Characteristics and radiofrequency ablation therapy of intermediate septal accessory pathway

Iatrogenic cardiomyopathy in patients with manifest right supero-paraseptal accessory pathways

INTRODUCTION

We describe two patients with right supero-paraseptal accessory pathway (SPAP) who developed left ventricular dysfunction associated with an increased degree of ventricular pre-excitation and frequent orthodromic reciprocating tachycardia (ORT) due to worsening atrioventricular (AV) node conduction.

METHODS AND RESULTS

Case 1: 48-year-old female with a history of normally functioning mechanical mitral valve, CABG, and ventricular pre-excitation that worsened after her open heart surgery. She presented with frequent palpitations with documented supraventricular tachycardia (SVT) and found to have a new left ventricular dysfunction with decrease in left ventricular ejection fraction (LVEF) from 55% to 46% with dyssynchrony. An electrophysiological study confirmed a right SPAP and ORT. The pathway was successfully ablated from the antegrade approach after careful mapping. After ablation and 6-month follow up echocardiogram showed improvement of EF to 54% and the LV dyssynchrony resolved. Case 2: 51-year-old male with a history of frequent SVT with recent unsuccessful ablations that resulted in worsening ventricular pre-excitation, more frequent SVT, and new left ventricular dysfunction (LVEF from 60% to 40%). He was started on amiodarone which resulted in significant sinus bradycardia, intermittent ventricular pre-excitation, and first degree AV block with significant increase in ORT events. His electrophysiology study confirmed SPAP which was successfully ablated from the antegrade approach after careful mapping. After 1 month, follow-up echocardiogram showed an improved ejection fraction to 60%.

CONCLUSION

Left ventricular dysfunction due to dyssynchrony and symptomatic frequent ORT of right SPAP can develop in the setting of new iatrogenic diminished AV node conduction. Successful ablation will result in LV function recovery to baseline.

Catheter ablation of anteroseptal accessory pathways from the aortic cusps: A case series and a review of the literature

Data regarding catheter ablation of anteroseptal accessory pathways through the aortic cusps are limited. We describe two cases of true para-Hisian accessory pathways successfully ablated from the aortic cusps (right coronary cusp and non-coronary cusp, respectively) along with a review of the current literature. Due to the close proximity to the atrioventricular node and the high risk of complication, mapping of the aortic cusps should always be considered in the case of anteroseptal accessory pathways. Anteroseptal accessory pathways can be safely and effectively ablated from the aortic cusps with good long-term outcomes.

Risk factors of recurrence and complication in radiofrequency catheter ablation of atrioventricular reentrant tachycardia in children and adolescents

BACKGROUND

To compare potential risk factors for complications and recurrence after radiofrequency catheter ablation in symptomatic atrioventricular reentrant tachycardia in children and adolescents.

METHODS

We retrospectively reviewed the data of 213 consecutive patients with symptomatic atrioventricular reentrant tachycardia who underwent both electrophysiological study and radiofrequency catheter ablation, divided these patients into two groups, children (age < 12 years) and adolescents (12 < or = rage, 18 years), and compared the location of the accessory pathway, success rate, recurrence rate, complications, presence of congenital heart disease, presence of intermittent ventricular pre-excitation, and presence of Wolff–Parkinson–White syndrome in the two groups.

RESULTS

The position of the accessory pathway was mostly right sided in children (61.3%) and left sided in adolescents (61.5%). Children had significantly more congenital heart disease than adolescents (6.4% versus 0.8%). Univariate analysis showed children or adolescents with right-sided accessory pathways to be 6.84 times and those with accessory pathways on both sides of the septum 25 times more likely to relapse than those with a single accessory pathway. Multivariate analysis indicated that children or adolescents with two accessory pathways were six times, and those with intermittent ventricular pre-excitation nine times more at risk of relapsing following radiofrequency ablation than those with single accessory pathways. All five complications occurred in children.

CONCLUSIONS

The findings suggest that the position and number of accessory pathways and presence of intermittent ventricular pre-excitation are related to risks of recurrence of atrioventricular reentrant tachycardia in children and adolescents.

Cryoablation of anteroseptal accessory pathways in children with limited fluoroscopy exposure

Due to its safety profile, cryoablation is used increasingly in pediatric patients, especially for septal arrhythmia substrates. Recent advances in electroanatomical-mapping technologies have resulted in a decrease or complete elimination of fluoroscopy exposure during catheter ablation procedures. The aim of this study was to assess the efficacy and safety of cryoablation of anteroseptal accessory pathways (APs) using electroanatomical-mapping system guidance with limited fluoroscopy exposure. A total of 24 patients underwent cryoablation of anteroseptal APs between July 2010 and April 2012. Cryomapping was performed with a 6 mm-tip catheter at -30 °C before the lesions were delivered. An 8 mm-tip catheter was used in one patient. The EnSite system (St. Jude Medical, St Paul, MN) was used in all procedures. The mean age was 11.9 ± 4.3 years. Acute success rate was 95.8 % (23 of 24). The mean procedure and cryoablation durations were 168 ± 58 min and 1,463 ± 525 s, respectively. Limited fluoroscopy was used only in 7 patients, and the mean fluoroscopy time was 1.7 ± 1.8 min (range 0.1-4 min) in these patients. Recurrence was noted in 2 patients (8.7 %) who underwent a second successful cryoablation procedure. The patient who underwent a failed attempt during the first procedure was successfully treated with a repeat procedure. The resultant long-term success rate was 100 % at a mean follow-up period of 14.2 ± 7.7 months. There were no complications except for transient atrioventricular block in one patient. Cryoablation of anteroseptal APs can be performed effectively and safely in children using a limited fluoroscopic approach with the help of electroanatomical-mapping systems.

