Significance of signal-averaged P-wave changes during exercise in patients with coronary artery disease and correlation with angiographic findings

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.

Prognostic of Interatrial Block after an Acute ST-Segment Elevation Myocardial Infarction

BACKGROUND

The influence of interatrial block (IAB) in the prognosis after an acute ST-segment elevation myocardial infarction (STEMI) is unknown.

OBJECTIVES

To assess the prognostic impact of IAB after an acute STEMI regarding long-term mortality, development of atrial fibrillation, and stroke.

METHODS

Registry of 972 consecutive patients with STEMI and sinus rhythm at discharge, with a long-term follow-up (49.6 ± 24.9 months). P wave duration was analyzed using digital calipers, and patients were divided into three groups: normal P wave duration (<120 ms), partial IAB (pIAB) (P wave ≥120 ms and positive in inferior leads), and advanced IAB (aIAB) (P wave ≥120 ms plus biphasic [positive/negative] morphology in inferior leads).

RESULTS

Mean age was 62.6 ± 13.5 years. A total of 708 patients had normal P wave (72.8%), 207 pIAB (21.3%), and 57 aIAB (5.9%). Patients with aIAB were older (mean age 73 years) than the rest (62 years in the other two groups, p < 0.001). They also had a higher rate of hypertension (70 vs. 55% in pIAB and 49% in normal P wave, p = 0.006) and higher all-cause mortality (26.3 vs. 12.6% in pIAB and 10.3% in normal P wave, p = 0.001). However, multivariable analysis did not show an independent association between IAB and prognosis.

CONCLUSION

About a quarter of patients discharged in sinus rhythm after an acute STEMI have IAB. Patients with aIAB have a poor prognosis, although this is explained mainly by the association of aIAB with age and other variables.

P wave detection and delineation in the ECG based on the phase free stationary wavelet transform and using intracardiac atrial electrograms as reference

Robust and exact automatic P wave detection and delineation in the electrocardiogram (ECG) is still an interesting but challenging research topic. The early prognosis of cardiac afflictions such as atrial fibrillation and the response of a patient to a given treatment is believed to improve if the P wave is carefully analyzed during sinus rhythm. Manual annotation of the signals is a tedious and subjective task. Its correctness depends on the experience of the annotator, quality of the signal, and ECG lead. In this work, we present a wavelet-based algorithm to detect and delineate P waves in individual ECG leads. We evaluated a large group of commonly used wavelets and frequency bands (wavelet levels) and introduced a special phase free wavelet transformation. The local extrema of the transformed signals are directly related to the delineating points of the P wave. First, the algorithm was studied using synthetic signals. Then, the optimal parameter configuration was found using intracardiac electrograms and surface ECGs measured simultaneously. The reverse biorthogonal wavelet 3.3 was found to be optimal for this application. In the end, the method was validated using the QT database from PhysioNet. We showed that the algorithm works more accurately and more robustly than other methods presented in literature. The validation study delivered an average delineation error of the P wave onset of -0.32±12.41 ms when compared to manual annotations. In conclusion, the algorithm is suitable for handling varying P wave shapes and low signal-to-noise ratios.

Effect of Slow Coronary Flow on P-Wave Duration and Dispersion

The slow coronary flow (SCF) phenomenon is often considered to be an incidental angiographic finding; however, several reports have shown it to be associated with cardiac events. In this study we aimed to assess P-wave duration and dispersion (PWD) in patients with SCF and to compare it with that of healthy subjects. Thus, 40 patients with angiographically proven SCF and otherwise normal coronary arteries (group 1) and 36 sex-age-matched healthy subjects (group 2) were included in this study. A 12-lead surface ECG, recorded at a paper speed of 50-mm/s and 2 mV/cm standardization, was obtained from each subject. P-wave duration was measured manually by use of a caliper. The difference between the maximum (Pmax) and minimum P (Pmin)-wave duration was calculated and defined as PWD. All subjects had undergone echocardiographic examination to exclude valvular disorders and wall motion abnormalities. There was no significant difference between the 2 groups in demographies of age, sex, heart rate, or blood pressure. Maximum P-wave duration and PWD were significantly higher in group 1 than in group 2 (120 ±7 vs 115 ±5, p = 0.003; 44 ±12 vs 38 ±9, p = 0.01, respectively). However, there was no significant difference in Pmin duration (75 ±9 vs 78 ±7, p = 0.4). In conclusion; SCF and otherwise normal epicardial coronary artery was found to be associated with prolonged P-wave duration and increased PWD. This may result from microvascular ischemia and/or altered autonomic control of cardiovascular system observed in this group of patients.

