Classification of atrial flutter and regular atrial tachycardia according to electrophysiologic mechanism and anatomic bases: a statement from a joint expert group from the Working Group of Arrhythmias of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology.

Regular atrial tachycardias classically are classified into flutter or tachycardia, depending on the rate and presence of a stable baseline on the ECG. However, current understanding of electrophysiology atrial tachycardias makes this classification obsolete, because it does not correlate with mechanisms. The proposed classification is based on electrophysiologic mechanisms, defined by mapping and entrainment. Radiofrequency ablation of a critical focus or isthmus can afford proof. Focal tachycardias are characterized by radial spread of activation and endocardial activation not covering the whole cycle. Ablation of the focus of origin interrupts the tachycardia. The mechanism of focal firing is difficult to ascertain by clinical methods. Macroreentrant tachycardias are characterized by circular patterns of activation that cover the whole cycle. Fusion can be shown during entrainment on the ECG or by multiple endocardial recordings. Ablation of a critical isthmus interrupts the tachycardia. Macroreentry can occur around normal structures (terminal crest, eustachian ridge) or around atrial lesions. The anatomic bases of these tachycardias must be defined, to guide appropriate treatment. Atrial flutter is a mere description of continuous undulation on the ECG, and only some strictly defined typical flutter patterns correlate with right atrial macroreentry bounded by the tricuspid valve, terminal crest, and caval vein orifices. This classification should be considered open, as some classically described tachycardias, such as reentrant sinus tachycardia, inappropriate sinus tachycardia, and type II atrial flutter, cannot be classified accurately. Furthermore, the possibility of fibrillatory conduction makes the limits with atrial fibrillation still ill defined.

A peculiar form of focal atrial tachycardia mimicking atypical atrial flutter.

A 55-year-old man was referred because of congestive heart failure and atrial flutter. A 12-lead electrocardiogram (ECG) showed positive P waves in leads II, III, and aVF with a continuously undulating pattern that lacked an isoelectric baseline. Tachycardia was diagnosed as atypical atrial flutter based on classical criteria. An electrophysiological study and catheter ablation using an electroanatomical system revealed the mechanism of the tachycardia to be focal atrial tachycardia originating from the left atrial roof. This case indicates that focal atrial tachycardia may present as atypical atrial flutter on the surface ECG.

Demonstration of diastolic and presystolic Purkinje potentials as critical potentials in a macroreentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia.

OBJECTIVES: The purpose of this study was to determine the relation of diastolic and presystolic potentials recorded during verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) to reentry circuit. BACKGROUND: Successful ablation of verapamil-sensitive ILVT at the zone of slow conduction from which the diastolic potential is recorded has been reported. However, the relationship between the diastolic potential and the reentrant circuit remains a matter of debate. METHODS: Radiofrequency (RF) ablation was performed in 20 patients with verapamil-sensitive ILVT. After identifying the ventricular tachycardia (VT) exit site, we searched for the mid-diastolic potential (P1) during VT. Entrainment followed by RF current application was performed. If the mid-diastolic potential could not be detected, RF current was applied at the VT exit site showing the earliest ventricular activation with a single fused presystolic Purkinje potential (P2). RESULTS: In 15 of 20 patients, both P1 and P2 were recorded during VT from midseptal region. Entrainment pacing captured P1 orthodromically and reset the VT. The interval from stimulus to P1 was prolonged as the pacing rate was increased. Radiofrequency ablation was successfully performed at this site in all 15 patients. After successful ablation, P1 appeared after the QRS complex during sinus rhythm with the identical sequence to that during VT. In the remaining five patients, the diastolic potential could not be detected, and a single fused P2 was recorded only at the VT exit site. Successful ablation was performed at this site in all five patients. CONCLUSIONS: This study demonstrates that P1 and P2 are critical potentials in a circuit of verapamil-sensitive ILVT and suggests the presence of a macroreentry circuit involving the normal Purkinje system and the abnormal Purkinje tissue with decremental property and verapamil-sensitivity.

Successful radiofrequency catheter ablation from the supravalvular region of the aortic valve in a patient with outflow tract ventricular tachycardia.

Outflow tract ventricular tachycardia (OT-VT) was successfully ablated from the right coronary cusp of the aortic valve. The 12-lead ECG was totally different from the typical right ventricular OT-VT because the R/S ratio in precordial lead V1 was equal to 1 and tall R waves in precordial leads V2-6 were seen. Radiofrequency energy application from the right coronary cusp of the aortic valve successfully ablated this VT without complications. Radiofrequency catheter ablation from the right coronary cusp of the aortic valve can be done safely and effectively.

