Accessory Pathways In Patients Research Articles

Unmasking Accessory Pathway Conduction with Adenosine-induced Atrioventricular Nodal Block After Radiofrequency Catheter Ablation

Radiofrequency catheter ablation is very effective in eliminating conduction over accessory pathways in patients with Wolff-Parkinson-White syndrome. However, accessory pathway conduction recurs in approximately 5 to 9 percent of patients in the weeks to months following ablation. We describe two cases in which intravenous adenosine revealed persistent accessory pathway conduction after apparently successful ablation, thus providing an indication for the delivery of further ablative therapy. Adenosine may improve the long-term efficacy of radiofrequency catheter ablation of accessory pathways by manifesting latent accessory pathway conduction.

Radiofrequency ablation of posteroseptal accessory pathways in patients with abnormal coronary sinus

Radiofrequency ablation of posteroseptal accessory pathways in patients with abnormal coronary sinus

Pace mapping using body surface potential maps to guide catheter ablation of accessory pathways in patients with Wolff-Parkinson-White syndrome.

BACKGROUND. A pace mapping technique using body surface potential maps (BSPMs) was developed to guide the positioning of an ablation catheter at the ventricular insertion point of accessory pathways (AP) in patients with the Wolff-Parkinson-White syndrome (WPW). METHODS AND RESULTS. The study was performed on 30 WPW patients. BSPMs were recorded with 63 leads distributed over the entire torso surface. The catheter used for radiofrequency ablation was first placed in the vicinity of the ventricular preexcitation site predicted by BSPMs recorded during the delta wave. BSPMs were then recorded during pacing with this catheter, the comparison between the preexcited and paced BSPMs indicated whether the pacing site was too anterior or posterior with respect to the preexcitation site, and the catheter was moved accordingly. This process was repeated until the preexcited and paced BSPMs were highly correlated (r > or = 0.8), and ablation then was attempted. It was possible to successfully ablate the AP in 28 patients after an investigation that lasted 54 +/- 44 minutes between the recording of the first paced BSPM and that of the BSPM paced at the successful ablation site. Patients with left free wall pathways needed less investigation time compared with patients with pathways of other locations (46 +/- 9 versus 100 +/- 25 minutes, p = 0.031). The sensitivity of BSPM pace mapping was assessed using pacing with a multipolar catheter, and significant changes were observed on the BSPMs for beats with pacing sites that were only 5 mm apart. CONCLUSIONS, BSPM pace mapping allowed us to achieve a 93% success rate with short investigation durations, provides significant information that cannot be obtained with the standard 12-lead ECG, is a self-correcting procedure that reduces the importance of BSPM alterations due to individual differences in the shape of the torso or heart, and is applicable only to patients with AP showing antegrade conduction.

Alfentanil-midazolam anaesthesia has no electrophysiological effects upon the normal conduction system or accessory pathways in patients with Wolff-Parkinson-White syndrome.

The effects of alfentanil-midazolam anaesthesia upon the electrophysiologic (EP) properties of normal atrioventricular (A-V) and accessory pathway (AP) conduction were studied in eight patients with Wolff-Parkinson-White syndrome during accessory pathway surgical ablation. The presence of an AP was confirmed by preoperative EP studies. Anaesthesia was induced with alfentanil (50 micrograms.kg-1) and midazolam (0.15 mg.kg-1) and maintained with an alfentanil infusion (2 micrograms.kg-1.min-1) and intermittent boluses of midazolam (1-2 mg q 15 min, PRN). Following sternotomy, a baseline EP study was performed which consisted of effective refractory period (ERP) and shortest cycle length (SCC) measurement during antegrade conduction in the AV and AP, as well as during retrograde conduction in the AP. Comparison with preoperative EP studies indicated that the administration of alfentanil-midazolam anaesthesia had no effect upon conduction or ERP in either pathway. Haemodynamic stability occurred throughout the surgical procedure with no tachyarrhythmias. We conclude that a combination of alfentanil-midazolam is suitable for general anaesthesia in patients undergoing ablative procedures for accessory pathways.

Effect of Ebstein's anomaly on short- and long-term outcome of surgically treated patients with Wolff-Parkinson-White syndrome.

