Background The association between advanced interatrial block (aIAB) and atrial fibrillation (AF) is known as "Bayes' Syndrome." There is little information on the prognostic role that new speckle tracking echocardiographic (STE) imaging techniques could play in it. We have examined the relationship between left atrial (LA) STE and the prediction of new-onset AF and/or stroke in IAB patients. Methods This is an observational prospective and unicentric cohort study with 98 outpatients: 55 (56.2%) controls with normal ECG without IAB, 21 (21.4%) with partial IAB (pIAB) and 22 (22.4%) with aIAB. The end point was new-onset AF, ischemic stroke and the composite of both. Results During a mean follow-up of 1.9 (1.7-2.3) years, 20 patients presented the end point (18 new-onset AF and two strokes): 8 (14.5%) in the control group, 3 (14.3%) in pIAB and 9 (40.9%) in aIAB, p = 0.03. In multivariable comprehensive Cox regression analyses, a decrease in absolute value of strain rate during the booster pump function phase (SRa) was the only variable independently related to the appearance in the evolution of the end point, in the first model (age, P-wave duration and SRa): HR 19.9 (95% CI, 3.12-127.5), p = 0.002 and in the second (age, presence of aIAB and SRa): HR 24.2 (95% CI, 3.15-185.4), p = 0.002. Conclusions In patients with IAB, a decrease in absolute value of LA SRa with STE predicts new-onset AF and ischemic stroke. Future studies should confirm our results and assess the prognostic usefulness of LA STE in patients with IAB.

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Advanced interatrial block is a surrogate for left atrial strain reduction which predicts atrial fibrillation and stroke.

Alterations of normal intra- and interatrial conduction are a common outcome of multiple cardiovascular conditions. They arise most commonly in the context of advanced age, cardiovascular risk factors, organic heart disease, atrial fibrosis, and left atrial enlargement. Interatrial block (IAB), the most frequent and extensively studied atrial conduction disorder, affects up to 20% of the general primary care population. IAB can be partial (P wave duration ≥ 120 ms on any of the 12 ECG leads) or advanced (P wave ≥ 120 ms and biphasic morphology (positive-negative) in inferior leads). Advanced IAB is an independent risk factor for supraventricular tachyarrhythmias and embolic stroke in a variety of clinical settings. Advanced IAB is a cause of left atrial electromechanical dysfunction and left atrioventricular dyssynchrony and has been associated with left ventricular diastolic dysfunction. P wave duration is associated with cardiovascular and all-cause mortality in the general population. Atrial conduction abnormalities should be identified as markers of atrial remodeling, prognostic indicators, and, in the case of advanced IAB, a true arrhythmologic syndrome. IAB and other P wave abnormalities should prompt the search for associated conditions, the treatment of which may partially reverse atrial remodeling or prevent it if administered upstream. Future studies will help define the role of preventive therapeutic interventions in high-risk patients, including antiarrhythmic drug therapy and oral anticoagulation. Implications for the treatment of heart failure and for pacing should also be further investigated.

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Intra- and interatrial conduction abnormalities: hemodynamic and arrhythmic significance

Introduction Advanced interatrial block (IAB) on a 12-lead electrocardiogram (ECG) is a predictor of stroke, incident atrial fibrillation (AF), and AF recurrence after catheter ablation. The objective of this study was to determine which features of IAB structural remodeling is associated with left atrium (LA) magnetic resonance imaging structure and function. Methods/results We included 152 consecutive patients (23% nonparoxysmal AF) who underwent preprocedural ECG and cardiac magnetic resonance (CMR) in sinus rhythm before catheter ablation of AF. IAB was defined as P-wave duration ≥120 ms, and was considered partial if P-wave was positive and advanced if P-wave had a biphasic morphology in inferior leads. From cine CMR and late gadolinium enhancement, we derived LA maximum and minimum volume indices, strain, LA fibrosis, and LA dyssynchrony. A total of 77 patients (50.7% paroxysmal) had normal P-wave, 52 (34.2%) partial IAB, and 23 (15.1%) advanced IAB. Patients with advanced IAB had significantly higher LA minimum volume index (25.7 vs 19.9 mL/m2 , P = .010), more LA fibrosis (21.9% vs 13.1%, P = .020), and lower LA maximum strain rate (0.99 vs 1.18, P = .007) than those without. Advanced IAB was independently associated with LA (minimum [P = .032] and fibrosis [P = .009]). P-wave duration was also independently associated with LA fibrosis (β = .33; P = .049) and LA mechanical dyssynchrony (β = 2.01; P = .007). Conclusion Advanced IAB is associated with larger LA volumes, lower emptying fraction, and more fibrosis. Longer P-wave duration is also associated with more LA fibrosis and higher LA mechanical dyssynchrony.

