Interatrial block (IAB) is associated with thromboembolism and atrial arrhythmias. However, prior studies included small patient cohorts so it remains unclear whether IAB predicts adverse outcomes particularly in context of atrial fibrillation (AF)/atrial flutter (AFL).

This study sought to determine whether IAB portends increased stroke risk in a large cohort in the presence or absence of AFAF/AFL.

We performed a 5-center retrospective analysis of 4,837,989 electrocardiograms (ECGs) from 1,228,291 patients. IAB was defined as P-wave duration ≥120 ms in leads II, III, or aVF. Measurements were extracted as .XML files. After excluding patients with prior AF/AFL, 1,825,958 ECGs from 458,994 patients remained. Outcomes were analyzed using restricted mean survival time analysis and restricted mean time lost.

There were 86,317 patients with IAB and 355,032 patients without IAB. IAB prevalence in the cohort was 19.6% and was most common in Black (26.1%), White (20.9%), and Hispanic (18.5%) patients and least prevalent in Native Americans (9.2%). IAB was independently associated with increased stroke probability (restricted mean time lost ratio coefficient [RMTLRC]: 1.43; 95% CI: 1.35-1.51; tau = 1,895), mortality (RMTLRC: 1.14; 95% CI: 1.07-1.21; tau = 1,924), heart failure (RMTLRC: 1.94; 95% CI: 1.83-2.04; tau = 1,921), systemic thromboembolism (RMTLRC: 1.62; 95% CI: 1.53-1.71; tau = 1,897), and incident AF/AFL (RMTLRC: 1.16; 95% CI: 1.10-1.22; tau = 1,888). IAB was not associated with stroke in patients with pre-existing AF/AFL.

IAB is independently associated with stroke in patients with no history of AF/AFL even after adjustment for incident AF/AFL and CHA2DS2-VASc score. Patients are at increased risk of stroke even when AF/AFL is not identified.

P wave morphology on electrocardiogram is often overlooked but indicates abnormal cardiac conduction from various etiologies. Split P waves on electrocardiogram have been reported previously but not in a perioperative setting.

A 69-year-old Caucasian male patient with widely split P waves on his preoperative electrocardiogram was scheduled for a reimplantation right total hip replacement under a combined spinal-general anesthetic technique. The patient was evaluated prior to surgery by a cardiologist and the preoperative anesthesia clinic without any comment on the abnormal P wave morphology on electrocardiogram. The patient was cleared to proceed with anesthesia and surgery. Following induction of general anesthesia, his cardiac rhythm changed to a Mobitz type II pattern. The surgical procedure was cancelled, and a permanent cardiac pacemaker was inserted.

Anesthesiologists should be aware that the presence of widely split P waves on electrocardiogram indicates the presence of atrial conduction abnormalities, likely from an ischemic or infiltrative process that can lead to more serious cardiac arrhythmias. P wave morphology should be observed and noted during the perioperative period for all patients.

Interatrial block (IAB) is an electrocardiographic pattern describing the conduction delay between the right and left atria. IAB is classified into 3 degrees of block that correspond to decreasing conduction in the region of Bachmann's bundle. Although initially considered benign in nature, specific subsets of IAB have been associated with atrial arrhythmias, elevated thromboembolic stroke risk, cognitive impairment, and mortality. As the pathophysiologic relationships between IAB and stroke are reinforced, investigation has now turned to the potential benefit of early detection, atrial imaging, cardiovascular risk factor modification, antiarrhythmic pharmacotherapy, and stroke prevention with oral anticoagulation. This review provides a contemporary overview of the epidemiology, pathophysiology, diagnosis, and management of IAB, with a focus on future directions.

The presence of interatrial block (IAB) is associated with the development of atrial fibrillation (AF). The aim of this study was to determine whether P-wave duration and presence of IAB before the implantation of a cardiac implantable electronic device (CIED) are associated with the presence of atrial high rate episodes (AHRE), during long-term follow-up.

