Ta Wave Research Articles

INSIGHTS ON ATRIAL ELECTROCARDIOGRAM IN SINUS RHYTHM AND ATRIOVENTRICULAR BLOCK FOR IMPROVED CLINICAL DIAGNOSIS

Objective: This study aims to characterize P and Ta wave of Modified Limb Lead (MLL) Electrocardiogram (ECG) in Normal Sinus Rhythm (NSR) and Atrioventricular Block (AVB). Methods: ECGs were recorded using MLL configuration from 100 NSR volunteers (mean age 31 years, 35 women) and 20 male AVB patients (mean age 72 years). Amplitudes and durations of P, Ta wave, and PTa Interval (PTaI) were measured, plotted, and analyzed for both the groups. Results: P-wave amplitudes were larger in AVB, and also P, Ta waves correlated significantly in both groups with higher correlation in AVB (NSR: [Formula: see text]; AVB: [Formula: see text]). Ta-wave duration ([Formula: see text][Formula: see text]ms) was longer than P-wave duration ([Formula: see text][Formula: see text]ms) in AVB patients and was opposite to P-wave polarity in all the leads. PP Interval (PPI) correlated significantly with P wave (NSR: [Formula: see text]; AVB: [Formula: see text]), Ta wave ([Formula: see text]; [Formula: see text]), PTaI ([Formula: see text]; [Formula: see text]), and corrected PTaI ([Formula: see text]; [Formula: see text]). Conclusion: P-wave right axis shift leads to the higher P-wave amplitude in AVB which may be due to the advancing age and atrial chamber enlargement. In NSR, the duration of observable Ta wave was longer than P wave, whereas in AVB, the Ta wave duration was 3–3.5 times longer than P wave.

Analysis of normal electrocardiographic patterns in mandarin ducks (Aix galericulata).

Background:Electrocardiographic (ECG) examination in birds is considered an inexpensive and noninvasive diagnostic aid for the recognition of infectious and metabolic diseases. Contrary to other bird species, studies describing normal ECG patterns for mandarin ducks (Aix galericulata) are lacking.Aim:The aim of this study was to describe and evaluate normal ECG patterns in A. galericulata.Methods:Ten clinically healthy mandarin ducks of both sexes, aged between 1 and 2 years and with body weight between 0.8 and 1.2 kg were included. Electrocardiograms were performed in a quiet room with animals conscious and manually restrained. All electrocardiographic parameters were recorded using standard (I, II, and III) and augmented (aVR, aVL, and aVF) limb leads. The paper speed was set at 50 mm/second. The amplitude was 1 mV = 20 mm. Morphological patterns of P, QRS, and T deflections were evaluated in all limb leads. The amplitude and the duration of waves and, their intervals were determined in lead II. The mean electrical axis (MEA) in the frontal plane was calculated using the Bailey hexaxial system.Results:In all birds examined, a regular sinus rhythm was observed. P waves were mainly positive in I, II, III, and aVF. A negative P wave was identified in aVR, while in aVL a great variability was present. The QRS complex was mainly isoelectric in lead I, while it was negative with rS or QS morphology in leads II, III, and aVF. A positive polarity of QRS was detected in aVL with R pattern, while it was negative or positive with QS or R morphology, respectively, in aVF. T waves were mostly positive in leads II, III, and aVF and, isoelectric in lead I. ST slurring and Ta wave were observed in 2/10 and 8/10, respectively. The mean heart rate was 246 ± 90 beats per minute and the MEA was −88.8° ± 9.57°.Conclusion:The ECG tracings of mandarin ducks show similarities and some differences with other avian species. The electrocardiographic values provided here can be used to assist in the interpretation of ECG in A. galericulata.

