Localization of accessory pathways in the Wolff-Parkinson-White syndrome

Supraventricular tachycardia: diagnosis and management

Supraventricular tachycardia (SVT) includes all forms of tachycardia that either arise above the bifurcation of the bundle of His or that have mechanisms dependent on the bundle of His. We conducted a review of the techniques used to differentiate the mechanisms of SVT. We searched the PubMed and MEDLINE databases for English-language literature published from 1970 to 2008. Articles were selected for either their historical importance or up-to-date clinical data. This review focuses on techniques for scrutinizing electrocardiograms of patients, analyzing in particular the onset of tachycardia, the mode of tachycardia termination, and the effects of premature ventricular contractions, premature atrial contractions, and aberrancy during tachycardia. Both short-term and long-term management of SVT are examined, including the urgent treatment of patients in the emergency department. This review also describes management of patients who have ongoing symptomatic SVT, outlining such available treatment options as atrioventricular node-blocking drugs, antiarrhythmic drugs, and catheter ablation.

Accuracy and limitations of published algorithms using the twelve-lead electrocardiogram to localize overt atrioventricular accessory pathways

INTRODUCTION

The purpose of this study was to evaluate the accuracy and limitations of published algorithms using the 12-lead ECG to localize AV accessory pathways (APs).

METHODS AND RESULTS

The 11 relevant algorithms found in the literature (MEDLINE database and major scientific sessions) were tested on a series of 266 consecutive patients who successfully underwent radiofrequency catheter ablation of a single overt AV AP. The positive predictive values (PPV) of the algorithms in applicable patients were significantly lower for algorithms with > 6 accessory location sites (40.6% +/- 10.9% vs 61.2% +/- 8.0%; P < 0.03) and show a tendency for algorithms not relying on delta wave polarity but on QRS polarity only (36.6% +/- 11.2% vs 52.3% +/- 13.1%; P = 0.09). The PPV in applicable patients is related to the AP location (P < 0.001) and ranked from the highest to the lowest as follows: left lateral (mean PPV = 86.3%), posteroseptal (mean PPV = 65.2%), right anteroseptal (mean PPV = 45.2%), and right posterolateral (mean PPV = 23.4%).

CONCLUSION

Our study suggests that the accuracy of algorithms relying on the 12-lead ECG depends on AP locations as defined in the algorithms and on the number of AP sites. The accuracy tends to be lower when delta wave polarity is not included in the algorithm's architecture. This should be considered when using these algorithms or when building new ones.

Radiofrequency ablation of concealed left free-wall accessory pathways without coronary sinus catheterization: results in 100 consecutive patients

INTRODUCTION

Feasibility of radiofrequency (RF) ablation using a two-catheter technique without coronary sinus catheterization was studied in 100 consecutive patients with a single concealed left free-wall accessory pathway.

METHODS AND RESULTS

Tachycardia was induced by electrical stimulation in the right atrium/right ventricle, and the presence of a concealed left free-wall accessory pathway was suggested electrocardiographically (negative P wave in leads I and/or aVL during orthodromic tachycardia) or by earlier atrial activation in the pulmonary artery compared to the high right atrium. Mapping of the mitral annulus was performed during right ventricular pacing or orthodromic tachycardia, and RF energy was applied at the site with the earliest retrograde atrial activation. Ablation was considered effective if tachycardia could not be induced, and if VA dissociation or exclusive retrograde nodal conduction was observed. Ablation was initially successful in 98 of 100 patients. Mean number of radiofrequency pulses were 3.2 +/- 2. Mean fluoroscopy time and total procedure time was 14 +/- 9 and 107 +/- 32 minutes, respectively. There were no complications related to the procedure. At a mean follow-up of 22 +/- 13 months, two patients experienced tachycardia recurrence and required a second procedure, which was successful.

CONCLUSIONS

Our results suggest that RF catheter ablation of concealed left free-wall accessory pathways can be safely, effectively, and rapidly performed using a simplified two-catheter technique with no need for coronary sinus catheterization.

[Radiofrequency ablation of occult left accessory pathways without catheterization of the coronary sinus]

BACKGROUND

Radiofrequency catheter ablation of concealed left-sided accessory pathways conventionally implies the introduction of several catheters for the assessment of electrophysiological properties as well as for the localization of the accessory pathways.

