Post-operative atrial fibrillation is associated with a pre-existing structural and electrical substrate in human right atrial myocardium.

BACKGROUND: Post-operative atrial fibrillation (POAF) is a major health economic burden. However, the precise mechanisms in POAF remain unclear. In other forms of AF, sites of high dominant frequency (DF) in sinus rhythm (SR) may harbour 'AF nests'. We studied AF inducibility in relation to substrate changes using epicardial electrograms and cardiomyocyte calcium handling in the atria of AF naïve patients. METHOD: Bipolar electrograms were recorded from the lateral right atrial (RA) wall in 34 patients undergoing coronary surgery using a high-density array in sinus rhythm (NSR). RA burst pacing at 200/500/1000ms cycle lengths (CL) was performed, recording episodes of AF>30s. Co-localised RA tissue was snap frozen for RNA and protein extraction. RESULTS: Electrograms prolonged during AF (76.64±29.35ms) vs. NSR/pacing (p<0.001). Compared to NSR, electrogram amplitude was reduced during AF and during pacing at 200ms CL (p<0.001). Electrogram DF was significantly lower in AF (75.87±23.63Hz) vs. NSR (89.33±25.99Hz) (p<0.05), and NSR DF higher in AF inducible patients at the site of AF initiation (p<0.05). Structurally, POAF atrial myocardium demonstrated reduced sarcolipin gene (p=0.0080) and protein (p=0.0242) expression vs. NSR. Phospholamban gene and protein expression was unchanged. SERCA2a protein expression remained unchanged, but MYH6 (p=0.0297) and SERCA2A (p=0.0343) gene expression was reduced in POAF. CONCLUSIONS: Human atrial electrograms prolong and reduce in amplitude in induced peri-operative AF vs. NSR or pacing. In those sustaining AF, high DF sites in NSR may indicate 'AF nests'. This electrical remodelling is accompanied by structural remodelling with altered expression of cardiomyocyte calcium handling detectable before POAF. These novel upstream substrate changes offer a novel mechanism and manifestation of human POAF.

Revisiting heart activation-conduction physiology, part I: atria.

This discussion paper re-examines the conduction-activation of the atria, based on observations, with respect to the complexity of the heart as an organ with a brain, and its evolution from a peristaltic tube. The atria do not require a specialized conduction system because they use the subendocardial layer to produce centripetal transmural activation fronts, regardless of the anatomical and histological organization of the transmural atrial wall. This has been described as "two-layer" physiology which provides robust transmission of activation from the sinus to the AV node via a centripetal transmural activation front. New productive insights can come from re-examining the physiology, not only during sinus rhythm but also during atrial tachycardias, in particular atrial flutter and atrial fibrillation (AF). During common flutter, the areas of slow conduction, in the isthmus and following trabeculations, particularly the subendocardial layer confines conduction through the trabeculations which supports re-entry. During experimental or postoperative flutter, the circular 2D activation around the obstacle follows the physiological transmural activation. Understanding this physiology offers insights into AF. During acute or protracted AF, the presence of stationary or drifting rotors is characteristic and consistent with normal physiological 2D atrial activation, suggesting that suppressing physiological transmural activation of AF will permanently restore normal sinus node atrial activation. In contrast, during permanent AF, normal 2D activation is abolished; the presence of transmural, serpentine, and chaotic atrial activation suggests that the normal physiological activation pattern has been replaced by a new, irreversible variety of atrial conduction that is a new physiology, which is consistent with evolution of complex systems.

Sinus node dysfunction in atrial fibrillation patients: the evidence of regional atrial substrate remodelling.

