Sensitivity and specificity of commonly used electrocardiographic criteria for left atrial enlargement determined by M-mode echocardiography

Comparing Artificial Intelligence-Enabled Electrocardiogram Models in Identifying Left Atrium Enlargement and Long-term Cardiovascular Risk

BACKGROUND

The role of P-wave in identifying left atrial enlargement (LAE) with the use of artificial intelligence (AI)-enabled electrocardiography (ECG) models is unclear. It is also unknown if AI-enabled single-lead ECG could be used as a diagnostic tool for LAE surveillance. We aimed to build AI-enabled P-wave and single-lead ECG models to identify LAE using sinus rhythm (SR) and non-SR ECGs, and compare the prognostic ability of severe LAE, defined as left atrial diameter ≥ 50 mm, assessed by AI-enabled ECG models vs echocardiography.

METHODS

This retrospective study used data from 382,594 consecutive adults with paired 12-lead ECG and echocardiography performed within 2 weeks of each other at Chang Gung Memorial Hospital. UNet++ was used for P-wave segmentation. ResNet-18 was used to develop deep convolutional neural network-enabled ECG models for discriminating LAE. External validation was performed with the use of data from 11,753 patients from another hospital.

RESULTS

The AI-enabled 12-lead ECG model outperformed other ECG models for classifying LAE, but the single-lead ECG models also showed excellent performance at a left atrial diameter cutoff of 50 mm. AI-enabled ECG models had excellent and fair discrimination on LAE using the SR and the non-SR data set, respectively. Severe LAE identified by AI-enabled ECG models was more predictive of future cardiovascular disease than echocardiography; however, the cumulative incidence of new-onset atrial fibrillation and heart failure was higher in patients with echocardiography-severe LAE than with AI-enabled ECG-severe LAE.

CONCLUSIONS

P-Wave plays a crucial role in discriminating LAE in AI-enabled ECG models. AI-enabled ECG models outperform echocardiography in predicting new-onset cardiovascular diseases associated with severe LAE.

Research progress on predicting atrial fibrillation recurrence after radiofrequency ablation based on electrocardiogram-related parameters

Atrial fibrillation (AF) is the most common arrhythmia. It is associated with increased stroke risks, thromboembolism, and other complications, which are great life and economic burdens for patients. In recent years, with the maturity of percutaneous catheter radiofrequency ablation (RFA) technology, it has become a first-line therapy for AF. However, some patients still experience AF recurrence (AFR) after RFA, which can cause serious consequences. Therefore, it is critical to identify appropriate parameters that are predictive of prognosis and to be able to translate the parameters easily into the clinical setting. Here, we reviewed possible predicting indicators for AFR, focusing on all the electrocardiogram indicators, such as P wave duration, PR interval and so on. It may provide valuable information for guiding clinical works.

ECG and CT for the detection of left atrial enlargement in hypertensive individuals-a population-based study

Left atrial enlargement (LAE) is associated with hypertension and an increased risk of cardiovascular morbidity and mortality. Guidelines for hypertension recommend LAE evaluation. We aimed to estimate the agreement of LAE as assessed by 12-lead electrocardiogram (ECG) and cardiac computed tomography (CT) in both the general population and hypertensive individuals. Cardiac CT and ECG were used to evaluate the presence of LAE in participants in the Copenhagen General Population Study. LAE, is defined as an LA volume above the 97.5% upper confidence limit by cardiac CT, as compared with multiple ECG criteria for LAE. A total of 3507 participants (47% males, age: 60 ± 10 years) were included. The prevalence of CT-defined LAE was 5.9% in the total population and 8.7% in participants with hypertension. In hypertensive individuals, LAE was identified by CT or by ECG in 31% with only a 4% overlap. ECG signs for anatomical LAE by CT had high negative predictive values between 93 and 96% but low sensitivity and positive predictive values. Specificity ranged from 27 to 93%. P-wave duration >120 ms was the best performing criterion, with a sensitivity of 48%, a specificity of 78%, and the highest area under the curve (0.66). We found a discrepancy in LAE prevalence when participants were assessed by CT and ECG, indicating that the two diagnostic modalities reflect different phenotypes of left atrial alterations. The diagnostic performance of ECG criteria for identifying anatomical LAE was poor.

Artificial Intelligence-Enabled Electrocardiogram Estimates Left Atrium Enlargement as a Predictor of Future Cardiovascular Disease

BACKGROUND

Left atrium enlargement (LAE) can be used as a predictor of future cardiovascular diseases, including hypertension (HTN) and atrial fibrillation (Afib). Typical electrocardiogram (ECG) changes have been reported in patients with LAE. This study developed a deep learning model (DLM)-enabled ECG system to identify patients with LAE.

METHOD

Patients who had ECG records with corresponding echocardiography (ECHO) were included. There were 101,077 ECGs, 20,510 ECGs, 7611 ECGs, and 11,753 ECGs in the development, tuning, internal validation, and external validation sets, respectively. We evaluated the performance of a DLM-enabled ECG for diagnosing LAE and explored the prognostic value of ECG-LAE for new-onset HTN, new-onset stroke (STK), new-onset mitral regurgitation (MR), and new-onset Afib.

RESULTS

The DLM-enabled ECG achieved AUCs of 0.8127/0.8176 for diagnosing mild LAE, 0.8587/0.8688 for diagnosing moderate LAE, and 0.8899/0.8990 for diagnosing severe LAE in the internal/external validation sets. Notably, ECG-LAE had higher prognostic value compared to ECHO-LAE, which had C-indices of 0.711/0.714 compared to 0.695/0.692 for new-onset HTN, 0.676/0.688 compared to 0.663/0.677 for new-onset STK, 0.696/0.695 compared to 0.676/0.673 for new-onset MR, and 0.800/0.806 compared to 0.786/0.760 for new-onset Afib in internal/external validation sets, respectively.

CONCLUSIONS

A DLM-enabled ECG could be considered as a LAE screening tool and provide better prognostic information for related cardiovascular diseases.

The Use of Machine Learning for the Care of Hypertension and Heart Failure

Machine learning (ML) is a branch of artificial intelligence that combines computer science, statistics, and decision theory to learn complex patterns from voluminous data. In the last decade, accumulating evidence has shown the utility of ML for prediction, diagnosis, and classification of hypertension and heart failure (HF). In addition, ML-enabled image analysis has potential value in assessing cardiac structure and function in an accurate, scalable, and efficient way. Considering the high burden of hypertension and HF in China and worldwide, ML may help address these challenges from different aspects. Indeed, prior studies have shown that ML can enhance each stage of patient care, from research and development, to daily clinical practice and population health. Through reviewing the published literature, the aims of the current systemic review are to summarize the utilities of ML for the care of those with hypertension and HF.

Validation of Normal P-Wave Parameters in a Large Unselected Pediatric Population of North-Western Romania: Results of the CARDIOPED Project

Aims

Reference values of the P-wave on 12 lead electrocardiograms are lacking for children and adolescents in Eastern Europe. Hence, the present study is aimed at determining the standard values of the P-wave in children and adolescents based on ECG data from the CARDIOPED project, a large-scale general population of children who participated in a screening program in Transylvania, Romania.

Methods and Results

A total of 22,411 ECGs of participants aged 6 to 18 years old from a school-based ECG screening were obtained between February 2015 and December 2015 in Transylvania, Romania. Three pediatric cardiologists manually reviewed each ECG. P-wave duration, voltage, axis, and correlation with gender and age were analyzed. The mean P-wave duration was 88 ± 10.7 ms, with a maximum duration of 128 ms. P-wave showed a positive correlation with age but did not differ between sexes. There was a positive correlation between the P-wave duration and the heart rate, but not with the body max index. The mean P-wave axis was 40.4 ± 31.1, and the mean P-wave amplitude was 0.12 ± 0.03 mV.

Conclusion

In this study on many pediatric subjects, we have provided normal limits for the P-wave in Romanian children aged 6-18 years. Our findings are useful for creating interpretation guidelines for pediatric ECG.

