Clockwise Atrial Flutter Research Articles

Comparison of clockwise and counterclockwise right atrial flutter using high-resolution mapping

Abstract Background To the best of our knowledge, few studies have been performed that explore the electrophysiological differences between clockwise (CW) and counterclockwise (CCW) right atrial (RA) cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) using the high-resolution Rhythmia mapping system. Objectives. Accordingly, our prospective cohort study, sought to compare CW and CCW CTI-dependent AFL in preselected pure right AFL patients (pts) using the ultra-high-definition (ultra-HD) Rhythmia mapping system. The study also aimed to mathematically develop a cartography model based on automatic velocity RA measurements to identify electrophysiological AFL specificities. Methods and results Between October 2019 and July 2020, 33 patients were recruited. The mean age was 71±13 years old. No difference was found concerning clinical variables between CCW AFL and CW AFL or regarding left ventricular ejection fraction (LVEF) (55.5±10 vs. 56.6±12; p=0.76). The AFL cycle length was very similar (248±20 vs. 252±28 ms; p=0.6). The sinus venosus (SV) block line was present in 32/33 of cases (97%) and no significant difference was found between CCW and CW CTI AFL (100% vs. 91%; p=0.7). No line was localized in the region of the crista terminalis (CT). A superior gap was present in the posterior line in 14/31 (45.2%) but this was similarly present in CCW AFL, when compared to CW AFL (10/22 [45.5%] vs. (4/10 [40%]); p=0.9). When present, the extension of the posterior line of block was observed in 18/31 pts (58%) without significant differences between CCW and CW CI AFL (12/22 [54.5%] vs. (6/10 [60%]) (p=.9) The Eustachian ridge line of block was similarly present in both groups (82% [18/22] vs. 45.5% [5/11]; p=0.2). The absence of the Eustachian ridge line of block led to significantly slowed velocity in this area (28±10cm/s; n=8),and the velocities were similarly altered between both groups (26±10 [4/22] vs. 29.8±11cm/s [4/11]; p=0.6). We created mathematical, three-dimensional RA reconstruction-velocity model measurements. In each block localization, when the block line was absent, velocity was significantly slowed (≤20cm/s). A systematic slowdown in conduction velocity was observed at the entrance and exit of the CTI in 100% of cases. This alteration to the conduction entrance was localized at the lateral side of the CTI for the CCW AFL and at the septal side of the CTI for CW AFL. The exit-conduction alteration was localized at the CTI septal side for the CCW AFL and at the CTI lateral side for the CW AFL. The only differences between CW and CCW AFL concerned activation patterns. Conclusions The ultra-HD Rhythmia mapping system confirmed the absence of significant electrophysiological differences between CCW and CW AFL. The mechanistic posterior SV and Eustachian ridge block lines were confirmed in each arrhythmia. A systematic slowing down at the entrance and exit of the CTI was demonstrated in both CCW and CW AFL, but in reverse positions. Funding Acknowledgement Type of funding sources: None.

Comparison of clockwise and counterclockwise right atrial flutter using high-resolution mapping and automated velocity measurements.