Retrieving hidden atrial repolarization waves from standard surface ECGs

BackgroundThis study estimates atrial repolarization activities (Ta waves), which are typically hidden most of the time from body surface electrocardiography when diagnosing cardiovascular diseases. The morphology of Ta waves has been proven to be an important marker for the early sign of inferior injury, such as acute atrial infarction, or arrhythmia, such as atrial fibrillation. However, Ta waves are usually unseen except during conduction system malfunction, such as long QT interval or atrioventricular block. Therefore, justifying heart diseases based on atrial repolarization becomes impossible in sinus rhythm.MethodsWe obtain TMPs in the atrial part of the myocardium which reflects the correct excitation sequence starting from the atrium to the end of the apex.ResultsThe resulting TMP shows the hidden atrial part of ECG waves.ConclusionsThis extraction makes many diseases, such as acute atrial infarction or arrhythmia, become easily diagnosed.

ECG Measurements to Emphasize Atrial Potentials Using Modified Limb Lead System

With the advancement in the field of Electrocardiology (ECG), the acquisition of electrical activity of the heart plays an important role in the diagnosis of various cardiovascular diseases. In general, this activity of conduction is acquired using Standard 12 Lead ECG system. Recently, a Modified Limb Lead system has been developed to study the atrial electrical activity for the diagnosis of atrial arrhythmias. The present study is to derive the normal limits of female subjects using Modified Limb Lead (MLL) system. This study was evaluated in 59 female subjects 19.52 ± 1 (Mean ± S.D) and is primarily involved to study atrial potentials with the use of precordial and modified limb lead position. In sinus rhythm female subjects, the P wave amplitude was 33.06 ± 21.18 µV and the Ta wave amplitude was 20.72 ± 18.16 µV. The P wave duration was 94.22 ± 10.64 ms, the Ta wave duration was 85.51 ± 17.49 ms. The results show that modifications in the limb electrode placement have significant effect on amplitudes and PR segment which may be of great importance for the assessment of atrial potentials.

Electrocardiographic findings in 130 hospitalized neonatal calves with diarrhea and associated potassium balance disorders.

BackgroundHyperkalemia in neonatal diarrheic calves can potentially result in serious cardiac conduction abnormalities and arrhythmias.ObjectivesTo document electrocardiographic (ECG) findings and the sequence of ECG changes that are associated with increasing plasma potassium concentrations (cK+) in a large population of neonatal diarrheic calves.AnimalsOne hundred and thirty neonatal diarrheic calves (age ≤21 days).MethodsProspective observational study involving calves admitted to a veterinary teaching hospital.ResultsHyperkalemic calves (cK+: 5.8‐10.2, blood pH: 6.55‐7.47) had significantly (P < .05) longer QRS durations as well as deeper S wave, higher T wave, and higher ST segment amplitudes in lead II than calves, which had both venous blood pH and cK+ within the reference range. The first ECG changes in response to an increase in cK+ were an increase in voltages of P, Ta, S, and T wave amplitudes. Segmented linear regression indicated that P wave amplitude decreased when cK+ >6.5 mmol/L, S wave amplitude voltage decreased when cK+ >7.4 mmol/L, QRS duration increased when cK+ >7.8 mmol/L, J point amplitude increased when cK+ >7.9 mmol/L, and ST segment angle increased when cK+ >9.1 mmol/L. P wave amplitude was characterized by a second common break point at cK+ = 8.2 mmol/L, above which value the amplitude was 0.Conclusions and Clinical ImportanceHyperkalemia in neonatal diarrheic calves is associated with serious cardiac conduction abnormalities. In addition to increased S and T wave amplitude voltages, alterations of P and Ta wave amplitudes are early signs of hyperkalemia, which is consistent with the known sensitivity of atrial myocytes to increased cK+.

PP-468 - Exercise-Induced Atrial Repolarization Ta Wave

PP-468 - Exercise-Induced Atrial Repolarization Ta Wave

Characteristics of the atrial repolarization phase of the ECG in paroxysmal atrial fibrillation patients and controls.