Automatically assessed P-wave predicts cardiac events independently of left atrial enlargement in patients with cardiovascular risks: The Japan Morning Surge-Home Blood Pressure Study

A prolonged P‐wave in electrocardiography (ECG) reflects atrial remodeling and predicts the development of atrial fibrillation (AF). The authors enrolled 810 subjects in the Japan Morning Surge Home Blood Pressure (J‐HOP) study who had ≥1 cardiovascular (CV) risk factor. The duration of P‐wave was automatically analyzed by standard 12‐lead electrocardiogram. Left atrial (LA) enlargement and left ventricular hypertrophy (LVH) were measured on echocardiography. The primary end points were fatal/nonfatal cardiac events: myocardial infarction, sudden death, and hospitalization for heart failure. The maximum P‐wave duration (Pmax) from the 12 leads was selected for analysis. The authors compared four prolonged P‐wave cutoffs (Pmax = 120, 130, 140, 150 ms) and cardiac events. LA diameter and left ventricular mass index (LVMI) were significantly associated with Pmax (r = 0.08, P = .02 and r = 0.17, P < .001, respectively). When the cutoff level was Pmax 120 or 130 ms, prolonged P‐wave was not associated with cardiac events (P = .45 and P = .10), but when a prolonged P‐wave was defined as Pmax ≥ 140 ms (n = 50) or Pmax ≥ 150 ms (n = 19), the patients in those groups had significantly higher incidence of cardiac events than others (P < .001 and P = .03). A Cox proportional hazards model including age, gender, body mass index, smoking, regular drinker, hypertension, dyslipidemia, diabetes, office systolic blood pressure, heart rate, LA enlargement, and LVH revealed that prolonged P‐wave defined as Pmax ≥ 140 ms was independently associated with cardiac events (hazard ratio: 4.23; 95% confidence interval: 1.30–13.77; P = .02). In conclusion, the automatically assessed prolonged P‐wave was associated with cardiac events independently of LA enlargement and LVH in Japanese patients with CV risks.

Association between electrocardiographic and echocardiographic atrial abnormalities and prognosis in cryptogenic stroke

BACKGROUND AND PURPOSE

The role of atrial fibrillation in cryptogenic stroke (CS) is well known. However, the usefulness of left atrial (LA) electrical and morphological abnormalities to identify more disabling strokes in sinus rhythm patients is less studied. We evaluated the association between electrocardiographic P-wave abnormalities and echocardiographic LA measures with neurological disability in patients with cryptogenic stroke.

METHODS

In a retrospective cohort, we included all consecutive hospitalized patients with cryptogenic stroke. Patients were classified according to modified Rankin scale at hospital discharge and at 3 months. LA abnormalities were identified by electrocardiographic (ECG) P-wave, axis and LA enlargement criteria, and by bidimensional echocardiograph through left atrial diameter and volume index.

RESULTS

Among the 143 patients with CS (63.4 ± 14.2 years, 53% women), 70 patients were classified as non-disabling stroke (Rankin score < 2) and 73 patients as disabling stroke (Rankin score ≥ 2) at hospital discharge. On echocardiogram, more patients with disabling stroke presented with enlarged LA volume index (48% vs. 25%; p = 0.01). This difference remained significant after adjustment for age, gender, CHA₂DS₂-VASc and NIHSS scores (p = 0.02) and even when the LA volume index was analyzed as a continuous variable (p = 0.055). Also, enlarged LA volume index was more prevalent (52% vs. 25%; p = 0.03) among those with disabling stroke at 3 months after hospital discharge. Among ECG criteria, only the LA enlargement assessed by downward deflection was more prevalent in disabling stroke.

CONCLUSION

Our study demonstrated an association between left atrial enlargement, assessed by downward deflection from ECG and volume index from echocardiogram, and more disabling cryptogenic strokes. This information could help to identify patients with poorer prognosis, or a subgroup where atrial cardiopathy may play a role in cardioembolic pathway.

Accuracy of Electrocardiography and Agreement with Echocardiography in the Diagnosis of Pediatric Left Atrial Enlargement

Left atrial enlargement (LAE) is a marker for diastolic cardiac dysfunction. Echocardiograms are considered the gold-standard for diagnosis, but given their wider access and lower economic cost, electrocardiograms (ECGs) may be useful in identifying patients who would benefit from further investigation. This study investigates the utility of ECG criteria to diagnose LAE in pediatric patients. A retrospective chart review (n = 492) was conducted in patients whose echocardiograms demonstrated LAE by left atrial indexed diameter z-score ≥2.0 and/or increased left atrial to aortic root ratio at various cutoffs (≥1.4, ≥1.6, ≥1.8). ECG criteria studied included: (1) P wave ≥110 msec, (2) P mitrale ≥40 msec, in LII (3) terminal negative P wave deflection in lead V1 > 40 msec, and (4) P/PR segment >1.6 in lead II. Sensitivity, specificity, Cohen's Kappa coefficient (κ), and ROC curves were calculated. A combination of P mitrale ≥40 msec and terminal negative P wave deflection in lead V1 > 40 msec yielded the greatest agreement (κ = 0.221, 95%CI 0.060-0.382), but all ECG criteria used to diagnose LAE had poor diagnostic value (AUC < 0.60). The present ECG criteria should not be used to diagnose LAE in the absence of an echocardiogram and findings should be considered in the context of clinical symptoms.

Evaluation of relationships between results of electrocardiography and echocardiography in 341 chimpanzees (Pan troglodytes)

OBJECTIVE

To examine potential relationships between ECG characteristics and echocardiographic measures of cardiac structure in chimpanzees (Pan troglodytes).

ANIMALS

341 chimpanzees (175 males and 166 females) from 5 sanctuaries and 2 zoological collections.

PROCEDURES

Chimpanzees were anesthetized for routine health examinations between May 2011 and July 2017 as part of the International Primate Heart Project and, during the same anesthetic events, underwent 12-lead ECG and transthoracic echocardiographic assessments. Relationships between results for ECG and those for echocardiographic measures of atrial areas, left ventricular internal diameter in diastole (LVIDd), and mean left ventricular wall thicknesses (MLVWT) were assessed with correlational analysis, then multiple linear regression analyses were used to create hierarchical models to predict cardiac structure from ECG findings.

RESULTS

Findings indicated correlations (r = -0.231 to 0.310) between results for ECG variables and echocardiographic measures. The duration and amplitude of P waves in lead II had the strongest correlations with atrial areas. The Sokolow-Lyon criteria, QRS-complex duration, and R-wave amplitude in leads V₆ and II had the strongest correlations with MLVWT, whereas the Sokolow-Lyon criteria, QRS-complex duration, and S-wave amplitude in leads V₂ and V₁ had the strongest correlations with LVIDd. However, the ECG predictive models that were generated only accounted for 17%, 7%, 11%, and 8% of the variance in the right atrial end-systolic area, left atrial end-systolic area, MLVWT, and LVIDd, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that relationships existed between ECG findings and cardiac morphology in the chimpanzees of the present study; however, further research is required to examine whether the predictive models generated can be modified to improve their clinical utility.

Interrelation Between Electrocardiographic Left Atrial Abnormality, Left Ventricular Hypertrophy, and Mortality in Participants With Hypertension

Left ventricular hypertrophy (LVH) and left atrial abnormality (LAA) are common correlated complications of hypertension. It is unclear how common for electrocardiographic markers of LAA (ECG-LAA) to coexist with ECG-LVH and how their coexistence impacts their prognostic significance. This analysis included 4,077 participants (61.2 ± 13.0 years, 51.2% women, 48.6% whites) with hypertension from the Third National Health and Nutrition Examination Survey. ECG-LVH was defined by Cornell voltage criteria. ECG-LAA was defined as deep terminal negativity of P wave in V1 >100 µV. Cox proportional hazard analysis was used to examine the associations between various combinations of ECG-LAA and ECG-LVH with all-cause mortality over a median follow-up of 14 years. The baseline prevalence of ECG-LVH, ECG-LAA, and the concomitant presence of both was 3.6%, 2.7%, and 0.34%, respectively. In a multivariable-adjusted model, mortality risk was highest in the group with concomitant ECG-LAA and ECG-LVH (hazard ratio [HR; 95% confidence interval {CI}] 2.69 [1.51, 4.80]), followed by isolated ECG-LAA (HR [95% CI] 1.63 [1.26, 2.12]), and then isolated ECG-LVH (HR [95% CI] 1.40 [1.08, 1.81]), compared with the group without ECG-LAA or ECG-LVH. Effect modification of these results by age and diabetes but not by gender or race was observed. In models with similar adjustment where ECG-LVH and ECG-LAA were entered as 2 separate variables and subsequently additionally adjusted for each other, the mortality risk was essentially unchanged for both variables. In conclusion, in participants with hypertension, ECG-LAA and ECG-LVH are independent markers of poor outcomes, and their concomitant presence carries a higher risk than either marker alone.