Electrophysiological Mechanisms of Bayés Syndrome: Insights from Clinical and Mouse Studies

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.

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.

Enhanced recognition of ischemia by three variable analysis of the exercise stress test

BACKGROUND

ECG ST-segment deviations have been the standard measure of coronary artery disease (CAD) during the exercise stress test (EST). Our past research has shown other ECG variables to be significant in EST. This study evaluates the benefit of routinely combining these variables in the detection of CAD.

METHODS

Sequential patients (n = 439) with suspected CAD referred for EST had their cases reviewed. Clinical and ECG variables were associated with myocardial perfusion imaging (MPI) scintigrams used to detect ischemia during maximum EST.

RESULTS

An increase in P-wave duration was the most sensitive predictor of ischemia with a sensitivity of 64.3%, a specificity of 86.5%, and a positive predictive power (PPP) of 57.8%. ST elevation ≥ 1 mm in lead AVR had a sensitivity of 53.1%, a specificity of 78.3%, and a PPP of 41.3%. ST depression ≥ 1 mm in leads V₄-V₆ had a sensitivity of 11.2%, a specificity of 94.7%, and a PPP of 37.9%. When these variables were combined, specificity and PPP increased to 100% (p < 0.001).

CONCLUSIONS

EST evaluation solely by ST deviation fails to identify a significant portion of ischemic cases. Combinations of ΔPWD, ST elevation in AVR, and ST depression improved the identification of ischemia.

Usefulness of p-wave duration to identify myocardial ischemia during exercise testing

It is well recognized that ST-segment depression is due to subendocardial ischemia secondary to an increase in left ventricular end-diastolic pressure. The increase in left ventricular end-diastolic pressure is associated with increased left atrial pressure, resulting in left atrial wall distension that contributes to increasing P-wave duration (PWD). The objective of this study was to determine if PWD measured in leads II and V(5) during maximum exercise stress testing could be a reliable predictor of myocardial ischemia. Patients with suspected coronary disease underwent maximum exercise stress testing with myocardial perfusion imaging. PWD was measured using leads II and V(5) at rest and after exercise, with electrocardiographic complexes magnified 4 times (100 mm/s, 40 mm/mV). The change in PWD was calculated as Delta = PWD(recovery) - PWD(rest). DeltaPWD and ST-segment changes were related to the absence or presence of ischemia (localized reversible perfusion abnormalities) on myocardial perfusion imaging scans. DeltaPWD had sensitivity of 72%, specificity of 82%, negative predictive power (NPP) of 90%, and positive predictive power of 57%. ST-segment change had sensitivity of 34%, specificity of 87%, NPP of 80%, and positive predictive power of 47%. When DeltaPWD and ST changes were combined, sensitivity increased to 79% and NPP increased to 91%. In conclusion, DeltaPWD outperformed ST-segment changes in predicting myocardial ischemia on myocardial perfusion imaging scans. Furthermore, when DeltaPWD and ST-segment changes were combined, sensitivity and NPP were also significantly increased. In this study population, measuring DeltaPWD substantially increased the diagnostic value of maximum exercise stress testing.

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.

