MAPping with fragmentation analysis in patients with atypical atrial FLUtter using the RHYthmia navigation system (MAP-FLURHY study)

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
E Franco ◽  
C Lozano Granero ◽  
R Matia ◽  
A Hernandez-Madrid ◽  
I Sanchez-Perez ◽  
...  
Keyword(s):  
Sinus Rhythm ◽  
Atrial Flutter ◽  
Cycle Length ◽  
Funding Source ◽  
Atrial Arrhythmias ◽  
Slow Conduction ◽  
Ablation Success ◽  
Focal Ablation ◽  
Procedural Success

Abstract Background Atypical atrial flutter (AAFL) circuits use areas of slow conduction which can be visualized as fragmented electrograms (fEGMs). Purpose To test an ablation strategy based on the identification and ablation of spots with fEGMs in AAFL. Methods The MAP-FLURHY study prospectively included all AAFL ablations with Rhythmia in our Center from June 2016 to June 2019. Patients with non-mappable AAFL, frequent conversion to atrial fibrillation, or cavotricuspid isthmus-dependent flutters were excluded from analysis. The IntellaMap ORION catheter was used to detect fragmentation areas, arbitrarily defined as fEGMs >70ms. Entrainment was used to check if these areas belonged to the AAFL circuit. Ablation targeted the longest fEGM within the circuit (return cycle <30ms): focal ablation for microreentries, and lines including the fEGMs for macroreentries. Ablation success was defined as conversion to sinus rhythm or another flutter. Procedural success was defined as successful ablation of all inducible flutters. Follow-up included visits with 24h Holter ECG at 3–6-12 months. Results 50 Patients received ablation (Figure). 27 Patients (70.6±13.1 years; 10 females; LVEF 57%±13%) with 44 mappable AAFLs were included in the analysis (Table). All AAFLs showed areas with fEGMs (106 areas; 2.4 areas per flutter). 42/44 AAFLs had fEGMs within the circuit, which were target of ablation. Ablation success: 34/36 AAFLs (94%); success could not be assessed in 6 circuits, due to mechanical conversion to sinus rhythm onto the target fEGM. Fragmented areas within the AAFL circuits (n=51) were longer (110±30 vs 90±15 ms, p<0.001) but had similar voltage (0.34±0.25 vs 0.36±0.26 mV) than areas outside the circuits (n=45). A fEGM duration >100ms/>40% of the cycle length predicted to be a successful site for ablation with 72.3%/73.8% specificity. Procedural success was achieved in 24/27 patients (89%). Excluding a 2-month blanking period, mean survival free from atrial arrhythmias was 19 (95% CI: 12.6–25.5) months. 57% of the patients were free from atrial arrhythmias at 1 year. Conclusions Most AAFLs had detectable fEGMs which could be target of ablation with high efficacy. Figure 1 Funding Acknowledgement Type of funding source: None

scholarly journals Stabilization of unstable reentrant atrial tachycardias via fractionated continuous electrical activity ablation (CHAOS study)

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
E Franco ◽  
C Lozano-Granero ◽  
R Matia ◽  
A Hernandez-Madrid ◽  
I Sanchez-Perez ◽  
...  
Keyword(s):  
Sinus Rhythm ◽  
Atrial Flutter ◽  
Atrial Arrhythmias ◽  
Density Mapping ◽  
Funding Sources ◽  
Ablation Success ◽  
Focal Ablation ◽  
Similar Figure ◽  
Procedural Success ◽  
One Year

