Identification of the optimal method for measuring left atrium volume as a marker of undetected atrial fibrillation in patients with cryptogenic stroke and high prevalence of overweight
Authors: Cecconi A , Viliani D , Montes A , Lopez Melgar B , Ramos Lopez A , Santos Martin B , De Toffol G , Vilches Miguel L , Vazquez Lopez-Ibor J , Diego Nieto G , Benedicto Buendia A , Dominguez Arganda L , Alfonso F , Jimenez Borreguero L J 
Published: October 2024

Abstract

Introduction
Paroxysmal atrial fibrillation (AF) is detected in approximately one-third of patients diagnosed with cryptogenic stroke undergoing prolonged ECG monitoring. Several risk factors for AF have been described, including left atrium (LA) enlargement, LA deformation, age, cardiovascular risk factors, and biomarkers as N-pro-BNP and troponin. Specifically, LA enlargement is a direct marker of atrial cardiopathy, which predisposes to AF. However, the methods to calculate LA enlargement vary. While LA biplane volume indexed to body surface area (BSA) remains the standardized method of choice according to current guidelines, it may underestimate the degree of enlargement in overweight patients. Additionally, overweight produces a systemic inflammatory state which is also associated with AF.

Purpose
The primary objective of the study was to define the best parameter among LA end systolic volume (LAESV), LAESV indexed to BSA (LAESV/BSA), and LAESV indexed to ideal BSA for identifying patients admitted for cryptogenic stroke with undetected paroxysmal AF. The secondary objective was to assess the accuracy of these parameters in both normal-weight and overweight patients.

Methods
Consecutive patients over 65 years-old diagnosed with cryptogenic stroke in our tertiary hospital were enrolled. All patients underwent 15-days ambulatory ECG monitoring to screen for undetected paroxysmal AF. Clinical, echocardiographic and laboratory data were prospectively collected. Ideal BSA was calculated using the Devine method. The accuracy of LA volume parameters in classifying patients with undetected paroxysmal AF was assessed using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve. The analysis was stratified for overweight status (BMI &lt; 25 or BMI ≥ 25).

Results
A total of 66 patients (Mean age 78.4 ± 7.6 years; 48% male) were included. Of them, 39 (59%) had hypertension, 16 (24%) had diabetes and 39 (59%) were overweight. AF was present in 21 (32%) patients. The mean LAESV, LAESV/BSA, LAESV/ideal BSA were 56.2 ± 23.0 ml, 34.2 ± 12.6 ml/m2, and 34.7 ± 14.1 ml/m2, respectively. Figure 1 illustrates the ROC curves for LA volume parameters in the main cohort and stratified by overweight status. Overall, no relevant differences in AUC were observed among LAESV, LAESV/BSA, LAESV/ideal BSA in each scenario. However, BMI significantly altered the discrimination performance of LA volume measures, which resulted optimal in normal-weight patients (AUC from 0.838 to 0.886) and absent in overweight patients (AUC from 0.838 to 0.521 to 0.564).

Conclusions
LAESV, LAESV/BSA, LAESV/ideal BSA show similar discrimination performance in identifying undetected AF in patients with cryptogenic stroke. However, the presence of overweight considerably impacts on the predictive value of LA volume parameters in this clinical scenario.ROC curves