Clinical significance of residual slow cavotricuspid isthmus conduction after ablation of typical atrial flutter.

The purpose of this study was to evaluate the clinical significance of residual slow cavotricuspid isthmus (IT) conduction on the ablation line after typical atrial flutter (AF) ablation, undetected by analysis of right atrial (RA) activation. Seventy patients with AF underwent IT ablation. In the first 35 patients (group I), IT block was verified only by the RA activation sequence. In the subsequent 35 patients (group II), IT block was verified by the presence of parallel double potentials with an isoelectric interval through the entire ablation line (in addition to RA activation sequence criteria) during pacing from the low lateral RA and the coronary sinus ostium. In group I patients, residual IT conduction was retrospectively analyzed at the ablation site immediately after the last radiofrequency (RF) application. Six of 33 group I patients (18%) with IT block had residual IT conduction represented by fractionated or multicomponent potentials immediately after the final RF application. Four of these 6 patients (67%) had recurrences of AF, 3 +/- 1.4 months after ablation. Four (12%) of 33 group II patients with IT block had residual IT conduction in the ablation line after creation of IT block confirmed by RA activation sequence. This conduction was eliminated by 1.6 +/- 0.9 further RF applications in all 4 patients. No AF recurrence was observed in group II patients. Up to 18% of patients with apparent IT ablation had residual slow IT conduction on the ablation line. This conduction was associated with AF recurrences and must be eliminated to achieve complete cure of AF.

Nonlinear ablation targeting an isthmus of critically slow conduction detected by high-density electroanatomical mapping for atypical atrial flutter.

Focused high-density atrial endocardial mapping was performed with a three-dimensional electroanatomical mapping system or a multielectrode basket catheter in six men and two women (mean age = 54 years) with atypical atrial flutter (AFL) to characterize its reentry circuit and identify its isthmus of critically slow conduction (ICSC). Activation mapping revealed figure-8 reentry with ICSC between a surgical atrial scars in three atypical AFLs following atriotomy, and between the crista terminalis (CT) and the inferior (IVC) or superior (SVC) vena cavae in atypical right atrial (RA) AFL in absence of prior atriotomy. Figure-8 double loop reentry was documented in one RA atypical AFL. ICSC was characterized by concealed entrainment with a post-pacing interval identical to the AFL cycle length, and a mid-diastolic fractionated electrogram, 129 +/- 23 ms in duration, spanning the isoelectric line between double potentials on adjacent area of conduction block. All AFLs were successfully ablated with 4.9 +/- 4.3 RF pulses applied at ICSC. A possible mechanism of atypical AFL consists of figure-8 reentry with ICSC between surgical scars in postoperative AFL, and between the CT and the IVC/SVC in RA AFL not preceded by cardiac surgery. Late and partial regeneration of conduction across the atriotomy scar can create an ICSC. Nonlinear ablation targeting ICSC can cure atypical AFL, whether it follows surgery or not.

Electrocardiographic characteristics of left ventricular outflow tract tachycardia.

Catheter ablation of idiopathic left ventricular outflow tract tachycardia (LVOT-VT) is rare because a safe ablation technique at this site has not been described, and serious complications may occur. This study compared the QRS morphology of LVOT-VT with that of idiopathic right ventricular outflow tract tachycardia. A comparison was made between the electrocardiographic characteristics of LVOT-VT originating from the supravalvular region of a coronary cusp (Supra-Ao group) with those of LVOT-VT originating from the infravalvular endocardial region of a coronary cusp of the aortic valve within the LV (Infra-Ao group). After precise mapping of the right ventricle, left ventricle, pulmonary artery, coronary cusps, and proximal portion of the anterior interventricular vein, there were 17 patients in whom VT was thought to be located at the LVOT by both activation and pace mapping. They were divided between a Supra-Ao group (n = 8), and an Infra-Ao group (n = 9). Analysis of the 12-lead electrocardiogram (ECG) revealed an S wave in lead I in all 17 patients. A precordial R wave transition was also observed at V1 or V2 in 16 patients (94%). In 7 of 8 patients (88%) with Supra-Ao LVOT-VT, no S wave was observed in either V5 or V6. In contrast, an Rs pattern was observed in both V5 and V6, or in V6 only, in 100% of the patients with Infra-Ao LVOT-VT. A LVOT-VT should be suspected when the ECG shows an S wave in lead I and an R/S ratio greater than 1 in lead V1 or V2, versus a coronary cusp location if there is no S wave in either lead V5 or V6.