Measure twice, cut once: pitfalls in the diagnosis of supraventricular tachycardia

In atrioventricular nodal and atrioventricular reentrant tachycardia, the relative timing of atrial and ventricular activation may sometimes be very similar, even during electrophysiological studies, and this may lead to an erroneous diagnosis and inappropriate treatment. As examples, we describe two cases that were recently referred to our hospital for a second opinion and treatment of paroxysmal supraventricular tachycardia. In both, the original diagnosis of the referring centres was commontype atrioventricular nodal reentrant tachycardia. Catheter ablation in those centres was unsuccessful. During our electrophysiological studies, however, an atrioventricular reentrant tachycardia was demonstrated, using a concealed accessory pathway for retrograde conduction in both patients. The accessory atrioventricular connection was successfully ablated and on follow-up both patients remained free of symptoms without medication. These findings illustrate the importance of complete electrophysiological analysis even for apparently simple supraventricular arrhythmias. (Neth Heart J 2010;18:78-84.).

[Invasive electrophysiology: complications, nightmares and their management]

Most minor side effects of ablation in the right atrium and right ventricle relate to femoral venous catheterization but there is a small risk of severe complications including atrioventricular (AV) block, damage of surrounding structures and thromboembolic events. Impairment of AV conduction can occur during ablation of atrioventricular re-entrant tachycardia, ablation of anteroseptal, mid-septal and parahisian accessory pathways, ablation of ectopic atrial tachycardia originating from the vicinity of the atrioventricular node and when ablating the septal isthmus for typical atrial flutter. Damage of the right coronary artery is a very rare complication after inferior isthmus ablation with high energy. The thromboembolic risk during and after cardioversion and ablation of atrial flutter is higher than previously recognized and anticoagulation therapy decreases this risk. The risk of perforation and tamponade during ablation in the right atrium and right ventricle is very low but particular caution is necessary in thin-walled structures such as the coronary sinus and the upper right ventricular outflow tract. Phrenic nerve injury can be avoided by pacing from the mapping electrode before application of radiofrequency energy at the right atrial free wall. Limitation of power output depending on the site of ablation and titration of energy application with continuous control of temperature and impedance should be considered to minimize the risk of complications.

Successful elimination of concealed accessory pathway-mediated tachycardia by ablation of AV nodal slow pathway

We report a case of atrioventricular reentrant tachycardia (AVRT) using a concealed para-Hisian accessory pathway for retrograde conduction, which also required anterograde conduction over the AV nodal slow pathway to maintain the tachycardia. The shortest VA interval during AVRT (70 ms) was noted at a site with His bundle electrogram amplitude of 0.25 mV. The AVRT was cured by radiofrequency ablation of the AV nodal slow pathway without affecting accessory pathway conduction. The patient has not reported any sustained palpitations at 2 years after ablation while receiving no medications. The case presented in this report illustrates a para-Hisian AVRT that was successfully eliminated by an unconventional approach of ablation of the atrial inputs to the AV nodal slow pathway.

Characteristics and radiofrequency ablation in posteroseptal and left free-wall subepicardial accessory pathways

Accessory pathways (APs) that can only be ablated from the coronary sinus are likely to be located subepicardially. The electrocardiographic (ECG) and electrophysiological characteristics as well as the immediate radiofrequency ablation success rate and the recurrence rate were compared in 15 patients (11 posteroseptal and 4 left free-wall) with subepicardial APs and in 31 control patients with posteroseptal (15) and left free-wall (16) APs matched with age, sex, and AP location during the same study period in whom APs were successfully ablated from the endocardial approach. Patients with posteroseptal subepicardial APs had a longer tachycardia cycle length (355 +/- 32 vs 286 +/- 49 milliseconds, P < .05), a lower success rate (9 /11 vs 15/15, P = .09), and a higher recurrence rate (3/9 vs 0/15, P < .05) as compared with control patients. A negative delta wave with QS or QR pattern in lead II was present in all 4 patients with a manifest posteroseptal subepicardial AP located in the middle cardiac vein as compared with none of the 5 control patients with posteroseptal APs located in the proximal coronary sinus and 1 of the 9 control patients (P < .01). A positive delta wave in lead I along with an R/S of less than 1 in lead V 1 , and a negative delta wave in lead II, was noted in 1 of the 2 patients with left free-wall subepicardial APs and none of the 7 controls (P = .047). The local activation time is significantly shorter in the 4 patients with left free-wall subepicardial AP than in the 16 control patients (31 +/- 9 vs 89 +/- milliseconds, P = .044).

CONCLUSIONS

Some ECG characteristics are suggestive of APs located in the middle cardiac vein and left free-wall subepicardial site, while a longer local activation time is characteristic of left free-wall APs. The success rate is lower and the recurrence rate higher with radiofrequency ablation in patients with subepicardial AP.

Cryoablation:. Potentials and Pitfalls

The use of cryoablation in the electrophysiology lab provides some distinct advantages not seen with conventional radiofrequency ablation. Ice mapping allows a functional assessment of a putative ablation site prior to the formation of a permanent lesion. This provides a distinct advantage adjacent to the AV node for para-hisian pathways and difficult cases of AVNRT. Cryoablation also produces minimal endothelial disruption and thrombus formation and causes no collagen shrinkage. This is likely advantageous when ablation is required within venous structures. There is also mounting experimental evidence that cryoablation is safe adjacent to the arterial system, especially within the middle cardiac vein or distal coronary sinus. As the technology evolves and further iterations of the catheter proceed, the role for this new but well-established technology is likely to grow.