Electrocardiographic detection of hypertensive left atrial enlargement in the presence of obesity: re-calibration against cardiac magnetic resonance

Left atrial enlargement (LAE) has adverse prognostic implications in hypertension. We sought to determine the accuracy of five electrocardiogram (ECG) criteria for LAE in hypertension relative to cardiac magnetic resonance (CMR) gold standard and investigate the effect of concomitant obesity. One hundred and thirty consecutive patients (age: 51.4±15.1 years, 47% male, 51% obese, systolic blood pressure (BP): 171±29 mm Hg, diastolic BP: 97±15 mm Hg) referred for CMR (1.5 T) from a tertiary hypertension clinic were included. Patients with concomitant cardiac pathology were excluded. ECGs were assessed blindly for the following: (1) P-wave >110 ms, (2) P-mitrale, (3) P-wave axis <30°, (4) area of negative P-terminal force in V1 >40 ms.mm and (5) positive P-terminal force in augmented vector left (aVL) >0.5 mm. Left atrial volume ≥55 ml m^-2, measured blindly by CMR, was defined as LAE. Sensitivity, specificity, positive predictive value, negative predictive value, accuracy and area under the receiver operator curve were calculated. The prevalence of LAE by CMR was 26%. All the individual ECG LAE criteria were more specific than sensitive, with specificities ranging from 70% (P-axis <30^o) to 99% (P-mitrale). Obesity attenuated the specificity of most of the individual ECG LAE criteria. Obesity correlated with significant lower specificity (48% vs 65%, P<0.05) and a trend towards lower sensitivity (59 vs 43%, P=0.119) when ≥1 ECG LAE criteria were present. Individual ECG criteria of LAE in hypertension are specific, but not sensitive, at identifying LAE. The ECG should not be used to excluded LAE in hypertension, particularly in obese subjects.

Type 2 Diabetes Induces Prolonged P-wave Duration without Left Atrial Enlargement

Prolonged P-wave duration has been observed in diabetes. However, the underlying mechanisms remain unclear. The aim of this study was to elucidate the possible mechanisms. A rat model of type 2 diabetes mellitus (T2DM) was used. P-wave durations were obtained using surface electrocardiography and sizes of the left atrium were determined using echocardiography. Cardiac inward rectifier K(+) currents (Ik1), Na(+) currents (INa), and action potentials were recorded from isolated left atrial myocytes using patch clamp techniques. Left atrial tissue specimens were analyzed for total connexin-40 (Cx40) and connexin-43 (Cx43) expression levels on western-blots. Specimens were also analyzed for Cx40 and Cx43 distribution and interstitial fibrosis by immunofluorescent and Masson trichrome staining, respectively. The mean P-wave duration was longer in T2DM rats than in controls; however, the mean left atrial sizes of each group of rats were similar. The densities of Ik1 and INa were unchanged in T2DM rats compared to controls. The action potential duration was longer in T2DM rats, but there was no significant difference in resting membrane potential or action potential amplitude compared to controls. The expression level of Cx40 protein was significantly lower, but Cx43 was unaltered in T2DM rats. However, immunofluorescent labeling of Cx43 showed a significantly enhanced lateralization. Staining showed interstitial fibrosis was greater in T2DM atrial tissue. Prolonged P-wave duration is not dependent on the left atrial size in rats with T2DM. Dysregulation of Cx40 and Cx43 protein expression, as well as fibrosis, might partly account for the prolongation of P-wave duration in T2DM.

Novel Electrocardiographic Patterns for the Prediction of Hypertensive Disorders of Pregnancy--From Pathophysiology to Practical Implications

Hypertensive disorders of pregnancy are a major cause of poor outcome, including placental abruption, organ failure, cerebrovascular accident and disseminated intravascular coagulation. These disorders are associated with increased fetal risk of intrauterine growth restriction, intrauterine death and prematurity. Electrocardiography (ECG) recently emerged as a useful tool to evaluate cardiovascular complications during pregnancy. Specifically, left atrial abnormalities detected by standard ECG are associated with a fourfold increased risk of developing hypertensive disorders during pregnancy. The mechanisms linking left atrial abnormality on ECG with hypertensive disorders are still elusive. Several mechanisms, possibly reflected by abnormal left atrial activation on ECG, has been suggested. These include increased reactivity to angiotensin II and up-regulation of angiotensin type 1 receptors, with activation of autoantibodies targeting these receptors.

P-wave indices and atrial fibrillation: cross-cohort assessments from the Framingham Heart Study (FHS) and Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Atrial fibrillation (AF) is associated with increased morbidity. P-wave indices (PWIs) measure atrial electrical function and are associated with AF. Study of PWI has been limited to single-cohort investigations, and their contributions to risk enhancement are unknown.

METHODS

We examined PWI from the FHS and ARIC study. We calculated 10-year AF risk using adjusted Cox models. We conducted cross-cohort meta-analyses for the PWI estimates and assessed their contributions to risk discrimination (c statistic), net reclassification index, and integrated discrimination improvement.

RESULTS

After exclusions, the analysis included 3,110 FHS (62.6 ± 9.8 years, 56.9% women) and 8,254 ARIC participants (62.3 ± 5.6 years, 57.3% women, 20.3% black race). Over 10 years, 217 FHS and 458 ARIC participants developed AF. In meta-analysis, P-wave duration >120 milliseconds was significantly associated with AF (hazard ratio 1.55, 95% CI 1.29-1.85) compared with ≤120 milliseconds. P-wave area was marginally but not significantly related to AF (hazard ratio 1.31, 95% CI 0.95-1.80). P-wave terminal force was strongly associated with AF in ARIC but not FHS. P-wave indices had a limited contribution toward predictive risk beyond traditional risk factors and markers.

CONCLUSIONS

P-wave indices are intermediate phenotypes for AF. They are associated with AF in cross-cohort meta-analyses but contribute minimally toward enhancing risk prediction.

P-wave morphology is unaffected by atrial size: a study in healthy athletes

BACKGROUND

Orthogonal P-wave morphology has previously been described in different populations, but its relation to atrial size has not been studied in detail. In this study, we investigated whether atrial size affects P-wave morphology in athletes, who are known to have different degrees of atrial enlargement.

METHODS

A total of 504 healthy, male, professional soccer players were included (median age 25 years). All underwent echocardiographic and 12-lead electrocardiographic (ECG) recordings. The ECG was transformed into orthogonal leads, using the inverse Dower transform. The association between echocardiographic parameters and standard P-wave measures (i.e., orthogonal morphology, left atrial abnormality assessed as negative P-wave terminal force [PTF] in lead V1 > 0.04 mm × s, and duration) was analyzed.

RESULTS

The vast majority had either type 1 P-wave morphology (75%) (positive leads X and Y and negative lead Z) or type 2 P-wave morphology (22%) (positive leads X and Y and biphasic lead Z [negative/positive]). Left atrial enlargement (≥29 mL/m(2) ) was found in 79% on echocardiography. There was no significant difference in left atrial end-systolic volume, left or right atrial diameters, or right atrial area between individuals with different P-wave morphologies. ECG signs of left atrial abnormality were found in eight subjects, who did not have significantly larger left atrial dimensions than the rest.

CONCLUSIONS

We demonstrated that P-wave morphology does not depend on the size of the atria in young, healthy athletes, and that PTF is not a reliable marker of left atrial enlargement in the current population.

