Comparison of left atrial dimensions by transesophageal and transthoracic echocardiography

Echocardiographic clues of the "atrial pump mechanism" during cardiopulmonary resuscitation

Instead of the ventricles, atria may be the cardiac structures mainly compressed during cardiopulmonary resuscitation (CPR). This study aimed to assess the prevalence and the mechanical characteristics of atrial compression, named the "atrial pump mechanism", in patients undergoing CPR. A retrospective cohort study was conducted on patients with witnessed refractory out-of-hospital cardiac arrest who were admitted to a tertiary referral center for extracorporeal CPR. The area of maximal compression (AMC) by chest compressions was assessed by transesophageal echocardiography. Right atrial wall excursion (RAWE), left atrial fractional shortening (LAFS), right ventricular fractional area change (RVFAC), and left ventricular fractional shortening (LVFS) were measured. Common carotid and middle cerebral artery peak velocities were assessed using color-Doppler imaging as markers of cardiac outflow and cerebral perfusion. Forty patients were included in the study. Five (12.5%) had AMC over the atria. The atrial pump pattern was characterized by marked atrial compression with higher RAWE and LAFS values compared to the other patients (p < 0.001). Common carotid Doppler and transcranial Doppler-velocity patterns were detectable in all patients with open left ventricular outflow tract, without differences between patients. CPR was successful in four patients (80%) with atrial pump compared to 14 (40%) with no atrial pump mechanism (p = 0.155). In this series of selected patients with witnessed cardiac arrest, the prevalence of the atrial pump mechanism was not negligible. It may contribute to forward blood flow and the maintenance of cerebral perfusion during prolonged cardiopulmonary resuscitation.

Baseline Intraoperative Left Ventricular Diastolic Function Is Associated with Postoperative Atrial Fibrillation after Cardiac Surgery

BACKGROUND

Detailed understanding of the association between intraoperative left atrial and left ventricular diastolic function and postoperative atrial fibrillation is lacking. In this post hoc analysis of the Posterior Left Pericardiotomy for the Prevention of Atrial Fibrillation after Cardiac Surgery (PALACS) trial, we aimed to evaluate the association of intraoperative left atrial and left ventricular diastolic function as assessed by transesophageal echocardiography (TEE) with postoperative atrial fibrillation.

METHODS

PALACS patients with available intraoperative TEE data (n = 402 of 420; 95.7%) were included in this cohort study. We tested the hypotheses that preoperative left atrial size and function, left ventricular diastolic function, and their intraoperative changes were associated with postoperative atrial fibrillation. Normal left ventricular diastolic function was graded as 0 and with lateral e' velocity 10 cm/s or greater. Diastolic dysfunction was defined as lateral e' less than 10 cm/s using E/e' cutoffs of grade 1, E/e' 8 or less; grade, 2 E/e' 9 to 12; and grade 3, E/e' 13 or greater, along with two criteria based on mitral inflow and pulmonary wave flow velocities.

RESULTS

A total of 230 of 402 patients (57.2%) had intraoperative diastolic dysfunction. Posterior pericardiotomy intervention was not significantly different between the two groups. A total of 99 of 402 patients (24.6%) developed postoperative atrial fibrillation. Patients who developed postoperative atrial fibrillation more frequently had abnormal left ventricular diastolic function compared to patients who did not develop postoperative atrial fibrillation (75.0% [n = 161 of 303] vs. 57.5% [n = 69 of 99]; P = 0.004). Of the left atrial size and function parameters, only delta left atrial area, defined as presternotomy minus post-chest closure measurement, was significantly different in the no postoperative atrial fibrillation versus postoperative atrial fibrillation groups on univariate analysis (-2.1 cm2 [interquartile range, -5.1 to 1.0] vs. 0.1 [interquartile range, -4.0 to 4.8]; P = 0.028). At multivariable analysis, baseline abnormal left ventricular diastolic function (odds ratio, 2.02; 95% CI, 1.15 to 3.63; P = 0.016) and pericardiotomy intervention (odds ratio, 0.46; 95% CI, 0.27 to 0.78, P = 0.004) were the only covariates independently associated with postoperative atrial fibrillation.

