Structure and Function of the Left Atrium and Left Atrial Appendage

Impact of Left Atrial Appendage Exclusion on Short-Term Outcomes in Isolated Coronary Artery Bypass Graft Surgery

BACKGROUND

The objective of this study was to evaluate the impact of left atrial appendage (LAA) exclusion on short-term outcomes in patients with atrial fibrillation undergoing isolated coronary artery bypass graft surgery.

METHODS

We queried the 2010 to 2014 National Readmissions Database for patients who underwent coronary artery bypass graft repair with and without LAA ligation by using International Classification of Diseases, Ninth Revision, Clinical Modification procedure codes (International Classification of Diseases, Ninth Revision, Clinical Modification: 36.1xx). Only patients with a history of atrial fibrillation were included in our analysis. The primary outcome of our study was 30-day readmissions following discharge. Secondary outcomes were in-hospital mortality and stroke. To assess the postoperative outcomes, we used multivariate logistic regression models to adjust for clinical and demographic covariates.

RESULTS

In total, we analyzed 253 287 patients undergoing coronary artery bypass graft surgery, 7.0% of whom received LAA closure. LAA exclusion was associated with a greater risk of postoperative respiratory failure (8.2% versus 6.2%, P<0.0001) and acute kidney injury (21.8% versus 18.5%, P<0.0001), but it did not significantly change the rate of blood transfusions or occurrence of cardiac tamponade. LAA exclusion was associated with a nonsignificant reduction in stroke (7.9% versus 8.6%, P=0.12), no difference in in-hospital mortality (2.2% versus 2.2% P=0.99), and a greater risk of 30-day readmission (16.0% versus 9.6%, P<0.0001). After covariate adjustment, LAA ligation remained a significant predictor of 30-day readmission (odds ratio, 1.640 [95% CI, 1.603-1.677], P<0.0001).

CONCLUSIONS

LAA exclusion during isolated coronary artery bypass graft surgery in patients with atrial fibrillation is associated with a higher rate of 30-day readmission. Postoperative measures to mitigate the loss of the hormonal and hemodynamic effects of the LAA may increase the therapeutic benefit of this procedure.

Interaction Effect of Diabetes and Acute Myocardial Infarction on the Left Atrial Function as Evaluated by 2-D Speckle-Tracking Echocardiography

The aim of the study described here was to investigate, using 2-D speckle-tracking echocardiography, whether myocardial infarction (MI) leads to diminished left atrial function in diabetic patients by comparison with non-diabetic patients. A total of 310 consecutive patients were divided into four groups based on the presence or absence of diabetes mellitus (DM) and acute ST-elevation MI. In the adjusted analysis, systolic and early diastolic strain and strain rate were reduced in the diabetic patients. Additionally, all deformation markers were impaired in the patients with MI. The DM-MI interaction was not statistically significant. Although reservoir, conduit and contraction functions of the left atrium were reduced in the patients with MI, left atrial reservoir and conduit functions were decreased in the diabetic patients. The reduction in left atrial function caused by MI was similar for diabetic and non-diabetic patients. Thus, DM and MI additively damaged left atrial function.

Utility of Cardiac MRI in Atrial Fibrillation Management

Advances in cardiac magnetic resonance (CMR) techniques and image acquisition have made it an excellent tool in the assessment of atrial myopathy. Remolding of the left atrium is the mainstay of atrial fibrillation (AF) development and its progression. CMR can detect phasic atrial volumes, atrial function, and atrial fibrosis using cine, and contrast-enhanced or non-contrast-enhanced images. These abilities make CMR a versatile and extraordinary tool in management of patients with AF including for risk stratification, ablation prognostication and planning, and assessment of stroke risk. We review the latest advancements in utility of CMR in management of patients with AF.

Global peak left atrial longitudinal strain assessed by transthoracic echocardiography is a good predictor of left atrial appendage thrombus in patients in sinus rhythm with heart failure and very low ejection fraction - an observational study

BACKGROUND

Peak left atrial longitudinal strain (PALS) can help identify left atrial appendage thrombus (LAAT) in patients with atrial fibrillation. Nevertheless, few studies have been performed in patients in sinus rhythm without established indications for anticoagulation but with increased risk of LAAT, such as heart failure (HF) with severe left ventricular systolic dysfunction patients. The primary aim of this study was to identify clinical and transthoracic echocardiography predictors of LAAT in HF patients with very low left ventricular ejection fraction and sinus rhythm. The secondary objective was to analyze frequencies and predictors of a composite clinical endpoint of death or hospitalization for ischemic stroke.