A jump in cycle length of orthodromic common atrial flutter during catheter ablation at the isthmus between the inferior vena cava and tricuspid annulus; evidence of dual isthmus conduction directed to dual septal exits.

INTRODUCTION: In orthodromic common atrial flutter (AFL), details of intraseptal propagation of the flutter (FL) wave exiting from the isthmus between the inferior vena cava and tricuspid annulus (IVC-TA isthmus) remain unknown. We hypothesized the existence of dual septal exits of the FL wave from the IVC-TA isthmus to both the anterior, coronary sinus ostium (CSO-TA) isthmus, and the posterior septal (IVC-CSO) isthmus, and that the IVC-TA isthmus might consist of dual muscle bundles directed to both septal isthmuses over the eustachian ridge; therefore, segmental ablation of the IVC-TA isthmus could change intraseptal FL wave propagation. METHODS AND RESULTS: To test the hypothesis, we investigated the influence of segmental ablation of the IVC-TA isthmus on intraseptal FL wave propagation. In seven of 40 (18%) consecutive patients, segmental ablation of the ventricular side of the IVC-TA isthmus during orthodromic common AFL led to sudden prolongation of the flutter cycle length (FCL) (from 266 +/- 33 ms to 291 +/- 45 ms) associated with changes in intraseptal activation sequences. They consisted of prolongation of the interval between the IVC-TA isthmus and the CSO (from 38 +/- 13 ms to 86 +/- 25 ms), shortening of the interval between the CSO and His (from 31 +/- 15 ms to 9 +/- 15 ms), and atrial electrogram polarity change at the His-bundle recording site. Morphological change in the FL wave was also seen on the 12-lead ECG. CONCLUSIONS: In some patients, segmental ablation of the IVC-TA isthmus can lead to a jump in FCL and changes in intraseptal activation sequences of FL waves due to anterior-to-posterior shifting of the septal exit. This indicates that the IVC-TA isthmus may contain dual circumferential muscle bundles as conduction pathways directed to dual septal exits both anterior and posterior to the CSO.

Thrombolytic therapy can reduce the arrhythmogenic substrate after acute myocardial infarction: a study using the signal-averaged electrocardiogram, endocardial catheter mapping and programmed ventricular stimulation.

Thrombolytic therapy improves survival after acute myocardial infarction (AMI) primarily by preserving left ventricular function. Its influence on the arrhythmogenic substrate remains uncertain. To investigate the electrophysiologic effects of thrombolytic therapy, signal-averaged electrocardiography, endocardial catheter mapping and programmed stimulation were performed in 93 consecutive patients with their first AMI who underwent thrombolytic therapy. Early reperfusion was achieved in 75 patients (group 1), but not in 18 patients (group 2). The incidence of the signal-averaged electrocardiogram abnormality was 11% in group 1 (8 of 75 patients) and 33% in group 2 (6 of 18 patients) (p<0.02). Catheter mapping detected delayed endocardial electrograms in 30 group 1 patients and 10 group 2 patients (p=NS). The spatial distribution of these electrograms was smaller, and the longest duration of endocardial electrograms was shorter in group 1 than in group 2 (p<0.01). Sustained monomorphic ventricular tachycardia was induced less commonly in group 1 (20%) than in group 2 (44%) (p<0.05). In conclusion, thrombolytic therapy can reduce the arrhythmogenic substrate and improve electrical stability after AMI. This antiarrhythmic effect may contribute, in part, to the improved survival of patients treated with thrombolytic drugs.

A case of catheter ablation of accessory atrioventricular connection between the right atrial appendage and right ventricle guided by a three-dimensional electroanatomic mapping system.

A 12-year-old girl was referred to our institution because of frequent episodes of AV reciprocating tachycardia. Ventriculoatrial and AV intervals were relatively long along the tricuspid annulus. Earliest retrograde atrial activation was recorded at the mid-portion of the right atrial appendage, 7 mm from the tricuspid annulus. The CARTO electroanatomic mapping system was very useful for providing accurate spatial orientation of the accessory connection. Complete ablation of this connection required multiple radiofrequency energy applications over an extensive area because of the multicomponent structure of the connection.

Optimal target site for slow AV nodal pathway ablation: possibility of predetermined focal mapping approach using anatomic reference in the Koch's triangle.

