Electrogram patterns predictive of successful catheter ablation of accessory pathways. Value of unipolar recording mode

Is this an anteroseptal accessory pathway?

The ECG of a patient during sinus rhythm shows preexcited QRS pattern, with rS pattern in lead V1, transition in lead V2, and positive inferior leads. Following the stepwise algorithms, the location of accessory pathway (AP) was identified at anteroseptal region. However, the precordial transition in lead V2 indicates mid-septal or posteroseptal AP. The mismatch suggested multiple APs and 5 APs were identified by electrophysiologic study. This case highlights the importance of detailed analysis of ECG in order to achieve adequate ablation.

Incremental benefit of a novel signal recording system during mapping and ablation

AIMS

Current electrophysiology signal recording and mapping systems have limited dynamic range (DR) and bandwidth, which causes loss of valuable information during acquisition of cardiac signals. We evaluated a novel advanced signal processing platform with the objective to obtain and assess additional information of clinical importance.

METHODS AND RESULTS

Over 10 canines, we compared intracardiac recordings within all cardiac chambers, in various rhythms, in pacing and during radiofrequency (RF) ablation across two platforms; a conventional system and the PURE EP™ [(PEP); Bio Sig Technologies, Inc., Los Angeles, CA, USA]. Recording cardiac signals with varying amplitudes were consistently and reproducibly observed, without loss of detail or introduction of artefact. Further the amplitude of current of injury (COI) on the unipolar signals correlated with the instantaneous contact force (CF) recorded on the sensing catheter in all the animals (r2 = 0.94 in ventricle). The maximum change in the unipolar COI correlated with the change in local electrogram amplitude during non-irrigated RF ablation (r2 = 0.61 in atrium). Reduction in artefact attributable to pacing (20 sites) and noise during ablation (48 sites) was present on the PEP system. Within the PEP system, simultaneous display of identical signals, filtered differently, aided the visualization of discrete conduction tissue signals.

CONCLUSION

Compared to current system, the PEP system provided incremental information including identifying conduction tissue signals, estimates of CF and a surrogate for lesion formation. This novel signal processing platform with increased DR and minimal front-end filtering may be useful in clinical practice.

Left-sided accessory pathways successfully ablated from the aortomitral continuity region: distinctive atrial activation patterns and anatomic concerns

AIMS

Accessory pathways (APs) successfully ablated at the aortomitral continuity (AMC) were sporadically reported but relevant data are very limited. We aimed to describe the electrophysiological characteristics of AMC-AP and the related anatomy.

METHODS AND RESULTS

This study involved eight (male/female = 3/5, mean age 42.6 ± 10.5 years) patients with left-sided AP successfully ablated in the AMC region. The retrograde atrial activation sequence was analysed and compared via recordings at the His-bundle (HB), coronary sinus (CS), and roving catheter during tachycardia, and the peak of QRS from the same cardiac circle used as time reference. Of the eight patients, two received prior ablations. During tachycardia, the activation time at the proximal CS (CSp), lateral CS (CSl), and HB region averaged 120 ± 26 ms, 124 ± 29 ms, and 117 ± 21 ms following the reference, respectively (P = 0.86). The latest atrial activation was recorded in the posterior CS which averaged 135 ± 25 ms following the reference. Placing the ablation catheter to AMC via retrograde approach was attempted in all cases but stable positioning achieved in none. Via transseptal approach, the ablation catheter could be easily placed at the AMC and recorded the earliest retrograde atrial activations with 60 ± 27 ms earlier than the relatively 'earliest' CS/HB recordings, and ablation at this site successfully eliminated AP conduction. No patients had recovered AP conduction after at least 12-month follow-up.

CONCLUSION

AMC-AP is featured by recording comparable retrograde atrial activation times at CSp, CSl, and HB with the latest recordings at the posterior CS. Stable placement and successful ablation in the AMC via retrograde aortic approach was difficult but can be achieved via transseptal approach.

The 'double transition': a novel electrocardiogram sign to discriminate posteroseptal accessory pathways ablated from the right endocardium from those requiring a left-sided or epicardial coronary venous approach

AIMS

The precise localization of manifest posteroseptal accessory pathways (APs) often poses diagnostic challenges considering that a small area may encompass AP that may be ablated from the right or left endocardium, or epicardially within the coronary sinus (CS). We sought to explore whether the QRS transition pattern in the precordial lead may help to discriminate the necessary ablation approach.

METHODS AND RESULTS

Consecutive patients who underwent a successful ablation of a single manifest AP over a 5-year period were included. Standard 12-lead electrocardiograms were reviewed. A total of 273 patients were identified. Mean age was 31 ± 15 years and 62% were male. Of the 110 identified posteroseptal AP, 64 were ablated from the right endocardium, 33 from the left endocardium, and 13 inside the CS. While a normal precordial QRS transition was most often observed, a subset of 33 patients presented an atypical 'double transition' pattern which specifically identified right endocardial AP. The combination of a q wave in V1 with a proportion of the positive QRS component in V1 < V2 > V3, predicted a right endocardial AP with a 100% specificity. In case of a positive QRS sum in V2, this 'double transition' pattern predicted a posteroseptal right endocardial AP with 99.5% specificity and 44% sensitivity. The positive predictive value was 97%. The only false positive was a midseptal AP. In the case of a negative or isoelectric QRS sum in V2, APs were located more laterally on the tricuspid annulus.