METHODS

We included 63 patients with HF, left ventricular ejection fraction < 25%, sinus rhythm at presentation, no history of atrial fibrillation, and without any established indications for anticoagulation. We determined whether clinical and transthoracic echocardiography parameters, including left atrial strain analysis, predicted LAAT. Transesophageal echocardiography was performed in all patients. When LAAT was detected, anticoagulation was recommended. The participants were followed for a median of 28.6 months (range 4-40) to determine the composite endpoint.

RESULTS

LAAT was found in 20 (31.7%) patients. Global PALS was the best independent predictor of LAAT in univariate and multivariate logistic regression analyses (Gini coefficient 0.65, area under the receiver-operating characteristic curve 0.83). A global PALS value below 8% was a good discriminator of LAAT presence (odds ratio 30.4, 95% CI 7.2-128, p <  0.001). During follow-up, 18 subjects (28.6%) reached the composite clinical endpoint. CHA₂DS₂-VASc score, use of angiotensin-converting-enzyme inhibitors or angiotensin receptor blockers, and body surface area were significant predictors for the composite endpoint of death or hospitalization for ischemic stroke in the multivariate regression model.

CONCLUSIONS

LAAT was relatively common in our group of HF patients and PALS has shown prognostic potential in LAAT identification. Further research is needed to determine whether initiation of anticoagulation or additional screening supported by PALS measurements will improve clinical outcomes in these patients.

Use of Cardiac Computed Tomography and Magnetic Resonance Imaging in Case Management of Atrial Fibrillation with Catheter Ablation

Atrial fibrillation (AF) is the most common arrhythmia associated with the risk of morbidity and mortality in clinical patients. AF is considered as an arrhythmia type that develops and progresses through close connection with cardiac structural arrhythmogenic substrates. Since the introduction of catheter ablation-mediated electrical isolation of arrhythmogenic substrates, cardiac imaging indicates improved treatment outcome and prognosis with appropriate candidate selection, ablation catheter guidance, and post-ablation follow-up. Currently, cardiac computed tomography (CCT) and cardiovascular magnetic resonance (CMR) imaging are essential in the case management of AF at both pre-and post-procedural stages of catheter ablation. In this review, we discuss the roles and technical considerations of CCT and CMR imaging in the management of patients with AF undergoing catheter ablation.

Left Atrial Phasic Function in Patients with Hypertension and Recurrent Atrial Fibrillation: Gender Differences of the Relationship with Diastolic Dysfunction and Central Aortic Pressure

Aim. To evaluate gender-related differences of left atrial (LA) phasic function and structural remodeling in conjunction with the parameters of left ventricular (LV) diastolic dysfunction and central aortic pressure in patients with hypertension and recurrent atrial fibrillation (AF).

Material and methods. The comparative study included 30 men and 37 women with non-valvular AF, hypertension and LV hypertrophy. Conventional echocardiographic measures were extended with LA measures, including its volume in three phases, LAemptying fraction (LAEF), passive and active ejection fraction. The parameters of central aortic pressure were estimated by applanation tonometry method.

Results. No difference was observed between LA and LV structural parameters in men and women. However, in women LAEF (39 [28;50] vs 50 [42;55]%; p=0.02) and E/E’(9.7 [7.8;12] vs 7.1 [5.6;8.6]; p=0.001) were worse than in men. Active LA ejection fraction was higher in women (31 [21;42] vs 24 [19;31]%; p=0.04), whereas passive one – in men (12 [10;14] vs 33 [23;38]%; p<0.001), respectively. Men and women had comparable heart rate (HR), central and peripheral systolic and diastolic pressure, pulse wave velocity (PWV), but women had higher augmentation index (AI) values [33 [28;39] vs 23 [21;28]%; p<0.001], even adjusted by HR (AI 75) (34 [27;39] vs 26 [20;29]%; p<0.001). Only in men PWV weakly correlated with AI 75 (r=0.44; p=0.02 versus r=-0.11; p=0.51, respectively for men and women; intergroup differences: z=2.26; p=0.012). In a multivariate regression analysis in men LAEF was significantly associated with height, weight, E’, E/E’ and glomerular filtration rate (GFR), whereas in women – with E’ and AI 75.

Conclusion. Patients of different genders with recurrent AF and hypertension have comparable LA structuralremodeling. However, women characterized by a more pronounced decrease in LAEF and impaired LV diastolic function than men. In women as distinct from men LV filling is predominantly due to LA systole. In a multivariate regression analysis in men LAEF was significantly associated with height, weight, E’, E/E’ and GFR, whereas in women – with E’ and AI 75. 

