Differential Left Atrial Remodeling in LV Diastolic Dysfunction and Mitral Regurgitation

Association of Mitral Regurgitation with Postoperative Atrial Fibrillation in Critically Ill Noncardiac Surgery Patients: A Prospective Cohort Study

Purpose

Atrial fibrillation (AF) is common in critically ill patients and can have serious consequences. Postoperative AF (POAF) in critically ill patients following noncardiac surgery has been understudied, contrary to cardiac procedures. Mitral regurgitation (MR) is associated with left ventricular dysfunction, which might contribute to the occurrence of AF in postoperative critically ill patients. This study aimed to investigate the association between MR and POAF in critically ill noncardiac surgery patients and establish a new nomogram for the prediction of POAF in critically ill noncardiac surgery patients.

Patients and Methods

A prospective cohort of 2474 patients who underwent thoracic and general surgery was enrolled in this study. Data on preoperative transthoracic echocardiography (TTE), electrocardiogram (ECG), and several commonly utilized scoring systems (CHA2DS2-VASc, HATCH, COM-AF, HART, and C2HEST) and baseline clinical data were collected. Independent predictors were selected by univariate and multivariable logistic regression analysis, and a nomogram was constructed for POAF within 7 days after postoperative intensive care unit (ICU) admission. The ability of the MR-nomogram and other scoring systems to predict POAF was compared by receiver operator characteristic (ROC) curve analysis and decision curve analysis (DCA). Additional contributions were evaluated by integrated discrimination improvement (IDI) and net reclassification improvement (NRI) analysis.

Results

A total of 213 (8.6%) patients developed POAF within 7 days after ICU admission. Compared to CHA2DS2-VASc, HATCH, COM-AF, HART, and C2HEST scoring systems, MR-nomogram showed better predictive ability for POAF with an area under the ROC curve of 0.824 (95% confidence interval: 0.805-0.842, p < 0.001). The improvement of the MR-nomogram in predictive value was supported by NRI and IDI analysis. The net benefit of the MR nomogram was maximal in DCA.

Conclusion

MR is an independent risk factor of POAF in critically ill noncardiac surgery patients. The nomogram predicted POAF better than other scoring systems.

Importance of left atrial mechanical function as a predictor of atrial fibrillation risk following cardiac surgery

Postoperative atrial fibrillation (POAF) after cardiac surgery is a major health problem that is associated with a significant financial burden and increased early morbidity and mortality. We investigated the accuracy of new echocardiographic derived indices to predict patients at higher risk of developing POAF. 84 consecutive patients (age 57.9 ± 6.9, 32% female) hospitalized for isolated CABG underwent comprehensive echocardiographic evaluation before surgery. Left atrial (LA) function was quantified through the assessment of phasic LA volumes to calculate LATEF. Speckle tracking echocardiography STE was used to measure LA reservoir strain, conduit strain and booster strain. Patients who developed POAF had increased LA volumes and impaired LA functions assessed by both the volumetric phasic changes and STE. By univariable analysis, all LA function parameters significantly predicted POAF. Multivariate regression analysis showed that age (P = 0.03, OR 1.134, 95% CI 1.012-1.271) and LATEF (P = 0.001, OR 0.814, 95% CI 0.725-0.914) were strong independent factors for POAF with LATEF showing the highest predictive accuracy. After multivariable adjustment to include LA strain indices to the base model, LA contractile strain LACtS (23.93 ± 4.19 vs 37.0 ± 3.35, p < 0.001) was the best discriminated for the highest predictive accuracy (OR 0.429, 95% CI 0.26-0.708). The ROC Curve was calculated for the greatest performance for prediction of POAF (AUC LACtS: 0.992; LATEF: 0.899). Adding new left atrial mechanics parameters is a more sensitive, independent tool that provides an incremental predictive value to discriminate patients at more risk for POAF.

Effect of catheter ablation on pre-existing abnormalities of left atrial systolic, diastolic, and neurohormonal functions in patients with chronic heart failure and atrial fibrillation

The critical role of the left atrium (LA) in cardiovascular homoeostasis is mediated by its reservoir, conduit, systolic, and neurohormonal functions. Atrial fibrillation is generally a reflection of underlying disease of the LA, especially in patients with heart failure. Disease-related LA remodelling leads to a decline in both atrial contractility and distensibility along with an impairment in the control of neurohormonal systems that regulate intravascular volume. Catheter ablation can lead to further injury to the atrial myocardium, as evidenced by post-procedural troponin release and tissue oedema. The cardiomyocyte loss leads to replacement fibrosis, which may affect up to 30-35% of the LA wall. These alterations further impair atrial force generation and neurohormonal functions; the additional loss of atrial distensibility can lead to a 'stiff LA syndrome', and the fibrotic response predisposes to recurrence of the atrial arrhythmia. Although it intends to restore LA systole, catheter ablation often decreases the chamber's transport functions. This is particularly likely in patients with long-standing atrial fibrillation and pre-existing LA fibrosis, especially those with increased epicardial adipose tissue (e.g. patients with obesity, diabetes and/or heart failure with a preserved ejection fraction). Although the fibrotic LA in these individuals is an ideal substrate for the development of atrial fibrillation, it may be a suboptimal substrate for catheter ablation. Such patients are not likely to experience long-term restoration of sinus rhythm, and catheter ablation has the potential to worsen their haemodynamic and clinical status. Further studies in this vulnerable group of patients are needed.