CONCLUSION

The combination of a q wave in V1 with a double QRS transition pattern in the precordial leads is highly specific of a right endocardial AP and rules out the need for CS or left-sided mapping.

Ultra-high resolution mapping and ablation of accessory pathway conduction

BACKGROUND

Detailed mapping studies of accessory pathway (AP) conduction have not been previously performed using ultra-high resolution mapping systems. We sought to evaluate the clinical utility of ultra-high resolution mapping systems and the novel "Lumipoint" algorithm in AP ablation.

METHODS

This study included 17 patients who underwent AP mapping using minielectrode basket catheters and Rhythmia systems. Ablation was performed with 4-mm irrigated-tip catheters.

RESULTS

Antegrade and retrograde AP conduction was observed in 6 and 16 patients. Atrial activation map was obtained during orthodromic tachycardia and ventricular pacing in 13 (76.5%) and 14 (82.3%) patients, and the earliest activation area was identical. Ventricular activation maps were created during atrial pacing in 3 patients. All maps showed focal activation patterns on global activation histograms, and the valley on the histogram highlighted the earliest activation area. "Complex activation" features further highlighted limited areas with continuous electrical activity during the time period in the majority. APs were located at the mitral and tricuspid annuli in 15 and 2 patients, and all were successfully eliminated with 3.4 ± 0.6 s applications. No patients had recurrences during a median follow-up of 15 [10.5-22.5] months. At successful ablation sites, the local atrial and ventricular electrogram amplitudes and ratio tended to be greater, and fusion or continuous electrical activity between the atrial and ventricular components was more frequently observed on the minielectrode than ablation catheter (17/17 vs. 12/17, p = 0.005).

CONCLUSIONS

Ultra-high resolution activation mapping and a novel algorithm facilitated the AP localization. The local electrogram characteristics differed between the minielectrode and ablation catheters.

Fundamentals of Cardiac Mapping

To characterize cardiac activity and arrhythmias, electrophysiologists can record the electrical activity of the heart in relation to its anatomy through a process called cardiac mapping (electroanatomic mapping, EAM). A solid understanding of the basic cardiac biopotentials, called electrograms, is imperative to construct and interpret the cardiac EAM correctly. There are several mapping approaches available to the electrophysiologist, each optimized for specific arrhythmia mechanisms. This article provides an overview of the fundamentals of EAM.

Electrogram recording and analyzing techniques to optimize selection of target sites for ablation of cardiac arrhythmias

The extracellular electrogram is caused by transmembrane currents that flow into extracellular space during propagation of the electrical impulse. Electrograms are usually recorded in unipolar or bipolar mode that have different characteristics, but provide complementary information. Both recording modes have specific advantages, but also suffer from disadvantages. Techniques to circumvent some of the weaknesses are reviewed. The origin of remote and fractionated deflections and their relation with electrode characteristics are discussed. Epicardial and endocardial sites of origin and breakthrough sites as well as the effect of fatty tissue on extracellular electrograms are presented. Induction of tachycardia to assess the arrhythmogenic area is not always possible because of hemodynamic instability of the patient. Techniques to assess sites with high reentry vulnerability without induction of arrhythmias are outlined such as activation‐repolarization mapping and decremental stimulation. Pitfalls of substrate mapping and techniques to avoid them as omnipolar mapping and characterization of complex electrograms by entropy are presented. Technical aspects that influence electrogram morphology as electrode size, filtering, contact force, and catheter position are delineated. Data from the various publications suggest that a combination of unipolar and bipolar electrogram analysis techniques is helpful to optimize determination of target sites for ablation.

Right free-wall accessory pathway with branched atrial insertions: Clinical, electrocardiographic, and electrophysiological characteristics

BACKGROUND

Right free-wall (RFW) accessory pathway (AP) with branched atrial insertions is a rare, underrecognized AP that may be associated with initial ablation failure.

OBJECTIVE

The purpose of this study was to investigate the clinical and electrophysiological characteristics of this AP.

METHODS

From January 2011 to March 2018, 10 patients identified with branched RFW-AP were enrolled in this study, and 30 consecutive patients with conventional RFW-APs served as control group. Right atrium (RA) was activation-mapped and 3-dimensionally reconstructed during AP-mediated orthodromic tachycardia or right ventricular pacing. Atrial insertions were defined as the earliest breakout sites, and their relationship with the tricuspid annulus (TA) were described and analyzed.

RESULTS

An average of 3 separate atrial insertions on the atrial side were documented among these 10 cases (5 female and 5 male; mean age 38.0 ± 13.9 years). All atrial insertions were away from the TA. The nearest atrial insertions averaged 15.9 ± 3.4 mm away from the TA, and the farthest atrial insertions were 22.6 ± 5.7 mm away from the TA. Anterograde and retrograde AP conduction remained unaffected after ablation of the first earliest breakout site but were eliminated by ablating all insertions after an average of 2.5 (range 2-2.5) remaps, 3 sites of ablation (range 2.5-4.5), 21 (range 15.5-37.8) radiofrequency applications, and 659.5 (range 464.3-1144.3) seconds of radiofrequency ablation duration. After 12-month follow-up, no patients reported AP conduction recovery or recurrent tachycardia.

CONCLUSION

RFW-AP with branched atrial insertions is an atypical AP variant and featured by >1 distinct atrial insertions on atrial side. Stepwise ablation rather than single focal ablation is required to eliminate all retrograde conduction.

