Accessory Pathways In Patients Research Articles

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

Augmented preexcitation assessed by scintigraphic phase analysis during atrial pacing

We sought to characterize the effect of augmented preexcitation on the phase image pattern associated with scintigraphic acquisition during conduction via accessory arteriovenous connections. For this reason we assessed phase image scintigraphy, acquired in sinus rhythm and during rapid atrial pacing in 12 patients with documented right (five patients) or left (seven patients) lateral accessory pathways. Augmented preexcitation during atrial pacing was documented at electrophysiologic study in all patients during atrial pacing at similar rates. Phase analysis was abnormal in only 8 patients during sinus rhythm but in all 12 patients during atrial pacing. Atrial pacing brought a significant delay in both mean left and right ventricular phase angles, LVφ̄ and RVφ̄, respectively. With atrial pacing, the site of earliest phase angle, interpreted to indicate the site of earliest excitation, shifted to the site of the accessory pathway. There was increased relative “prematurity” of the mean phase angle of the ipsilateral ventricle and an absolute increase in the difference between mean and earliest left and right ventricular phase angles, Δφ̄ (LV-RV) and Δ φ 0 (LV-RV), respectively. In patients with right-sided pathways, Δφ̄ (LV-RV) increased from 9.5 ± 12.6 degrees to 47.9 ± 22.8 degrees, whereas Δ φ 0 (LV-RV) increased from 28.1 ± 18.0 degrees to 67.6 ± 25.0 degrees (both p < 0.05). Patients with left-sided pathways demonstrated similar changes in which Δφ̄ (LV-RV) decreased from 2.9 ± 10.8 degrees to −26.5 ± 9.0 degrees and Δ φ 0 (LV-RV) decreased from 3.4 ± 14.2 degrees to −27.4 ± 17.9 degrees (both p < 0.05). On the other hand, the site of latest phase angle, or fusion, shifted away from the bypass pathway and the preexcited ventricle. Scintigraphic phase analysis, as electrophysiologic study, reveals dynamic changes with augmented preexcitation during atrial pacing. The parallel in image and electrophysiologic studies provides a physiologic basis for the scintigraphic method, which seeks to localized electrophysiologic foci on the basis of the mechanical sequence. This study makes no effort to assess clinical utility of the phase method. Yet it does demonstrate that phase analysis may be nondiagnostic or ambiguous in sinus rhythm, in the absence of maximum preexcitation. Scintigraphy may complement electrophysiologic catheter mapping in the evaluation of accessory pathways in patients with preexcitation. Atrial pacing may aid the scintigraphic assessment of preexcitation and localization of the accessory pathway in some patients.

Value of the resting 12 lead electrocardiogram and vectorcardiogram for locating the accessory pathway in patients with the Wolff-Parkinson-White syndrome.

The resting 12 lead electrocardiogram and vectocardiogram were reviewed in 47 patients with the Wolff-Parkinson-White syndrome (a) who had pre-excitation on the resting 12 lead electrocardiogram, (b) who had a single anterograde conducting accessory pathway assessed and located during preoperative electrophysiological study and during epicardial mapping at operation, and (c) in whom surgical division of the accessory pathway resulted in loss of pre-excitation. The site of the accessory pathway established during operation was compared with that established by evaluating the polarity of the delta wave and QRS complex on the resting 12 lead electrocardiogram. The electrocardiogram was assessed by the Rosenbaum criteria (Wolff-Parkinson-White type A, left-sided pathway; or type B, right-sided pathway), the Gallagher criteria (atrial pacing resulting in maximal pre-excitation), and the World Health Organisation criteria (a composite of previous studies). The Gallagher and World Health Organisation criteria were derived from patients demonstrating maximal pre-excitation that often required atrial pacing. The present study was designed to determine whether these criteria could be accurately applied to the resting 12 lead electrocardiogram on which the degree of pre-excitation was variable. The Rosenbaum criteria correctly identified a left sided accessory pathway in 26 of 34 patients and a right-sided accessory pathway in nine of 13 patients. The Gallagher and World Health Organisation criteria correctly identified the location in only 15 (32%) of the 47 patients. The resting vectorcardiogram was inaccurate for locating the accessory pathway. Although published criteria are useful for identifying the site of the accessory pathway from an electrocardiogram obtained when rapid atrial pacing is being used to achieve maximal pre-excitation, they are not suitable for identifying the exact site of an accessory pathway from the resting 12 lead electrocardiogram.