AIMS: It remains unclear as to whether regional atrial substrates of certain areas of the atrium in patients with atrial fibrillation (AF) can be related to sinoatrial node dysfunction. We investigated the relationship between the biatrial substrate characteristics and sinus node function in these patients. METHODS AND RESULTS: The study enrolled 34 patients (aged 57 ± 11 years old; 20 males) who underwent catheter ablation for symptomatic paroxysmal AF. Sinus node dysfunction was defined as having corrected sinus node recovery time longer than 550 ms. Atrial substrate analyses of both atria and atrial conductive properties were investigated in patients with (Group 1) and without sinus node dysfunction (Group 2). The mean global bipolar voltage of both atria and the atrial refractory period were similar between the two groups. Regional analysis showed that the mean bipolar voltage for patients in Group 1 was lower than in Group 2 (1.0 ± 0.3 vs. 2.1 ± 0.7 mV, P < 0.001) only in the sinus node region, while the electrophysiological properties were similar for both groups in other anatomic regions of both atria. The right atrial total activation time was significantly longer (97 ± 9 vs. 89 ± 10 ms, P = 0.023) and the conduction velocity along the crista terminalis was significantly slower (1.0 ± 0.2 vs. 1.2 ± 0.3 m/s, P = 0.019) in Group 1 patients than in Group 2 patients. CONCLUSION: In patients with AF, regional atrial remodelling near the sinus node area was associated with sinus node dysfunction.

Rapid high resolution electroanatomical mapping: evaluation of a new system in a canine atrial linear lesion model.

BACKGROUND: A canine right atrial (RA) linear lesion model was used to produce a complex pattern of RA activation to evaluate a novel mapping system for rapid, high resolution (HR) electroanatomical mapping. METHODS AND RESULTS: The mapping system (Rhythmia Medical, Incorporated) uses an 8F deflectable catheter with a minibasket (1.8 cm diameter), containing 8 splines of 8 electrodes (total 64 electrodes, 2.5 mm spacing). The system automatically acquires electrograms and location information based on electrogram stability and respiration phase. In 10 anesthetized dogs, HR-RA map was obtained by maneuvering the minibasket catheter during sinus rhythm and coronary sinus pacing. A right thoracotomy was performed, and either 1 or 2 (to create a gap) epicardial linear lesions were created on the RA free wall (surgical incision or epicardial radiofrequency lesions). RA maps during RA pacing close to the linear lesions were obtained. A total of 73 maps were created, with 44 to 729 (median 237) beats and 833 to 12 412 (median 3589) electrograms (≤2 to ≤5 mm from surface geometry), resolution 1.8 to 5.3 (median 2.7) mm, and 2.6 to 26.3 (median 7.3) minutes mapping time. Without manual annotation, the system accurately created RA geometry and demonstrated RA activation, identifying the location of lines of block and presence or absence of a gap in all 10 dogs. Endocardial radiofrequency catheter ablation of a gap (guided by activation map) produced complete block across the gap in all 3 dogs tested. CONCLUSIONS: The new HR mapping system accurately and quickly identifies geometry and complex patterns of activation in the canine RA, with little or no manual annotation of activation time.

A novel manoeuvre for discerning supraventricular tachycardia mechanism.

AIMS: Discerning supraventricular tachycardia (SVT) mechanism during catheter ablation procedures can be difficult and time-consuming, which, when combined with diagnostic error, places patients at risk of unnecessary complications. Distinguishing atrial tachycardia (AT) from AV nodal re-entry tachycardia (AVNRT) may be particularly vexatious. Value-added techniques are thus always welcome, particularly if they are not time-consuming nor require complex intracardiac lead configurations. In this study, we assessed whether a new technique, simultaneous right atrial and right ventricular pacing (RA + RV) during ongoing SVT, met these criteria. METHODS AND RESULTS: Using a simple intracardiac lead configuration (right atrial appendage, His bundle, right ventricular apex), the response to RA + RV delivered at 80-90% of the SVT cycle length, was examined in 80 patients referred for catheter ablation. In each patient, the actual tachycardia mechanism was adjudicated by standard electrophysiologic criteria ± successful catheter ablation. Mechanisms of SVT included, non-exclusively, AVNRT (24 patients), accessory pathway-mediated (orthodromic) re-entry (AVRT; 23 patients), AT (10 patients), and sinus tachycardia (ST induced with isoproterenol; 49 patients). Immediately after cessation of RA + RV pacing during persistent SVT, the first intracardiac electrogram observed was right atrial in all AT whereas it was His bundle in all AVNRT. The response during AVRT was mixed. CONCLUSIONS: In this preliminary evaluation, RA + RV pacing appears to add value to the existing armamentarium of electrophysiologic indices to discern SVT mechanism, in particular with respect to discriminating between AVNRT and AT.

