Cine-CMR quantified left atrial diameter - a simple index of left atrial remodeling that closely parallels chamber area and stratifies longitudinal atrial arrhythmic risk
Journal of Cardiovascular Magnetic Resonance volume 16, Article number: P225 (2014)
Cine cardiac magnetic resonance (cine-CMR) provides excellent endocardial delineation, enabling accurate quantification of left atrial (LA) chamber size. Relative utility of cine-CMR linear dimensions and area-based indices for prediction of LA-associated arrhythmias is unknown.
The study comprised patients with coronary artery disease (CAD) included in a multimodality registry. Cine-CMR (1.5T) was performed using a standard 2-dimensional steady state free precession (SSFP) pulse sequence (typical TR 3.5 msec, TE 1.6 msec, flip angle 60°, temporal resolution 30-50 msec). Cine-CMR evidenced mitral regurgitation (MR) severity was graded in accordance with established conventions based on size of MR associated inter-voxel dephasing of the regurgitant jet. LA size was measured on cine-CMR at atrial end-diastole using two established methods:  linear diameter (measured in 3-chamber long axis orientation),  area (planimetered in 4-chamber long axis orientation), with both indices indexed to body surface area. Clinical follow-up was performed via medical record review, with atrial fibrillation (AF) or flutter (AFl) verified based on physician documentation.
336 patients with CAD were studied (60 ± 12 yo, 79% M, 34% DM, 58% HTN); LA diameter (mean 2 ± 0.4 cm/m2) and area (12 ± 3 cm2/m2) yielded similar prevalence of chamber dilation (20% vs. 21%, p = 0.76) assigned using established cine-CMR population-based cutoffs. LA indices correlated highly (r = 0.74, p < 0.001;Figure 1), with similar magnitude of correlation among subgroups at risk for LA remodeling, such as patients with HTN (r = 0.74, p < 0.001) and DM (r = 0.77, p < 0.001). Severe MR was 9-fold more common among patients in the top quartile of LA diameter compared to the remainder of the population (19% vs. 2%, p < 0.001), with similar results when prevalence of severe MR was compared among patients stratified by LA area (17% vs. 3%, p < 0.001). Clinical follow-up (minimum 60 days) was available in 46% of the study population (n = 168). During mean follow-up of 1.5 ± 1.9 years, 31 patients (18%) developed AF/AFl: Cine-CMR quantified LA dimensions stratified arrhythmic risk, with a 5-fold increase in relative risk for AF/Fl among patients in the highest LA diameter quartile (HR 5.1, CI 1.5 - 17.1, p < 0.05), and a 3-fold increase for those in the highest quartile of LA area (HR 3.4, CI 1.1 to 10.6, p < 0.05) compared to the remainder of the population (Figure 2).
Cine-CMR quantified LA diameter provides a simple measure of atrial remodeling that correlates well with LA area, yielding similar predictive value for stratifying MR as well as longitudinal risk for atrial arrhythmias.
National Institutes of Health (K23 HL102249-01).
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Kim, J., Gurevich, S., Kochav, J.D. et al. Cine-CMR quantified left atrial diameter - a simple index of left atrial remodeling that closely parallels chamber area and stratifies longitudinal atrial arrhythmic risk. J Cardiovasc Magn Reson 16 (Suppl 1), P225 (2014). https://doi.org/10.1186/1532-429X-16-S1-P225