Three-dimensional myocardial scar characterization from the endocardium: Usefulness of endocardial unipolar electroanatomic mapping

Epicardial ablation may be required to eliminate ventricular tachycardia (VT) in patients with underlying structural heart disease. The decision to gain epicardial access is frequently based on the suspicion of an epicardial origin for the VT and/or presence of an arrhythmogenic substrate. Epicardial pathology and VT is frequently present in patients with nonischemic right and/or left cardiomyopathies even in the setting of modest or no endocardial bipolar voltage substrate. In this setting, unipolar voltage mapping from the endocardium serves to help identify midmyocardial and/or epicardial VT substrate. The additional value of endocardial unipolar mapping includes its usefulness to predict the clinical outcome after VT ablation, to determine the irreversibility of myocardial disease, and to guide endomyocardial biopsy procedures to specific areas of intramural scarring. In this review, we aim to provide a guide to the use of endocardial unipolar mapping and its appropriate interpretation in a variety of clinical situations.

Predictive value of unipolar and bipolar electrograms in idiopathic outflow tract ventricular arrhythmia mapping and ablation

INTRODUCTION

Radiofrequency catheter ablation is an effective therapy for focal idiopathic outflow tract ventricular arrhythmia (OTVA). However, visual inspection of the unipolar electrogram (EGM) QS morphology is subjective with a poor specificity for predicting successful ablation sites. This study aims to evaluate the predictive value of unipolar and bipolar EGMs in OTVA mapping and ablation.

METHODS AND RESULTS

Twenty-two patients scheduled for idiopathic OTVA ablation were prospectively enrolled. During the procedure, unipolar and bipolar EGMs were recorded simultaneously and visually inspected by the operator to identify their values for predicting arrhythmogenic sites. Quantitative features of the unipolar EGM including the ratio of amplitude of the first positive peak versus the nadir (R-ratio), the maximum descending slope (MaxSlope), and the time interval between the initial deflection point to the MaxSlope (D-Max) were calculated for each target site in offline analysis. EGMs from 100 sites were collected in 20 patients and analyzed. The bipolar reverse polarity characteristic was not as practical for identifying successful ablation site as the unipolar QS characteristic. Successful ablation sites demonstrated smaller R-ratio and shorter D-Max than unsuccessful sites, but no significant difference in MaxSlope. A unipolar EGM-derived quantitative criterion provided significantly better specificity (0.70) than visual inspection (0.37) without compromising on the sensitivity (0.83 vs. 0.89).

CONCLUSION

The bipolar reverse polarity characteristic was not a practical method for identifying target in idiopathic OTVA ablation. The unipolar EGM-derived quantitative criteria have better predictive performance than visual inspection of the QS characteristic and are likely to reduce unnecessary ablation sites.

Local Atrial/Ventricular Ratio as an Adjuvant Marker for Catheter Ablation of Atrioventricular Accessory Pathways

Background and Objectives

The earliest atrial (A)/ventricular (V) activation potential, or accessory pathway (AP) potential are commonly used as ablation targets for atrioventricular (AV) APs. However, these targets are sometimes ambiguous.

Subjects and Methods

We reviewed 119 catheter ablation cases in 112 patients diagnosed with orthodromic atrioventricular reentrant tachycardia (AVRT) or Wolff-Parkinson-White (WPW) syndrome. Local A/V amplitude potentials with the earliest activation or AP potential were measured shortly before achieving antegrade AP conduction block, ventriculoatrial block during right ventricle (RV) pacing, or AVRT termination with no AP conduction.

Results

APs were located in the left lateral (55.5%), left posterior (17.6%), left posteroseptal (10.1%), midseptal (1.7%), right posteroseptal (7.6%), right posterior (1.7%), and right lateral (5.9%) regions. The mean earliest activation time was 16.7±15.5 ms, mean A/V potential was 1.1±0.9/1.0±0.9 mV, and mean A/V ratio was 1.7±2.0. There was no statistically significant difference between the activation methods (antegrade vs. RV pacing vs. orthodromic AVRT) or AP locations (left vs. right atrium). However, when the local A/V ratio was divided into 3 groups (≤0.6, 1.0±0.3, and ≥1.4), the antegrade approach resulted in an A/V ratio greater than 1.0±0.3 (86.7%, p=0.007), and the orthodromic AVRT state resulted in a ratio of less than 1.0±0.3 (87.5%, p<0.001).

Conclusion

The mean local A/V potential and ratio did not differ by activation method or AP location. However, a different A/V ratio based on activation method (≥1.0±0.3, antegrade approach; and ≤1.0±0.3, orthodromic AVRT state) could be a good adjuvant marker for targeting AV APs.

Non-contact mapping system accurately localizes right-sided accessory pathways in type B Wolff-Parkinson-White syndrome

AIMS

Ablation of right-sided accessory pathways (APs) is sometimes challenging because several anatomical features of the tricuspid annulus (TA) and surrounding structures differ from those of the mitral annulus. This study investigated the electrophysiological characteristics and efficacy of a non-contact mapping (NCM) system for catheter ablation of right-sided APs.