Association between interatrial block, left atrial fibrosis, and mechanical dyssynchrony: Electrocardiography-magnetic resonance imaging correlation.

Resumen El sindrome de Bayes es una nueva entidad clinica, caracterizada por la combinacion de bloqueo interauricular (BIA) avanzado en el electrocardiograma de superficie con fibrilacion auricular (FA) y otras arritmias auriculares. Este sindrome se asocia con un riesgo incrementado de ictus, demencia y mortalidad. El BIA avanzado se diagnostica con la presencia de una onda P ≥ 120 ms de morfologia bifasica (±) en derivaciones de cara inferior. Se produce por un bloqueo completo del haz de Bachmann que causa una despolarizacion retrograda de la auricula izquierda desde zonas cercanas a la union auriculoventricular. La miocardiopatia auricular fibrotica es el sustrato anatomico del BIA avanzado. La disincronia inducida por el BIA avanzado funciona como desencadenante y mecanismo de mantenimiento de la FA. Esta alteracion de la arquitectura auricular produce remodelado auricular, estasis sanguinea e hipercoagulabilidad, lo cual desencadena la cascada trombogenica. El BIA avanzado, incluso sin arritmias auriculares documentadas, tambien se ha relacionado con FA, ictus, demencia y mortalidad. Sin embargo, todavia no se ha demostrado el beneficio de la anticoagulacion para los pacientes sin FA documentada. Por lo tanto, es recomendable una busqueda proactiva de FA en los pacientes con BIA avanzado.

Síndrome de Bayés. Lo que todo clínico debe conocer

Advanced interatrial block (A-IAB) has been associated to atrial fibrillation (AF) and ischemic stroke, raising the question as to whether such patients, even when still in sinus rhythm without documented AF, could benefit from oral anticoagulation. AF and A-IAB are both markers of stroke. The anatomical substrate in both is fibrotic atrial cardiomyopathy, resulting in atrial electromechanical dyssynchrony, dysfunction, and left atrial remodelling, that favour blood stasis and hypercoagulation. Under these conditions thrombogenic cascade may be triggered, resulting in systemic embolization. Before proposing oral anticoagulation in the management of selected patients with A-IAB, as is currently recommended in patients with AF and high CHA2DS2-Vasc score, a randomized clinical trial will have to demonstrate efficacy and safety of anticoagulation in this setting. In the meantime, an individualized approach may be considered based on the recognition of those patients at a higher risk of stroke. These may be elderly patients with A-IAB and several risk factors and, thus, with a high CHA2DS2-Vasc score and the presence of environmental arrhythmias.

Relation of Advanced Interatrial Block to Risk of Atrial Fibrillation and Stroke

To evaluate the possibility of left atrial (LA) remodeling using speckle tracking echocardiography (STE) in patients with interatrial block (IAB). We performed a cross-sectional study with three groups of patients: 56 without IAB, 21 with partial IAB (pIAB), and 22 with advanced IAB (aIAB). Transthoracic echocardiographic (TTE) STE was performed and clinical and echocardiographic findings were analyzed. TTE showed higher LA volume/body surface area in the patients with IAB. With STE, the absolute value of strain rate during atrial booster pump function (SRa) and early reservoir period (SRs) decreased in the pIAB group and even more in the aIAB group, compared to the group without IAB. The independent variables were the echocardiographic measures of LA size and function. After adjusting for confounders, both multiple linear regression and multivariate multinomial regression showed good correlation with dependent variables: longer P-wave duration on electrocardiography and with the type of IAB, respectively. SRa (p < 0.001), SRs (p < 0.001), and maximal peak LA longitudinal strain in the reservoir period (p = 0.009) were independently associated with P-wave duration. SRa was also associated with the presence of pIAB (OR = 11.5; 95% confidence interval (CI): 2.7–49.0; p = 0.001) and aIAB, (OR = 98.2; 95% CI: 16–120.4; p < 0.001) and SRs was associated with pIAB (OR: 0.03; CI: 0.003–0.29; p = 0.003) and with aIAB (OR: 0.008; CI: 0.001–0.12; p = 0.004). IAB correlates directly with structural remodeling and a decrease in the absolute value of LA SRa and SRs determined using STE.

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Patricia Barrio-Martínez

Papers

Interatrial block and atrial remodeling assessed using speckle tracking echocardiography.