thirugnanachandran and colleagues employed voxel-based imaging in conjunction with computer model of cerebral circulation to understand the temporal and spatial evolution of the topography of ACA stroke following vessel occlusion. The experiments included occlusion of successive branches of the anterior cerebral artery while the configurations of the CoW were varied.

Time is Brain, For Some More Than Others

Elena Zapata-Arriaza, MD
@ElenaZaps

Ospel JM, Hill MD, Kappelhof M, Demchuk AM, Menon BK, Mayank A, Dowlatshahi D, Frei D, Rempel JL, Baxter B, Goyal M. Which Acute Ischemic Stroke Patients Are Fast Progressors? Results From the ESCAPE Trial Control Arm. Stroke. 2021;52:1847-1850.

Time is brain; however, there are patients for whom that time runs faster. Penumbra brain tissue, due to large vessel occlusion, tends to progress to ischemia in the absence of intracranial reperfusion. However, there are a number of conditions that cause a faster progression (rapid progressors) or not, even in those who will receive endovascular treatment. To identify acute ischemic stroke patients with rapid infarct growth, Ospel and colleagues performed a post hoc analysis of the ESCAPE trial (Endovascular Treatment for Small Core and Proximal Occlusion Ischemic Stroke) in order to investigate baseline clinical and imaging characteristics of fast progressors stroke patients.

The authors included control arm patients if they had follow-up imaging at 2-8 hours without substantial recanalization, and if their baseline Alberta Stroke Program Early CT Score was ≥9. Fast infarct progression was defined as Alberta Stroke Program Early CT Score decay ≥3 points from baseline to 2- to 8-hour follow-up imaging.

The Role of Time and Collateral Status on Ischemic Core Overestimation on CT Perfusion

Tolga Daniel Dittrich, MD

García-Tornel Á, Campos D, Rubiera M, Boned S, Olivé-Gadea M, Requena M, Ciolli L, Muchada M, Pagola J, Rodriguez-Luna D, et al. Ischemic Core Overestimation on Computed Tomography Perfusion. Stroke. 2021.

Computed tomography perfusion (CTP) has become widely accepted as the imaging modality for the estimation of the infarct core and subsequent selection for endovascular treatment (EVT) in ischemic stroke due to large vessel occlusion (LVO), especially in the late time window. The radiological correlate for the core in CTP is usually the volume of tissue with a (compared with the contralateral hemisphere) reduction in cerebral blood flow (CBF) <30%. Overestimation of the core in CTP is thought to be time-dependent and may be a concern, especially with rapid imaging after symptom onset and fast reperfusion after imaging.

García-Tornel et al. addressed the question of the influence of time and collateral status on ischemic core overestimation. They retrospectively evaluated patients with anterior circulation LVO strokes with successful reperfusion after EVT. The core was considered to be the tissue with CBF <30% in CTP. Collateral status was assessed by the hypoperfusion intensity ratio (time to maximum of tissue residue function >6 seconds/time to maximum of tissue residue function >10 seconds). The reference for the final infarct volume was the non-contrast CT after 24 to 48 hours.

What Happens to Busted Clots After Using the Clot Buster?

Kevin O’Connor, MD

Ohara T, Menon BK, Al-Ajlan FS, Horn M, Najm M, Al-Sultan A, Puig J, Dowlatshahi D, Calleja Sanz AI, Sohn SI, et al.; for INTERRSeCT Study Investigators. Thrombus Migration and Fragmentation After Intravenous Alteplase Treatment: The INTERRSeCT Study. Stroke. 2021;52:203–212.

Ohara et al. conducted a post hoc analysis of data collected in the INTERRSeCT study (Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion With IV Alteplase and Other Treatments Using Serial CT Angiography) to study thrombus changes in ICA or MCA occlusions following IV t-PA and whether this affected clinical outcomes. The 427 INTERRSeCT study patients underwent baseline CTA as well as repeat CTA or conventional angiogram following IV t-PA administration. The investigators compared the proximal position of the clot on baseline and repeat imaging, and if it migrated, they graded the degree of movement on a 0-3 scale with higher grades indicating more distal movement. If there was no change in proximal position, they assessed thrombus fragmentation determined by the presence of a new thrombus in a distal artery. A 90-day modified Rankin Scale score ≤2 was considered a good outcome.

Left Atrial Appendage Thrombus in Patients with Ischemic Stroke as Marker of Atrial Fibrillation?

Wern Yew Ding, MBChB

Senadeera SC, Palmer DG, Keenan R, Beharry J, Yuh Lim J, Hurrell MA, Mouthaan P, Fink JN, Wilson D, Lim A, Wu TY. Left Atrial Appendage Thrombus Detected During Hyperacute Stroke Imaging Is Associated With Atrial Fibrillation. Stroke. 2020;51:3760–3764.

Atrial fibrillation (AF) is an established risk factor for thromboembolic events, including ischemic stroke. Therefore, identification of patients with this arrhythmia is important to facilitate the implementation of stroke prevention therapy using oral anticoagulation. Nonetheless, as a significant proportion of patients with AF remain asymptomatic, it remains largely under-diagnosed in the general population. Given that the source of emboli in the majority of AF-related strokes originates from the left atrial appendage (LAA), inclusion of this structure in imaging protocols may have a role in aiding the diagnosis of AF.

In a recent retrospective study of consecutive patients with ischemic stroke or transient ischemic attack, Senadeera and colleagues investigated the prevalence of computed tomography angiography (CTA)-detected LAA thrombus during hyperacute stroke imaging and evaluated the association between LAA thrombus and AF. The imaging protocol consisted of non-contrast CT, followed by CT perfusion and CTA from aortic arch to vertex. Two experienced physicians and pre-defined measures were used to assess for LAA thrombus on these scans.