Ebstein's anomaly is the most commonly occurring congenital abnormality associated with the Wolff-Parkinson-White (WPW) syndrome. However, the effects of Ebstein's anomaly on the risks and benefits of surgical ablation of accessory pathways in patients with WPW syndrome are unknown. This study compared the long-term outcome of 38 WPW patients with Ebstein's anomaly undergoing accessory pathway ablation to a reference population of 384 similarly treated patients without the anomaly. Ebstein's anomaly was mild in 21 patients (55%) and moderate-to-severe in 17 patients (45%). Sixteen patients (42%) required tricuspid valve surgery, and 23 (61%) had an atrial septal defect or patent foramen ovale repaired. Baseline clinical characteristics and preoperative clinical arrhythmias were similar in both groups. Ten-year survival was 92.4% and 91.2% for patients with and without Ebstein's anomaly, respectively (p = NS). During a mean follow-up of 6.2 +/- 3.8 and 5.3 +/- 3.6 years, 82% of patients with and 90% without Ebstein's anomaly had either clinically insignificant or no arrhythmias, and 18% versus 10% reported symptoms suggesting arrhythmias lasting longer than 1 minute, respectively. Atrial fibrillation was reduced postoperatively to 9% (p less than 0.001) in patients with and to 4% (p less than 0.001) in those without the anomaly. Fewer hospitalizations were reported postoperatively by 90% versus 96% of patients with and without Ebstein's anomaly; 9.4% versus 6.0% of patients were disabled at follow-up, respectively (p = NS). Patients with Ebstein's anomaly are improved significantly after accessory pathway ablation. The presence of this anomaly should not preclude accessory pathway ablation in these patients.

Usefulness of noninvasive studies in assessment of accessory pathway in patients with Wolff-Parkinson-White syndrome

Usefulness of noninvasive studies in assessment of accessory pathway in patients with Wolff-Parkinson-White syndrome

Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease.

Radiofrequency energy has been used safely and successfully to eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome and the substrate for atrioventricular nodal reentrant tachycardia. However, this form of ablation has had only limited success in eliminating ventricular tachycardia in patients with structural heart disease. In contrast, direct-current catheter ablation has been used successfully to eliminate ventricular tachycardia in patients with and without structural heart disease. The purpose of this study was to test whether radiofrequency energy can safely and effectively ablate ventricular tachycardia in patients without structural heart disease. Sixteen patients (nine women and seven men; mean age, 38 years; range, 18-55 years) without structural heart disease who had ventricular tachycardia underwent radiofrequency catheter ablation to eliminate the ventricular tachycardia. Two patients presented with syncope, nine with presyncope, and five with palpitations only. Mean duration of symptoms was 6.7 years (range, 0.5-20 years). Radiofrequency catheter ablation successfully eliminated ventricular tachycardia in 15 of 16 patients (94%). Sites of ventricular tachycardia origin included the high right ventricular outflow tract (12 patients), the right ventricular septum near the tricuspid valve (three patients), and the left ventricular septum (one patient). The only ablation failure was in a patient whose ventricular tachycardia arose from a region near the His bundle. An accurate pace map, early local endocardial activation, and firm catheter contact with endocardium were associated with successful ablation. Radiofrequency ablation did not cause arrhythmias, produced minimal cardiac enzyme rise, and resulted in no detectable change in cardiac function by Doppler echocardiography. Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease is effective and safe and may be considered as early therapy in these patients.

Two-dimensional echocardiographic phase analysis. Its potential for noninvasive localization of accessory pathways in patients with Wolff-Parkinson-White syndrome.

In patients with the preexcitation syndrome who are undergoing transcatheter or surgical ablation, accurate localization of accessory pathways is critical. Because preexcitation is known to alter ventricular activation sequence and result in focal areas with presystolic contraction, we investigated whether phase analysis applied to two-dimensional echocardiographic cine loops objectively identifies these focal areas and can be used to localize ventricular insertion sites of accessory pathways. We prospectively obtained phase images in 17 patients (11 males; age range, 11-35 years) during minimal preexcitation in normal sinus rhythm and during maximal preexcitation induced by right atrial pacing. A group of 11 normal subjects (six men; age range, 26-37 years) served as controls. Pathway locations predicted from phase imaging were compared with those predicted from routine 12-lead ECGs, from visual inspection of cine loop images, and from catheter-mounted electrode endocardial mapping. Cross-sectional views in a digital cine loop format were mathematically transformed using a first harmonic Fourier algorithm to obtain the corresponding phase images. Phase angle histograms were derived in eight wall segments. Mean and earliest phase angles were derived by computer analysis to quantitate contraction sequence. We found that during right atrial pacing, phase angles in focal areas markedly deviated from normal--mean phase angles from 33 degrees to 164 degrees, and earliest phase angles from 50 degrees to 180 degrees. Accessory pathways could be precisely localized in 53% of the patients by 12-lead ECG, in 59% by visual inspection of cine loop images, in 82% by phase imaging, and in 94% by a combination of the three methods. Our results suggest that phase imaging, especially when used in combination with cine loop and 12-lead ECG, can be used to localize ventricular insertion sites of accessory pathways and may be clinically useful as a noninvasive adjunct to endocardial mapping in patients with Wolff-Parkinson-White syndrome.