Acute and long-term outcome of transvenous cryoablation of midseptal and parahissian accessory pathways in patients at high risk of atrioventricular block during radiofrequency ablation

The ability of transvenous cryothermal catheter ablation to create reversible lesions (cryomapping) and to avoid catheter dislodgment (cryoadherence) has been shown to be safe and highly effective in elimination of atrioventricular nodal reentrant tachycardia. In addition, cryoablation may be useful in the management of perinodal accessory pathways, but its efficacy and safety in patients at high risk of atrioventricular block during radiofrequency catheter ablation is unknown. This study prospectively evaluated the efficacy and safety of cryoablation in patients with midseptal and parahissian accessory pathways.

Algorithm for differentiation of left and right posterior paraseptal accessory pathway

We studied 196 consecutive patients with posterior paraseptal accessory pathway (AP); 124 showed manifest preexcitation and 72 were concealed AP. Successful ablation was obtained from left-sided approach in 134 patients (left posterior pasaseptal [LPS] group) and from right sided approach in 62 patients (right posterior paraseptal [RPS] group). A ventriculo-atrial (VA) interval of <50 ms recorded at LPS region (VA(LPS)) during right ventricular pacing identified 95 of the 134 patients (71%) with LPS AP with 100% specificity and positive predictive value. In the 101 patients with VA(LPS) >/=50 ms, a difference in VA interval of <20 ms recorded at the His bundle region and LPS region, DeltaVA(H-LPS), during right ventricular pacing predicted RPS AP with a sensitivity of 97%, a specificity of 85% and a positive predictive value of 91%. When these 2 parameters were used together for prediction of LPS or RPS AP, the sensitivity, specificity, and positive predictive value were 96%, 97%, and 98% for LPS AP, and 97%, 96%, and 91% for RPS AP, respectively. This simple new algorithm using VA(LPS) and DeltaVA (H-LPS) during right ventricular pacing successfully discriminates LPS and RPS AP with high sensitivity, specificity, and positive predictive value and could facilitate radiofrequency ablation in patients with posterior paraseptal AP.

Successful Radiofrequency Catheter Ablation of an Anteroseptal (Superoparaseptal) Atrioventricular Accessory Pathway From the Left Ventricular Outflow Tract

This case report describes a patient with Wolff-Parkinson-White syndrome in whom the ECG exhibited a typical pattern of an anteroseptal (superoparaseptal) accessory pathway. Successful radiofrequency catheter ablation was achieved from the septal side of the left ventricular outflow tract. It might be worthwhile to map the left side of the anterior septum if an accessory pathway potential is not appreciable along the tricuspid annulus to avoid the potential complication of AV block in patients with a typical anteroseptal accessory pathway ECG pattern.

Radiofrequency catheter ablation of septal accessory pathways in the pediatric age group

Radiofrequency catheter ablation (RCA) of septal accessory pathways may be technically challenging in children due to the risk of inadvertent atrioventricular (AV) block in the setting of small cardiac dimensions. Outcomes were reviewed for all patients aged < or =19 years with manifest and concealed septal accessory pathways undergoing RCA since 1990 at a single institution. One hundred forty-five procedures were performed in 127 patients (mean age 11.6 years). The number of studies according to accessory pathway location were: anteroseptal (n = 36), midseptal (n = 20), mouth of coronary sinus (n = 40), middle cardiac vein (n = 6), right posteroseptal (n = 21), and left posteroseptal (n = 22). Ablation was deferred for 9 patients (6 anteroseptal and 3 midseptal) in favor of additional pharmacologic trials. Acute success rates for targeted accessory pathways were: anteroseptal (96%), midseptal (94%), mouth of coronary sinus (88%), middle cardiac vein (100%), right posteroseptal (100%), and left posteroseptal (96%). Recurrence rates during follow-up were: anteroseptal (14%), midseptal (12%), mouth of coronary sinus (3%), right posteroseptal (4%), and left posteroseptal (4%). Permanent second or third degree AV block occurred in 4 of 136 RCA attempts (3%), involving 2 anteroseptal and 2 midseptal pathways. In 3 of these 4 cases, a high probability of block was anticipated from prior ablation efforts, prompting pacemaker insertion before or in conjunction with RCA. Thus, in the pediatric age group, acute RCA success rates for septal accessory pathways can exceed 90%. The risks of AV block and accessory pathway recurrence are most relevant to anteroseptal and midseptal pathways. These data may be factored into patient selection and the decision whether to ablate.

Safety and efficacy of cryoablation of accessory pathways adjacent to the normal conduction system

Cryoablation of Septal Accessory Pathways.

INTRODUCTION

Catheter ablation has become a routine treatment for patients with Wolff-Parkinson-White syndrome because of its low risk and high efficacy; however, radiofrequency ablation in the septum close to the AV node or His bundle still carries a definite risk for AV block. Cryoenergy catheter ablation has recently become available. This technique has specific features, such as the ability to create reversible loss of function to predict the effects of ablation (ice mapping) and the adherence of the catheter tip to the endocardium with freezing, which avoids the risk for dislodgment. Both of these characteristics may minimize the risk of complications. The aim of this study was to analyze the effectiveness and safety of catheter cryoablation in 20 patients with para-Hisian or midseptal accessory pathways (AP).

METHODS AND RESULTS

Eleven patients with para-Hisian and 9 patients with midseptal AP underwent catheter cryoablation. Ice mapping at -30 degrees C was performed to ascertain the disappearance of AP conduction and the absence of impairment of AV nodal conduction. If the expected result was obtained, cryoablation was performed by lowering the temperature to -75 degrees C for 4 minutes in order to create a permanent lesion. Cryoablation was successful in all patients using a mean of 1.2 +/- 0.4 applications. Recurrences occurred in 4 patients (20%) who underwent a second successful cryoablation session. No complications were observed.

CONCLUSION

Cryoablation appears to be a safe and effective technique for ablation of APs close to the AV node or His bundle because of the ability to predict the acute effects of ablation with ice mapping before creation of an irreversible lesion.