Concordance of distinguishing electrocardiographic features during sinus rhythm with the location of accessory pathways in the Wolff-Parkinson-White syndrome

Knowledge of the location of accessory pathways in patients with Wolff-Parkinson-White (WPW) syndrome is pertinent to patient management. Despite the recognition that features of delta waves present during maximal preexcitation reflect ventricular activation at different sites around the anulus fibrosus, the value of electrocardiographic patterns observed during sinus rhythm, when ventricular preexcitation is often not maximal for identifying accessory pathway locations, has not been determined. In this study, 12-lead electrocardiograms recorded during sinus rhythm from 66 patients with WPW syndrome were analyzed for delta-wave polarity, QRS axis in the frontal plane, the pattern of precordial R-wave transition, and concordance between electrocardiographic patterns and the site of the accessory pathway determined using catheter and intraoperative computer mapping. Electrocardiograms from patients with left lateral sites showed negative delta waves in leads I or aVL, a normal QRS axis and early precordial R-wave transition (20 of 24 patients); left posterior sites manifested negative delta waves in II, III and aVF and a prominent R wave in V 1 (14 of 16 patients); posteroseptal sites had negative delta waves in II, III and aVF, a superior QRS axis and an R < S in V 1 (all 16 patients); right free wall locations manifested negative delta waves in aVR, a normal QRS axis, and R-wave transition in V 3-V 5 (6 of 6 patients); and anterior septal sites had negative delta waves in V 1 and V 2, a normal QRS axis, and R-wave transition in V 3-V 5 (4 of 4 patients). Characteristic electrocardiographic patterns were not observed in 5 patients because of insufficient preexcitation. Each had a left lateral or left posterior pathway. Overall, the proposed electrocardiographic criteria derived during sinus rhythm identified correctly the accessory pathway location in 60 of 66 patients (91%). Thus, the electrocardiogram provides the physician with a reliable noninvasive means of regionalizing the location of accessory pathways in patients with WPW syndrome.

The preexcitation index: an aid in determining the mechanism of supraventricular tachycardia and localizing accessory pathways.

In this study we sought to determine whether characteristics of ventricular-induced atrial preexcitation during reciprocating tachycardia could help differentiate atrioventricular (AV) nodal reentry from orthodromic AV reentry using an accessory pathway and to identify the site of accessory pathways in patients with Wolff-Parkinson-White syndrome. Fifty-five patients with orthodromic AV reciprocating tachycardia and 22 patients with AV nodal reentrant tachycardia were studied with standard electrophysiologic techniques. There were 24 left free wall, 23 posterior septal, seven anterior septal, and one right free wall accessory pathways. Progressively premature right ventricular complexes (V2) were introduced during reciprocating tachycardia (V1V1). The V1V1 interval during tachycardia minus the longest V1V2 at which atrial preexcitation occurred defined a preexcitation index (PI). Atrial preexcitation occurred in 49 of 55 (89%) patients with AV reentry compared with only three of 22 (14%) patients with AV nodal reentry (p less than .001). In the three patients with AV nodal reentry who demonstrated atrial preexcitation, the PI was distinct from that of the septal pathways and was in the upper range of values for left free wall pathways. The percentage of tachycardias demonstrating atrial preexcitation was not different between the free wall and septal pathways, but His bundle activation was visible at the time of atrial preexcitation in only six of 17 (35%) left free wall compared with 13 of 16 (81%) posterior septal and seven of seven (100%) anterior septal pathways (p less than .05 free wall vs posterior or anterior septal).(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous computer mapping to facilitate intraoperative localization of accessory pathways in patients with Wolff-Parkinson-White syndrome

Sixteen patients with the Wolff-Parkinson-White syndrome underwent simultaneous intraoperative computer mapping from multiple sites before surgical division of the accessory pathways. A 16-bipolar electrode band was positioned around the atrioventricular groove. Ventricular epicardial electrograms from single beats were recorded simultaneously during atrial pacing, resulting in maximal preexcitation, and atrial electrograms were recorded during orthodromic supraventricular tachycardia. Four-level transmural plunge needle electrodes were used concomitantly in 3 patients. Electrograms were processed separately using a guarded signal conditioner that isolates, amplifies, filters and analog-to-digitally converts synchronously at 2 kHz with 12-bit accuracy. Digital data were transmitted by fiber optics to a high-density digital recorder and processed with a computer having rapid interactive graphics. Results in the 16 patients revealed 20 distinct Kent bundles. Two patients had only nosustained supraventricular tachycardia induced intraoperatively and 1 patient manifested intermittent anterograge ventricular preexcitation. Multiple pathways were identified in 4 patients. This simultaneous multiple electrode mapping procedure facilitates intraoperative mapping by requiring only a single beat for analysis of anterograde and retrograde activation times, decreases cardiac manipulation during mapping and obviates the need for cardiopulmonary bypass, and permits analysis of transmural activation patterns. This approach decreases markedly the time required for mapping and permits accurate study of nonsustained arrhythmias as well as rapid identification of multiple accessory pathways.

