Multislice Computed Tomography Accurately Quantifies Left Atrial Size and Function After the MAZE Procedure

A fast and reproducible method to estimate left atrial volume using cardiac computed tomography

PURPOSE

The purpose of this study was to do better than the simple maximal axial area (MArea_ax) and to validate simple, fast and robust orthogonal methods for determining the left atrium volume (LAV) with cardiac CT (CCT).

MATERIAL AND METHODS

A total of 60 patients who underwent CTT were retrospectively included. There were 30 men and 30 women with a mean age of 59±12 (SD) years (range: 27-80 years), using four methods to assess LAV beyond the MArea_ax: two orthogonal methods requiring the measurements of axial, coronal and sagittal planes of 3 diameters LAV_3diam or 3 area LAV_3Areas; Area-length biplane method LAV_biplane; and volumetric method LAV_volumetric using a semi-automated tool that served as the reference standard. The orthogonal methods were applied on contrast-enhanced (IV+) and unenhanced (IV-) CCT images. Comparisons were performed using Pearson correlation test (r) and Bland-Altman analysis. Inter- and intra-observer variability were assessed using intraclass correlation coefficient (ICC) with a two-way mixed-effects model.

RESULTS

On IV+ CCT, LAV_biplane, LAV3diam_-IV+, LAV_3Areas-IV+ underestimated LAV (-15±1.99mL; -21±1.37mL; -15±1.98mL; all P<0.001). LAV_3diam-IV+, LAV3_Areas-IV+ better correlated with reference standard (r=0.97 and 0.98) than LAV_biplane (r=0.79) as well as MArea_ax (r=0.90). Estimating LAV on IV- further showed high correlation against the reference (r=0.93 and 0.95 for LAV3diam_-IV- and LAV_3Areass-IV-, respectively). Intra- and inter-observer ICC increased from LAV_volumetric (2.43% and 3.09%); LAV_3Areas-IV+ (3.04 and 3.30%); LAV_3Areas-IV-(3.34 and 4.23%), LAV3diam_-IV+ (3.36 and 5.11%); LAV3diam_-IV- (5.16 and 6.90%); to LAV_biplane (9.65 and 10.28%).

CONCLUSIONS

Better than MArea_ax, orthogonal methods using either diameter or surface are fast and reproducible methods to assess LAV on CCT when performed with or without intravenous administration of contrast material.

Long-term results of the maze procedure with GP ablation for permanent atrial fibrillation

OBJECTIVES

We investigated the effect of the maze procedure with intensive pulmonary vein isolation (PVI) guided by ganglionated plexus (GP) mapping (the Maze with GP ablation group) on a long-term postoperative maintenance of sinus rhythm in patients with permanent atrial fibrillation (AF) and compared with that in patients undergoing the maze procedure with the conventional PVI (the Maze group).

METHODS AND RESULTS

We investigated 48 patients who underwent the maze procedure with GP ablation for persistent AF and 43 patients who underwent the maze procedure. The Maze procedure was conducted by the endocardial application of bipolar radiofrequency ablation and cryoablation. Conventional PVI was applied three times for the entrance of right and left PVs, respectively. Intensive PVI for GP ablation was repeated six-to-eight times for both sides of PVs to cover the bilateral GP regions identified by GP mapping. The duration of permanent AF, the prevalence of concomitant primary heart diseases, and the postoperative follow-up period were comparable between the two groups. At discharge, 1 year, 5 years after the surgery, sinus rhythm was maintained in 74.4%, 61%, and 40.5% of the Maze group. In contrast, it was maintained in 93.7%, 88.9%, and 75.7% of the Maze with GP ablation group. The cumulative freedom rate from AF at 10 years after surgery was significantly higher in the Maze with GP ablation group.

CONCLUSIONS

More intense PV isolation including adjacent GP may improve long-term results of maze procedure in patients with permanent AF.