Effect of treadmill exercise testing on P wave duration and dispersion in patients with isolated myocardial bridging

Several previous studies suggest that myocardial bridging (MB) is associated with ischemia and rhythm disturbances. We sought to examine exercise-induced changes in P wave duration and dispersion (PWD), the markers of atrial conduction abnormalities in patients with isolated MB of left anterior descending artery (LAD) and control subjects. Eighteen patients with MB of LAD (group-I) and 22 subjects with angiographically demonstrated normal coronary arteries (group-II) underwent treadmill exercise testing. Before and after exercise ECG was recorded at a paper speed of 50 mm/s. The change in maximum and minimum P wave duration was measured manually and difference between two values was defined as PWD. There was no difference between two groups in terms of demographic properties. Baseline maximum and minimum P wave duration and PWD durations were similar in both groups and they did not change after exercise. (Group-I: before and after test; 114 +/- 10 vs. 114 +/- 9, 66 +/- 13 vs. 67 +/- 10, and 47 +/- 9 vs. 45 +/- 13 ms, P > 0.05, group-II; 113 +/- 9 vs. 115 +/- 8, 68 +/- 11 vs. 68 +/- 11, 45 +/- 11 vs. 48 +/- 15 ms for each, respectively). In addition there was no significant correlation between PWD and P wave duration and echocardiographic variables. In patients with MB of LAD, PWD and P wave duration were not different than healthy subjects and treadmill exercise testing did not induce atrial conduction abnormalities in both groups.

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.

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.

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.

Limited utility of interatrial block in predicting ischemia on coronary angiography in patients with suboptimal exercise performance

INTRODUCTION

Interatrial block (P waves > or = 110 ms) is thought to be associated with underlying myocardial ischemia during exercise but has not been extensively investigated in patients with suboptimal or borderline exercise tolerance tests (< 3 min exercise). We utilized coronary angiography to assess the relationship of both, the resting baseline and exercise induced increase in P-wave duration with coronary artery disease among patients who had undergone such tests.

METHODS

We prospectively identified 51 consecutive patients with interatrial block who had coronary artery disease and hypertension but not atrioventricular valvular heart disease, and had undergone coronary angiography to evaluate myocardial ischemia after a suboptimal exercise tolerance test. A control group of 64 consecutive exercise tolerance test patients with similar preliminary characteristics but without interatrial block at rest was used for comparison. Patients from both groups were then appraised for significant obstructive lesions (> 70%) on coronary angiography that were suggestive of myocardial ischemia.

RESULTS

Obstructive coronary artery lesions suggestive of myocardial ischemia were more frequent among interatrial block patients but this was not statistically significant (p=0.25). However, change in P-wave duration of > 20 ms occurred more frequently in interatrial block patients in the presence of a positive exercise tolerance test. Among patients without interatrial block at baseline, more patients who developed new interatrial block had significant disease on coronary angiography.

CONCLUSION

The utility of using interatrial block toward predicting myocardial ischemia among patients with suboptimal exercise tolerance tests is limited. However, further investigation on the early change in P-wave duration in patients with interatrial block and the development of new interatrial block during exercise could be helpful in optimizing exercise tolerance tests, particularly when borderline or suboptimal.

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.

Angiographic localization of potential culprit coronary arteries in patients with interatrial block following a positive exercise tolerance test

Interatrial block (IAB), denoted by P waves > or =110 ms, is believed to be associated with underlying ischemia, particularly with that of its principal interatrial conduction pathway, the Bachmann bundle. We investigated if there is an angiographic association of IAB on electrocardiograms at rest in patients who underwent cardiac angiography after a positive exercise tolerance test (ETT) result. Twenty-seven patients with IAB and 42 control patients without IAB on electrocardiograms at rest who had evidence of ischemia on cardiac angiography after ETT were identified. Coronary vessels that were angiographically most significantly stenosed (> or =70% occlusion indicating stenosis) were noted for statistical comparison (a p value <0.05 was considered statistically significant). Among patients with IAB, the right coronary artery was the predominant vessel to be affected, with > or =70% narrowing compared with the left, inclusive of the left main, left circumflex, obtuse marginal, and diagonal coronary arteries (58% vs 23%, p = 0.03). Right coronary artery lesions in patients with IAB were mostly in the proximal and mid portions (54% vs 25% for the entire left coronary artery, p = 0.02). No such difference was noted in control subjects. In conclusion, in patients with IAB at rest who have coronary heart disease, the right coronary artery is predominantly more significantly affected.

