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Focal atrial tachycardia (AT) is uncommon and characterized by centrifugal atrial activation from a point source. ATs are found clustering around well-defined sites of structural and electrophysiologic heterogeneity in both atria. Focal AT most often occurs in patients without structural heart disease. The P-wave morphology on the surface ECG provides a good guide to the site of origin. With electrophysiologic study, activation mapping efforts can begin in the region suggested by P-wave analysis. Catheter ablation is an effective therapy that can result in long-term cure in most patients with a low risk of complications.

Woman 48 years old with progressive dyspnea, fatigue, dysphagia, lower limb edema, palpitations and decreased physical ability that made her to seek medical attention. The chest film showed severe cardiomegaly or "cor bovis" with cardiothoracic index of 0.78. The findings suggest a dilatation of both atria but mostly in the one. The echocardiogram shows severe mitral regurgitation consistent with rheumatic valve disease and "giant" left atrium. This was first described in 1938 by Semans and Taussig, is considered a rare finding and the principal cause is rheumatic mitral disease. This type of valve lesions are becoming less frequent as aneurysmal dilation. The diameters, the area and the calculated volume are shown as one of the greatest reported atrium.

To our knowledge, we describe the first case of a pseudoaneurysm of the mitro-aortic intervalvular fibrosa fistulizing into both atria, following an aortic bacterial endocarditis and valve replacement.

The objective of this study was to evaluate potential of Multiscale principal Analysis (MSPCA) to extract information of atrial electrograms as predictors of atrial fibrillation (AF) recurrence after ablation. Database is composed of intra-atrial recordings from 43 AF patients that were registered previous to an ablation procedure. MSPCA was applied to each atrium and main frequency and entropy were determined. We could find differences in main frequency in the left atrium between patients from both groups. Moreover, patients that maintenance sinus rhythm group showed a dominant atrial frequency trend from right to left atrium. In addition, non-recurrent AF group showed an enhancement of differences of regularity between both atria. These differences show the efficiency of MSPCA to characterize cardiac dynamic. High frequency values and not differences in main atrial frequency along the right atrium may indicate that AF reversion to sinus rhythm is more difficult.

Among the most difficult but fulfilling challenges to meet in the invasive electrophysiology laboratory is defining a reentrant circuit and choosing an effective ablation strategy. In this installment of teaching rounds, Ip et al1 elegantly discuss the deductive process involved when analyzing activation and entrainment data in a particularly instructive reentrant circuit involving both atria. See Article by Ip et al Can activation mapping define the mechanism of tachycardia?2 In general, a centrifugal spread from an apparent point source suggests an automatic focus, whereas the absence of such a spread would favor reentry. However, there are important exceptions that occur frequently enough that such a simple construct is rarely of sufficient practical value.

Myxoma, a rare type of intracardiac tumor, forms a very small percentage of the cardiac cases. Reports of biatrial myxoma are rarer, with cases of single tumor reaching both atria being more common. Here, we present an unusual case of two independently growing atrial myxoma in a 29-year-old female. We emphasize that early recognition of symptoms, confirmation of diagnosis by transesophageal echocardiography, and prompt surgical excision remain vital in the management of such patients. The patient in the present case was managed successfully with no evidences of recurrence at the last follow-up.

AF Cycle Length Detection Analysis. Introduction: Experimental models have demonstrated that atrial fibrillation (AF) may be due to one or more rapid drivers (source) producing AF. These drivers may be characterized by rapid and regular cycle lengths (CLs), producing fibrillatory conduction to the rest of the atria. The ability to reliably identify such drivers would be invaluable. The purpose of this study was to develop and validate a CL variability detection (CLVD) analysis capable of accurately determining beat-to-beat CLs of atrial electrograms (AEGs) during AF, and then to compare this analysis with dominant frequency (DF) analysis. Methods and Results: We analyzed 6 episodes of AF in 6 dogs (sterile pericarditis model) due either to a single, stable left atrial reentrant circuit, or unstable reentrant circuits causing fibrillatory conduction to the rest of the atria. During AF, AEGs were recorded simultaneously from 400 to 420 electrodes on both atria. CLs from over 20,000 AEGs were manually measured, and compared to CLs detected using both the CLVD and DF analyses. There was significant correlation between (1) CLs measured manually and the CLVD analysis (mean CL: correlation coefficient [CC]= 0.96, standard deviation [SD]: CC = 0.89); and (2) mean CL measured manually and the DF analysis (CC = 0.84). However, there was poor correlation between SD of CLs measured manually and the organization index (OI) by DF analysis (CC =–0.59). Conclusion: The CLVD analysis was validated as being accurate for detecting both rate and degree of regularity of AEGs during AF, and more accurate than DF analysis. (J Cardiovasc Electrophysiol, Vol. 24, pp. 199-206, February 2013)

An atrial septal aneurysm (ASA) is a rare but well-recognized abnormality of uncertain clinical relevance. It is a localized bulging of the inter-atrial septum into either or both atria during the cardiac cycle. ASA has been reported as an unexpected finding during autopsy but may also be diagnosed in living patients by echocardiographic techniques. We present a 37-year-old woman with a recurrent atypical chest pain of one-year duration. She was found to have a congenital atrial septal aneurysm on evaluation. The echocardiographic images mimicked a left sided cor triatriatum sinister. She had no other symptoms and had no co-morbidities. There was no audible murmur. ASA can mimic cor-triatriatum and echocardiographic examination should be performed from multiple views before any echocardiographic diagnosis is made.

Introduction. The existence of human cardiac stem cells (hCSC) and their regenerative capacity are not fully defined. The aim of this study was to identify and analyse the distribution of hCSCs by flow cytometry (FCM). Methods. Tissue samples from the left ventricle (LV) and the appendages of the right atrium (RA) and left atrium (LA) were taken during cardiac surgery. Mononuclear cells (MNCs) were isolated, labelled for the stem-cell-marker c-kit and hematopoietic-lineage markers and analysed by FCM. Results. HCSCs could be isolated from the RA, LA, and LV without significant quantitative difference between both atria (A) (RA 4.80 ± 1.76% versus LA 4.99 ± 1.69% of isolated MNCs, P=0.922). The number of hCSCs was significantly higher in both atria compared to the left ventricle (A 4.90 ± 1.29% versus LV 0.62 ± 0.14% of isolated MNCs, P=0.035). Conclusion. The atria contain a higher concentration of hCSC than the left ventricle. HCSCs located in the atria could serve as an endogenous source for heart regeneration.

