Interatrial block: is it time for more attention?

Atrial depolarization abnormalities in pulmonary sarcoidosis

BACKGROUND

Cardiac sarcoidosis, often manifested as sudden death, can be the first manifestation of sarcoidosis. Since 12-lead electrocardiogram (ECG) is recommended as an initial screening tool for cardiac sarcoidosis, the recognition of subtle abnormalities assumes utmost significance. The objective of this study was to identify the electrocardiographic abnormalities in patients with pulmonary sarcoidosis.

RESULTS

A detailed analysis of 12-lead ECGs obtained from sixty patients with histopathologically proven pulmonary sarcoidosis and no overt cardiac involvement was done. The findings were compared with those of an age-matched control group. Varying degrees of intraventricular conduction defects were common in the study group [67%], as well as the control group [57%] [P = 0.23]. There was a higher prevalence of biphasic P wave [P = 0.003] and bifid P wave [P = 0.029] in lead III and rsr' in lead aVF [P = 0.03] in the study group as compared to the control group.

CONCLUSIONS

Our study demonstrates a greater prevalence of subtle ECG abnormalities in patients with pulmonary sarcoidosis as compared to patients with other forms of pulmonary disease. Atrial depolarization abnormalities were commoner in patients with pulmonary sarcoidosis.

Interatrial Block Predicts Atrial Fibrillation and Total Mortality in Patients with Cardiac Resynchronization Therapy

BACKGROUND

Interatrial block (IAB) and abnormal P-wave terminal force in lead V1 (PTFV1) are electrocardiographic (ECG) abnormalities that have been shown to be associated with new-onset atrial fibrillation (AF) and death. However, their prognostic importance has not been proven in cardiac resynchronization therapy (CRT) recipients.

OBJECTIVE

To assess if IAB and abnormal PTFV1 are associated with new-onset AF or death in CRT recipients.

METHODS

CRT recipients with sinus rhythm ECG at CRT implantation and no AF history were included (n = 210). Automated analysis of P-wave duration (PWD) and morphology classified patients as having either no IAB (PWD <120 ms), partial IAB (pIAB: PWD ≥120 ms, positive P waves in leads II and aVF), or advanced IAB (aIAB: PWD ≥120 ms and biphasic or negative P wave in leads II or aVF). PTFV1 >0.04 mm•s was considered abnormal. Adjusted Cox regression analyses were performed to assess the impact of IAB and abnormal PTFV1 on the primary endpoint new-onset AF, death, or heart transplant (HTx) and the secondary endpoint death or HTx at 5 years of follow-up.

RESULTS

IAB was found in 45% of all patients and independently predicted the primary endpoint with HR 1.9 (95% CI 1.2-2.9, p = 0.004) and the secondary endpoint with HR 2.1 (95% CI 1.2-3.4, p = 0.006). Abnormal PTFV1 was not associated with the endpoints.

CONCLUSIONS

IAB is associated with new-onset AF and death in CRT recipients and may be helpful in the risk stratification in the context of heart failure management. Abnormal PTFV1 did not demonstrate any prognostic value.

Cardiac arrhythmia caused by a novel type of atrial conduction block: A case report

INTRODUCTION

We report an extremely rare case of atrial conduction block with unusual electrocardiogram (ECG) results, which has never been reported before. There are 2 types of atrial conduction block that result in atrial irregularities or complete atrial conduction block. The former is similar to other types of cardiac blocks such as sinus node to atrial block, atrial to ventricular block, or bundle branch blocks, which are characterized by 2 P waves at a specific frequency. This is due to the complete inner atrial block that results in the atrial muscle being divided into 2 parts without conduction between them so that each part has its rhythm generator. The objective of this report is to examine the cause of inner atrial conduction block and to promote awareness of this disorder.

PATIENT CONCERNS

An 81-year-old Chinese male patient was examined after complaining about chest discomfort, and it was found that he had atrial tachycardia; ECG results revealed a P wave loss at specific intervals (or P wave separation).

DIAGNOSIS

A diagnosis of P wave loss at specific intervals (or P wave separation) was made based on ECG results.

INTERVENTIONS

An ECG was performed on the patient OUTCOMES:: It was unclear whether this patient has atrial separation or a new type of atrial conduction block, but our results revealed that this case presents a novel type of atrial conduction block, which we named 'P wave block.'