Association of Duke prognostic treadmill scores with change in P-wave duration during exercise tolerance tests in patients with interatrial block and coronary heart disease

Interatrial block (IAB), as denoted by P waves > or =110 ms in duration, is believed to be associated with underlying ischemia, particularly with that of its principal interatrial conduction pathway, the Bachmann bundle. In this study, the association between Duke prognostic treadmill (DPT) scores and change in P-wave duration in IAB was investigated in patients who underwent cardiopulmonary exercise tolerance tests (CPETTs). Twenty-seven patients with IAB and 42 control patients without IAB on electrocardiography at rest who had evidence of myocardial ischemia on coronary angiography after CPETTs were identified consecutively. P-wave measurements were obtained independently at the beginning of every CPETT stage and also when P-wave changes occurred. Increments in P-wave durations were measured to the nearest 20 ms. DPT scores were calculated for the 2 groups. There was no significant difference between the groups in mean values for DPT scores and for exercise capacity. However, change in P-wave duration in patients with IAB was significantly associated with mean DPT score. As the change in P-wave duration increased, the DPT score was significantly less (p = 0.003). DPT scores were more significant with P-wave changes of >20 ms compared with P-wave changes of < or =20 ms (p = 0.00001). In conclusion, in patients with coronary heart disease and IAB at rest, increases in P-wave durations during CPETTs are inversely associated with DPT scores.

The Bachmann Bundle and interatrial conduction

The cardiac conduction system (CCS) is responsible for generation and systematic conduction of cardiac impulses. The Bachmann Bundle (BB), considered one of its several accessory impulse-conducting pathways, plays a fundamental role in interatrial conduction. Delay in this pathway leads to prolongation of the P wave on the electrocardiogram (interatrial delay or block), which in turn is a precursor for atrial tachyarrhythmias, mainly atrial fibrillation and significant left atrial electromechanical dysfunction. As such, the magnitude of its sequelae has necessitated a flurry of investigations that have been targeted toward its prevention and management. Although current studies on the use of angiotensin-converting enzyme inhibitors and atrial pacing have indeed shown some promise, it would be shortsighted to overlook and circumvent the actual underlying lesion-BB abnormality. Thus, a thorough understanding of the CCS and interatrial conduction is essential. We review current literature on the BB and discuss potential mechanisms that affect its conduction.

Interatrial block during exercise tolerance tests as an additional parameter for the diagnosis of ischemic heart disease

INTRODUCTION

Interatrial block (IAB; P-wave duration, >or=120 milliseconds) is associated with increases of left atrial pressure. We studied the use of IAB during exercise tolerance test (ETT) in diagnosis of ischemic heart disease.

METHOD

Exercise tolerance tests were performed in 149 patients (mean age, 50 years; male, 60.4%). P-wave duration was measured at rest, at each stage of exercise using the Bruce protocol, and in recovery. As clinically indicated, 71 patients subsequently underwent nuclear stress test and/or catheterization. The evidence of ischemia (EOI) was considered present according to the more definite test, that is, catheterization over nuclear stress test over ETT.

RESULTS

Among patients who did not have IAB at rest (n=115), 63 patients (54.7%) developed IAB during the ETT. The incidence of IAB during the ETT was higher in patients with EOI than patients without EOI (88.9% vs 51.9%, P=.03). When IAB during the ETT and positive ETT were used together to detect EOI, they were more accurate (86.1% vs 81.7%) than the ETT alone. Among patients with IAB at rest (n=34), patients with EOI had a higher incidence of P-wave duration increase of more than 20 milliseconds during the recovery period than patients without EOI (100% vs 21.8%, P=.015). When using P-wave duration increase of more than 20 milliseconds during the recovery period in conjunction with positive ETT, the sensitivity in detecting EOI was higher than using the ETT alone (100% vs 0%), but the specificity was worsened (68.8% vs 84.4%).

CONCLUSION

New IAB and worsening of IAB during ETT appeared in patients with ischemic heart disease and may be used as additional parameters for the ETT interpretation.

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.