Only few studies have been performed that explore the electrophysiological differences between clockwise (CW) and counterclockwise (CCW) right atrial (RA) cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) using the high-resolution Rhythmia mapping system. We sought to compare CW and CCW CTI-dependent AFL in pure right AFL patients (pts) using the ultra-high-definition (ultra-HD) Rhythmia mapping system and we mathematically developed a cartography model based on automatic velocity RA measurements to identify electrophysiological AFL specificities. Thirty-three pts were recruited. The mean age was 71 ± 13 years old. The sinus venosus (SV) block line was present in 32/33 of cases (97%) and no significant difference was found between CCW and CW CTI AFL (100% vs. 91%; p = .7). No line was localized in the region of the crista terminalis (CT). A superior gap was present in the posterior line in 14/31 (45.2%) but this was similarly present in CCW AFL, when compared to CW AFL (10/22 [45.5%] vs. 4/10 [40%]; p = .9). When present, the extension of the posterior line of block was observed in 18/31 pts (58%) without significant differences between CCW and CW CI AFL (12/22 [54.5%] vs. 6/10 [60%]; p = .9) The Eustachian ridge line of block was similarly present in both groups (82% [18/22] vs. 45.5% [5/11]; p = .2). The absence of the Eustachian ridge line of block led to significantly slowed velocity in this area (28 ± 10 cm/s; n = 8), and the velocities were similarly altered between both groups (26 ± 10 [4/22] vs. 29.8 ± 11 cm/s [4/11]; p = .6). We created mathematical, three-dimensional RA reconstruction-velocity model measurements. In each block localization, when the block line was absent, velocity was significantly slowed (≤20 cm/s). A systematic slowdown in conduction velocity was observed at the entrance and exit of the CTI in 100% of cases. This alteration to the conduction entrance was localized at the lateral side of the CTI for the CCW AFL and at the septal side of the CTI for CW AFL. The exit-conduction alteration was localized at the CTI septal side for the CCW AFL and at the CTI lateral side for the CW AFL. The ultra-HD Rhythmia mapping system confirmed the absence of significant electrophysiological differences between CCW and CW AFL. The mechanistic posterior SV and Eustachian ridge block lines were confirmed in each arrhythmia. A systematic slowing down at the entrance and exit of the CTI was demonstrated in both CCW and CW AFL, but in reverse positions.

P1013Biannular atrial flutter: clinical and electrophysiological characterization by activation and entrainment

Abstract Introduction re-entry mechanisms around mitral and tricuspid annuli are frequent causes of left and right atrial flutter (AFt) respectively in patients with ipsilateral atrial pathology. However, clinical and electrophysiological characteristics of other types of atrial re-entries that could involve both AV annuli are less known. Purpose characterize biannular atrial flutters. Methods 4 patients with AFt were submitted for ablation (aged 30, 31, 58 and 61 yo; 2 females). All had a cardiac congenital disease with a prior surgical procedure: 3 atrial septal defects (ASD) with surgical repair and 1 with transposition of the great arteries (TGA) with Senning repair. The AFt had a cycle length (CL) of 290, 315, 330 y 340 ms respectively and 1:1 AV conduction in 3 of them. For the electrophysiological study, a multipolar catheter (20 or 24 poles) was placed in the right atrium (RA) in every patient, showing counterclockwise and clockwise activation in 1 and 3 patients, respectively. Coronary sinus (CS) activation was proximal to distal in one patient and distal to proximal in the other 2. No CS activation could be obtained in the patient with Senning repair. Results each AFt was mapped by entrainment from different sites of the RA, showing post-pacing intervals (PPI) similar to the CL of the AFt around the tricuspid annulus in all of them and also from proximal and distal CS in the 3 patients with ASD. Access to the native left atrium (LA) was achieved in the patient with Senning repair, showing PPIs around the mitral annulus that were similar to the LC of the tachycardia. In 2 patients the attempt to get to the LA through the interatrial septum (IAS) could not be achieved and was unattempted in the other one. Recordings and PPIs of the LA roof were obtained from the right branch of the pulmonary artery in 2 patients. Counterclockwise AFt and clockwise AFt by single biannular perimitrotricuspid rotation in 1 and 3 patients respectively. The AFt was ended and no reinduction was possible after radiofrequency application that achieved cavotricuspid isthmus block in all of the patients. Conclusions reentry around both AV annuli is possible as a single loop, counterclockwise or clockwise, of simultaneous rotation as a clinical mechanism of Aft. This type of AFt seems to be associated to absence or severe damage in the IAS.

PP-279 ABLATION OF THE TYPICAL CAVOTRICUSPID ISTHMUS-DEPENDENT ATRIAL FLUTTER AND ATRIOVENTRICULAR NODAL REENTRY TACHYCARDIA IN A PATIENT WITH OPERATED TETRALOGY OF FALLOT

Introduction: Cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) is the most common arrhythmia in operated Tetralogy of Fallot (ToF) patients. Here, we report the successful ablation of a typical counterclockwise AFL and reverse clockwise AFL in a patient with operated ToF. Case report: A 35-year-old male had previously undergone total corrective surgery for ToF 27 years before admitted to our clinic. He suffered from tachyarrhythmias for 3 months, and his symptoms had worsened in the last 1 month with the manifestation of paroxysmal typical AFL. Baseline ECG revealed first degree AV block and right ventricular hypertrophy signs. Upon examination of the 12-lead ECG recorded during palpitation, we observed no visible P waves and inferior axis and thus considered the possibility of AVNRT. Transthoracic and transesophageal echocardiography revealed an incomplete closure of the tricuspid valve with severe tricuspid regurgitation and a dilated right atrium in the apical 4-chamber view. Electrophysiological investigation revealed both clockwise and anticlockwise AFL (Figures 1a,b).