Cardiac conduction abnormalities remain a major cause of death and disability worldwide. However, as of today, there is no standard clinical imaging modality that can noninvasively provide maps of the electrical activation. In this paper, electromechanical wave imaging (EWI), a novel ultrasound-based imaging method, is shown to be capable of mapping the electromechanics of all four cardiac chambers at high temporal and spatial resolutions and a precision previously unobtainable in a full cardiac view in both animals and humans. The transient deformations resulting from the electrical activation of the myocardium were mapped in 2D and combined in 3D biplane ventricular views. EWI maps were acquired during five distinct conduction configurations and were found to be closely correlated to the electrical activation sequences. EWI in humans was shown to be feasible and capable of depicting the normal electromechanical activation sequence of both atria and ventricles. This validation of EWI as a direct, noninvasive, and highly translational approach underlines its potential to serve as a unique imaging tool for the early detection, diagnosis, and treatment monitoring of arrhythmias through ultrasound-based mapping of the transmural electromechanical activation sequence reliably at the point of care, and in real time.

Characterization of Atrial Activation Intervals During AF. Background: The mean, median, and minimum local atrial activation (A-A) intervals have been used to determine the local atrial effective refractory period (AERP) during atrial fibrillation (AF), the underlying assumption being that AF is due to multiple reentrant wavelets. Objective: We tested the hypothesis that when AF is due to a single, rapid, stable reentrant circuit (driver), the minimum and mean local A-A intervals will be similar at sites in the reentrant circuit, but will vary widely at sites with fibrillatory conduction, making these latter intervals unreliable indicators of AERP. Methods: During sustained AF due to a left atrial (LA) driver in 6 sterile pericarditis dogs, electrograms were recorded from 186 bipolar electrodes from both atria. A-A intervals were measured from each recording site during 1.2 seconds of AF. Minimum A-A intervals as well as temporal (within site) and spatial (between sites) variability were determined from all sites. Results: A-A intervals from each site during AF demonstrated that (1) 90–100% of right atrial (RA) sites and 18–39% of LA sites showed considerable (SD > 6 ms) temporal variability; (2) RA and LA sites with fibrillatory conduction (SD > 6 ms) showed considerable (a) spatial variability (RA: 9–36 ms; LA: 5–27 ms) and (b) variability of the minimum A-A intervals (RA: 14–35 ms; LA 11–28 ms). Conclusion: During AF due to a driver, areas with fibrillatory conduction manifested considerable variability in the mean and the minimum A-A intervals. Therefore, it is unlikely that any of the A-A intervals reflect AERP. (J Cardiovasc Electrophysiol, Vol. 22, pp. 310-315, March 2011)

Substrate-based radiofrequency ablation for treatment of atrial fibrillation (AF) is still under development. The purpose of this study was to investigate the different characteristics and distribution of complex fractionated atrial electrograms (CFAE) in both atria in patients with paroxysmal and persistent AF. The NavX™ system was used to map the left and right atria and the coronary sinus in 20 AF patients (ten persistent). An automated algorithm calculates the average time interval between consecutive deflections (complex fractionated electrogram (CFE) mean). All recordings were visually inspected off-line and interpreted either as continuous, fragmented, mixed CFAE, or non-CFAE, and their locations were determined. Electrograms with intermittent CFAE characteristics were also regarded as non-CFAEs. There were more CFAEs in persistent AF than in paroxysmal AF (52% vs. 44% of total registrations, p

Rationale Myxoma is the most common type of primary benign cardiac tumor in adults. The left atrium is the most frequent site of origin followed by the right atrium. Biatrial myxoma is extremely rare. Patient concerns We present a case of a 60-year-old woman with biatrial myxoma, who presented with palpitations for one month. Diagnoses Echocardiography revealed an irregular homogeneous mass in the left atrium and in the right atrium, and were connected via the fossa ovalis suspiciously. Computed tomography angiography revealed a hypo-intense mass in both atria. Interventions The tumors were successfully removed by surgical excision and histological analysis confirmed the diagnosis. Outcomes The patient was discharged one week after surgery, and did not experience recurrence during the two years follow-up period. Lessons Biatrial myxoma is rare. Surgical resection is the mainstay of treatment and there is no recurrence reported. The clinical data and the features on echocardiogram of biatrial myxoma are reviewed, providing important clinical information for the pre-operative diagnosis and intraoperative removal of biatrial myxoma.

Most anatomical and physiological studies of the sauropsid heart have focused on species with extraordinary physiologies, and detailed anatomical descriptions of hearts from sauropsids with more com- mon physiologies are therefore warranted. Here, we present a comprehensive study of the cardiac anatomy of the South American rattlesnake (Crotalus durissus). The cardiovascular physiology of this species has been investigated in a number of studies, whereas only a few cursory studies exist on the cardiac anatomy of viperid snakes. The heart of C. durissus is typically squamate in many regards. Both atria are thin-walled sacs, and the right atrium is the most voluminous. The single ven- tricle contains three major septa; the vertical septum, the muscular ridge (MR), and the bulbuslamelle. These partially divide the ventricle into three chambers; the systemic and left-sided cavum arteriosum (CA), the pul- monary and right-sided cavum pulmonale, and the medial cavum venosum (CV). The MR is the most devel- oped septum, and several additional and minor septa are found within the CA and CV. An extraordinary thin cortical layer encloses the ventricle, and it is irrigated by a remarkably rich arborization of coronary arteries. Previous studies show high degrees of blood flow separa- tion in the Crotalus heart, and this can only be explained by the coordinated actions of the septa and the prominent atrioventricular valves. J. Morphol. 271:1066-1077, 2010. 2010 Wiley-Liss, Inc.