Importance of physical parameters for the effectiveness of radiofrequency catheter ablation

Radiofrequency catheter ablation has been shown to be an effective form of treatment of accessory pathways in patients with WPW-syndrome and other supraventricular tachycardias. However, the biophysical parameters so far used in vivo neither correlated with the size of the myocardial lesion nor did they provide any information about contact of the electrode with the myocardial wall. In this study, 104 radiofrequency energy applications were performed on excised pig myocardium in circulating heparinized pig blood, and in blood alone, and root mean square (rms) voltage, current and phase angle were measured using a specially developed device. The calculated effective power and output power differed by only 2-7% measured at the point of maximum current during coagulation. A progressive drop in current following a rise in impedance led to a phase shift of more than 80 degrees with a decrease in effective power to 17% of the output power. Hence, apparent output power was mainly ineffective power. The time-dependent variations of phase angle, impedance and current were found to be useful for distinguishing between the coagulated media. These results show that physical parameters measured during radio-frequency catheter ablation may help to monitor electrode position in the clinical situation and reduce the number of ineffective energy applications.

Single-catheter approach to radiofrequency current ablation of left-sided accessory pathways in patients with Wolff-Parkinson-White syndrome.

Catheter ablation with the use of radiofrequency current has been introduced as a therapeutic option for patients with tachyarrhythmias mediated by an accessory atrioventricular pathway. The technique conventionally implies the introduction of several catheters into the heart for assessment of electrophysiological parameters as well as for localization of the accessory pathway and may last for several hours. Thirty-four patients with Wolff-Parkinson-White syndrome and a delta wave pattern indicative of an overt (i.e., capable of consistent antegrade conduction) left-sided free-wall accessory pathway underwent attempts at radiofrequency current ablation of the pathway with the use of just one catheter. No patient had a previous electrophysiological study. The catheter was introduced into the left ventricle close to the mitral annulus and was used for pathway localization as well as for ablation. The approach was completely successful in 30 patients (88%). In the remaining four patients, ablation of the pathway was achieved by using the multiple-catheter approach. Overall procedure duration was 2.0 +/- 1.1 hours; radiation exposure time was 22.8 +/- 20.4 minutes (median, 17.3 minutes). There were no acute complications. The single-catheter approach to radiofrequency current ablation of overt left-sided free-wall accessory pathways is feasible, safe, and effective in the majority of patients. The approach requires considerable investigator experience but significantly reduces procedure duration and radiation exposure time.

Histopathology of Monopolar Transcatheter Radiofrequency Ablation at the Mitral Valve Annulus

Although monopolar radiofrequency (RF) catheter ablation is being used to interrupt left-sided accessory pathways in patients with tachyarrhythmia, little is known of the histologic effects from this method of treatment. RF ablation at the mitral valve (MV) annulus was performed in ten dogs to examine the histology of the lesion area. A custom 6 French ablation catheter with a 4 mm distal electrode was positioned beneath the MV adjacent to the annulus. Mean preablation atrial to ventricular electrogram ratio (A/V ratio) was 0.26 +/- 0.17. Thirty +/- 1 watts of RF power were applied for 53 +/- 13 seconds between the distal electrode and a large skin electrode. Nine dogs were sacrificed 6 weeks and one dog 2 days following ablation. Annular lesions were seen in eight of the ten dogs. Lesion volume was 136 +/- 41 mm3 and correlated with the A/V ratio (r2 = 0.74, P = 0.006). Lesions consisted of necrosis of the left ventricle with extension into the atrioventricular groove and left atrium. No injury to the coronary sinus or circumflex artery was observed. A small area of injury was noticed on the mitral leaflet in one dog. Monopolar RF ablation creates lesions at the MV annulus without injury to adjacent vascular structures.