Abstract Funding Acknowledgements Type of funding sources: None. Background. Unstable reentrant atrial tachycardias (ATs) (i.e. those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate.  Purpose. We have tested a strategy to convert unstable reentrant ATs into mappable stable ATs based on the detection and ablation of rotors. Methods. From May 2017 to December 2019, we included all consecutive patients scheduled for ablation of reentrant AT, excluding CTI-dependent atrial flutter, in which the tachycardia circuit was unstable. Operators subjectively identified rotors as sites with fractionated continuous (or quasi-continuous) electrical signals on 1-2 adjacent bipoles of conventional high-density mapping catheters, without dedicated software (Figure, A). Focal ablation of these sites was performed in order to stabilize the AT or convert it into sinus rhythm. In patients without rotors or failed rotor ablation, sites with spatiotemporal dispersion (i.e. all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted (Figure, B). Procedural success was defined as the successful ablation of all inducible ATs, without need of cardioversion, final sinus rhythm and non-inducibility. Follow-up included visits with ECG and 24h Holter-ECG at 3, 6 and 12 months. Results. From May 2017 to December 2019, 97 patients were scheduled for reentrant AT ablation, excluding CTI-dependent atrial flutter. Of these, 18 patients (18.6%; 72.1 ± 8.9 years of age, 9 females) presented unstable circuits and were included. 9 patients (50%) had structural cardiomyopathy, 11 patients (61%) prior atrial arrhythmias ablations, and 4 patients (22%) previous cardiac surgery. 13 patients (72%) had detectable rotors (26 rotors; median 2 [1–3] rotors per patient); focal ablation achieved conversion into stable AT or sinus rhythm in 12 (92%). In the other patient, and the 5 patients without detectable rotors, 17 sites with spatiotemporal dispersion were detected and focally ablated, with success to achieve arrhythmia stabilization in 5 patients (83%). Globally, and excluding one patient with spontaneous AT stabilization, ablation success to stabilize the AT was achieved in 16/17 patients (94.1%). Procedural success was achieved in 16/18 patients (88.9%). Rate of one-year freedom from atrial arrhythmias was 66.7%. In the 9 patients with stable ATs ablated during the same period, procedural success (92.4%) and one-year freedom from atrial arrhythmias (65.8%) were similar (Figure, C). Conclusion. Most unstable reentrant ATs show detectable rotors, identified as sites with single-bipole fractionated quasi-continuous signals, or spatiotemporal dispersion plus non-continuous fractionation. Ablation of these sites is highly effective to stabilize the AT or convert it into sinus rhythm. Abstract FIGURE

scholarly journals Stabilization of unstable reentrant atrial tachycardias via fractionated continuous electrical activity ablation (CHAOS study).

2021 ◽  
Author(s):  
Eduardo Franco ◽  
Cristina Lozano ◽  
Roberto Matía ◽  
Antonio Hernandez-Madrid ◽  
Inmaculada Sánchez ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Cycle Length ◽  
The Other ◽  
Atrial Arrhythmias ◽  
Density Mapping ◽  
Ablation Success ◽  
Focal Ablation ◽  
One Year ◽  
Mapping Catheter

Introduction. Unstable reentrant atrial tachycardias (ATs) (i.e. those with frequent circuit modification or conversion to atrial fibrillation) are challenging to ablate. We have tested a strategy to achieve arrhythmia stabilization into mappable stable ATs based on the detection and ablation of rotors. Methods and Results. From May 2017 to December 2019, 97 consecutive patients with reentrant ATs were ablated. Of these, 18 (18.6%) presented unstable circuits and were included. Mapping was performed using conventional high-density mapping catheters (IntellaMap ORION, PentaRay NAV or Advisor HD Grid). Rotors were subjectively identified as fractionated continuous (or quasi-continuous) electrograms on 1-2 adjacent bipoles of the mapping catheter, without dedicated software. 13 patients (72%) had detectable rotors (median 2 [1–3] rotors per patient); focal ablation achieved conversion into stable AT or sinus rhythm in 12 (92%). In the other 6 patients, sites with spatiotemporal dispersion (i.e. all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles were targeted. 17 sites with spatiotemporal dispersion were detected and focally ablated. Globally, and excluding 1 patient with spontaneous AT stabilization, ablation success to stabilize the AT was achieved in 16/17 patients (94.1%). One-year freedom from atrial arrhythmias was similar between patients with unstable and stable ATs (66.7% Vs 65.8%, p=0.946). Conclusion. Most unstable reentrant ATs show detectable rotors, identified as sites with single-bipole fractionated quasi-continuous signals, or spatiotemporal dispersion plus non-continuous fractionation. Ablation of these sites is highly effective to stabilize the AT or convert it into sinus rhythm.

scholarly journals Subjective identification and ablation of drivers in persistent atrial fibrillation

2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
E Franco ◽  
C Lozano-Granero ◽  
R Matia ◽  
A Hernandez-Madrid ◽  
I Sanchez-Perez ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Left Atrium ◽  
Atrial Flutter ◽  
Pulmonary Vein ◽  
Persistent Atrial Fibrillation ◽  
Atrial Arrhythmias ◽  
Ablation Success ◽  
Tailored Approach ◽  
Approach Group