The aim of this study is to characterize the observable segment of the atrial repolarization (Ta wave) of the standard ECG during sinus rhythm in paroxysmal atrial fibrillation (PAF) patients and controls. Ta and P waves were measured from signal-averaged recordings of a standard 12-lead ECG in 40 patients, 20 with PAF, but in SR at the time of recording, and 20 healthy controls. Wave amplitudes and morphologies were measured. There were no significant differences in Ta amplitude between the PAF patients and controls. A subgroup analysis of patients on and off anti-arrhythmic drugs also showed no significant differences in Ta amplitudes. For both groups Ta wave had opposite polarity to the monophasic P wave. Biphasic P waves had Ta polarity opposite to the initial phase of the P wave. Ta wave amplitudes were largest in leads II (mean ± SD, –25 ± 16 μV), V2 (–22 ± 10 μV), V3 (–21 ± 10 μV) and V4 (–20 ± 8 μV). A significant correlation was found between Ta and P wave amplitudes, leads recording larger P waves also had larger Ta waves (PAF group: r = 0.15 (P = 0.02) PAF vs r = 0.33 (P = 0.002) HC). No differences in the amplitude of the observable section of the atrial repolarization phase of the ECG could be observed between patients with PAF and controls. Ta wave correlates with the corresponding P wave in both amplitude and polarity.

The atrial T wave: The elusive electrocardiographic wave exposed by a case of shifting atrial pacemaker

The atrial T wave (Ta wave) is the body surface manifestation of atrial repolarisation and, unlike the P wave (atrial depolarisation), is little recognised. We report the case of a patient with shifting pacemaker which clearly demonstrates the effect of the Ta wave on ST segment and T wave. A simple conceptual model is used to explain the observed phenomenon. The case serves as a reminder of this often forgotten ECG wave and its potential effects on other ECG features.

PROPOSED SIMPLE METHOD FOR ELECTROCARDIOGRAM RECORDING IN FREE-RANGING ASIAN ELEPHANTS (ELEPHAS MAXIMUS).

Electrocardiography represents a relevant diagnostic tool for detecting cardiac disease in animals. Elephants can present various congenital and acquired cardiovascular diseases. However, few electrophysiologic studies have been reported in captive elephants, mainly due to challenging technical difficulties in obtaining good-quality electrocardiogram (ECG) tracings, and no data are currently available for free-ranging Asian elephants (Elephas maximus). The purpose of this pilot prospective study was to evaluate the feasibility of using a simple method for recording ECG tracings in wild, apparently healthy, unsedated Asian elephants (n = 7) in the standing position. Successful six-lead recordings (I, II, III, aVR, aVL, and aVF) were obtained, with the aVL lead providing the best-quality tracings in most animals. Variables measured in the aVL lead included heart rate, amplitudes and duration of the P waves, QRS complexes, T and U waves, and duration of the PR, QT, and QU intervals. A negative deflection following positive P waves, representative of an atrial repolarization wave (Ta wave), was observed for five out of the seven elephants.

Characteristics of the atrial repolarization phase of the ECG in paroxysmal atrial fibrillation patients and controls

Objective The aim of this study is to characterize the observable segment of the atrial repolarization (Ta wave) of the standard ECG during sinus rhythm in paroxysmal atrial fibrillation (PAF) patients and controls.Methods Ta and P waves were measured from signal-averaged recordings of a standard 12-lead ECG in 40 patients, 20 with PAF, but in SR at the time of recording, and 20 healthy controls. Wave amplitudes and morphologies were measured.Results There were no significant differences in Ta amplitude between the PAF patients and controls. A subgroup analysis of patients on and off anti-arrhythmic drugs also showed no significant differences in Ta amplitudes. For both groups Ta wave had opposite polarity to the monophasic P wave. Biphasic P waves had Ta polarity opposite to the initial phase of the P wave. Ta wave amplitudes were largest in leads II (mean ± SD, –25 ± 16 μV), V2 (–22 ± 10 μV), V3 (–21 ± 10 μV) and V4 (–20 ± 8 μV). A significant correlation was found between Ta and P wave amplitudes, leads recording larger P waves also had larger Ta waves (PAF group: r = 0.15 (P = 0.02) PAF vs r = 0.33 (P = 0.002) HC).Conclusion No differences in the amplitude of the observable section of the atrial repolarization phase of the ECG could be observed between patients with PAF and controls. Ta wave correlates with the corresponding P wave in both amplitude and polarity.

