Association of left atrial function and left atrial enhancement in patients with atrial fibrillation: cardiac magnetic resonance study

Abstract

Background: Atrial fibrillation (AF) is associated with left atrial (LA) structural and functional changes. Cardiac magnetic resonance late gadolinium enhancement (LGE) and feature-tracking are capable of noninvasive quantification of LA fibrosis and myocardial motion, respectively. We sought to examine the association of phasic LA function with LA enhancement in patients with AF.

Methods and results: LA structure and function was measured in 90 patients with AF (age 61±10 years; 76% men) referred for ablation and 14 healthy volunteers. Peak global longitudinal LA strain, LA systolic strain rate, and early and late diastolic strain rates were measured using cine-cardiac magnetic resonance images acquired during sinus rhythm. The degree of LGE was quantified. Compared with patients with paroxysmal AF (60% of cohort), those with persistent AF had larger maximum LA volume index (56±17 versus 49±13 mL/m(2); P=0.036), and increased LGE (27.1±11.7% versus 36.8±14.8%; P<0.001). Aside from LA active emptying fraction, all LA parameters (passive emptying fraction, peak global longitudinal LA strain, systolic strain rate, early diastolic strain rate, and late diastolic strain rate) were lower in patients with persistent AF (P<0.05 for all). Healthy volunteers had less LGE and higher LA functional parameters compared with patients with AF (P<0.05 for all). In multivariable analysis, increased LGE was associated with lower LA passive emptying fraction, peak global longitudinal LA strain, systolic strain rate, early diastolic strain rate, and late diastolic strain rate (P<0.05 for all).

Conclusions: Increased LA enhancement is associated with decreased LA reservoir, conduit, and booster pump functions. Phasic measurement of LA function using feature-tracking cardiac magnetic resonance may add important information about the physiological importance of LA fibrosis.

Keywords: atrial fibrillation; atrial function, left; gadolinium; magnetic resonance imaging.

Figure 1. Assessment of LA structure using LGE-MRI

Figure 2. LA volume and function during the cardiac cycle

A: Changes in LA volume during reservoir, conduit and booster pump phases. The volume curve is a composite of measured volumes using 2 and 4 chamber views. B: LA longitudinal strain in different segments of LA, the dotted white line shows the average of LA longitudinal strain in all segments. PLAS: peak global longitudinal LA strain; C: LA longitudinal strain rate in different LA segments. The white dotted line shows the average of the strain rate in all segments. The points for systolic strain rate (SR-s), early diastolic strain rate (SR-ed) and late diastolic strain rate (SR-ld) have been shown.

Figure 3

Correlation of LA enhancement and A: maximum LA volume index, B: minimum LA volume index, C: LA passive emptying fraction, D: LA active emptying fraction, E: LA peak global longitudinal strain, F: systolic LA strain rate, G: early diastolic atrial strain rate (absolute value), and H: late diastolic LA strain rate (absolute values)

Figure 4

Left: Examples of image intensity ratio map of two LA with mild (top) and extensive (bottom) enhancement. Right: Comparing LA function in two patients with mild (solid black line) and extensive (dotted gray line) LA enhancement A: changes in LA volume during systole (reservoir), early diastole (conduit), and late diastole (pump). B: changes in global longitudinal LA strain during cardiac cycle. More extensive LA enhancement was associated with smaller peak global longitudinal atrial strain (PLAS). C: LA longitudinal strain rate during cardiac cycle. In this example the patient with more extensive LA enhancement has smaller systolic strain rate (SR-s), early diastolic strain rate (SR-ed), and late diastolic strain rate (SR-ld)