Abstract Background Ablation of drivers in persistent atrial fibrillation (AF) has shown controversial results. Purpose To test the efficacy of a tailored approach for persistent AF ablation which includes pulmonary vein isolation (PVI) plus “subjective” identification and ablation of drivers. Methods From May 2017 to December 2019, selected patients with persistent AF and ongoing AF at the beginning of the ablation procedure were included. Conventional high-density mapping catheters (PentaRay NAV, IntellaMap Orion or Advisor HD Grid) were used. Drivers were subjectively identified as: a) fractionated continuous (or quasi-continuous) electrograms on 1–2 adjacent bipoles, without dedicated software (Figure 1A, dashed line; PR = PentaRay NAV); and b) sites with spatiotemporal dispersion (i.e. all the cycle length comprised within the mapping catheter) plus non-continuous fractionation on single bipoles (Figure 1B, arrows; in panels A and B: paper speed 200 mm/s; ORB = 24-pole ORBITER Woven catheter, blue bipoles around tricuspid annulus and green bipoles into the coronary sinus). Ablation included PVI + focal or linear ablation targeting sites with drivers. Ablation success was defined as conversion to sinus rhythm or atrial flutter during ablation. Follow-up included visits with 24h Holter ECG at 3–6–12 months. Survival free from atrial arrhythmias lasting >30 seconds was compared between patients ablated with this tailored approach, and all consecutive patients with persistent AF treated with a PVI-only strategy during the same period. Results 158 Patients received ablation: 35 with the tailored approach (61,7±10,2 years; 29% females) and 123 with only PVI (62,5±9,6 years; 25% females; 89% cryoablation). Basal characteristics were similar (Table 1). In the tailored-approach group, 14 patients (40%) presented 28 detectable sites with continuous fractionated electrograms, 26 on the left atrium and 2 on the right atrium, which was only mapped if ablation of drivers in the left atrium was not successful; 12 (43%) were located within the pulmonary vein antra. 27 patients (77%) showed 103 sites with spatiotemporal dispersion (4 [3–5] per patient). Ablation success was achieved in 17 patients (48%; conversion to sinus rhythm, n=7; conversion to atrial flutter, n=10) in the tailored-approach group and 1 patient (0,8%, sinus rhythm) in the PVI-only group. Excluding a 3-month blanking period, the tailored approach, compared to only PVI, improved one-year freedom from atrial arrhythmias (71% Vs 51%, p=0,05) and mean survival free from atrial arrhythmias (26±3 months; 95% CI 21–32 months Vs 18±2 months; 95% CI 15–22 months) (Figure 1C), at the cost of a longer median procedural time (246 [212–277] vs 108 [81–143] min, p<0,001) and fluoroscopy time (51 [36–76] vs 33 [21–45] min, p<0,001). Conclusion Subjective identification and ablation of drivers, added to PVI, improved freedom from atrial arrhythmias. FUNDunding Acknowledgement Type of funding sources: None. Table 1. Basal characteristics Figure 1

scholarly journals Fetal Atrial Flutter and Hydrops Successfully Treated with Transplacental and Direct Fetal Therapy

2016 ◽  
Vol 6 (1) ◽  
pp. 16-21
Author(s):  
Bettina F. Cuneo
Keyword(s):  
Sinus Rhythm ◽  
Atrial Flutter ◽  
Marked Change ◽  
Postnatal Life ◽  
Fetal Therapy ◽  
Fetal Ultrasound ◽  
Fetal Demise ◽  
Antiarrhythmic Medications ◽  
Antiarrhythmic Treatment

AbstractThe hydropic fetus with atrial flutter has high risk of fetal demise. In utero treatment is not as successful as SVT with 1:1 conduction. Even after conversion to sinus rhythm, close follow-up of the pregnancy is required for several reasons..Case Report:A 25 year old primigravida, at 26 wks of gestation had a fetal ultrasound which showed a tachycardic hydropic fetus with AFI 49. The rhythm was atrial flutter: AR 400 bpm and VR 200 bpm. The heart was structurally normal. Transplacental antiarrhythmic treatment with sotalol was started and 24 hours later, the fetus was still primarily in flutter with rare episodes of sinus rhythm and frequent PAC. Sotalol was increased but the mother’s QTc increased to > 500 ms, so the sotalol dose was reduced. On day 4th direct i.m. of digoxin was given and fetus was in sinus rhythm. Pharmacotherapy was continued. On the 16th day of sinus rhythm (at 33 wks), a marked change in FHR variability was seen. An US revealed the fetus was in sinus rhythm with a normal FHR. Because of the decreased FHR variability, the fetus was delivered by CS and the cord pH was 7.19, Apgars 1, 9 and 9. The neonate received no antiarrhythmic medications. On day 6 of postnatal life, an AV re-entrant tachycardia (AVRT) developed and sinus rhythm was successfully restored with sotalol and digoxin. The infant was treated for 18 months with no episodes of SVT or atrial flutter.