Unmasking atrial repolarization to assess alternans, spatiotemporal heterogeneity, and susceptibility to atrial fibrillation

Detection of atrial repolarization waves free of far-field signal contamination by ventricular activation would allow investigation of atrial electrophysiology and factors that influence susceptibility to atrial tachycardia and atrial fibrillation (AF). The purpose of this study was to identify means for high-resolution intracardiac recording of atrial repolarization (Ta) waves using standard clinical electrocatheters and to assess fundamental electrophysiologic properties relevant to AF risk. In alpha-chloralose anesthetized Yorkshire pigs, we studied effects of vagus nerve stimulation (VNS) on PTa and QT intervals and effects of acute atrial ischemia or administration of intrapericardial acetylcholine followed by intravenous epinephrine on susceptibility to AF. Electrocatheters with closely spaced (1-mm) electrode pairs yielded high-resolution tracings of atrial repolarization waves. These recordings permitted detection of differential effects of right or left VNS, which shortened atrial PTa interval by 30% vs. 21% (P <.01) and lengthened QT interval by 1.5% vs. 9%, respectively (P < .05). During atrial ischemia, STa segments were elevated 3.4-fold (P < .01), and the threshold for inducing AF was reduced 3.1-fold (P = .004). Ischemia amplified atrial T-wave alternans (TWAa) and spatiotemporal heterogeneity (TWHa) by 23- and 13-fold, respectively, in inverse correlation to AF threshold (r = 0.74, P <.01; r = 0.61, P = .03). TWAa and TWHa increased by 4.5- and 2-fold shortly before autonomically triggered atrial premature beats and AF. This study used standard electrocatheters to demonstrate that TWAa and TWHa analysis provides means to assess vulnerability to AF without provocative electrical stimuli. These parameters could be evaluated in the clinical electrophysiology laboratory to determine risk for this prevalent arrhythmia and efficacy of contemporary and new agents.

A Study on Atrial Ta Wave Morphology in Healthy Subjects: An Approach Using P Wave Signal-Averaging Method

A Study on Atrial Ta Wave Morphology in Healthy Subjects: An Approach Using P Wave Signal-Averaging Method

Catch the Ta Wave: A Source of ST-Segment Elevation

Catch the Ta Wave: A Source of ST-Segment Elevation

Analysis of the atrial repolarization wave in dogs with third-degree atrioventricular block

To characterize the electrocardiographic features of the atrial repolarization (Ta) wave in dogs with third-degree atrioventricular (AV) block. ECGs of 36 dogs with third-degree AV block and no identifiable structural heart diseases. Standard 12-lead ECGs were acquired with a digital system, and measurements were manually edited. A Ta wave was detectable in all dogs for at least 1 ECG lead. The Ta wave had negative polarity in leads I, II, III, and aVF and positive polarity in leads aVL and aVR, with a mean electrical axis of -114.26°. Mean duration and mean amplitude of the Ta wave in lead II were 140.2 milliseconds and -0.09 mV, respectively, with the ratio for the Ta-to-P wave duration of 2.3 and the ratio of Ta-to-P wave amplitude of -0.35. Significant correlations were found between the Ta wave duration and duration of the P-Ta interval, Ta wave amplitude and the ECG lead, Ta wave duration and body weight, and duration of the P-Ta interval and atrial rate. Measurements of the Ta wave were repeatable. Measurements of the Ta wave in dogs with third-degree AV block were repeatable. The values for the Ta wave reported here can be used as reference values for dogs with AV conduction disturbances and an echocardiographically normal atrial size. Further studies are needed to validate these results in dogs with structural heart diseases.