Attempted nonsurgical electrical ablation of accessory pathways via the coronary sinus in the Wolff-Parkinson-White syndrome

Previous canine experiments suggested that transvenous catheters placed in the coronary sinus could be used to deliver limited energy shocks, resulting in fibrosis in the atrial wall and coronary sulcus with sparing of the coronary artery. From the distribution of the fibrosis, it appeared that this approach could be used for attempted ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome. Eight patients with symptomatic Wolff-Parkinson-White syndrome underwent electrophysiologic testing with attempted ablation of 10 accessory pathways. Shocks were limited to 40 to 80 J, except in one patient who received shocks of 100 and 150 J. From 2 to 26 shocks were given to each accessory pathway. All the accessory pathways were blocked completely immediately after the shocks. Subsequently, evidence of accessory pathway conduction recurred in each patient. Three had early promise of long-term improvement after the procedure, with prolongation of the refractory periods of the accessory pathways during the remainder of the initial hospitalization. Several weeks later, however, there was evidence of return toward original values in two of these. Another patient who appeared not to benefit during her initial hospitalization returned 7 weeks later with very depressed accessory pathway conduction, possibly due to developing fibrosis. The only significant complication occurred in the patient receiving shocks of 100 and 150 J; he had apparent rupture of the coronary sinus requiring pericardial drainage. In two patients in whom nonsurgical ablation was not successful, intraoperative mapping showed that the accessory pathway was located in an area of fibrosis at the site of the attempted ablation. In summary, nonsurgical electrical ablation of accessory pathways via the coronary sinus may be successful using limited energy levels in a few patients. The procedure remains experimental, and widespread application must await more effective means of delivering the shocks.

Evaluation of noninvasive tests for identifying patients with preexcitation syndrome at risk of rapid ventricular response

Intermittent preexcitation, block in the accessory pathway after intravenous injection of ajmaline or procainamide, and block in the accessory pathway during exercise usually exclude a short antegrade refractory period of an accessory pathway in patients with the Wolff-Parkinson-White syndrome. This report describes three patients with these findings suggestive of a relatively long antegrade effective refractory period of the accessory pathway in whom life-threatening ventricular response occurred during atrial fibrillation. In the first patient with a pattern of intermittent preexcitation, rapid ventricular response with wide QRS was present during atrial fibrillation. In the second patient in whom preexcitation disappeared after intravenous injection of ajmaline or procainamide as well as during exercise testing, atrial pacing showed 1:1 conduction over the accessory pathway at a cycle length of 220 msec and the shortest R-R interval during induced atrial fibrillation was 190 msec. The third patient, with no evidence of preexcitation during sinus rhythm, presented antidromic reciprocating tachycardia and atrial fibrillation with life-threatening ventricular response, the minimal R-R interval being 220 msec. Noninvasive tests in the preexcitation syndrome lack sufficient prognostic sensitivity. The evaluation of ventricular response during induced atrial fibrillation represents the most reliable means of identifying such patients at risk.

Adenosine: electrophysiologic effects and therapeutic use for terminating paroxysmal supraventricular tachycardia.

Adenosine was administered intravenously to 17 patients undergoing intracardiac electrophysiologic studies. At a mean dose of 179 +/- 88 micrograms/kg (+/- SD), adenosine suppressed sinus node automaticity and depressed atrioventricular (AV) nodal conduction. These effects were less than 20 sec in duration and were not influenced by muscarinic blockade with atropine (0.02 to 0.03 mg/kg). Adenosine at this dose had no effect on antegrade conduction over accessory pathways in patients with Wolff-Parkinson-White syndrome. No independent hemodynamic effects were observed. In six patients, adenosine was administered intravenously during stimulation-induced paroxysmal supraventricular tachycardia. In the five patients in whom the reentry loop of their tachycardia included the AV node, adenosine at a mean dose of 83 +/- 35 micrograms/kg (+/- SD) terminated their tachycardia within 20 sec after peripheral intravenous injection. The dose of adenosine required to terminate these tachycardias did not produce manifest sinus node suppression, and sinus rhythm promptly resumed in all patients. Adenosine did not terminate either supraventricular tachycardia due to intra-atrial reentry or atrial flutter, but did produce transient AV block during these arrhythmias. Our findings demonstrate that the human sinus and AV nodes are sensitive to physiologic doses of adenosine and that adenosine may be used safely and effectively to terminate acute episodes of supraventricular tachycardia that involve the AV node in the reentry pathway.

