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

Association of left atrial structure and function and incident cardiovascular disease in patients with diabetes mellitus: results from multi-ethnic study of atherosclerosis (MESA)

AIMS

Diabetes mellitus (DM) is associated with the development of cardiovascular disease (CVD). Morphological changes in the left atrium (LA) may appear before symptoms. We aimed to investigate the association between cardiac magnetic resonance imaging (CMR) measured LA structure and function and incident CVD in asymptomatic individuals with DM.

METHODS AND RESULTS

Tissue tracking CMR was used to measure LA size and phasic function (emptying fractions and strain) on all 536 Multi-Ethnic Study of Atherosclerosis (MESA) participants with DM and available CMR at baseline in 2000-2002. At the time of enrolment, all participants were free of clinically recognized CVD, which was defined as MI, resuscitated cardiac arrest, angina, stroke, heart failure, and atrial fibrillation. Cox regression was used to assess the association of LA parameters with incident CVD adjusted for traditional cardiovascular risk factors, LV mass, NT Pro-BNP and maximum LA volume. Kaplan-Meier curves, adjusted for traditional risk factors, were generated for each LA measurement for the 25% of participants with the most abnormal values versus the remaining 75%. After a mean follow up of 11.4 ± 3.4 years, 141 individuals developed CVD. Individuals with incident CVD (mean age 66 years, 66% male vs. mean age 64 years, 50% male) had larger maximum and minimum LA volume index (LAVI) (32.1 vs. 26.8 mm3/m2; 19.4 vs. 14.2 mm3/m2 respectively, P < 0.001 for both), and lower total, passive, and active EF than those without CVD (P < 0.01 for all). In the fully adjusted model, there was a significant association of minimum LAVI, LA total EF, LA passive EF and LA active EF with incident CVD (HR 1.12 per mm3/m2, P < 0.001; HR 0.95 per %, P < 0.001; HR 0.97 per %, P = 0.021; HR 0.98 per %, P < 0.027, respectively).

CONCLUSIONS

CMR measured LA minimum volume and LA function as measured by emptying fraction are predictive of CVD in a diabetic multi-ethnic population free of any clinically recognized CVD at baseline.

Echocardiographic associates of atrial fibrillation in end-stage renal disease

Background

The prevalence of atrial fibrillation (AF) in end-stage renal disease (ESRD) patients is relatively high. The present study evaluated the association between left atrial (LA) remodelling, including an increased size and myocardial fibrosis, and slow LA conduction and the occurrence of AF.

Methods

In 171 ESRD patients enrolled in the Implantable Cardioverter Defibrillators in Dialysis patients (ICD2) trial, the LA dimensions, LA conduction delay [as reflected by the time difference between P-wave onset on surface electrocardiogram and A'-wave on tissue Doppler imaging (PA-TDI)] and LA function were compared between patients who exhibited AF versus patients without AF. Based on ICD remote monitoring or clinical records, the occurrence of AF was detected.

Results

Of 171 patients, 47 (27%) patients experienced AF. Despite comparable left ventricular ejection fraction and prevalence of significant mitral regurgitation, patients with AF had significantly larger LA volume index (mean ± standard deviation) (29 ± 11 versus 23 ± 10 mL/m2, P = 0.001), longer PA-TDI duration (144 ± 30 versus 131 ± 27 ms, P = 0.010) and reduced late diastolic mitral annular velocity (A') (7.1 ± 2.8 versus 8.2 ± 2.4 cm/s, P = 0.012) compared with patients without AF. On multivariable analysis, larger LA volume index [odds ratio (OR) 1.04, 95% confidence interval (CI) 1.01-1.08, P = 0.017], longer PA-TDI duration (OR 1.02, 95% CI 1.00-1.03, P = 0.025) and reduced A' (OR 0.84, 95% CI 0.72-0.98, P = 0.025) were independently associated with AF after adjusting for age and left ventricle diastolic relaxation.

Conclusion

ESRD patients with AF show more advanced changes in the LA substrate than ESRD patients without AF.

Impaired left atrial function predicts inappropriate shocks in primary prevention implantable cardioverter-defibrillator candidates

INTRODUCTION

Inappropriate implantable cardioverter-defibrillator (ICD) shocks, commonly caused by atrial fibrillation (AF), are associated with an increased mortality. Because impaired left atrial (LA) function predicts development of AF, we hypothesized that impaired LA function predicts inappropriate shocks beyond a history of AF.