The V‐A‐V Response to Ventricular Entrainment During Atrial Tachycardia: What Is the Mechanism?

A 46-year-old male was admitted to our emergency department due to a narrow QRS tachycardia of 230 bpm with impeding hemodynamic collapse. His only remarkable medical history was mild hypertension. Adenosine administration was ineffective in stopping the tachycardia, and sinus rhythm was restored using an electrical cardioversion. A few weeks later, during an electrophysiology study an identical tachycardia was immediately induced during the introduction of diagnostic catheters into the right atrium (Fig. 1, upper panel). A rate-related right bundle branch block aberration was present for most of the time. Atrial activation was simultaneous with ventricular activation, ruling out atrioventricular reentrant tachycardia (AVRT), and suggesting atrioventricular nodal reentrant tachycardia (AVNRT) (Fig. 1, lower panel). To confirm the absence of atrial tachycardia, ventricular entrainment pacing using a cycle length shorter by 30 milliseconds than the tachycardia cycle length was performed. The atrial rate accelerated to the pacing rate (Fig. 2), and when ventricular (V) pacing was ceased, the activation sequence was the last entrained atrium (A) followed by the ventricle (V) (i.e., a V-A-V response). Such a response is considered to rule out atrial tachycardia and these findings were repeatable. Therefore, by exclusion of all other possible causes a diagnosis of AVNRT could have been considered irrefutable. However, long VA interval during entrainment and the atrial activation sequence with atrial depolarization later on His catheter than on high right atrial catheter (Fig. 1, lower panel) were not compatible with slow-fast AVNRT, either. Moreover, multiple attempts to stop the tachycardia with fast ventricular and atrial burst pacing failed. This prompted a more detailed assessment of the atrial activation sequence and an analysis of entrainment from the right atrium. Those analyses both led to an unquestionable diagnosis of a macroreentrant right atrial tachycardia with a reentrant circuit identical to that observed in a typical clockwise atrial flutter, albeit slower, which resulted in a rate below the arbitrary thresh-

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.

Characteristics of recurrent clockwise atrial flutter after previous radiofrequency catheter ablation for counterclockwise isthmus-dependent atrial flutter

Isthmus-dependent (ID) clockwise (CW) atrial flutters (AFl) are rare in comparison with counterclockwise (CCW) AFl. Little is known about clinical and electrophysiological characteristics of CW AFl occurring after previous radiofrequency (RF) catheter ablation of CCW AFl. We sought to compare CW AFl de novo vs. CW AFl occurring after previous CCW AFl RF ablation. A total of 246 procedures of RF catheter ablation for AFl from January 2009 to January 2011 were reviewed. Clinical and electrophysiological data were analysed. Patients were excluded if they were in sinus rhythm at the beginning of the procedure, if they had concomitant/previous atrial fibrillation ablation, or if AFl was not ID. Twenty-seven patients presented CW AFl (10.9% of all ID AFl), including 10 CW AFl occurring after a previous RF catheter ablation for CCW AFl. Mean time for recurrence after the previous procedure of CCW AFl RF ablation was 3.5 years. They were younger (61.6 ± 11 years) than patients with CW AFl de novo (74.0 ± 7.2 years; P = 0.005). Bidirectional isthmus block was obtained in all patients. There was a significant difference in terms of double potential separation after ablation (155 ± 31 ms for CW AFl de novo vs. 111 ± 7 ms for recurrent CW AFl; P = 0.028). No differences were observed concerning CHADS score, AFl cycle length, and electrocardiogram typical pattern for CW AFl between the two groups. Patients with CW AFl occurrence after CCW AFl RF catheter ablation are younger than patients with CW AFl de novo. They also have a smaller interspike interval after block completion.