The left atrial appendage in humans: structure, physiology, and pathogenesis

For many years, the left atrial appendage (LAA) was considered a dormant embryological remnant; however, it is a structurally complex and functional organ that contributes to cardiac haemodynamic changes and volume homeostasis through both its contractile properties and neurohormonal peptide secretion. When dysfunctional, the LAA contributes to thrombogenesis and subsequent increased predisposition to cardioembolic events. Consequently, the LAA has gained much attention as a therapeutic target to lower this risk. In addition, attention has focused on the LAA in its role as an electrical trigger for atrial tachycardia and atrial fibrillation with ablation of the LAA to achieve electrical isolation showing promising results in the maintenance of sinus rhythm. This in-depth review explores the structure, physiology and pathophysiology of the LAA, as well as LAA intervention and their sequelae.

Left Atrial Structure and Function, and Left Ventricular Diastolic Dysfunction: JACC State-of-the-Art Review

Defining left atrial (LA) function has recently emerged as a powerful parameter, particularly in evaluation of left ventricular (LV) diastolic dysfunction (LVDD) and heart failure with preserved ejection fraction. Echocardiographic assessment of LVDD by echocardiography remains a challenging task; recent recommendations provide a simpler approach than previous. However, the shortcomings of the proposed approach (including transmitral flow, tissue velocity, maximum left atrial volume [LAV], and estimated pulmonary artery systolic pressure), lead to the presence and severity of LVDD remaining undetermined in a significant proportion of patients. Maximum LAV is a surrogate measure of the chronicity and severity of LVDD, but LAV alone is an insensitive biomarker of early phases of LVDD, because the LA may take time to remodel. Because the primary function of the LA is to modulate LV filling, it is not surprising that functional LA changes become evident at the earliest stages of LVDD. Moreover, LA function may provide additive value, not only in diagnosing LVDD, but also in grading its severity and in monitoring the effects of treatment. The current review provides a critical appraisal on the existing evidence for the role of LA metrics in evaluation of LVDD and consequent heart failure with preserved ejection fraction.

Regional Disparities of Left Atrial Appendage Wall Contraction in Patients With Sinus Rhythm and Atrial Fibrillation

BACKGROUND

Patients with atrial fibrillation (AF) exhibit impaired left atrial appendage (LAA) function. However, regional characteristics of LAA function in patients with AF are not defined.

METHODS

Consecutive patients (n = 1,195) undergoing transesophageal echocardiography at a university hospital were included. Patients were divided into three groups on the basis of their rhythm: sinus rhythm (SR), paroxysmal AF, and permanent or persistent AF. Regional LAA wall velocities were determined using color Doppler tissue imaging, placing regions of interest at the lateral and medial wall of the LAA.

RESULTS

Of the 1,182 patients ultimately included, 691 (59%) were in SR, 371 (32%) had permanent or persistent AF, and 120 (10%) had paroxysmal AF with SR at the time of transesophageal echocardiography. Both lateral and medial LAA wall velocities were lower in patients with AF in comparison with those in SR. Nearly 90% of patients in both groups of patients with AF exhibited a pattern of medial LAA wall velocity greater than lateral LAA wall velocity, in comparison with 20% of patients with SR. The odds ratio for the association of this LAA contraction pattern with AF was 22.14 (95% CI, 12.06-40.64; P < .001). The movement of lateral LAA wall velocity showed the highest correlation with LAA emptying velocity compared with the medial LAA wall (r = 0.67, P < .001).

CONCLUSIONS

Lateral LAA wall velocity is higher than medial LAA wall velocity in patients in SR, which reverses in patients with AF. Assessment of LAA regional wall velocity using Doppler tissue imaging appears to be a promising approach to identify patients with paroxysmal AF.

Does Alignment in Statistical Shape Modeling of Left Atrium Appendage Impact Stroke Prediction?

Evidence suggests that the shape of left atrium appendages (LAA) is a primary indicator in predicting stroke for patients diagnosed with atrial fibrillation (AF). Statistical shape modeling tools used to represent (i.e., parameterize) the underlying LAA variability are of crucial importance to learn shape-based predictors of stroke. Most shape modeling techniques use some form of alignment either as a data pre-processing step or during the modeling step. However, the LAA is a joint anatomy along with left atrium (LA), and the relative position and alignment plays a crucial part in determining risk of stroke. In this paper, we explore different alignment strategies for statistical shape modeling and how each strategy affects the stroke prediction capability. This allows for identifying a unified approach of alignment while analyzing the LAA anatomy for stroke. Here, we study three different alignment strategies, (i) global alignment, (ii) global translational alignment and (iii) cluster based alignment. Our results show that alignment strategies that take into account LAA orientation, i.e., (ii), or the inherent natural clustering of the population under study, i.e., (iii), provide significant improvement over global alignment in both qualitative as well as quantitative measures.