Left atrio-vertebral ratio: A new computed-tomography measurement to identify left atrial dilation

BACKGROUND

Left cardiac chambers dilation, interstitial lung changes and pleural effusions are the characteristics of cardiogenic pulmonary oedema on computed tomography (CT) of the chest but mensuration of the left atrial size is not routinely performed. Cardiac chambers normal dimensions are known to be proportional to the patient's build and anthropomorphic data but adjustment of chambers dimensions to available elements seen on the axial CT images has never been evaluated before.

OBJECTIVES

Our objective was to use data easily available on axial images to directly scale the left atrium. We chose to divide the left atrial diameter by the thoracic vertebral diameter, using the latter as a body-mass indicator. As a preliminary study, we aimed to evaluate the range of values of this left atrio-vertebral ratio (LAVR) by comparing patients suffering from cardiogenic pulmonary oedema with patients free of cardiac disease. We hypothesized that if the difference of values in these two populations of patients was significant enough, this ratio would be relevant and could be used as a quick criterion in different clinical situations.

METHOD

Two radiologists reviewed CT scans of 32 of patients free of cardiac disease and 40 patients in acute cardiac failure. The maximum diameter of the left atrium at the level of the right inferior pulmonary vein was divided by the vertebral transverse diameter to generate a left atrio-vertebral ratio. Receiver operating characteristic curves identified the threshold associated with pulmonary oedema.

MEASUREMENTS AND MAIN RESULTS

The mean LAVR was 1.85 ± 0.27 in asymptomatic patients and 2.48 ± 0.35 in patients with pulmonary oedema. A LAVR of 2.1 yielded 85% sensitivity and 88% specificity for the diagnosis of cardiogenic pulmonary oedema.

CONCLUSIONS

LAVR is a simple new measure directly scaling the left atrial diameter to the anthropomorphic characteristics of the patient. In our series, a ratio above 2.1 is strongly associated with cardiogenic pulmonary oedema indirectly suggesting left atrial dilation. The results were significantly different between the two populations of patients (no heart condition versus cardiogenic pulmonary oedema) suggesting a high potential for clinical application.

Adjusted left atrial emptying fraction as a predictor of procedural outcome after catheter ablation for atrial fibrillation

Structural remodeling of the left atrium is a risk factor for recurrent arrhythmia after catheter ablation for atrial fibrillation; however, data are sparse regarding the role of functional left atrial remodeling in predicting procedural outcomes. We evaluated whether left atrial transport function could be used to predict recurrent atrial fibrillation. From July 2008 through August 2010, we enrolled 202 consecutive patients who underwent catheter ablation for atrial fibrillation (paroxysmal=120, persistent=82). Left atrial volumes (LAVs) were measured by means of multislice computed tomography at every 10% of the R-R interval, and measurements were adjusted for body surface area to yield the LAV index (LAVI) at baseline. The left atrial emptying fraction (LAEF) was calculated according to LAV differences. During the mean follow-up period of 10 ± 4 months after a single ablation procedure, atrial fibrillation recurred in 59 patients (paroxysmal=19, persistent=40). Multivariate analysis revealed that persistent atrial fibrillation, early mitral inflow velocity, LAVImax, LAVImin, LAEF, LAVImax/LAEF, and LAVImin/LAEF were all independent predictors of atrial fibrillation, but the best predictor was LAVImin/LAEF (β=1.329, P=0.001). The cutoff value was 1.61 (mL/m(2))/%, and the sensitivity and specificity were 74.6% and 62.2%, respectively (area under the curve=0.761). Our study shows that adjusted left atrial emptying fraction with use of multislice computed tomography might be a useful, noninvasive method to select patients for ablation.

Left atrial function following surgical ablation of atrial fibrillation: prospective evaluation using dual-source cardiac computed tomography

PURPOSE

The Maze procedure has shown excellent efficacy in the elimination of atrial fibrillation (AF); however, little is known about the quality of functional recovery in the left atrium (LA) following successful sinus rhythm conversion by the Maze procedure.