Background: Nonpulmonary vein (PV) ectopy initiating atrial fibrillation (AF)/atrial tachycardia (AT) is not uncommon in patients with AF. The relationship of complex fractionated atrial electrograms (CFAEs) and non-PV ectopy initiating AF/AT has not been assessed. We aimed to characterize the CFAEs in the non-PV ectopy initiating AF/AT. Methods: Twenty-three patients (age 53 ± 11 y/o, 19 males) who underwent a stepwise AF ablation with coexisting PV and non-PV ectopy initiating AF or AT were included. CFAE mapping was applied before and after the PV isolation in both atria by using a real-time NavX electroanatomic mapping system. A CFAE was defined as a fractionation interval (FI) of less than 120 ms over 8-second duration. A continuous CFAE (mostly, an FI < 50 ms) was defined as electrogram fractionation or repetitive rapid activity lasting for more than 8 seconds. Results: All patients (100%) with non-PV ectopy initiating AF or AT demonstrated corresponding continuous CFAEs at the firing foci. There was no significant difference in the FI among the PV ostial or non-PV atrial ectopy or other atrial CFAEs (54.1 ± 5.6, 58.3 ± 11.3, 52.8 ± 5.8 ms, P = 0.12). Ablation targeting those continuous CFAEs terminated the AF and AT and eliminated the non-PV ectopy in all patients (100%). During a follow-up of 7 months, 22% of the patients had an AF recurrence with PV reconnections. There was no recurrence of any ablated non-PV ectopy during the follow-up. Conclusion: The sites of the origin of the non-PV ectopies were at the same location as those of the atrial continuous CFAEs. Those non-PV foci were able to initiate and sustain AF/AT. By limited ablation targeting all atrial continuous CFAEs, the AF could be effectively eliminated.

The aim of this study was to determine the developmental anatomy of intrinsic cardiac ganglia with respect to epicardiac ganglionated nerve plexus in the human fetuses at different gestation stages. Twenty fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent examinations on total (non-sectioned) hearts. Most epicardiac ganglia embodied multilayered neurons and were oval in shape, but some ganglia involved neurons lying in one layer or had the irregular appearance because of their extensions along inter-ganglionic nerves. The mean ganglion area of fetuses at gestation stages of 15-40 weeks was 0.03 +/- 0.008 mm(2). The largest epicardiac ganglia, reaching in area 0.4 mm(2), were concentrated on the dorsal surface of both atria. The particular fused or "dual" ganglia were identified at the gestation stages of 23-40 weeks, but they composed only 2.3 +/- 0.7% of all found epicardiac ganglia. A direct positive correlation was determined between the fetal age and the ganglion area (mm(2)) as well as between the fetal age and the number of inter-ganglionic nerves. The revealed appearance of epicardiac ganglia in the human fetuses at 15-40 weeks of gestation confirms their prenatal development and presumable intrinsic remodelling.

We report a case of a 68-year-old man who had dialysis-related amyloidosis. The patient underwent neck surgery due to spondyloarthritis. Unfortunately he died after the surgery in sepsis. The preoperative routine echocardiography didn't suggest cardiac involvement of amyloidosis. However, the pathological findings in autopsy revealed severe amyloid depositions of both atria in contrast to the quite mild involvement of ventricles. We have experienced that the cardiac involvement of dialysis-related amyloidosis may be confined to atria almost sparing ventricles. Therefore, in patients with hemodialysis-related amyloidosis, even if echocardiogram doesn't suggest any ventricular amyloidosis, physicians should consider the possibility of atrial amyloidosis and should check the detail of atrial findings. If the A wave in the mitral filling pattern seems small or absent, physicians have to proceed transesophageal echocardiogram to detect intra atrial thrombus and consider anti-coagulation therapy to prevent thromboembolic complications of atrial amyloidosis.

Aims Fibrillatory waves observed in the surface electrograms may be a direct reflection of the electrophysiologic mechanism of the atrial fibrillation (AF). This study compared the fibrillatory waves in the surface ECG and the individual intracardiac mapping sites in different types of paroxysmal AF. Methods and results Thirty patients with paroxysmal AF originating from the pulmonary veins (PVs) or superior vena cava (SVC) were enrolled. Frequency analysis was performed on the intracardiac electrograms recorded from various mapping sites in both atria sequentially with simultaneous surface electrogram recordings. The SVC–AF patients had a trend toward a higher DF in ECG lead V1 when compared with the PV–AF patients (7.35+ 2.09 vs. 5.89+ 0.79 Hz, P ¼ 0.018). The mean dominant frequency (DF) of the LA mapping sites in the PV–AF patients was higher than that in the SVC–AF patients (7.06+ 0.66 vs. 6.13+ 0.96 Hz, P ¼ 0.009), whereas the mean DF of the RA mapping sites was similar between the two groups (5.84+ 0.80 vs. 6.26+ 1.11 Hz, P ¼ NS). The intra-class correlation coefficient (ICC) between the mean DF of the RA sites and V1 was higher (r ¼ 0.21, P ¼ 0.02) when compared with the mean DF of the LA sites (r ¼ 20.007, P . 0.05). Furthermore, the maximal ICC was observed in the anterolateral RA free wall (r ¼ 0.84, P , 0.001) and not the other anatomic sites of the RA and LA. Conclusion The fibrillatory activity observed in ECG lead V1 correlated primarily with the activity of the anterolateral RA free wall and thus may be useful for detecting the AF source if it is close to that area.

Cardiac navigation systems (CNS) are often used in electrophysiological studies to create spatial-electrical maps supporting the arrhythmia mechanism identification. Sequentially recorded electrograms yield the bioelectrical information from features such as voltage and activation times in terms of their spatial location, which are subsequently interpolated for building the electroanatomical map (EAM) of the cardiac chamber. Our goal was to evaluate quantitatively the effect of interpolation in the EAM accuracy when reconstructed from a set of samples. Triangulated irregular networks (TIN), thin plate spline (TPS), and support vector machines (SVM) were assessed by using: (a) two detailed simulated time activation maps during flutter and sinus rhythm in both atria; (b) a set of real CNS maps, given by 13 activation time and 19 voltage maps, with 6 right atria (RA), 6 left atria (LA), 4 right ventricles (RV), and 16 left ventricles (LV). Interpolation methods were benchmarked using root mean squared error (RMSE), efficiency (EF), and Willmott distance (WD). On the one hand, EF and WD were similar for yielding a clearer cut-off point than RMSE for the number of required samples, which was about 100. Better EAM accuracy was obtained using TPS, followed by SVM and TIN, except for flutter in the RA, where early-meets-late was smoothed by SVM. On the other hand, EAM accuracy (in terms of the average WD) was slightly outperformed by RA than LA (0.57 vs 0.52), whereas RV and LV were similar (0.71 vs 0.71). In reference to the methods, similar average WD was given by the interpolation methods (TIN 0.64 ± 0.14; TPS 0.66 ± 0.15; SVM 0.65 ± 0.18). The EAM accuracy is dependent on the map nature and on the cardiac chamber.

