Echocardiography reveals hidden paroxysmal atrial fibrillation in older adults

Researchers say two non-invasive echocardiographic measures, the left atrial stiffness index (LASI) and left atrial activation time (LA-AT), were markedly higher in older adults with newly diagnosed, symptom-free paroxysmal atrial fibrillation (PAF) than in age-matched controls. The open-access findings, published in Cardiovascular Ultrasound, are based on a retrospective analysis from the STROKESTOP2 study and indicate that early atrial remodeling may be detectable before the left atrium becomes visibly enlarged.

The study included people with newly diagnosed PAF and a randomly chosen age-matched control group without atrial fibrillation, all drawn from the STROKESTOP2 cohort. All participants had NT-proBNP levels between 125 and 900 ng/L, a range consistent with mild elevation rather than overt heart failure. Transthoracic echocardiograms were reviewed retrospectively offline with specialized software. Along with standard measurements, LA-AT was calculated from the time delay between the start of the P-wave on the ECG and the tissue Doppler Á peak wave in the lateral wall of the left atrium.

The average age of the cohort was 76 ± 0.3 years. There were 67 participants in the PAF group and 94 in the control group. Silent PAF was associated with a significantly higher LASI, with a median of 0.41 (interquartile range 0.29–0.60) compared with 0.32 (0.29–0.43) in controls, P = 0.001. Left atrial activation time was also longer at 170 ms (140–180) versus 140 ms (120–144), P < 0.001. Together, these findings point to greater passive stiffness of the atrial chamber and slower electrical conduction across the lateral atrial wall in the fibrillation group.

A subgroup analysis reinforced the result. Even among participants whose left atrial volume index (LAVI) stayed within normal limits at ≤ 34 ml/m², LASI and LA-AT remained significantly elevated and prolonged in the PAF group (n = 27) compared with controls (n = 72). This suggests the echocardiographic markers can detect functional and conduction abnormalities before the atrium shows measurable structural enlargement, a stage at which standard size-based screening would still appear normal.

NT-proBNP levels, however, did not differ meaningfully between the two groups: 228 ng/L (interquartile range 181–348) in the PAF group versus 216 ng/L (156–317) in controls, P = 0.18. In this mildly elevated range, the biomarker did not distinguish the groups, while the echocardiographic indices did. Receiver operating characteristic (ROC) analysis identified cutoffs of LASI > 0.54 and LA-AT > 139 ms for detecting silent PAF in this population.

The authors conclude that measures of left atrial stiffness and atrial conduction delay were significantly increased in patients with recently diagnosed PAF, and that LASI and LA-AT thresholds may offer a non-invasive way to detect early atrial remodeling without structural enlargement in older patients at high risk of PAF who have mildly raised NT-proBNP levels. Because the analysis was retrospective and limited to a specific screened older population with a defined biomarker range, these thresholds will need validation in other cohorts before clinical use. The study was released as an accepted manuscript for early access and can be cited using a permanent DOI, while further editorial processing continues before the final version of record is published.

Subject of Research: Echocardiographic markers of left atrial stiffness and conduction delay in silent paroxysmal atrial fibrillation

Article Title: Echocardiographic markers for left atrial stiffness and left atrial conduction delay in patients with silent paroxysmal atrial fibrillation compared to age-matched controls

Article References: Bastos, L., Al-Khalili, F., Bäck, M., Manouras, A., Engdahl, J., & Shahgaldi, K. (2026). Echocardiographic markers for left atrial stiffness and left atrial conduction delay in patients with silent paroxysmal atrial fibrillation compared to age-matched controls. Cardiovascular Ultrasound. https://doi.org/10.1186/s12947-026-00395-1

Image Credits: AI Generated

Keywords: atrial fibrillation, echocardiography, left atrial stiffness index, left atrial activation time, NT-proBNP, STROKESTOP2, paroxysmal atrial fibrillation, left atrial strain, ROC analysis, elderly screening, atrial remodeling, Cardiovascular Ultrasound