INTRODUCTION: Although a variety of ablation techniques have been developed in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT), there have been few reports discussing the location of the optimal target site. Based on our early experiences, we hypothesized that radiofrequency (RF) current applied around the upper margin of the coronary sinus ostium (UCSO) results in the most effective and safe treatment of AVNRT. METHODS AND RESULTS: To confirm our hypothesis, the efficacy of RF currents applied around the UCSO guided by local electrograms in 59 patients (group B: predetermined focal mapping approach) were compared with the outcomes in 60 other patients previously treated with the standard electrogram-guided mapping method starting around the lower margin of the coronary sinus ostium (group A). The precise location of ablation catheters at successful sites (S) was also evaluated. All the patients were successfully treated without complications. Significantly fewer RF pulses and lower energies were needed in group B patients (mean RF applications: 4.3 vs 1.4 applications, mean total energy delivered: 4,699 vs 2,236 J in groups A and B, respectively, P < 0.01). Detailed analyses of the anatomical locations of S using CS venography in group B patients who received only a single RF application (46 patients) revealed that the distance between His and S varied according to the length of Koch's triangle, while that between S and UCSO was relatively constant. In 85 % of these 46 patients, S was located within 5 mm above and below the level of the UCSO. CONCLUSION: RF applications around the UCSO guided by local electrograms yielded excellent outcomes in AVNRT patients with wide varieties in the size of Koch's triangle. The optimal target site was located within 5 mm above and below the level of UCSO along the tricuspid annulus.

Radiofrequency catheter ablation for sinoatrial node reentrant tachycardia: electrophysiologic features of ablation sites.

The aim of this study was to investigate catheter ablation of sino-atrial reentrant tachycardia (SART) and the electrophysiologic characteristics of the ablation sites. From January 1990 to October 1997, 651 patients with supraventricular tachycardia were referred and 11 patients were found to have SART. Ablation was successful in all cases with a mean number of 3.3 radiofrequency (RF) current pulses. SART terminated during 22 of 36 RF pulses. In spite of prompt termination, tachycardia could be re-induced in 3 of 11 patients with its earliest activation site shifted. At effective ablation sites, the electrograms during tachycardia were characterized as fractionated (75+/-17 ms), and 38+/-16 ms prior to surface P wave, and 42+/-18 ms prior to the high right atrium. Unipolar electrograms revealed a sharp negative unipolar deflection, so called QS pattern, in 15 of 20 sites during SART and 15 of 15 sites during sinus rhythm. During effective applications, atrial premature beats (APB) with activation sequences identical to sinus rhythm appeared in 14 of 22 cases. Effective ablation sites of SART showed fractionated electrograms during tachycardia and sinus rhythm. Unipolar electrogram with a QS pattern and APB during energy application could be an indicator of the optimal ablation sites.

Retrograde Purkinje potential activation during sinus rhythm following catheter ablation of idiopathic left ventricular tachycardia.

We describe two patients with idiopathic left ventricular tachycardia that were cured by radiofrequency catheter ablation. Tachycardia was inducible by ventricular stimulation and was verapamil sensitive. Two distinct presystolic potentials (P1 and P2) were recorded during tachycardia in the mid-septal or inferoapical area, but only one potential (P2) was recorded during sinus rhythm. After catheter ablation at this site, the P1 potential was noted after the QRS complex during sinus rhythm, while the P2 was still observed before the QRS complex. The P1 potential showed a decremental property during atrial or ventricular pacing. These data suggest that Purkinje tissue with decremental properties was responsible for the tachycardia mechanism, and that the reentry circuit involving this tissue is likely to be of considerable size.

Verapamil-sensitive left anterior fascicular ventricular tachycardia: results of radiofrequency ablation in six patients.

INTRODUCTION: Verapamil-sensitive left ventricular tachycardia (VT) with a right bundle branch block (RBBB) configuration and left-axis deviation has been demonstrated to arise from the left posterior fascicle, and can be cured by catheter ablation guided by Purkinje potentials. Verapamil-sensitive VT with an RBBB configuration and right-axis deviation is rare, and may originate in the left anterior fascicle. METHODS AND RESULTS: Six patients (five men and one woman, mean age 54+/-15 years) with a history of sustained VT with an RBBB configuration and right-axis deviation underwent electrophysiologic study and radiofrequency (RF) ablation. VT was slowed and terminated by intravenous administration of verapamil in all six patients. Left ventricular endocardial mapping during VT identified the earliest ventricular activation in the anterolateral wall of the left ventricle in all patients. RF current delivered to this site suppressed the VT in three patients (ablation at the VT exit). The fused Purkinje potential was recorded at that site, and preceded the QRS complex by 35, 30, and 20 msec, with pace mapping showing an optimal match between the paced rhythm and the clinical VT. In the remaining three patients, RF catheter ablation at the site of the earliest ventricular activation was unsuccessful. In these three patients, Purkinje potential was recorded in the diastolic phase during VT at the mid-anterior left ventricular septum. The Purkinje potential preceded the QRS during VT by 66, 56, and 63 msec, and catheter ablation at these sites was successful (ablation at the zone of slow conduction). During 19 to 46 months of follow-up (mean 32+/-9 months), one patient in the group of ablation at the VT exit had sustained VT with a left bundle branch block configuration and an inferior axis, and one patient in the group of ablation at the zone of slow conduction experienced typical idiopathic VT with an RBBB configuration and left-axis deviation. CONCLUSION: Verapamil-sensitive VT with an RBBB configuration and right-axis deviation originates close to the anterior fascicle. RF catheter ablation can be performed successfully from the VT exit site or the zone of slow conduction where the Purkinje potential was recorded in the diastolic phase.