Successful ablation of Hisian ectopy identified by a reversed His bundle activation sequence

Junctional ectopy or tachycardia have been mapped and ablated in the atrioventricular node or its posterior extensions. There is no report of Hisian ectopy convincingly demonstrated and then successfully treated by ablation. A 39-year-old man presented with a 9-year history of recurrent supraventricular ectopy refractory to medical treatment. Intracardiac mapping revealed that the ectopy originated from the His bundle, which was indicated by a reversed His bundle activation sequence during ectopy compared to that during sinus rhythm, while the right bundle branch potential was anterogradely activated. Low power RF energy delivered to the site of earliest activation completely abolished the ectopic activity without modification of Hisian or atrioventricular conduction. After a 12-month followup, the patient remains free of recurrence.

Ablation of atrial tachycardia originating from the vicinity of the atrioventricular node: significance of mapping both sides of the interatrial septum

OBJECTIVES

The purpose of the study was to examine the value of right- and left-sided mapping to identify the site of tachycardia origin.

BACKGROUND

Focal atrial tachycardia may originate from the vicinity of the atrioventricular node from either side of the interatrial septum.

METHODS

In 16 patients undergoing radiofrequency catheter ablation of perinodal atrial tachycardia, activation mapping of the right and left side of the interatrial septum was performed.

RESULTS

Atrial tachycardia originated from the right side of the interatrial septum in 10 patients (group A) and from the left side in 6 patients (group B). On the right side, earliest atrial activity preceded the onset of the P-wave by 49 +/- 15 ms in group A and by 38 +/- 8 ms in group B (NS), and it preceded the signal recorded from the right atrial appendage by 59 +/- 19 ms in group A and by 60 +/- 13 ms in group B (NS). On the left side, earliest activity preceded the onset of the P-wave by 27 +/- 16 ms in group A and by 51 +/- 6 ms in group B (<0.01), and it preceded the signal obtained from the right atrial appendage by 38 +/- 19 ms in group A and by 73 +/- 9 ms in group B (<0.01). Atrial tachycardias were successfully eliminated in all patients without impairment of atrioventricular conduction. During follow-up, two patients had a recurrence of tachycardia.

CONCLUSIONS

Mapping of only the right side cannot exclude a left-sided origin. Therefore, mapping of both sides of the interatrial septum is required prior to ablation of focal atrial tachycardia originating from the vicinity of the atrioventricular node.

Unusual features of intermediate septal bypass tracts

INTRODUCTION

Intermediate septal (IS) AV bypass tracts, located along the tricuspid annulus between the His bundle and coronary sinus os, lie in close proximity to the AV node. Surgical or catheter ablation of IS bypass tracts incurs increased risk for development of complete heart block. We report additional unusual features of some IS bypass tracts that distinguish them from typical bypass tracts in other anatomic regions.

METHODS AND RESULTS

We analyzed a consecutive series of 150 patients with a history of Wolff-Parkinson-White syndrome and supraventricular tachycardia who underwent ablation of bypass tracts. We studied the incidence and characteristics of AV conduction of IS bypass tracts compared with bypass tracts in other locations. Of the 150 patients in the study, 21 had an IS bypass tract (all had anterograde AV conduction). Ten (48%) of these 21 IS bypass tracts demonstrated anterograde decremental properties with atrial pacing versus 3 (2%) of 129 non-IS bypass tracts (P < 0.001). During ablation, a change in delta wave morphology before total loss of conduction in the IS bypass tract also occurred in 3 (14%) of 21 IS bypass tracts versus 0 of 129 non-IS bypass tracts (P = 0.0004). During ablation, a change in P wave to delta wave interval occurred in 4 (19%) of 21 IS bypass tracts versus 0 of 129 non-IS bypass tracts (P < 0.0001). One IS patient exhibited retrograde Wenckebach block in the bypass tract, and two IS patients showed loss of retrograde bypass tract conduction after ablation attempts that first changed the delta wave morphology. No non-IS patient had these features (P < 0.0001 for each comparison).

CONCLUSION

Some IS bypass tracts have unusual properties that distinguish them from bypass tracts in other locations, perhaps due to the presence of multiple ventricular insertions of the bypass tract. It is possible that some cases represent true "nodoventricular" pathways.

Parahisian radiofrequency catheter ablation in dogs: comparison of the above-valve and below-valve approaches

In patients with an accessory pathway close to the His bundle, radiofrequency catheter ablation (RFCA) requires additional care to avoid damage to the normal conduction system. To assess differences between approaches from above or below the tricuspid valve (TV), we performed RFCA in 20 dogs (from above, group A, n=10; from below, group B, n=10). RF energy with temperature control at 60 degrees 60 seconds was administered at the site where a small His potential was recorded from the ablation catheter guided by fluoroscopy and transesophageal echocardiography (TEE) (in the latter six dogs). Before and after RFCA, electrophysiological testing was performed and histological findings were compared. An ablated lesion was created in 7 of 10 (2 of 2 guided by TEE) dogs in group A and 5 of 10 (3 of 4 TEE) dogs in group B. In group A, an ablated lesion involved the atrium and ventricle in the anterior site of His bundle, but the lesion was only in the ventricle in group B. An atrioventricular block (AVB) and severe damage to the penetrating bundle was observed in one dog of group A. A large hematoma on the TV was made in 2 dogs and the complete right bundle branch block (CRBBB) occurred in 3 dogs of group B. The approach from below the TV was safer than that from above the TV in parahisian RFCA, because it did not create an AVB, although it has a high incidence of CRBBB and associated technical difficulties.