P wave area for quantitative electrocardiographic assessment of left atrial remodeling

BACKGROUND

Left atrial (LA) dilation provides a substrate for mitral regurgitation (MR) and atrial arrhythmias. ECG can screen for LA dilation but standard approaches do not assess LA geometry as a continuum, as does non-invasive imaging. This study tested ECG-quantified P wave area as an index of LA geometry.

METHODS AND RESULTS

342 patients with CAD underwent ECG and CMR within 7 (0.1±1.4) days. LA area on CMR correlated best with P wave area in ECG lead V1 (r = 0.42, p<0.001), with lesser correlations for P wave amplitude and duration. P wave area increased stepwise in relation to CMR-evidenced MR severity (p<0.001), with similar results for MR on echocardiography (performed in 86% of patients). Pulmonary arterial (PA) pressure on echo was increased by 50% among patients in the highest (45±14 mmHg) vs. the lowest (31±9 mmHg) P wave area quartile of the population. In multivariate regression, CMR and echo-specific models demonstrated P wave area to be independently associated with LA size after controlling for MR, as well as echo-evidenced PA pressure. Clinical follow-up (mean 2.4±1.9 years) demonstrated ECG and CMR to yield similar results for stratification of arrhythmic risk, with a 2.6-fold increase in risk for atrial fibrillation/flutter among patients in the top P wave area quartile of the population (CI 1.1-5.9, p = 0.02), and a 3.2-fold increase among patients in the top LA area quartile (CI 1.4-7.0, p = 0.005).

CONCLUSIONS

ECG-quantified P wave area provides an index of LA remodeling that parallels CMR-evidenced LA chamber geometry, and provides similar predictive value for stratification of atrial arrhythmic risk.

Usefulness of electrocardiographic parameters as compared with computed tomography measures of left atrial volume enlargement: from the ROMICAT trial

INTRODUCTION

The 12-lead surface electrocardiogram (ECG) is commonly used as a noninvasive modality to assess for left atrial enlargement (LAE), but data comparing ECG against cardiac computed tomography (CT) for LAE is lacking. We aimed to determine the diagnostic performance of 6 ECG criteria for LAE as compared with CT left atrial volume (LAV) and index to body surface area (LAVI) as the reference standard.

MATERIALS AND METHODS

In 339 patients (age: mean ± mean, 53 ± 12 years; 63% male), we evaluated the quantitative ECG parameters of P duration, P to PR segment ratio, P wave area, and P terminal force in lead V1. We also assessed qualitatively the morphology of bifid and biphasic P waves. Patients were stratified into top and lowest quartile of LAV and LAVI by CT.

RESULTS

Of the 6 ECG criteria, patients with P duration greater than 110 milliseconds had a 2½-fold increase likelihood of being in the top quartile of LAV (adjusted odds ratio [OR], 2.51; P = .01) and LAVI (adjusted OR, 2.74; P = .007) as measured by CT. For this ECG criterion, the sensitivity and specificity were 71% and 55% for CT LAE by LAV and 61% and 55% for LAVI. The remaining ECG parameters of LAE assessed (P to PR segment ratio, P terminal force in lead V1, P wave area, bifid, and biphasic P wave) were not associated with LAE by CT-based LAV or LAVI (all P ≥ .20).

DISCUSSION

Only P duration greater than 110 milliseconds was independently associated with LAE based on CT-derived LA volume and index. However, none of the established ECG parameters of LAE have sufficient diagnostic accuracies for predicting volumetric enlargement by CT, thus limiting its clinical utility.

The prognostic importance of isolated P-Wave abnormalities

BACKGROUND

While certain P-Wave morphologies have been associated with abnormal atrial size and either pulmonary or cardiovascular (CV) disease, their relationship to mortality and specific cause of death has not been reported.

METHODS

Analyses were performed on the first digitally recorded electrocardiogram (ECG) on 43 903 patients at the Palo Alto Veterans Administration Medical Center since 1987. After appropriate exclusions, 40 020 patients remained. Using computerized algorithms, P-wave amplitude and duration in 12 leads as well as several standardized ECG interpretations were extracted. The main outcome measures were pulmonary and CV mortality.

RESULTS

During a mean follow-up of 6 years there were 3417 CV and 1213 pulmonary deaths. After adjusting for age and heart rate in a Cox regression model, P-wave amplitude in the inferior leads was the strongest predictor of pulmonary death (hazard ratio [HR]: 3.0, 95% confidence interval [CI]: 2.3-3.9, P < .0001 for an amplitude > 2.5 mm), outperforming all other ECG criteria. The depth of P-wave inversion in leads V(1) or V(2) and P-wave duration were strong predictors of CV death (HR: 1.7, 95% CI: 1.5-2.0, P < 0.0001 for a P-wave inversion deeper than 1 mm), outperforming many previously established ECG predictors of CV death.

CONCLUSIONS

P-wave amplitude in the inferior leads is the strongest independent predictor of pulmonary death while P-wave duration and the depth of P-wave inversion in leads V(1) or V(2) significantly predict CV death. These measurements can be obtained easily and should be considered as part of clinical risk stratification.

Abnormal P-wave morphology is a predictor of atrial fibrillation development and cardiac death in MADIT II patients

BACKGROUND

Several ECG-based approaches have been shown to add value when risk-stratifying patients with congestive heart failure, but little attention has been paid to the prognostic value of abnormal atrial depolarization in this context. The aim of this study was to noninvasively analyze the atrial depolarization phase to identify markers associated with increased risk of mortality, deterioration of heart failure, and development of atrial fibrillation (AF) in a high-risk population with advanced congestive heart failure and a history of acute myocardial infarction.

METHODS

Patients included in the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) with sinus rhythm at baseline were studied (n = 802). Unfiltered and band-pass filtered signal-averaged P waves were analyzed to determine orthogonal P-wave morphology (prespecified types 1, 2, and 3/atypical), P-wave duration, and RMS20. The association between P-wave parameters and data on the clinical course and cardiac events during a mean follow-up of 20 months was analyzed.

RESULTS

P-wave duration was 139 + or - 23 ms and the RMS20 was 1.9 + or - 1.1 microV. None of these parameters was significantly associated with poor cardiac outcome or AF development. After adjustment for clinical covariates, abnormal P-wave morphology was found to be independently predictive of nonsudden cardiac death (HR 2.66; 95% CI 1.41-5.04, P = 0.0027) and AF development (HR 1.75; 95% CI 1.10-2.79, P = 0.019).

CONCLUSION

Abnormalities in P-wave morphology recorded from orthogonal leads in surface ECG are independently predictive of increased risk of nonsudden cardiac death and AF development in MADIT II patients.

Prevalence of interatrial block in healthy school-aged children: definition by P-wave duration or morphological analysis

BACKGROUND

P waves > or = 110 ms in adults and > or = 90 ms in children are considered abnormal, signifying interatrial block, particularly in the first case.

METHODS

To evaluate the prevalence of interatrial block in healthy school-aged children, we obtained 12-lead digital ECGs (Cardioperfect 1.1, CardioControl NV, Delft, The Netherlands) of 664 healthy children (349 males/315 females, age range 6-14 years old). P-wave analysis indices [mean, maximum and minimum (in the 12 leads) P-wave duration, P-wave dispersion, P-wave morphology in the derived orthogonal (X, Y, Z) leads, as well the amplitude of the maximum spatial P-wave vector] were calculated in all study participants.

RESULTS

P-wave descriptor values were: mean P-wave duration 84.9 + or - 9.5 ms, maximum P-wave duration 99.0 + or - 9.8 ms, P dispersion 32.2 + or - 12.5 ms, spatial P amplitude 182.7 + or - 69.0 microV. P-wave morphology distribution in the orthogonal leads were: Type I 478 (72.0%), Type II 178 (26.8%), Type III 1 (0.2%), indeterminate 7 (1%). Maximum P-wave duration was positively correlated to age (P < 0.001) and did not differ between sexes (P = 0.339). Using the 90-ms value as cutoff for P-wave duration, 502 (75.6%) children would be classified as having maximum P-wave duration above reference range. The 95th and the 99th percentiles were in the overall population 117 ms and 125 ms, respectively. P-wave morphology type was not in any way correlated to P-wave duration (P = 0.715).