CONCLUSIONS

Baseline preoperative left ventricular diastolic dysfunction on TEE, not left atrial size or function, is independently associated with postoperative atrial fibrillation. Further studies are needed to test if interventions aimed at optimizing intraoperative left ventricular diastolic function during cardiac surgery may reduce the risk of postoperative atrial fibrillation.

EDITOR’S PERSPECTIVE

Multimodality Imaging in the Study of the Left Atrium

The left atrium (LA) plays a vital role in maintaining normal cardiac function. Many cardiac diseases involve the functioning of the LA directly or indirectly. For this reason, the study of the LA has become a priority for today's imaging techniques. Assessment of LA size, function and wall characteristics is routinely performed in cardiac imaging laboratories when a patient undergoes transthoracic echocardiography. However, in cases when the LA is the focus of disease management, such as in atrial fibrillation or left atrial appendage closure, the use of multimodality is critical. Knowledge of the usefulness of each cardiac imaging technique for the study of LA in these patients is crucial in order to choose the most appropriate treatment. While echocardiography is the most widely performed technique for its evaluation and the study of wall deformation analysis is increasingly becoming more reliable, multidetector computed tomography allows a detailed analysis of its anatomy to be carried out in 3D reconstructions that help in the approach to interventional treatments. In addition, the evaluation of the wall by cardiac magnetic resonance imaging or the generation of electroanatomical maps in the electrophysiology room have become essential tools in the treatment of multiple atrial pathologies. For this reason, the goal of this review article is to describe the basic anatomical and functional information of the LA as well as their study employing the main imaging techniques currently available, so that practitioners specializing in cardiac imaging techniques can use these tools in an accurate and clinically useful manner.

Guidelines for the Use of Transesophageal Echocardiography to Assist with Surgical Decision-Making in the Operating Room: A Surgery-Based Approach: From the American Society of Echocardiography in Collaboration with the Society of Cardiovascular Anesthesiologists and the Society of Thoracic Surgeons

Intraoperative transesophageal echocardiography is a standard diagnostic and monitoring tool employed in the management of patients undergoing an entire spectrum of cardiac surgical procedures, ranging from "routine" surgical coronary revascularization to complex valve repair, combined procedures, and organ transplantation. Utilizing a protocol as a starting point for imaging in all procedures and all patients enables standardization of image acquisition, reduction in variability in quality of imaging and reporting, and ultimately better patient care. Clear communication of the echocardiographic findings to the surgical team, as well as understanding the impact of new findings on the surgical plan, are paramount. Equally important is the need for complete understanding of the technical steps of the surgical procedures being performed and the complications that may occur, in order to direct the postprocedure evaluation toward aspects directly related to the surgical procedure and to provide pertinent echocardiographic information. The rationale for this document is to outline a systematic approach describing how to apply the existing guidelines to questions on cardiac structure and function specific to the intraoperative environment in open, minimally invasive, or hybrid cardiac surgery procedures.

Comparison of Left Atrial Measurements Using 2- and 3-Dimensional Transesophageal Echocardiography

OBJECTIVES

To assess the correlation between left atrial measurements using 2- and 3-dimensional transesophageal echocardiography.

DESIGN

Prospective, observational study.

SETTING

Single, tertiary care, academic medical center.

PARTICIPANTS

The study comprised 63 consecutive patients undergoing cardiac surgery with cardiopulmonary bypass and intraoperative transesophageal echocardiography.

INTERVENTIONS

In addition to the standard comprehensive intraoperative transesophageal examination, study images were obtained by designated anesthesiologists from the study team.

MEASUREMENTS AND MAIN RESULTS

The 2-dimensional transesophageal echocardiography views included 4-chamber, 2-chamber, aortic valve short axis, and aortic valve long axis. For the 3-dimensional images, full-volume (90 × 90) data sets were acquired from 4-chamber and aortic valve short-axis views over 4 beats with apnea. Left atrial height, mediolateral length, anteroposterior length, and area were measured in 2- and 3-dimensional images. Left atrial length in the short- and long-axis views of the aortic valve also were measured in 2- and 3-dimensional images. Results indicate that for all patients in this study, the 2- and 3-dimensional measurements correlate well and the 2 observers were in agreement with each other.