Characteristics and radiofrequency catheter ablation of septal accessory atrioventricular pathways

Septal accessory AV pathways are located in the complex AV septal space that also contains the specialized conduction system. They have unique electrocardiographical and electrophysiological characteristics to be differentiated from free-wall accessory pathways. Some of the septal pathways have AV nodelike conduction properties and produce a similar activation sequence in the retrograde conduction. Several methods have been developed to distinguish them from AV nodal pathways. Radiofrequency catheter ablation using the titration method and endocardial approach without entrance into the coronary sinus is effective in eliminating most of the septal accessory pathways without impairment of AV conduction. However, some posteroseptal accessory pathways may require energy application inside the coronary sinus, thus information of the coronary sinus anatomy is important for preventing complication.

Radiofrequency catheter ablation of septal accessory pathways within the triangle of Koch: importance of energy titration testing other than the local electrogram characteristics for identifying the successful target site

Radiofrequency (RF) catheter ablation of accessory atrioventricular (AV) connections in the proximity of His bundle or AV node is at high risk of developing complete heart block. A safe and effective protocol has not been well established. Nineteen consecutive patients with 19 septal accessory pathways within the triangle of Koch underwent a protocol with power-titrated RF energy testing to identify the target site for successful catheter ablation. At every potential target site preselected by local electrogram characteristics, RF energy was started at 5 W for 10 seconds, with an increment of 5 W (duration remained at 10 s) until maximally 30 W or the observation of transient interruption of accessory pathway conduction. By this stepwise RF energy testing, we successfully localized and ablated 18 (94.7%) of the 19 septal accessory pathways, 10 close to His bundle (zone I) and 8 away from it (zone II). The test-effective RF power was 20 W or less in 9 of all 11 septal accessory pathways in zone I, and 5 of the 8 in zone II (P = 0.68). Meanwhile, the final RF power for successful ablation was 30 W or less in 9 of the 10 zone I and 6 of the 8 zone II septal accessory pathways (P = 0.83). One patient with an accessory pathway in zone I was complicated with complete AV block after final ablation at 30 W. None of the local electrogram characteristics except continuous electrical activity during retrograde mapping was helpful in the prediction of ablation outcome. Careful RF energy titration testing could effectively help identify the target site for successful RF catheter ablation of septal accessory pathways within the triangle of Koch. The dependence on local electrogram manifestations could be frustrated by a low probability of success.

Interlesion dependence of the risk for restenosis in patients with coronary stent placement in in multiple lesions

BACKGROUND

Little is known about the behavior with regard to restenosis of multiple lesions within the same patient treated with intracoronary stenting. Our objective was to test the hypothesis that there is an intrapatient dependence of restenosis between lesions.

METHODS AND RESULTS

Quantitative analysis was carried out on angiograms obtained before, immediately after, and at 6 months after coronary stent placement in 1734 lesions in 1244 patients. We used a specialized logistic regression that not only accounts for intraclass correlation but also quantifies it in the form of odds ratio (OR) as the change in risk of a lesion to develop restenosis if another companion lesion had restenosis. The model was based on 23 patient- and lesion-related variables with binary restenosis (diameter stenosis > or =50%) as end point. The overall restenosis rate was 27.5%: 24.4% for single-lesion, 28.6% for double-lesion, and 33.8% for > or =3-lesion interventions. After adjustment for the influence of significant factors (hypercholesterolemia, systemic arterial hypertension, diabetes mellitus, previous PTCA, ostial lesion, location in left anterior descending coronary artery, number of stents placed, vessel size, stenosis severity, balloon-to-vessel ratio, and final result), the analysis found a significant intrapatient correlation, OR 2.5 (1.8 to 3.6). This means that in patients with multilesion interventions, the risk of a lesion to develop restenosis is 2.5 times higher if a companion lesion has restenosis, independently of the presence or absence of analyzed patient risk factors (eg, diabetes).

CONCLUSIONS

This study demonstrates that there is a dependence of restenosis between coronary lesions in patients who undergo a multilesion intervention. The likelihood of restenosis for a lesion is higher when another companion lesion has also developed restenosis. Other, as yet unidentified patient factors may be the source of this intrapatient correlation of restenosis.

Radiofrequency ablation of anteroseptal, para-Hisian, and mid-septal accessory pathways using a simplified femoral approach

Feasibility of RF ablation using a simplified two-catheter technique from a femoral approach was studied in 97 consecutive patients with a manifest or concealed accessory pathway located at the anteroseptal, mid-septal, and para-Hisian areas. RF was applied at the site with the shortest V-delta interval or the earliest retrograde atrial activation during orthodromic tachycardia or right ventricular pacing. Ablation was initially successful in 88 of 97 patients (91%). Success rate was 94% (16/17) for anteroseptal, 94% (39/43) for para-Hisian, and 89% (33/37) for mid-septal accessory pathways, without differences between manifest and concealed pathways for any of the locations. Mean number of RF pulses was 8 +/- 5 for anteroseptal, 6 +/- 6 for mid-septal, and 12 +/- 13 for para-Hisian accessory pathways. Two patients (2%) required implantation of a permanent pacemaker for complete AV block. At a mean follow-up of 27 +/- 14 months, four patients with previous manifest preexcitation experienced resumption of intermittent preexcitation, but only one required a second successful procedure for recurrence of palpitations. RF ablation can be used effectively and without impairment of normal AV conduction in the majority of patients with anteroseptal, para-Hisian, and mid-septal accessory pathways using a simplified two-catheter technique from a femoral approach.