CONCLUSION

The type of EKG shown in this case has never been reported. This EKG shows a new type of conduction block in the atrium, temporarily named as a new type of P wave block.

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.

Biphasic P wave in inferior leads and the development of atrial fibrillation

Background

Anisotropic and slow conduction in the atrium underlie the development of atrial fibrillation (AF). This study aimed to investigate the P wave characteristics associated with the development of AF in patients with a biphasic P wave in the inferior leads.

Methods

Digital analysis of retrospectively recorded 12-lead electrocardiograms was performed to select patients with a biphasic P wave (positive/negative) in lead II from a database of 114,334 patients. Characteristics of the P wave in the inferior leads associated with incidence of AF were determined. Receiver operating characteristic curves dichotomized P wave variables were measured in each lead.

Results

A total of 141 patients (77 men; mean age, 64±19 years) were enrolled in this study. Twenty-nine (20.6%) patients developed AF (AF group) vs. 112 (79.6%) who did not (non-AF group) during a follow-up period of 50±62 months. The amplitude of the initial P wave portion in lead II was significantly larger in the AF group when compared with the non-AF group (77.3±77.0 µV vs. 51.0±30.1 µV, p=0.003), while the amplitude of the terminal P wave portion in lead III was significantly decreased in the AF group when compared with the non-AF group (−70.6±41.3 µV vs. −89.1±38.1 µV, p=0.024). The duration of the initial P wave portion in lead III was significantly longer in the AF group when compared with the non-AF group (52.7±34.6 ms vs. 35.8±30.4 ms, p=0.011). Multivariate Cox proportional-hazards analysis confirmed that the increased duration of the initial P wave portion in lead III (≥71 ms) was independently associated with AF development (hazard ratio 2.90, 95% confidence interval 1.16–7.11, p=0.02).

Conclusion

The analyses of the biphasic P wave in the inferior leads suggest that the development of AF could be attributed to increased atrial slow conduction.

Advanced interatrial block predicts clinical recurrence of atrial fibrillation after catheter ablation

BACKGROUND

It has been demonstrated that advanced interatrial block (IAB) is associated with an increased risk of atrial fibrillation (AF); however, the impact of advanced IAB on recurrence of paroxysmal AF after catheter ablation is not clear.

METHODS

204 consecutive patients with paroxysmal AF who underwent index circumferential pulmonary vein (PV) isolation were prospectively enrolled. In all patients, a resting electrocardiogram in sinus rhythm was evaluated for the presence of advanced IAB, defined as a P-wave duration >120ms and biphasic (±) morphology in the inferior leads. Advanced IAB was detected in 20.1% of patients. AF recurrence was defined as the occurrence of confirmed atrial tachyarrhythmia lasting more than 30s beyond 3 months after the catheter ablation in the absence of any antiarrhythmic treatment.

RESULTS

During the mean follow-up period of 13.9±6.2 months (range, 3-27 months), 62 patients (30.4%) developed recurrence of AF. The recurrence rate was higher in patients with advanced IAB than those without advanced IAB (46.3% vs. 26.4%, p=0.006). Cox regression analysis with adjustment for age, P-wave duration, CHADS2 score, and PV isolation identified advanced IAB (hazard ratio, 2.111; 95% confidence interval, 1.034-4.308; p=0.040) and left atrial diameter (hazard ratio, 1.051; 95% confidence interval, 1.004-1.100; p=0.034) as two independent predictors of recurrence of AF.

CONCLUSIONS

Patients with advanced IAB were at an increased risk of AF recurrence after catheter ablation.

Revisiting Clinical Utility of Chest Radiography and Electrocardiogram to Determine Ischemic Stroke Subtypes: Special Reference on Vascular Pedicle Width and Maximal P-Wave Duration

BACKGROUNDS

It is often difficult to diagnose stroke subtypes at admission, particularly in sinus rhythm cases. Vascular pedicle width (VPW) on chest X-ray (CXR) and maximal P-wave duration (P-max) on electrocardiogram (ECG) are again realized as useful parameters reflecting intravascular volume and atrial conduction status, respectively. We investigated the utility of VPW and P-max as a tool for differentiating ischemic stroke subtypes.