CONCLUSIONS

Two- and 3-dimensional measurements of the left atrium correlated well. Measurements made using 3-dimensional transesophageal echocardiography were subject to similar limitations as those made using 2-dimensional echocardiography. The benefits of 3-dimensional transesophageal echocardiography and multiplanar reconstruction could be expanded by improvements in ultrasound technology and software.

[Consensus on Perioperative Transesophageal Echocardiography of the Brazilian Society of Anesthesiology and the Department of Cardiovascular Image of the Brazilian Society of Cardiology]

Through the Life Cycle of Intraoperative Transesophageal Echocardiography (ETTI/SBA) the Brazilian Society of Anesthesiology, together with the Department of Cardiovascular Image of the Brazilian Society of Cardiology (DIC/SBC), createded a task force to standardize the use of intraoperative transesophageal echocardiography by Brazilian anesthesiologists and echocardiographers based on scientific evidence from the Society of Cardiovascular Anesthesiologists/American Society of Echocardiography (SCA/ASE) and the Brazilian Society of Cardiology.

Consensus on Perioperative Transesophageal Echocardiography of the Brazilian Society of Anesthesiology and the Department of Cardiovascular Image of the Brazilian Society of Cardiology

Through the Life Cycle of Intraoperative Transesophageal Echocardiography (ETTI/SBA) the Brazilian Society of Anesthesiology, together with the Department of Cardiovascular Image of the Brazilian Society of Cardiology (DIC/SBC), created a task force to standardize the use of intraoperative transesophageal echocardiography by Brazilian anesthesiologists and echocardiographers based on scientific evidence from the Society of Cardiovascular Anesthesiologists/American Society of Echocardiography (SCA/ASE) and the Brazilian Society of Cardiology.

Transesophageal Echocardiography in Swine: Establishment of a Baseline

The porcine model is a commonly used animal model in cardiovascular research. Along with new innovative operative techniques, choice of the optimal imaging technique is crucial. Transesophageal echocardiography (TEE) is a reliable imaging tool is highly important in a large number of experimental evaluations. But so far, TEE data for swine are limited, and few standard values have been established for the porcine model. The experience and baseline results for TEE in 45 swine are presented in this study. A full TEE examination was conducted in 45 German landrace or German large white swine, with an average body weight of 49 ± 3 kg, before experimental off-pump mitral valved stent implantation. Additionally hemodynamic measurements were evaluated. The valve implantation procedure was guided solely by real-time 3-D TEE. Baseline values of standard echocardiographic parameters are provided and, where appropriate, compared with human reference values. TEE proved to be an adequate imaging technique in this experimental porcine animal model. The baseline TEE and hemodynamic parameters established for the widely used porcine model can serve as a reference in future studies.

Perioperative Diastolic Dysfunction

Left ventricular diastolic dysfunction (LVDD) has only recently been recognized as an important determinant of perioperative morbidity. Intraoperative echocardiographers have been slow to adopt assessment of LVDD into clinical practice. This has been partly attributable to the complex measurements required to characterize LVDD, which are in turn related to how our understanding of diastole has evolved. Additionally, the lack of effective therapeutic options has left many wondering whether it is worthwhile to characterize this pathology in the first place. However, therapies are developed more rapidly once a problem can be identified reliably. The assessment of LVDD is centered on how effectively the left ventricle can fill. Diastolic dysfunction affects intraventricular pressures and stiffness, which in turn affect the pressure relationship between the left atrium and the left ventricle thereby affecting transmitral flow. Since echocardiography can enable the measurement of flow velocities, transmitral diastolic filling flow patterns provide robust information on diastolic function. The impact of abnormal diastolic function on left atrial pressure has consequences for pulmonary venous flow, which can also be measured with echocardiography. However, given the limitations of flow velocity, direct measurement of tissue velocity can significantly improve the characterization of diastolic dysfunction. The evolution of Doppler and speckle-based methods of assessing tissue motion have vastly improved our understanding of diastolic function. With the development of simpler algorithms for categorization, and their gradual adoption by perioperative echocardiographers, LVDD should be better diagnosed and treated to improve postoperative outcomes.

