Left Atrial Function Assessed by Tissue Doppler Imaging as a New Predictor of Cardiac Events after Non-ST-Elevation Acute Coronary Syndrome

Impact of Cardiac Magnetic Resonance Left Atrial Ejection Fraction in Advanced Ischemic Cardiomyopathy

BACKGROUND

The prognostic significance of cardiac magnetic resonance (CMR)-based left atrial ejection fraction (LAEF) is not well defined in the ischemic cardiomyopathy (ICM) cohort.

OBJECTIVES

The authors sought to assess the prognostic impact of LAEF, when adjusted for left ventricular remodeling, myocardial infarct size (MIS), left atrial volume index, and functional mitral regurgitation (FMR), on outcomes in patients with advanced ICM.

METHODS

ICM patients who underwent CMR were retrospectively evaluated (April 2001-December 2019). LAEF, left atrial volume index, MIS, left ventricular remodeling, and FMR were derived from CMR. The primary clinical endpoint was a composite of all-cause mortality and cardiac transplant. A baseline multivariable Cox proportional hazards regression model was constructed to assess prognostic power of LAEF.

RESULTS

There were 718 patients (416 primary events) evaluated, with a median duration of follow-up of 1,763 days (4.8 years) and a mean LAEF of 36% ± 15%. On multivariable analysis, higher LAEF was independently associated with reduced risk (HR: 0.24, 95% CI: 0.12-0.48, P < 0.001), even after adjusting for FMR and MIS. The highest adjusted risk was observed in patients with an LAEF <20% and an MIS of >30% (HR: 3.20, 95% CI: 1.73-5.93). The lowest risk was in patients within the comparator group with an LAEF of >50% and a MIS of <15% (HR: 1.07, 95% CI: 0.81-1.42).

CONCLUSIONS

Reduced LAEF is independently associated with increased mortality in ICM. Risk associated with declining LAEF is continuous and incremental to other risk factors for adverse outcomes in patients with ICM even after adjusting for MIS and FMR severity.

Characterization of left and right atrial function in healthy volunteers by cardiovascular magnetic resonance

BACKGROUND

Left and right atrial function show a different pattern in advanced age in order to maintain adequate ventricular filling. It has been shown that left atrial (LA) function has a prognostic value in a number of heart conditions. Cardiovascular magnetic resonance (CMR) provides high quality images of the left and right atria using high temporal resolution steady state free precession (SSFP) cine sequences. We used SSFP cines to characterize atrial function in healthy, normotensive, volunteers.

METHODS

We measured maximum, preatrial contraction and minimum left and right atrial volumes in 120 healthy subjects after careful exclusion of cardiovascular abnormality (60 men, 60 women; 20 subjects per age decile from 20 to 80 years). Data were generated from 3-dimensional modeling, including tracking of the atrioventricular ring motion and time-volume curves analysis. With those measurements, all the usual parameters for left and right atrial function were calculated.

RESULTS

Gender had significant influence on some parameters of left and right atrial conduit and booster pump function. Age significantly influenced the majority of parameters of both left and right atrial function, with typically lower reservoir and conduit functions and higher booster pump function, both in males and females belonging to older age groups. CMR normal ranges were modelled for clinical use with normalization, where appropriate, for body surface area and gender, displaying parameters with respect to age.

CONCLUSIONS

CMR normal reference ranges for components of left and right atrial function are provided for males and females for a wide age range.

Left atrium function in patients with coronary artery disease

PURPOSE OF REVIEW

The left atrial cavity has recently been identified as a potential biomarker for cardiac and cerebrovascular accidents. This review examines the potential of left atrial size and function in predicting cardiovascular disease in the general population and outcomes in coronary artery disease (CAD) patients.

RECENT FINDINGS

The atrium is perfused primarily by branches of the proximal left circumflex coronary artery (LCx), and depression of the cavity mechanical performance has been demonstrated in experimental studies during LCx occlusion. Thus, left atrial volume and function assessment may have prognostic relevance, particularly in CAD patients. Such a line of thinking, however, is challenged by the widespread notion that the contribution by left atrial chamber morphology and functional quantitation to the risk stratification process after a first cardiovascular event is not adequately considered. However, a number of studies have shown that left atrial volume predicts survival and major adverse events after an acute myocardial infarction. Left atrial remodeling also provides an important overall prognostic information and correlates with brain natriuretic peptide after primary percutaneous coronary interventions.

SUMMARY

Evaluation of left atrial size and function is currently of great interest and it will be more so in the very near future, given its potential for insights into the pathophysiology of the ischemic heart, which makes it an important clinical risk identifier in CAD patients.

Left atrial geometry and pump function in ischemic cardiomyopathy

Background

Many of the factors that are known to alter left atrial (LA) contractility are present in patients with ischemic cardiomyopathy (ICM). Nevertheless, preservation of LA contractile function in this group of patients was reported in previous studies. The aim of this study was to assess the changes in LA size, geometry and contractile function in ICM.