Atrial repolarization: its impact on electrocardiography

The repolarizing Ta wave of normal sinus rhythm is not fully visible unless there is a long P-R interval or complete atrioventicular block. Even with the latter, it is often of unseeably low voltage. It can powerfully influence inferior lead ST deviation in the stress test. The Ta of inverted or retrograde P waves is of higher voltage than that of sinus rhythm and can simulate inferior injury. Evidence of specialized internodal tracts resides in 2 specific atrial action potential properties: resistance to gross hyperkalemia and supernormality. The Ta wave figures essentially in the diagnosis of acute atrial infarction.

Reduced body mass gain in small passerines during migratory stopover under simulated heat wave conditions

For birds that migrate long distances, maximizing the rate of refueling at stopovers is advantageous, but ambient conditions may adversely influence this vital process. We simulated a 3-day migratory stopover for garden warblers (Sylvia borin) and compared body temperatures (Tb) and rates of refueling under conditions of a heat wave (Ta=40°C by day, and 15°C at night) with those under more moderate conditions (Ta=27°C by day, and 15°C at night). We measured Tb with implanted thermo-sensitive radio transmitters. Birds had significantly lower rates of body mass gain on the first day of stopover (repeated measures mixed model ANOVA, p=0.002) affecting body mass during the entire stopover (p=0.034) and higher maximum Tb during the day when exposed to high Ta than when exposed to moderate Ta (p=0.002). In addition, the birds exposed to high Ta by day had significantly lower minimum Tb at night than those exposed to moderate daytime Ta (p=0.048), even though Ta at night was the same for both groups. We interpret this lower nighttime Tb to be a means of saving energy to compensate for elevated daytime thermoregulatory requirements, while higher Tb by day may reduce protein turnover. All effects on Tb were significantly more pronounced during the first day of stopover than on days two and three, which may be linked to the rate of renewal of digestive function during stopover. Our results suggest that environmental factors, such as high Ta, constrain migratory body mass gain. Extreme high Ta and heat waves are predicted to increase due to global climate change, and thus are likely to pose increasing constraints on regaining body mass during stopover and therefore migratory performance in migratory birds.

Noninvasive Evidence of Shortened Atrial Refractoriness during Sinus Rhythm in Patients with Paroxysmal Atrial Fibrillation

Shortening of the atrial refractory period is the key feature of atrial electrical remodeling during atrial fibrillation (AF). During sinus rhythm (SR), assessment of the atrial refractoriness is hampered by the fact that the atrial repolarization wave (Ta wave) is largely obscured by the following QRST complex. The purpose of this study was to study the Ta wave in subjects with paroxysmal AF during SR with third-degree atrioventricular (AV) block, and in matched controls. Fifteen patients (mean age 70 +/- 10 years, five males) with paroxysmal AF undergoing AV-nodal ablation were studied. Fifteen age- and gender-matched subjects (mean age 71 +/- 9 years, five males) with third-degree AV block, without a history of heart disease, were used as controls. Standard 12-lead electrocardiograms (ECGs) were recorded and transformed to orthogonal leads and studied using P-wave signal averaging technique. The P to Ta interval was shorter (408 +/- 47 ms vs 451 +/- 53 ms, P = 0.017) and in Lead Y the Ta peak location was earlier (156 +/- 31 ms vs 187 +/- 34 ms, P = 0.002) in subjects with paroxysmal AF than in the controls. The P-wave duration (126 +/- 15 ms vs 129 +/- 17 ms, P = 0.59) and morphology was similar in AF patients and controls. In this study, the ECG signs of shorter atrial refractoriness associated with a history of AF are visualized for the first time during SR. The finding of the earlier location of the PTa peak in AF subjects implies that a possible indicator of increased arrhythmia susceptibility may be visible already in the unprocessed ECG.

