Patterns of left atrial activation and evaluation of atrial dyssynchrony in patients with atrial fibrillation and normal controls: Factors beyond the left atrial dimensions

Association between sick sinus syndrome and atrial fibrillation: A systematic review and meta-analysis

AIMS

Sick sinus syndrome (SSS) and atrial fibrillation (AF) frequently coexist and show a bidirectional relationship. This systematic review and meta-analysis aimed to decipher the precise relationship between SSS and AF, further exploring and comparing different therapy strategies on the occurrence or progression of AF in patients with SSS.

METHODS AND RESULTS

A systematic literature search was conducted until November 2022. A total of 35 articles with 37,550 patients were included. Patients with SSS were associated with new-onset AF compared to those without SSS. Catheter ablation was associated with a lower risk of AF recurrence, AF progression, all-cause mortality, stroke and hospitalization of heart failure compared to pacemaker therapy. Regarding the different pacing strategies for SSS, VVI/VVIR has higher risk of new-onset AF than DDD/DDDR. No significant difference was found between AAI/AAIR and DDD/DDDR, as well as between DDD/DDDR and minimal ventricular pacing (MVP) for AF recurrence. AAI/AAIR was associated with higher risk of all-cause mortality when compared to DDD/DDDR, but lower risk of cardiac death when compared to DDD/DDDR. Right atrial septum pacing was associated with a similar risk of new-onset AF or AF recurrence compared to right atrial appendage pacing.

CONCLUSION

SSS is associated with a higher risk of AF. For patients with both SSS and AF, catheter ablation should be considered. This meta-analysis re-emphasizes that high percentage of ventricular pacing should be avoided in patients with SSS in order to decrease AF burden and mortality.

P-wave duration and atrial fibrillation recurrence after catheter ablation: a systematic review and meta-analysis

AIMS

Atrial fibrillation (AF) is a global health problem with high morbidity and mortality. Catheter ablation (CA) can reduce AF burden and symptoms, but AF recurrence (AFr) remains an issue. Simple AFr predictors like P-wave duration (PWD) could help improve AF therapy. This updated meta-analysis reviews the increasing evidence for the association of AFr with PWD and offers practical implications.

METHODS AND RESULTS

Publication databases were systematically searched and cohort studies reporting PWD and/or morphology at baseline and AFr after CA were included. Advanced interatrial block (aIAB) was defined as PWD ≥ 120 ms and biphasic morphology in inferior leads. Random-effects analysis was performed using the Review Manager 5.3 and R programs after study selection, quality assessment, and data extraction, to report odds ratio (OR) and confidence intervals. : Among 4175 patients in 22 studies, 1138 (27%) experienced AFr. Patients with AFr had longer PWD with a mean pooled difference of 7.8 ms (19 studies, P < 0.001). Pooled OR was 2.04 (1.16-3.58) for PWD > 120 ms (13 studies, P = 0.01), 2.42 (1.12-5.21) for PWD > 140 ms (2 studies, P = 0.02), 3.97 (1.79-8.85) for aIAB (5 studies, P < 0.001), and 10.89 (4.53-26.15) for PWD > 150 ms (4 studies, P < 0.001). There was significant heterogeneity but no publication bias detected.

CONCLUSION

P-wave duration is an independent predictor for AF recurrence after left atrium ablation. The AFr risk is increasing exponentially with PWD prolongation. This could facilitate risk stratification by identifying high-risk patients (aIAB, PWD > 150 ms) and adjusting follow up or interventions.