Atrial fibrillation (AF) is an abnormal heart rhythm originated in the top chambers of the heart. The goal of pulmonary vein ablation for AF is returning to normal heart rhythm; nevertheless restoration of sinus rhythm is difficult to prognostic. In order to predict AF recurrences regularity of atrial activity morphology was studied. Intracardiac recordings from 43 paroxysmal and persistent AF patients registered previous to ablation procedure were monitored after the intervention. Results showed differences in entropy measurements from dipoles located in the right atrium with lower values of entropy in the recurrent group than in group that maintain sinus rhythm (p=0.004). The same trend was showed by entropy measures from spatial correlation between dipoles located in the right atrium, with lower values in the non-recurrent group than in the group with AF recurrence (p=0.009). Moreover, differences between both atria were found in the non-recurrent group 4.11±0.01 in the left atrium vs. 4.07±0.01 in the right atria (p=0.04). These findings show that atrial activity is more regular in the right atrium in the patients with non recurrences in AF.

Purpose Heart failure (HF) with preserved ejection fraction (HFPEF) is the most prevalent type of HF in nonhospitalized patients, but its pathophysiology remains poorly understood. The aim of our study was to assess the existence of interatrial dyssynchrony (IAD), a potentially treatable condition, in the development of HF symptoms. Methods Consecutive patients with new onset of shortening of breath, referred for suspected HF, were screened. In all cases, a transthoracic echocardiography, ECG, and determination of plasma BNP level were performed at initial consultation. Patients were diagnosed according to current guidelines. Patients with HF and reduced ejection fraction were excluded. Later, the time from P‐wave onset on the ECG to peak negative strain (atrial contraction) was determined using speckle tracking echocardiography; the time difference between both atria (ms) was used as an index of IAD. Results Sixty‐six patients were included. Mean age was 74 ± 8 years (74% female, 77% hypertensive). HFPEF patients (n = 32) showed an increased IAD as compared to subjects with non‐HF (n = 34; interatrial time difference 72.7 ± 27 vs. 28 ± 7 ms, P < 0.001). IAD showed a significant correlation with BNP levels, diastolic pattern, and echocardiographic parameters indicative of elevated LV filling pressures. LA function assessed by LA strain rate was not significantly different between HPPEF patients with and without IAD > 60 ms. Conclusions We showed that IAD was present at initial stages of symptomatic HFPEF. It might be an important mechanism involved in the development of symptoms in HFPEF and a potential target amenable to be treated with device therapy.

We identified a case of paroxysmal atrial fibrillation (AF) originating from inferior vena cava (IVC) and the low-posterior left atrium (LA). Both foci, the IVC and the low-posterior LA, simultaneously served not only as trigger but also as driver for maintenance of AF. During AF, the IVC and the low-posterior LA continuously demonstrated the rapid and fractionated potentials that exit into both atria with conduction block. Focal ablation for ectopic beats within the IVC and the low-posterior LA completely eliminated the storm of AF.

We sought to define right atrial appendage (RAA) anatomic and functional parameters in a consecutive series of participants and to compare these measures with left atrial appendage (LAA) indices among patients with in sinus rhythm and atrial fibrillation (AF).With AF, both atria are fibrillating, yet the vast majority of thrombi are located within the LAA. Transesophageal echocardiography provides anatomic and functional information regarding both the LAA and the RAA.In a consecutive series of 92 patients (48 men; age 61 +/- 17 years) referred for transesophageal echocardiography, RAA and LAA anatomy (width, length, area) and ejection velocity were measured at two orientations (RAA, 90 and 135 degrees; LAA, 0 and 90 degrees).RAA anatomic measures were similar for both imaging planes, whereas LAA area was larger at 90 degrees. There was a modest correlation between RAA and LAA anatomic measures (area: r = 0.58, P = .001). RAA neck width was substantially greater than LAA neck width (P.0001) whereas appendage area was similar (P = not significant) and RAA neck width/area was greater than LAA neck width/area (P.0001). AF was associated with approximately 50% decline in ejection velocity for both the LAA and the RAA with an increase in LAA area (P = .006 vs sinus), but similar anatomic remodeling was not found for the RAA (P = not significant vs sinus).In this consecutive series of patients undergoing transesophageal echocardiography, RAA anatomic and functional parameters were found to be independent of imaging plane, with anatomic measures demonstrating a correlation with LAA measures. Although AF is associated with depressed RAA and LAA ejection velocities, anatomic RAA remodeling appears to be absent. The larger RAA width and lack of anatomic remodeling may partially explain the substantially lower prevalence of RAA thrombus found among patients with AF.

Background: Previous experimental studies have demonstrated electrophysiological and structural remodeling in pacing induced atrial fibrillation. The latter has been characterized by glycogen accumulation but no connection to atrial fibrillation induction and maintenance has as yet been proposed. Aims: We determined the presence of glycogen in the right and left atrial appendages in the goat heart, in order to find any intrinsic disparity in distribution and concentration between these sites. Materials and Methods: Atrial appendages from 5 goats were stained by the Periodic acid Schiff method to determine the presence of glycogen and the concentration of glycogen by morphometric analysis. Results: We are reporting for the first time that the right atrial appendage showed scattered glycogen granules throughout the atrial myocytes which delineated the intercalated discs; whereas glycogen in the left atrial appendage was more dense within cells and coalesced against the intercalated discs and side to side junctions between myocytes. Also, morphometric analysis determined that the stained regions of the right atrial appendages averaged, 0.8 ± 1.3 μm 2 compared to the left atrial appendage sections, 2.6 ± 3 μm 2 , p = 0.02. We show that glycogen is heterogeneously distributed in both atria in the normal goat heart; however, the density of glycogen deposits concentrating against the intercalated discs and side to side connections in the left atrial appendage is a critically distinct difference. Impediment of cell to cell conduction could result in a non-uniform wavefront of activation, with areas of slowed conduction, predisposing the left atrium to reentrant based atrial fibrillation. Conclusion: These findings provide a basis for the well-known greater propensity for atrial fibrillation in the left versus the right atrium.

