Detecting Cardiac Thrombi in Acute Ischemic Stroke on Cardiac CT Versus Transoesophageal Echocardiography

Rationale:

Cardiac CT acquired during the acute stroke imaging protocol (acute cardiac CT) has recently been shown to have a superior diagnostic yield than transthoracic echocardiography, which is currently the most commonly used method to screen for structural sources of cardioembolism in patients with acute ischemic stroke. The most common finding on acute cardiac CT are cardiac thrombi located in the left atrium (LA) and specifically the left atrial appendage (LAA). The higher diagnostic yield of acute cardiac CT compared to TTE is partially explained because CT allows for better visualization of the LAA, but also because cardiac thrombi may dissolve in the first days after stroke. Whether acute cardiac CT is the optimal diagnostic modality for LA thrombi in stroke patients is unknown, since data comparing it to transoesophageal echocardiography (TEE), which is the reference standard to detect LA thrombi, are lacking. The general hypothesis of this study is that acute cardiac CT is the optimal method to detect LA thrombi in ischemic stroke patients, since TEE can miss LA thrombi that dissolve in the first days after stroke.

Objectives:

1. Determine whether acute cardiac CT has a higher diagnostic probability of detecting LA thrombi compared to TEE or repeated cardiac CT in the subacute phase of ischemic stroke by assessing the rate at which LA thrombi dissolve in the first days after ischemic stroke occurrence.
2. Determine the positive predictive value of acute cardiac CT compared to TEE for the detection of LA thrombi. Study design: Prospective, single-centre, observational cohort Study population: 39 patients of 18 years or older with acute ischemic stroke and a LA thrombus detected on cardiac CT acquired during the acute stroke imaging.

Main study parameters/endpoints:

1. Rate at which LA thrombi visualized on acute cardiac CT dissolve in the first days after ischemic stroke.
2. False-positive rate for detection of left atrial thrombi on acute cardiac CT compared to TEE. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Clinical and imaging patient data which are obtained as part of standard care will be prospectively collected after written informed consent. Patient with a LA thrombus on acute cardiac CT will undergo TEE for research purposes after obtaining written informed consent. TEE is semi-invasive and associated with a small risk of major complications (<0.2%). Patients will also be exposed to additional radiation (1.4 mSV) due to sequential cardiac CT after TEE. The Radiation Dose Committee deemed this to be an intermediate risk. In a small minority of patients (<10%), another cardiac CT will be acquired 2 minutes after this sequential cardiac CT to ensure a clear, final assessment of the presence of an atrial appendage thrombus. This will result in a total additional radiation of 3 mSV for the two additional cardiac CT's. The Radiation Dose Committee deemed this to be an intermediate risk. As part of standard care, patients will be contacted for follow-up evaluation by a trained stroke nurse at 90 days. As a result of ischemic stroke, some patients become incapacitated to an extent they are unable to give informed consent. In these cases, the legal representative will be asked for informed consent. Decreased leveI of consciousness or aphasia are typical clinical characteristics of cardioembolic stroke. Therefore, it is pivotal to also include incapacitated acute ischemic stroke patients. Excluding these patients from the study would render the study non-representative of the study's target population (acute ischemic stroke patients with cardioembolic stroke due to LA thrombus).