METHODS AND RESULTS

We examined nine APs in six consecutive patients who underwent catheter ablation of right-sided APs with NCM. In Case 6, we compared NCM with contact activation mapping. Three of six patients had two APs, and one of these had previously failed ablation. We observed atrial activation during sinus rhythm or atrial pacing using a multiple-electrode array (MEA) deployed in the right atrium near the TA. Non-contact mapping identified the AP location as a peri-TA breakout point that appeared prior to or simultaneously with the delta wave onset in all APs. In Case 6 we confirmed that the peri-TA breakout identified by NCM corresponded to the earliest ventricular activation identified by contact mapping. We successfully ablated nine APs by radiofrequency (RF) energy application to the breakout sites, while one AP located just above the pole of the MEA required additional conventionally guided mapping and ablation. The mean RF duration was 189.8 ± 119.0 s. After 33.2 ± 9.4 months of follow-up, one para-hisian AP and one right lateral AP recurred, but these were successfully ablated in a second procedure using NCM.

CONCLUSION

Non-contact mapping was able to identify the location of right-sided APs accurately and quickly.

Correlative anatomy for the invasive electrophysiologist: outflow tract and supravalvar arrhythmia

Radiofrequency ablation in the outflow tract and great arteries is increasingly performed to treat a variety of symptomatic cardiac arrhythmias. The regional anatomy of these structures is among the most complex of those encountered by cardiac electrophysiologists. An exact appreciation of the relationships between these overlapping structures and their proximity to the coronary arterial and conduction system is essential for rational, safe, and effective ablation for these arrhythmias. A supravalvar portion of the aorta is a unique site for arrhythmia origin where the arrhythmogenic substrate for atrial arrhythmias, ventricular arrhythmias, and accessory pathways may all be located. Discussed in this review are the main principles of outflow tract and supravalvar arrhythmia, and these are correlated with fluoroscopy, electrograms, and electrocardiography that help guide the invasive electrophysiologist.

New access for radiofrequency catheter ablation of left-sided atrioventricular accessory pathways: safety and efficacy of the transradial approach

BACKGROUND

The safety and efficacy of the transradial approach for radiofrequency catheter ablation (RFCA) of left-sided atrioventricular accessory pathways (APs) was evaluated in the present study.

METHODS AND RESULTS

Included were 40 consecutive patients with type A Wolff-Parkinson-White (WPW) syndrome who underwent RFCA via the radial artery route, and 30 patients with type A WPW syndrome who underwent RFCA via the transfemoral approach (controls) were retrospectively chosen for control. All 45 APs in the 40 patients were successfully ablated: 35 APs were successfully blocked with 1 ablation attempt, and the other 10 APs were ablated after 2-4 attempts. Compared with the transfemoral approach, the total procedure time for the transradial approach was longer (40 +/- 7.7 vs 32.4 +/- 8.7 min, P<0.05) and the fluoroscopic time was similar (7.2 +/- 2.2 vs 7.9 +/- 3.9 min, P>0.05). There were no vascular complications in the transradial group, but 2 patients in the transfemoral developed local hematoma. There was no recurrence of arrhythmia in either group.

CONCLUSIONS

The transradial approach is a safe and effective access for RFCA of left-sided APs.

Clinical importance of Koch's triangle size in children: a study using 3-dimensional electroanatomical mapping

BACKGROUND

Catheter ablation inside the Koch's triangle has a risk for complete atrioventricular block.

METHODS AND RESULTS

The anatomic size of the coronary sinus (CS) and His bundle (HB) in children and the distance between them was studied using a 3-dimensional electroanatomical mapping system (CARTO). Fifty-three children (mean age, 11.8+/-3.7 years) without congenital heart disease (ie, 24 with atrioventricular re-entrant tachycardia, 18 with atrioventricular nodal re-entrant tachycardia, 7 with atrial tachycardia, 2 with ventricular tachycardia and 2 with atrial flutter) were studied. The size of the HB recording area was 148+/-97 mm2 and the size of the CS was 66+/-44 mm2. The size of the CS and the distance between the HB and CS (18+/-7 mm) were proportional to body weight, body length and body surface area. All patients underwent catheter ablation, including 25 ablations inside Koch's triangle. Catheter ablation was successful in 52 patients without any atrioventricular nodal injury.

CONCLUSIONS

The CS size and the distance between the HB and CS increased proportionally with children's growth. To know the distance from the HB to the ablation point is useful in avoiding atrioventricular node injury, and information about the length of Koch's triangle may provide supportive information when applying radiofrequency energy inside Koch's triangle without needing to use the CARTO system in children, but this merits further investigation.

Cardiac Valve Assessment with MR Imaging and 64-Section Multi–Detector Row CT

A variety of noninvasive techniques are available to assess cardiac valve morphologic features and function, with echocardiography currently being the most widely used modality for this purpose. Technical advances in electrocardiographically gated multi-detector row computed tomography (CT) and magnetic resonance (MR) imaging allow the noninvasive visualization of the cardiac valves. At present, 64-section multi-detector row CT and MR imaging are commonly being used for comprehensive examination of the heart. Information about the cardiac valves is routinely provided by MR imaging of cardiac function or coronary CT angiography. Thus, the interpreting physician may have additional information available that can aid in making the diagnosis. Supplemental movie clips are available at http://radiographics.rsnajnls.org/cgi/content/full/26/6/1769/DC1.

Progressive facilitation of antegrade conduction via an accessory pathway in a patient with Wolff-Parkinson-White syndrome and permanent atrial fibrillation

The case of a 64-year-old man with Wolff-Parkinson-White syndrome and permanent atrial fibrillation (AF) is reported. The patient was admitted due to electrocardiographic feature of AF with rapid conduction over the left-sided accessory pathway. Administration of pirmenol effectively suppressed the ventricular response via an accessory pathway. A transesophageal echocardiography detected an uncertain thrombus in the left atrial appendage. During the 33-month follow-up period, the ventricular response via an accessory pathway was progressively facilitated. Radiofrequency catheter ablation using a transseptal approach was performed during AF, resulting in complete elimination of the antegrade accessory pathway conduction.

