Reproducibility of left atrial function using cardiac magnetic resonance imaging

Abstract

Objectives: To determine the test-retest reproducibility and observer variability of CMR-derived LA function, using (i) LA strain (LAS) and strain rate (LASR), and (ii) LA volumes (LAV) and emptying fraction (LAEF).

Methods: Sixty participants with and without cardiovascular disease (aortic stenosis (AS) (n = 16), type 2 diabetes (T2D) (n = 28), end-stage renal disease on haemodialysis (n = 10) and healthy volunteers (n = 6)) underwent two separate CMR scans 7-14 days apart. LAS and LASR, corresponding to LA reservoir, conduit and contractile booster-pump function, were assessed using Feature Tracking software (QStrain v2.0). LAEF was calculated using the biplane area length method (QMass v8.1). Both were assessed using 4- and 2-chamber long-axis standard steady-state free precession cine images, and average values were calculated. Intra- and inter-observer variabilities were assessed in 10 randomly selected participants.

Results: The test-retest reproducibility was moderate to poor for all strain and strain rate parameters. Overall, strain and strain rate corresponding to reservoir phase (LAS_r, LASR_r) were the most reproducible, yielding the smallest coefficient of variance (CoV) (29.9% for LAS_r, 28.9% for LASR_r). The test-retest reproducibility for LAVs and LAEF was good: LAVmax CoV = 19.6% ICC = 0.89, LAVmin CoV = 27.0% ICC = 0.89 and total LAEF CoV = 15.6% ICC = 0.78. The inter- and intra-observer variabilities were good for all parameters except for conduit function.

Conclusion: The test-retest reproducibility of LA strain and strain rate assessment by CMR utilising Feature Tracking is moderate to poor across disease states, whereas LA volume and emptying fraction are more reproducible on CMR. Further improvements in LA strain quantification are needed before widespread clinical application.

Key points: • LA strain and strain rate assessment using Feature Tracking on CMR has moderate to poor test-retest reproducibility across disease states. • The test-retest reproducibility for the biplane method of assessing LA function is better than strain assessment, with lower coefficient of variances and narrower limits of agreement on Bland-Altman plots. • Biplane LA volumetric measurement also has better intra- and inter-observer variability compared to strain assessment.

Keywords: Cardiovascular diseases; Left atrial function; Magnetic resonance imaging; Reproducibility of results.

Fig. 1

Left atrial volume quantification for emptying fraction calculation. Cine 2- and 4-chamber images illustrating contoured maximum (at left ventricular systole) and minimum (at left ventricular diastole) left atrial areas for calculating LA volume and emptying fraction using biplane area length method

Fig. 2

An example of left atrial strain and strain rate assessment using Feature Tracking. a A typical LA strain curve (upper) and a typical strain rate curve (lower), anterior wall (green), inferior wall (blue), LA roof (white) and the average (purple dotted line). b 4-Chamber and 2-chamber images illustrate LA contours at ventricular end-systole and end-diastole (LAS_r, LA strain at reservoir; LAS_cd, LA strain at conduit; LAS_bp, LA strain at booster-pump phase; LASR_r, LA strain rate at reservoir; LASR_cd, LA strain rate at conduit; LASR_bp, LA strain rate at booster-pump phase)

Fig. 3

Bland-Altman plots for test-retest reproducibility of left atrial strain (left panel) and volume (right panel) parameters (LAS_r, LA strain at reservoir; LAS_cd, LA strain at conduit; LAS_bp, LA strain at booster-pump phase; LAV, left atrial volume; LAEF, left atrial emptying fraction)

Fig. 4

Associations of left atrial emptying fractions with left atrial strain parameters. Scatter plots showing the correlation between total LA emptying fraction (EF) and LA strain at reservoir phase (a), passive LAEF and LA strain at conduit phase (b), active LAEF and LA strain at contraction booster-pump phase (c) (LAS_r, LA strain at reservoir; LAS_cd, LA strain at conduit; LAS_bp, LA strain at booster-pump phase; LAEF, left atrial emptying fraction)