PATIENTS AND METHODS

Feasibility of radiofrequency ablation using a simplified two-catheter technique without coronary sinus catheterization was prospectively studied in 95 consecutive patients with a single concealed left free-wall accessory pathway. A 6F quadripolar catheter was introduced into the right atrium/right ventricle and tachycardia was induced by electrical stimulation. The presence of a concealed left-sided accessory pathway was suggested electrocardiographically (negative P wave in I and/or aVL during orthodromic tachycardia) or by earlier atrial activation in the pulmonary artery compared to the right atrium. Mapping of the mitral annulus and ablation were performed during orthodromic tachycardia or ventricular pacing using a 7F steerable catheter. Radiofrequency energy was applied at sites with the shortest VA interval. The procedure was considered effective if tachycardia could not be induced and if VA dissociation or exclusive nodal VA conduction were observed.

RESULTS

The procedure was initially successful in 93 out of 95 patients (98%). Mean number of applications were 3.2 +/- 2. Mean fluoroscopy time and total procedure duration were 14 +/- 9 and 108 +/- 33 minutes respectively. At a mean follow-up of 21 +/- 13 months, 2 patients required a second session because of tachycardia recurrence.

CONCLUSIONS

Radiofrequency catheter ablation of concealed left-sided accessory pathways can be safely, effectively and rapidly performed using a two-catheter technique without coronary sinus catheterization.

Earlier activation of the distal than the proximal site of the coronary sinus may represent retrograde conduction through AV node: significance of recording of far distal coronary sinus

During retrograde conduction through an accessory pathway (AP) or the atrioventricular (AV) node, earlier activation of the distal recording site than a more proximal site of the coronary sinus (CS) generally indicates retrograde conduction via a distally located AP. Thus, after successful ablation of a left-sided AP, if the distal CS recording site is activated earlier than a more proximal site retrogradely, it is considered to suggest-in the absence of His-bundle recording or more frequently in the setting of poor recording of the low septal right atrial electrogram-a conduction via a second AP (located more distally), and not conduction via the AV node. Yet, we hypothesized that retrograde conduction through the AV node may activate the far distal site of the CS (CSD) earlier than a more proximal site, as the anterior atrial wavefront, coming retrogradely from the AV node and traveling along the anterior mitral annulus, could reach the CSD earlier than a more proximal site. To test this we studied 18 patients with intact retrograde conduction via the AV node, but without evidence of an AP. The CSD was recorded by means of a quadripolar catheter (interelectrode distance of 2-5 mm); retrograde activation sequence at the distal (CSD1-2) versus proximal (CSD3-4) bipolar recording site was determined during ventricular stimulation. In 12 of 18 patients the CSD1-2 recording site was activated 5-10 ms earlier than the CSD3-4 recording site, in 3 of 18 patients the CSD1-2 site was activated 5 ms later than the CSD3-4 site; in the remaining 3 patients both recording sites were depolarized simultaneously. The results indicate that the CSD was often depolarized earlier than a more proximal site by impulses that conducted to the atria retrogradely via the AV node while the quadripolar recording catheter was placed at the CSD. This observation, although not well documented previously, suggests that the sequence of retrograde atrial activation in the CS should be studied carefully in consideration of the actual location of the mapping catheter in order to correctly diagnose the presence or absence of conduction via an AP.

Utility of the 12-lead electrocardiogram in localizing the origin of right ventricular outflow tract tachycardia

The purpose of this investigation was to develop an algorithm on the basis of the QRS morphology observed on the 12-lead ECG that would rapidly locate the site of origin of the monomorphic ventricular tachycardia arising from the septal portion of the RVOT. Radiofrequency catheter ablation guided by pace-mapping techniques has proven effective in eliminating the ventricular tachycardia originating from the RVOT in the absence of structural heart disease. A method that would rapidly identify the portion of the RVOT septum toward which more detailed pace-mapping should be directed before catheter ablation would be useful in decreasing procedure time and radiation exposure and potentially facilitating a successful ablation procedure. The RVOT septum was divided into nine sites. In 11 patients, bipolar pacing was performed at each of the nine designated sites to mimic ventricular tachycardia. A standard 12-lead surface ECG was recorded during pacing. The QRS morphology in the limb leads was characterized and the site of the R-wave transition was determined in the precordial leads. A QS in lead a VR and a monophasic R wave in leads II, III, aVF, and V6 were noted in each patient at all paced sites. In lead I, pacing at the three posterior septal sites always resulted in an R wave. Pacing at the three anterior sites produced a dominant Q wave (either QS or Qr) at 17 (52%) of 33 sites or a qR complex at 16 (48%) of 33 sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiographic imaging of coronary sinus diverticula and middle cardiac veins in patients with preexcitation syndrome: impact on radiofrequency catheter ablation of posteroseptal accessory pathways