Differences in the pattern of ventricular activation in small rodents determined by morphological organization of the cardiac ventricular conduction system.

Ventricular activation of the mouse heart differs significantly compared to activation in larger mammals. Knowledge of structural and functional characteristics of laboratory animals is essential for evaluation of results obtained from experiments. The present study was performed to evaluate whether the different pattern of activation is common to small rodents or unique for mice. Hearts of adult Wistar rats were isolated and Langendorff perfused. After removing the right and left ventricular free wall, extracellular activity of the septum and bundle branches (BB) was determined using a multi-terminal electrode harboring 247 terminals. Immunolabeling on cryosections was performed to assess expression and distribution of the gap junction proteins Connexin40 (Cx40), Cx43, Cx45, contractile (Desmin, alpha-actinin) and intercalated disk-related (N-cadherin, beta-catenin) proteins. Collagen distribution was assessed by Sirius Red staining. Reconstruction of the left and right bundle branch (LBB and RBB) using immuno-labeling revealed that the LBB spreads all over the septal surface. The RBB too is broad, albeit to a lesser extend than LBB. A sheet of connective tissue electrically separates the common bundle and proximal BB from the septal working myocardium. Immunolabeling revealed clear differences between the conduction system and the working myocardium with respect to expression level and distribution of the different proteins analyzed. The morphological organization of the area resulted in an electrical activation pattern of the septum comparable to what is common in larger mammals: earliest activation at the midseptum via the bundle branches. From our data we conclude that the pattern of ventricular activation in the rat heart and the structure of the conduction system fit to data described for larger mammals and differ from the different pattern previously found in mouse heart.

Adenosine can also improve the conduction between the superior vena cava and right atrium after isolation.

A 64-year-old man with atrial tachycardia (AT) 3 years after a superior vena cava (SVC) isolation for atrial fibrillation underwent electrophysiologic testing. SVC mapping with a basket catheter revealed a more frequent activation in the SVC than in either of the atria during the AT and consequently the recovered conduction between the SVC and right atrium. The conduction improved from 3 or 4-1 conduction to 2-1 conduction after adenosine was administered. Ectopic firing in the SVC persisted even after restoration of sinus rhythm by the successful SVC isolation, which was confirmed by adenosine.

Differences in the aging-associated trends of the monophasic action potential duration and effective refractory period of the right and left atria of the rat.

BACKGROUND: The incidence of atrial fibrillation (AF) increases with aging, but the aging-associated electrophysiological changes of atrial myocardium are poorly understood. METHODS AND RESULTS: Based on the hypothesis that aging of the atrium enhances AF susceptibility, 30 Wistar rats were divided into 3 age groups: adult, middle-aged, and aged (n=20 per group). Their hearts were isolated and perfused by Langendorff apparatus. Monophasic action potential duration at 90% repolarization (MAPD(90)) and effective refractory period (ERP) at the basic stimulation cycle length (BCL: 400 ms), and MAPD(90) at other different stimulation cycle lengths in each age group were measured. At the BCL, the MAPD (90) of the right atrial myocardium was prolonged from the adult to the aged group, that of the left atrial myocardium was prolonged from the adult to middle-aged group, and the MAPD(90) of the left atrial myocardium in the aged group were shorter than that in the adult and middle-aged groups. The ERP of the atrial myocardium showed the same age-associated trend as MAPD(90). As the stimulation frequency increased, the MAPD(90) of both the left and right atrial myocardium shortened correspondingly in the adult and middle-aged groups, but in the aged group the MAPD(90) of the right atrial myocardium shortened markedly more than that of the left atrial myocardium. CONCLUSIONS: There are different aging-associated electrophysiological changes in the right and left atrium, and the older heart is more vulnerable to developing the substrate for AF.

Atrial electrophysiologic abnormalities in patients with Wolff-Parkinson-White syndrome but without paroxysmal atrial fibrillation.