380 patients (57% men; 75 ± 10 years) were included. IAB was defined according to the International Consensus Criteria. AHRE was defined as an episode of atrial rate ≥225 beats/min with a minimum duration of 5 minutes.

Documented paroxysmal AF before the implantation was present in 24% of the patients; 80% had hypertension and 32% structural heart disease. Mean P-wave duration was 123 ± 23 ms, and 39% of the patients had IAB (32% partial, 7% advanced). After a mean follow-up of 18 ± 12 months, 33% of the patients presented AHRE. Patients with AHRE had a P-wave duration significantly longer (130 ± 24 ms vs 119 ± 21 ms; P < 0.001) and a greater prevalence of IAB (53% vs 32%; P < 0.001). In a multivariate analysis, predictors of AHRE were: IAB (odds ratio [OR] 2.1; 95% confidence interval [CI] [1.3-3.4], P < 0.001) and previous paroxysmal AF (OR 2.6; 95% CI [1.5-4.3], P < 0.001). In patients without previous AF, the presence of IAB was also a significant predictor of AHRE (OR 3.1; 95% CI [1.8-5.5], P < 0.001).

IAB is a strong predictor of AHRE in patients with CIED. This finding is independent of the presence of prior paroxysmal AF.

Interatrial block (IAB) is a well-known entity that is associated with an increased risk of atrial fibrillation (AF). This association is called Bayes' syndrome. The aim of our study was to define the prevalence of IAB among patients younger than 65 years undergoing cardiac surgery and determine whether there is an association between the presence of interatrial conduction delay and postoperative atrial fibrillation (POAF).

A total of 207 patients were enrolled. Partial IAB was defined as P-wave>120ms. Advanced IAB was defined as P-wave>120ms+biphasic morphology in the inferior leads. Ocurrence of POAF was assessed and a comparative analysis was conducted between patients that did and did not develop AF.

IAB prevalence was 78.3% (partial 66.2%, advanced 12.1%). POAF occurred in 28.5% of all patients, and was more frequent among patients with advanced IAB (44%) compared to 27.7% and 24.4% of POAF among patients with partial IAB and without IAB, respectively. Patients who developed POAF were significantly older, had significantly higher NTproBNP, higher prevalence of atrial enlargement and thyroid disease. After multivariate analysis, advanced IAB was found to be independently associated with POAF.

IAB is a frequent finding among patients undergoing cardiac surgery. According to our results, advanced IAB is independently associated with POAF in younger patients (<65 years) undergoing cardiac surgery.

Bayés syndrome is an under-recognized clinical condition characterized by inter-atrial block (IAB). This is defined electrocardiographically as P-wave duration > 120 ms and can be categorized into first, second and third degree IAB. It can be caused by inflammatory conditions such as systemic sclerosis and rheumatoid arthritis, abnormal protein deposition in cardiac amyloidosis, or neoplastic processes invading the inter-atrial conduction system, such as primary cardiac lymphoma. It may arise transiently during volume overload, autonomic dysfunction or electrolyte disturbances from vomiting. In other patients without an obvious cause, the predisposing factors are diabetes mellitus, hypertensive heart disease, and hypercholesterolemia. IAB has a strong association with atrial arrhythmogenesis, left atrial enlargement (LAE), and electro-mechanical discordance, increasing the risk of cerebrovascular accidents as well as myocardial and mesenteric ischemia. The aim of this review article is to synthesize experimental evidence on the pathogenesis of IAB and its underlying molecular mechanisms. Current medical therapies include anti-fibrotic, anti-arrhythmic and anti-coagulation agents, whereas interventional options include atrial resynchronization therapy by single or multisite pacing. Future studies will be needed to elucidate the significance of the link between IAB and atrial tachyarrhythmias in patients with different underlying etiologies and optimize the management options in these populations.

Data are lacking on the characteristics of atrial activity in centenarians, including interatrial block (IAB).