Bachmann bundle impairment following linear ablation of left anterior wall: impact on left atrial function

We aimed to evaluate the effect of Bachmann bundle (BB) impairment on electrical and mechanical function of the left atrium (LA), as well as the long-term clinical impact of such impairment. We measured activation time in the five LA walls in 56 patients with atrial fibrillation. LA reservoir, conduit, and contractile function were also evaluated. Patients were divided into two groups based on ablation strategy: the circumferential pulmonary vein isolation (CPVI) group and CPVI with LA anterior wall linear ablation (LAAW) group. Patients in the CPVI + LAAW group were divided into two sub-groups based on ECG differences following ablation: the BB impairment group and intact BB group. LA activation time and function were then compared between the ablation strategy groups and the CPVI + LAAW subgroups. Patients in the CPVI + LAAW group exhibited longer activation times in the anterior and lateral walls of the LA, poorer LA synchrony, and reduced LA contractile and reservoir function when compared with those in the CPVI group. In the BB impairment subgroup, we observed a discrepancy between electrical/mechanical remodeling. Among five walls, activation time was longest in this region. BB impairment was also associated with reduced LA function. Significant changes in LA function and conductibility were observed in patients with anterior wall ablation, especially those with iatrogenic BB impairment.

Atrial remodeling and atrial fibrillation recurrence after catheter ablation : Past, present, and future developments

The term "atrial remodeling" is used to describe the electrical, mechanical, and structural changes associated with the presence of an arrhythmogenic substrate for atrial fibrillation. Rhythm control therapy may slow down or even reverse progressive atrial remodeling. Atrial remodeling has long been recognized as an important predictor of clinical outcomes and therapeutic success, but recent advances have highlighted its clinical relevance and revealed the implications of specific anatomical changes such as atrial asymmetry or shape. This has opened the path to computational precision medicine that captures these data in detail and combines them with other factors, to provide patient-specific solutions. The goal of precision medicine lies in improving clinical outcomes, reducing costs, and avoiding unnecessary procedures. In this article, we review the history of atrial remodeling and we summarize the insights from our research on anatomical atrial remodeling and its association with rhythm outcomes after catheter ablation. Finally, we present recent advances in the field, reflecting the beginning of a new technological era that will enable us to improve patient care by personalized patient-specific medicine.

Clinical review of sick sinus syndrome and atrial fibrillation

Sick sinus syndrome (SSS) is a set of diseases with abnormal cardiac pacing, which manifests as diverse cardiac arrhythmias, especially bradycardia. The clinical presentation is inconspicuous in the early stage, but with the progression of this disease, patients may present with symptoms and signs of end-organ hypoperfusion. As a common result in the natural history of the disease, SSS coexisting with atrial fibrillation (AF) forms the basis of bradycardia-tachycardia syndrome. Age-related interstitial fibrosis is considered to be the common pathophysiological mechanism between SSS and AF. The combination of these diseases will adversely affect the condition of patients and the efficiency of subsequent treatment. Although the exact mechanism is not clear to date, the extensive structural and electrical remodeling of the atrium are considered to be the important mechanism for the occurrence of AF in patients with SSS. Pacemaker implantation is the first-line treatment for symptomatic patients with SSS and documented bradycardia history. In view of the adverse effects of AF on the treatment of SSS, researchers have focused on evaluating different pacing modes and algorithms to reduce the risk of AF during pacing. Catheter ablation may also be used as an alternative second-line therapy for some patients with SSS and AF.

Abnormal pattern of left atrial activation and asynchronous conduction predicted the occurrence of new atrial fibrillation: evidences for Bachmann's bundle block in atrial fibrillation pathophysiology

AIMS

Evidences suggest that recurrent atrial fibrillation (AF) is associated with left atrial (LA) remodelling. The goal of this study is to establish a method for assessment of LA remodelling and find predictors for the development of AF.