Cardiac autotransplantation and ex vivo surgical repair of giant left atrium: a case presentation

BACKGROUND

Chronic Mitral Valve disease is strongly associated with Left atrial enlargement; the condition has a high mortality risk. Clinical manifestations include atrial fibrillation, pulmonary hypertension, thromboembolic events, and in cases of Giant Left Atrium (GLA) and a distorted cardiac silhouette. Full sternotomy, conventional open-heart surgery, reductive atrioplasty and atrioventricular valve repair are required to resolve symptoms. However, these procedures can be complicated due to the posterior location of the GLA and concomitant right lateral protrusion. Cardiac autotransplantation is superior under these conditions; it provides improved visual access to the posterior atrial wall and mitral valve, hence, facilitates corrective surgical procedures. We aimed to assess the clinical outcome of patients undergoing cardiac autotransplantation as the primary treatment modality to resolve GLA. Moreover, we evaluated the procedural safety profile and technical feasibility.

CASE PRESENTATION

Four patients, mean EuroSCORE II of 23.7% ± 7.7%, presented with heart failure, atrial fibrillation, left atrial diameter > 6.5 cm and a severe distorted cardiac silhouette; X-ray showed prominent right lateral protrusion. We performed cardiac autotransplantation using continuous retrograde perfusion with warm blood supplemented with glucose followed by atrioplasty, atrial plication, valve annuloplasty and valve repair on the explanted beating heart. The surgical approach reduced the left atrial area, mean reduction was - 90.71 cm² [CI95% -153.3 cm² to - 28.8 cm², p = 0.02], and normalized pulmonary arterial pressure, mean decrease - 11.25 mmHg [CI95% -15.23 mmHg to - 7.272 mmHg, p = 0.003]. 3 out of 4 patients experienced an uneventful postoperative course; 2 out of 4 patients experienced a transient return to sinus rhythm following surgery. One was operated on in 2017 and is still in good condition; two other patients survived for more than 10 years; Kaplan-Meier determined median survival is 10.5 years.

CONCLUSIONS

Cardiac autotransplantation is an elegant surgical procedure that facilitates the surgical remodelling of Giant Left Atrium. Surgical repair on the ex vivo beating heart, under continuous warm blood perfusion, is a safe procedure applicable also to high-risk patients.

Decreased platelet-to-lymphocyte ratio as predictor of thrombogenesis in nonvalvular atrial fibrillation

BACKGROUND

Inflammation plays a key role in the progression of atrial fibrillation and its related prothrombotic state. The platelet-to-lymphocyte ratio (PLR) is an easily obtainable biomarker of inflammatory burden. Decreased left atrial appendage flow velocity (LAA-FV) reflects blood stasis, and left atrial strain is a manifestation of atrial remodeling. This study examined the role of PLR in reflecting decreased LAA-FV and its correlation with impaired left atrial strain.

METHODS

In 54 patients with nonvalvular atrial fibrillation, LAA-FV and left atrial strain were measured by echocardiography. The PLR was calculated from a complete blood count.

RESULTS

The PLR was lower in the group of patients with decreased LAA-FV (84.22 [IQR, 69.87-98.17 cm/s] vs. 103.27 [IQR, 90.37-127.16 cm/s]; p = 0.018). PLR was predictive of decreased LAA-FV with a sensitivity of 66.7% and a specificity of 83.3%. In a receiver operator characteristic curve analysis, using a cut-off value of 88.16, the area under the curve for PLR as a predictor of decreased LAA-FV was 0.726 (p = 0.018). Furthermore, the patients with a PLR of < 88.16 had a lower left atrial strain than those with a PLR of > 88.16 (0.38 vs. 0.77, p = 0.02).

CONCLUSION

The PLR was lower in patients with nonvalvular atrial fibrillation and with a decreased LAA-FV. Its correlation with left atrial strain might indicate the role of inflammation in the progression of atrial remodeling and in the prothrombotic state.

Perioperative Echocardiographic Index of Left Ventricular Filling Pressure in Cardiac Surgery

BACKGROUND

The elevated preoperative ratio of early transmitral flow velocity to early diastolic velocity of the mitral annulus (E/e') as an echocardiographic index of left ventricular filling pressure is known to be associated with poor postoperative outcomes. We investigated the association between preoperative and postoperative E/e' elevation and clinical outcomes after cardiac operations.

