P-wave Area Research Articles

P-Wave Indices and Risk of Ischemic Stroke: A Systematic Review and Meta-Analysis.

Atrial cardiomyopathy is associated with an increased risk of ischemic stroke. P-wave terminal force in lead V1, P-wave duration, and maximum P-wave area are electrocardiographic parameters that have been used to assess left atrial abnormalities related to developing atrial fibrillation. The aim of this systematic review and meta-analysis was to examine their values for predicting ischemic stroke risk. PubMed and EMBASE databases were searched until December 2016 for studies that evaluated the association between P-wave indices and stroke risk. Both fixed- and random-effects models were used to calculate the overall effect estimates. Ten studies examining P-wave terminal force in lead V1, P-wave duration, and maximum P-wave area were included. P-wave terminal force in lead V1 was found to be an independent predictor of stroke as both a continuous variable (odds ratio [OR] per 1 SD change, 1.18; 95% confidence interval [CI], 1.12-1.25; P<0.0001) and categorical variable (OR, 1.59; 95% CI, 1.10-2.28; P=0.01). P-wave duration was a significant predictor of incident ischemic stroke when analyzed as a categorical variable (OR, 1.86; 95% CI, 1.37-2.52; P<0.0001) but not when analyzed as a continuous variable (OR, 1.05; 95% CI, 0.98-1.13; P=0.15). Maximum P-wave area also predicted the risk of incident ischemic stroke (OR per 1 SD change, 1.10; 95% CI, 1.04-1.17). P-wave terminal force in lead V1, P-wave duration, and maximum P-wave area are useful electrocardiographic markers that can be used to stratify the risk of incident ischemic stroke.

Changes in P-wave morphology after pulmonary vein isolation: insights from computer simulations.

Apparently conflicting clinical measurements of P-wave duration (PWD) pre- vs. post-ablation have been reported. To assist the interpretation of these clinical data, we used a computer model of the atria and torso to simulate P waves before and after pulmonary vein (PV) isolation. Twenty ablation patterns were designed (segmental or ipsilateral ablation; five distances to PV sleeves; addition of a roof line or not). Possible PV reconnections were introduced as gaps in the ablation lines. PWD and area were measured during sinus rhythm in vectorcardiogram (VCG) magnitude signals and on the 16-lead ECG before and after ablation, and after PV reconnection. After PV isolation, biatrial activation time was prolonged by 0-5 ms without and by 48±5 ms with roof line. Yet PWD was shortened in lead V3 and V4 by up to 15 ms. The effect of ablation on P-wave morphology was stronger when larger PV areas were isolated. Segmental and ipsilateral PV isolation led to concordant results. P-wave area increased in V1 and decreased in V6. Changes in PWD and area on the VCG were sensitive to the threshold used for detecting the end of the P wave. The occurrence of PV reconnection was best identified on leads V3, V4, and V9. PV isolation and reconnection induced measurable changes on the 16-lead ECG that might be used to improve patient follow-up after ablation.

Association between left atrial abnormality on ECG and vascular brain injury on MRI in the Cardiovascular Health Study.

Emerging evidence suggests that atrial disease is associated with vascular brain injury in the absence of atrial fibrillation. The Cardiovascular Health Study prospectively enrolled community-dwelling adults aged ≥65 years. Among participants who underwent MRI, we examined associations of ECG left atrial abnormality with brain infarcts and leukoaraiosis. P-wave terminal force in lead V1 was the primary measure of left atrial abnormality; P-wave area and duration were secondary predictors. We excluded participants with atrial fibrillation before or on their index ECG. Primary outcomes were incident infarcts and worsening leukoaraiosis from initial to follow-up scan ≈5 years later. Secondary outcomes were prevalent infarcts and degree of leukoaraiosis on initial MRI. Relative risk (RR) and linear regression models were adjusted for vascular risk factors. Among 3129 participants with ≥1 scan, each SD increase in P-wave terminal force in lead V1 was associated with a 0.05-point (95% confidence interval [CI], 0.0003-0.10) higher baseline white matter grade on a 10-point scale. P-wave terminal force in lead V1 was associated with prevalent infarcts of any type (RR per SD, 1.09; 95% CI, 1.04-1.16) and more so with prevalent nonlacunar infarcts (RR per SD, 1.22; 95% CI, 1.08-1.38). Among 1839 participants with 2 scans, P-wave terminal force in lead V1 was associated with worsening leukoaraiosis (RR per SD, 1.09; 95% CI, 1.01-1.18), but not with incident infarcts (RR per SD, 1.06; 95% CI, 0.93-1.20). Sensitivity analyses adjusting for incident atrial fibrillation found similar results. P-wave area and duration were not associated with outcomes. ECG left atrial abnormality is associated with vascular brain injury in the absence of documented atrial fibrillation.

