Abstract
Background: The magnetocardiogram (MCG) is a promising medical tool for detecting and visualizing abnormal cardiac electrical activation in cardiovascular disease patients. MCG has higher spatial resolution than the electrocardiogram (ECG) because the magnetic field is not distorted by flow through tissues. Taking advantage of these features, MCG has been applied for studying arrhythmia, such as atrial fibrillation (AF) and long-QT syndrome. Paroxysmal AF is the most common sources of thromboembolism for ESUS. Since factors that reflect left atrial overload (LAO) are independent predictors of paroxysmal AF, evaluation of these factors in ESUS patients is essential to improve their prognosis. We aimed to investigate the potential utility of MCG in ESUS patients for evaluation of the factors that reflect LAO. Methods: ESUS patients who underwent MCG (MC-6400 MCG system with 64 magnetic sensors) in our hospital were enrolled between September 2018 and July 2021. The peak P-wave magnitude of the right atrium segment and the left atrium segment on the MCG (MCG-RA, MCG-LA) were measured. Subsequently, the ratio of peak magnitude of the LA segment to that of the RA segment (MCG-LA/RA) was used to evaluate LAO. Other factors that reflect LAO, such as PAC frequency on Holter monitoring, LAD in transthoracic echocardiography (TTE), serum level of brain natriuretic peptide, left ventricular ejection fraction (LVEF) in TTE, and P-wave terminal force in lead V1 (PTFV1) on ECG were also evaluated. Results: Fifty-two ESUS patients with a mean age of 67.9±14.3 years (females, 42%) were included. The mean MCV-RA and MCG-LA were 7.70±12.82 and 4.50±7.74 pico-Tesla, respectively. The mean MCG-LA/RA was 0.66±0.31. The MCG-LA/RA was significantly correlated with the PAC frequency (r=0.293, p=0.039), although either MCG-RA or MCG-LA was not correlated. Also, the MCG-LA/RA ratio was significantly correlated with LAD (r=0.301, p=0.03) but not with brain natriuretic peptide (r= 0.25, p= 0.09), LVEF (r= -0.06, p= 0.654), or PTFV1 (r= 0.02, p=0.91). Conclusion: This is the first study that evaluated the relationship of the MCG-LA/RA ratio with factors that reflect LAO in ESUS patients. These results suggest that the MCG-LA/RA ratio is a novel biomarker for LAO in ESUS patients.
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