Speckle tracking analysis: a new tool for left atrial function analysis in systemic hypertension: an overview

Speckle tracking echocardiography (STE) is an imaging technique applied to the analysis of left atrial function. STE provides a non-Doppler, angle-independent and objective quantification of left atrial myocardial deformation. Data regarding feasibility, accuracy and clinical applications of left atrial strain are rapidly gathering. This review describes the fundamental concepts of left atrial STE, illustrates its pathophysiological background and discusses its emerging role in systemic arterial hypertension.

Role of Left Atrial Reservoir Strain Rate in Left Atrial Remodeling in Severe Mitral Regurgitation

Background:

Impaired left atrial (LA) reservoir deformation has been found to be associated with poor functional capacity and outcomes in severe chronic mitral regurgitation (MR). Among patients with primary MR (valve incompetence due to mitral valve pathology), we focus on Carpentier II classification (prolapse or flail mitral valve) and aim to investigate determinants for decreased LA reservoir deformation and its impact on LA remodeling in severe MR.

Methods:

Among 159 consecutive patients with severe chronic Carpentier II MR (left ventricular ejection fraction ≥ 60%), 55 underwent follow-up echocardiography, which was compared with their baseline study. We used the change of LA volume index as the rapidity of LA remodeling, LA eccentricity index as LA sphericity, and peak LA reservoir strain as well as reservoir strain rate (LASR_R) derived from two-dimensional speckle-tracking echocardiography as LA reservoir function.

Results:

Older age, elongated left atrium, increased LA volume index, as well as reduced left ventricular global longitudinal strain and LA ejection fraction all linked to a poor baseline LASR_R (all p < 0.001). A second echocardiography during a mean follow-up of 15.3 ± 8.3 months revealed an enlarged left atrium (increased interval change of LA volume index; p < 0.001). In multivariate analysis, only the difference between the baseline and follow-up LASR_R values (Δ: LASR_R; odds ratio (OR) 0.037, 95% confidence interval (CI) 0.003–0.496, p = 0.013) predicted accelerated LA remodeling. A poor baseline LASR_R was significantly associated with its profound deterioration during the follow-up period (β: = -0.424, p = 0.002).

Conclusion:

In severe chronic Carpentier II MR, a reduced follow-up LASR_R predicted future accelerated LA remodeling. Patients with a poor baseline LASR_R are at a higher risk of its deterioration.

Left atrial eccentricity in chronic mitral regurgitation: relation to left atrial function

AIMS

The aim of this study was to assess the changes in the left atrial (LA) shape and to identify the determinants of these changes in chronic mitral regurgitation (MR).

METHODS AND RESULTS

We enrolled 125 consecutive patients (56 ± 16 years, 51% men) with chronic MR caused by myxomatous mitral valve disease in sinus rhythm and 45 control patients (54 ± 15 years, 55% men) undergoing transthoracic Doppler echocardiography. The LA eccentricity index (LAEi) and the LA volume index (LAVi) were used to estimate the LA shape and size, respectively. There were significant decreases in LAEi (r= -0.723, P< 0.001) and increases in LAVi (r= 0.642, P< 0.001) with increasing severity of MR. In multivariate stepwise linear regression analysis, regurgitant fraction (RF) was an independent determinant of the LAE, whereas RF, left ventricular (LV) mass index and LV diastolic dysfunction grade were independent determinants of the LA volume. The LAEi was positively related to the velocity of A' in the entire population (r = 0.238, P = 0.002). On the receiver operating characteristic (ROC) curve analysis, LAEi ≤1.30 was the best cut-off value to reflect the LA systolic dysfunction (A' velocity <7 cm/s; area under the curve was 0.78, P < 0.001).

CONCLUSION

LA becomes more spherical with increasing severity of MR, suggesting a decrease in LAE, which is mainly determined by the volume overload. LAE might be closely related to the LA systolic function in chronic MR.

Left atrial flow propagation velocity: a new approach for assessment of left atrial reservoir function

To assess the feasibility of left atrial flow propagation velocity (LAFPV) measurement and to evaluate the influence of preload alterations on this new parameter of left atrial (LA) reservoir function as compared to conventional echocardiographic indices. 30 healthy volunteers (26 ± 5 years, 20 males) underwent echocardiographic examination at rest, during passive leg lifting and after sublingual administration of nitroglycerine with subsequent Valsalva maneuver. LA reservoir function was assessed by conventional indices including LA expansion index, peak velocity and velocity-time integral of pulmonary venous systolic flow. As well, LAFPV was measured by color M-mode in an apical 4-chamber view as the slope of the transatrial flow wave during LA reservoir phase. LAFPV measurement was feasible in 25 subjects (83%). All conventional parameters of LA reservoir function were significantly altered from resting values by both load-modifying conditions. However, LAPFV was not significantly altered by such maneuvers (228 ± 28 cm s⁻¹ at rest vs. 238 ± 3 cm s⁻¹ during leg lifting, P = NS, vs. 218 ± 38 cm s(-1) after nitroglycerin with Valsalva maneuver, P = NS vs. rest, P < 0.01 vs. leg lifting). LAFPV can be measured in a majority of subjects and represents a new, less load-dependent index of LA reservoir function that may more appropriately reflect LA compliance.