Clinical, electrophysiological characteristics, and radiofrequency catheter ablation of atrial tachycardia near the apex of Koch's triangle

Atrial tachycardia, with its focus near the apex of Koch's triangle, may carry a potential risk of atrioventricular block during radiofrequency catheter ablation. The efficacy and safety of this procedure have never been addressed. The characteristics and catheter ablation results are reported for six patients with atrial tachycardia near the apex of Koch's triangle. All six patients were female aged 49.6 +/- 9.3 years (range 39-63). Organic heart disease was present in 3 (50%) of the 6 patients. The P wave in surface ECG had a mean axis of -28 degrees (range -90 degrees - +30 degrees) in the frontal plane. The catheter ablation was guided by activation sequence mapping. The energy was titrated from low power level. Atrial overdrive pacing was used to monitor the atrioventricular conduction should accelerated junctional rhythm occur. At the final successful ablation site, the local atrial activation was 41.8 +/- 9.1 ms before the P wave and His-bundle potential was present in 5 of the 6 patients. All patients had their atrial tachycardia eliminated without recurrence or heart block during a follow-up period of 17.7 +/- 8.5 months (range 6-30). In conclusion, atrial tachycardia near the apex of Koch's triangle has distinct clinical and electrophysiological features. Radiofrequency catheter ablation can be performed effectively. However, extreme care must be taken to prevent inadvertent atrioventricular block. Titrated energy application and continuous monitoring of atrioventricular conduction are mandatory.

Inadvertent atrioventricular block during radiofrequency catheter ablation. Results of the Pediatric Radiofrequency Ablation Registry. Pediatric Electrophysiology Society

BACKGROUND

Inadvertent atrioventricular block is a complication of radiofrequency ablation. The present study is an analysis of the incidence, significance, and factors associated with inadvertent atrioventricular block during radiofrequency catheter ablation in childhood and adolescence.

METHODS AND RESULTS

The records of the Pediatric Radiofrequency Ablation Registry were reviewed. Between January 1, 1991, and April 1, 1994, atrioventricular block occurred in 23 of 1964 radiofrequency ablations (1.2%): 14 as third-degree block (3 transient) and 9 as second-degree block (5 transient). Atrioventricular block occurred from 5 seconds to 2 months (mean, 4.1 days; median, 15 seconds) after the onset of the energy application. Eight transient cases lasted 1 hour to 1 month (mean, 9.4 days; median, 7 days). Inadvertent atrioventricular block was related to the ablation anatomic site: 3 of 111 (2.7%) anteroseptal, 11 of 106 (10.4%) midseptal, and 2 of 197 (1.0%) right posteroseptal sites (P = .0007) for anteroseptal, P = .0001 for midseptal, and P = .17 for right posteroseptal versus nonright septal sites). Five of 314 (1.6%) ablations for atrioventricular nodal reentrant tachycardia resulted in atrioventricular block (P = .004 versus nonright septal sites). Compared with a matched subgroup, radiofrequency ablation experience was the only significant risk factor (32.7 versus 106.6, P = .002) for the occurrence of atrioventricular block.

CONCLUSIONS

Inadvertent atrioventricular block may occur during or late after radiofrequency catheter ablation. It is associated with ablations for (1) anterior and midseptal accessory pathways and atrioventricular nodal reentry and (2) relative institutional inexperience.

Catheter-induced atrioventricular nodal block during radiofrequency ablation

This study examined the incidence and significance of catheter-induced atrioventricular nodal block (AVNB) during a radiofrequency ablation procedure that uses stiff large-tip steerable ablation catheters. AVNB was noted in 10 (1.6%) of 613 consecutive patients undergoing radiofrequency ablation therapy for atrioventricular nodal (AVN) reentrant tachycardia (592 patients) or atrioventricular reentry tachycardia incorporating a midseptal accessory pathway (21 patients). Of these 10 patients, 9 underwent AVN modification for AVN reentrant tachycardia and 1 for ablation of a midseptal accessory pathway. One patient had two episodes of AVNB during two sessions undertaken because of recurrence of tachycardia. No patient had a preexisting conduction defect before the study. In all 10 patients, AVNB was transient, and it lasted for a mean of 9.1 +/- 19 minutes. It occurred during positioning of the ablation catheter in the junctional area before (8 patients) or after (2 patients) the start of radiofrequency current applications. Complete AVNB was noted on six occasions, second-degree AVNB on four occasions, and first-degree AVNB on one occasion. All blocks were associated with narrow QRS ventricular beats and with a site of block proximal to the His bundle. The mean ventricular heart rate during AVNB was 60 +/- 23 beats/min. Two patients had transient asystole, with one having loss of consciousness. No patient required special treatment for heart block. One-to-one conduction resumed after repositioning of the catheters, and the subsequent ablation procedure was successfully completed in 8 of the 10 patients. During a follow-up of 20 +/- 12 months, none of the patients had severe dizziness or syncope, and none required implantation of a permanent pacemaker. In conclusion, transient AVNB due to mechanical injury occurs during positioning of a stiff large-tip steerable ablation catheter in the junctional area. Delivery of radiofrequency current to the site that provokes catheter-induced AVNB should be avoided.

Electrocardiographic identification of mid-septal accessory pathways in close proximity to the atrioventricular conduction system

In order to identify ECG characteristics of overt mid-septal accessory pathways (APs) predictive of close proximity to the AV conduction system we analyzed data from patients who underwent successful RF catheter ablation of a mid-septal AP. Mean patient age was 31 +/- 16 years, and 13 were male. The 40 degrees right anterior oblique view was used to divide the mid-septal area into 3 zones: 1 (anterior portion); 2 (intermediate); and 3 (posterior portion). The 12-lead ECG was analyzed with regard to delta wave polarity and R/S transition in the precordial leads. The findings from patients ablated at zone 3 were compared to those at zones 1 and 2. All patients had a positive delta wave in the leads I, II, aVL, and negative delta wave in the leads III and aVR. The R/S transition occurred in lead V2 in 80% of patients. The delta wave in lead aVF was the only ECG characteristic that correlated with the AP ablation zone. Six of 8 patients ablated at zone 3 had a negative delta wave in lead aVF while 6 out of 7 patients ablated at zone 1 or 2 had a positive or isoelectric delta wave in lead aVF (P = 0.03). A positive or isoelectric delta wave in lead aVF identifies mid-septal AP in close proximity to the AV conduction system.