MATERIALS AND METHODS

We prospectively enrolled 12 patients (aged 52.5±10.1 years, 1 female) with valvular AF undergoing mitral valve surgery combined with the Maze procedure. Parameters of LA function in three anatomic compartments [anterior, posterior, and LA appendage (LAA)] were evaluated using electrocardiography-gated dual-source cardiac CT at one month and at six months after surgery. Twelve subjects matched by age, gender, and body surface area served as controls.

RESULTS

At one month after surgery, ejection fraction (EF) and emptying volume (EV) of the LA were 14.9±7.4% and 21.3±9.7 mL, respectively, and they were significantly lower than those of the control group (EF, 47.9±11.2%; EV, 46.0±10.7%; p<0001). These values did not significantly change throughout late periods (p=0.22 and 0.21, respectively). Functional contributions of the anterior, posterior, and appendage compartments (EV of each compartment/overall EV) were 80.4%, -0.9%, and 20.5%, respectively, for those with LAA preservation (n=6); 100.1%, -0.1%, and 0% for those with LAA resection (n=6; p<0.05); and 62.2%, 28.2%, and 9.7% in the control subjects (p<0.001).

CONCLUSION

Contractile functions of the LA significantly decreased after the Maze procedure. Functional contributions of three compartments of the LA were also altered. The influence of LAA preservation on postoperative LA functions needs to be evaluated through studies of larger populations.

Quantification of the functional consequences of atrial fibrillation and surgical ablation on the left atrium using cardiac magnetic resonance imaging

OBJECTIVES

The effect of atrial fibrillation (AF) on left atrial (LA) function has not been well defined and has been largely based on limited echocardiographic evaluation. This study examined the effect of AF and a subsequent Cox-Maze IV (CMIV) procedure on atrial function.

METHODS

Cardiac magnetic resonance imaging (cMRI) was performed in 20 healthy volunteers, 8 patients with paroxysmal atrial fibrillation (PAF) and 7 patients with persistent or long-standing persistent atrial fibrillation (LSP AF). Six of the PAF patients underwent surgical ablation with the CMIV procedure and 5 underwent both pre- and postoperative cMRIs. The persistent or LSP AF patients underwent only postoperative cMRIs because all scans were performed with patients in normal sinus rhythm. Volume-time curves throughout the cardiac cycle and regional wall shortening were evaluated using the cine images and compared across groups.

RESULTS

Compared with normal volunteers, patients with PAF had significantly decreased reservoir contribution to left ventricular (LV) filling (P = 0.0010), an increased conduit function contribution (P = 0.04) and preserved booster pump function (P = 0.14). Following the CMIV procedure, significant reductions were noted with respect to reservoir and booster pump function, with corresponding increases in conduit function. These differences were more drastic in patients with persistent/LSP AF. Regional wall motion was significantly reduced by PAF in all wall segments (P < 0.05), but was not further reduced by the CMIV. Despite changes in LA function, LV function was preserved following surgery.

CONCLUSIONS

PAF significantly altered LA function and has a detrimental effect on regional wall motion. Surgical intervention further altered LA function, but the reasons for this are likely multifactorial and not entirely related to the lesion set itself.

Assessment of the structural remodeling of the left atrium by 64-multislice cardiac CT: comparative studies in controls and patients with atrial fibrillation

BACKGROUND

To assess the functional differences among the three anatomic compartments of the left atrium (LA) using 64-multislice cardiac CT in controls and patients with atrial fibrillation (AF).

METHODS

We examined 144 individuals (105 males, mean age 56.42 ± 12.04 years) undergoing 64-multislice cardiac CT and divided them into 48 control, 53 paroxysmal AF (PAF), and 43 persistent AF (PeAF) patients. The LA was divided into three anatomic compartments according to their embryologic origins: venous LA (VLA), anterior LA (ALA), and LA appendage (LAA). Each volume was calculated using a threshold-based, three-dimensional segmentation. The LA parameters were defined as maximum and minimum LA volume indices, emptying volume, and ejection fraction. We compared the LA parameters of each compartment in controls, PAF patients, and PeAF patients.

