Assessment of Left Atrial Volume by Magnetic Resonance in Patients with Permanent Atrial Fibrillation. The Short-axis Method vs. the Single Plane Area-length Method

ABSTRACT

Background:

Atrial fibrillation (AF) is associated with enlargement of the left atrium (LA). The LA volume can be assessed by cardiac magnetic resonance (CMR). The standard CMR method for measuring the LA volume is the shortaxis (SA) method, which is time consuming, hence little useful in the clinical setting. For this reason more simplified methods have been developed to assess the LA volume.

Objective:

To compare the standard SA method and the simplified single plane area-length (AL) method for measurements of the LA volume in patients with permanent AF.

Methods and Results:

CMR was performed in 34 patients with permanent AF. CMR was conducted with the steady-state free precession (SSFP) technique TrueFISP. LA volumes were measured using the single plane AL method and the SA method. A good and statistically significant correlation was found between the two methods. The Pearson's correlation coefficients for LA maximal volume (LAmax) and LA minimal volume (LAmin) were 0.92, p<0.0001 and 0.91, p<0.0001, respectively. The single plane AL method underestimated LA volumes compared to the SA method (LAmax: 143 ± 35 ml vs. 149 ml ± 38, p=0.046, LAmin: 124 ml ± 30 vs. 130 ml ± 34, p=0.014). Intra- and interobserver agreement was inferior for the single plane AL method.

Conclusion:

Measurements of LA volumes by the SA method and the single plane AL methods correlate closely in patients with permanent AF. However, the single plane AL method underestimates the LA volume and the reproducibility is inferior compared to the SA method.

Keywords:

Atrial fibrillation, cardiac magnetic resonance, left atrial volume, steady-state free precession, short-axis method, area-length method.