Low Lateral Right Atrium Research Articles

PO-03-098 DIFFERENTIAL PACING FOR IDENTIFYING MULTIPLE INTERATRIAL CONNECTIONS

Interatrial connection (IAC) is reported to be an anatomical structure associated with complex biatrial tachycardias. However, electrophysiological conduction between left atrium (LA) and right atrium (RA) has not been fully investigated. This study was to distinguish multiple IACs by using different pacing sites. Twenty patients with paroxysmal atrial fibrillation who underwent ablation were enrolled. High-density mapping of left and right atrial before ablation were created during continuous pacing from sinus node (SN) or low lateral RA (LL-RA), and LA appendage (LAA) or posterior wall (LA-PW), respectively. Focal activation sites were defined as IAC and breakthrough segments of each atrium were recorded. The average number of total IAC were 4.9±1.3 and 4.1±1.2 for RA-LA and LA-RA, respectively (Figure A1,2). There was no significant difference in number of IACs between each directional connections (cranial pacing, p=0.35; caudal pacing, p=0.62) (Figure B). Connections at the level of interatrial septum (IAS) and Bachmann’s bundle were mostly found as RA-LA connections, however more than one third of the patients had connections in right pulmonary veins, its carina, LA roof and coronary sinus musculature. LA-RA connections were mainly existed in IAS, however superior and inferior vena cava were also frequently related. Only either single site from SN or LL-RA pacing elucidated significantly smaller number of IACs for RA-LA compared to total IACs (SN vs total, 3.2±0.8 vs 4.9±1.3, p<0.001; LL-RA vs total, 3.2±1.5 vs 4.9±1.3, p<0.001) (Figure C1). Similarly, only either LAA or LA-PW pacing revealed significantly smaller number of IACs for LA-RA compared to total IACs (LAA vs total, 3.0±0.8 vs 4.1±1.2, p<0.001; LA-PW vs total, 3.0±0.8 vs 4.1±1.2, p<0.001) (Figure C2). Although difference of pacing sites did not influence the total number of interarial conductions (RA-LA, p=0.09; LA-RA, p=0.85), pacing from cranial and caudal sites preferentially disclosed IAC at upper and lower septal segments, respectively (upper connections of RA-LA, SN vs LL-RA, 73.4% vs 46.9%, p=0.0037; upper connections of LA-RA, LAA vs LA-PW pacing, 66.1% vs 41.0%, p=0.013) (Figure D1,2). Pacing from multiple locations may be required in order to reveal entire interatrial connections.

DELAYED LEAD PERFORATION OF THE RIGHT ATRIUM IN THE PRESENCE OF PERSISTENT LEFT SUPERIOR VENA CAVA: A RARE COINCIDENCE

DELAYED LEAD PERFORATION OF THE RIGHT ATRIUM IN THE PRESENCE OF PERSISTENT LEFT SUPERIOR VENA CAVA: A RARE COINCIDENCE

Rate-Dependent and Site-Specific Conduction Block at the Posterior Right Atrium and Drug Effects Evaluated Using a Noncontact Mapping System in Patients with Typical Atrial Flutter

Conduction block in the posterior right atrium (RA) plays an important role in perpetuating atrial flutter (AFL). Although conduction blocks have functional properties, it is not clear how the block line changes with the pacing rate, pacing site, and administration of antiarrhythmic drugs. Forty patients with typical AFL were enrolled. Pacing (110, 170, 230 ppm) from the coronary sinus ostium (CSo) and low lateral RA was performed. After 1 mg/kg pilsicainide (pure sodium channel blockade) administration, the pacing protocol was repeated. Conduction block was assessed based on a color-coded isopotential map and 20 points of virtual unipolar electrograms in the posterior RA using noncontact mapping. Block line proportion was defined as the percentage of length of the block line between the superior and inferior vena cava. The pacing rate-dependent extension of the block proportion was significant during pacing from both sides (pacing from the CSo: 59 ± 17% at 110 ppm, 69 ± 16% at 230 ppm, P < 0.05; pacing from the low lateral RA: 43 ± 19% at 110 ppm, 55 ± 22% at 230 ppm, P < 0.05). The block line was significantly longer during CSo pacing than during low lateral RA pacing at each rate (all P < 0.05). After pilsicainide administration, the block line extended further. In addition to pacing rate-dependent and site-dependent changes in the block line, pilsicainide further extended the block line length. This phenomenon explains the clinical observation that counterclockwise AFL occurs more frequently than clockwise AFL, and the mechanism of class IC AFL.