Thromboembolic events early after mitral valve repair: incidence and predictive factors

BACKGROUND AND OBJECTIVES

The incidence of thromboembolic events (TE) in the early period following mitral valve repair (MV repair) is poorly documented. The aim of this prospective study was to evaluate it, and to determine predictive factors.

METHODS AND RESULTS

In this prospective multicenter non-randomized study, 350 consecutive patients were included after MV repair and monitored until post-operative day 44+/-6. 65.7% received Vitamin K antagonists (VKA), 18.8% aspirin (ASA), 5.4% ASA+VKA and 10% received no antithrombotic therapy (AT). All patients with AF received VKA or VKA+ASA. Twelve patients had a cerebral TE during follow-up:14.3% among untreated patients, 3.0% in the VKA group, and 0% in the ASA and in the ASA+VKA groups (p=0.03 for comparison no AT group versus the three other combined groups; p=NS for VKA versus ASA). In univariate analysis, only the absence of post-operative AT was related to the risk of TE (HR=6.7, CI 95%[2.1-21], p=0.0002). In a prespecified subgroup (n=185) of patients with sinus rhythm and without concomitant cardiac surgery (in which the choice of AT is not influenced by these associate conditions), only the absence of post-operative AT remained related to the risk of TE (HR=10.0, CI 95%[2.45-40], p=0.001).

CONCLUSION

In the first six weeks following MV repair, the incidence of thromboembolic events is far from negligible (3.5%), even in patients with sinus rhythm. The main predictive factor for thromboembolic event determined in this study is the absence of an antithrombotic therapy.

Evaluation of Left Atrial Size on Transoesophageal Echocardiography: What is the Best Measure?

BACKGROUND

There is no well established measurement of left atrial (LA) size on transoesophageal echocardiography (TOE). We sought to determine which measurement on TOE would best correlate with LA size obtained from transthoracic echocardiography (TTE).

METHODS

LA diameter (LAD) and volume (LAV) on TOE were compared to TTE measurements from 57 patients. The transthoracic examination was performed just prior to the TOE under 'similar clinical conditions'. LAD was obtained by M-mode and LAV was estimated by area-length method, M-mode derived LAD and the Simpson's method on TOE and compared to LAV estimated by the Simpson's method on transthoracic examination.

RESULTS

Despite LAD and LAV being underestimated on TOE, good correlations were present between LAD (r=0.85; p=0.001), area-length LAV (r=0.72; p=0.001) and Simpson's LAV (r=0.8; p=0.001). Bland Altman analysis for comparison of LAD between transoesophageal and transthoracic measurements demonstrated a mean difference of -2mm. Simpson's LAV on TOE gave the best estimation of LAV from TTE with a mean difference of -6 ml as compared to -10 ml by area-length LAV in the cohort studied.

CONCLUSION

Both left atrial diameter and volume are underestimated on TOE. The best measure with the least under-estimation of LA volume on transoesophageal examination as compared to TTE measures is obtained from Simpson's biplane estimation of LA volume.

Multi-modality imaging to assess left atrial size, anatomy and function

The left atrium (LA) anterior-posterior diameter was one of the first standardised echocardiographic parameters. However, the clinical importance of LA size assessment has been neglected for some time. Recent population-based studies have demonstrated the prognostic value of LA size for long-term outcome. Furthermore, with new dedicated techniques such as tissue Doppler imaging, it has become feasible to assess (regional) LA function. In addition, the introduction of catheter ablation procedures has changed the treatment of patients with drug-refractory atrial fibrillation (AF) dramatically. New image integration systems have become available for these catheter ablation procedures. With the use of image integration systems, a real anatomical "roadmap" of the LA is provided for catheter ablation procedures. All these factors may explain the renewed interest in LA anatomy. In this article, the importance of assessment of LA size and LA anatomy is discussed. Furthermore, the various imaging modalities that are available for the non-invasive visualisation of the LA will be reviewed. In addition, the role of these imaging techniques in catheter ablation procedures for AF will be discussed.