scholarly journals Concealed Pulmonary Vein Bigeminy during Sinus Rhythm in Patients with Paroxysmal Atrial Fibrillation: A Useful Marker for Pulmonary Vein Firing

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Jiqiang Hu ◽  
Wu Kuang ◽  
Xiaoyun Cui ◽  
Yan Li ◽  
Yang Wu ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Success Rate ◽  
Pulmonary Vein ◽  
Recurrence Rate ◽  
Paroxysmal Atrial Fibrillation ◽  
Coupling Interval ◽  
Ablation Success

Introduction. A concealed pulmonary vein (PV) bigeminy (cPVB) may be found in some patients with atrial fibrillation (AF) during sinus rhythm (SR). The aim of this study was to investigate whether the presence of cPVB during SR is associated with a higher PV firing. Methods and Results. Seven hundred seventy-six PVs (excluding 5 right middle PVs and 8 left common trunks) were mapped in 198 patients with paroxysmal AF (PAF) who underwent circumferential PV isolation. cPVB with a mean coupling interval of 136 ± 16 ms during SR was observed prior to ablation in 22 (11%) patients. Focal firing was provoked prior to ablation in 144 (19%) PVs. The incidence of focal firing was greater in PVs exhibiting cPVB compared with PVs without cPVB (89% vs. 16%; P<0.001). Also, the number of radiofrequency applications required for isolation was greater in ipsilateral PVs, exhibiting cPVB compared with ipsilateral PVs without cPVB (21.6 ± 6.8 vs. 18.2 ± 5.6; P=0.024). During a follow-up of 32 ± 20 months, the single ablation success rate was 82%. Compared with patients without cPVB, patients with cPVB were associated with higher recurrence rate of AF (27% vs. 17%; p=0.032). Conclusion. cPVB during SR was observed prior to index ablation in 11% of PAF patients. Such a potential itself may be a PV firing in a concealed manner, which does not reactivate LA. The PV exhibiting cPVB required a greater number of radiofrequency applications for isolation. Compared to patients without cPVB, the recurrence rate of AF in patients with cPVB was greater.

Withdrawal of anti-arrhythmic therapy after cavo-tricuspid isthmus ablation of typical atrial flutter

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
S Couto Pereira ◽  
T Rodrigues ◽  
J Brito ◽  
P Silverio Antonio ◽  
B Valente Silva ◽  
...  
Keyword(s):  
Atrial Flutter ◽  
Clinical Characteristics ◽  
Cox Regression ◽  
Simple Procedure ◽  
Symptom Control ◽  
Atrial Arrhythmias ◽  
Chi Square ◽  
Loop Recorder ◽  
Typical Atrial Flutter

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Medical management of typical atrial flutter (AFL) is sometimes unsuccessful and may have adverse effects. Symptom control using radiofrequency cavo-tricuspid isthmus ablation (CTA) is a feasible alternative, given the fact that it is a simple procedure with a low rate of complications. However, in some patients (pts), new atrial arrhythmias may develop and the decision of anti-arrhythmic therapy (AAT) withdrawal is usually patient-based. Purpose To predict the recurrence of atrial arrhythmias (AR) after CTI ablation between pts that suspended AAT and those that maintained AAT. Methods Single-center retrospective study of pts with typical AFL submitted to ablation between 2015 and 2019. Pts clinical characteristics, current and follow up therapy were collected. Holter and/or 7-day event loop recorder were performed during the follow up to identify AR. For statistical analysis, we applied Chi-square, Mann-Whitney and Cox regression to identify predictors of AR. Results CTA ablation was performed in 476 pts (mean age: 66.3 ± 11.7 years, 79.8% males). At time of ablation most pts were in EHRA II class (70.8%) and 44.6% of pts had at least mild left atrial dilatation on transthoracic echocardiography. The mean follow up time was 2.8 years. Two-hundred sixty-nine pts (57,6%) were under anti-arrhythmic therapy (AAT) before the ablation. After the procedure, 58 pts withdrawn AAT before AR and 8 pts after AR. During the follow-up period, we observed AR of typical AFL in 17 pts (3.6%), atypical AFL in 35 pts (7.4%) and AF in 118 pts (24.8%). There were no statistically significant differences regarding AR between pts that maintained and suspended AAT (p = NS). Concerning the pts that suspended AAT, thyroid disfunction (p = 0.012), higher CHADs-VASc score (p = 0.033), ischemic cardiomyopathy (p = 0.001) and tobacco abuse (p = 0.005) were predictors of AR, being the last two also independent predictors (HR 0.243; 95%CI 0.76-0.778, p = 0.017; HR 4.449; 95%CI 1.128-17.553, p = 0.033, respectively).  Conclusion After CTA ablation, AF is the most frequent recurrent arrhythmia. Interestingly, the withdrawn of AAT didn’t seem to predict the recurrence of arrhythmic events. The decision of stopping AAT must be individualized regarding patients’ clinical characteristics. Abstract Figure 1: AAT withdrawal and AR

