This prospective cohort study enrolled 62 patients who were presented with cerebrovascular stroke or TIA and were referred to the cardiology department for cardiac evaluation. Another 40 participants with no previous medical history of implication were included as a control group for comparison of left atrial function to those patients with cryptogenic stroke.

So, participants were divided into two groups after conducting TEE for all participants and exclusion of possible etiologies of cardio-embolism: Group I (40 cryptogenic stroke patients) and Group II, which included healthy participants as the control group. Participants of Group I were divided into Group Ia (AF recorded group) and Group Ib (non-AF registered group). Our study was approved by the Local Institutional Human Research Ethics Committee, and participants provided written informed consent.

This study included female and male patients with confirmed cerebrovascular ischemic stroke, diagnosed through brain imaging (utilizing brain CT or MRI to rule out primary intracranial hemorrhage), and individuals who experienced transient ischemic attacks.

Exclusion criteria for cardio-embolism/stroke risk include patients with persistent or paroxysmal atrial fibrillation (all participants with paroxysmal atrial fibrillation less than 30 s were excluded), aortic or mitral valvular metallic prostheses, moderate or severe valvular lesions, a history of CAD, LVEF < 50%, intra-cardiac mural thrombi or shunts, significant carotid artery stenosis (> 50% by sonography), uncontrolled hypertension, known aortic aneurysms, metabolic or electrolyte disorders, thyroid dysfunction (a risk factor for atrial fibrillation), and a history of recognized stroke causes like Polycythemia rubra vera or Anti-phospholipid syndrome. These criteria are vital for patient selection in medical interventions or studies, ensuring safety and minimizing embolic risk.

All patients were subjected to the following screening steps:

(i)

Full history tracking:

(a)

Risk factors such as gender, age, smoking, diabetes mellitus, hypertension, dyslipidemia, and positive family history of the ischemic event, either cerebral vascular or cardiac event.

(b)

Drug history, including medications and doses.

(c)

Previous and existing cardiac problems like ischemic heart diseases and heart failure.

(d)

Other medical problems.

(ii)

General and local cardiac examination:

It involves arterial blood pressure measurement, body weight, height, pulse, body mass index, and body surface area.

(iii)

Resting 12-leads surface ECG: to exclude arrhythmia, atrial fibrillation, paroxysmal or persistent CAD, or cardiac chambers dysfunction, and also for detection of left atrial cardiopathy markers as P wave duration, PTFV1.

(iv)

Laboratory: the routine laboratory investigations in patients with cerebrovascular stroke as complete blood count, renal and hepatic profiles, coagulation profile, and total Lipid profile parameters, including serum triglycerides, serum cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and non-HDL cholesterol.

Echocardiography was performed using The ACUSON SC2000 PRIME ultrasound system, Siemens, Germany. An echocardiographic study was done using 2D, M-mode, and Doppler and tissue Doppler techniques. All study participants were examined while in the left lateral recumbent position and instructed to refrain from deep inhalation or performing the Valsalva maneuver. Systolic and diastolic functions of LV were assessed, LA anteroposterior diameter was measured in PLAX view, LA maximal and minimal volumes in biplane (apical 4 and apical 2 chambers) view, LA volume index (LAVI) which was considered by (LA maximal volume / BSA). Also, the LA emptying volume was evaluated by assessing the LA maximum and LA minimum volume difference. LA ejection fraction (LAEF) was estimated by the LA emptying/maximum volume.

LV diastolic function was assessed by mitral inflow pattern in apical 4 chambers view and calculating E/A ratio. 'E' wave represents the early ventricular diastole, and 'A' wave represents the atrial contraction and septal tissue Doppler velocities to estimate e`/a,` e` represents early diastolic annular velocity, a' represents the annular late diastolic velocity, following the European Association of Cardiovascular Imaging and the American Society of Echocardiography recommendations, updated in 2016.

For TEE evaluation, an ultrasound system using (Siemens Acuson SC2000) using a "Z6Ms" transducer or (Philips iE33) using an "xMATRIX TEE X 7-2t" transducer was used. All of the patients were in fasting condition for a minimum of 4 h before the procedure. Oxygen saturation and blood pressure were evaluated. Local pharyngeal anesthesia with 2% lidocaine spray was used along with low-dose intravenous midazolam.