Effects of primary percutaneous coronary intervention on P wave dispersion

BACKGROUND

Several studies demonstrated that P wave dispersion (PWD) increased after coronary occlusion. The effect of primary percutaneous coronary intervention (PCI) on PWD needs to be elucidated.

METHODS

The study consisted of 125 patients with acute myocardial infarction (110 men, mean age 59.8+/-7.8 years) undergoing primary PCI. The patients were divided into three groups according to thrombolysis in myocardial infarction myocardial perfusion grade (TMPG) after successful PCI. Groups 1 (n=12), 2 (n=9), and 3 (n=104) included the patients with TMPG 0/1, 2, 3, respectively. Electrocardiograms were obtained before and approximately 66+/-18 minutes after PCI.

RESULTS

PWD and P(maximum) after PCI were significantly lower than the preintervention values (P<0.001 for both). When PWD and Pmaximum values after PCI were compared among groups, PWD and Pmaximum in groups 1 and 2 were found to be higher than those of group 3 (P<0.001 for PWD and Pmaximum). Atrial fibrillation (AF) occurred in 14 patients. Pmaximum and PWD in patients with AF were higher compared to those of the patients without AF (P<0.001 for both P wave parameters). Also more frequent AF attacks were observed in group 1 compared to group 3 (P<0.001).

CONCLUSIONS

PWD and Pmaximum after primary PCI were lower compared to the preintervention values. Prolonged PWD in patients with poor myocardial perfusion can contribute to increased mortality, and also it can can be combined with ST segment resolution to predict clinical reperfusion and might help in predicting AF.

Influence of high-dose leucovorin and 5-fluorouracil chemotherapy regimen on P wave duration and dispersion

BACKGROUND

Although 5-fluorouracil (5-FU)-related cardiotoxicity is well known, atrial arrhythmia, as a potentially serious complication has not been studied in detail. The aim of this study was to determine the P max and Pd in the electrocardiograms (ECG) of patients receiving 5-FU treatment.

METHODS

Twenty-five patients (mean age: 62 years) receiving a 5-FU bolus plus continuous infusion with calcium leucovorin over 48 h and with normal pre-treatment cardiac physical examinations, ECG and echocardiography were enrolled. P maximum (P max), P minimum (P min) and P dispersion (Pd) (maximum minus minimum P wave duration) were measured from the 12-lead ECG at the 0th and 48th hour of the first chemotherapy cycle. Echocardiography was also obtained in all patients at the same times.

RESULTS

Clinical cardiotoxicity was observed in two patients. P max and Pd were both significantly longer after 5-FU treatment at the 48th hour (P < 0.001). P min did not change (P > 0.05).

CONCLUSION

Treatment with 5-FU based regimens may increase Pd and prolong the P max in cancer patients. These alterations may be predictive of patients at risk of atrial arrhythmias during 5-FU treatment.

Predictive value of P-wave signal-averaged electrocardiogram for atrial fibrillation in acute myocardial infarction

BACKGROUND

Atrial fibrillation (AF) is a common complication of acute myocardial infarction (AMI) with a reported incidence of 7-18%. Recently, P-wave signal-averaged electrocardiogram (P-SAECG) has been used to assess the risk of paroxysmal AF attacks in some diseases. The aim of this study was to determine prospectively whether patients with AMI at risk for paroxysmal AF would be identified by P-SAECG and other clinical variables.

METHODS

A total of 100 patients (mean age: 59+/-12, 77 male, 23 female) with ST segment elevation AMI were enrolled in this study. Patients with chronic AF were excluded. At entry, all patients underwent standard 12-lead ECG and in the first 24 hours, P-SAECG was taken, and echocardiography and coronary angiography were performed on the patients. Patients are followed for a month in terms of paroxysmal AF attacks and mortality.

RESULTS

AF was determined in 19 patients (19%). In patients with AF, abnormal P-SAECG more frequently occurred than in patients without AF (37% vs 15%, P<0.05). Patients with AF were older (70+/-14 vs 56+/-10, P<0.001) and had lower left ventricular ejection fraction (42%+/-8 vs 49%+/-11, P<0.05). AF was less common in thrombolysis-treated patients (47% vs 74%, P<0.05). Thirty-day mortality was higher in patients with AF (16% vs 2%, P=0.05).