To determine the value of echocardiography for identifying coronary sinus (CS) diverticula and middle cardiac veins (MCVs) in patients with posteroseptal accessory pathways (PAPs), transthoracic (TTE) and transesophageal echocardiography (TEE) were performed in 18 consecutive patients with PAP and in 15 control subjects with left lateral accessory pathway before CS angiography. The size, shape, and location of CS diverticula and MCV were described and compared to angiography. TEE and angiography were concordant for the identification of diverticula (n = 5) and agreed for depicting MCV in 22 of the 27 cases. TTE revealed 4 of 5 diverticula and identified 4 of 27 MCV (P < 0.001). Fourteen MCV but no diverticula were found in the control subject. There was no significant difference between transesophageal and angiographic measurements for the width (23.5 +/- 4.9 vs 26.8 +/- 6.6 mm) and height (13.5 +/- 3.8 vs 15.7 +/- 3.4 mm) of the diverticula, and the width (3.5 +/- 0.7 vs 3.7 +/- 0.6 mm) of MCV. TEE underestimated the length of the MCV (12.0 +/- 1.8 vs 27.2 +/- 6.0, P < 0.001). Delivery of radiofrequency energy within the neck of a diverticulum or within an MCV was successful in 5 of 5, and 6 of 13 cases in patients with PAPs, respectively. In conclusion, echocardiography was as reliable as angiography for detecting and describing CS diverticula and MCV in patients with preexcitation syndrome. Echocardiography is recommended prior to electrophysiological study because it may simplify radiofrequency catheter ablation.

Atrial and accessory pathway activation direction in patients with orthodromic supraventricular tachycardia: insights from vector mapping

OBJECTIVES

The purpose of this study was to utilize vector mapping to investigate atrial and accessory pathway activation direction during orthodromic supraventricular tachycardia.

BACKGROUND

Although advances have been made in the electrophysiologic evaluation and management of accessory pathways, our understanding of accessory pathway anatomy and physiology remains incomplete. Vector mapping has been validated as a method of studying local myocardial activation.

METHODS

In 28 patients with a left-sided or posteroseptal accessory atrioventricular (AV) pathway referred for ablation, atrial and accessory AV pathway activation direction was determined during ventricular pacing or orthodromic supraventricular tachycardia, or both, by summing three orthogonally oriented bipolar electrograms recorded from the coronary sinus to create three-dimensional vector loops. Atrial and accessory AV pathway activation direction was determined in all patients from the maximal amplitude vectors of the vector loops. Because of beat to beat variability in the directions of the vector loops, data from 8 of 28 patients could not be analyzed.

RESULTS

At 81 of 83 sites, atrial activation direction along the long axis of the coronary sinus corresponded with the direction suggested by activation time mapping. Activation direction along the anteroposterior and inferosuperior axes was variable, potentially due to variations in the level of the atrial insertion of the accessory AV pathway and in the depth or angling of pathway fibers in the AV fat pad. In eight patients, at least one recording was obtained at the site of an accessory AV pathway potential. Accessory AV pathway activation proceeded superiorly and to the right in seven of eight patients; in one patient with a posteroseptal pathway, accessory AV pathway activation proceeded superiorly and to the left.

CONCLUSIONS

1) Vector mapping is a useful technique for localizing accessory AV pathways; 2) left-sided accessory AV pathways angle from left to right as they traverse the AV groove; and 3) variable activation directions of the atrial myocardium adjacent to the coronary sinus suggest that accessory AV pathway insertion into the atrium differs from patient to patient.

Nonuniformity of AH intervals during stimulation at different left atrial sites

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at different left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CS) affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atrial sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on: stimulus-atrium (SA), AH, and stimulus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900-350 msec, mean 532 +/- 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 +/- 10 msec, 57 +/- 10 msec, 44 +/- 11 msec, and 32 +/- 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for HRA vs proximal CS). The mean AH intervals were 123 +/- 23 msec, 104 +/- 28 msec, 95 +/- 15 msec, and 90 +/- 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CS). In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > or = 15 msec; in 9 patients this difference was only < or = 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.