The aim of this study was to describe the prevalence of IAB and auricular arrhythmias in subjects older than 100 years and to elucidate their clinical implications.

We studied 80 centenarians (mean age 101.4 ± 1.5 years; 21 men) with follow-ups of 6-34 months. Of these 80 centenarians, 71 subjects (88.8%) underwent echocardiography. The control group comprised 269 septuagenarians.

A total of 23 subjects (28.8%) had normal P wave, 16 (20%) had partial IAB, 21 (26%) had advanced IAB, and 20 (25.0%) had atrial fibrillation/flutter. The IAB groups exhibited premature atrial beats more frequently than did the normal P wave group (35.1% vs 17.4%; P < .001); also, other measurements in the IAB groups frequently fell between values observed in the normal P wave and the atrial fibrillation/flutter groups. These measurements included sex preponderance, mental status and dementia, perceived health status, significant mitral regurgitation, and mortality. The IAB group had a higher previous stroke rate (24.3%) than did other groups. Compared with septuagenarians, centenarians less frequently presented a normal P wave (28.8% vs 53.5%) and more frequently presented advanced IAB (26.3% vs 8.2%), atrial fibrillation/flutter (25.0% vs 10.0%), and premature atrial beats (28.3 vs 7.0%) (P < .01).

Relatively few centenarians (<30%) had a normal P wave, and nearly half had IAB. Our data suggested that IAB, particularly advanced IAB, is a pre-atrial fibrillation condition associated with premature atrial beats. Atrial arrhythmias and IAB occurred more frequently in centenarians than in septuagenarians.

The past few years have given rise to extensive research on atrial conduction disorders and their clinical relevance. Most notably, an association between interatrial block and supraventricular arrhythmias has been discovered. This disorder, recently termed 'Bayés' syndrome', has important clinical implications. In this article, the authors review normal atrial conduction and associated disorders. A particular focus is placed on Bayés' syndrome and the relationship between interatrial block and supraventricular arrhythmias in different clinical scenarios. The report also outlines the current progress in the study of this syndrome and highlights areas requiring further investigation.

Right (RA) and left atrial (LA) damage was produced with a subepicardial infiltration of 96 degrees alcohol in two groups of dogs. In six other dogs the left or right portion of the interatrial band was also injured. Conventional ECG and supplementary unipolar leads were recorded using photographic and direct inscription polygraphs at paper speeds of 50 and 100 mm/sec. Control, immediate postinjury and late tracings were obtained. A-V block was provoked to determine QTac. Slowing of heart rate and slight widening of the P wave and P-R interval were observed with both types of atrial damage. In four cases low right atrial rhythm was detected: two showed anatomo-histological sinus node involvement in right atrial injury. Qp waves were registered over the left precordium with necrosis of both sides, but were more frequent with RA damage. Damage of the left portion of the interatrial band delayed left atrial activation and split P waves in the precordial leads. Damage of the RA distorts the initial vectors, magnifying the left ones and simulating LA enlargement. The Qp registered on the RA is also detected by surface leads. Contrary distorted LA depolarization increases the RA vector and delays the left, ones, giving rise to greater asynchronsim and bimodal P waves.

The P wave of the ECG, recorded with both conventional and special techniques, was compared with left atrial (LA) pressure and volume in 22 patients with mitral valve disease. The patients were also compared with 2 groups of normal subjects as to the P wave, recorded with the special technique. Changes in the P wave, such as increased duration, increased bipeak interval or P terminal force were significantly more common in the patients than in normal subjects. Among the patients, no significant correlations were found between degree of LA pressure elevation, LA enlargement and P wave changes. It is concluded that for the diagnosis of increased LA load it is more useful to study the terminal vector of the P wave than signs of increased atrial asynchrony. Recordings with high amplification and paper speed as in the present special technique are of advantage for such measurements. However, the special leads by themselves were not ideal for study of an increased terminal vector directed to the left and backwards.