Standardized transesophageal echocardiography (TEE) images were acquired using mid-esophageal views, including the 4 chamber, mitral commissural, 2 chamber, long axis, ascending aorta long axis, aortic valve short axis, bicaval, and right ventricular inflow–outflow views. Furthermore, a multi-planar assessment of the left atrial appendage (LAA) was implemented. In cases where the inter-atrial shunt was not observed via color flow Doppler in the bicaval view, agitated intravenous saline was managed for further assessment. Furthermore, additional standard images of the descending aorta and aortic arch in both short and long axes were captured to complete the evaluation. LA and LAA in multiple angles were evaluated for spontaneous echocardiographic contrast (SEC) and/or thrombus formation. Thrombus was identified as echodensity with distinct borders, observed in various views, and autonomous from an endocardium. SEC was defined with the echo-dense smoke-like motion.

A saline contrast study was administered through normal respiration and the Valsalva maneuver to assess the inter-atrial septum accurately. The PFO presence was established based on micro-bubbles direct visualization passing through the atrial septum to LA by recording three consecutive cardiac cycles after complete opacification of the right atrium or detecting color Doppler flow through the atrial septum. The use of TEE in our study searches for objective evidence for embolic stroke as a routine workup in cryptogenic stroke to exclude cardio-embolic sources such as PFO, LAA appendage thrombi, or even SEC or significant aortic plaques.

High-risk PFO for paradoxical embolism is defined as Large PFO size (septum primum maximum separation from the secundum throughout the Valsalva maneuver) ≥ 2 mm on TEE, presence of inter-atrial septal aneurysm (dilated segment protrusion of the septum at least 15 mm beyond the atrial septum level surface) or hypermobility. Significant aortic arch/ ascending aorta plaques were defined as ≥ 4 mm in thickness.

Speckle tracking study for LA was performed on all members of the study population. From the apical 4 chamber and 2 chamber views 202 with a stable ECG recording, the left atrium will be visualized as clearly as possible, permitting reliable delineation of myocardial tissue and extra-cardiac structures. The non-foreshortened tracing was started at the mitral annulus endocardial border, extrapolating across the pulmonary veins and/or LA appendage orifices by employing the apical four chamber. Most studies recommend biplane apical 2 and apical 4 chambers views in echocardiographic assessment of LA by 2D-STE; however, using a single apical view (apical 4 chambers view) may be accepted and provides the LA strain normal reference values throughout the reservoir, contraction phases, and conduit. Cine-loops of the left atrium (LA) from well-optimized LA-focused images ensure the maximum LA length and base inclusion in each view.

A frame rate of 40–90 frames/three consecutive cardiac cycles was used. LA Cine-loops were captured from well-optimized LA-focused images to maximize the inclusion of the length and base of LA. The used settings were selected to merge temporal resolution with suitable spatial definition and improve the frame-to-frame tracking technique feasibility. Images are recorded and analyzed offline using the speckle tracking software.

The aim of using 2D Speckle tracking echocardiography in our study is to assess left atrial mechanical dysfunction when TEE could not explain the source of cardio-embolism and as an important diagnostic tool for early prediction of subclinical AF 205. The left atrial ejection fraction (LAEF) and left atrial reservoir strain rate (LASr) were used to evaluate left atrial function.

Bilateral carotid artery ultrasonography was performed on all participants of the study. All patients with significant carotid artery atheromatous plaques with more than 50% stenosis were excluded. Plaque was characterized as a localized structure protruding into the arterial lumen, displaying a thickness exceeding 2 mm, evaluated from the interface between the intima and lumen to the interface between the media and adventitia. Non-obstructive carotid atherosclerosis (NOCA) is less than 50% of carotid artery atherosclerosis.

ECG rhythm monitoring during hospitalization

All participants were monitored for ECG rhythm abnormality for 48 h during hospitalization in the stroke unit. Episodes of atrial fibrillation more than 30 s during the 48 h were recorded.