Background: The atria are assumed to be connected electrically to each other at the level of the Bachmann's bundle, coronary sinus (CS) musculature, and interatrial septum, and these connections may have an important role in the interatrial conduction and perpetuation of various types of atrial tachyarrhythmias. However, the number, location, and preferential connections of the interatrial conduction related to the site of activation have not been examined yet. Methods: The endocardium of both atria and the CS were mapped during continuous pacing from the left superior and inferior pulmonary veins, right pulmonary veins, upper and lower right atrium, or right atrial septum at various paced cycle lengths in 14 canines. The electrograms were recorded by custom-made form-fitted electrodes mounted on a specially designed device that allowed the septal aspects of the electrode forms to be spatially fixed to each other accurately. Results: Four distinct interatrial electrical connections were identified at the Bachmann's bundle, CS, and antero-superior and postero-inferior septa. Decremental conduction was not seen in any of the connections. Bachmann's bundle was the most preferential connection during pacing from any epicardial site. The transseptal connections were evident only during pacing from the interatrial septum. The preference among the four connections was determined by the site of stimulation and the propagation of the activation related to the myocardial architecture. Conclusion: These unique preferential connections may play a significant role in the interatrial conduction and perpetuation of atrial tachyarrhythmias.

UNLABELLED Increased ECM in canine PVs. INTRODUCTION Cell uncoupling due to fibrosis or increased extracellular collagen matrix (ECM) affects the formation of ectopic focal activity. Whether or not the increase of ECM also exists in the pulmonary veins (PVs) with rapid atrial pacing is unknown. We sought to test the hypothesis that in chronic atrial pacing dogs with sustained atrial fibrillation (AF), the amount of ECM was increased in both atria and the PVs. METHODS AND RESULTS We induced sustained AF in dogs by rapid atrial pacing. Computerized mapping techniques were used to map both atria and the PVs. We also used histological assessment to quantify the amount of ECM. After 118+/-24 days of rapid atrial pacing, sustained AF was induced in 7 dogs. Repetitive rapid activities (RRAs) either continuously or intermittently arose from the PVs during sustained AF. Histological study shows that there was no fibrosis in both atrial free walls and the PVs. However, the amount of ECM was increased in these regions. The mean ECM surface area fraction at each region in the dogs with sustained AF was all significantly higher compared to the corresponding region in normal dogs. Similarly, the heterogeneity of the ECM surface area fraction at each region in the dogs with sustained AF was also all significantly higher compared to normal dogs. CONCLUSIONS In chronic atrial pacing-induced sustained AF, structural remodeling (i.e., inhomogeneous increase of ECM) also involves the PVs. Reduced coupling of the myocytes in the PV due to histological changes may provide an additional mechanism facilitating RRAs.

There is general agreement that AF is most likely a reentrant rhythm disturbance. However, the precise pathophysiological bases for its initiation and maintenance have not been fully resolved. In the original description of the multiple wavelet hypothesis of atrial fibrillation, as put forward by Moe et al. and later substantiated by Allessie et al., the wavelets were thought to move randomly throughout the atria. However, more recent studies that have applied high resolution mapping of wave propagation and rigorous analyses in the time and frequency domains to long episodes of AF, have provided evidence that atrial fibrillation is not random, but is accompanied by a high degree of spatiotemporal periodicity. This has led to the hypothesis that maintenance of AF may depend on the uninterrupted periodic activity of a small number of discrete reentrant sites, established by the interaction of propagating waves with anatomical heterogeneities in the atria. It has been proposed also that the rapidly successive wave fronts emanating from these sources propagate through both atria and interact with anatomical and/or functional obstacles, leading to fragmentation and wavelet formation. In support of this idea, observations made during radiofrequency ablation of AF in humans suggest that, in some patients, a single, repetitive focal source of activity propagate impulses from an individual pulmonary vein to the remainder of the atrium as fibrillatory waves. These studies underscore the need for identification of continuing AF sources at localized sites, and of transient AF "triggers", which may involve normal or abnormal pacemaker mechanisms or even reentrant activity, and of the manner in which electrical activity initiated by such triggers interacts with the normally propagating electrical waves to initiate fibrillatory activity in the atria.

Linear Lesions Prevent Atrial Fibrillation.Introduction: In the animal model, segmentation of the atria with radiofrequency-generated linear lesions (LL) using the loop catheter has been shown to be highly effective in terminating chronic atrial fibrillation (AF). This study addresses the question whether the same lesion set also would prevent reinduction and sustainability of AF. Methods and Results: We studied two groups of dogs. The AF group included eight dogs in which the atria were paced until chronic AF was present. After 6 months of sustained AF, the dogs were converted to normal sinus rhythm (NSR) by the creation of LL in both atria. Rapid atrial pacing was restarted 6 months later and continued for 4 weeks. In the NSR group, there were nine dogs in NSR without inducible AF at baseline. LL were created, and after 6 months rapid atrial pacing was applied for 4 weeks. Rhythm status was monitored weekly. Transthoracic echocardiography was performed at baseline, before linear lesion placement, and before pacing/repacing. At the conclusion of the study, the hearts were excised and examined. The lesions were stained, and their quality was assessed. AF was induced in a much shorter interval in the dogs in which AF had previously been present than in NSR dogs (8 ± 5 days vs 25 ± 13 days; P < 0.05). LL prevented sustainability of AF induced via rapid pacing once the pacing stimulus was stopped. Incomplete lesions were associated with increased inducibility of atrial tachycardia and AF. Conclusion: In this animal model of AF, LL are not only capable of terminating chronic AF, but also lead to self-termination of AF once the rapid pacing is stopped. Self-termination of AF after induction with rapid pacing was not observed in this AF model in the absence of LL. In the dogs with 6 months of AF, the presence of AF led to increased atrial susceptibility to AF induction by rapid pacing, even with LL and after 6 months of recovery. Incomplete LL allows induction of atrial tachycardia and AF.

Levels and distribution of heart monoamine oxidases (MAOs) were studied in male Sprague-Dawley rats of 3 (young) and 24 (old) months of age using biochemical and histochemical techniques. Biochemical assay of MAOs in atria and in ventricles showed a significant increase in MAOs levels in old in comparison with young animals. MAOs histochemical staining revealed an homogeneous distribution of the enzyme within both right and left atria and/or ventricles in 3-months-old rats. In 24-months-old rats an increase of MAOs reaction in comparison with younger animals was found. This increase is more consistent in the endocardial portion of the right atrium and in the endocardial portion of the left atrium. In 3-months-old rats MAOs reaction was slightly lower in the epicardial than in the endocardial portions of both atria and/or ventricles. In 24-months-old rats MAOs reaction showed a significant increase if compared with young rats. The significance of these data is discussed in relation to the role of MAOs in rat heart.

A British cat was presented with generalized fatty infiltration of the heart compromising both ventricles and atria, resembling arrhythmogenic right ventricular cardiomyopathy. Due to the nature and progression of the dis - ease, the final diagnosis was achieved at necropsy. According to our knowledge only a few cases of fatty infiltration of the heart have been reported in cats, this being the first in which the pathological findings were seen in both atria.