METHODS AND RESULTS

We prospectively analyzed the association between LA function and incident inappropriate shocks in primary prevention ICD candidates. In the Prospective Observational Study of ICD (PROSE-ICD), we assessed LA function using tissue-tracking cardiac magnetic resonance (CMR) prior to ICD implantation. A total of 162 patients (113 males, age 56 ± 15 years) were included. During the mean follow-up of 4.0 ± 2.9 years, 26 patients (16%) experienced inappropriate shocks due to AF (n = 19; 73%), supraventricular tachycardia (n = 5; 19%), and abnormal sensing (n = 2; 8%). In univariable analyses, inappropriate shocks were associated with AF history prior to ICD implantation, age below 70 years, QRS duration less than 120 milliseconds, larger LA minimum volume, lower LA stroke volume, lower LA emptying fraction, impaired LA maximum and preatrial contraction strains (Smax and SpreA ), and impaired LA strain rate during left ventricular systole and atrial contraction (SRs and SRa ). In multivariable analysis, impaired Smax (hazard ratio [HR]: 0.96, P = 0.044), SpreA (HR: 0.94, P = 0.030), and SRa (HR: 0.25, P < 0.001) were independently associated with inappropriate shocks. The receiver-operating characteristics curve showed that SRa improved the predictive value beyond the patient demographics including AF history (P = 0.033).

CONCLUSION

Impaired LA function assessed by tissue-tracking CMR is an independent predictor of inappropriate shocks in primary prevention ICD candidates beyond AF history.

Quantifying left atrial structure and function using single-plane tissue-tracking cardiac magnetic resonance

PURPOSE

Left atrial (LA) structure and function are important markers of adverse cardiovascular outcomes. Tissue-tracking cardiovascular magnetic resonance (CMR) accurately quantifies LA volume, strain, and strain rate based on biplane long-axis imaging. We aimed to assess the accuracy of the LA indices quantification from single-plane tissue-tracking CMR.

METHODS

We included 388 subjects (mean age 57±13, male 70%) whose cine CMR images in sinus rhythm were available in both four-chamber and two-chamber views: 162 patients from the Prospective Observational Study of Implantable Cardioverter-Defibrillators (PROSE-ICD) Study, 208 patients from atrial fibrillation cohort, and 18 healthy volunteers. The group was divided into the training set (n=291) and the test set (n=97). In the training set, we compared the LA indices derived from biplane imaging and single-plane imaging (a four-chamber view), and developed regression equations. In the test set, we used the regression equations to estimate the LA indices from the single-plane imaging, and quantified the accuracy of the estimation against the LA indices from the biplane.

RESULTS

In the training set, all the LA indices from the single-plane imaging tended to be systematically underestimated compared with those from the biplane imaging, however, the correlation coefficient was high (r²=0.73-0.90, p<0.001). In the test set, LA volumetric indices showed excellent reproducibility (intra-class correlation coefficient (ICC): 0.91-0.92) with relatively low variability (16.3-22.3%); For LA strain and strain rate indices, reproducibility was excellent (ICC: 0.81-0.93), however, the variability was slightly higher than that of volumetric indices (21.7-25.4%).

CONCLUSIONS

LA volumetric indices measured from single-plane tissue-tracking CMR are highly accurate and reproducible with reference to those derived from the standard biplane imaging. The reproducibility of LA strain and strain rate indices from single-plane tissue-tracking CMR is excellent but the variability is higher than that of the volumetric indices.

Left Atrial Size and Function in Hypertrophic Cardiomyopathy Patients and Risk of New-Onset Atrial Fibrillation

BACKGROUND

The value of left atrial (LA) diameter, volume, and strain to risk stratify hypertrophic cardiomyopathy patients for new-onset atrial fibrillation (AF) was explored.