CONCLUSIONS

Abnormal P-wave morphology signifying the presence of interatrial block is very rare in a healthy pediatric population, while widened P waves are quite common, although currently classified as abnormal.

P wave and the development of atrial fibrillation

BACKGROUND

Terminal P-wave inversion in lead V(1) representing left atrial overload has been considered a precursor of atrial fibrillation (AF).

OBJECTIVE

The purpose of this study was to determine whether this P-wave morphologic characteristic can predict the development of AF.

METHODS

Digital analysis of 12-lead ECGs was performed to enroll patients with P terminal force > or =0.06 s x 2 mm in lead V(1) from among a database of 308,391 ECG recordings. The prognostic value of ECG characteristics for developing AF was determined.

RESULTS

A total of 78 patients (mean age 52 +/- 19 years) with left atrial overload were chosen from among 102,065 patients in the database. During mean follow-up of 43 months, 15 (19%) patients developed AF (AF group) versus 63 (81%) patients who did not (non-AF group). No significant difference was noted between the AF and non-AF groups with regard to the area, duration, and amplitude of the P-wave terminal portion in lead V(1). In contrast, the area, duration, and amplitude of the P-wave initial portion in the same lead were significantly greater in the AF group than in the non-AF group (114.6 +/- 73.0 microV x ms vs 73.1 +/- 59.3 microV x ms, 42.2 +/- 12.4 ms vs 35.7 +/- 10.1 ms, and 94.0 +/- 39.9 microV vs 68.8 +/- 49.4 microV, respectively; P <.05 for each). Multivariate analysis confirmed that the area of the P-wave initial portion was independently associated with the development of AF (hazard ratio 4.02, 95% confidence interval 1.25-17.8; P = .018).

CONCLUSION

P-wave initial portion in lead V(1) was an independent risk stratifier of AF development in patients with marked left atrial overload.

Interatrial block: is it time for more attention?

Interatrial block (IAB) is defined as delayed conduction between the right and left atrium, which results in prolonged P-wave duration (> or =110 milliseconds). Interatrial block can be partial or advanced (much less common), depending on the severity of the conduction abnormality. Several studies have reported that the prevalence of IAB is more than 40% in hospital inpatients. Despite this, IAB remains largely underdiagnosed and commonly ignored. Although more investigations are needed to identify the cause of IAB, coronary artery disease and conditions related to cardiovascular disease, such as hypertension or diabetes mellitus, have been described as potential risk factors for developing IAB. Interatrial block has strong associations with multiple medical conditions including atrial fibrillation, myocardial ischemia, left atrial enlargement, and systemic emboli. Treatment modalities for IAB to preclude its consequences include pacing and medical management, in which angiotensin-converting enzyme inhibitors and angiotensin receptor blockers have given promising results. However, more interest, attention, and research for IAB is required to explore this uncertain issue thoroughly.

Left atrial abnormality by electrocardiogram predicts left ventricular hypertrophy by echocardiography in the presence of right bundle-branch block

BACKGROUND

Left ventricular hypertrophy (LVH) on the electrocardiogram (ECG) may be masked in the presence of complete right bundle-branch block (RBBB). Left bundle-branch block on the ECG is associated with LVH at autopsy in 93% of hearts studied. However, RBBB does not predict LVH and the usual ECG criteria applied for LVH may not be reliable in the presence of RBBB.

HYPOTHESIS

The study was undertaken to evaluate left atrial (LA) abnormality as a criterion for the diagnosis of LVH in the presence of RBBB.

METHODS

Left atrial abnormality in the ECG was assessed by two independent observers as a criterion of LVH in the presence of RBBB in 100 patients, and data were compared with those of 50 patients without LA abnormality.

RESULTS

Left ventricular hypertrophy was confirmed by echocardiographic determination of left ventricular (LV) mass in both groups. Observers reliably differentiated between hypertrophied and normal-sized LV in the presence of RBBB by using LA abnormality as an ECG criterion when correlated with LV mass determined by echocardiography. Observer 1 correctly detected LVH in 88% and Observer 2 in 82% of patients. False positive diagnosis was made in 12 and 18% of patients by Observers 1 and 2, respectively. Observers' performance of recognition of LA abnormality in the present study was 94%. Results showed sensitivity of 76 and 70% and specificity of 84 and 92% for Observers 1 and 2, respectively. Left ventricular mass increased significantly and was diagnostic of LVH in 92% of patients with LA abnormality. Left ventricular mass was high in 84% of patients when corrected by body surface area. LVH in the presence of RBBB by the ECG was found in only seven patients (5%) when six commonly used conventional criteria of diagnosis of LVH by ECG were employed. Regression analysis found LA abnormality to be a strong independent predictor of increased LV mass. Multiple regression analysis revealed that age, body mass index, body surface area, and frontal axis are also significant predictors of LV mass.

CONCLUSION

The results obtained by the correlation of LA abnormality by ECG and LVH by echocardiography conclude that LA abnormality by ECG was significantly diagnostic of LV hypertrophy in the presence of RBBB.

Differences in treadmill exercise tolerance parameters between patients with partial and advanced interatrial depolarization abnormality

Advanced interatrial block (aIAB) is considerably much less common than partial interatrial block (pIAB), occuring in <2% of the elderly hospitalized population. Less is, therefore, known of the true clinical burden of aIAB, particularly in relation to graded exercise. Therefore, 12 patients with aIAB and 30 patients with pIAB who performed a baseline exercise tolerance test and had a repeat test performed > or = 2 years later were included in the study. Exercise tolerance, echocardiographic findings, and major adverse cardiovascular events were compared. Left atrial size progressed at a significantly faster rate in those with aIAB. In addition, Duke Prognostic Treadmill scores were significantly lower on follow-up in those patients with aIAB. Overall, patients with aIAB had significantly greater left atrial size (48.3 +/- 9 vs 42.8 +/- 4 mm, p < 0.01) and significantly lower Duke Prognostic Treadmill scores than those with pIAB (-0.2 +/- 5 vs 4.1 +/- 4, p < 0.05). There were, however, no significant differences in the occurence of major adverse cardiovascular events. In conclusion, left atrial size progressed at a significantly faster rate but Duke Prognostic Treadmill scores were significantly lower in those with aIAB compared with patients with pIAB after > or = 2 years of follow-up. Further study is required to determine whether patients with aIAB require follow-up echocardiography and/or exercise tolerance tests for optimal risk stratification.

Risk stratification for recurrent heart failure in patients post-myocardial infarction with electrocardiographic and echocardiographic left atrial abnormality

Left atrial enlargement is predictive of cardiovascular events. The predictive power, however, of the combination of electrocardiographic (LAE-ECG) and echocardiographic left atrial enlargement (LAE-Echo) has not been extensively evaluated. We prospectively identified patients admitted with non-ST-segment elevation myocardial infarction (NSTEMI) who developed new-onset heart failure during admission. Baseline electrocardiograms obtained < or =12 months before admission were evaluated for LAE-ECG, such as prolonged P-wave duration or positive P-wave terminal force in lead V1, and in-hospital echocardiographic reports obtained < or =1 month after admission were assessed for linear, anteroposterior LAE-Echo. Follow-up was directed toward pertinent cardiovascular events and death. Of the 462 patients with NSTEMI, 108 developed new-onset heart failure (23%); 71 patients had LAE-Echo. Follow-up was 23.2 months (mean 22.1 months). Although in-hospital (early) cardiovascular complications (other than heart failure) were not significantly higher in patients with LAE-Echo, these patients demonstrated more postdischarge (late) cardiovascular complications, predominantly recurrent heart failure. In addition, those with a combination of LAE-Echo and LAE-ECG demonstrated significantly higher recurrence of heart failure (hazard ratio 1.52, 95% confidence interval 1.12 to 4.35; p = 0.02 for interatrial conduction delay, and hazard ratio 1.07, 95% confidence interval 1.01 to 3.27 for P-wave terminal force in lead V1; p = 0.03) and increased mortality compared with those with LAE-Echo alone. In conclusion, our data suggest that a combination of electrical and mechanical left atrial dysfunction is significantly more predictive of increased cardiovascular events and mortality compared with left atrial mechanical dysfunction alone.