NASPE Young Investigator Awardee 1992. Three-dimensional electrogram mapping improves ablation of left-sided accessory pathways

Conventional electrogram mapping techniques for localization of accessory pathways during radiofrequency ablation procedures are time consuming and often inaccurate. We hypothesized that a computer generated, three-dimensional electrogram of retrograde atrial activation created from signal-averaged sequential endocardial bipolar electrograms (collected from the atrial aspect of the mitral annulus using a single transseptal catheter and then time aligned to a known myocardial activation reference) would improve left-sided accessory pathway atrial insertion site identification and increase ablation efficiency. Ablation efficiency was defined by procedure time, fluoroscopy time, duration of radiofrequency energy required to achieve initial accessory pathway block, cumulative ablation energy per procedure, and number of radiofrequency energy applications. Patients with single left-sided accessory atrioventricular connections were studied. Standard mapping results in 31 patients (group A) were compared to a three-dimensional electrogram approach used in 26 patients (group B). Three-dimensional electrogram mapping reduced procedure time (group A 3.8 +/- 1.6 vs group B 2.8 +/- 0.9 hours, P < 0.004), fluoroscopy time (group A 45.3 +/- 35.0 vs group B 25.1 +/- 10.5 min, P < 0.02), time to accessory pathway block (group A 2.6 +/- 1.5 vs group B 1.2 +/- 0.5 sec, P < 0.002), cumulative radiofrequency energy (group A 2126 +/- 2207 vs group B 636 +/- 586 joules, P < 0.0008), and radiofrequency energy applications (group A 5.0 +/- 4.4 vs group B 1.7 +/- 1.2, P < 0.0002). We conclude that three-dimensional electrogram mapping improves left-sided accessory pathway atrial insertion localization, reduces ablation procedure time and radiation exposure, and improves ablation efficiency.

Accuracy of various methods of localization of the orifice of the coronary sinus at electrophysiologic study

The coronary sinus (CS) orifice is an important reference point for determining electrode and, thereby, accessory pathway location at electrophysiologic study. The reliability of fluoroscopic landmarks used to identify the CS orifice is not known. This study compared the accuracy of several fluoroscopic landmarks for identifying the CS orifice with the location defined by radiopaque contrast injection of the CS. Forty patients were studied. Radiographic markers of the CS orifice that were examined included: (1) the point at which the CS catheter prolapsed during advancement, (2) the point of maximum convexity of the CS catheter when a superior vena caval approach was used, (3) the right side of the ventricular septum, and (4) the relation to the underlying vertebrae. The least-significant difference method of multiple comparisons was used for statistical analysis. The point at which the CS catheter prolapsed was the most accurate noncontrast method for determining the location of the CS orifice (p less than 0.05), but was possible without the use of excessive force in only 48% of patients. The point of catheter prolapse was a median of 1 mm (range 0 to 11) from the true location of the os. Errors with other examined landmarks ranged up to 3 cm. Identification of the CS orifice is best performed by radiopaque contrast injection. The point of prolapse during catheter advancement in the CS is an accurate alternative when contrast injection is not feasible. Other noncontrast fluoroscopic landmarks are less reliable and are best avoided.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypothesis testing as an approach to the analysis of complex tachycardias--an illustrative case of a preexcitation variant

The correct elucidation of the electrophysiological substrate and mechanism(s) responsible for a complex arrhythmia requires a systematic approach to the analysis of the electrophysiological data. One approach calls for the formulation of a set of hypotheses that could explain the data obtained during the study. The hypotheses are then tested for compatibility with phenomena observed and the one that agrees with the majority of the findings would represent the most tenable explanation. We present the case of a young girl with a wide QRS complex tachycardia and a history of ventricular preexcitation that illustrates this approach. The complexities were resolved only after intraoperative analysis and surgical ablation of a right-sided accessory pathway with decremental properties, and provides further insight into our understanding of the nodoventricular Mahaim fiber.

Predictive accuracy of electrophysiologic localization of accessory pathways

Operative ablation of accessory pathways depends critically on preoperative localization when technical limitations preclude complete intraoperative mapping. To assess the accuracy of localization, 345 patients undergoing operative ablation were studied; 316 (91.6%) had a single accessory pathway and 29 (8.4%) had multiple accessory pathways. The electrophysiologic study was diagnostically complete and accurate in 294 patients (93%) with a single accessory pathway and 19 (61%) with multiple accessory pathways. A left lateral accessory pathway was most accurately localized with excellent sensitivity (99%) and positive predictive value (98.5%). Diagnostic errors occurred in 33 patients because of 1) incorrect localization (n = 16), 2) failure to detect a second pathway (n = 9), and 3) diagnosis of a second pathway not verified intraoperatively (n = 8). Multiple pathways were more prevalent in the group with errors (33.3% vs. 5.8%, p = 0.0001), as were unidirectional pathways (48.5% vs. 24.3%, p = 0.003). It is concluded that preoperative localization of accessory pathways is sufficiently accurate to allow intraoperative mapping to be brief and focused.