METHODS AND RESULTS

A total of 242 hypertrophic cardiomyopathy patients without AF history were evaluated by (speckle-tracking) echocardiography. During mean follow-up of 4.8±3.7 years, 41 patients (17%) developed new-onset AF. Multivariable analysis showed LA volume (≥37 mL/m²; hazard ratio, 2.68; 95% confidence interval, 1.30-5.54; P=0.008) and LA strain (≤23.4%; hazard ratio, 3.22; 95% confidence interval, 1.50-6.88; P=0.003), but not LA diameter (≥45 mm; hazard ratio, 1.67; 95% confidence interval, 0.84-3.32; P=0.145), as independent AF correlates. Importantly, 59% (n=24) of AF events occurred despite a baseline LA diameter <45 mm, observed in 185 patients. In this patient subset, LA strain (area under the curve 0.73) and LA volume (area under the curve 0.83) showed good predictive value for new-onset AF. Furthermore, patients with LA volume <37 versus ≥37 mL/m² and LA strain >23.4% versus ≤23.4% had superior 5-year AF-free survival of 93% versus 80% (P=0.003) and 98% versus 74% (P=0.002), respectively. Importantly, LA volume <37 mL/m² and strain >23.4% yielded high negative predictive value (93% and 98%, respectively) for new-onset AF. Likelihood ratio test indicated incremental value of LA volume assessment (P=0.011) on top of LA diameter to predict new-onset AF in hypertrophic cardiomyopathy patients with LA diameter <45 mm, which tended to increase further by addition of LA strain (P=0.126).

CONCLUSIONS

LA diameter, volume, and strain all relate to new-onset AF in hypertrophic cardiomyopathy patients. In patients with normal LA size, however, both LA volume and strain further refine risk stratification for new-onset AF.

MRI-Derived Myocardial Strain Measures in Normal Subjects

OBJECTIVES

The aim of this study was to perform a systematic review and meta-analysis to estimate the normal ranges of magnetic resonance imaging (MRI)-based feature tracking (FT) and to identify sources of variations. Similar analyses were also performed for strain encoding, displacement encoding with stimulated echoes, and myocardial tagging.

BACKGROUND

MRI-FT is a novel technique for quantification of myocardial deformation using MRI cine images. However, the reported 95% confidence intervals (CIs) from the 2 largest studies have no overlaps.

METHODS

Four databases (EMBASE, SCOPUS, PUBMED, and Web of Science) were systematically searched for MRI strains of the left (LV) and right (RV) ventricles. The key terms for MRI-FT were "tissue tracking," "feature tracking," "cardiac magnetic resonance," "cardiac MRI," "CMR," and "strain." A random effects model was used to pool LV global longitudinal strain (GLS), global circumferential strain (GCS), global radial strain (GRS), and RVGLS. Meta-regressions were used to identify the sources of variations.

RESULTS

659 healthy subjects were included from 18 papers for MRI-FT. Pooled mean of LVGLS was -20.1% (95% CI: -20.9% to -19.3%), LVGCS -23% (95% CI: -24.3% to -21.7%), LVGRS 34.1% (95% CI: 28.5% to 39.7%), and RVGLS -21.8% (95% CI: -23.3% to -20.2%). Although there were no publication biases except for LVGCS, significant heterogeneities were found. Meta-regression showed that variation of LVGCS was associated with field strength (β = 3.2; p = 0.041). Variations of LVGLS, LVGRS, and RVGLS were not associated with any of age, sex, software, field strength, sequence, LV ejection fraction, or LV size. LVGCS seems the most robust in MRI-FT. Among the MRI-derived strain techniques, the normal ranges were mostly concordant in LVGLS and LVGCS but varied substantially in LVGRS and RVGLS.

CONCLUSIONS

The pooled means of 4 MRI-derived myocardial strain methods in normal subjects are demonstrated. Differences in field strength were attributed to variations of LVGCS.

Cardiac Magnetic Resonance-Measured Left Atrial Volume and Function and Incident Atrial Fibrillation: Results From MESA (Multi-Ethnic Study of Atherosclerosis)

BACKGROUND

Early detection of structural changes in left atrium (LA) before atrial fibrillation (AF) development could be helpful in identification of those at higher risk for AF. Using cardiac magnetic resonance imaging, we examined the association of LA volume and function, and incident AF in a multiethnic population free of clinical cardiovascular diseases.