Higher prevalence of cardiovascular events among patients with abnormal atrial depolarization and coronary artery disease at 18 months' post-exercise tolerance testing

Abnormal atrial depolarization, denoted as interatrial block (IAB; P wave >110 ms), is associated with myocardial ischemia during exercise. The authors conducted an 18-month follow-up for cardiovascular events in 31 consecutive patients with IAB and 60 controls without IAB at rest; participants had coronary artery disease and hypertension and had undergone coronary angiography following positive exercise tolerance test (ETT) results. Atrial fibrillation and need for repeat ETT and coronary artery revascularization were significant with IAB (77.4% vs 20%; P<.001). In patients with such events, IAB, left atrial dilatation, left ventricular hypertrophy, increased left ventricular end-diastolic volume, poorer Duke prognostic treadmill (DPT) scores, and significant coronary artery stenoses were predominant. IAB (hazard ratio [HR], 4.9; 95% confidence interval [CI], 1.3-19.7; P=.02) and DPT scores (HR, 0.84; 95% CI, 0.72-0.98; P=.03) were independently associated with these events. At 18 months' follow-up, IAB at rest was associated with cardiovascular events among those with known coronary artery disease and hypertension.

Accuracy of electrocardiographic criteria for atrial enlargement: validation with cardiovascular magnetic resonance

BACKGROUND

Anatomic atrial enlargement is associated with significant morbidity and mortality. However, atrial enlargement may not correlate with clinical measures such as electrocardiographic (ECG) criteria. Past studies correlating ECG criteria with anatomic measures mainly used inferior M-mode or two-dimensional echocardiographic data. We sought to determine the accuracy of the ECG to predict anatomic atrial enlargement as determined by volumetric cardiovascular magnetic resonance (CMR).

METHODS

ECG criteria for left (LAE) and right atrial enlargement (RAE) were compared to CMR atrial volume index measurements for 275 consecutive subjects referred for CMR (67% males, 51 +/- 14 years). ECG criteria for LAE and RAE were assessed by an expert observer blinded to CMR data. Atrial volume index was computed using the biplane area-length method.

RESULTS

The prevalence of CMR LAE and RAE was 28% and 11%, respectively, and by any ECG criteria was 82% and 5%, respectively. Though nonspecific, the presence of at least one ECG criteria for LAE was 90% sensitive for CMR LAE. The individual criteria P mitrale, P wave axis < 30 degrees , and negative P terminal force in V1 (NPTF-V1) > 0.04s.mm were 88-99% specific although not sensitive for CMR LAE. ECG was insensitive but 96-100% specific for CMR RAE.

CONCLUSION

The presence of at least one ECG criteria for LAE is sensitive but not specific for anatomic LAE. Individual criteria for LAE, including P mitrale, P wave axis < 30 degrees , or NPTF-V1 > 0.04s.mm are highly specific, though not sensitive. ECG is highly specific but insensitive for RAE. Individual ECG P wave changes do not reliably both detect and predict anatomic atrial enlargement.

Differences in echocardiographic indices between patients with partial and advanced interatrial conduction delay

Partial interatrial block (IAB) (P wave > or =110 ms) is a marker of left atrial abnormality. A similar association among patients with advanced IAB (biphasic P waves > or =110 ms in leads II, III, and aVF) is unknown. The authors screened 27 consecutive patients for advanced IAB with transthoracic echocardiograms (TTEs). Of those, 19 who had repeat TTEs after 2 years formed our study cohort. The authors used 44 consecutive controls with partial IAB who had been similarly screened and had follow-up TTEs 2 years apart. TTE parameters were comparable at baseline between groups but were expectedly different on follow-up. When change (delta value) in these indices was compared, however, only left atrial dimension remained significant (advanced 0.07+/-0.06 mm vs partial IAB 0.03+/-0.06 mm; P=.03). Further study over a longer duration is warranted to ascertain if advanced IAB patients would benefit from follow-up noninvasive cardiac imaging for appropriate risk stratification.

Quantitative estimation of left atrial linear dimension on a transthoracic echocardiogram using an electrocardiographic formulaic assessment

A proportionate and incremental association between left atrial (LA) dilatation on a transthoracic echocardiogram (TTE) and increasing severity in abnormal atrial depolarization can be described by the regression formula: LA dimension in parasternal long-axis view (in millimeters) = 2.47 + 0.29 [P-wave duration (in milliseconds)]. However, prospective testing of this formula for LA quantification with comparison to other TTE indexes is lacking. We prospectively obtained 12-lead electrocardiograms for 72 consecutive patients before individual, nonemergent TTE assessment. P waves were assessed independently to the nearest 10 ms for application of the formula with a Bland-Altman plot. P-wave durations were obtained specifically from lead II and also from any lead that yielded the widest measurement. There was a strong formulaic correlation with LA measurement by TTE (p <0.00000001; r = 0.662), irrespective of electrocardiographic lead used. However, as the measurement difference increased between that in any lead and lead II, correlation strength increased. Correlation was not significantly affected by commonly measured electrocardiographic and TTE indexes, such as, PR interval, QRS complex, and left ventricular end-diastolic as well as systolic dimensions, after adjustment for these variables. Moreover, when the P-wave axis remained within the normal range, the correlation strength increased. The Bland-Altman plot also showed good agreement of LA dimension assessment between formulaic estimation and TTE measurement. In conclusion, there is good agreement and correlation between formulaic estimation and that of TTE for measurement of LA linear dimension. The LA regression formula is an indirect asset that could perhaps supplement LA quantification on TTE in certain circumstances.

Association of P-wave duration, dispersion, and terminal force in relation to P-wave axis among outpatients

BACKGROUND

While P-wave duration (P-dur) and dispersion (P-disp) could both reflect fractionated and inhomogeneous propagation of sinus cardiac impulses, and may therefore be associated with each other, a clear relationship has not been extensively studied. We studied these markers as well as the significance of P-wave terminal force in lead V1 (PTFV1) in relation to the P-wave axis (P-axis).

METHODS

We appraised our previously studied sample of 500 consecutively numbered, otherwise unselected, electrocardiograms (ECGs) of outpatients from the University of Massachusetts, Worcester, Massachusetts, for the foregoing P-wave characteristics. P-disp, defined as the difference of the duration between the widest and narrowest P wave, and the greatest P-dur after a 12-lead ECG search, was measured manually to the nearest 10 ms. PTFV1 was considered positive when > or = 40 mm2 terminal deflection was present on biphasic P waves on lead V1. Normal P-axis was considered 0 degrees to +75 degrees by manually constructing the mean frontal plane electrical P-axis from standard limb leads.

RESULTS

After excluding those with atrial arrhythmias, paced rhythms, errors in lead placement, P waves with low amplitude or overall technically poor tracing, 428 ECGs formed our final sample. P-dur was strongly associated with P-disp (P < 0.0001), but the correlation remained weak (r = 0.42). Overall, P-dur was not significantly associated with P-axis but when divided into tertiles and quintiles, the significance was evident within the range of the normal P-axis, particularly 0 degrees to +60 degrees (P < 0.0001). In a subanalysis of 380 ECGs that had appreciable biphasic P waves on lead V1, PTFV1 was noted on 178 (47%) ECGs and was significantly associated with P-dur (P < 0.0001), P-disp (P < 0.0001), and P-axis (P = 002). When considering P-axis in tertiles and quintiles, P-dur was greater in patients with a positive PTFV1 and significant within the normal range of the P-axis, especially from 0 degrees to +60 degrees .

CONCLUSION

P-dur, P-disp, and PTFV1 appear to share a significant tripartite association in relation to the normal P-axis, particularly when P-axis ranges 0 degrees to +60 degrees . Therefore, for optimal clinical assessment, these markers should be evaluated in relation to the normal P-axis.