BACKGROUND: Paroxysmal atrial fibrillation (PAF) frequently occurs in patients with Wolff-Parkinson-White (WPW) syndrome. HYPOTHESIS: The purpose of this study was to analyze the atrial electrophysiologic abnormalities and vulnerability to develop atrial fibrillation (AF) in patients with WPW syndrome but with no previous history of PAF. METHODS: We investigated atrial electrophysiologic abnormalities and vulnerability to AF in patients with WPW syndrome but without PAF. An electrophysiologic study was performed in 28 patients with WPW syndrome, 23 with atrioventricular nodal reentrant tachycardia (AVNRT) and 25 with other arrhythmias (control), all of whom had no history of PAF. The following atrial excitability parameters were assessed: effective refractory period (ERP), spontaneous or paced (A1) and extrastimulated (A2) atrial electrogram widths, percent maximum atrial fragmentation (%MAF; A2/A1 x 100), wavelength index (WLI; ERP/A2), and inducibility of AF. RESULTS: The ERP tended to be shorter in patients with WPW syndrome and in those with AVNRT than in the control group. The %MAF increased (154 +/- 33 vs. 137 +/- 23%, p < 0.05) and WLI decreased (2.7 +/- 0.8 vs. 3.4 +/- 1.0, p < 0.05) significantly in patients with WPW syndrome compared with the control group; however, these parameters in patients with AVNRT showed intermediate values. Atrial fibrillation was more inducible in patients with WPW syndrome (4/28 [14.3%]) than in those with AVNRT (4.3% [1/23]) and the control group (0/25 [0%]). With respect to patients with WPW syndrome and with and without inducible AF, the %MAF increased (195 +/- 23 vs. 148 +/- 30%, p < 0.01) and the WLI decreased (2.2 +/- 0.3 vs. 2.9 +/- 0.9, p < 0.05) in subjects with inducible AF. CONCLUSIONS: Atrial electrophysiologic abnormalities, especially atrial conduction delays, are more prominent in patients with WPW syndrome, even if they had no previous history of PAF. These abnormalities may play an important role in determining the vulnerability to AF.

[Arrhythmia induction during atrial pacing with atrial floating electrodes]. / Inducción de arritmias durante la estimulación auricular mediante electrodos flotantes auriculares.

Atrial pacing with floating electrodes primarily designed for single lead VDD systems has disadvantages attributable to the floatability of the electrodes. Body and breathing movements cause changes in the position of the atrial dipole that can lead to failure of atrial capture and sensing, and even alternation of the stimulated chamber. We report the induction of typical intranodal tachycardia episodes related to intermittent failure of atrial capture in a patient with an implanted single lead DDD pacing system. Such systems pose a substantial risk of potentially arrhythmogenic asynchronous pacing.

Global dispersion of right atrial repolarization in healthy pigs and patients.

OBJECTIVE: To investigate the feasibility of monophasic action potential (MAP) mapping using an electroanatomical mapping system (CARTO) in obtaining information on global dispersion of atrial repolarization and to evaluate the role of dispersion of repolarization in the genesis of paroxysmal atrial fibrillation (PAF). METHODS AND RESULTS: Right atrial MAPs were recorded from 53 +/- 18 sites in 10 healthy pigs and 33 +/- 21 sites in 6 patients with and 4 patients without history of PAF. In pigs, the global dispersions of activation time (AT), MAP duration and end of repolarization time (EOR), 70 +/- 8, 95 +/- 18 and 121 +/- 28 ms, respectively, were significantly greater than those among 10, 20 and 30 sites. In patients with PAF, the global dispersions of MAP duration and EOR (128 +/- 10 and 149 +/- 31 ms) were significantly greater than those in patients without PAF (84 +/- 10 and 91 +/- 17 ms). CONCLUSION: MAP mapping using the CARTO system was feasible in experimental and clinical settings in obtaining information on global dispersion of atrial repolarization. The number of recording sites could significantly affect repolarization parameters. The dispersions of atrial repolarization were significantly greater in patients with PAF than those without, suggesting the involvement of an increased dispersion of repolarization in the genesis of PAF.

