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Using an experimental model of pulmonary hypertension in rats (monocrotaline in a dose of 60 mg/kg), we revealed an additional focus of early excitation in the zone where the pulmonary veins enter the left atrium, in addition to the main focus in the sinoatrial node. Pulmonary hypertension leads to the formation of regions of early activation in the right and left atria and a significant change in the sequence of atrial depolarization. Propagation of independent excitation waves in the right and left atria increases heterogeneity of depolarization and leads to the formation of atrial arrhythmias.

The standard 12-lead Electrocardiogram (ECG) system is the most commonly used technique for obtaining the electrocardiographic signal to evaluate the heart’s electrical activity. In the surface ECG, atrial repolarization (Ta wave) is not observed. However, during the exercise stress test, ST-segment depression validates the existence of Ta wave.To record the Ta wave and enhance atrial depolarization (P wave) in Sinus Rhythm (SR) ECG, Modified Limb Lead (MLL) system is used. PTa Interval (PTaI) represents the duration from the beginning of P wave to the end of Ta wave. This study aims to develop a corrected PTaI (PTac) formula to correct the PTaI from MLL ECGs for different heart rates. ECGs were recorded from 35 volunteers in SR and Sinus Tachycardia (ST) condition of mean age 24 ± 5 years using EDAN PC ECG system. Regression analysis was implemented on the recorded data to derive the slope for PP Interval (PPI) vs. PTaI plots in both groups. In SR group, PPI correlated well with PTaI (r = 0.48) compared to the ST group (r = 0.17). A new corrected PTaI (\({\text{PTa}}_{\text{c}} {\text{N}}\)) formula was developed from the slope values of SR and ST and compared with the previously developed PTac formula. The developed PTac formula of this study showed accurate results with the least slope in different heart rates. Implementation of new PTac formula in automatic algorithms further improves the clinical diagnosis related to atrial ECG components.

Aim . To determine the dispersion deviations of low-amplitude oscillations of the cardiac cycle in Magadan adolescents with different levels of activity of the sympathetic link of autonomic regulation (according to the heart rate variability — HRV). Material and methods . We analyzed ratios of HRV and ECG dispersion mapping (DM ECG) of the heart among male volunteers aged 15-17 years. The initial activity level of their autonomic nervous system (ANS) was characterized by sympathetic orientation (60 of 260 people): moderate — group 1 (n=43) and pronounced — group 2 (n=17), respectively. Results . When comparing the indices of HRV with the averaged DM ECG values for the “Rhythm” characteristic in group 2, the range of University, Magadan; 3Magadan regional center of medical prevention, values corresponded to 24-62% (normal — 20%), significantly exceeding the values characteristic for group 1 (14-37%). The values of the integral indicator “Myocardium” in both groups approached the upper limit of normal (15-17%). The greatest number of non-zero values indicating similarities with the standards of pathology was observed in terms of G1-G2 and G9. The values of G1 and G2 indicators in both groups of volunteers were comparable and, on average, did not exceed 6 relative units, while the range of fluctuations of the G9indicator in the first group was within 4 relative units, and in the second group — 7 relative units, respectively. Conclusion . In groups with moderate and elevated levels of central regulatory contour influence on the heart rhythm, ECG DM indicators showed the same type of similarity with the pathology standards in atrial depolarization processes at different types of potential localization causing it (G1 — G2). However, with pronounced centralization, deviations of the cardiac rhythm and dispersion characteristics from the norm were more often observed, similarities were found in the increased variations in the velocity characteristics of the initial ventricular depolarization front (G9), which is an unfavorable prognostic sign.

The electrophysiologic study is performed by inserting electrode-tipped catheters into the body and positioning them within the heart. In a typical diagnostic study, the baseline intracardiac intervals, RR, AH, and HV, are measured, and the responses to pacing from different sites in the atria and ventricles are analyzed. Precise measurements of AV conduction can be performed with intracardiac recording. In addition to the basic surface ECG measurements of the PR, QRS, QT, PP, and RR intervals, in an electrophysiologic study, atrioventricular conduction can be further analyzed by quantifying the AH and HV intervals. Significantly prolonged AH intervals in the lack of reversible factors may represent high vagal tone, intrinsic AV nodal disease, or conduction down the slow pathway of the atrioventricular node. Retrograde conduction, measured by the VA interval, the time between ventricular depolarization to the earliest atrial depolarization is also helpful in the study of supraventricular tachycardias.