METHODS AND RESULTS

This prospective study included patients without a history of AF who were evaluated using pulsed-wave tissue Doppler imaging (PW-TDI). P-wave onset to A'-wave (PA' interval) was measured at the septal, lateral, anterior, and inferior mitral annulus. Abnormal LA activation pattern was defined as an upward LA activation over the coronary sinus and delayed activation anterior. Left atrial asynchrony was measured as (i) the difference between the septal and lateral PA' interval (DLS) and (ii) the standard deviation of all four PA' intervals (SD4-PA'). The follow-up for AF recurrence (AF+) was based on symptoms and 7-day Holter electrocardiograms. Ninety-eight patients (mean age 58 ± 15 years, 47% female) were included. During a follow-up of 28 ± 9 months, AF was documented in 10%. More pronounced LA asynchrony was observed in AF+ group: DLS (AF+) 39 ± 16 vs. DLS (AF-) 20 ± 11 ms; P < 0.001, and SD4-PA' (AF+) 18.6 ± 6.4 vs. SD4-PA' (AF-) 11.7 ± 4.2 ms; P < 0.001. Abnormal LA activation was frequently observed in AF+ patients: 60% vs. 27%; P = 0.033. Electrocardiogram sign of Bachmann's bundle block (BBB) was associated with prolongation of SD4-PA': SD4-PA' (BBB+) vs. SD4-PA' (BBB-) = 18 ± 6 vs. 13 ± 4.5 ms; P = 0.007.

CONCLUSIONS

More pronounced LA asynchrony and abnormal LA activation pattern were associated with new-onset AF.

Atrial conduction time associated predictors of recurrent atrial fibrillation

Identifying patients at high risk of atrial fibrillation (AF) recurrence remains challenging. This study aimed to evaluate total atrial conduction time (TACT) and left atrial (LA) asynchrony as predictors of AF recurrence. Consecutive patients after the first AF episode, terminated either spontaneously or with cardioversion, underwent transthoracic echocardiography. TACT, estimated by the time delay between the onset of P-wave and the peak A'-wave on the Tissue Doppler Imaging (PA-TDI duration), atrial volumetric and functional parameters, and biatrial strain were assessed. We calculated mean PA-TDI-the average of PA-TDI measurements in all left atrial (LA) walls-and the difference between the longest and the shortest PA interval (DLS) and the standard deviation of 4 PA intervals (SD4) to assess the LA global remodeling and asynchrony, respectively. The primary endpoint was AF recurrence. Patients with recurrent AF had significantly prolonged PA-TDI intervals in each LA wall-and thus mean PA-TDI-than those without recurrence (mean PA-TDI: 157.4 ± 17.9 vs. 110.2 ± 7.7 ms, p < 0.001). At univariate analysis, LA maximum volume index, total LA emptying fraction, right atrial maximum volume index, PA-TDI, DLS, and SD4 were predictors of AF recurrence. At multivariable analysis, PA-TDI intervals in all LA walls remained strong predictors with mean PA-TDI (odds ratio 1.04; 95% confidence interval 1.03-1.06) having an optimal cutoff of 125.8 ms in receiver operator characteristics curve analysis providing 98% sensitivity and 100% specificity for AF recurrence (area under the curve = 0.989). PA-TDI was an independent predictor of AF recurrence and outperformed established echocardiographic parameters.

Multimodality imaging for atrial fibrosis detection in the era of precision medicine

In recent years, atrial fibrillation (AF) has increasingly become a focus of attention because it represents the most encountered arrhythmia in clinical practice and a major cause of morbidity and mortality. Issues underlying AF have long been debated; nevertheless, electrical, contractile, and structural remodeling is demonstrated to be the pivotal contributor to arrhythmic substrate. Fibrosis is a hallmark of arrhythmogenic structural remodeling, resulting from an accumulation of fibrillar collagen deposits, as a reparative process to replace degenerating myocardium with concomitant reactive fibrosis, which causes interstitial expansion. Although the precise role of fibrosis in AF initiation and maintenance remains to be fully elucidated, a better definition of its extent and distribution may assist in designing individually tailored ablation approaches and improving procedure outcomes by targeting the fibrotic substrates with an organized strategy employing imaging resources. A deep comprehension of the mechanisms underlying atrial fibrosis could be crucial to setting up improved strategies for preventing AF-promoting structural remodeling. Imaging modalities such as echocardiography, cardiac computed tomography, and cardiac magnetic resonance, combined sometimes with invasive electroanatomical mapping, could provide valuable information for the optimal patients’ management if their use is not limited to cardiac anatomy study but extended to characterize abnormal left atrial substrate. Although pulmonary vein isolation is usually efficacious in treating paroxysmal AF, it is not sufficient for many patients with nonparoxysmal arrhythmias, particularly those with longstanding persistent AF. Noninvasive imaging techniques play a pivotal role in the planning of arrhythmic substrates ablation and show a strong correlation with electro-anatomic mapping, whose novel multipolar mapping catheters allow nowadays a more precise comprehension of atrial substrate. This review aims to explore the impact of the various imaging modalities for the detection of atrial fibrosis and their role in the management of AF.