METHODS

The study divided 1,353 patients who underwent cardiac operations into four groups: preoperative and postoperative E/e' ≤15 (low-low), preoperative E/e' ≤15 but postoperative E/e' >15 (low-high), preoperative E/e' >15 but postoperative E/e' ≤15 (high-low), and preoperative and postoperative E/e' >15 (high-high). Cox proportional hazard analysis was performed. Kaplan-Meier curve analysis was performed before and after propensity score matching.

RESULTS

The four perioperative E/e' categories were independently associated with 5-year mortality (hazard ratio, high-high vs low-low: 3.58; low-high vs low-low: 3.75; high-low vs low-low: 1.18). Kaplan-Meier curves showed that mortality was significantly different between the groups (log-rank test: high-high vs. low-low, p < 0.001; low-high vs low-low, p < 0.001). Postoperative intensive care unit and hospital lengths of stay, incidence of acute kidney injury, and 1-year mortality were significantly different. However, after propensity score matching, mortality and the incidence of postoperative acute kidney injury were significantly different only between postoperative E/e' ≤15 and E/e' >15, but not between preoperative E/e' ≤15 and E/e' >15.

CONCLUSIONS

Postoperative E/e' >15 was more strongly associated with mortality and acute kidney injury than preoperative E/e' >15. Measurement of the postoperative E/e' ratio may help in assessing the risk of these patients.

Atrial Cardiopathy and Sympatho-Vagal Imbalance in Cryptogenic Stroke: Pathogenic Mechanisms and Effects on Electrocardiographic Markers

Recently, atrial cardiopathy has emerged as possible pathogenic mechanism in cryptogenic stroke and many electrocardiographic (ECG) markers have been proposed in order to detect an altered atrial substrate at an early stage. The autonomic nervous system (ANS) plays a well-known role in determining significant and heterogeneous electrophysiological changes of atrial cardiomyocytes, that promote atrial fibrillation episodes in cardioembolic stroke. Conversely, the role of ANS in atrial cardiopathy and cryptogenic stroke is less known, as well as ANS effects on ECG markers of atrial dysfunction. In this paper, we review the evidence linking ANS dysfunction and atrial cardiopathy as a possible pathogenic factor in cryptogenic stroke.

Computational Flow Dynamic Analysis of Right and Left Atria in Patent Foramen Ovale: Potential Links with Atrial Fibrillation

Background

An impairment of the left atrial function similar to that usually observed in atrial fibrillation (AF) has been observed also in patients with patent foramen ovale (PFO) and permanent right-to-left shunting (RLS).

Methods

We reconstructed the geometrical model of right atrium (RA), PFO, left atrium (LA) and left atrial appendage (LAA) of 65 patients with mild (36 patients mean age 45.5±6.8 years, 24 females) or permanent (29 patients, mean age 45.1±5.3 years, 21 females) RLS using anatomical data obtained by transoesophageal echocardiography (TEE) and cardiac MRI, performed as a part of our institutional screening protocol for paradoxical embolism. Using computational fluid dynamic analysis (CFD) we assessed the vorticity magnitude in both the LA and LAA to analyse a possible rheological relationship between PFO and AF.

Results

The anatomical models, in terms of dimensions, were comparable among the patients with mild and permanent RLS. A higher vorticity magnitude was observed in the mild shunt both in the LA (101.12±21.3 vs 88.3±22.6, p=0.02) and LAA (62±14.4 vs 32.4±12.3, p<0.01) when compared to the permanent R-L shunting.

Conclusion

The lower vorticity magnitude across the LA and LAA in patients with permanent RLS suggests a possible higher stagnation of the blood in these anatomical sites, similarly as previously observed in patients with AF.

Editor-in-Chief's Top Picks From 2017

Each week, I record audio summaries for every article in JACC, as well as an issue summary. While this process has been time-consuming, I have become quite familiar with every paper that we publish. Thus, I personally select papers (both original investigations and review articles) from 15 distinct specialties each year for your review. In addition to my personal choices, I have included manuscripts that have been the most accessed or downloaded on our websites, as well as those selected by the JACC Editorial Board members. In order to present the full breadth of this important research in a consumable fashion, we will present these manuscripts in this issue of JACC. The highlights comprise the following sections: Basic & Translational Research, Cardiac Failure, Cardiomyopathies/Myocardial & Pericardial Diseases, Cardio-oncology, Congenital Heart Disease, Coronary Disease & Interventions, CVD Prevention & Health Promotion, Hypertension, Imaging, Metabolic & Lipid Disorders, Rhythm Disorders, Valvular Heart Disease, and Vascular Medicine (1-110).