METHODS AND RESULTS

In a case-cohort study embedded in MESA (Multi-Ethnic Study of Atherosclerosis), baseline LA size and function assessed by cardiac magnetic resonance feature-tracking were compared between 197 participants with incident AF and 322 participants randomly selected from the whole MESA cohort. Participants were followed up for 8 years. Incident AF cases had a larger LA volume and decreased passive, active, and total LA emptying fractions and peak global LA longitudinal strain (peak LA strain) at baseline. In multivariable analysis, elevated LA maximum volume index (hazard ratio, 1.38 per SD; 95% confidence interval, 1.01-1.89) and decreased peak LA strain (hazard ratio, 0.68 per SD; 95% confidence interval, 0.48-0.96), and passive and total LA emptying fractions (hazard ratio for passive LA emptying fractions, 0.55 per SD; 95% confidence interval, 0.40-0.75 and hazard ratio for active LA emptying fractions, 0.70 per SD; 95% confidence interval, 0.52-0.95), but not active LA emptying fraction, were associated with incident AF.

CONCLUSIONS

Elevated LA volumes and decreased passive and total LA emptying fractions were independently associated with incident AF in an asymptomatic multiethnic population. Including LA functional variables along with other risk factors of AF may help to better risk stratify individuals at risk of AF development.

Advances in anticoagulation management of patients undergoing cardioversion of nonvalvular atrial fibrillation

Atrial fibrillation (AF) is a major cause of stroke. The restoration of sinus rhythm through cardioversion, either chemical or electrical is a common practice. Interestingly, there is an incremental increase from the baseline risk for embolisation in the immediate post-cardioversion period, with most events occurring within 10 days from cardioversion. Especially patients with recent onset AF show the lowest rates of antithrombotic therapy, while having a high stroke risk. Despite the increased risk for embolisation, anticoagulation in patients undergoing cardioversion of atrial fibrillation is often inadequate. Moreover, since the implementation of non-vitamin K antagonists oral anticoagulants (DOACs) there are several therapeutic approaches for pericardioversion anticoagulant therapy and not all suits to all patients. In addition, the extensive use of transesophageal echocardiography provides an alternative strategy, especially useful for patients of high haemorrhagic risk. In this review article, we aim to provide an update on the anticoagulation strategies for patients undergoing cardioversion of non-valvular atrial fibrillation in the advent of the use of DOACs.

Usefulness of the Atrial Emptying Fraction to Predict Maintenance of Sinus Rhythm After Direct Current Cardioversion for Atrial Fibrillation

Atrial volumes indexed to body surface area (AVI) are robust predictors of nonvalvular atrial fibrillation (AF) recurrence after direct current cardioversion (DCCV). The incremental value of atrial emptying fraction (EmF) compared with atrial volumes as a predictor for recurrent AF after DCCV has not been evaluated. We sought to compare the predictive ability of baseline left atrial (LA) EmF, right atrial (RA) EmF, LAVI, and RAVI for post-DCCV AF recurrence at 6 months. The first 95 patients enrolled in the AF Clinic Registry with adequate echocardiogram imaging constituted the study cohort. Each patient underwent echocardiogram within 6 months before cardioversion. Maximal LAVI and RAVI, LA EmF, and RA EmF were performed offline using 4-chamber single-plane Simpson's method, averaged over 5 cycles. The mean age of the study cohort was 64 ± 12 years, and 67% were men. Only 28 patients (29%) who underwent DCCV remained in sinus rhythm at 6 months of follow-up. The remaining, 67 (71%) had reverted to AF or underwent ablation during the 6 months of follow-up. The overall performance for prediction of AF recurrence was greatest for RA EmF, area under the receiver operator characteristic curve (AUC): RA EmF 0.92, LA EmF 0.89, RAVI 0.76, and LAVI 0.63. RA and LA EmF AUCs were significantly higher than for LAVI or RAVI (max p = 0.02). In conclusion, although RAVI and LAVI are strong predictors of AF recurrence after DCCV, RA and LA EmF outperformed in this cohort.