Phase Image Triangulation of Accessory Pathways in Patients Undergoing Catheter Ablation of Posteroseptal Pathways

The outcome of posteroseptal accessory pathway ablation by direct current (DC) shocks delivered just outside the os of the coronary sinus was studied in 21 patients. Electrocardiographic and electrophysiological parameters as well as phase image patterns of equilibrium multiple-gated blood-pool scintigrams were studied to determine their usefulness in predicting the success of ablation. A second free-wall pathway was documented by electrophysiological or surgical findings in six patients, and the value of phase images in detecting this second pathway was studied as well. Ablation was successful in 57%. The cumulative mean energy of DC shocks amounted to 524 +/- 170 joules and was not predictive of ablation outcome, neither was the mean ventriculoatrial (VA) conduction time. The predictive value of the 12-lead maximally preexcited electrocardiogram was poor in the 15 patients with a single posteroseptal bypass tract. A new method to triangulate the site of the earliest phase angle on the atrioventricular (AV) valve plane successfully localized the bypass pathway in 14 of those patients. No specific phase pattern predicted successful ablation except for a symmetrical, concentric peripheral phase progression found to be predictive of ablation success in the four patients who showed this pattern. Phase analysis was able to localize the second, nonposteroseptal pathway in four of six patients. This study showed that a concentric peripheral phase progression in the gated blood-pool scintigrams is predictive for ablation success in patients with posteroseptal pathways. A free-wall localization of the earliest phase angle is suggestive of a second bypass tract in this area.

Surgical treatment of the Wolff-Parkinson-White syndrome by epicardial electrical ablation

A new operation to eliminate accessory pathways—epicardial electrical ablation—is described. In a group of 201 patients without concomitant disease, the mortality rate was 0.5% and the overall efficacy of the operation for free wall accessory pathways, 98%. A retrospective clinical study of 44 unselected patients was performed to examine how safe epicardial electrical ablation is. The criteria for intraoperative effectiveness were disappearance of both the delta wave and retrograde conduction and inability to induce tachycardia. In the postoperative and follow-up periods, the following were reviewed: electrocardiograms; Holter monitor recordings (24 to 26 hours); release of the myocardial-specific isoenzyime of creatine kinase; intracardiac hemodynamics and myocardial contractility (radionuclide methods); selective coronary arteriograms and ventriculograms; mean work capacity (bicycle ergometer); diagnostic transesophageal electrical stimulation; and histology of the area of ablation. The main conclusion of this study is that epicardial electrical ablation is a highly efficient and safe operation for surgical elimination of parietal accessory pathways in patients with Wolff-Parkinson-White syndrome. Its advantages are its technical simplicity and the opportunity to review results immediately during the operation.

Radiofrequency catheter ablation of ventricular tachycardia in patients without structural heart disease

BACKGROUNDRadiofrequency energy has been used safely and successfully to eliminate accessory pathways in patients with the Wolff-Parkinson-White syndrome and the substrate for atrioventricular nodal reentrant tachycardia. However, this form of ablation has had only limited success in eliminating ventricular tachycardia in patients with structural heart disease. In contrast, direct-current catheter ablation has been used successfully to eliminate ventricular tachycardia in patients with and without structural heart disease. The purpose of this study was to test whether radiofrequency energy can safely and effectively ablate ventricular tachycardia in patients without structural heart disease.METHODS AND RESULTSSixteen patients (nine women and seven men; mean age, 38 years; range, 18-55 years) without structural heart disease who had ventricular tachycardia underwent radiofrequency catheter ablation to eliminate the ventricular tachycardia. Two patients presented with syncope, nine with presyncope, and five...

The influence of age on effective refractory periods of the accessory pathway in patients with Wolff-Parkinson-White syndrome

The influence of age on effective refractory periods of the accessory pathway in patients with Wolff-Parkinson-White syndrome

An Artificial Neural Network to Localize Atrioventricular Accessory Pathways in Patients Suffering from the Wolff‐Parkinson‐White Syndrome

The electrocardiographic localization of atrioventricular accessory pathways has been extensively described in the literature by a number of well-known electrophysiologists and surgeons. These descriptions, often represented as decision trees, are useful, but do not apply in all cases. To formalize the process of determining the proper localization, this expert human knowledge could be represented in an expert system. But since reasoning is partly based on the use of heuristic knowledge, and are often not represented in the written description of the human expert, the results will be suboptimal. On the other hand, by using a self-learning neural network approach, the causal relations between input (polarity of the delta waves) and output (the correct localization) do not have to be defined by the expert. It is derived by the neural network, by analyzing a learning set of cases consisting of the ECG plus the corresponding correct localization. In our set of 60 cases, 2 hours of training were required to learn how to localize all cases correctly. From a control set of 25 cases, 23 were interpreted by the system satisfactorily. the neural network approach can be useful in situations where causal relations between the electrocardiogram and underlying mechanism are partly undefined.