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.

Proposed algorithms for P-wave identification and segmentation usually search for it within a window just before the R peak, thus hypothesizing the presence of at most one P wave, as it is in a normal electrocardiographic (ECG) tracings. In presence of abnormal atrial depolarization, however, there might be no P waves (as in atrial fibrillation) or multiple P waves (as in second- or third-degree atrioventricular blocks). Thus, this study proposes a new Adaptive Threshold Identification Algorithm (AThrIA) for ECG P-waves whose most innovative feature is to look for P waves all along the heartbeat, potentially allowing multiple P-waves identification. AThrIA ability to identify and segment (finding onset, maximum and offset) P waves was tested in simulated and experimental ECG tracings with no P waves, one P wave and two P waves, respectively. All P waves involved in the study were annotated. Results indicate that AThrIA correctly identified all P waves (no false-negative or false-positive detections). Segmentation errors were 0 ms for the simulated ECG tracings, and no more than 10 ms for the experimental tracings. Thus, AThrIA represents a promising tool for P-wave identification and segmentation in both physiological (one P wave) and pathological (none or multiple P waves) conditions.

Atrial fibrillation is the most common sustained cardiac arrhythmia which is often troublesome to manage. Currently, rhythm and rate control medications are the mainstays of therapy. In 2 amiodarone-refractory highly symptomatic patients, an innovative approach using ranolazine, which selectively acts on Na+ channels and delays atrial depolarization, was tried successfully.

By electrocardiotopographic method the dynamics of electrical field has been studied on the body surface of newborn nestlings of the pied flycatcher (Ficedula hypoleuca) at the period of atrial depolarization. On the body surface there have been revealed two shifts of zones of positive and negative cardiopotentials of the heart electrical field, which are due to peculiarities of sequence of atrial depolarization, anatomical immaturity of atrial structures, and the presence of closed foramen ovale.

There are three categories of atrioventricular (AV) block: first-, second-, and third-degree. First-degree AV block is manifest only by a prolongation of the PR interval beyond 0.2 s. The essential element of both second- and third-degree AV block is a “dropped beat,” in this case meaning an atrial depolarization (P wave) not followed by a ventricular depolarization (QRS complex). Second-degree AV block is subdivided in Mobitz I (or Wenckebach) block or Mobitz II. Mobitz I has the characteristic of increasing prolongation of sequential PR intervals until there is a “dropped beat,” a P wave not followed by a QRS. Mobitz II is a higher degree of block where only a fraction (for example, 1 of 3) of the P waves is followed by a QRS, and the PR interval for that conducted beat may be normal or prolonged but is generally fairly constant. Third-degree AV block (also known as complete heart block) is manifest by the absence of conduction from atria to ventricles and the presence of atrioventricular dissociation, where the atrial depolarization (P waves) occurs at one rate and the ventricular depolarization (QRS complexes) appear at a totally unrelated, slower rate.

The electrocardiogram (ECG) is a graphical representation of the electrical activity of the heart. It is an important tool in the care of many patients with potential cardiovascular disease. Learning ECG interpretation logically starts with knowing the normal ECG and its normal variants. The cardiovascular system changes, like most biological systems do as the child grows towards adulthood. This chapter reviews the normal behavior of electrical changes throughout the cardiac cycle and the expected normal ECG findings of various ages as well as the variants of normal ECG.