A unipolar coronary sinus mapping study of patients with left-sided atrioventricular accessory pathways

So-called unipolar 'PQS pattern' is widely accepted as a hallmark of successful catheter ablation of the left-sided atrioventricular accessory pathway. However, the unipolar nature of the electrogram and the site-dependent appearance of this characteristic pattern are poorly understood. Therefore, unipolar coronary sinus (CS) mapping was performed using a multipolar fine electrode in patients with Wolff-Parkinson-White (WPW) syndrome associated with an antegrade left-sided accessory pathway (case group) and those with a concealed left-sided accessory pathway or atrioventricular nodal reentrant tachycardia (control group) under sinus rhythm and fixed high right atrial, CS ostial, and distal pacing. In both groups, the unipolar CS atrial electrogram showed intrinsic negative deflection (initial positive followed by negative parts) with considerable variation depending on the recording site. This unipolar configuration of the atrial electrogram was not influenced by different activation sequences during pacing at various sites. The case group exhibited a unipolar 'PQS pattern' at successful ablation sites for the left lateral to anterolateral accessory pathway. However, this was not true for the left posteroseptal accessory pathway, possibly because the negative part of the atrial electrogram distorted the 'PQS pattern' as an intervening dip. In conclusion, the site-dependent variations of the unipolar CS atrial electrogram underlie the limited usefulness of the 'PQS pattern' in left posteroseptal accessory pathway localization.

Recording Techniques for Clinical Electrophysiology

The precise techniques employed in the electrophysiology laboratory influence the nature of the electrograms that are recorded during mapping procedures. Unipolar recordings that are minimally filtered can be useful for mapping focal arrhythmia sources, but have substantial far-field signal that can obscure low-amplitude signals of interest in abnormal regions. Bipolar recordings are standard in most laboratories because rejection of far-field signal facilitates identification of local potentials in abnormal areas, but the signal of interest can be beneath either recording electrode and far-field signals do occur. Simultaneously obtained unipolar recordings are a useful adjunct to bipolar recordings in some situations. High pass filtering and digital sampling also influence electrogram characteristics. High pass filtering of unipolar recordings can be useful to reduce far-field components, but limits inferences from electrogram morphology.

Electrophysiological characteristics and radiofrequency ablation of accessory pathways with slow conductive properties

BACKGROUND

Atrioventricular accessory pathways (AP) with unusually long ventriculo-atrial (VA) conduction times are present in a significant subset of patients with the Wolff-Parkinson-White (WPW) syndrome, not including patients with the permanent form of atrioventricular junctional reciprocating tachycardia.

METHODS AND RESULTS

We compared the electrophysiological characteristics and outcomes after radiofrequency (RF) ablation in 34 patients with the WPW syndrome, a VA interval >80 ms, and paroxysmal tachycardia with an RP/PR ratio <1 (the slow group), vs 80 patients with WPW syndrome and a VA interval <80 ms (the fast group). AP were found in the posteroseptal region significantly more often in the slow than in the fast group. In addition, the decremental conductive properties of the AP were more common in the slow than in the fast group. Catheter ablation of AP was highly successful in both groups, although ablation required a greater number of RF applications and longer procedure times in the slow group, especially for AP with decremental conductive properties.

CONCLUSIONS

A posteroseptal AP location was more common in AP associated with long conduction times than in AP with typical conductive properties. Both types of AP were successfully ablated, although the slow group required longer procedures and more RF energy deliveries.

Ventricular Unipolar Potential in Radiofrequency Catheter Ablation of Idiopathic Non-Reentrant Ventricular Outflow Tachycardia

We conducted this study to verify the efficacy of ventricular unipolar potential (V-uni) for ablation of idiopathic non-reentrant ventricular tachycardia (idio-VT). The morphology of V-uni at the successful and unsuccessful sites was analyzed in 27 patients with idio-VT [20 with right ventricular outflow tachycardia (RVOVT) and 7 with left ventricular outflow tachycardia (LVOVT)]. The usefulness of V-uni was compared with a pacemapping method and the V-QRS interval. The incidence of QS-pattern V-uni at the successful and best unsuccessful sites were 100 versus 25% (P = 0.000005) in RVOVT and 86 versus 29% (P = 0.10) in LVOVT. The pacemapping scores at the successful and best unsuccessful sites were 11.5/12 versus 11.2/12; NS in RVOVT, and 11.2/12 versus 11.1/12; NS in LVOVT. The mean V-QRS interval at the successful and the best unsuccessful sites were 22.5 +/- 3.8 versus 21.6 +/- 3.4 msec; NS in RVOVT, 15.1 +/- 3.2 versus 12.5 +/- 3.3 msec; NS in LVOVT. The sensitivity (sen) and specificity (spe) of QS-pattern V-uni to determine the optimum target sites were 1.0 and 0.89 in RVOVT and 0.86 and 0.83 in LVOVT, respectively. In the ablation of idio-VT, QS-pattern V-uni is simply and visually identifiable, is very useful, and should be given a high priority when determining the optimum target site.

Transseptal activation during left atrial pacing in humans: electroanatomic mapping using a noncontact catheter and the intracardiac echocardiography

BACKGROUND

A better understanding of transseptal activation may be important for the treatment of atrial fibrillation, but little is known about preferential routes of conduction from the left atrium (LA) to the right atrium (RA) in humans.