Comparative accuracy of the vectorcardiogram and electrocardiogram in the localization of the accessory pathway in patients with Wolff-Parkinson-White syndrome: Validation of a new vectorcardiographic algorithm by intraoperative epicardial mapping and electrophysiologic studies

The scalar electrocardiograms (ECGs) and vectorcardiograms (VCGs) of 41 patients with Wolff-Parkinson-White (WPW) syndrome were used to compare the accuracy of these techniques in the identification of the site of preexcitation. The location of the accessory pathway (AP) was determined by endocavitary electrophysiologic studies in all patients and the location was confirmed during intraoperative epicardial mapping in 28 of them. The ECGs were classified according to Gallagher's criteria and with Milstein's algorithm, whereas the VCGs were classified according to a new two-step algorithm. The presence of multiple accessory pathways and coexisting myocardial infarctions were major limitations in both the VCG and ECG classification procedures. In patients with a single accessory pathway, three AP localizations (right free ventricular wall, posterior, or left free ventricular wall) were identified with the first step of the VCG algorithm, with an overall sensitivity (96.5%), specificity (90.7%), and positive predictive values (80%) that were greater than those obtained with the ECG Milstein algorithm (77.1%, 91.5%, and 75%, respectively). The second step of the VCG algorithm made it possible to identify an AP location in one of the following sites: anterior right, lateral right, posterior right, posterior left, lateral left, or anterior left ventricle. The overall sensitivity, specificity, and positive predictive values were greater for the second step of the VCG algorithm than for the ECG criteria proposed by Gallagher (43.6% versus 39.3%, 92.1% versus 87.4%, and 51.5% versus 33.3%, respectively). It was concluded that the VCG seems to be more specific and sensitive than the ECG in the identification of the preexcitation site and should be given preference in the initial evaluation of the WPW syndrome.

Electrophysiological Demonstration of Anterograde Concealed Conduction in Accessory Atrioventricular Pathways Capable Only of Retrograde Conduction

Anterograde concealed conduction into the concealed accessory atrioventricular (AV) pathway has been postulated to be one of the factors preventing the reciprocating process via the accessory pathway in patients with the concealed Wolff-Parkinson-White(WPW) syndrome but its presence has not been documented. To demonstrate the occurrence of anterograde concealment, 12 patients with the concealed WPW syndrome were selected for study. A pacing protocol was designed in which the retrograde conduction of the ventricular extrastimulus over the accessory pathway was assessed during ventricular pacing alone (conventional method) and during the AV simultaneous pacing (simultaneous method); the results were then compared. When the high right atrium was simultaneously paced, the effective refractory period of the concealed accessory pathway shortened as compared with the conventional method in five of 12 patients (from 341.7 +/- 110.8 to 312.5 +/- 108.2 msec, n = 12), whereas, it decreased in all patients studied when the coronary sinus near the accessory pathway was simultaneously paced (from 375.7 +/- 135.0 to 287.1 +/- 116.1 msec, n = 7). These results demonstrate that the AV simultaneous pacing frequently shortens the refractoriness of the concealed accessory AV pathway and such facilitation seems to be well explained by the probable anterograde concealment in it and peeling back of the refractory barrier.

Pre- and intraoperative identification of multiple accessory pathways. Experience of 19 pathways in 9 patients.

The pre- and intraoperative electrophysiological studies in 9 patients with two or more accessory pathways are described. The presence of multiple accessory pathways was clinically suspected in only 2 patients. During the preoperative electrophysiological study two accessory pathways were identified in 7 patients and a single pathway in 2 patients. At operation, additionally three accessory pathways were identified in 3 patients. One out of two pathways, found preoperatively, could not be confirmed in 1 patient. It is concluded that the clinical or preoperative electrophysiological evidence of only one accessory pathway should not distract one's attention from considering multiple accessory pathways in patients presenting only one type of tachycardia.

Electrophysiological Properties of the AV Node and the Accessory Pathway in Patients with the AV Reentrant Tachycardia

Electrophysiological Properties of the AV Node and the Accessory Pathway in Patients with the AV Reentrant Tachycardia