Radiofrequency ablation therapy of the posteroseptal accessory pathway

Among 652 patients with Wolff-Parkinson-White syndrome who underwent radiofrequency ablation in this laboratory, 139 (21%) were found to have a total of 146 posteroseptal accessory pathways. Ablation was conducted by the regular transvenous or transaortic approach; ablation from cardiac venous structures was used only if regular approaches were unsuccessful. Of the 146 posteroseptal accessory pathways, 94 were successfully ablated from the left posteroseptal region and 45 from the right posteroseptal region. In 3, successful ablation of the accessory pathway required delivery of the current to the proximal coronary sinus, and in 1 it required delivery of the current to both the atrial and ventricular aspects of the tricuspid valve at the right posteroseptum. Thus, the accessory pathway was successfully ablated in 143 (98%) of 146 instances or in 136 (98%) patients. In 3 patients, ablation was unsuccessful despite delivery of current to the left posteroseptum, the right posteroseptum, the proximal coronary sinus, and the middle cardiac vein. Seventy-seven (57%) patients with an initial success, including 9 patients with resumed preexcitation or recurrence of paipitations, underwent a follow-up electro-physiologic study 90 +/- 72 days after ablation. Of these 9 patients, the initial successful ablation site was the right posteroseptum in 7 and the left posteroseptum in 2. The accessory pathways were ablated successfully by subsequent trials in 8 patients, whereas in 1 the accessory pathway was severely damaged. Thus radiofrequency ablation of posteroseptal accessory pathways can be achieved by the regular transvenous or transaortic approach; delivery of current to the coronary sinus or middle cardiac vein is unnecessary in most patients.

Insights into the electrophysiology of accessory pathway-mediated arrhythmias provided by the catheter ablation experience: "learning while burning, part III"

The success of catheter ablation has greatly improved the care of patients with paroxysmal tachycardias and has caused a revolution in the practice of electrophysiology. Some investigators have expressed that concern over procedural success in an increasingly interventional specialty threatens to eclipse attempts to understand the physiology of arrhythmia syndromes. Alternatively, due to the precise and directed nature of the lesions created with radiofrequency energy, catheter ablation procedures have allowed investigation to continue at a more focused level. In this article, the insights provided by the catheter ablation experience into the physiology of arrhythmias mediated by accessory AV pathways will be reviewed. Although the learning process was sometimes delayed by the nearly immediate success of radiofrequency catheter ablation, difficult situations have continued to renew efforts for understanding at a deeper level. Conscious attempts at "learning while burning" will provide the opportunity to investigate aspects of bypass tract physiology that remain incompletely characterized, such as partial response to therapy and late recurrence.

Radiofrequency ablation for supraventricular and ventricular tachycardia in young patients

Radiofrequency ablation therapy was conducted in 86 consecutive children and young patients with a mean age of 14 +/- 3 years (range = 3-18). Fifty-two patients had Wolff-Parkinson-White syndrome, one had re-entry tachycardia incorporating a nodoventricular fiber, 22 had atrioventricular node re-entry tachycardia, two had atrial tachycardia and nine had idiopathic ventricular tachycardia. Radiofrequency ablation was successful in 50 of the 52 patients (96%) with Wolff-Parkinson-White syndrome and the one with nodoventricular fiber. Radiofrequency modification of the atrioventricular node using the inferior approach was successful in eliminating atrioventricular node re-entry tachycardia in 20 of the 22 patients (91%). Radiofrequency ablation in the two patients with atrial tachycardia was unsuccessful. Of the nine patients with idiopathic ventricular tachycardia, eight from the left ventricle and one from the right ventricular outflow tract, eight were successfully ablated (88%). Follow-up over a period ranging from 1 to 46 months (21 +/- 13) revealed a recurrence of tachycardia in seven patients; a late electrophysiological study in 38 patients revealed the induction of tachycardia in 11 patients (seven with accessory pathway-mediated tachycardia, three with atrioventricular node re-entry tachycardia and one with idiopathic ventricular tachycardia). All 11 patients were successfully ablated by a second trial. In conclusion, radiofrequency ablation therapy is effective and safe in pediatric patients with supraventricular and ventricular tachycardia and should be considered as the therapy of choice in this group of patients.

Electrocardiographic and electrophysiologic characteristics of anteroseptal, midseptal, and para-Hisian accessory pathways. Implication for radiofrequency catheter ablation

STUDY OBJECTIVE

To investigate the ECG characteristics, the electrophysiologic properties, and an effective radiofrequency catheter ablation technique in patients with septal accessory pathways.

PATIENTS

Forty-six consecutive subjects with septal accessory pathways located in the anteroseptal, midseptal, and para-Hisian areas.

DESIGN AND INTERVENTIONS

ECGs obtained during sinus rhythm and orthodromic tachycardia, conduction properties obtained from electrophysiologic study, and results of two different ablation techniques were analyzed.

MEASUREMENTS AND RESULTS

(1) Twenty-four (52.2%) had manifest preexcitation and 15 (32.6%) had multiple accessory pathways; (2) midseptal pathways could be differentiated from anteroseptal and para-Hisian pathways by a negative delta wave in lead III and a biphasic delta wave in lead aVF during sinus rhythm, and a negative retrograde P wave in two inferior leads during orthodromic tachycardia; (2) midseptal pathways had better antegrade conduction properties and a significantly higher incidence (61.5%) of inducible atrial fibrillation; (4) radiofrequency catheter ablation using lower energy (20+/-6 W) had a comparable effect to ablation using higher energy (36+/-5 W), but without impairment of atrioventricular (AV) node conduction or development of AV block; and (5) during the follow-up period of 26+/-14 months (range, 5 to 54 months), three (6.5%) patients had recurrence.

