Analysis of the Association Between Electrocardiographic P-wave Characteristics and Atrial Fibrillation in the REGICOR Study

New electrocardiographic aspects of the P wave: Its value in clinical cardiology

In this article, we will comment on new aspects of P-wave morphology that help us to better diagnose atrial blocks and atrial enlargement, and their clinical implications. These include: (1) Atypical ECG patterns of advanced interatrial block; (2) The ECG diagnosis of left atrial enlargement versus interatrial block; (3) Atrial fibrillation and advanced interatrial block: The two sides of the same coin; and (4) P-wave parameters: Clinical implications.

P Wave Parameters and Indices: A Critical Appraisal of Clinical Utility, Challenges, and Future Research-A Consensus Document Endorsed by the International Society of Electrocardiology and the International Society for Holter and Noninvasive Electrocardiology

Atrial cardiomyopathy, characterized by abnormalities in atrial structure and function, is associated with increased risk of adverse cardiovascular and neurocognitive outcomes, independent of atrial fibrillation. There exists a critical unmet need for a clinical tool that is cost-effective, easy to use, and that can diagnose atrial cardiomyopathy. P wave parameters (PWPs) reflect underlying atrial structure, size, and electrical activation; alterations in these factors manifest as abnormalities in PWPs that can be readily ascertained from a standard 12-lead ECG and potentially be used to aid clinical decision-making. PWPs include P wave duration, interatrial block, P wave terminal force in V₁, P wave axis, P wave voltage, P wave area, and P wave dispersion. PWPs can be combined to yield an index (P wave index), such as the morphology-voltage-P-wave duration ECG risk score. Abnormal PWPs have been shown in population-based cohort studies to be independently associated with higher risks of atrial fibrillation, ischemic stroke, sudden cardiac death, and dementia. Additionally, PWPs, either individually or in combination (as a P wave index), have been reported to enhance prediction of atrial fibrillation or ischemic stroke. To facilitate translation of PWPs to routine clinical practice, additional work is needed to standardize measurement of PWPs (eg, via semiautomated or automated measurement), confirm their reliability and predictive value, leverage novel approaches (eg, wavelet analysis of P waves and machine learning algorithms), and finally, define the risk-benefit ratio of specific interventions in high-risk individuals. Our ultimate goal is to repurpose the ubiquitous 12-lead ECG to advance the study, diagnosis, and treatment of atrial cardiomyopathy, thus overcoming critical challenges in prevention of cardiovascular disease and dementia.

Beat-to-Beat P-Wave Analysis Outperforms Conventional P-Wave Indices in Identifying Patients with a History of Paroxysmal Atrial Fibrillation during Sinus Rhythm

Early identification of patients at risk for paroxysmal atrial fibrillation (PAF) is essential to attain optimal treatment and a favorable prognosis. We compared the performance of a beat-to-beat (B2B) P-wave analysis with that of standard P-wave indices (SPWIs) in identifying patients prone to PAF. To this end, 12-lead ECG and 10 min vectorcardiogram (VCG) recordings were obtained from 33 consecutive, antiarrhythmic therapy naïve patients, with a short history of low burden PAF, and from 56 age- and sex-matched individuals with no AF history. For both groups, SPWIs were calculated, while the VCG recordings were analyzed on a B2B basis, and the P-waves were classified to a primary or secondary morphology. Wavelet transform was used to further analyze P-wave signals of main morphology. Univariate analysis revealed that none of the SPWIs performed acceptably in PAF detection, while five B2B features reached an AUC above 0.7. Moreover, multivariate logistic regression analysis was used to develop two classifiers-one based on B2B analysis derived features and one using only SPWIs. The B2B classifier was found to be superior to SPWIs classifier; B2B AUC: 0.849 (0.754-0.917) vs. SPWIs AUC: 0.721 (0.613-0.813), p value: 0.041. Therefore, in the studied population, the proposed B2B P-wave analysis outperforms SPWIs in detecting patients with PAF while in sinus rhythm. This can be used in further clinical trials regarding the prognosis of such patients.

The prevalence and prognostic significance of interatrial block in the general population

Introduction: Partial and advanced interatrial block (IAB) in the electrocardiographic (ECG) represents inter-atrial conduction delay. IAB is associated with atrial fibrillation (AF) and stroke in the general population.Material and methods: A representative sample of Finnish subjects (n = 6354) aged over 30 years (mean: 52.2 years, standard deviation: 14.6) underwent a health examination including a 12-lead ECG. Five different IAB groups based on automatic measurements were compared to normal P waves using multivariate-adjusted Cox proportional hazard model. Follow-up lasted up to 15 years.Results: The prevalence of advanced and partial IAB was 1.0% and 9.7%, respectively. In the multivariate model, both advanced (hazard ratio (HR): 1.63 (95% confidence interval (CI): 1.00-2.65)) and partial IAB (HR: 1.39 (1.09-1.77)) were associated with increased risk of AF. Advanced IAB was associated with increased risk of stroke or transient ischaemic attack (TIA) independently of associated AF (HR: 2.22 (1.20-4.13)). Partial IAB was also associated with increased risk of being diagnosed with coronary heart disease (HR: 1.26 (1.01-1.58)).Discussion: IAB is a rather frequent finding in the general population. IAB is a risk factor for AF and is associated with an increased risk of stroke or TIA independently of associated AF.Key messagesBoth partial and advanced interatrial block are associated with increased risk of atrial fibrillation in the general population.Advanced interatrial block is an independent risk factor for stroke and transient ischaemic attack.The clinical significance of interatrial block is dependent on the subtype classification.

Simulation of inter atrial block based on a human atrial model

Inter atrial block (IAB) is a prevailing cardiac conduction abnormality that is under-recognized in clinical practice. IAB has strong association with atrial arrhythmia, left atrial enlargement, and electromechanical discordance, increasing the risk of atrial fibrillation (AF) and myocardial ischemia. IAB was generally believed to be caused by impaired conduction along the Bachmann bundle (BB). However, there are three other conduction pathways, including the fibers posteriorly in the vicinity of the right pulmonary veins (VRPV), transseptal fibers in the fossa ovalis (FO), and muscular bundles on the inferior atrial surface near the coronary sinus (CS). We hypothesized that the importance of BB on IAB might have been overestimated. To test this hypothesis, various combinations of conduction pathway blocks were simulated based on a realistic human atrial model to investigate their effects on the index of clinical diagnosis standard of IAB using a simulated 12-lead electrocardiogram (ECG). Firstly, the results showed that the BB block alone could not generate typical P wave morphology of IAB, and that the combination of BB and VRPV pathway block played important roles in the occurrence of IAB. Secondly, although single FO and CS pathways play subordinate roles in inter atrial conduction, their combination with BB and VRPV block could also produce severe IAB. In summary, this simulation study has demonstrated that the combinations of different inter atrial conduction pathways, rather than BB alone, resulted in ECG morphology of IAB. Attention needs to be paid to this in future pathophysiological and clinical studies of IAB.

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

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.

Second-degree interatrial block: Brief review and concept

The advanced interatrial block (A-IAB) (P ≥ 120 ms plus ± pattern in II, III and aVF) corresponds at atrial level, to right or left advanced bundle branch block at ventricular level, and it is well known that these patterns may be seen transiently in relation to taquicardia or bradycardia (tachycardia or bradycardia dependent right or left bundle branch block). We present for the first time, the same phenomenon at atrial level. In one case, the A-IAB appears in relation to tachycardization and in the other disappears during a pause induced by ventricular premature complex.