CONCLUSIONS

An abnormal P-SAECG may be a predictor of paroxysmal AF in patients with AMI. Advanced age and systolic heart failure were detected as two important clinical risk factors for the development of AF.

Effects of P-wave dispersion on atrial fibrillation in patients with acute anterior wall myocardial infarction

BACKGROUND

P-wave dispersion (P dispersion), defined as the difference between the maximum and the minimum P-wave duration (P minimum), and maximum P-wave duration (P maximum) have been used to evaluate the discontinuous propagation of sinus impulse and the prolongation of atrial conduction time respectively. The aim of this study was to investigate whether early assessment of P dispersion predicts paroxysmal atrial fibrillation (AF) in patients with acute anterior wall myocardial infarction (MI).

METHODS

We prospectively evaluated 147 consecutive patients (45 women, 102 men; aged 55 +/- 9 years) with a first acute anterior wall MI. All patients were evaluated by echocardiography to measure the left atrial diameter and left ventricular ejection fraction (LVEF). Electrocardiography was recorded from all patients on admission and every day during hospitalization.

RESULTS

AF occurred in 25 patients. In 122 patients, AF did not occur. P maximum was found to be significantly higher in patients with AF than in patients without AF (115 +/- 17.3 ms vs 101 +/- 14.7 ms, P = 0.001). P dispersion also was significantly higher in patients with AF than in patients without AF (50 +/- 12.5 ms vs 43 +/- 10.1 ms, P = 0.01). There was no significant difference between the two groups in P minimum (64 +/- 12.5 ms vs 59 +/- 11.7 ms, P = 0.057). The echocardiographically left atrial diameters were not significantly higher in the patients with AF than those without (25 +/- 3.38 mm and 23 +/- 3.36 mm, respectively, P = 0.76). LVEF was found to be significantly different in the patients who developed AF and in those who did not (37.96 +/- 6.18% vs 47.70 +/- 6.01%, P = 0.0001).

CONCLUSIONS

Although P maximum and P dispersion are significant predictive factors of AF in patients with acute anterior wall MI in the univariate analysis, on the basis of multivariate analysis, only age and LVEF were independent predictive parameters for AF.

A basic approach to the interpretation of the exercise test

To interpret the exercise test, the following parameters need to be evaluated: the heart rate and blood pressure response, symptoms, dysrhythmias, aerobic capacity, and evidence for myocardial ischemia. When analyzing the ST segment for ischemia, the amount and type of ST depression and the time of onset and resolution are examined. The exercise test results are best used to determine a post-test probability that the patient has significant coronary disease, predict its severity, and provide a prognosis of the patient. The test allows primary care physicians to decide which patients with coronary artery disease can be safely managed medically and which high-risk patients need further evaluation and consideration for revascularization.

Short-, mid-, and long-term reproducibility of the atrial signal-averaged electrocardiogram in healthy subjects: comparison with the conventional ventricular signal-averaged electrocardiogram

Although atrial signal-averaged electrocardiogram (SAECG) has been proposed for noninvasive identification of patients with atrial tachyarrhythmias, the substantial variability of the measurement limits the clinical value. The aim of the study was to assess the short- to long-term reproducibility of atrial SAECG and to compare it to that of the conventional ventricular SAECG in 51 healthy volunteers (30 men; age 32 +/- 8 years). In each subject, SAECG recordings were obtained using MAC-VU electrocardiograph and HiRES and PHiRES software (Marquette Medical Systems) and repeated after 5 minutes, 1 day, 1 week, and 1 month. Automatically detected onset and offset of the filtered QRS complex and P wave were subsequently corrected by two independent observers, and the averaged values were used for the analysis. Conventional ventricular SAECG parameters: filtered QRS duration (QRStot), low amplitude signal duration, and root mean square voltage (RMS) of the terminal 40 ms of QRS, and 5 atrial parameters: filtered P wave duration (Ptot), RMS of the terminal 40, 30, 20 ms, and of the entire P wave were obtained. Relative errors of different pairs of measures were used to assess the intrasubject reproducibility. QRStot and Ptot were the most reproducible parameters. The relative errors after 5 minutes, 1 day, 1 week, and 1 month were 0.8% to 2.4% for QRStot, and 1.3% to 4.2% for Ptot. For RMS voltages, the relative errors exceeded 15% in short-term and 20% in long-term recordings. Although Ptot was statistically less reproducible than QRStot, the reproducibility of the former was good and comparable to that of the QRStot. The reproducibility of the voltage parameters was significantly poorer than that of the duration parameters. The study showed a satisfactory short- and long-term reproducibility of Ptot in the atrial SAECG in healthy subjects. However, low reproducibility of the voltage parameters should be considered in clinical applications.