CONCLUSIONS

Midseptal accessory pathways had ECG and electrophysiologic characteristics that were distinctive from those of anteroseptal and para-Hisian pathways. Catheter ablation of these septal pathways using low radiofrequency energy was safe and effective.

Comparative validation of quantitative coronary angiography systems. Results and implications from a multicenter study using a standardized approach

BACKGROUND

Computerized quantitative coronary angiography (QCA) has fundamentally altered our approach to the assessment of coronary interventional techniques and strategies aimed at the prevention of recurrence and progression of stenosis. It is essential, therefore, that the performance of QCA systems, upon which much of our scientific understanding has become integrally dependent, is evaluated in an objective and uniform manner.

METHODS AND RESULTS

We validated 10 QCA systems at core laboratories in North America and Europe. Cine films were made of phantom stenoses of known diameter (0.5 to 1.9 mm) under four experimental conditions: in vivo (coronary arteries of pigs) calibrated at the isocenter or by use of the catheter as a scaling device and in vitro with 50% contrast and 100% contrast. The cine films were analyzed by each automated QCA system without observer interaction. Accuracy and precision were taken as the mean and SD of the signed differences between the phantom stenoses, and the measured minimal luminal diameters and the correlation coefficient (r), the SEE, the y intercept, and the slope were derived by their linear regression. Performance of the 10 QCA systems ranged widely: accuracy, +0.07 to +0.31 mm; precision, +/- 0.14 to +/- 0.24 mm; correlation (r), .96 to .89; SEE, +/- 0.11 to +/- 0.16 mm; intercept, +0.08 to +0.31 mm; and slope, 0.86 to 0.64.

CONCLUSIONS

There is a marked variability in performance between systems when assessed over the range of 0.5 to 1.9 mm. The range of accuracy, intercept, and slope values of this report indicates that absolute measurements of luminal diameter from different multicenter angiographic trials may not be directly comparable and additionally suggests that such absolute measurements may not be directly applicable to clinical practice using an on-line QCA system with a different edge detection algorithm. Power calculations and study design of angiographic trials should be adjusted for the precision of the QCA system used to avoid the risk of failing to detect small differences in patient populations. This study may guide the fine-tuning of algorithms incorporated within each system and facilitate the maintenance of high standards of QCA for scientific studies.

Electrocardiographic characteristics and catheter ablation of parahissian accessory pathways

BACKGROUND

Accessory pathways may be located in close proximity to the His bundle, resulting in a high risk of heart block during attempted surgical or electrical interruption of these pathways. This study reports the prevalence, ECG characteristics, and results of catheter ablation of parahissian accessory pathways. They were defined on the basis of both the presence of a high amplitude (> 0.1 mV) of His bundle potential at the ablation site and an exclusion of anteroseptal or midseptal location of the accessory pathway.

METHODS AND RESULTS

Eight patients with a parahissian accessory pathway were identified among 582 consecutive patients who underwent radiofrequency ablation of an accessory pathway. They were six males and two females with a mean age of 21 +/- 9 years. During maximal preexcitation, the ECG showed a positive delta wave in leads I, II, and a VF in all patients: six had a negative delta wave in leads V1 and V2 instead of the positivity usually observed in anteroseptal accessory pathways. This pattern had a sensitivity of 75%, a specificity of 96%, a positive predictive value of 86%, and a negative predictive value of 93% for a parahissian location in comparison with a group of 28 patients with anteroseptal accessory pathways. At the successful ablation site, the mean amplitude of the His bundle potential was 0.2 +/- 0.1 (0.12 to 0.4 mV). All accessory pathways were successfully ablated without causing heart block using 5 to 20 W of radiofrequency energy.

CONCLUSIONS

Parahissian accessory pathways have a preexcitation pattern that is distinctive from that of anteroseptal accessory pathways. Catheter ablation of these pathways is feasible using low energy with preservation of normal atrioventricular conduction.

Late clinical and electrophysiologic outcome of radiofrequency ablation therapy by the inferior approach in atrioventricular node reentry tachycardia

A late electrophysiologic study was conducted in 182 of 289 patients with slow-fast atrioventricular node reentry tachycardia 81 +/- 36 days after radiofrequency ablation therapy by the inferior approach. Of these 182 patients, electrophysiologic study immediately after ablation revealed a selective modification of the slow pathway in 159, a modification of both the slow and fast pathways in 15, a modification of the fast pathway alone in 3, and failure of ablation in 5. One hundred two patients had no induction of echoes; 75 had induction of fewer than four echoes; and 5 had induction of sustained tachycardia with or without isoproterenol infusion. The late electrophysiologic study in these 182 patients revealed a persistent effect without changes in conduction properties in 161 (88%) patients. A change in conduction properties was noted in 21 patients, including 5 with resumption of slow- or fast-pathway conduction with induction of sustained tachycardia, 8 with improved fast- or slow-pathway conduction, and 8 with an additional depression of fast- or slow-pathway conduction. Of the 102 patients with no induction of echoes and the 75 patients with induction of fewer than four echoes during the immediate postablation electrophysiologic study, 5 (3 and 2, respectively) patients had induction of tachycardia. Of the 5 patients with induction of sustained tachycardia in the immediate postablation electrophysiologic study, 3 continued to have induction of sustained tachycardia; 1 had induction of echoes only; and 1 had no induction of echoes.(ABSTRACT TRUNCATED AT 250 WORDS)