A model for in vivo validation of linear lesions in the right atrium.

UNLABELLED: Linear lesions have been proposed for treatment of complex atrial arrhythmias including atrial macroreentry tachycardia and compartmentalization in atrial fibrillation. AIM: To judge the effectiveness of a given lesion design, definite endpoints are necessary to ascertain the completeness of the line of block produced. METHODS AND RESULTS: We report validation criteria for long linear lesions in the right atrium in 42 pts, that combine both conventional and 3D mapping information (CARTO). Transferring from the validation of bi-directional block of the cavotricuspid isthmus line for atrial flutter, we validated 2 additional long linear lesions in the right atrium (anterior line and intercaval line). In addition to a complete isthmus line in all 42 pts, in 28 pts a complete anterior line was achieved and validated by both conventional and CARTO criteria. A complete intercaval line was deployed in 11 pts with complete anterior and isthmus lines (with a characteristic shift for the intercaval line) and in 5 pts without a complete anterior line (without characteristic shift). CONCLUSIONS: Conventional catheters placed at strategic locations on opposite sides of the intended ablation line, can depict a sudden characteristic change in the activation sequence. Using a combination of both techniques, deployment and validation of long linear lesion can be facilitated.

Conduction velocity around the tricuspid valve annulus during type 1 atrial flutter: defining the location of areas of slow conduction by three-dimensional electroanatomical mapping.

BACKGROUND: Conduction velocity (CV) around the tricuspid valve annulus (TVA) during type 1 atrial flutter (AFL) has been shown to be slowest in the tricuspid valve-inferior vena cava (TV-IVC) isthmus, compared to the septal or free wall segments of the TVA. However, fiber orientation in the triangle-of-Koch suggests that the inferior septum and medial TV-IVC isthmus should be the most slowly conducting segments around the TVA. METHODS: To test this hypothesis we evaluated CV around the TVA during type 1 atrial flutter in 11 patients, using an electro-anatomical mapping system (Carto). CV was first calculated in 4 segments around the TVA including the TV-IVC isthmus, lateral free wall, superior free wall and septum, and then calculated in 8 segments around the TVA including medial (MI) and lateral isthmus (LI), inferior (IL) and superior lateral (SL) free wall, lateral (LS) and medial superior (MS) free wall, and superior (SS) and inferior septum (IS). Statistical comparison of CV from these multiple segments was made by one-way analysis of variance. RESULTS: Measured in 4 segments around the TVA, mean CV (m/sec) in the TV-IVC isthmus (0.81 +/- 0.23) and the septum (0.93 +/- 0.18) was significantly slower than CV in the lateral free wall (1.16 +/- 0.23) and superior free wall (1.10 +/- 0.20), and CV in the TV-IVC isthmus was significantly slower than in the septum (p < 0.05). However, when analyzed in 8 segments, mean CV in the MI (0.56 +/- 0.16) and IS (0.59 +/- 0.24) was significantly (p < 0.05) slower than in all other segments including the LI (1.06 +/- 0.46), IL (1.17 +/- 0.40), SL (1.15 +/- 0.40), LS (1.04 +/- 0.25), MS (1.15 +/- 0.28), and SS (1.26 +/- 0.36) segments. CONCLUSIONS: Consistent with previous reports, CV around the TVA during type 1 AFL was slowest in the TV-IVC isthmus, compared to the septum, superior and lateral free wall regions. However, when the TVA was further subdivided into 8 segments, CV in the MI and IS segments was significantly slower than in all other segments around the TVA. These observations more precisely define the regions of slow conduction in human type 1 AFL, and are consistent with the known anisotropy and slow conduction in the Triangle of Koch.

Bi-atrial mapping of atrial arrhythmias.