Effects of ischemia on P wave dispersion and maximum P wave duration during spontaneous anginal episodes

P wave dispersion (P dispersion), defined as the difference between the maximum and the minimum P wave duration, and maximum P wave duration (P maximum) are electrocardiographic (ECG) markers that have been used to evaluate the discontinuous propagation of sinus impulses and the prolongation of atrial conduction time, respectively. To study the effects of myocardial ischemia on P dispersion and P maximum, 95 patients with coronary artery disease (CAD) and typical angina pectoris and 15 controls with angina like symptoms underwent 12-lead surface ECG during and after the relief of pain. During pain and during the asymptomatic period, P maximum and P dispersion were calculated from the averaged complexes of all 12 leads. P dispersion increased significantly during spontaneous angina (45+/-17 ms) compared to the asymptomatic period (40+/-15 ms), P < 0.001 only in the patient group. Both P maximum and P dispersion showed higher values during angina in those patients who developed diffuse ischemia, as estimated with ST segment changes in multiple ECG leads. P dispersion showed higher values during the anginal episode in patients with left ventricular dysfunction, independently of the presence of a previous myocardial infarction. Atrial conduction abnormalities, as estimated with P maximum and particularly P dispersion, are significantly influenced by myocardial ischemia in patients with CAD and spontaneous angina.

Asymptomatic coronary artery disease detection: update 1996. A screening protocol using 16-lead high-resolution ECG, ultrafast CT, exercise testing, and radionuclear imaging

The authors have proposed a new four-step screening algorithm to detect asymptomatic coronary artery disease (CAD) in flight school candidates, cadets, and rated flyers of the Unites States Air Force (USAF). In step 1, the USAF Armstrong Laboratory (USAF/AL) risk profile and improved 16-lead high-resolution electrocardiogram/vectorcardiogram will be recorded at baseline. On routine follow-up evaluations, quantitative serial comparisons will be performed by the method of Kornreich. In step 2, beginning with flight school candidates and cadets, all three groups will be studied by the ultrafast computed tomograph (CT) protocol. Those candidates positive for coronary calcium will be studied by coronary angiography and ventriculography, and their eligibility for continued rated flight status will be determined by present criteria. In step 3, those candidates negative for coronary calcium by ultrafast CT will then be screened by the newly defined and improved high-sensitivity treadmill exercise test criteria. In step 4, candidates with a positive treadmill exercise test result, or who are also found in the upper quintile of the USAF/AL risk profile, wild also have exercise nuclear wall motion studies and perfusion scans. If these are abnormal and suggestive of myocardial ischemia, this subset will also be studied by heart catheterization and coronary angiography, and their eligibility for continued rated flight status will be determined by present criteria. The incidence of coronary calcium/no calcium for each degree of stenosis in the 6,000 flyers in each quintile was used to develop the following projections: (1) that more than 3 of 4 rated flyers with unsuspected CAD, and (2) more than 9 of 10 with severe flow-limiting CAD can be identified by these upgraded screening procedures. Evidence is herein presented that these enhancements will result in a major (5-8-fold) increase in case finding of this disease. Based on the estimate of four lost high-performance aircrafts per year from sudden incapacitation of the pilot due to CAD, when this four-step screen is fully operational, it can be expected to reduce the $80 million annual losses to the United States government from CAD by 85%, a savings of $68 million per year.