The Mechanism of and Preventive Therapy for Stroke in Patients with Atrial Fibrillation

Atrial fibrillation is a major cardiac cause of stroke, and a pathogenesis involving thrombus formation in patients with atrial fibrillation is well established. A strategy for rhythm control that involves catheter ablation and anticoagulation therapy is evolving. A strategy for rhythm control that restores and maintains sinus rhythm should reduce the risk of ischemic stroke that is associated with atrial fibrillation; however, this is yet to be proven in large-scale randomized controlled trials. This paper reviews the emerging role of rhythm control therapy for atrial fibrillation to prevent stroke.

Incremental Value of Left Atrial Global Longitudinal Strain for Prediction of Post Stroke Atrial Fibrillation in Patients with Acute Ischemic Stroke

Background

Atrial fibrillation (AF) is a well-established risk factor for stroke. Interestingly, ischemic stroke increases risk of incident AF in patients without prior diagnosed AF. For better risk stratification for post-stroke AF, we studied left atrial (LA) size and mechanical function using two-dimensional (2D) speckle tracking imaging in patients with acute ischemic stroke.

Methods

A total of 227 patients (132 males, age 67 ± 12) with acute ischemic stroke without a history of AF underwent 2D transthoracic echocardiography and speckle tracking imaging for the assessment of LA volume index and global LA longitudinal strain (LALS). From clinical variables, the CHA₂DS₂-VASc score and National Institute of Health Stroke Scale (NIHSS) were calculated in each patient. Post-stroke AF was defined as newly diagnosed AF during the course after ischemic stroke.

Results

Post-stroke AF occurred in 25 patients (11%). Patients with post-stroke AF were older and showed a higher tendency of CHA₂DS₂-VASc score, significantly higher log NIHSS, larger LA volume index and lower global LALS than those without. In multivariate analysis, global LALS was an independent predictor for post-stroke AF (hazard ratio 0.90, 95% confidence interval 0.83.0.97, p < 0.01) after controlling for confounding factors. Furthermore, global LALS provided incremental predictive value for post-stroke AF over the CHA₂DS₂-VASc score, NIHSS, and LA volume index. The global LALS < 14.5% better distinguished post-stroke AF (area under the curve 0.837, sensitivity 60%, specificity 95%, p < 0.01) than CHA₂DS₂-VASc score.

Conclusion

Global LALS as a marker of LA mechanical function has incremental predictive value for post-stroke AF in patients with acute ischemic stroke.

Cardiac Fibrosis in Patients With Atrial Fibrillation: Mechanisms and Clinical Implications

Atrial fibrillation (AF) is associated with structural, electrical, and contractile remodeling of the atria. Development and progression of atrial fibrosis is the hallmark of structural remodeling in AF and is considered the substrate for AF perpetuation. In contrast, experimental and clinical data on the effect of ventricular fibrotic processes in the pathogenesis of AF and its complications are controversial. Ventricular fibrosis seems to contribute to abnormalities in cardiac relaxation and contractility and to the development of heart failure, a common finding in AF. Given that AF and heart failure frequently coexist and that both conditions affect patient prognosis, a better understanding of the mutual effect of fibrosis in AF and heart failure is of particular interest. In this review paper, we provide an overview of the general mechanisms of cardiac fibrosis in AF, differences between fibrotic processes in atria and ventricles, and the clinical and prognostic significance of cardiac fibrosis in AF.

Association of left atrial function with incident atypical atrial flutter after atrial fibrillation ablation

BACKGROUND

Symptomatic left atrial (LA) flutter (LAFL) is common after atrial fibrillation (AF) ablation.

OBJECTIVE

The purpose of this study was to examine the association of baseline LA function with incident LAFL after AF ablation.

METHODS

The source cohort included 216 patients with cardiac magnetic resonance (CMR) before initial AF ablation between 2010 and 2013. Patients who underwent cryoballoon or laser ablation, patients with AF during CMR, and those with suboptimal CMR, or missing follow-up data were excluded. Baseline LA volume and function were assessed by feature-tracking CMR analysis.

RESULTS

The final cohort included 119 patients (mean age 58.9 ± 11 years; 76.5% men; 70.6% patients with paroxysmal AF). During a median follow-up of 421 days (interquartile range 235-751 days), 22 patients (18.5%) had incident LAFL. Baseline LA volume was similar between the 2 groups. In contrast, baseline reservoir, conduit, and contractile function of the LA were significantly impaired in patients with incident LAFL. Baseline global peak longitudinal atrial strain (PLAS) <22.65% predicted incident LAFL with 86% sensitivity and 68% specificity (C statistic 0.76). In a multivariable model adjusting for age, heart failure, and LA volume, PLAS (hazard ratio 0.9 per % increase in PLAS; P = .003) and LA linear lesions (hazard ratio 2.94; P = .020) were independently associated with incident LAFL. The coexistence of PLAS <22.65% and linear lesions was associated with 9-fold increased hazard of incident LAFL.