Electrophysiologic study on the mechanism of initiation of clockwise atrial flutter by rapid atrial pacing：role of dual pathway physiology within the right atrial isthmus

Electrophysiologic study on the mechanism of initiation of clockwise atrial flutter by rapid atrial pacing：role of dual pathway physiology within the right atrial isthmus

217 Characteristics of recurrent clockwise atrial flutter after previous radiofrequency catheter ablation for counterclockwise isthmus-dependent atrial flutter

217 Characteristics of recurrent clockwise atrial flutter after previous radiofrequency catheter ablation for counterclockwise isthmus-dependent atrial flutter

Novel method to evaluate the conduction velocity and conducting area during isthmus-dependent atrial flutter

The difference of the conduction velocity (CV) around the tricuspid valve annulus between the counter-clockwise (CCW) atrial flutter and the clockwise (CW) atrial flutter has not been well clarified. This study was undertaken to evaluate the CV and the conducting area (CA) per millisecond around the tricuspid valve annulus using the electroanatomical mapping. The electroanatomical mapping was performed during the tachycardia for 30 consecutive patients (mean age: 61±16 years) with isthmus-dependent atrial flutter (CCW, 25; CW, 5). We measured the CV and the CA of five divided areas of the right atrium, that is, upper septum (US), lower septum (LS), isthmus (I), upper lateral wall (UL) and lower lateral wall (LL) using the novel measurement method in the isochronal map. Statistical differences of these data between the two groups were assessed by the Student's t-test and one-way analysis of variance methods. In total, the CV of the LS was significantly slower than other areas (m/sec: US, 0.57±0.18; LS, 0.43±0.18; UL, 0.60±0.26; LL, 0.53±0.20; I, 0.50±0.17; p<0.05) and the CA of the US and UL were significantly larger than other areas (mm2/sec: US, 34.5±16.2; LS, 16.2±9.5; UL, 40.0±14.1; LL, 27.0±17.0; I, 16.8±8.5; p<0.0001). There was no significant difference between the CCW and the CW atrial flutters in terms of the CV and the CA of equally divided five areas. In both of the CCW and the CW atrial flutters, the CV of the LS was significantly slower than other areas and the CA of the lower atrium was significantly smaller than the upper atrium.

Cavotricuspid Isthmus Ablation Guided by Electroanatomic Mapping in a Patient with a Mechanical Tricuspid Valve Replacement After a Total Correction of Tetralogy of Fallot

Atrial arrhythmias are a common sequel after surgery for congenital heart disease, and often eventually cause late morbidity and mortality. Nowadays, percutaneous catheter ablation of atrial flutter (AFL) is widely practised, and is highly successful and safe. Patients with a tricuspid valve replacement (TVR) represent a distinct group for whom the appropriate nonpharmacologic therapy for AFL has not yet been established. We report a case of a 55-year-old woman with a history of a total correction of tetralogy of Fallot (ToF) who developed AFL before and after receiving a tricuspid valve prosthesis. Based on the results of the activation mapping, counterclockwise and clockwise AFL were identified. Completion of a cavotricuspid isthmus (CTI) line on the atrial side successfully terminated the AFL, with resumption of sinus rhythm. Guided by a 3D mapping system, CTI ablation is feasible and safe in patients with a prosthetic tricuspid valve.

Right Atrial Thrombus Aspiration Guided by Intracardiac Echocardiography During Catheter Ablation for Atrial Fibrillation

A 56-year-old man with psoriasis and a 2-year history of paroxysmal atrial fibrillation and flutter was admitted for catheter ablation. The procedure was performed under general anesthesia. The patient arrived to the electrophysiology laboratory in atrial flutter. A preprocedural transesophageal echocardiogram confirmed the absence of intraatrial thrombus. The patient was chronically anticoagulated with warfarin, and the international normalized ratio (INR) on the day of the procedure was 2.4. After vascular access was obtained, a duodecapolar catheter was placed from the left femoral vein with the 10 distal electrodes in the coronary sinus and 10 proximal electrodes in the right atrium (RA). A phased-array intracardiac echo (ICE) catheter was placed via the left femoral vein into the RA. Intravenous heparin, 5000 U, was given after initial catheter placement. The presence of typical clockwise atrial flutter was confirmed by activation and entrainment mapping. A cavo-tricuspid isthmus ablation line …