High prevalence of widened P waves among pediatric patients in 2 separate hospitals

INTRODUCTION

In adults, P waves of 110 milliseconds or longer are often associated with significant disease. In the pediatric population, however, cutoffs for P-wave durations are naturally lower but could vary physiologically with age because of increasing heart mass. We appraised if age-proportionate increase in P-wave duration does indeed occur in both hospitalized infants and children and also investigated the prevalence of widened P-wave durations using currently accepted "normal" cutoffs (</=70 milliseconds for infants and </=90 milliseconds for children).

METHODS

We consecutively obtained 12-lead electrocardiograms of infants and children aged up to 16 years (range, 0.1-16 years; mean +/- SD, 10.1 +/- 5.2 years; male, 46.9%) who presented through the emergency department for nonacute, noncardiac conditions at the Nassau University Medical Center (NUMC), East Meadow, NY, and Saint Vincent Hospital (SVH), Worcester, MA, from January to May 2006. Electrocardiograms were then evaluated for the greatest P-wave duration in every lead to the nearest 10 milliseconds using a calibrated magnifying graticule on a blinded, single read.

RESULTS

The study sample consisted of 96 nonacute pediatric patients: infants and children from NUMC (age, 0.1-16 years; mean +/- SD, 9.1 +/- 5.4 years; male, 46.6%) and children from SVH (age, 6-16 years; mean +/- SD, 13.1 +/- 2.5 years; male, 47.8%). Prolonged P waves longer than 70 milliseconds were present in 3 (23%) of the 13 NUMC infants, whereas prolonged P waves longer than 90 milliseconds were observed in 16 (27%) of the 60 NUMC children and 7 (30%) of the 23 SVH children. Linear regression analysis revealed that age was the sole predictor of increasing P-wave durations on any lead [age = -15.33 + 0.30 (P-wave duration [milliseconds]); r(2) = 0.44]. Moreover, there was a significant increase in P-wave duration for patients aged 10 years or older, where a notable step-up in such measurements was observed.

CONCLUSION

P-wave duration is significantly associated with age among hospitalized children as well as infants, where particular increase occurs at 10 years of age or older. General pediatricians and, more importantly, pediatric cardiologists, need to be more vigilant in using appropriate age-based P-wave cutoffs when assessing interatrial conduction in this population.

Association of myocardial ischemia and coronary angiographic lesions with increased left atrial dimension during exercise tolerance tests among patients without known coronary heart disease

The association between left atrial (LA) dilation and fundamental exercise parameters has not shared equal extensive investigation as its clinical correlate, interatrial block (IAB; P waves > or =110 ms). We prospectively identified 94 consecutive patients with LA dilation on 2-dimensional transthoracic echocardiography but without atrioventricular valvular disease, hypertension, or coronary artery disease who had undergone coronary angiography after exercise tolerance tests (ETTs) for assessment of new coronary artery disease. Duke prognostic treadmill (DPT) scores were calculated and exercise capacity was expressed as METs of workload achieved. We appraised the cohort for common co-morbidities, IAB on electrocardiography at rest, and exercise-induced P-wave increments (divided into 20-ms quintiles). IAB (67% vs 34%, p = 0.002) and increased LA dimension (48 +/- 6 vs 45 +/- 5 mm, p = 0.01) were associated in patients with >70% coronary artery diameter stenoses and were equally reflected by positive ETT results (79.5% vs 20%, p <0.001), decreased METs (11.43 + [-0.60 x LA size (millimeters)], r(2) = 0.04), and lower DPT scores (35.23 + [-0.70 x LA size (millimeters)], r(2) = 0.73). Incremental P-wave change was associated with lower METs and DPT scores but with positive ETT results and significant coronary artery stenoses (p for trend <0.001). LA dimension was largest in the highest quintile (>60 ms) of P-wave change (p for trend <0.001). In conclusion, increased LA dimension is significantly associated with myocardial ischemia during ETT and is reflected by lower METs and DPT scores and a higher incidence of coronary artery diameter stenoses >70% in patients matched by age-, gender-, and LA size without preexisting coronary artery disease.

Interatrial block: a novel risk factor for embolic stroke?

BACKGROUND

Interatrial block (IAB; P wave > or = 110 ms) is highly prevalent and is strongly associated with atrial tachyarrhythmias and left atrial dysfunction, making it a potential embolic risk.

METHODS AND RESULTS

Among 293 neurological admissions over 2 years, 85 patients were diagnosed with embolic strokes and 208 with nonembolic strokes. Patients were then matched for stroke risk factors and evaluated for IAB. Eighty-eight percent of probable embolic stroke patients showed sinus rhythm, demonstrating a 61% IAB prevalence. Only hypertension (P < 0.001; r = 0.3) and IAB (P < 0.006; r = 0.2) were significant and directly correlated.

CONCLUSION

IAB could indeed be a novel risk for embolic strokes and further investigation is warranted.

Relation of electrocardiographic criteria for left atrial enlargement to two-dimensional echocardiographic left atrial volume measurements

Left atrial (LA) enlargement by 2-dimensional (2-D) echocardiography predicts adverse cardiovascular outcomes. Electrocardiographic (ECG) criteria for LA enlargement are based on M-mode echocardiographic LA diameter, which is inferior to 2-D-derived LA volumes. This study compared established ECG criteria for LA enlargement with atrial volume obtained by 2-D echocardiography to determine if traditional ECG criteria accurately represent LA chamber enlargement, therefore offering a low-cost screening tool. A total of 261 randomly selected patients who underwent electrocardiography and 2-D echocardiography were enrolled. ECG parameters and electronically derived P-wave medians were analyzed with electronic calipers for maximal accuracy. LA volumes by 2-D echocardiography were measured with Simpson's method of discs, with enlargement defined as 32 ml/m(2). Sensitivity and specificity tables and receiver-operating characteristic curves were constructed for each criterion. Univariate and multivariate analyses were performed for predictors of 2-D echocardiographic LA enlargement. LA enlargement was present in 43% of patients. ECG P-wave duration was the most sensitive for the detection of LA enlargement (69%) but had low specificity (49%). Conversely, a biphasic P wave was the most specific (92%) but had low sensitivity (12%). The maximum area under the receiver-operating characteristic curve for any criterion was 0.64, too low to be of clinical utility. In conclusion, established ECG criteria for LA enlargement do not reliably reflect LA enlargement and lack sufficient predictive value to be useful clinically. These results suggest that P-wave abnormalities should be noted as nonspecific LA abnormalities, with the term "LA enlargement" no longer used.

Specific electrocardiographic markers of P-wave morphology in interatrial block

BACKGROUND

Interatrial block (IAB; P waves >/= 110 milliseconds), the conduction delay between the right (RA) and left atrium (LA), is depicted on the electrocardiogram (ECG) as prolonged, often bifid ("notched"), P waves with distinguishable RA and LA components. Although electrophysiologic (EP) studies give some insight on how RA and LA components are depicted on the surface ECG in normal conduction, few if at all any, have conclusively demonstrated this correlation with IAB. Using existing EP knowledge, we investigated if such P-wave markers on bedside ECGs exist in IAB and appraised their utility in IAB recognition.

METHODS

We reviewed the medical records of patients admitted to a general hospital from December 1, 2004, to December 15, 2004. Of those, 151 patients had been admitted for nonacute presentations and were screened with 12-lead ECGs. Thirty-eight ECGs were excluded for nonsinus and paced rhythms, severe motion artifact, errors in lead placement, absence of adequate patient identification, and duplicate patient admissions after discharge. The remaining 113 ECGs were then evaluated for IAB. Sixty-three patients who did not have IAB formed the control (group A), whereas of the remaining 50 patients with IAB, 24 who had past ECGs for comparison formed group B1 and 26 without past ECGs formed group B2. Groups were compared for common clinical comorbidities, whereas sensitivity and specificity were calculated for significant P-wave markers. P values were also calculated, with a value of <.05 considered significant.