METHODS

We studied 343 acute stroke patients showing sinus rhythm on admission. Dividing the patients into cardioembolic (CE) stroke (n = 57) and non-CE (n = 286) groups, we compared clinical backgrounds including VPW on CXR, and P-max in lead II and premature atrial contraction (PAC) on 12-leads ECG. Then, we investigated the independent factors for CE.

RESULTS

Independent factors associated with CE were VPW (≥59.3 mm) (p < 0.001; odds ratio (OR), 10.12; 95% confidence interval (CI), 4.13-24.8), P-max in lead II (≥120 ms) (p < 0.001; OR, 8.61; 95% CI, 3.96-18.7), PAC (p = 0.002; OR, 7.35; 95% CI, 2.14-25.3) and D-dimer level (≥1.11 µg/ml) (p = 0.016; OR, 2.57; 95% CI, 1.20-5.51).

CONCLUSIONS

VPW, P-max, PAC and D-dimer are useful parameters for diagnosing CE stroke in patients with sinus rhythm at admission.

Prolonged P wave duration predicts stroke mortality among type 2 diabetic patients with prevalent non-major macrovascular disease

Background

Prolonged P wave duration is a marker of delayed inter-atrial conduction which may predict cardiovascular disease (CVD). Type 2 diabetes is a risk factor for all atherosclerotic manifestations including stroke. We evaluated the prognostic significance of prolonged P wave duration among middle-aged Finnish type 2 diabetes patients with and without prevalent non-major macrovascular disease (PNMMVD) with respect to total and stroke mortality.

Methods

We followed up for 18 years 739 type 2 diabetic patients without previous major CVD event at baseline. Participants were stratified according to P wave duration (<114 or ≥114 ms) and PNMMVD (i.e. coronary heart disease defined as ischaemic ECG changes and typical symptoms of angina pectoris, or claudication; yes or no). The Cox proportional hazards model was used to estimate the joint association between P wave duration, PNMMVD and the mortality risk.

Results

During the follow-up, 509 patients died, and 59 of them died from stroke. Those who had prolonged P wave duration had 2.45 (95% confidence interval: 1.11-5.37) increased stroke mortality among PNMMVD patients. In patients without PNMMVD, there was no relationship between P wave duration and stroke mortality.

Conclusions

As an easily measurable factor P wave duration merits further studies with higher number of patients to evaluate its importance in the estimation of stroke risk in type 2 diabetic patients with PNMMVD.

Interatrial block in the modern era

Interatrial block (IAB; P-wave duration ≥ 110 ms), which represents a delay in the conduction between the atria, is a pandemic conduction abnormality that is frequently underappreciated in clinical practice. Despite its comprehensive documentation in the medical literature, it has still not received adequate attention and also not adequately described and discussed in most cardiology textbooks. IAB can be of varying degrees and classified based on the degree of P-duration and its morphology. It can transform into a higher degree block and can also manifest transiently. IAB may be a preceding or causative risk factor for various atrial arrhythmias (esp. atrial fibrillation) and also be associated with various other clinical abnormalities ranging from left atrial dilation and thromboembolism including embolic stroke and mesenteric ischemia. IAB certainly deserves more attention and prospective studies are needed to formulate a standard consensus regarding appropriate management strategies.

Interatrial block - a novel risk factor for acute mesenteric ischemia

Interatrial block (IAB; P-wave duration ≥110 milliseconds) denotes a conduction delay between the two atria. IAB has been shown to have a strong correlation with atrial arrhythmias, left atrial enlargement, left atrial electromechanical dysfunction and cerebral thromboembolism. Our study sought to determine whether there was an increased incidence of IAB in patients with acute occlusive mesenteric ischemia. Medical records of patients admitted with a diagnosis of acute mesenteric ischemia (AMeI) from January 2009 to March 2011 were reviewed retrospectively. One hundred seventy-two out of 342 patients reviewed, qualified after excluding mechanical surgical obstruction, suspected non-occlusive mesenteric ischemia due to shock/hypoperfusion, and mesenteric venous thrombosis. Of 99 patients who were in normal sinus rhythm without prior history of atrial arrhythmia, 88 (88.9 %) had IAB. This was more than twice the average prevalence of IAB of two general hospital populations (41 % and 47 % as demonstrated by two previous studies). IAB may thus represent a novel risk factor for AMeI as it does for embolic stroke.