Catheter ablation for ventricular tachycardia from a diverticulum at the right ventricular outflow tract.

A case is presented of a 73-year-old man with drug resistant ventricular tachycardia that originated from the right ventricular outflow tract. A right ventriculogram showed a diverticulum in the interventricular septum at the right ventricular outflow tract. Low energy radiofrequency catheter ablation within the diverticulum was performed successfully and safely.

Retrograde multiple and multifiber accessory pathway conduction in the Wolff-Parkinson-White syndrome: potential precipitating factor of atrial fibrillation.

INTRODUCTION: The determinants of susceptibility to atrial fibrillation (AF) and the existence of accessory pathway conduction have remained unidentified in the Wolff-Parkinson-White (WPW) syndrome. We tested the hypothesis that excitation inputs into the atrium over a retrograde multiple or multifiber accessory pathway during AV reentrant tachycardia (AVRT) could precipitate initiation of AF. METHODS AND RESULTS: Two hundred fifty consecutive patients with WPW syndrome underwent electrophysiologic study and radiofrequency catheter ablation. The patients were classified into two groups according to the study results: 29 with retrograde multiple or multifiber accessory pathway (MP) and 221 with retrograde single accessory pathway (SP). Compared with the SP patients, the MP patients showed a significantly higher incidence of clinical AF (MP vs SP: 19/29 vs 51/221, P < 0.01), induced AF (12/29 vs 32/221, P < 0.01), and initiated AF during ventricular pacing and AVRT (10/12 vs 17/32, P < 0.05). There were no differences between the two groups in incidence of clinical and induced AVRT (24/29 vs 200/221 and 25/29 vs 206/221, respectively), mean cycle length of induced AVRT, or electrophysiologic parameters of the accessory pathway. AF inducibility during AVRT or ventricular pacing was eliminated by partial ablation in 7 of 10 patients with MP. After total ablation, the incidence of induced AF was similar between the two groups (MP vs SP: 1/29 vs 11/221). CONCLUSION: The existence of a retrograde multiple or multifiber accessory pathway in patients with WPW syndrome is associated with a higher incidence of clinical and induced AF. Successful ablation of the retrograde multiple or multifiber accessory pathway can eliminate the induction of both AVRT and AF.

High energy radiofrequency catheter ablation for common atrial flutter targeting the isthmus between the inferior vena cava and tricuspid valve annulus using a super long tip electrode.

There have been controversies concerning the optimal target sites and approaches in radiofrequency catheter ablation of common atrial flutter. We attempted high energy radiofrequency catheter ablation targeting the isthmus between the inferior vena cava and tricuspid valve annulus (IVC-TV isthmus) with a super long (8 mm) tip electrode, and compared the efficacy of this anatomical approach with the electrophysiological approach targeting the posteroseptal right atrium posterior to the coronary sinus using a standard 4-mm tip electrode. Atrial flutter was successfully ablated in 12 of 12 patients (100%) without recurrence with the anatomical approach, while, in 7 of 9 patients (64%) with 2 recurrences with the electrophysiological approach. In comparison of ablation data between the anatomical and electrophysiological approaches, there were significant differences in the mean number of application pulses (anatomical vs electrophysiological: 2.3 +/- 0.8 vs 9.9 +/- 6.4, P < 0.01), applied wattage (39 +/- 12 W vs 24 +/- 6 W, P < 0.01), applied energy per application (1,986 +/- 426 J vs 659 +/- 323 J, P < 0.01), fluoroscopic time (26 +/- 11 min vs 74 +/- 30 minutes, P < 0.01), and procedure time (59 +/- 8 min vs 181 +/- 53 min, P < 0.01). In conclusion, the anatomical approach is superior to the electrophysiological one with respect to procedure and radiation time, and linear ablation at the IVC-TV isthmus with an 8-mm tip electrode and high energy application is highly effective and safe.