Left atrial activation and asymmetric anatomical remodeling in patients with atrial fibrillation: The relation between anatomy and function

BACKGROUND

Identifying patients with advanced left atrial (LA) remodeling before catheter ablation (CA) of atrial fibrillation (AF) is crucial.

HYPOTHESIS

This study aimed to identify echocardiographic parameters associated with changes in anatomy and conduction properties of the left atrium (LA).

METHODS

We examined 75 AF patients prior to CA and measured the intervals from the P-wave-onset to four mitral annulus sites by pulsed-wave tissue Doppler imaging (PW-TDI). Patients were grouped to an upward U-pattern (delayed anterior activation) and a downward D-pattern (earliest LA activation anterior). CT-data were used to measure the LA volume (LAV). LAV was divided into anterior- (LA-A) and posterior-parts by a plane, parallel to the posterior wall and between the veins and the appendage, to calculate the asymmetry index (ASI = LA-A/LAV).

RESULTS

Patients with U-pattern (n = 66) had a higher ASI (65 ± 6 vs. 61 ± 3%, p = .014), older age (61 ± 11 vs. 51 ± 11 years, p = .03) and more diastolic dysfunction (71 vs. 22%, p = .008) Multivariate regression showed that age (OR 1.1 per year, CI 1.007-1.199) and diastolic dysfunction (OR 6.36, CI 1.132-35.7, p = .036) were independent predictors of the U-pattern. Diastolic dysfunction (B 4.49, CI 1.61-7.37, p = .003) was the only independent predictor of ASI in linear regression analysis.

CONCLUSION

AF patients with a U-pattern have an increased LA asymmetry. Diastolic dysfunction is a common cause of this LA activation and remodeling. Therefore, detection of a U-pattern signifies patients with advanced AF and may facilitate selection for an appropriate ablation strategy.

Determinants of left intra-atrial electromechanical delay as evaluated by tissue Doppler imaging in candidates for coronary artery bypass graft surgery

OBJECTIVES

Inhomogeneity in the atrial conduction time is a predisposing factor for atrial fibrillation. The aim of our study was to determine the independent determinants of the left intra-atrial electromechanical delay (LIAEMD) as a marker of left atrial (LA) dyssynchrony in candidates for coronary artery bypass graft surgery (CABGS).

METHODS

This prospective cross-sectional study recruited 516 consecutive candidates for CABGS. Via the pulsed-wave tissue Doppler imaging modality in echocardiography, the times between the P wave and the peak of the a' wave at the septal and lateral mitral annuli were measured and the difference between these times was considered to be LIAEMD. Additionally, clinical and laboratory data on each patient were gathered. The odds ratio for an increased LIAEMD was calculated in patients with and without diabetes in univariate and multivariate analyses.

RESULTS

The multivariable analysis revealed that in the patients without diabetes, obesity, calcium-channel blocker usage, an increased maximal LA volume, and a decreased lateral e'/a' ratio and in the diabetic patients, diuretic usage and a decreased lateral e'/a' ratio were independently correlated with an increased likelihood of LIAEMD occurrence (P < .05).

CONCLUSIONS

In our study on CABGS candidates, in the patients without diabetes, obesity, an increased maximal LA volume, calcium-channel blocker usage, and a decreased lateral e'/a' ratio and in the diabetic patients, diuretic usage and a decreased lateral e'/a' ratio independently determined increased LIAEMD. The prevention or treatment of factors that are detrimental to the LA electromechanical function may be helpful for the preservation of the LA electromechanical integrity.