Abstract T P142: Association between Left Atrial Abnormality on ECG and Vascular Brain Injury on MRI in the Cardiovascular Health Study

Background: Atrial fibrillation (AF) has long been recognized as a risk factor for vascular brain injury. Emerging evidence suggests that atrial disease is associated with vascular brain injury even in the absence of AF. Methods: The Cardiovascular Health Study prospectively enrolled community-dwelling adults ≥65 years of age. Among participants who underwent MRI, we examined associations of left atrial abnormality on a 12-lead electrocardiogram (ECG) with MRI-defined brain infarcts and leukoaraiosis. P-wave terminal force--the product of the duration and depth of the terminal component of the P-wave--in lead V1 (PTFV1) is the most consistently used ECG measure of left atrial abnormality and was our primary predictor; P-wave area and duration were secondary predictors. We excluded participants with AF on their index ECG or a diagnosis of AF prior to the index ECG. Primary outcomes were incident infarcts and worsening leukoaraiosis from initial to follow-up scan approximately 5 years later. Secondary outcomes were prevalent infarcts and degree of leukoaraiosis on initial MRI. Non-lacunar infarcts were separately examined in a secondary analysis. We performed relative risk and linear regression analyses adjusting for vascular risk factors. Results: Among 3,129 participants with at least one scan, each 1-SD increase in PTFV1 (2160 μV*ms) was associated with a 0.05-point (95% CI, 0.0003-0.10) higher baseline white matter grade on a 10-point scale. PTFV1 was also associated with prevalent infarcts of any type (RR per SD, 1.09; 95% CI, 1.04-1.16), and in particular with prevalent non-lacunar infarcts (RR per SD, 1.22; 95% CI, 1.08-1.38). Among 1,839 participants with two scans, PTFV1 was associated with worsening leukoaraiosis (RR per SD, 1.09; 95% CI, 1.01-1.18), but not incident infarcts (RR per SD, 1.06; 95% CI, 0.93-1.20). Similar results were seen in sensitivity analyses accounting for incident AF diagnosed after the ECG and before the MRI under analysis. P-wave area and duration were not associated with our outcomes. Conclusions: ECG left atrial abnormality is associated with vascular brain injury even in the absence of AF.

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

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. 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. 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. 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 and the risk of incident ischemic stroke in the Multi-Ethnic Study of Atherosclerosis.

Emerging data suggest that left atrial disease may cause ischemic stroke in the absence of atrial fibrillation or flutter (AF). If true, this condition may provide a cause for many strokes currently classified as cryptogenic. Among 6741 participants in the Multi-Ethnic Study of Atherosclerosis who were free of clinically apparent cerebrovascular or cardiovascular disease (including AF) at baseline, we examined the association between markers of left atrial abnormality on a standard 12-lead ECG-specifically P-wave area, duration, and terminal force in lead V1-and the subsequent risk of ischemic stroke while accounting for incident AF. During a median follow-up of 8.5 years, 121 participants (1.8%) had a stroke and 541 participants (8.0%) were diagnosed with AF. In Cox proportional hazards models adjusting for potential baseline confounders, P-wave terminal force in lead V1 was more strongly associated with incident stroke (hazard ratio per 1 SD increase, 1.21; 95% confidence interval, 1.02-1.44) than with incident AF (hazard ratio per 1 SD, 1.11; 95% confidence interval, 1.03-1.21). The association between P-wave terminal force in lead V1 and stroke was robust in numerous sensitivity analyses accounting for AF, including analyses that excluded those with any incident AF or modeled any incident AF as having been present from baseline. We found an association between baseline P-wave morphology and incident stroke even after accounting for AF. This association may reflect an atrial cardiopathy that leads to stroke in the absence of AF.