Introduction: Stable organized atrial tachyarrhythmias (ATs) /"rotors" that maintain AF have been identified in patients (pts) with paroxysmal atrial fibrillation (PAF) & persistent AF (PRAF) with no or minimal heart disease. Hypothesis: Biatrial ATs occur in AF pts with systolic heart failure (HF). Methods: We performed simultaneous contact catheter mapping of the RA & LA using 3 D non-contact mapping ) in 83 refractory AF pts during spontaneous AF episodes.Spontaneous atrial premature beats (APBs) & triggered ATs were analyzed. We also compared regional distribution of ATs & activation patterns in pts with & without HF. Results: 24 HF pts, mean age of 62±9 years, 75% male with mean left ventricular ejection fraction (LVEF) 45.5±9% and mean left atrial (LA) size 4.35±0.8 cm were mapped. They had 42 APBs that triggered 26 distinct organized stable ATs/"rotors". Each pt had 1 to 4 RA or LA regions showing triggering APBs (mean 1.75/pt) initiating AT. APBs arose predominantly from the RA or LA septum (45%) & superior LA/PV (24%) regions (Fig 1a). A biatrial distribution of the stable ATs/"rotors" occcurred in HF pts (Fig 1b) with few focal ATs. Compared to pts without HF (n=59), HF pts (n=24) trended to have more PRAF (83% vs 66%, p=0.18). 78 organized stable ATs/"rotors" were compared for regional distribution in PRAF pts with HF (n=16) & without HF (n=32). Stable ATs with focal LA/PV origin were uncommon in both groups (7% vs. 15%). LA ATs/"rotors" were similar (26% vs. 17%; p=0.58) as were typical RA flutter and atypical RA ATs/"rotors" in both groups (Fig 1c). Conclusions: 1. A majority of APBs initiating AF in HF pts originated from the septal and superior LA/PV regions. 2. While triggers are still frequently present with the LA/PV origin in HF pts, stable ATs/"rotors" had biatrial distribution & a lesser frequency of focal LA/PV ATs. 3. This spectrum of ATs/"rotors" was similar to PRAF pts without HF, potentially supporting similar ablative interventions in both pt groups.

Background Ventricular diastolic dysfunction in patients with repaired tetralogy of Fallot (TOF) may affect atrial mechanics. This study aimed to explore right atrial (RA) and left atrial (LA) mechanics in repaired TOF patients and their relationship with ventricular diastolic function. Methods Fifty-four patients (36 males), aged 17.8 ± 8.3 years, who had undergone TOF repair at 3.9 ± 3.3 years and 40 healthy subjects aged 16.9 ± 6.3 years (P = 0.57) were studied. Right and LA peak positive, peak negative, and total strain, strain rate at ventricular systole (SRs), early diastole (SRed), and atrial contraction (SRac), and electromechanical delay were determined using speckle tracking echocardiography (STE). Ventricular diastolic function was assessed by tissue Doppler imaging and STE. Ventricular volumes and pulmonary regurgitant volume were derived from 3D echocardiography. Results Compared with controls, patients had significantly lower RA and LA peak positive and total strain, SRs, SRed, and SRac (all P

GEPSTEIN, L., et al.: Accurate Linear Radiofrequency Lesions Guided by a Nonfluoroscopic Electroanatomic Mapping Method During Atrial Fibrillation. Catheter-based continuous linear lesions may become a curative procedure for AF. The accuracy of guiding the application of continuous RF lesions by a nonfluoroscopic mapping system (NFM) during AF in goats was tested. The NFM system (Carto) uses magnetic fields to determine, in real time, the location and orientation of a 7 Fr ablation catheter tip. AF was induced in nine goats by intravenous infusion of methacholine (3–4 μg⋅kg–1⋅min–1) and burst pacing. The three-dimensional atrial geometry was reconstructed using the median location of the mapping catheter tip during 30 seconds when in contact with each endocardial site. Sequential RF energy (60 seconds in a temperature-controlled mode [60°C]) was delivered along a predetermined path to create longitudinal lesions in both atria. Sites to which RF energy was applied were tagged on the NFM map, enabling the operator to accurately navigate the catheter tip to the adjacent sites. In all cases (n = 14) the location, shape, length, and continuity of the linear lesions on the electroanatomic maps highly correlated with the autopsy findings. Average line length on the reconstructed maps was 32.3 ± 4.1 mm, which highly correlated (r = 0.98, P

It has been suggested that the three-dimensional structure of the atria may be crucial in arrhythmogenesis; however, previous in vivo atrial activation mapping studies have been limited to either endocardial or epicardial approaches.To investigate the role of endocardial and epicardial structures and their interaction in atrial conduction and arrhythmias, we used five epicardial plaques and two intra-atrial balloon arrays to record a total of 368 unipolar electrograms from the entire epicardial and endocardial surface of both atria. During regular 1:1 pacing from the right atrial appendage, right atrial endocardial activation spread considerably faster than epicardial (total activation time 45+/-12 msec vs 60+/-19 msec, respectively [mean +/- SD]; P0.05), pointing to preferential conduction over structures like the crista terminalis and pectinate muscles. No such differences were noted in the left atrium. Transseptal spread occurred via discrete anterior and posterior pathways, causing separate breakthroughs in anterior and posterior atrial regions, respectively. Dissociation between septal pathways played a role in reentry during vagal atrial fibrillation. In 2 of 4 dogs with atrial fibrillation associated with congestive heart failure, single macroreentrant circuits involving endocardial and epicardial components were revealed during the arrhythmia.We conclude that activation mapping using simultaneous recording from both epicardial and endocardial surfaces provides potentially important insights into the mechanisms of atrial conduction and arrhythmogenesis.