Cardiac mapping of atrial activation was originally performed in animals during open chest preparations, using epicardial electrodes. The development of endocardial egg-shaped multiple electrodes provided detailed assessment of the minimum number of wavelengths required to sustain atrial fibrillation (AF), as well as the role of interatrial connections during AF. Subsequently, several studies on bi-atrial epicardial high-density mapping in animals and humans also reported on the importance of interatrial connections, as well as the specific characteristics of the left atrium as compared with the right atrium during chronic AF. Endocardial bi-atrial mapping studies using electrode catheters were reported using basket-shaped catheters carrying 64 electrodes. Animal studies suggested that septal activation was asynchronous and discordant, while a human study outlined the multiple origins of atrial ectopic beats following DC cardioversion in patients with chronic atrial fibrillation. The advent of non-fluoroscopic mapping systems significantly changed our approach to percutaneous endocardial mapping. Simultaneous bi-atrial studies using electroanatomic mapping were performed in sinus rhythm as well as in atrial flutter. These studies demonstrated the predominance of interatrial conduction over Bachmann's Bundle and the coronary sinus-left atrial connection during respectively, sinus rhythm and atrial flutter. Simultaneous bi-atrial non-contact mapping was initially performed during porcine studies and later in humans, demonstrating asynchronous and discordant septal activation both during sinus rhythm or left lateral atrial pacing. Preliminary studies from simultaneous bi-atrial non-contact mapping in humans in whom AF occurred spontaneously or was induced suggests three main types of atrial activation, consisting of left atrial drivers causing the right atrium to fibrillate following conduction over interatrial connections, the right atrium independently sustaining AF, even after pulmonary vein disconnection, and both atria fibrillating independently without activation over interatrial connections. Bi-atrial mapping has been essential for our understanding of normal and abnormal atrial activation, and ultimately may provide new approaches for ablation of atrial fibrillation.

Extended distribution of prolonged and fractionated right atrial electrograms predicts development of chronic atrial fibrillation in patients with idiopathic paroxysmal atrial fibrillation.

INTRODUCTION: This study evaluates whether electrophysiologic abnormalities in patients with idiopathic paroxysmal atrial fibrillation (PAF) predict the transition to chronic atrial fibrillation (CAF). METHODS AND RESULTS: Ninety-six patients with idiopathic PAF underwent electrophysiologic study and were followed up. During electrophysiologic study, endocardial mapping was performed at 12 sites in the right atrium (four aspects of the high, middle, and low right atrium). During follow-up of 60 to 130 months, conversion from PAF to CAF was observed in 17 patients (CAF group). The remaining 79 patients remained in sinus rhythm (PAF group). Although a high frequency of abnormal atrial electrograms was observed in the high right atrium in both groups, the frequency of those recorded from the middle right atrium was significantly higher in the CAF group than in the PAF group (70.6% vs 13.9%, P < 0.0005). Kaplan-Meier analysis showed that >50% of the patients with abnormal atrial electrograms in the middle right atrium developed CAF after 10 years, whereas only 7% of patients without those developed CAF (P < 0.0001). CONCLUSION: Our data suggest that extended distribution of abnormal atrial electrograms from the high to middle right atrium is predictive of the development of CAF in patients with idiopathic PAF.

Conduction properties of the crista terminalis and its influence on the right atrial activation sequence in patients with typical atrial flutter.

The conduction properties of the crista terminalis (CT) and its influence on the right atrial activation sequence were analyzed in 14 patients with typical atrial flutter (AF). Atrial mapping was performed with 35 points of the right atrium during typical AF and during atrial pacing performed after linear ablation of inferior vena cava-tricuspid annulus (IVC-TA) isthmus. Atrial pacing was delivered from the septal isthmus at cycle lengths of 600 ms and the tachycardia cycle length (TCL). The right atrial activation sequence and the conduction interval (CI) from the septal to lateral portion of the IVC-TA isthmus were analyzed. During AF, the conduction block line (CBL) (detected by the appearance of double potentials along the CT and craniocaudal activation on the side anterior to CT) was observed along the CT in all patients. The TCL and CI during AF were 254 +/- 19 and 207 +/- 14 ms, respectively. During pacing at a cycle length of 600 ms, the CBL was observed along the CT in four patients, however, a short-circuiting activation across the CT was observed in the remaining ten patients. The CI during pacing at 600 ms was 134 +/- 38 ms, shorter than that during AF (P < .0001). During pacing at the TCL, the CBL was observed along the CT in all patients. The presence of the CBL along the CT prevented a short-circuiting activation across the CT and resulted in the same right atrial activation as observed during AF. With the formation of the CBL, the CI significantly increased to 206 +/- 17 ms and was not different from that during AF. These data suggest that the conduction block along the CT is functional. It was presumed that presence of conduction block at the CT has some relevance to the initiation of typical AF though it was not confirmed.