Significant Correlation of P-Wave Parameters With Left Atrial Volume Index and Left Ventricular Diastolic Function

BackgroundThe 12-lead electrocardiogram (ECG) is a commonly used tool to access left atrial enlargement, which is a marker of left ventricular diastolic dysfunction (LVDD). The aim of this study was to evaluate any association of the P-wave measurements in ECG with left atrial volume (LAV) index and LVDD. MethodsThis study enrolled 270 patients. In this study, 4 ECG P-wave parameters corrected by heart rate, that is, corrected P-wave maximum duration (PWdur-MaxC), corrected P-wave dispersion (PWdisperC), corrected P-wave area (PWareaC) and corrected mean P-wave duration (meanPWdurC), were measured. LAV and left ventricular diastolic parameters were measured from echocardiography. LVDD was defined as a pseudonormal or restrictive mitral inflow pattern. ResultsThe 4 P-wave parameters were significantly correlated with the LAV index after adjusting for age, sex, diabetes, hypertension, coronary artery disease, body mass index and diastolic blood pressure in multivariate analysis. The standardized β coefficients of PWdurMaxC, PWdisperC, meanPWdurC and PWareaC were 0.338, 0.298, 0.215 and 0.296, respectively. The 4 P-wave parameters were also significantly correlated with LVDD after multivariate logistic regression analysis. The odds ratios (95% confidence intervals) of PWdurMaxC, PWdisperC, meanPWdurC and PWareaC were 1.03 (1.01–1.04), 1.02 (1.04–1.04), 1.04 (1.02–1.07) and 1.01 (1.00–1.02), respectively. ConclusionsThis study demonstrated that PWdurMaxC, PWdisperC, meanPWdurC and PWareaC were important determinants of the LAV index and LVDD. Therefore, screening patients by means of the 12-lead ECG may be helpful in identifying a high-risk group of increased LAV index and LVDD.

Electrocardiographic P wave changes after thoracoscopic pulmonary vein isolation for atrial fibrillation

Changes in P wave duration (PWD) and P wave area (PWA) have been described following catheter ablation for atrial fibrillation (AF). We hypothesize that video-assisted thoracoscopic pulmonary vein isolation (VATS-PVI) for AF results in decrease of PWD, PWA and P wave dispersion, which may resemble reverse electrical remodeling of the atrium after restoration of sinus rhythm. VATS-PVI consisted of PVI and ganglionic plexus ablation in 29 patients (mean age, 59 ± 7years; 23 males; 17 paroxysmal AF) and additional left atrial lesions in patients with persistent AF. PWD and PWA were measured in ECG lead II, aVF and V2 of ECGs during sinus rhythm before, directly after, and 6months postprocedure. P wave dispersion was derived from the 12 lead ECG. Prior to VATS-PVI, PWD did not correlate with left atrial size and no difference in left atrial size was found between patients with paroxysmal or persistent AF (p = 0.27). Following VATS-PVI, PWD initially prolonged in all patients from 115 ± 4.6ms to 131 ± 3.6ms (p < 0.01) but shortened to 99 ± 3.2ms after 6months (p < 0.01). PWA was 5.60 ± 0.32mV*ms at baseline, 6.44 ± 0.32mV*ms post-VATS-PVI (P = NS), and 5.40 ± 0.28mV*ms after 6months (p = NS vs. baseline, p < 0.05 vs. post-VATS-PVI). P wave dispersion decreased in the persistent AF group from baseline 67 ± 3.3 to 64 ± 2.5ms post-VATS-PVI (p = 0.30) and to 61 ± 3.4ms after 6months (p < 0.05). PWD increases significantly directly after successful VATS-PVI in both groups. There was significant decrease in PWD after 6months. Similarly, P wave dispersion decreased in the persistent group. These changes suggest an immediate procedure related effect, but the later changes may represent reverse electrical atrial remodeling following cessation of AF.