Atrial fibrillation (AF) is often described as a disorganized phenomenon, but many features that qualitatively suggest an underlying order have recently been reported. The present study aimed to disclose this underlying order of AF in a quantitative manner, using a new method of mutual information (MI), which is a measure for gauging the general correlation between 2 time series. Frequency analysis and the MI method were used to analyze 5 epicardial potentials on both atria during AF induced by vagal stimulation (Vs) in 15 dogs. Unipolar electrodes were placed on the right atrial appendage (Rap), the high right atrium (HRA), and the left atrial appendage (Lap). The other 2 electrodes were placed equidistantly between HRA and Rap (RA1 - RA2). The power spectrum of AF had a discrete peak around 17 Hz during Vs. After Vs was stopped, the discrete peak shifted from 17 Hz to 7 Hz on all epicardial leads. Taking RA2 as a reference, MI was calculated between RA2 and each of the other electrodes. The MI values (0.066±0.005) were greater than 0.047 (the critical value for correlated data) even during Vs. The MI values increased significantly from the highly active process of AF during Vs to the less active one (0.126±0.006) before termination of AF. In addition, the MI values increased more at the electrodes close to RA2 (RA1 and Rap) than at those far from it (HRA and Lap). These findings suggest that multiple wavelets, which are not random, progressively organize into a few major waves toward the termination of AF; therefore, AF is not a random phenomenon in this model. (Jpn Circ J 2001; 65: 111 - 116)

Although electrophysiologic changes occur during atrial remodeling, little is known how remodeling affects atrial fibrillation (AF) organization. We hypothesized that, in animals with long-term rapid atrial rates and a rapid ventricular response, AF would be more disorganized than in animals with rapid atrial rates only. In 8 dogs, chronic AF was created by 6 weeks of continuous rapid atrial pacing. In this group, the ventricular response to AF was spontaneous and unaltered. Twenty-one epochs of AF were epicardially mapped from the right and left atria. In 6 dogs, chronic AF was also created with rapid atrial pacing, however, the AV node was ablated and the ventricles were VVI paced at 80 BPM. Only 1 epoch of AF per dog was mapped. Atrial cycle length (CL) and spatial organization were compared. In chronic AF with a spontaneous ventricular rate, left atrial CL (96+/-14 ms) averaged 24 ms shorter than right atrial CL (121+/-18 ms) (P.0001). With VVI pacing, AF CL was longer than in the dogs with the spontaneous ventricular rate. However, the left atrial CL (109+/-30 ms) was still significantly shorter than the right atrial CL (145+/-43 ms) (P.001). Spatial organization values showed that during chronic AF with a spontaneous ventricular rate, the left atrium is more disorganized (2593+/-497) than the right atrium (2052+/-732) (P.0001). With VVI pacing, the left atrium (2202+/-597) is still more disorganized than the right (1620+/-936) (P.05). However, with VVI pacing, both atria appear less disorganized than dogs with VVI pacing. Atrial remodeling caused by heart failure that is superimposed on the remodeling due to rapid atrial rates causes the atria to be more disorganized than remodeling due to rapid atrial rates alone. However, in either case the left atrium is faster and more disorganized than the right atrium. Atrial fibrosis caused by the heart failure may increase the disorganization of AF activation.

Several lines of evidence suggest that autonomic innervation plays a role in the generation of atrial fibrillation (AF). Ganglionated plexi (GPs) that modulate autonomic innervation have been identified over both atria, particularly the pulmonary vein (PV) antral regions. Stimulation of GPs results

Primary pheochromocytomas located outside the adrenal glands account for only 10% of all pheochromocytomas. Mediastinal pheochromocytomas are even rarer and usually represent a therapeutic challenge as they often infiltrate adjacent structures. We report the case of a large primary mediastinal pheochromocytoma in a 65-year-old patient presenting with a sudden angina-like chest pain and dyspnea. Thoracic multislice computed tomography showed an 8 x 5 x 6-cm retrocardiac mass causing compression of both atria and infiltrating the left superior pulmonary vein. The tumor was highly vascularized and presented a blood supply derived from the circumflex artery. The mass was successfully removed by open heart surgery, and the patient was discharged 10 days postoperatively.

A 52-year-old woman was admitted with the complaint of dyspnea that was present at rest and lasted a few hours. On bedside echocardiography, multiple small thrombus formations were detected in the right atrium under the tricuspid valve. Similar thrombus formation was detected in the left atrium. The lung perfusion scintigraphy indicated pulmonary embolism. Recombinant tissue plasminogen activator was started via intravenous infusion; after a dose of 60 mg, speech disturbance was observed, so thrombolytic therapy was terminated. The patient's speech problem subsided spontaneously. The dyspnea improved dramatically. Repeated bedside echocardiographic examination revealed the thrombi in both atria had disappeared.

1. The influence of hypoxia on the time course of regional myocardial accumulation and elimination of the beta 1-adrenoceptor antagonist metoprolol was investigated by a spontaneously beating rat isolated perfused heart preparation. 2. Myocardial metoprolol content was maximal at 2 min in the left and right ventricles and atria. Neither the extent nor the time of maximal myocardial metoprolol content was significantly influenced by the induction of hypoxia. However, maximal myocardial metoprolol content in both atria and right ventricles was significantly higher than that in the left ventricular samples (P < 0.02; one-factor analysis of variance, 17 d.f.). 3. Elimination of metoprolol (as indicated from residual myocardial metoprolol content at 10 min) was impaired in hypoxic left ventricles (P < 0.01 vs normoxia; unpaired t-test, 10 d.f.) but not in right ventricles or atria. This variation in myocardial metoprolol disposition was not apparent from examination of serial metoprolol concentrations in coronary perfusate. 4. Hypoxia selectively impaired the elimination of metoprolol from the left ventricle, but not the process of drug accumulation, by any region of myocardium. It remains to be determined whether this reflects regional variation in the extent of microcirculatory impairment associated with hypoxia.

The study was designed to identify the influence of ibutilide on activation during atrial fibrillation (AF) and determine its role in enhancing the efficacy of electrical conversion of AF. Vagally-mediated acute AF was induced in 12 anesthetized dogs. In 5 dogs, a cross-shaped epicardial patch containing 16 recording electrodes was placed on the right atrium. In 7 dogs, defibrillation patch electrodes overlying both atria were used to deliver biphasic shocks (50% tilt; 90 °F). Measurements were made at baseline and following ibutilide (0.075 mg/kg bolus followed by 0.075 mg/kg infusion over 10 minutes). Right atrial multisite electrogram recordings revealed significant prolongation in AF cycle length at all sites following ibutilide. In all dogs, AF cycle length increased with ibutilide from 90±23 to 130±49 ms (p < 0.005). Whereas, atrial defibrillation threshold decreased from 0.83±0.5 to 0.53±0.29 J (p =0.020). In conclusion, ibutilide prolongs cycle length of canine vagally-mediated acute AF. Furthermore, ibutilide facilitates electrical conversion of AF by lowering energy requirement. Thus, controlled drug infusion in conjunction with electrical defibrillation may be useful for managing AF.