Mechanisms of atypical flutter wave morphology in patients with isthmus-dependent atrial flutter

Sixty-three episodes of isthmus-dependent atrial flutter (AFL) in 55 patients were studied to characterize variations in flutter wave morphology and to investigate the mechanisms of the atypical flutter waves on surface ECG. The activation patterns of coronary sinus (CS) and their relationship with flutter wave morphology on the ECG were analyzed. In 46 episodes of counterclockwise AFL (CCW-AFL), there were four types of flutter waves on ECG. Typical and atypical flutter waves were found in 47.8% and 13.0% of the episodes, respectively. Atypical flutter waves had broad positive terminal portion or entirely positive wave in the inferior leads and in V(1), with a distal-to-proximal or fused activation pattern in the CS, and an average activation time of 21.3 +/- 11.4 ms. In 17 episodes of clockwise AFL (CW-AFL), typical and atypical flutter waves were identified in 41.2% and 41.2%, respectively. Atypical flutter waves had negative waves in the inferior ECG leads and in V1, a proximal-to-distal activation pattern in the CS, and an average activation time of 42.4 +/- 14.4 ms. We conclude that atypical flutter waves are common in the isthmus-dependent AFL. The clockwise or counterclockwise conduction in the right atrium, and the activation patterns or conduction sequences between the right and the left atrium, are associated with the variations in the flutter wave morphology on body surface ECG.

Ventricular location of a part of the right atrial isthmus after tricuspid valve replacement for Ebstein’s anomaly: a challenge for atrial flutter ablation

We report the case of a patient with atrial flutter late after tricuspid valve replacement for Ebstein's anomaly. Computed tomographic angiography revealed that coronary sinus ostium and part of the right atrial isthmus were located on the ventricular side of the valve ring due to the specific surgical approach in this condition. Based on the results of electroanatomic mapping and entrainment, the arrhythmia was found to be cavotricuspid isthmus dependent clockwise atrial flutter. Completion of the isthmus line required ablation lesions across the artificial valve. When these were delivered the arrhythmia terminated and isthmus block was achieved. Due to arrhythmia recurrence a redo procedure was performed which demonstrated conduction recovery in the ventricular part of the cavotricuspid isthmus. Intracardiac ultrasound-guided ablation successfully eliminated conduction across the isthmus with subsequent freedom from arrhythmia on follow up.

Abstract 2644: High Prevalence of a Novel Conduction Pattern Around the Coronary Sinus in Cavotricuspid Isthmus Dependent Right Atrial Flutter

Objective : We tested our hypothesis that, in atrial flutter (AFL) dependent on the cavotricuspid isthmus (CTI), lower loop reentry (LLR) is the common pathway route at the coronary sinus (CS) posterior site, and thus, dual loop reentry (DLR) is a common circular pattern. Methods and result s: We studied 25 patients with CTI-dependent AFL, 16 with chronic counterclockwise atrial flutter (CCW-AFL) and 9 with clockwise atrial flutter (CW-AFL) and determined the precise reentry circuitry, especially for conduction patterns around the CS orifice, using electroanatomical mapping. We measured post pacing interval and tachycardia cycle length during entrainment from sites within the flutter circuit. In 16 of the 25 CCW-AFL patients, the CS anterior pacing site was within the AFL circuit in 13. The CS anterior pacing site was within the AFL circuit in 6 of the 9 CW-AFL patients. In 8 each of 16 CCW-AFL and 9 CW-AFL patients, both the CS anterior and posterior sites were within the AFL circuit. Results of 3-Dimensional (3D) activation mapping suggest that all of these patients had a DLR circuit, and that CS posterior conduction broke through the eustachian valve/ridge. Conclusion : CS posterior conduction consisted of the flutter circuit and appeared to be critical for maintaining AFL. Almost all AFL patients had DLR formed within the LLR or the superior RA circuit constituted from CS posterior conduction and in the anterior loop around the tricuspid annulus.

P3-57: Comparison of the conduction velocity and conducting area between the counter clockwise and clockwise atrial flutters using electroanatomical mapping system

There is still controversy about the difference of the conduction velocity (CV) around the tricuspid valve annulus (TVA) between the counter clockwise (CCW) atrial flutter (AFl) and the clockwise (CW). Therefore, this study was undertaken to evaluate the CV around the TVA and conducting area per milli-second (CA) of right atrium (RA) using the electroanatomical mapping system (CARTO).