Non-Invasive Characterization of Electrical Remodeling in a Risk Factor Modification Program

Introduction: Weight management in obese subjects is suggested to improve cardiac remodelling. Little is known about the atrial electrical changes that accompany weight reduction.Methods: In a randomized-controlled trial (ANZCTR: 12610000497000), 46 subjects with BMI >27 in sinus rhythm were randomized to a comprehensive risk factor management program or general lifestyle advice, and followed-up for 12-months. Metabolic profiles, pharmacotherapy, BMI, waist circumference (WC) and body surface area (BSA) were recorded. Digital analysis of 12-lead ECGs was used to assess P-wave duration (PWD) and area (PWA) and indexed to BSA (PWD-I and PWA-I), at baseline and at completion of the study.Results: Subjects were well matched for all baseline characteristics (25 active, 21 controls). Mean follow-up was 11.6±1.6 months. Using the paired-sample t-test, significant reduction was seen in all indices at 12-months (PWD; P<0.001, PWA; P=0.001, PWD-I; P=0.014, PWA-I; P=0.016) in the active group. No significant difference was seen in the control group. Using regression analysis with intention-to-treat, active group allocation was predictive of abbreviated P-wave indices (P=0.019). Controlling for age, gender, baseline respiratory disturbance index (RDI), ΔBMI, ΔWC and ΔBSA, significant correlation remained between shortening of PWD-I and number of anti-hypertensive medication used (P=0.026). Conclusion: A structured comprehensive risk factor management program, with aggressive hypertension management and weight reduction, is associated with a favourable improvement in ECG-derived indices of atrial electrical remodelling.

P-wave Measurements and Electrical Reconnection of the Posterior Left Atrium after Catheter Ablation for Atrial Fibrillation

Recurrent atrial arrhythmias (RAAs) following posterior left atrial isolation (PLAI) for atrial fibrillation are common and are associated with reconnection of the PLA and pulmonary veins. We aimed to show that P-wave duration (PWD) and P-wave area under the curve (PWAUC) changes in patients undergoing PLAI can be measured using signal-averaged electrocardiogram (SAECG), and that reversal of these changes in patients with RAAs can be used to noninvasively detect reconnection. SAECG recordings before and after PLAI in 52 patients were analyzed for changes in PWD and PWAUC and also in 26 of these patients who had a repeat procedure for RAA. PWD and PWAUC reduced significantly in most leads following PLAI (mean 104 ± 11 ms to 93 ± 15 ms [P < 0.001] and 3.53 ± 1.23 microvolt seconds (μVs) to 2.87 ± 1.23 μVs [P = 0.001], respectively). Reconnection was observed in 20 of 26 patients at the repeat procedure. Compared to after the first procedure, reconnected patients had increased PWD and PWAUC (e.g., the increase in V4 was 14.1 ± 20.9 ms [P = 0.01] and 0.98 ± 1.17 μVs [P = 003], respectively) at the repeat procedure, while nonreconnected patients had decreased PWD and PWAUC (in V4, it was decreased by 11.5 ± 7.0 ms [P = 0.05] and 0.97 ± 0.33 μVs [P = 0.001]). A change in lead V4 PWAUC > -0.29 μVs for detecting reconnection had a sensitivity of 94% and specificity of 100% (receiver operator characteristic area under the curve 0.97, P = 0.005). PLAI reduces PWD and PWAUC while reconnection increases them both. SAECG may be able to detect reconnection of the PLA noninvasively.

A new use for an old technique?

This editorial refers to ‘Changes in P-wave area and P-wave duration after circumferential pulmonary vein isolation’ by K. Van Beeumen et al ., on page 798. Since Brodie first performed high-resolution recordings of the surface P-wave, using signal averaging, more than 40 years ago numerous publications have attempted to establish a clinical use for this technique. Initial case–control studies established that individuals known to have paroxysmal atrial fibrillation (PAF) have a longer P-wave duration and a higher P-wave energy than controls.1 This has lead to exploration of this technique as a predictor of atrial fibrillation (AF) occurrence in populations judged to be at risk or in individuals following intervention for episodes of arrhythmia. Hence, the utility of the signal averaged P-wave as a predictor of AF in a variety of clinical settings has been investigated.2 In general, these and other studies have identified that, in whatever scenario, patients that are likely to develop AF have longer P-waves, increased P-wave energy (or amplitude) and increased P-wave dispersion. Similar findings are apparent when the risk of recurrent AF after cardioversion or after cardioversion from short- or long-term AF are studied.3,4 Despite the above investigations, the signal averaged P-wave remains largely a research tool with limited clinical use. This is likely to relate to the nature of AF itself and of the therapies available for its treatment. …

Changes in P-wave area and P-wave duration after circumferential pulmonary vein isolation