Atypical atrial flutter has, hitherto, been relatively refractory totermination by rapid atrial pacing. High-frequency pacing (HFP) in theatrium, for termination of atrial flutter or atrial fibrillation (AF), andthe electrophysiologic effects related to it have not been examined. Weexamined the clinical efficacy, safety, and electrophysiologic mechanisms ofHFP using 50-Hz bursts at 10 mA applied at the high right atrium in patientswith atypical atrial flutter (group 1) or AF (group 2), using a prospectiverandomized study protocol. Four burst durations (500, 1000, 2000, and 4000ms) were applied at the high right atrium repetitively in random sequence in22 patients with spontaneous atrial flutter or AF. Local and distant rightand left atrial electrogram recordings were analyzed during and after HFP.HFP resulted in local and distant right and left atrial electrogramacceleration in 8 of 10 patients (80%) in group 1 but caused lessfrequent local atrial electrogram acceleration (6 of 12 patients) and nodistant atrial electrogram effects in group 2 (p < .05 versus group 1).The HFP protocol was effective in arrhythmia termination in 6 of 10patients in group 1 but in no patient in group 2 (p < .05 versus group1). Standard HFP protocol applied at the high right atrium can frequentlyalter atrial activation in both atria and can terminate atypical atrialflutter. Efficacy in AF is limited, probably due to limitedelectrophysiologic actions beyond the local pacing site.

There is increasing emphasis on the role of interatrial septal abnormalities, including patent foramen ovale and atrial septal aneurysm, in the genesis of stroke. However, a transseptal thrombus located in both atria is rarely visualized by echocardiography or other cardiac imaging techniques. It is also difficult to prove the mechanism of stroke in most clinical settings. In the present case of impending paradoxical cerebral embolism, the thrombus penetrating the atrial septal wall was visualized by transesophageal echocardiography. (Circ J 2005; 69: 246 - 248)

Primary cardiac lymphoma (PCL) is a rare malignancy, accounting for 1.3–2% of primary cardiac tumours. We report of a patient with a large PCL who presented with a very rare ECG: an advanced interatrial conduction disturbance of the Bachmann bundle highly suspicious to be due to tumour's involvement of interatrial connections between both atria across the …

To characterize biatrial phasic volumetric function in dilated and hypertrophic cardiomyopathy with cine magnetic resonance (MR) imaging.Eight patients with dilated cardiomyopathy (mean age, 47 years), eight with hypertrophic cardiomyopathy (mean age, 39 years), and eight healthy subjects (mean age, 41 years) underwent cardiac-gated long-axis cine MR imaging of both atria.Left atrial minimum volume averaged 94 mL +/- 37 (standard deviation) in dilated cardiomyopathy, 86 mL +/- 40 in hypertrophic cardiomyopathy, and 51 mL +/- 14 in control subjects (P = .04). Left atrial ejection fraction averaged 16% +/- 6 in dilated cardiomyopathy, 19% +/- 12 in hypertrophic cardiomyopathy, and 28% +/- 7 in control subjects (P = .03). Right atrial minimum volume and ejection fraction were not altered in either form of cardiomyopathy. The normalized filling and emptying rates of either atrium were decreased in both forms of cardiomyopathy.In mildly symptomatic dilated and hypertrophic cardiomyopathy, and left atrium is enlarged and its relative cyclic volume changes are reduced. The right atrium is of normal size, but its reservoir function is compromised particularly in dilated cardiomyopathy. Three-dimensional volume measurements with cine MR imaging enable the exposure of altered atrial volumetric function.

Atrial fibrillation (AF) is a chaotic (and lethal) cardiac rhythm disorder that profoundly affects the cardiovascular performance. Surgical therapeutic intervention has been the principal method of treatment in these cases. The standard method has been the scalpel based "maze" cut and sew procedure. The method aims at interrupting the circular electrical patterns that are responsible for the arrhythmia. Strategic placement of incisions in both atria terminates the formation and the conduction of errant electrical impulses, and channels the normal electrical impulse in one direction. Scar tissue generated by the incisions permanently blocks the paths of the impulses that cause AF, thus eradicating the arrhythmia. Microwave cardiac ablation is a relatively new concept for the clinical treatment of cardiac arrhythmias. It is a procedure in which oscillating electromagnetic energy is delivered to the myocardium (the heart muscle), via a probe, to create thermal lesions. The frequencies typically used for microwave medical ablation are 915 MHz or 2.45 GHz. The thermal lesions are relied upon to disrupt or eliminate the conduction pathways supporting arrythmia. This relatively new technology has accrued an impressive clinical history in terms of biophysical and clinical efficacy, safety and surgeons' satisfaction.

Introduction: Indications for implantable cardioverter defibrillators (ICDs) are growing. Based on controlled clinical trial data, ICDs are indicated for sustained ventricular tachycardia and episodic ventricular fibrillation, but have use for secondary prevention (prophylaxis) purposes as well. Implants will likely increase. For the average patient requiring an ICD, which device is best? Several types are available, including single-chamber (VVI) ICDs that pace and sense only in the right ventricle, dual-chamber (DDD) ICDs that pace and sense in both the atria and ventricles, and biventricular devices that coordinate activation in both left and right ventricular chambers. A device that can sense and pace in both atria and ventricles would seem preferable to a single-chamber device; not surprisingly, most ICD implants are dual-chamber devices. The Low Energy Safety Study trial (Gold; Unpublished data), comparing singleto dual-chamber ICDs, showed similar survival for both types of ICDs when adjusting for baseline characteristics. The risk of death was related to New York Heart Association class, age, tachyarrhythmias, and heart block; the study was nonrandomized.

The mechanism underlying atrial fibrillation (AF) remains poorly understood. Multiple wandering propagation wavelets drifting through both atria under hierarchical models are not understood. Some pharmacological drugs, known as antiarrhythmics, modify the cardiac ionic currents supporting the fibrillation process within the atria and may modify the AF propagation dynamics terminating the fibrillation process. Other medications, theoretically non-antiarrhythmic, may slightly affect the fibrillation process in non-defined mechanisms. We evaluated whether the most commonly used anaesthetic agent, propofol, affects AF patterns. Partial least-squares (PLS) analysis was performed to reduce significant noise into the main latent variables to find the differences between groups. The final results showed an excellent discrimination between groups with slow atrial activity during the propofol infusion. © 2012 Institute of Physics and Engineering in Medicine. © 2012 Institute of Physics and Engineering in Medicine., This work was supported by the Ministry of Education and Science of Spain. (Ref: EASI TEC2009-13939).