RESULTS

In each of the three LA compartments, the maximum LA volume index was lowest in controls (LAA, 4.8 ml/m(2); VLA, 18.3 ml/m(2); ALA, 37.1 ml/m(2)) and highest in PeAF patients (LAA, 9.8 ml/m(2); VLA, 30.0 ml/m(2); ALA, 67.3 ml/m(2)). Regarding the three LA compartments, the ejection fraction was highest in the LAA and lowest in the VLA in controls (LAA, 58.3%; VLA, 29.0%; ALA, 47.4%) and in PAF patients (LAA, 47.3%; VLA, 18.3%; ALA, 39.2%). In PeAF patients, the emptying volumes and ejection fractions of the VLA were approximately zero.

CONCLUSIONS

The anatomic compartments of the LA play different roles in AF patients. The LAA has both highest contractility and independent function, and the VLA is the most severely affected by LA dysfunction. Our results may be helpful in understanding the pathophysiology of AF and predicting treatment responses to radiofrequency ablation in the future.

Meta-analysis of the effect of radiofrequency catheter ablation on left atrial size, volumes and function in patients with atrial fibrillation

The effects of radiofrequency catheter ablation (RFCA) on left atrial (LA) size, volumes, and function in patients with atrial fibrillation (AF) are not well understood. The aim of this study was to systematically review the effects of RFCA on LA size, volumes, and function in patients with AF. Medline, the Web of Science, the Cochrane Central Register of Controlled Trials, and the reference lists of retrieved reports were searched for relevant studies through April 2009. Studies conducted in patients with AF were included if their primary outcomes were changes in LA size or volumes and/or function before and after RFCA. Weighted mean differences for changes in LA diameter, LA maximum volume, LA minimum volume, LA ejection fraction, and LA active emptying fraction were estimated using fixed- and random-effects meta-analyses. Seventeen relevant studies (enrolling 869 patients) among 192 identified studies were included in the final analysis. Compared to preablation values, there were significant decreases in LA diameter and LA volumes at postablation follow-up. However, compared to preablation values, there were no significant differences in LA ejection fraction and LA active emptying fraction at postablation follow-up. Decreases in LA diameter and LA volumes remained significant in those without AF recurrence but not in those with AF recurrence. LA ejection fraction and LA active emptying fraction did not decrease in patients without AF recurrence, whereas they decreased in patients with AF recurrence. In conclusion, successful RFCA in patients with AF significantly decreases LA size and volumes and does not seem to adversely affect LA function.

Assessment of left atrial volume and mechanical function in ischemic heart disease: a multi slice computed tomography study

Left atrial (LA) maximal volume contains prognostic information in patients with heart failure and acute myocardial infarction. However, only few studies have investigated the detailed mechanical function of the LA in these patients. We assessed the feasibility of evaluating LA volume and mechanical function with Multi Slice Computed Tomography (MSCT) in patients with ischemic heart disease. Furthermore, the LA and left ventricular (LV) function was evaluated in relation to signs of clinical heart failure.

METHODS AND RESULTS

MSCT was performed in 40 patients with sinus rhythm and ischemic heart disease. We enrolled 20 patients with reduced LV ejection fraction (LVEF≤45%) and 20 with preserved LVEF (>45%). LA volumes, reservoir, channel and pump function were measured. Interobserver variation for LA volume measures was 1.5% (SD: 6.6%). In patients with reduced LVEF, LA volumes were larger throughout the cardiac cycle (LA-max 66.8 ml/m(2) vs 57.4 ml/m(2) and LA-min: 45.8 ml/m(2) vs 31.6 ml/m(2), p<0.05) and LA reservoir and pump function were all significantly impaired (Fractional change: 43% vs 31%, LAEF 31% vs 19%, p<0.05). Patients with clinical signs of heart failure during hospitalisation had significantly lower LAEF than patients without (16(9)% vs. 30(17)% p<0.05). In a multivariate linear regression analyses the presence of clinical signs of heart failure and reduced LVEF were independent determinants of impaired LA reservoir and pump function (p<0.05).

