Echocardiographic markers for left atrial stiffness and fibrosis in patients with silent paroxysmal atrial fibrillation compared to age-matched controls

Purpose: To study left atrial stiffness index (LASI) and left atrial activation time (LA-AT) changes in an older population with silent paroxysmal atrial fibrillation (PAF) compared to age-matched control. Methods: Individuals with newly diagnosed PAF and a randomly selected age-matched control group without AF were enrolled from STROKESTOP2-study. All participants had NT-proBNP levels 125-900 ng/L. TTE examinations were analyzed retrospectively offline using dedicated software. Besides conventional echocardiographic measurements, LA-AT was obtained by measuring the time delay between the onset of the P-wave on ECG and tissue Doppler Á peak wave in lateral LA wall. LASI was calculated as the ratio of left ventricular filling (E/é) to peak atrial longitudinal strain (PALS) Results: Mean age was 76±0.3. The PAF group (n=67) presented significant increase of LASI (0.41 (0.29 – 0.60) vs. 0.32 (0.29 – 0.43), P=0.001) and prolonged LA-AT (170 (140 – 180) ms vs. 140 (120 – 144) ms, P<0.001) compared to controls (n=94). Subgroup analysis with normal LA volume index (LAVI) ≤34 ml/m , LASI and LA-AT remained significantly increased/prolonged in PAF (N=27) compared to controls (N=72). NT-proBNP-levels did not differ between PAF (228 (181–348) ng/L) and controls (216 (156–317) ng/L) (P=0.18). ROC curve analysis identified thresholds LASI>0.33 and LA-AT>139 msec for predicting silent PAF. Conclusions: Indices reflecting LA stiffness and fibrosis were significantly elevated in recently diagnosed PAF patients and elevated in the absence of LA dilatation. LASI and LA-AT thresholds might non-invasively provide additional information in patients with high risk of PAF in general elderly population.