METHODS AND RESULTS

Twelve patients were studied. A noncontact mapping system was used to map the RA during pacing from several sites of LA at different cycle lengths. The location of the Bachmann's bundle (BB), the fossa ovalis (FO) and the coronary sinus (CS) ostium were determined using intracardiac echocardiography. The BB was the earliest area of right atrial activation during pacing from the atrial appendage, roof and postero-superior wall in 94% of cases. The FO was the area of earliest activation during pacing from the septum and the right superior pulmonary veins (PV) in 95% of cases. The CS ostium (alone or associated with the FO) was the region of transseptal breakthrough in all patients during pacing from the right inferior PV, postero-inferior wall and distal CS. Various patterns of activation with 2 or 3 distinct areas of transseptal breakthrough were observed during pacing from the lateral wall and the left superior PV. The pacing cycle length did not influence the modality of transseptal activation.

CONCLUSIONS

Different patterns of transseptal activation were found during pacing from LA. The preferential routes of conduction from the LA to the RA were related to the sites of stimulation and were not influenced by the pacing cycle length.

Subthreshold stimulation in three types of reentrant supraventricular tachycardia: correlation with the results of catheter ablation

The effects of subthreshold stimulation (STS) by direct current were investigated in 20 patients with atrioventricular nodal reentrant tachycardia (AVNRT), 27 with atrioventricular reentrant tachycardia (AVRT) and 3 with idiopathic atrial reentrant tachycardia (IART) STS was delivered to each eligible site for ablation prior to radiofrequency application. STS was defined as 'positive' if it could terminate the tachycardia or disrupt the conduction of accessory pathways without myocardial capture and defined as 'negative' if it could not. Radiofrequency ablation was performed irrespective of a positive or negative result from STS and was successful in all 50 patients. Among the 50 successful ablation sites, STS was positive at 26 sites (11 sites in AVNRT, 12 in AVRT and 3 in IART). STS was positive at 4 sites where ablation failed in 3 patients with AVRT and was negative at 8 sites where ablation was successful in 4 patients with AVNRT and 4 with AVRT. The positive and negative predictive value of STS for the detection of the optimal ablation site were, respectively, 100% and 74% in AVNRT, 73% and 72% in AVRT, and both 100% in IART STS-guided mapping is a specific method to predict the successful catheter ablation of reentrant supraventricular tachycardia.

Electroanatomical Mapping (CARTO) of ectopic atrial tachycardia: impact of bipolar and unipolar local electrogram annotation for localization the focal origin

Electroanatomical Mapping (CARTO) allows a tridimensional localization of ectopic atrial tachycardia (EAT). No standardized recommendation exists for annotation the local activation time in EAT using this new technology. In the present study bipolar local electrogram were used for CARTO guided RF ablation of EAT. In comparison the same maps were retrospectively analyzed by annotation the unipolar local electrogram.

METHODS

In 15 consecutive patients (6m, 51+/-14 y) with EAT CARTO mapping was guided by annotation the earliest onset of the bipolar local electrogram. Following successful RF ablation the obtained EAT maps were subsequently evaluated by annotation of the earliest steepest negative intrinsic deflection of the unipolar local electrogram. Both CARTO maps were compared with regard to the region of focal EAT origin.

RESULTS

RF ablation of all 15 EAT foci guided by annotation the bipolar local electrogram with CARTO was successful with a median of 3 [1-18] pulses and a median fluoroscopy time of 10 min [4-25]. All but one focus was located in the right atrium: posterior to posteroinferior region of the terminal crest in 6, septal region in 5, anterior superior region in 3 cases. One left sided EAT was located at the septum. The bipolar CARTO map demonstrated a "small territory" location of earliest activation (extension of the focus < or =0.4 cm(2)) in 14 out of 15 patients. In a single patient the bipolar map showed several sites of earliest local activation (extension >0.4 cm(2)). On the other side the retrospectively achieved unipolar maps demonstrated an extended region of earliest local activation in 6 out of 15 patients (>0.4 cm(2)).

CONCLUSIONS

CARTO maps of EAT by annotation the earliest onset of the bipolar local electrogram provide an efficacious guide for location the focal origin. Extended regions of earliest local activation in EAT might be rather determined by annotation the unipolar in comparison to the bipolar local electrogram.

[Oblique orientation of the accessory pathway demonstrated by radiofrequency application]

Activation mapping of atrial and ventricular insertion has suggested an oblique orientation of some accessory pathways. However, this aspect has not been demonstrated by radiofrequency application. This report presents two patients with Wolff-Parkinson-White syndrome and an accessory pathway with bidirectional conduction and oblique orientation. The accessory pathway oblique orientation was demonstrated by transient and permanent conduction abolition following radiofrequency application in two separate ventricular and atrial sites. These findings may explain the failure to ablate accessory pathway by radiofrequency application in the ventricular side of the mitral annulus guided by retrograde atrial activation occasionally observed in patients with a concealed accessory pathway.

