Clinical Significance of the Characteristics of Microembolic Signals Recorded in the Recovery Period of Ischemic Stroke, a Cross-Sectional Observational Study

Abstract

Background. Microembols detected during transcranial Doppler monitoring with microembolodetection (TCDM with MED) are different in nature and, accordingly, in structure, as well as in size and consequences of their impact on the cerebral vessels. The following biophysical characteristics of microembolic signals (MES) can be assessed during TCDM with MED: frequency, which indirectly reflects the structure of the microembolus, duration, which indirectly reflects the size of the microembolus, and power, which is an integral characteristic. The issues of the relationship between characteristics of MES and clinical indicators have been little studied according to literature.
 Aims study of the biophysical characteristics of microembolic signals recorded in patients with ischemic stroke, as well as the factors affecting these characteristics, the clinical and prognostic significance of microembolism.
 Methods. This is a cross-sectional observational study that is part of a prospective cohort study. Data on 28 patients in the recovery period of ischemic stroke are included, in whom the biophysical characteristics of MES were analyzed (the total number of cases in the cohort study was 1600), and who underwent: duplex scanning of the brachiocephalic arteries, transcranial duplex scanning, TCDM with MED, transthoracic echocardiography, magnetic-resonance tomography of the brain, electrocardiography. Study enrollment was carried out in the period from 2019 to 2021. The MES characteristics included frequency, duration, power, energy index (the product of power and duration), of which the MES power was the main one.
 Results. MES characteristics correlated with anthropometric parameters: average duration - with the patients age (r = 0.421; p = 0.029); average frequency with body surface area (r = 0.624; p = 0.010). The average power, duration and energy index of MES were significantly higher in persons with intraluminal masses in the carotid arteries (p 0.05). Correlations of biophysical characteristics of MES with blood flow velocities in brain vessels (inverse correlation between the duration of the MES and the value of the peak systolic velocity in the M2 segment of the right MCA r = 0.529, p = 0.02; correlations between the power of MES, as well as the duration of MES with peak systolic and end-diastolic velocities in the V4 segment of the right VA r = 0.4810.572, p = 0.0270.007), as well as with signs of atrophy of the temporal and occipital lobes of the brain were identified (inverse correlation between MES frequency and regional atrophy in the right temporal lobe r = 0.434, p = 0.038; inverse correlation between MES frequency and regional atrophy in the left temporal lobe r = 0.422, p = 0.045; inverse correlation between MES frequency and regional atrophy in the left occipital lobe r = 0.465, p = 0.025). Significant differences were found in the number of MES and their average power, duration, energy index in the presence and absence of atrial fibrillation (p 0.05).
 Conclusions. Age and, apparently, weight, as well as signs of atherosclerosis of the brachiocephalic arteries, influence the development of microembolism. In the presence of atrial fibrillation, material microembolism is observed predominantly, and the number of MES and their characteristics which reflect the size of microemboli are significantly higher. The relationship between the duration of MES and the characteristics reflecting the blood supply in the basin of the middle cerebral artery, as well as between the frequency of MES and the presence of regional atrophy in the temporal and occipital lobes of the brain according to magnetic resonance imaging was revealed.