A Case with Macroreentrant Atrial Tachycardia around Sinus Venosa Region—Demonstration of Conduction across Crista Terminalis after Cavotricuspid Isthmus Block—

A 66-year-old mas was referred to our hospital for frequent episodes of palpitation. 12-lead ECG showed typical atrial flutter (AFL) with 2:1 atrioventricular conduction, which spontaneously turned into atrial fibrillation (AF). Radiofrequency (RF) ablation was performed and circumferential pulmonary vein isolation was successfully achieved. Linear ablation of cavotricuspid isthmus (CTI) was also added for typical AFL and bidirectional conduction block at the isthmus was confirmed by widely splited double potentials recorded at CTI and significant prolongation of conduction time between coronary sinus ostium (CSos) and low lateral right atrium (LLRA). Subsequently, atrial tachycardia (AT) was induced by atrial burst pacing. During the AT, electroanatomical mapping showed macroreentry pattern around the sinus venosa region, where double potentials were recorded by a mapping catheter. Ablation was performed during AT to create block line between sinus venosa and inferior vena cava and AT terminated during RF application. After completion of the block line, conduction time between CSos and LLRA prolonged from 152 ms to 169 ms. This is the first case report that could demonstrate the conduction across crista terminalis in a case with typical AFL.

Ablation of Right-Sided Accessory Pathways With Atrial Insertion Far From the Tricuspid Annulus Using an Electroanatomical Mapping System

It is difficult to ablate a right-sided accessory pathway (AP) with atrial insertion far from the tricuspid annulus (TA). We report our initial experience of ablating this rare AP by a 3-dimensional electroanatomical mapping system (CARTO). From January of 2006 to April of 2008, 18 patients with right-sided APs who failed previous outside ablations were enrolled in this study. Retrograde AP conduction was mapped during pacing at the right ventricular apex by activation-mapping the right atrium (RA) using a 3-dimensional electroanatomical mapping system. AP atrial insertion was defined as the earliest retrograde atrial activations and successful ablation of the APs at this site. Among the 18 patients who had failed previous ablation, 10 patients (7 patients with right manifest APs and 3 patients with right conceal APs) had atrial insertions far from the TA. Of the 10 patients, the atrial insertions were found at the base of the RA appendage in 3 patients, at the high lateral RA in 5 patients, at the low lateral RA in other 2 patients. Ablation at the atrial insertions successfully abolished the AP conduction. The mean distance between the atrial insertion sites and the TA was 20.2 ± 2.7 mm. No patients reported recovered AP conduction or recurrent tachycardias after 6-month follow-up. The right-sided APs may have atrial insertion far from the TA. These uncommon variation of APs can be reliably identified and ablated using CARTO system.

Scar-Related Atrial Tachycardia Associated with Radiation Therapy

A 59-year-old male was admitted for catheter ablation of paroxysmal supraventricular tachycardia. He had a previous history of lower-thoracic esophageal cancer treated by chemoradiation therapy 2 years earlier. The patient had received a total dose of 61 Gy and the heart had been included in the radiation therapy (RT) field. The 12-lead ECG during sinus rhythm was within normal range (Picture 1A). The 12-lead ECG during tachycardia showed long RP tachycardia (Picture 1B). The endocardial voltage map of the right atrium (RA) by electroanatomical mapping revealed a broad low voltage area including scar tissue which was suggested by non-captured, high output pacing, mainly in the free wall of the RA (Picture 2A). The activation map during the tachycardia demonstrated a focal activation pattern with the earliest activation site in the low lateral RA (Picture 2B) where the mid-diastolic potentials during the tachycardia were recorded (Picture 3), suggesting scarrelated reentry as the mechanism of the tachycardia and suc-

Incremental Pacing for the Diagnosis of Complete Cavotricuspid Isthmus Block During Radiofrequency Ablation of Atrial Flutter

Complete conduction block of the cavotricuspid isthmus (CTI) reduces atrial flutter recurrences after ablation. Incremental rapid pacing may distinguish slow conduction from complete CTI conduction block. Fifty-two patients (67 +/- 9 years) undergoing 55 CTI ablation procedures were included. With ablation, double potentials (DPs) separated by an isoelectric line of > or =30 ms were obtained. Incremental atrial pacing (600-250 ms) was performed from coronary sinus (CS) and low lateral right atrium (LLRA). A <20 ms increase in the DPs distance during incremental pacing was indexed as complete CTI block. In 8 patients, an initial <20 ms DPs distance increase was noted; direct complete isthmus block was suggested and no additional ablation performed. In the remaining, the CTI line was remapped for conduction gaps and additional radiofrequency energy pulses applied. Complete block, as indexed by incremental pacing, occurred in 46 of 55 procedures, with one flutter recurrence (follow-up 8 +/- 2 months): DPs interval variation of 116 +/- 20 to 123 +/- 20 ms (CS), P = 0.21; and 122 +/- 25 to 135 +/- 35 ms (LLRA), P = 0.17. The remaining 9 patients (persistent rate-dependent DPs increase) presented 3 flutter recurrences, P = 0.01: DP distance from 127 +/- 15 to 161 +/- 18 ms (CS), P < 0.001; and 114 +/- 24 to 142 +/- 10 ms (LLRA), P = 0.007. Incremental pacing distinguishes complete CTI block from persistent conduction. Such identification, accompanied by additional ablation to achieve block, should minimize flutter recurrences after ablative therapy.