Variations of left atrial activation patterns in congestive heart failure

We report about a case of a patient admitted to the Intensive Cardiac Care Unit for severe congestive heart failure which showed modification of P-wave morphology and duration, correlated with the clinical evolution. In the case here described, we show that ECG analysis, specifically P wave, allow us to assess the hemodynamic evolution of the acute decompensated heart failure patient. Electrocardiographic examination is the first and the most simple and available diagnostic tool in the evaluation of patients with cardiac diseases. Usually, P-wave evaluation is not carefully assessed, in spite of very useful informations we can draw from its interpretation. We report about a patient admitted to our Intensive Cardiac Care Unit (ICCU) for severe congestive heart failure which showed peculiar modification of P-wave morphology and duration, well correlated with the clinical course.

Increased incidence of interatrial block in younger adults with cryptogenic stroke and patent foramen ovale

Background

Stroke is often unexplained in younger adults, although it is often associated with a patent foramen ovale (PFO). The reason for the association is not fully explained, and mechanisms other than paradoxical embolism may be involved. Young stroke patients with PFO have more atrial vulnerability than those without PFO. It is plausible that stretching of the interatrial septum may disrupt the interatrial conduction pathways causing interatrial block (IAB). IAB is associated with atrial fibrillation, dysfunctional left atria and stroke.

Methods

Electrocardiogram (ECG) characteristics of prospectively recruited young patients (≤55 years of age) with unexplained stroke (TOAST and A-S-C-O) were compared with control data. All stroke cases underwent bubble contrast transthoracic and transoesophageal echography. IAB was defined as a P-wave duration of ≥110 ms. ECG data were converted to electronic format and analysed in a blind manner.

Results

Fifty-five patients and 23 datasets were analysed. Patients with unexplained stroke had longer P-wave duration (p = 0.013) and a greater prevalence of IAB (p = 0.02) than healthy controls. Case status was an independent predictor of P-wave duration in a significant multivariate model. There was a significant increase in the proportion of cases with a PFO with IAB compared with cases without PFO and with controls (p = 0.005).

Conclusions

Young patients with unexplained stroke, particularly those with PFO, exhibit abnormal atrial electrical characteristics suggesting atrial arrhythmia or atrial dysfunction as a possible mechanism of stroke.

Effect of obesity on p-wave parameters in a Chinese population

OBJECTIVE

To study the association between obesity and P-wave duration and dispersion (P(d)) in order to evaluate the potential risk for atrial fibrillation development in Chinese subjects using the definitions applied for Asian populations.

METHODS

The study population consisted of 40 obese (body mass index (BMI) > or = 25 Kg/m(2), according to the World Health Organization classification for the Asian population) subjects and 20 age- and sex-matched normal weight controls. Maximum P-wave duration (P(max)), minimum P-wave duration (P(min)), and P(d) were carefully measured using a 12-lead electrocardiogram, while the presence of interatrial block (IAB; P > or = 110 ms) was assessed.

RESULTS

There were no significant differences between the two groups regarding age, sex, history of hypertension or diabetes, and hyperlipidemia. Compared to controls, BMI, left atrial diameter (LAD), and interventricular septal thickness were increased, while P(max) (111.9 +/- 9.3 vs 101.1 +/- 6.0 ms, P < 0.01) and P(d) (47.9 +/- 9.3 vs 31.8 +/- 6.9 ms, P < 0.01) were significantly prolonged in the obese group. P(min) was similar between the two groups. The prevalence of IAB was significantly greater in the obese subjects. Pearson's correlation analysis showed that there were positive correlations between P(d) and BMI (r = 0.6, P < 0.001), as well as between P(d) and LAD (r = 0.366, P < 0.05).

CONCLUSION

Our data suggest that obesity is associated with increased P(max) and P(d), and increased prevalence of IAB, parameters that have been associated with atrial fibrillation. The correlation of these electrocardiogram parameters with LAD indicates an association between increased BMI and atrial remodeling in Asian subjects.