Detailed ECG Analysis of Atrial Repolarization in Humans

Data on human atrial repolarization are scarce since the QRS complex normally obscures its ECG trace. In the present study, consecutive patients with third-degree AV block were studied to better describe the human Ta wave. Forty patients (mean age 75 years, 17 men) were included. All anti-arrhythmic drugs were discontinued before ECG recording. Standard 12-lead ECGs were recorded, transformed to orthogonal leads and studied using signal-averaged P wave analysis. The average P wave duration was 124 +/- 16 ms. The PTa duration was 449 +/- 55 ms (corrected PTa 512 +/- 60 ms) and the Ta duration (P wave end to Ta wave end) was 323 +/- 56 ms. The polarity of the Ta wave was opposite to that of the P wave in all leads. The Ta peaks were located at 196 +/- 55 ms in Lead Y, 216 +/- 50 ms in Lead X, and 335 +/- 92 in Lead Z. No correlation was found between P wave duration and Ta duration, or between Ta peak amplitude and Ta duration. The morphology of the Ta wave was similar regardless of the interatrial conduction. The Ta wave has the opposite polarity, and the duration is generally two to three times that, of the P wave. Although the Ta peak may occasionally be located in the PQ interval during normal AV conduction, it is unlikely that enough information can be obtained from analysis of this segment to differentiate normal from abnormal atrial repolarization. Hence, an algorithm for QRST cancellation during sinus rhythm is needed to further improve analysis.

The normal electrocardiogram of four species of conscious raptors

The aim of this study was to describe normal ECG patterns and values in four species of conscious raptors (Eurasian kestrel, Griffon vulture, Little owl, and Eurasian Eagle owl). Electrocardiograms were carried out in 75 conscious birds belonging to four species of raptors. Lead II waveforms were analysed to determine amplitudes and durations of waves and intervals. Morphologic patterns of P-QRS-T deflections were analysed in the six limb leads. Rhythm, heart rate, mean electrical axis, presence of Ta wave, ST slurring, and P-on-T phenomenon were also studied. The influence of species, body weight and heart rate in electrocardiographic variables were statistically analysed ( P < 0.05). Sinus rhythm was present in all tracings, showing sinus arrhythmia in four cases. Ta wave was present in six tracings and P-on-T phenomenon in four. ST segment could be identified in all tracings, being mainly high above baseline. Significant differences between species were found for all the electrocardiographic parameters. The heart rate and body weight were also found to be a significant influence in most parameters. This study provides electrocardiographic data for four species of raptors that can be used to establish comparisons for clinical purposes.

Cardiac memory in canine atrium : identification and implications.

Memory is a diverse biological phenomenon whose importance in the ventricle has been demonstrated. We hypothesized its occurrence in the atrium, contributing to the modulation of cardiac rhythm. We analyzed P and Ta waves in conscious chronically instrumented dogs with complete heart block. Animals were atrioventricularly sequentially paced at 5% greater than the sinus rate from the lateral right atrium (RA) during control, followed by 2 periods of 1-hour test pacing at 50% greater than the sinus rate, or by equivalent test pacing from the left atrial appendage (LAA) at 5% or 50% greater than the sinus rate. Recovery RA pacing periods of 20- and 30-minute duration, respectively, succeeded each test pacing period. RA test pacing at either rate did not affect the variables measured, but changing the pacing site from RA to LAA altered the P and Ta waves. Displacement of the spatial atrial gradient vector occurred during recovery from LAA pacing, was more marked at rapid pacing rates, and manifested accumulation and resolution consistent with cardiac memory. Concurrently, the right effective refractory period decreased. Memory is demonstrable in canine atrium, showing rapid onset, accumulation during successive pacing periods, and resolution on cessation of pacing. Given its association with a reduced effective refractory period, it may contribute to the substrate for atrial arrhythmias.