Fractionated atrial electrograms during sinus rhythm: Relationship to age, voltage, and conduction velocity

Fractionated atrial electrograms (CFAEs) have been implicated in the mechanism of atrial fibrillation (AF). The prevalence and distribution of CFAEs in normal populations have not been clearly defined. This study sought to determine the influence of age on CFAEs and investigate the relationship between CFAEs and the underlying atrial substrate. Twenty-one patients without structural heart disease underwent electroanatomic mapping of their right atrium (RA). Patients were categorized into 3 groups according to age: group A, patients <30 years (25.1 +/- 3.1 years, n = 7); group B, patients between 31 and 59 years (51.7 +/- 10.3 years, n = 6); group C, patients >60 years (66.9 +/- 7.7 years, n = 8). The proportion of points with CFAEs was analyzed for the high and low septal RA, high and low lateral RA, and high and low posterior RA. The mean atrial voltage and conduction velocity were assessed in each of these regions. The percentage of CFAEs was greater in group C (14.6% +/- 7.7%) than in group A (2.7% +/- 2.1%; P = 0.001). The percentage of CFAEs in group B (8.5% +/- 3.5%) was not significantly different from that in group A (P = 0.21) and group C (P = 0.14). The CFAEs were predominantly located in the posterior RA and high septal RA. There were significant correlations between the proportion of CFAEs and age (R = 0.72; P < 0.01), atrial voltage (R = -0.57; P < 0.01), and conduction velocity (R = -0.73; P < 0.001). CFAEs increase with age and occur in regions of low atrial voltage and slowed conduction. The distribution of CFAE is predominantly along the posterior and high septal RA, regions where there are marked changes in myocardial fiber orientation. This suggests that the underlying myocardial architecture is the main influence on electrogram morphology.

Intraoperative mapping of the right atrial free wall during sinus rhythm: variety of activation patterns and incidence of postoperative atrial fibrillation

The atrial conduction properties associated with cardiac disease are speculated as the background of postoperative atrial fibrillation (POAF). We examined the atrial conduction patterns and conduction properties during sinus rhythm (SR) in patients that had undergone cardiac operations and evaluated the incidence of POAF in all patients. Fifty-two patients with stable SR who underwent cardiac surgery, with a diagnosis of valvular disease in 25, ischemic heart disease in 24, and others in 3, were enrolled in this study. The epicardial recordings were made using a mapping system with 60 unipolar electrodes placed on the right atrium (RA) intraoperatively. The activation patterns of the RA were assessed, and the longitudinal, transverse and oblique conduction velocity and max anisotropic ratio were also examined. Sinus activation was initiated from various sites (single origin at the high-lateral RA in 40, mid-lateral RA in 4, low-lateral RA in 2, and multiple origins in 6 patients) and it demonstrated anisotropic conduction (1.8+/-0.6) with the longitudinal conduction being more rapid than transverse and oblique conduction. Fifteen patients demonstrated non-uniform activation patterns such as, a localized conduction delay in seven, functional conduction block in two and mosaic-activation pattern associated with multiple origins in six. A total of 21 patients (44%) developed POAF. A conduction delay and mosaic activation pattern was found significantly more often in patients with POAF than in patients who remained in sinus rhythm. Multivariate analysis revealed that non-uniform activation pattern (odds ratio=8.71; 95% confidence interval [CI]=1.74-43.67; p=0.008) and TR (odds ratio=4.95; 95% CI=1.14-21.37; p=0.032) were independently associated with the development of POAF. Although all patients had converted to SR at the time of discharge, the administration of antiarrhythmic drugs caused sinus bradycardia in two patients who demonstrated a mosaic activation pattern in RA. Cardiac surgery patients exhibited a variety of sinus activation patterns, which also provided an arrhythmogenic substrate for POAF. A better understanding of the sinus activation using an intraoperative mapping system may provide benefit in the clinical management of POAF.