Effects of acute volume changes on P wave characteristics: correlation with echocardiographic findings in healthy men

INTRODUCTION

This study was performed to determine the effect on the P wave of different hemodynamic loads to the heart.

METHODS AND RESULTS

Signal-averaged P wave ECG and atrial echocardiographic measurements were obtained from eight healthy male volunteers at rest and after infusion of 1000 mL of plasma expander (Haemaccel) over 15 minutes. These measurements were repeated 24 hours later at rest and after 0.8 mg of nitroglycerin given sublingually. The effect of positional changes was also studied. At rest the amplitude of the P wave and the time of the maximal the P wave amplitude were reproducible. Sitting increased heart rate variability; no significant changes of the P wave were found. Volume overload decreased the heart rate and increased the atrial size on echocardiography with changes in lead V1 (earlier appearance of the first positive deflection). Nitroglycerin administration increased heart rate and decreased the echocardiographic size of the atria, the latter not reaching statistical significance. Administration of nitroglycerin induced P wave amplitude rise in leads I and II. The maximal power in fast Fourier transformation for calculated orthogonal leads X and Y increased as well.

CONCLUSIONS

Amplitude behavior in leads I, II, and V1 appears to correlate with load conditions, particularly with volume redistribution. In healthy men subtle changes in the P wave morphology after volume changes can be detected by the signal-averaged ECG. Application of these findings in patients following acute changes in circulation needs further investigation.

Current usefulness of the signal-averaged electrocardiogram

Signal-averaged electrocardiography is a relatively simple, noninvasive technique by which valuable information can be gained to help in the management of patients with cardiovascular disease. The presence of late potentials on the SAECG is a good marker for the presence of an arrhythmogenic substrate that is believed to be the source of ventricular tachycardia in patients with coronary artery disease. The value of the detection of late potentials has been studied best after myocardial infarction, when the absence of late potentials makes the occurrence of an arrhythmic event very unlikely. The positive predictive value for an arrhythmic event to occur in the presence of late potentials is low, however, comparable to the predictive value of decreased left ventricular function, complex ventricular ectopy, or abnormal autonomic tone. This appears to have its explanation in the complex pathophysiology behind the occurrence of arrhythmic events. Improved accuracy for the SAECG is achieved when the result of the test is interpreted with consideration of the presence or absence of other predictive markers. A thorough understanding of the signal-averaged electrocardiogram makes optimal clinical use of the information gained from this easily acquired test possible.

Analysis of the signal-averaged P-wave duration in patients with percutaneous coronary angioplasty-induced myocardial ischemia

To assess the impact of angioplasty-induced myocardial ischemia on the duration of the surface P wave, patients undergoing elective angioplasty of isolated lesion in the left anterior descending, circumflex or right coronary arteries were monitored with a 3-channel electrocardiographic Holter system. The leads used were modified bipolar chest leads V5, aVF and V2 (CM-V5, CS-aVF and CM-V2). After echocardiographic signal-averaging, the earliest onset and the latest offset of the P wave were identified in all of the above time-aligned signal-averaged leads, and the composite maximal P duration was measured under 10 x magnification. The maximal ST-segment shift during balloon inflation was also measured in all of the above leads at 60 ms after the J point. In the study group comprising 47 patients, the mean signal-averaged P-wave duration was 125.0 +/- 16 ms at baseline versus 130.0 +/- 15 ms during balloon inflation, p less than 0.005. In the left anterior descending coronary artery group (n = 23), the mean signal-averaged P-wave duration was 122.4 +/- 17 ms and 131.3 +/- 16 ms during balloon inflation, p less than 0.005). In the group with a right coronary artery lesion (n = 18), the values were 127.3 +/- 14 ms and 128.4 +/- 13 ms respectively (p = not significant). Significant increases in the P-wave duration were found to occur in groups both with (n = 34) and without (n = 13) ST-segment shift greater than or equal to 1 mm (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)