Effects of verapamil on the electrophysiologic properties of the accessory pathway in patients with the Wolff-Parkinson-White syndrome

The effects of intravenous verapamil on the electrophysiologic properties of the accessory pathway in 12 patients with symptomatic Wolff-Parkinson-White syndrome were studied using intracardiac electrical recordings. In 11 of the 12 patients it was possible to induce a reentrant supraventricular tachycardia with programmed atrial or ventricular pacing. After verapamil it was still possible to induce supraventricular tachycardia in 6 of the 11 patients; however, the mean cycle of length of the tachycardia increased from a control value of 330 ± 20 ms (mean ± standard error of mean) to 369 ± 21 ms (p < 0.05). Although verapamil had no significant effect on the anterograde refractory period of the accessory pathway as measured by the extrastimulus technique, it significantly increased maximal 1:1 atrioventricular (AV) conduction through the accessory pathway to incremental high rate atrial pacing in 10 of the 12 patients (control value 227 ± 10 beats/min, value after verapamil 258 ± 14 beats/min, p < 0.001). In 4 patients in whom episodes of atrial fibrillation could be compared before and after verapamil, the drug decreased the average R-R interval from a control value of 327 ± 27 ms to 282 ± 28 ms (p < 0.05) and decreased the shortest R-R interval between preexcited beats from a control value of 237 ± 21 ms to 209 ± 18 ms (p < 0.05). It is concluded that in patients with symptomatic Wolff-Parkinson-White syndrome, verapamil may increase the ventricular response through the accessory pathway if atrial fibrillation occurs. This finding, which is of potential clinical significance, could not have been predicted from conventional anterograde refractory period estimations.

Effect of isoproterenol on the anterograde refractory period of the accessory pathway in patients with the Wolff-Parkinson-White syndrome

To evaluate the effect of beta adrenergic stimulation on the duration of the anterograde refractory period of the accessory pathway, isoproterenol was infused in seven patients with the Wolff-Parkinson-White syndrome. In two patients the effect of isoproterenol was studied during long-term oral amiodarone administration. To avoid rate-related changes induced by isoproterenol, the anterograde refractory period of the accessory pathway was determined using the single test stimulus method at identical basic cycle lengths. Isoproterenol shortened the anterograde refractory period of the accessory pathway in six of the seven patients studied. In two of the three patients with an initial anterograde refractory period of the accessory pathway of equal to or less than 290 ms, shortening measured 30 ms. In three patients having an anterograde refractory period of the accessory pathway of more than 290 ms, isoproterenol abbreviated these values by 30, 60 and 80 ms, respectively. The greatest amount of shortening was observed in patients having the longest initial values for the anterograde refractory period of their accessory pathway. In the two patients receiving oral amiodarone therapy, isoproterenol shortened the anterograde refractory period of the accessory pathway by 180 and 60 ms, respectively, indicating that the effect of isoproterenol can not be prevented by long-term oral amiodarone administration. Our observations may be of importance in patients with the Wolff-Parkinson-White syndrome and atrial fibrillation. They suggest that beta adrenergic stimulation induced by hypotension or anxiety may result in shortening of the anterograde refractory period of the accessory pathway, leading to increased ventricular rates during atrial fibrillation.

Effect of lidocaine on atrioventricular response via the accessory pathway in patients with Wolff-Parkinson-White syndrome.

SUMMARY Electrophysiologic effects of i.v. lidocaine were evaluated in 10 patients with Wolff-Parkinson-White (WPW) syndrome during atrial fibrillation (AF) (eight of 10) or programmed atrial stimulation (nine of 10). The shortest RR intervals during AF were 190–415 msec (mean 271.8 ± 64.5 msec) before lidocaine and decreased to 250.0 ± 85.4 msec (range 180-435 msec, p = NS) after the drug. In six of eight patients, the shortest RR interval decreased and in the remaining two patients it increased by 20 msec after lidocaine. After lidocaine, the average RR intervals during AF for all eight patients decreased from 351.1 ± 45.9 msec to 335.6 ± 68.0 msec (p = NS). After lidocaine, the RR inverval shortened in five of eight patients, lengthened in two and did not change In one. In two of eight patients, acceleration of ventricular rate after lidocaine was accompanied by hemodynamic deterioration, necessitating DC cardioversion in one. The control effective refractory period of the accessory pathway (ERP-AP) was 300 msec or less in all patients, and lidocaine prolonged this variable in only one case. In the remaining patients, after lidocaine the ERP-AP either shortened (two of nine), did not change (two of nine) or atrial refractoriness precluded its determination. Similarly, during incremental pacing, the atrial cycle length that produced block in the AP shortened in five patients, lengthened in one and did not change in the others. In patients with WPW syndrome and relatively short ERP-AP (i.e., 300 msec), lidocaine generally has no significant effect or produces acceleration of ventricular response during AF. In patients with AF and a rapid ventricular rate due to antegrade conduction over the AP, lidocaine is unlikely to have beneficial effects and may be deleterious.