The effect of circumferential pulmonary vein isolation (CPVI) on P-wave characteristics is not clear. We used the signal-averaged (SA) electrocardiogram (ECG) and the ECG derived vector cardiogram (dVCG) to study the influence of CPVI on P-wave duration (PWD) and P-wave area (PWA) and studied whether changes were associated with successful outcome after initial CPVI. Thirty-nine patients (56 +/- 10 years, 72% males) underwent CPVI for paroxysmal or persistent atrial fibrillation (AF). For each patient, an ECG recording was taken at the start and end of the ablation procedure. dVCG was derived using the inverse Dower transform. PWD was defined by manual annotation of earliest onset and latest offset of the SA-P-wave. PWA was calculated as the area under the SA-ECG curve averaged for the 12 ECG leads (PWA-ECG) and SA-dVCG curve (PWA-dVCG). Successful outcome after CPVI was defined as freedom from symptomatic and asymptomatic AF at the end of follow-up (11 +/- 5 months). Average PWD decreased from 132 +/- 14 to 126 +/- 16 ms (P < 0.01). PWA-ECG and PWA-dVCG decreased markedly from 4.64 +/- 1.40 to 3.65 +/- 1.61 mVms (P < 0.001) and from 4.27 +/- 1.66 to 2.48 +/- 1.59 mVms (P < 0.001). Parameters of PWA were not different between successes (n = 31) and failures (n = 8). In contrast, PWD after ablation was significantly shorter in patients with successful outcome (123 +/- 16 vs. 135 +/- 11 ms, P < 0.05). (i) CPVI results in a modest but significant shortening in PWD and a marked decrease in PWA. (ii) PWD was significantly shorter in cases of successful outcome after CPVI.

Ethnic distribution of ECG predictors of atrial fibrillation and its impact on understanding the ethnic distribution of ischemic stroke in the Atherosclerosis Risk in Communities (ARIC) study.

The paradox of the reported low prevalence of atrial fibrillation (AF) in blacks compared with whites despite higher stroke rates in the former could be related to limitations in the current methods used to diagnose AF in population-based studies. Hence, this study aimed to use the ethnic distribution of ECG predictors of AF as measures of AF propensity in different ethnic groups. The distribution of baseline measures of P-wave terminal force, P-wave duration, P-wave area, and PR duration (referred to as AF predictors) were compared by ethnicity in 15 429 participants (27% black) from the Atherosclerosis Risk in Communities (ARIC) study by unpaired t test, chi(2), and logistic-regression analysis, as appropriate. Cox proportional-hazards analysis was used to separately examine the association of AF predictors with incident AF and ischemic stroke. Whereas AF was significantly less common in blacks compared with whites (0.24% vs 0.95%, P<0.0001), similar to what has been reported in previous studies, blacks had significantly higher and more abnormal values of AF predictors (P<0.0001 for all comparisons). Black ethnicity was significantly associated with abnormal AF predictors compared with whites; odds ratios for different AF predictors ranged from 2.1 to 3.1. AF predictors were significantly and independently associated with AF and ischemic stroke with no significant interaction between ethnicity and AF predictors, findings that further justify using AF predictors as an earlier indicator of future risk of AF and stroke. There is a disconnect between the ethnic distribution of AF predictors and the ethnic distribution of AF, probably because the former, unlike the latter, do not suffer from low sensitivity. These results raise the possibility that blacks might actually have a higher prevalence of AF that might have been missed by previous studies owing to limited methodology, a difference that could partially explain the greater stroke risk in blacks.

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 V 1 (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.

Electrocardiographic diagnosis of left atrial enlargement in patients with mitral stenosis: the value of the P-wave area

Objective — To investigate the value of the P-wave area in diagnosing left atrial enlargement in patients with mitral stenosis.Methods — We measured the P-wave area from lead II of a standard 12-lead ECG in 136 consecutive patients with mitral stenosis.We also measured the left atrial diameter with two-dimensional echocardiography.Results — Left atrial enlargement was identified in 120 (88.2%) patients. There was an excellent correlation between P-wave area and left atrial diameter in these patients (r = 0.739, p = 0.001). A P-wave area of ≥4 ms•mv had an 85.8% sensitivity and 93.7% specificity for left atrial enlargement. There was also a smaller but significant correlation between left atrial diameter and the total P-wave duration (r = 0.635, p < 0.01) or P-wave amplitude (r = 0.683, p<0.01) in these patients. However, the P-wave area had a better overall sensitivity than the P-wave duration (43.3%) or amplitude (10.8%) in diagnosing left atrial enlargement.Conclusions — Left atrium enlargement can be estimated by P-wave area measured from ECG lead II in patients with mitral stenosis. A P-wave area ≥4 ms•mv serves as a new criterion of left atrial enlargement.