Background: Measuring body surface potentials in the assessment of the electrical activity of the heart is the most commonly used noninvasive method for diagnosing cardiac arrhythmias. Paroxysmal atrial fibrillation (PAF) patients have disturbed cardiac electrophysiology but the detailed characteristics of atrial activation on the body surface are unknown. Methods: P waves from 60 sites on the body surface were analyzed from 10 PAF patients in sinus rhythm (PAF group) and 10 healthy controls (HC group). Evolution of atrial depolarization was described qualitatively by maps of P-wave amplitudes. P-wave dipole evolution was described quantitatively by measuring the changing location (body site) and amplitude of the dipole positive and negative pole peaks. Results: Both groups exhibited similar dipolar structure with an area of positive and an area of negative potentials. Over the depolarization cycle, there were significant changes in the location of the dipole with the positive pole rotating anteriorly right to left by two electrode sites (10 cm) (P = 0.001). There were significant differences between groups with the positive pole in PAF offset to the right of the chest by 0.43 (0.38) strips compared to HC (P < 0.007). Compared to controls, the PAF group positive poles reached peak amplitude sooner (49 [11] ms vs 65 [14] ms, P = 0.012) and negative poles reached peak amplitude later (74 [13] ms vs 62 [8] ms, P = 0.019). Conclusion: Atrial depolarization is characterized by a single dipole with time-varying amplitude and orientation with significant differences in dipole trajectory between patients with PAF and HCs. (PACE 2012;00:1–8)

Objective: Isolated atrial amyloidosis (IAA) is associated with atrial tachyarrhythmias. However, only a few studies have appraised atrial tachyarrhythmias and atrial depolarization abnormalities in connection with high-grade IAA. We conducted a collaborative retrospective study to assess this association. Methods: One hundred consecutive autopsied hearts were studied histologically for IAA. To increase the specificity for atrial depolarization abnormalities in this preliminary study, we excluded those specimens with intermediate amyloid involvement, i.e. IAA grades 1 and 2 (grade 0 = absent or trivial deposits; grade 1 = small deposits; grade 2 = moderate deposits; grade 3 = dense, large deposits). We then screened for baseline, premortem electrocardiograms (ECGs) to assess rhythm. In those with sinus rhythm, the P wave axis, duration, dispersion and terminal force in V1 were determined under magnification. Results: Of the 27 premortem ECGs corresponding to the autopsy specimens with grades 3 (sample) or 0 (controls) IAA, 9 showed sinus rhythm, 13 showed atrial fibrillation, 1 showed atrial flutter and 4 were uninterpretable. Fourteen autopsied hearts (52%) were positive for grade 3 IAA. Ten of those had atrial tachyarrhythmias (9 atrial fibrillation and 1 atrial flutter) compared to 4 of the 13 hearts with grade 0 IAA (72 vs. 31%, respectively; p = 0.03). Although there was excellent interobserver agreement using intraclass correlation coefficients, there were no significant differences in P wave measurements among the small number of patients with sinus rhythm for grade 3 versus grade 0 IAA. Conclusion: In a collaborative, preliminary, pilot assessment of autopsied hearts for which premortem ECGs were necessarily screened retrospectively, significantly more hearts with high-grade IAA were associated with atrial tachyarrhythmias compared to those with low-grade IAA. A larger study with an appropriately matched autopsy control group is needed to confirm these and previous observations.

P-wave widening on the 12-lead electrocardiogram denotes abnormal atrial depolarization and has been shown to be associated with myocardial ischemia during treadmill exercise tolerance testing. However, its true significance during dipyridamole (Persantine) stress imaging remains questionable given the potential direct as well as indirect effects of dipyridamole on the atria. We present a novel series of 5 comparable cases of dipyridamole stress imaging where serial P-wave duration increase occurred during administration of dipyridamole. We observed that such P-wave widening occurred even in the absence of evidence of myocardial ischemia on subsequent myocardial perfusion imaging. Clinicians should therefore be aware of this potential association where, unlike that observed with graded exercise treadmill testing, P-wave widening during dipyridamole infusion could perhaps be a pharmacological effect on the atria instead of an indication of underlying myocardial ischemia.