scholarly journals Relationship between cardiac structure and function and atrial fibrillation related hospitalizations following catheter ablation

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
F.J Olsen ◽  
S Darkner ◽  
X Chen ◽  
S Pehrson ◽  
A Johannessen ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Catheter Ablation ◽  
Sinus Rhythm ◽  
Longitudinal Strain ◽  
Global Longitudinal Strain ◽  
Funding Source ◽  
Risk Patients ◽  
Atrial Strain ◽  
And Function

Abstract Background Even though catheter ablation (CA) is an effective treatment for atrial fibrillation (AF), AF-related hospitalizations and cardioversions are common following this procedure. Purpose To investigate whether echocardiographic measures of left atrial (LA) function could predict AF-related hospitalizations and cardioversions. Methods This was a substudy of a trial that randomized patients to amiodarone vs place to reduce AF recurrence following CA. Transthoracic echocardiography was performed prior to CA and included assessment of: end-systolic and end-diastolic LA volumes, emptying fraction (LAEF), atrial strain, and global longitudinal strain (GLS). Poisson regression was used to assess predictive value for AF-related hospitalizations and cardioversions. Multivariable adjustments were made for: age, gender, ejection fraction, AF burden, AF subtype, dyspnea, and class 1c antiarrhythmics. Results Of the 212 patients, 80 were hospitalized for AF (206 times), and 77 were cardioverted (192 times) within the 6 months follow-up period. Mean age was 60 years, 83% were men, and mean LVEF was 50%. In univariable analyses, LA volumes, LAEF and GLS were predictors of the outcomes but did not remain significant predictors after multivariable adjustments. During echocardiography 162 patients were in sinus rhythm and 50 had AF rhythm. Rhythm during the echocardiogram modified the association between GLS and outcomes (p for interaction &lt;0.05 for both endpoints), such that GLS predicted both AF-related hospitalizations and cardioversions in patients with sinus rhythm but not AF during the echocardiogram (figure). Conclusion Global longitudinal strain predicts AF-related hospitalizations and cardioversions after CA, but only in patients presenting in sinus rhythm during the echocardiogram. Patients presenting with impaired global longitudinal strain should be considered high-risk patients following CA who may benefit from close follow-up. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): The Danish Heart Foundation

scholarly journals A new approach to atrial flutter ablation using functional substrate mapping with wavefront discontinuity during sinus rhythm

EP Europace ◽  
2021 ◽  
Vol 23 (Supplement_3) ◽  
Author(s):  
D Valbom Mesquita ◽  
L Parreira ◽  
J Farinha ◽  
R Marinheiro ◽  
P Amador ◽  
...  
Keyword(s):  
Sinus Rhythm ◽  
Atrial Flutter ◽  
Small Area ◽  
Low Voltage ◽  
Categorical Variables ◽  
Accurate Identification ◽  
Funding Sources ◽  
Slow Conduction ◽  
Voltage Mapping ◽  
Conduction Zone