Electrophysiological diagnosis of participation of accessory pathway in patients with paroxysmal supraventricular tachycardia.

Electrophysiological studies were performed on 34 patients whose reentrant circuit of paroxysmal supraventricular tachycardia (PSVT) involved normal atrioventricular (AV) conduction system as the antegrade limb and either overt (25 patients) or concealed (9 patients) accessory AV pathway as the retrograde limb. The diagnosis of this mechanism was made by one or more of the following: 1) eccentric retrograde atrial activation sequence; 2) effect of bundle branch block on ventriculoatrial (VA) conduction time; 3) paradoxically premature atrial capture; 4) atrial capture by premature ventricular stimulation of VA conduction time with retrograde during PSVT; 5) no significant prolongation of VA conduction time with retrograde atrial activation sequence to that of PSVT during incremental and premature ventricular stimulation; 6) shortening of cycle length with constant H-V and V-A intervals after atropine administration. The participation of accessory pathway in PSVT circuit should be decided by as many of the above-mentioned findings or procedures as possible for optimal therapy. Electrophysiological studies have led to the recognition that accessory pathway, functionally silent during antegrade conduction, is responsible for some patients with PSVT. If the mechanisms of PSVT were more carefully analyzed, the recognition of PSVT cases involving accessory pathway would increase.

Enhanced atrioventricular nodal conduction in a patient with dual extranodal pathways

A patient was admitted to the hospital with wide complex tachycardia and a history of recurrent palpitations. Electrophysiologic studies showed evidence of dual atrioventricular (AV) accessory pathways. One proved to be an anteroseptal (possible right anterior) pathway probably capable of only unidirectional conduction. The other pathway was in the posterior septum and conducted only in the retrograde direction. The tachycardia circuit involved anterograde conduction via either the AV node-His axis or the anteroseptal pathway and retroconduction over the posteroseptal accessory pathway. In addition, enhanced AV nodal conduction coupled with two accessory AV nodal pathways has rarely been described in English medical literature. Previous reports have carefully described anatomic, electrocardiographic, and electrophysiologic evidence of more than one accessory pathway in patients with the Wolff-Parkinson-White syndrome. The introduction of surgical techniques for ablation of an accessory pathway demands precision in the electrophysiologic evaluation of patients with ventricular preexcitation. Reported herein is a patient with the unique finding of two extranodal accessory pathways and enhanced atrioventricular (AV) nodal conduction (or AV nodal bypass).

Multiple accessory pathways in patients with the pre-excitation syndrome.

We have studied 135 patients with the pre-excitation syndrome and have demonstrated evidence of multiple accessory pathways in 20 patients. Five patients had two distinct accessory atrioventricular (A-V) connections, associated with enhanced A-V node conduction in one patient. Twelve patients had a single accessory A-V connection associated with enhanced A-V conduction. In one of these there was an additional fasciculo-ventricular connection. One patient had an accessory A-V connection associated with a nodoventricular bundle. Two patients had fasciculo-ventricular connections combined with enhanced A-V conduction. The latter two patients had electrocardiograms suggestive of a complete accessory A-V connection. Patients with enhanced A-V conduction had shorter cycle lengths during reciprocating tachycardia, primarily because of a short A-H during the dysrhythmia, than those without such conduction. In addition, patients with enhanced A-V conduction demonstrated more rapid conduction from atrium to His bundle during induced atrial fibrillation and two developed life-threatening ventricular responses during atrial fibrillation. A nodo-ventricular pathway was documented to participate in reciprocating tachycardia in one patient. Surgery was undertaken in 13 patients. In 11, the intraoperative mapping studies confirmed the preoperative predictions. In two patients, the presence of a second accessory A-V connection was documented after ablation of one.

THE PROGNOSIS OF THE WOLFF-PARKINSON-WHITE SYNDROME

Excerpt Many authors, including Wolff, Parkinson and White,1consider the prognosis of the Wolff-Parkinson-White syndrome (characterized by White et al.1essentially as: (1) a short P-R interval, (2)...