CONCLUSION

Reproducible assessment of LA size and mechanical function throughout the cardiac cycle using MSCT is feasible and potentially useful clinically.

Does left atrial volume and pulmonary venous anatomy predict the outcome of catheter ablation of atrial fibrillation?

INTRODUCTION

Preprocedural factors may be helpful in selecting patients with atrial fibrillation (AF) for treatment with catheter ablation and in making an assumption regarding their prognosis. The aims of this study were to investigate whether left atrial (LA) volume and pulmonary venous (PV) anatomy, evaluated by computed tomography (CT) prior to ablation, will predict AF recurrence following catheter ablation.

METHODS AND RESULTS

We included 146 patients (mean age 57 +/- 11 years, 83% male) with symptomatic AF (55% paroxysmal, 18% persistent, 27% long-standing persistent). All patients underwent CT scanning prior to catheter ablation to evaluate LA volume and PV anatomy. Circumferential PV isolation was performed guided by Cartomerge electroanatomical mapping. The outcome was defined as complete success, improvement, or failure. After a mean follow-up of 19 +/-7 months, complete success was achieved in 59 patients (40%), and 38 patients (26%) demonstrated improvement. LA volume was found to be an independent predictor of AF recurrence with an adjusted OR of 1.14 for every 10-mL increase in volume (95% CI 1.00-1.29, P = 0.047). PV variations were equally distributed among the different outcomes of the ablation procedure, and therefore univariate analysis did not identify PV anatomy as a predictor of outcome.

CONCLUSION

LA volume is an independent predictor of AF recurrence after catheter ablation. Additionally, PV anatomy did not have any effect on the outcome. These findings suggest that an assessment of LA volume may be incorporated into the preprocedural evaluation of patients being considered for AF ablation.

Evaluation of the Pulmonary Veins and Left Atrial Volume using Multidetector Computed Tomography in Patients Undergoing Catheter Ablation for Atrial Fibrillation

Catheter ablation is an evolving treatment option in patients with atrial fibrillation. Contrast enhanced electrocardiogram-gated multi-detector computed tomography (MDCT) has rapidly evolved over the past few years into an important tool in the diagnosis of coronary atherosclerosis. There is increasing recognition that MDCT is a useful tool to evaluate non-coronary structures, such as cardiac chambers, valves, the coronary sinus and adjacent structures including pulmonary veins. In particular, MDCT is playing an increasingly important role in the evaluation of the left atrium and the pulmonary veins in patients undergoing catheter ablation for atrial fibrillation. It provides accurate and reliable identification of the pulmonary veins and anatomical relationship between the left atrium and esophagus although the mobile esophagus may limit the value of MDCT to reduce the risk of atrio-esophagus fistula. In this article, we will review the evaluation of the left atrium and pulmonary veins using MDCT in patients undergoing catheter ablation of atrial fibrillation.

Validation of a simplified method to determine left atrial volume by computed tomography in patients with atrial fibrillation

The success of catheter ablation of atrial fibrillation (AF) is highly dependent on a preprocedural assessment of the size and shape of the left atrium. The most precise method to determine left atrial (LA) volume using computed tomography requires manually tracing the LA area of each cross-sectional image. This is a labor-intensive and time-consuming technique. The purpose of this study was to compare LA volume derived using the "gold-standard" multiple-slice technique with LA volume estimated using 3 orthogonal LA dimensions in patients with AF. The patient population was composed of 100 patients referred for catheter ablation of AF (87 men, mean age 57 +/- 12 years). AF was paroxysmal in 49 patients and persistent in 51. Each patient underwent computed tomography before catheter ablation, and LA volume was measured using the 2 methods. The mean LA volume measured using the multiple-slice technique was 136 +/- 46 ml. According to the simpler estimation approach, the mean LA volume was 112 +/- 41 ml. A close correlation was noted between atrial volumes determined using the 2 methods (r = 0.91, p <0.001). There was a mean underestimation of LA volume by the estimation technique of 17 +/- 13%. In conclusion, the results of this study reveal that LA volume determined using an estimation approach correlates closely with true LA volume as determined using the gold-standard multiple-slice approach. This estimation approach underestimates true LA volume by approximately 20%.

