Reproducibility of left atrial function using cardiac magnetic resonance imaging.

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.

Emerging Techniques for Risk Stratification in Nonischemic Dilated Cardiomyopathy: JACC Review Topic of the Week.

Dilated cardiomyopathy (DCM) is a common condition, which carries significant mortality from sudden cardiac death and pump failure. Left ventricular ejection fraction has conventionally been used as a risk marker for sudden cardiac death, but has performed poorly in trials. There have been significant advances in the areas of cardiac magnetic resonance imaging and genetics, which are able to provide useful rick prediction in DCM. Biomarkers and cardiopulmonary exercise testing are well validated in the prediction of risk in heart failure; however, they have been tested less specifically in the DCM setting. This review will discuss these methods with a view toward multiparametric risk assessment in DCM with the hope of creating parametric risk models to predict sudden cardiac death and pump failure in the DCM population.

Non-ST elevation myocardial infarction, non-obstructive coronary arteries and severe regional microvascular dysfunction in a patient with dilated cardiomyopathy.

Cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement (LGE) is a key modality in providing localisation and characterisation of myocardial injury in patients diagnosed with myocardial infarction with non-obstructive coronary arteries (MINOCA). We present a case that demonstrates the unique ability of CMR to provide crucial information in instances of uncertainty. A 71-year-old patient with dilated cardiomyopathy (DCM) presented with symptoms suggestive of acute myocardial infarction. The diagnosis of MINOCA was confirmed following coronary angiography. CMR imaging with LGE confirmed presence of apical infarction. Quantitative myocardial perfusion mapping demonstrated severely reduced blood flow in the non-infarcted septal segments proximal to the distal infarcted territory. The precise aetiology of apical infarction remains uncertain and is likely attributed to coronary plaque rupture. However, concomitant severe regional microvascular dysfunction is also appreciated. This is a recognised, but not well described, phenomenon in DCM and may contribute to repetitive ischaemic injury and disease progression.