CONCLUSION

Baseline LA function and linear lesions were independently associated with incident LAFL after AF ablation. Linear lesions should be limited to selected cases, especially in patients with impaired LA function.

Regional function analysis of left atrial appendage using motion estimation CT and risk of stroke in patients with atrial fibrillation

AIMS

The aim of this article is to determine the association between left atrial appendage (LAA) regional dysfunction using image-based motion-estimation computed tomography (CT) (iME) and a prior history of stroke or transient ischaemic attack (TIA) in patients with atrial fibrillation (AF).

METHODS AND RESULTS

In this single-centre retrospective case-control study, among patients referred for AF ablation who underwent pre-ablation cardiac CT with retrospective ECG gating, we identified 18 patients with a prior history of stroke or TIA at the time of CT scan and 18 age- and gender-matched controls. All the patients were in sinus rhythm at the time of CT scan. Four-dimensional motion vector field was estimated from the CT images using iME. To assess myocardial deformation, area change ratio (A) and area change rate (AR) were calculated over the endocardial surface of the LAA. There was no significant difference in the baseline patient characteristics between the stroke/TIA group and the control group (67.6 ± 8.1 years old, 66.7% male, 16.7% persistent AF). LAA maximum (Amax; 23.8 ± 33.0 vs. 52.9 ± 41.2%, P = 0.02) and pre-atrial contraction area change ratio (ApreA; 13.7 ± 17.7 vs. 30.9 ± 29.2%, P = 0.04) were significantly lower in the stroke/TIA group than in the control group, respectively. The difference in LAA Amax and ApreA remained significant in multivariate analysis (P = 0.03 and P = 0.04, respectively).

CONCLUSION

LAA regional dysfunction is associated with stroke/TIA in AF patients. Our results offer a basis for a prospective study to determine the role of LAA regional dysfunction by iME in predicting cerebrovascular events such as stroke or TIA.

Quantitative tissue-tracking cardiac magnetic resonance (CMR) of left atrial deformation and the risk of stroke in patients with atrial fibrillation

BACKGROUND

Recent evidence suggests that left atrial (LA) dysfunction may be mechanistically contributing to cerebrovascular events in patients with atrial fibrillation (AF). We investigated the association between regional LA function and a prior history of stroke during sinus rhythm in patients referred for catheter ablation of AF.

METHODS AND RESULTS

A total of 169 patients (59 ± 10 years, 74% male, 29% persistent AF) with a history of AF in sinus rhythm at the time of pre-ablation cardiac magnetic resonance (CMR) were analyzed. The LA volume, emptying fraction, strain (S), and strain rate (SR) were assessed by tissue-tracking cardiac magnetic resonance. The patients with a history of stroke or transient ischemic attack (n=18) had greater LA volumes (Vmax and Vmin; P=0.02 and P<0.001, respectively), lower LA total emptying fraction (P<0.001), lower LA maximum and pre-atrial contraction strains (Smax and SpreA; P<0.001 and P=0.01, respectively), and lower absolute values of LA SR during left ventricular (LV) systole and early diastole (SRs and SRe; P=0.005 and 0.03, respectively) than those without stroke/transient ischemic attack (n=151). Multivariable analysis demonstrated that the LA reservoir function, including total emptying fraction, Smax, and SRs, was associated with stroke/transient ischemic attack (odds ratio 0.94, 0.91, and 0.17; P=0.03, 0.02, and 0.04, respectively) after adjusting for the CHA2DS2-VASc score and LA Vmin.

CONCLUSIONS

Depressed LA reservoir function assessed by tissue-tracking cardiac magnetic resonance is significantly associated with a prior history of stroke/transient ischemic attack in patients with AF. Our findings suggest that assessment of LA reservoir function can improve the risk stratification of cerebrovascular events in AF patients.