Detection and quantification of valvular heart disease with dynamic cardiac MR imaging

Magnetic resonance (MR) imaging is rapidly gaining acceptance as an accurate, reproducible, noninvasive method for optimal assessment of structural and functional parameters in patients with valvular heart disease. The severity of valvular regurgitation can be evaluated with cine gradient-echo MR imaging, which allows measurement of the area of the signal void corresponding to the abnormal flow jet. Alternatively, this modality can be used to obtain ventricular volumetric measurements and calculate the regurgitant fraction, or velocity-encoded cine (VEC) MR imaging can be used to quantify regurgitant blood flow. The severity of valvular stenosis can be determined by evaluating the flow jet and associated findings with either modality or by using VEC MR imaging to calculate the transvalvular pressure gradient and valve area. Dynamic MR imaging allows accurate assessment of ventricular function and comprehensive evaluation of pathophysiologic changes. In addition, good interstudy reproducibility suggests a role for VEC MR imaging in assessing the effects of therapeutic intervention and monitoring regurgitant fraction, thereby helping in surgical planning and the prevention of ventricular dysfunction. With greater cost-effectiveness and the increasing availability of new hardware and more advanced techniques, MR imaging will become a routine procedure in valvular heart disease.

Catheter ablation of repetitive monomorphic ventricular tachycardia from left ventricular outflow tract guided by unipolar mapping

Repetitive monomorphic ventricular tachycardia from the left ventricular outflow tract is an uncommon arrhythmia. Successful catheter ablation has been previously reported in a few cases, but a large number of applications were usually needed when an approach based on either activation mapping or pace mapping was used. In our patient, the selection of the target point for application was based exclusively on unipolar mapping criteria of the ectopic beats, resulting in a short procedure with successful outcome.

Unipolar electrogram characteristics predictive of successful radiofrequency catheter ablation of accessory pathways

INTRODUCTION

The purpose of this study was to determine the characteristics of the unipolar electrogram that are most helpful in predicting successful radiofrequency ablation of accessory pathways.

METHODS AND RESULTS

The unipolar electrogram was analyzed at 185 ablation sites in 53 patients; 94 attempts were directed at the site of earliest atrial activation ("atrial group") and 91 at the site of earliest ventricular activation ("ventricular group"). The electrogram was analyzed for several features, including pattern ("QS" or "initial R"). Unipolar pattern: Overall, a "QS" pattern was seen at 55% of unsuccessful, 75% of temporarily successful, and 90% of permanently successful sites. For the atrial group, the respective frequencies were 53%, 77%, and 92%, and for the ventricular group, 57%, 73%, and 86%. The difference in pattern distribution between unsuccessful and permanently successful sites was significant for all groups: overall, P < 0.0001; atrial group, P = 0.0005; ventricular group, P = 0.02. Absence of a "QS" pattern (i.e., "initial R") predicted a 92% chance of unsuccessful ablation. Additional features: Activation times were significantly shorter at permanently successful than at unsuccessful (P < 0.0001) or temporarily successful sites (P = 0.0002). No significant differences were found in atrial or ventricular amplitudes or in A/V ratios. Intrinsic deflection slew was lower at temporarily successful sites (P = 0.03 vs all other sites).

CONCLUSION

Ablation at sites revealing an "initial R" pattern (i.e., absent "QS") is very unlikely to be successful. Activation time is shorter at successful sites. These features are equally applicable when mapping the atrial potential as when mapping the ventricular potential.

[Analysis of local electrograms and characteristics of the ablation procedure in left-sided accessory pathways that required five or more pulses of radiofrequency]

INTRODUCTION AND OBJECTIVES

Radiofrequency ablation of left sided accessory pathways requires multiple pulses in some patients due to different factors such as inadequate mapping, inappropriate tissue electrode contact and particular anatomic factors. However these characteristics have not been specifically analyzed.

METHODS

We have studied a prospective ablative series of 65 consecutive patients with left-sided pathways submitted to radiofrequency ablation by a simplified technique. In every application point, we analyzed the electrogram features, application point, impedance, potency and temperature.

RESULTS

52 patients (80%) required less than 5 radiofrequency pulses (group A) and 13 (20%) required > or = than 5 pulses (group B). The presence of a suggestive potential accessory pathway in local electrogram was similar in both groups and there were no differences in the local A-V or V-A intervals. However, in patients with pre-excitation the Delta-V interval was shorter in group A than in group B (8 ms vs 15 ms; p < 0.001). Furthermore, the impedance observed from the ablation point in group A was lower (108 +/- 12 vs 121 +/- 22 ohms; p < 0.001), and the maximum watts required to reach the predetermined temperature was higher in group A (42 +/- 16 vs 31 +/- 18 watts; p < 0.001). Final success of the procedure was 100%.

CONCLUSIONS

Patients requiring more than 5 radiofrequency pulses had electrograms and tissue contact equal or better than those requiring less than 5 pulses. This suggests that difficulties encountered in some procedures can be due to anatomical factors rather than inaccurate mapping or insufficient tissue contact.

Characteristics of intracardiac potentials at successful ablation sites in concealed Wolff-Parkinson-White syndrome

The authors investigated bipolar electrograms recorded from the catheter tip at the actual successful ablation sites in 22 consecutive patients with concealed Wolff-Parkinson-White syndrome to clarify the characteristics of the potentials indicating the optimal site for catheter ablation. In all patients the retrograde transaortic approach to their left-sided accessory pathways, and a temperature-controlled (60 degrees C) energy delivery, were performed. The authors assumed that a shorter dissociation time (time from energy delivery to ventriculoatrial conduction dissociation) indicated more accurate catheter mapping. A significant negative correlation (r = 0.527, p < 0.05) between the AV ratio (ratio of the amplitudes of the atrial to ventricular potentials) recorded at the ablation catheter tip and the dissociation time was observed. When the AV ratio and the dissociation time were compared among the groups classified according to the corresponding Npeak (the number of positive potential peaks in the electrogram obtained from the ablation catheter tip during right ventricular apical pacing) value, they differed significantly (p < 0.05 and p < 0.01, respectively), ie, a higher AV ratio and a shorter dissociation time related to a multipeak electrogram from the ablation catheter tip. The authors conclude that the atrial insertion site of the accessory pathway, exhibiting a multipeak complex electrogram that may represent nonuniform anisotropic characteristics, is an adequate ablation site.