RESULTS

Clinical characteristics of patients in all groups were statistically comparable. Overall, almost all P waves in patients with IAB (groups 1 and 2) appeared "notched" (94%, P < .0001; sensitivity, 75%; specificity, 94% for IAB recognition; positive predictive value, 94%). P-wave RA components were commonly depicted as "domes," whereas their LA counterparts formed "spikes" (48%, P < .0001; sensitivity 96%; specificity, 70% for IAB recognition). When groups B1 and B2 were compared with increased accuracy, more P waves in group B1 were noted to have notches and had easily discernible RA and LA components; often, the RA duration is longer than the LA duration. In addition, more "dome-and-spike" complexes could be determined when past ECGs were present for comparison. These markers could be found on any bedside ECG lead in IAB but were predominant on leads II and V3 to V6.

CONCLUSIONS

Specific noninvasive surface markers such as P-wave "dome-and-spike" complexes and "notches" in any lead (predominantly leads II and V3-V6) on the bedside ECG could alert clinicians to measure P waves and so identify IAB.

Prevalence of Interatrial Block in the Program of All-Inclusive Care for the Elderly (PACE)

Interatrial block (IAB) (P wave > or =110 milliseconds) is a potent correlate of atrial tachyarrhythmias, left atrial electromechanical dysfunction, and embolism. IAB has been demonstrated to be highly prevalent in the general hospital population, but no investigation has addressed this in the elderly community outside the hospital. We appraised the prevalence of IAB in a service of the Program of All-Inclusive Care for the Elderly (PACE), the Elder Service Plan (ESP). Of the 202 ESP members in Worcester, MA, 167 (ages 61-103 years; female 81.4%) who had current 12-lead electrocardiograms were evaluated for IAB, and an age-based comparison was made between those with and without IAB. Of those patients with current electrocardiograms, 148 (88.6%) showed sinus rhythm and 72 (48.6%) depicted IAB: 20% in patients aged 60-69 years, 39.5% aged 70-79 years, 56.8% aged 80-89 years, and 50% in those 90 years and older. Given its sequelae of anatomic and pathophysiologic consequences, prompt recognition of IAB in a high-risk group such as that in the PACE community (48.6% prevalence) is important, especially for anticipation of atrial fibrillation and possible embolism.

Potential clinical correlates and risk factors for interatrial block

BACKGROUND

Interatrial block (IAB; P wave > or =110 ms) denotes a conduction delay between the atria, is strongly associated with atrial tachyarrhythmias, left atrial enlargement, left atrial electromechanical dysfunction, and is a risk for embolism. Despite this, potential risk factors for IAB have not been clearly defined.

METHODS

Patients admitted via the Emergency Department for nonacute medical reasons to the nontelemetry general medical floors of a tertiary care general hospital from October to November 2004 were screened for sinus rhythm on electrocardiograms. Four hundred and four patients who met our criteria were then evaluated for IAB on respective electrocardiograms. All patients were subsequently compared for common diseases as well as coronary artery disease (CAD) risk factors and divided into two groups, those with IAB and those without (control). Mean age +/- standard deviation, odds ratios (ORs), 95% confidence intervals (CIs), r values, and p values were calculated. p values <0.05 were considered statistically significant.

RESULTS

From the sample (n = 404), 182 patients had IAB (45%; mean age 64.32 +/- 19.27 years; males 51.6%) while 222 did not (control). CAD (OR 3.150, 95% CI 2.05-4.83; p < 0.001, r = 0.3), hypertension (OR 2.918, 95% CI 1.85-4.60; p < 0.001, r = 0.2), diabetes mellitus (OR 2.542, 95% CI 1.62-3.97; p < 0.001, r = 0.1), and hypercholesterolemia (OR 1.823, 95% CI 1.22-2.74; p = 0.004, r = 0.2) were significant risk factors and correlates for IAB. Multivariate analysis using stepwise linear regression revealed these factors as direct correlates of IAB.

CONCLUSION

CAD, hypertension, diabetes mellitus and hypercholesterolemia appear to be risk factors for IAB in general hospital patients admitted for nonacute reasons. Considering the known sequelae of IAB, awareness of its associations with such risk factors could be important for patient risk stratification.

Peripheral Edema Masks the Diagnoses of P Pulmonale, P Mitrale, and Biatrial Abnormality: Clinical Implications for Patients With Heart Failure

Peripheral edema (PED) impacts the size of the electrocardiogram, attenuating the amplitude and duration of QRS complexes and P waves. Diagnostic configurations of P pulmonale (Pp), P mitrale (Pm), and biatrial abnormality (Pb) are based on measurements of the amplitude and duration of the P waves. To investigate whether PED masks the diagnoses of Pp, Pm, and Pb, 15 patients (nine who suffered PED and six who did not gain weight during hospitalization, who served as controls) were studied. Of nine patients with PED, one had Pp, four had Pm, and four had Pb on admission, but such configurations were abolished after development of PED, except in one patient with Pm. Of six controls, one patient had Pp, three had Pm, and two had Pb, both on admission and at discharge. There was no difference in sex (p=0.61) or age (p=0.27) between the patients with PED and the controls; however, patients with PED were sicker and eventually died, while none of the controls did so. Electrocardiographic atrial abnormalities can be masked by PED, resulting from the attenuation of P waves and mediated by a decrease in the electrical impedance of the body's volume conductor due to water overload. These have clinical implications for patients with heart failure.

Correlation of left atrial size with p-wave duration in interatrial block

BACKGROUND

Interatrial block (IAB) [P-wave duration > or = 110 ms] is associated with left atrial (LA) enlargement (LAE) and pathophysiologic derangements that result in atrial tachyarrhythmias, LA electromechanical dysfunction, and embolism. However, there has been no study addressing the direct correlation of P-wave duration in IAB and LAE.

METHODS

One hundred eighty-one consecutive patients who were admitted to a tertiary care teaching hospital over 5 consecutive days were screened for past transthoracic echocardiogram evaluations and were then matched with ECGs done within 10 days of these echocardiographic investigations. ECGs were evaluated for presence of IAB, and patients were subsequently classified into two groups: control patients and patients with IAB. Patients were also matched for common comorbidities. Mean, SD of age, Pearson correlation coefficient (r), p values, and multivariate and linear regression analyses were analyzed for the investigated variables of LA size, left ventricular hypertrophy (LVH), posterior wall thickness, septal thickness, and P-wave duration.

RESULTS

From the sample (n = 66; mean age +/- SD, 71.3 +/- 13.7; female gender, 48.5%), the mean LA size in the control group was 36.7 +/- 4.01 mm and for the group of patients with IAB (n = 38) was 42.2 +/- 7.25 mm (p = 0.004). Linear regression analysis revealed that P-wave duration was significantly correlated with LA size (p = 0.0002, r = 0.606).

CONCLUSIONS

Degree of conduction delay in IAB (P-wave duration) is an independent, direct correlate of LAE, and the regression equation (LA size [in millimeters] = 2.47 +/- 0.29 x P-wave duration [in milliseconds]) could be used to estimate LAE.

P-wave morphology correlation with left atrial volumes assessed by 2-dimensional echocardiography

To correlate prespecified P-wave morphologies with echocardiographically derived left atrial volumes (LAVs), we studied a convenience sample of 71 patients with predominantly normal left ventricular systolic function (mean ejection fraction = 58.2% +/- 6.6%) who underwent concurrent 2-dimensional echocardiogram and 12-lead electrocardiogram. Left atrial volume was calculated from apical end-systolic images by the biplane method of disks and was indexed for body surface area (BSA). Electrocardiograms were assessed manually with calipers, measuring leading edge to leading edge. Patients included 34 men and 37 women with a mean age of 53 +/- 14 years. P-wave duration/PR-segment duration in lead II and depth and duration of terminal P wave in lead V1 (P terminal force) correlate poorly with LAV and provided only modest predictive power (area under receiver operating characteristic curve = 0.466-0.619 and r = 0.30-0.42, P = .014-.021). Total P-wave duration in lead II correlated moderately (r = 0.47, P < .001) and predicted LAV (LAV/BSA = 8.0 + 0.2 [P-wave duration in lead II]), as did P-wave area in lead II (r = 0.49, P < .001) (LAV/BSA = 18.6 + 1.7 [P-wave duration in lead II]). The 4 P-wave morphologies were found to be poorly sensitive but highly specific for left atrial enlargement.