ORIGINAL INVESTIGATIONS: Comparison of Left Atrial Dimensions by Transesophageal and Transthoracic Echocardiography

Transesophageal echocardiography (TEE) is an established cardiovascular diagnostic technique. Left atrial (LA) size, as measured by transthoracic echocardiography (TTE), is associated with cardiovascular disease and is a risk factor for atrial fibrillation, stroke, death, and the success of cardioversion. Assessment of LA size has not been as well validated on TEE as on TTE. We determined LA size measurements in four standard views in 122 patients undergoing TEE and TTE at the same setting. In this study, we found that measurement of LA dimensions by TEE suffers from significant limitations in all views except the basal long-axis view (mid-esophageal level) with transducer plane at 120-150 degrees. This view had the best correlation with transthoracic LA measurements: r = 0.79 for TEE long axis (CI 0.71-0.85), P <.0001.

Early Exercise Training After Mitral Valve Repair

BACKGROUND

Surgical mitral valve (MV) repair is now the best technique to correct mitral regurgitation (MR). However, clinical studies have shown that without exercise training (ET), there is no significant postoperative exercise tolerance improvement. Moreover, healing duration of the MV wound is not well known; thus, the feasibility of an early ET program (ETP) may be discussed.

OBJECTIVES

To evaluate safety and feasibility of an early ETP after MV repair.

METHODS AND RESULTS

All patients hospitalized in 13 postoperative centers after MV repair from September 2002 to June 2003 were included in this prospective study. They underwent an ETP during 3 weeks on average. Transthoracic echocardiography and a cardiopulmonary exercise test were performed before and after the ETP.

PATIENTS

Two hundred fifty-one consecutive patients (male gender, 70%; mean age, 59 +/- 14 years [+/- SD]) were included 16 +/- 10 days after MV repair. There was no MR occurrence or worsening after the ETP. Left ventricular ejection fraction slightly increased (53 +/- 10% vs 55 +/- 9%, p = 0.004). Peak oxygen consumption and anaerobic threshold increased from 16.3 +/- 4.5 to 20.0 +/- 6.0 mL/kg/min (22% increase) and from 12.2 +/- 3.8 to 14.2 +/- 4.3 mL/kg/min (16% increase) respectively, (p < 0.0001).

CONCLUSION

ET after MV repair does not deteriorate the outcome of recent surgery and seems efficient.

Comparison of magnetic resonance imaging and transesophageal echocardiography in detection of thrombus in the left atrial appendage

BACKGROUND AND PURPOSE

A noninvasive technique of visualizing the left atrial appendage (LAA) and its thrombus in patients with atrial fibrillation would be of great interest. This study examined the utility of MRI for the assessment of thrombus in the LAA.

METHODS

We evaluated 50 subjects with nonrheumatic continuous atrial fibrillation and a history of cardioembolic stroke. Each patient received an MRI and a transesophageal echocardiography (TEE) on the same day for thrombus detection in the LAA. Both double- and triple-inversion recovery sequences were used for the MRI evaluations.

RESULTS

In all subjects, the LAA was readily visualized with MRI. High-intensity masses in the LAA were clearly distinguishable from the LAA wall in the triple-inversion recovery sequences. Concordance between detection of high-intensity mass with MRI and thrombus with TEE was high: no mass (MRI), no thrombus (TEE), 31 patients; mass (MRI), thrombus (TEE), 16 patients; and mass (MRI), no thrombus (TEE), 3 patients (overall kappa=0.876, SE=0.068).

CONCLUSIONS

MRI is a noninvasive and reproducible modality for thrombus detection in the LAA of patients with nonrheumatic continuous atrial fibrillation and previous cardioembolic stroke.