Electrical conduits within the inferior atrial region exhibit preferential roles in interatrial activation.

Differences between conduction properties of interatrial conduits and their roles in initiation and maintenance of supraventricular arrhythmias remain unclear. Our objective was to determine details of interatrial activation in inferior atrial region and to correlate intra-atrial and interatrial activation patterns with the site of origin of atrial ectopic activation. In 9 dogs, basket-catheters carrying 64 electrodes were deployed into both the right atrium (RA) and left atrium (LA). A 10-electrode catheter was inserted into the coronary sinus (CS). Activation patterns of the RA, LA, and CS were compared during pacing in the CS, in RA inferoparaseptum posterior to Eustachian ridge-tendon of Todaro (TT), and in inferior RA near the CS ostium (anterior to TT). We found that pacing in proximal and middle CS resulted in a RA breakthrough invariably at the CS ostium, consistent with conduction through a CS-RA connection. Meanwhile, LA breakthrough emerged in inferoposterior region (inferior to mitral annulus), suggesting conduction through a CS-LA connection. While pacing in distal CS, LA breakthrough shifted to middle posterolateral wall. Whereas, the RA was activated by the LA directly through the septum. During pacing in RA inferoparaseptum posterior to TT, the LA was activated directly through the septum at 22 +/- 4 ms. Whereas, during pacing anterior to TT, the LA was activated through both the CS and the septum while earliest activation was delayed by 38 +/- 5 ms. In conclusion, both the interatrial septum and CS musculature form electrical conduits in inferior atrial region in canine. Differences in activation properties between the conduits in inferior interatrial region result in selective interatrial activation patterns during ectopic activation.

Localization of the initial fibrillatory cycle in patients with paroxysmal atrial fibrillation.

BACKGROUND: Recent reports suggest the presence of conduction delay in the posterior septal region during sinus rhythm in patients with lone paroxysmal atrial fibrillation (AF). OBJECTIVE: To explore the location of intra-atrial conduction delay associated with initiation of AF. DESIGN: In 8 lone AF patients (51 +/- 10 years), 20 AF paroxysms were induced during electrophysiological examination. Bipolar electrograms were acquired from a 10-polar catheter in the coronary sinus (CS), a 4-polar His bundle catheter, and a 20-polar Halo catheter in the right atrium. RESULTS: Induced AF paroxysms showed earliest registered atrial activity in interatrial septum (IAS) or proximal CS in 17 cases (85%). Conduction delay at the posterior IAS or proximal CS accompanied induction of 18 AF paroxysms (6 patients). Atrial activation sequence at the beginning of the AF paroxysms was stable and reproducible in six repeatedly induced AF episodes (3 patients). CONCLUSION: In lone AF patients, induction of AF is associated with conduction disturbances in the IAS and proximal CS regions.

Optimization and mechanism of step-leap respiration exercise in treating of cor pulmonale.

The interaction between cardiovascular system and the respiratory system is complicated and may be used for the rehabilitation of the cor pulmonale disease. To study the effects of different breathing mode on the cardiac and pulmonary systems, a mathematical model is established based on the previous work. Using this model, computer simulation experiments are carried out for searching an optimal respiration mode in treating of cor pulmonale disease. Results indicate that the step-leap respiration mode could provide a better assistant to the rehabilitation of the cor pulmonale patients in the sense of increasing coronary flow, reducing pulmonary arterial pressure and reducing the working load for the right heart. This result is also proven by the clinical experiments. This work may suggest that a proper directed respiration exercise can be used in the treatment of cor pulmonale disease.