As the electrical source of hearts, sino-atrial node cells (SANCs) play significant roles in rhythmic firings. Due to the complex structure and function of SANCs, electrical interactions of SAN and its surrounding atrium has not yet been fully understood. The aim of the present study is to investigate effects of coupling conductance between SAN and atrial cells as well as the ectopic beats in atrium on automaticity of the SAN by computer simulation methods. On the basis of a dynamic mathematical single cell model considering the heterogeneity of central and peripheral SANCs, a two-dimensional inhomogeneous tissue slice including SAN and atrium was developed. The operator splitting method was used to integrate the tissue model. The results demonstrated that the coupling conductance between SAN and atrium had effects on the direction of spontaneous action potential conduction in SAN. Weak coupling resulted in a shift of the earliest pacemaker site from central to peripheral SANCs. Additionally, the ectopic beat-induced excitation in atrium was found to be able to enter into and overdrive suppress the automaticity of SAN. Even if the ectopic beat was delivered after the spontaneous firing had started in central SANCs, the spontaneous conduction toward the periphery could also be suppressed by the retrograde activation from the entering atrial depolarization wave. These findings suggested a direct link between sinus node dysfunction and atrial arrhythmias, and therefore were helpful in explaining the role of atrium in sinus node dysfunction.

Relata-se o caso de um cão, sem raça definida, levado ao veterinário por apresentar cansaço fácil e episódios de síncope. Foram identificadas fibrilação atrial e extra-sístoles ventriculares isoladas ao exame eletrocardiográfico. O tratamento antiarrítmico não foi eficaz, e o animal morreu devido a um episódio de síncope. À necropsia, observou-se massa em região de base cardíaca, invadindo a luz do átrio esquerdo. Histologicamente, constatou-se a presença de quimiodectoma. A infiltração miocárdica atrial causou lesões nos miócitos, produzindo circuitos reentrantes e/ou focos ectópicos de despolarização atrial.

Cardioelectric field (CEF) on the body surface of birds (hen and pigeon) at the period of atrial excitation was studied by the method of the 64-channel synchronous electrocardiotopography. At the period of the atrial depolarization in the birds the zone of CEF negative potentials on the body surface is located cranially with respect to the zone of positive potentials. At the initial moments of P wave the minimum is located in the cranial (hen) or middle (pigeon) third of the dorsal body surface, while the maximum—in the area of the heart projection onto the ventral (hen) or left-lateral (pigeon) body surface. The maximum and minimum of the potential reach the greatest value at the period of the middle part of the P wave (near the peak), their amplitude being higher in pigeons. The distribution dynamics of the CEF potentials on the body surface is similar in different bird species and is characterized by stability in mutual disposition of positive and negative zones. The interspecies and intraspecies CEF variability on the body surface at the period of the atrial activation seems to be due to differences in the heart disposition in the chest. At the period of the atrial myocardium activation, CEF on the bird body surface reflects adequately projection of the potential distribution on epicardium and the sequence of spreading of excitation in the atrial myocardium, including that in the presence of several fronts of depolarization waves.

Each wave deflection on the ECGrepresents a portion of the heart’selectrical activity and is labeled inthe same way it has been labeled forthe past 100 years: the P wave repre-sents atrial depolarization (contrac-tion), the QRS complex representsventricular depolarization, and theT wave represents ventricular repo-larization (relaxation). Atrial repo-larization occurs concurrently withventricular depolarization and istherefore masked within the QRScomplex (Figure 2).When reference is made to theQT interval, one is interested in thetime it takes for the ventricles to relax,or more accurately, the duration ofventricular repolarization. Length-ening of ventricular repolarization

This report describes the occurrence of prolonged atrial escape intervals (AEI) initiated by sensing of ventricular premature complexes (VPC) without a preceding atrial depolarization or an AV delay in two patients with DDD pacemakers with an atrial-based lower rate response. The prolonged AEIs were due to ventriculoatrial cross-talk so that atrial sensing of the far-field R wave of the VPCs occurred before detection of the R wave by the ventricular channel as a near-field signal. Early atrial sensing of the far-field R wave was promoted by a high atrial sensitivity and/or low ventricular sensitivity and was eliminated by reducing atrial sensitivity and/or increasing ventricular sensitivity. This manifestation of far-field sensing should not be interpreted as malfunction of dual chamber pacemakers with atrial-based lower rate timing.

The origin of the term P wave datesback to Eindhoven, who originally had labeled the electrical signals from the heart as A,B,C, and D. The great Dutch electrocardiographer, concerned about possible additional deflections to the left of A, chose to start again in the middle of the alphabet. Hence, atrial systole came to be called P (I). Now, a century later, we should not be too certain that to the left of P there are no new humps still to be named or more likely, renamed.