Methods and results

60 subjects (age: 49 ± 12 years, 53% males) in sinus rhythm undergoing coronary angiography (CA), were enrolled in this study; 15 subjects as a control group, 30 patients with reduced ejection fraction (EF) and significant coronary artery disease; as the ICM group, and 15 with reduced EF and normal CA; as the dilated cardiomyopathy (DCM) group.

LA dimensions, volume, active emptying fraction (ACTEF) and eccentricity index (LAEi) as well as late diastolic velocities of the mitral annulus (a′) and LA free wall (A₃) were measured.

Compared with the control group, ICM patients had larger LA volume and reduced ACTEF, a′ and A₃, with no significant difference between patients with ICM and DCM in any of these parameters. LA eccentricity was, non-significantly, higher in both cardiomyopathy groups than in the control group.

Conclusions

Patients with ICM have increased LA volume and reduced LA contractile function in comparison with normal controls. LA enlargement, LA contractile dysfunction and LA geometric changes in ICM are similar to that occurring in DCM. LA size, contractile function and eccentricity may not be reliable in differentiating ischemic from idiopathic dilated cardiomyopathy.

Left atrial function assessed by left atrial strain in patients with left circumflex branch culprit acute myocardial infarction

INTRODUCTION

Although left atrium (LA) has played an important role in diastole, ischemic insult of atrium in acute myocardial infarction (AMI) has not been clearly evaluated.

METHODS

We hypothesized that LA function would be further decreased in AMI patients with a culprit lesion in the left circumflex branch (LCX). This was an observational cohort study in a single university hospital. Echocardiography was performed to evaluate left ventricular diastolic function, LA volume, and LA function. Systolic (LAS ) and late diastolic (LAA ) LA strain were measured using speckle tracking echocardiography.

RESULTS

Sixty-eight AMI patients treated with emergent or urgent percutaneous coronary intervention were enrolled. Global LAS strain was significantly lower in patients with a culprit lesion in the LCX than culprit lesions in other vessels (left anterior descending, 27.3 ± 6.8%; left circumflex, 20.1 ± 8.9%; right coronary artery, 23.3 ± 6.5%; P = 0.007). LA volume index did not differ significantly (P = 0.093). Other clinical and conventional echocardiographic parameters, including Doppler measurements, did not differ significantly.

CONCLUSIONS

Global LAS strain was lower in AMI patients with a culprit lesion in the LCX than those with culprit lesions in other vessels, without any significant difference in LA volume index. The lower global LAS strain might suggest decreased LA function resulting from ischemic insult by AMI with culprit lesions in the LCX.

Left atrial mechanics: echocardiographic assessment and clinical implications

The importance of the left atrium in cardiovascular performance has long been acknowledged. Quantitative assessment of left atrial (LA) function is laborious, requiring invasive pressure-volume loops and thus precluding its routine clinical use. In recent years, novel postprocessing imaging methodologies have emerged, providing a complementary approach for the assessment of the left atrium. Atrial strain and strain rate obtained using either Doppler tissue imaging or two-dimensional speckle-tracking echocardiography have proved to be feasible and reproducible techniques to evaluate LA mechanics. It is essential to fully understand the clinical applications, advantages, and limitations of LA strain and strain rate analysis. Furthermore, the technique's prognostic value and utility in therapeutic decisions also need further elucidation. The aim of this review is to provide a critical appraisal of LA mechanics. The authors describe the fundamental concepts and methodology of LA strain and strain rate analysis, the reference values reported with different imaging techniques, and the clinical implications.

Evaluation of biatrial size and functions by different echocardiographic parameters in patients with acute coronary syndromes

After acute coronary syndromes (ACS), cardiac remodelling affecting not only ventricles but also both atria is an important problem associated with an increased risk for adverse cardiovascular outcomes. However, it is usually underestimated to evaluate atrial size and functions. The aim of the present study is to compare left and right atrial size and functions in ACS patients with healthy controls during transthoracic echocardiography by means of diameter, area and volume measurements, and pulsed-wave tissue Doppler imaging (TDI). 150 ACS patients (128 male, 22 female) and 25 healthy controls (19 male, 6 female) were enrolled into the study. Of the ACS patients, 75 had ST-segment elevation myocardial infarction (STEMI) and 75 had non-STEMI. Biatrial diameters, areas, and volumes were measured from different echocardiographic views. Atrial total emptying fraction and expansion index values were calculated from volume measurements. By the pulsed-wave TDI of the atrial walls; peak systolic (S'), peak early diastolic (E'), and peak late diastolic (A') velocities were measured. Almost all left atrial parameters for diameter, area, and volume measurements were higher in ACS patients. Similarly, they had higher values for the same right atrial parameters. Left and right atrial total emptying fraction and expansion index values were lower in ACS patients than controls. All left and right atrial walls had lower S' and E' velocities in ACS patients. ACS cause important alterations in the biatrial size and functions evaluated by echocardiographic diameter, area and volume measurements, and pulsed-wave TDI.