Differential Pacing for Distinguishing Slow Conduction from Complete Conduction Block of the Tricuspid-Inferior Vena Cava Isthmus after Radiofrequency Ablation for Atrial Flutter—Role of Transverse Conduction through the Crista Terminalis

Partial conduction block has been suggested a predictor of recurrence of atrial flutter (AFL). The aim of this study was to assess transverse conduction by the crista terminalis (CT) as a problem in evaluating isthmus block and the usefulness of differential pacing for distinguishing slow conduction (SC) and complete conduction block (CB) across the ablation line. We assessed 14 patients who underwent radiofrequency catheter ablation of the eustachian valve/ridge-tricuspid valve isthmus for typical AFL. Activation patterns along the tricuspid annulus (TA) suggested incomplete CB across the isthmus. In these patients, atrial pacing was performed from the low posteroseptal (PS) and anteroseptal (AS) right atrium (RA) while the ablation catheter was placed at the ablation line where double potentials (DPs) could be recorded. The pattern of activation of the RA free wall was assessed by a 20-pole catheter positioned along the CT during pacing from the coronary sinus (CS) ostium (CSos) and low lateral RA (LLRA). Faster transverse conduction across the CT resulted in simultaneous or earlier activation of the distal halo electrodes than of the more proximal electrodes, suggesting incomplete conduction block across the isthmus. CB (13) and SC (1) were detected as changes in the activation times of the first and second components of DPs (DP1, DP2) during PS RA pacing and AS RA. Similar changes in the activation times DP1 and DP2 during AS RA pacing as compared to PS RA reflected SC through the isthmus, whereas increased DP1 activation time and decreased of DP2 activation time reflected complete conduction block across the isthmus. Transverse conduction across the CT influences the sequence of activation along the TA after isthmus ablation. Differential pacing can distinguish SC from complete conduction block across the ablation line in the isthmus.

Role of bipolar electrogram polarity mapping in localizing recurrent conduction in the isthmus early and late after ablation of atrial flutter.

Bipolar electrogram polarity was analyzed to localize the recurrent conduction site in the isthmus between the tricuspid annulus (TA) and inferior vena cava (IVC) in recurrent atrial flutter (AF). Despite the initial successful linear isthmus ablation, recurrence of transisthmus conduction and AF is not uncommon. It is unclear how the recurrent conduction site can be identified. Fourteen patients with recurrent AF were studied: four with late recurrence remote from the first ablation and 10 with early recurrence within 60 minutes after the initial successful ablation. Bipolar electrogram polarity mapping was performed during low lateral right atrium (LLRA) pacing during sinus rhythm while recording bipolar electrograms from the septal portion of the isthmus along the previously ablated line. The septal side of the isthmus from TA to IVC was arbitrarily divided into five sites, and the bipolar electrodes with cathode at the tip and anode at the second was placed at each site. The recurrent conduction site was localized by analyzing the polarity of the bipolar electrogram recorded at each site. All recurrent AF was due to reentry around TA. During pacing from LLRA, as the mapping electrode was moved from TA to IVC side, the major polarity of the electrogram changed from negative to positive in all patients. A transitional electrogram with the equal amplitudes in positive and negative components was recorded between the sites showing mainly negative and positive electrograms, indicating electrogram polarity reversal at this site. Application of radiofrequency energy to this single site resulted in the elimination of transisthmus conduction in all patients with a single application in 11 patients and 2 or 3 in the remaining 3. Bipolar electrogram polarity mapping with attention to the polarity reversal point is useful for identifying and ablating the recurrent conduction site.

Electrophysiological determinant for induction of isthmus dependent counterclockwise and clockwise atrial flutter in humans

ObjectiveTo investigate the electrophysiological determinant underlying the electrical induction of counterclockwise and clockwise isthmus dependent atrial flutter.Patients and methodsThe isthmus bordered by the inferior vena caval orifice–tricuspid annulus–coronary sinus ostium...

Nonpharmacologic treatment of common atrial flutter guided by transient entrainment.

We attempted nonpharmacologic treatment for common atrial flutter in 7 patients, with direct current catheter ablation (CA) in 5 cases and cryoablation in 2 cases under the guidance of transient entrainment. Transient entrainment during common atrial flutter by pacing from the mid or low lateral right atrium (LLRA) revealed a long conduction time between the LLRA and the orifice of the coronary sinus (CSo) (73% to 121% of flutter cycle length). In 2 cases, fragmented electrograms were recorded at the low right atrial septum with durations of 150 msec and 155 msec, respectively. Because these fragmented electrograms were transiently entrained by rapid atrial pacing in the same manner as other atrial electrograms and were recorded in an area of long conduction, we believe that fragmented electrograms represent critical slow conduction. In 5 cases, CA was directed at this area. Three cases were successfully treated with 3 to 4 DC shocks of 100 J (follow up periods of 11.3, 4.5 and 3 months). Two cases which received 1 to 2 DC shocks of 100 J had recurrence of atrial flutter 6 and 4.7 months later, respectively. Two cases which showed atrial septal defect received surgical treatment. They were successfully treated with extended cryoablation in this same area (follow up periods of 26 and 9.2 months). In conclusion, extended ablation of an area of fragmented electrograms using transient entrainment may be an effective treatment for common atrial flutter.