During dual chamber pacing, repetitive ventriculoatrial (VA) synchrony secondary to retrograde conduction can occur whenever otherwise effectual atrial stimuli fall continually within the atrial myocardial refractory period generated by preceding unsensed retrograde atrial depolarization. The latter falls within the pacemaker atrial refractory period and cannot initiate endless loop tachycardia, another form of repetitive VA synchrony secondary to a reentrant process through the pacemaker and the heart. This report describes the usefulness of Holter recordings in the diagnosis of repetitive nonreentrant VA synchrony and documents initiation and termination of this process by a ventricular extrasystole.

The ability of single paced ventricular beats during tachycardia to penetrate the tachycardia circuit and reset the subsequent atrial depolarization (atrial preexcitation), enabling calculation of the "preexcitation index," can be helpful in analyzing supraventricular tachycardias. However, the ventricular refractory period often prevents ventricular capture of beats with the necessary prematurity to demonstrate atrial preexcitation, particularly in atrioventricular nodal reentrant tachycardia (AVNRT). We hypothesized that the use of double premature stimuli could overcome this limitation. In 25 consecutive patients with either AVNRT or atrioventricular reciprocating tachycardia (AVRT) we attempted to demonstrate atrial preexcitation with single and double ventricular extrastimuli. Whereas atrial preexcitation with a single extrastimulus could only be achieved in 3 of 11 patients with AVNRT, all but 1 patient demonstrated atrial preexcitation with the use of double ventricular extrastimuli. On the other hand, in all but 1 patient with AVRT, atrial preexcitation could be achieved with single and double extrastimuli. A formula was derived for obtaining a preexcitation index with double extrastimuli and shown to correspond closely with the preexcitation index obtained with a single extrastimulus in the 16 patients in whom atrial preexcitation could be achieved with single and double extrastimuli. Thus, this technique significantly enhances the ability to achieve atrial preexcitation and to calculate the preexcitation index in patients with AVNRT, and thus may be useful in deciphering tachycardia mechanism in some patients, as well as being a useful technique in studying the electrophysiological properties of the antegrade and retrograde limbs of AVNRT.

Objective Arterial hypertension is associated with the risk of developing atrial arrhythmia. This research was aimed at studying the sequence of depolarization along the atrial epicardium and formation of the cardioelectric field on the body surface of hypertensive rats. Methods The study was carried out on eleven ISIAH rats (with hereditary stress-induced hypertension). We analyzed spatial-temporal characteristics of body surface potential map (BSPM), time characteristics of electrocardiogram during atrial depolarization, sequence of atrial epicardial depolarization of rats. Statistical analysis was performed using independent samples t-test. Results The results indicated that in 27% of hypertensive rats in the pulmonary vein (PV) sleeves, early excitation areas are formed 2.0 ± 0.5 ms after the beginning of depolarization of the sino-atrial node area, in 73% of animals, the area of the PV sleeves is excited 6.5 ± 0.4 ms after the beginning of depolarization. In experimental animals, the beginning of inversion of areas of positive and negative cardioelectric potentials on BSPM does not differ. In 73% of rats, duration of inversion on BSPM was 7.7 ± 1.9 ms, and in 27% - 3.9 ± 0.1 ms (p=0.011). The formation of early activation zones in PV of rats with arterial hypertension testifies to possible wandering focus in the myocardium of PV sleeves. Stress-induced hypertension results in actual risk of atrial arrhythmias, which originate at the base of the PV. Conclusion In rats with arterial hypertension, two early depolarization zones are revealed in the sinus node area and in the PV return to the left atrium, projected on BSPM by mutual positions of negative and positive potential zones.

We performed ambulatory 24-hour esophagus ECG in nine patients with dual chamber pacemakers suspect of transient arrhythmias in order to achieve correct and reliable P wave identification during daily life activities. In all patients episodes were observed with varying atrial artifact to left atrial depolarization sequences. These episodes probably reflected presence of atrial fusion systole, an ECG phenomenon which should be taken into account when analyzing ambulatory esophagus ECG. Thus, the ambulatory esophagus ECG revealed its ability to detect spontaneous atrial depolarization in the presence of pacemaker artifact in patients with DDD(R) pacemakers.