A nodoventricular fiber associated with dual AV nodal conduction, AV nodal reentrant tachycardia, and anterior location of the slow AV nodal pathway

We present a case of a patient with a nodoventricular tract, associated with dual AV nodal conduction and AV nodal reentrant tachycardia, and an anteroseptal location of the slow AV nodal pathway. The remarkable feature of this case is the site of successful ablation, in the anteroseptum just anterior and superior to the His bundle, where both preexcitation and dual AV nodal physiology were abolished.

Reproducibility of bipolar endocavitary electrogram measurements at sites of radiofrequency energy delivery in patients with the Wolff-Parkinson-White syndrome

BACKGROUND

Radiofrequency ablation of atrioventricular accessory pathway is widely used to cure patients with the Wolff-Parkinson-White syndrome. The site of successful ablation is determined using electrophysiological parameters, endocavitary bipolar electrogram measurements being the most commonly used. Interobserver reproducibility of these measurements may limit the reliability of ablation criteria based upon bipolar measurements only but, to our knowledge, this reproducibility has not been evaluated so far. Such was the aim of this study.

METHODS

Three independent observers reviewed the bipolar electrograms recorded at sites were radiofrequency energy was delivered (successfully or not) in 28 consecutive patients with the Wolff-Parkinson-White syndrome. In each tracing, 4 intervals were measured: (1) A0V0 (onset of the atrial electrogram to onset of the ventricular electrogram), (2) AaVa (activation time of the atrial electrogram to activation time of the ventricular electrogram), (3) V0-QRS (onset of the ventricular electrogram to onset of delta wave on the surface ECG) and (4) Va-QRS (activation time of the ventricular electrogram to onset of delta wave on the surface ECG).

RESULTS

The interobserver reproducibility was low since only 50% of A0V0 intervals were measured with an interobserver difference lower than 10 ms and up to 43% of Va-QRS intervals were measured with an interobserver difference greater than 30 ms. The reproducibility of interval measurement was graded from the highest to the lowest as follows: A0V0, AaVa, V0-QRS and Va-QRS (Chi-square statistic, chi 2 = 71.72, p < 0.0001). Kappa values were lower than 0.40, indicating a poor interobserver reproducibility.

CONCLUSIONS

Our study suggests that interobserver reproducibility of only bipolar electrograms interval measurements at sites of radiofrequency ablation of atrioventricular accessory pathway is poor, which limits the reliability of bipolar criteria to predict a successful ablation site.

[High frequency current catheter ablation of accessory conduction pathways]

Radiofrequency catheter ablation has established as the first line therapy for the curative treatment of patients with accessory pathway. Atrioventricular accessory pathways irrespective of the exact localisation can be successfully ablated in more than 90% of all cases. Severe complications associated with the ablation procedure are rare and occur in approximately 2% of patients treated. The recurrence rate after successful ablation is approximately 8 to 10%. Recurrence of accessory pathway conduction occurs almost exclusively within the first 3 months following successful ablation, late recurrences are rare. Patients with variants of accessory pathways such as atriofascicular pathways or retrogradely conducting accessory pathways with decremental conduction properties can also be cured with a high success rate. Because of its well balanced efficacy-risk profile radiofrequency catheter ablation should be recommended as the first line therapy to all symptomatic patients with accessory pathway.

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.

Development and validation of an ECG algorithm for identifying accessory pathway ablation site in Wolff-Parkinson-White syndrome

INTRODUCTION

Delta wave morphology correlates with the site of ventricular insertion of accessory AV pathways. Because lesions due to radiofrequency (RF) current are small and well defined, it may allow precise localization of accessory pathways. The purpose of this study was to use RF catheter ablation to develop an ECG algorithm to predict accessory pathway location.

METHODS AND RESULTS

An algorithm was developed by correlating a resting 12-lead ECG with the successful RF ablation site in 135 consecutive patients with a single, anterogradely conducting accessory pathway (Retrospective phase). This algorithm was subsequently tested prospectively in 121 consecutive patients (Prospective phase). The ECG findings included the initial 20 msec of the delta wave in leads I, II, aVF, and V1 [classified as positive (+), negative (-), or isoelectric (+/-)] and the ratio of R and S wave amplitudes in leads III and V1 (classified as R > or = S or R < S). When tested prospectively, the ECG algorithm accurately localized the accessory pathway to 1 of 10 sites around the tricuspid and mitral annuli or at subepicardial locations within the venous system of the heart. Overall sensitivity was 90% and specificity was 99%. The algorithm was particularly useful in correctly localizing anteroseptal (sensitivity 75%, specificity 99%), and mid-septal (sensitivity 100%, specificity 98%) accessory pathways as well as pathways requiring ablation from within ventricular venous branches or anomalies of the coronary sinus (sensitivity 100%, specificity 100%).

CONCLUSION

A simple ECG algorithm identifies accessory pathway ablation site in Wolff-Parkinson-White syndrome. A truly negative delta wave in lead II predicts ablation within the coronary venous system.