Circadian behavior of P-wave duration, P-wave area, and PR interval in healthy subjects.

The prolongation of P-wave duration has long been shown to indicate the presence of high risk for atrial fibrillation. The circadian variation of P-wave characteristics and their dynamic adaptation to heart rate changes was not tested before. To evaluate the diurnal pattern of P-wave duration, P area, and PR interval and of their linearly fitted relation with RR interval, 50 healthy volunteers (25 men, mean age 34 +/- 10 years) underwent 24-hour ambulatory electrocardiographic (ECG) recording with digital 12-lead Holter recorders. The median P-wave duration, P area, and PR interval were calculated from the average 12-lead ECG constructed from each 10-second ECG recording. Single harmonic regression analysis was performed to reveal the presence of circadian variation in the aforementioned ECG parameters. The P area (P < 0.0001, R(2) = 0.78), the PR interval (P < 0.0001, R(2) = 0.92), the P area / RR slope (P < 0.0001, R(2) = 0.55), and the PR/RR slope (P < 0.0001, R(2) = 0.42) showed a highly significant circadian variation while the periodic nature of P-wave duration (P = 0.016, R(2) = 0.32) and of the P duration / RR slope (P = 0.011, R(2) = 0.18) was only indicated by harmonic regression analysis. P-wave duration, P area, and PR interval show a significant circadian variation in healthy subjects. The relations between P area/RR,PR/ RR, and P duration/RR also demonstrate a significant diurnal pattern.

Superiority of a vertical sternal lead for detection of arrhythmias during ambulatory electrocardiographic monitoring

In a preliminary study comparing 7 sets of bipolar leads with standard modified V 1 and V 5 leads, a vertical sternal lead system with the negative lead just below the suprasternal notch, and the positive lead over the xiphoid had the greatest P-wave area. In the current study, the vertical sternal and modified V 1 leads were obtained simultaneously using 2-channel ambulatory electrocardiographic recorders in 50 consecutive patients undergoing diagnostic ambulatory electrocardiography for suspected arrhythmias. The vertical sternal lead provided tracings with a larger P-Wave area compared with that of the modified V 1 (0.58 ± 0.44 vs 1.23 ± 0.69 mm 2; p < 0.0001), and a greater QRS complex (9.23 ±4.16 vs 11.78 ± 4.90 mm; p = 0.006). During premature atrial contractions and supraventricular tachycardia, P-wave visibility was significantly better in the sternal lead than in V 1 (p < 0.001). Furthermore, sternal lead tracings were superior with regard to overall quality and noise level. It is suggested that the vertical sternal lead replace the currently used modified V 1 during ambulatory electrocardiographic monitoring. This lead system in conjunction with the standard modified V 5 lead should be useful in the differential diagnosis of atrial arrhythmias.

Effect of caval occlusion on the magnitude of unipolar atrial electrograms in dogs.

Studies were done on eight mongrel dogs anesthetized with pentobarbital sodium to assess the effects of acute changes in heart volume on the magnitude of electrocardiographic potentials recorded from the right atrium. Following midsternotomy, acute changes in heart volume were produced by occlusion of the superior vena cava (SVC), inferior vena cava (IVC), or both vena cavae while heart rate was controlled by pacing the right atrium. P-wave area, defined by integrating absolute value of the P wave over time, increased by 8.2 +/- 7.4% during SVC occlusion, 13.3 +/- 8.5% during IVC occlusion, and 23.6 +/- 16.2% during occlusion of both vena cavae. Areas of ventricular complexes appearing in atrial electrograms decreased by 6.6 +/- 6.2% during SVC occlusion, 11.1 +/- 6.7% during IVC occlusion, and 15.2 +/- 9.2% during occlusion of both vena cavae. These results are compatible with predominately tangential activation of the atrium and radial excitation of the ventricle and provide experimental confirmation of the "Brody effect."