Abstract Funding Acknowledgements Type of funding sources: None. Background Ultra high-density (UHD) mapping allows accurate identification of local abnormal electrograms and low voltage within a small area range, allowing precise identification of reentry circuits. Areas with high isochronal density in a small area known as deceleration zones (DZ) are responsible for reentry. Purpose Identify the DZ and areas of low voltage in sinus rhythm (SR) and evaluate the feasibility of performing atrial flutter (AFL) ablation by targeting those zones. Methods We prospectively enrolled patients in SR referred for AFL ablation (either typical or atypical). An isochronal late activation mapping (ILAM) during SR with UHD catheter was performed, annotating latest deflection of local electrograms. DZ were defined as areas with &gt;3 isochrones within 1cm radius, prioritizing zones with maximal density. Atrial flutter was then induced and ILAM during flutter was performed for comparison. Voltage mapping was also assessed (0.1-0.5mV). Ablation targeted DZ in SR that displayed the higher voltage. DZ in SR were compared to DZ in AFL. Number of radiofrequency (RF) applications needed to terminate AFL were assessed. After AFL termination, complete line of the slow conduction zone was completed, and pulmonary vein isolation (PVI) was done in case of left AFL. Categorical variables are presented in absolute and relative values and median and interquartile range were used for numerical variables, as well t-student test for correlation of numerical variables. Results We studied 6 AFL (4 atypical, 66.7%) in 5 patients, 2 male (40%), median age 70 (64- 72). UHD ILAM in SR with 2195 points (1212-2865) and 2197 points (1356-3102) in AFL (p = 0.62).  The UHD ILAM identified a median of (QR) DZ in SR, that colocalized with AFL isthmus and DZ in AFL in 100%. DZ were not always located in low voltage areas. Aiming at the higher voltage in the DZ terminated the AFL in all cases, with a median RF time of 38 (25-58) seconds and AFL was no longer inducible. However, according to protocol, the complete line of slow conduction zone was done, with a median RF time of 1049.5 (274-1194) seconds (p = 0,009). Conclusions Isochronal mapping in sinus rhythm with UHD catheters can display the functional substrate for reentry in AFL, allowing a substrate guided ablation in case of non-inducible AFL. Targeting the areas of high isochronal density, is effective in terminating AFL, obviating the need for extensive ablation. Abstract Figure.

Transitions among atrial fibrillation, atrial flutter, and sinus rhythm during procainamide infusion and vagal stimulation in dogs with sterile pericarditis

1991 ◽  
Vol 69 (1) ◽  
pp. 15-24 ◽  
Author(s):  
Pierre L. Pagé ◽  
Hamid Hassanalizadeh ◽  
René Cardinal
Keyword(s):  
Atrial Fibrillation ◽  
Sinus Rhythm ◽  
Atrial Flutter ◽  
Right Atrium ◽  
Cycle Length ◽  
Vagal Stimulation ◽  
Right Atrial ◽  
Free Wall ◽  
Circus Movement ◽  
The Right

The mechanism of atrial flutter and fibrillation induced by rapid pacing in 22 dogs with 3-day-old sterile pericarditis was investigated by computerized epicardial mapping of atrial activation before and after administration of agents known to modify atrial electrophysiologic properties: procainamide, isoproterenol, and electrical stimulation of the vagosympathetic trunks. Before the administration of any of these agents, a total of 30 episodes of sustained atrial flutter (> 1 min duration, monomorphic; regular cycle length, 127 ± 12 ms, mean ± SD) was induced in 15 out of 22 dogs and 9 episodes of unstable atrial flutter (duration, <1 min; cycle length, 129 ± 34 ms; monomorphic, alternating with fibrillation) were induced in the remaining 7 preparations. In the latter, administration of procainamide transformed unstable atrial flutter and atrial fibrillation to sustained atrial flutter (cycle length, 142 ± 33 ms; n = 9 episodes). During control atrial flutter, atrial maps displayed circus movement of excitation in the right atrial free wall with faster conduction parallel to the orientation of intra-atrial myocardial bundles. Vagal stimulation changed atrial flutter to atrial fibrillation in 32 of 73 trials; this was associated with acceleration of conduction in the lower right atrium, leading to fragmentation of the major wave front. Isoproterenol produced a 6–25% increase of the atrial rate in 6 out of 14 trials of atrial flutter and induced atrial fibrillation in 4. After procainamide, the reentrant pathway was lengthened and conduction was slowed further in the right atrium. Maps obtained during unstable atrial flutter showed incomplete circuits involving the right atrium. Following procainamide infusion, the area of functional dissociation or block was enlarged and a stable circus movement pattern, which was similar to the pattern seen in control atrial flutter, was established in the right atrium. We conclude that (1) the transitions among atrial fibrillation, atrial flutter, and sinus rhythm occur between different functional states of the same circus movement substratum primarily located in the lower right atrial free wall, and (2) the anisotropic conduction properties of the right atrium may contribute to these reentrant arrhythmias and may be potentiated by acute pericarditis.Key words: atrial flutter, atrial fibrillation, atrial mapping, antiarrhythmic drugs, vagal stimulation.

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