P6-41: Patterns of interatrial conduction and P wave polarities were different between atrial tachyarrhythmias from superior vena cava and clockwise atrial flutter?

P6-41: Patterns of interatrial conduction and P wave polarities were different between atrial tachyarrhythmias from superior vena cava and clockwise atrial flutter?

Counterclockwise atrial flutter in dextrocardia

A 57-year-old woman with history of flutter had a surface ECG suggestive of clockwise (CW) atrial flutter with positive F waves in leads II, III, and aVF and negative F wave in lead V1 (Figure 1). The complete absence of an R wave in lead I was noted. Chest x-ray film demonstrated dextrocardia. Echocardiography established complete situs inversus with otherwise normal intracardiac anatomy.

Atrial arrhythmias prevalence in heart transplant patients

The orthotopic heart transplantation (HTx), by the standard technique involves anastomosis of donor(DA) to recipient atria(RA): the composite atrium comprises two electrically distinct parts which show, generally, 2 distinct independent rhythms. Little is known about atrial arrhythmias prevalence and features in HTx patients (pts). Between January 1985 and November 2004 in Div. of Cardiac Surgery 740 pts underwent HTx by standard technique (mean age 48.1 ± 12 yrs, mean F.U. 80 mos).16/740 pts (2.2%) with incessant atrial arrhythmias underwent EPS and RF ablation. In 10/16 (62.5%) pts atrial arrhythmia originated from RA and was conducted to DA across the surgical scar: in 6, the RA arrhythmia was sustained atrial tachycardia, in 1 pt was atrial fibrillation (AF) and in 3 was pseudo premature atrial contractions (PAC)due to conduction of recipient sinus rhythm to DA. In all pts, except one, the interatrial conduction (IAC) was localized along the suture line in the right atrium, in the postero-lateral or lateral wall. In 3/16 (19%) pts the arrhythmia was a clockwise atrial flutter (AFl) with the critical isthmus between the interatrial suture line and the tricuspid valve (TV). Two/16 (12.5%) pts had focal arrhythmias; one pt had frequent PACs from the superior portion of the DA, close to the suture line; one pt had a focal tachycardia from the DA postero-lateral wall, close to the scar. One pt had an atrioventricular nodal reentry tachycardia (AVNRT) from the DA.The prevalence of sustained atrial arrhythmias in this population was 2.2%, with a prevalence of arrhythmias due to the IAC of 1.3%, AFl of 0.4%, AVNRT of 0.1% and focal atrial tachycardia of 0.4%. The sole case of AF was due to IAC. In this pts the prevalence of AF is significantly lower (1%), whereas the prevalence of AFl is significantly higher (0.09%) compared to the general population. In orthotopic HTx pts, IAC was responsible of most of atrial arrhythmias. The low prevalence of AF episodes might be explained by the electrical isolation of pulmonary and cava veins from the DA; the higher prevalence of AFl is likely due to interatrial suture line which favours macroreentry arrhythmias with critical isthmus between the interatrial suture line and the TV.

Relationship Between Anatomic Location of the Crista Terminalis and Double Potentials Recorded During Atrial Flutter:

The activation sequence in typical atrial flutter (AFL) around the tricuspid annulus is well described. However, activation of the remainder of the right atrium (RA) is not well defined. Previous studies have shown a linear block at the crista terminalis (CT) during AFL. The aim of this study was to evaluate the relationship between the location of the CT and the line of block by intracardiac echocardiography (ICE). Twenty-one patients with typical AFL were included in the study. The ICE imaging catheter (9-French with 9-MHz ultrasound transducer) was advanced to the RA. Under ICE guidance, a 20-pole roving catheter was used to map double potentials (DPs) during AFL, and three-dimensional images of the RA were reconstructed. During counterclockwise (CCW), clockwise (CW) AFL, or both, a line of conduction block manifested by DPs was identified at a septal site adjacent to the CT in 12 patients and in the posteroseptal RA in 9 patients. The functional line of block in CCW and CW AFL is localized not at the CT but at the septal edge of the CT or in the posteroseptal RA.