Left atrial contractility is preserved after successful circumferential pulmonary vein ablation in patients with atrial fibrillation

INTRODUCTION

Circumferential pulmonary vein ablation (CPVA) for atrial fibrillation (AF) consists of creating extensive lesions in the left atrium (LA). The aim of the study was to evaluate changes in LA contractility after ablation and their relationship with procedure outcome.

METHODS AND RESULTS

A series of 90 consecutive patients underwent cardiac magnetic resonance imaging (MRI) before and 4-6 months after CPVA. Only patients in sinus rhythm during both imaging acquisitions were included in the study to measure LA end-diastolic (LAmax) and LA end-systolic (LAmin) volumes. Fifty-five patients were finally analyzed (41 men, 52 +/- 11 years, 74% paroxysmal AF). During a mean follow-up of 12 +/- 7 months and after 1.2 +/- 0.3 ablation procedures, 38 patients (69%) were arrhythmia-free (group I), and the remaining 17 patients had recurrences (group II). There was a significant decrease in mean LAmax volume in both groups, whereas mean LAmin volume only decreased in group I. Mean LA ejection fraction (EF) was preserved after CPVA in group I (40 +/- 11% vs 38 +/- 10%; P = 0.27) but decreased in patients with arrhythmia recurrences (37 +/- 10% vs 27 +/- 10%; P < 0.001). In fact, LA EF remained stable or increased in 68% of patients without arrhythmia recurrences.

CONCLUSIONS

LAmax volume reduction following CPVA occurs regardless of the clinical efficacy of the procedure, whereas mean LAmin volume only decreased in patients without recurrences. LA EF was preserved or even increased in most patients with successful CPVA.

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.

Atrial function after ablation procedure in patients with chronic atrial fibrillation using steady-state free precession magnetic resonance imaging

BACKGROUND

Surgical ablation procedures are an established surgical procedure for restoration of sinus rhythm and reestablishment of atrial function in patients with chronic atrial fibrillation. The purpose of this study was to evaluate the feasibility and reproducibility of steady-state free precession magnetic resonance imaging (SSFP MRI) for examination of atrial dimensions and function after ablation procedures.

METHODS

Nineteen patients (mean age, 63.1 +/- 11.7 years) being at least six months after surgical ablation procedure, with stable sinus rhythm, were selected for the study. They underwent cardiac MRI. End-diastolic and end-systolic volumes were measured using Simpson's rule. The presence of visual contraction was visually assessed.

RESULTS

In MRI evaluation mean end-diastolic volume of the right atrium and left atrium after an ablation procedure was 127 +/- 45 mL and 163 +/- 50 mL, respectively. Mean stroke volume was 23 +/- 15 mL and 26 +/- 12 mL for the right and left atrium. Mean ejection fraction of the right atrium was 0.19 +/- 0.14 and 0.17 +/- 0.1 for the left atrium. An atrial kick of both atria was observed in 8 of 19 (47%) patients. An atrial kick of only the right atrium was observed in an additional 13 of 19 (68%) patients.

CONCLUSIONS

The anticipated events after a surgical ablation procedure are the restoration of atrial contractility and the associated atrial kick, thereby enhancing cardiac output and decreasing the risk of thromboembolism. Evaluation of atrial function after an ablation procedure using SSFP MRI is feasible and allows a standardized documentation of postoperative atrial function, thus allowing evaluation of the surgical outcome in a reproducible way. Echocardiographic evaluation seems to underestimate the transport function of the atrium.