Signal averaging in Wolff-Parkinson-White syndrome: evidence that fractionated activation is not necessary for body surface high-frequency potentials.

It is commonly assumed that the presence of high frequency components in body surface potentials implies that fractionated activation fronts, caused by heterogeneously viable tissue, are present in the heart. However, it is possible that non-fractionated activation fronts can also give rise to high frequency surface potentials and that the relative amount of high frequency power is related to the complexity of the activation sequence. In a test of this idea, averaged body surface potentials were recorded during the entire QRS complex of nine Wolff-Parkinson-White (WPW) patients in situations in which fractionated activation fronts should not have been present, but which represent increasing degrees of complexity of ventricular activation: (1) postoperative ectopic pacing from subepicardial wires placed during surgery, when a single coherent activation front was present throughout most of the QRS; (2) Preoperative preexcited rhythm, when a single coherent activation front was present for one portion of the QRS (the delta wave); and (3) postoperative normal rhythm, when two or more activation fronts were present in the ventricles throughout most of the QRS. For comparison, averaged body surface potentials were also analyzed during the last 40 ms of the QRS complex and the ST segment of 14 postinfarction patients with chronic ventricular tachycardia. In the patients with WPW syndrome, relatively high frequency content increased (attenuation -36.7 vs -27.2 vs -18.3 dB) and QRS width decreased (160.7 vs 125.9 vs 94.1 ms) significantly from paced to preoperative to postoperative beats. Significant high frequency content was present in all cases, showing that coherent activation fronts can give rise to high frequencies. Interestingly, the postoperative QRS of WPW patients contained a larger proportion of high frequency power than did the late potentials of the patients with ventricular tachycardia. Thus, while the presence of late fractionated body surface potentials may be a marker for ventricular tachycardia, these potentials by themselves do not necessarily signify that the underlying cardiac activation giving rise to these signals is fractionated.

Occurrence of atrial fibrillation in patients with paroxysmal supraventricular tachycardia due to atrioventricular nodal reentry.

The occurrence of atrial fibrillation in patients with paroxysmal supraventricular tachycardia (PSVT) has been well documented when PSVT is secondary to atrioventricular reentry, but not when PSVT is secondary to atrioventricular nodal reentry (AVNRT). Seventeen patients with AVNRT were followed using transtelephonic electrocardiogram monitoring to document symptomatic tachycardias. The median length of telephone monitor surveillance was 357 days. Fifteen of 17 patients transmitted electrocardiograms that showed PSVT. Three of 17 patients (18%) transmitted electrocardiograms that showed atrial fibrillation. A transition from PSVT into atrial fibrillation was not recorded, but all three did have PSVT recorded on other days of follow-up. We report the occurrence of atrial fibrillation in patients with AVNRT and that its incidence is higher than expected for the general population.

Importance of preexcited QRS morphology during induced atrial fibrillation to the diagnosis and localization of multiple accessory pathways.

The present investigation evaluates the ability of several electrocardiographic (ECG) and electrophysiologic methods to identify multiple accessory pathways in 47 patients in whom the presence and sites of multiple accessory pathways were confirmed intraoperatively. To establish ECG features that suggested the presence of multiple accessory pathways in these patients, we initially studied the 12-lead ECG during maximal preexcitation in 101 patients with single accessory pathways. Distinctive 12-lead ECG patterns were noted for six defined anatomic areas around the right and left atrioventricular groove. Multiple preexcited QRS morphologies, each typical for a separate accessory pathway, and atypical preexcited QRS morphologies were recorded during atrial fibrillation in 31 of 47 (66%) patients with multiple accessory pathways. By comparison, the ECG during sinus rhythm and rapid atrial pacing identified 14 (32%) and 26 (55%) of the patients, respectively. In 12 (26%) patients in whom evidence for multiple accessory pathways was absent from endocardial mapping data, atrial fibrillation provided the diagnosis. In five (11%) patients, atrial fibrillation was the only method that demonstrated the presence of multiple accessory pathways. A combination of ECG findings during atrial fibrillation and rapid atrial pacing plus endocardial mapping data identified 43 (91%) of the patients with multiple accessory pathways. There were two unique fusion patterns on the 12-lead ECG that were characteristic of specific multiple accessory pathway combinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Utility of introducing ventricular premature complexes during reciprocating tachycardia in specifying the location of left free wall accessory pathways.

The usefulness of the response to single and double ventricular premature complexes (VPCs) introduced during reciprocating tachycardia (RT) in predicting the location of a left free wall accessory pathway was studied in 55 patients with the Wolff-Parkinson-White syndrome. One VPC introduced from the right ventricle into narrow QRS RT when the His bundle was refractory resulted in retrograde atrial preexcitation in 25 of 55 (45%) patients, while 30 (55%) showed no preexcitation. Double VPCs produced retrograde atrial preexcitation in 9 of 26 patients not responding to a single VPC. No difference in RT cycle length, AH, HV or ventriculoatrial intervals was found between those patients who did or did not show retrograde atrial preexcitation. The response to single and double VPCs during RT was related to the location of the AP. The average distance of the AP from the crux determined by intraoperative epicardial mapping in the 41 patients who underwent surgery was 2.7 +/- 0.7 mapping units (left posterolateral region) in patients showing retrograde atrial preexcitation with a single VPC, 3.6 +/- 0.7 units (at the lateral left ventricular margin) in those responding to double VPCs and 4.3 +/- 0.8 units (beyond the LV margin) in those showing no response. Left bundle--branch block (LBBB) aberrancy during RT resulted in an average 60 +/- 14 ms prolongation of the ventriculoatrial interval in 40 patients, including 5 in whom LBBB was seen only after procainamide infusion. VPCs introduced into LBBB RT resulted in significant retrograde atrial preexcitation in 6 additional patients in whom no response during normal QRS RT was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Procainamide infusion test: inability to identify patients with Wolff-Parkinson-White syndrome who are potentially at risk of sudden death.

Persistence of preexcitation in sinus rhythm with procainamide infusion has been reported to occur in patients with a short anterograde accessory pathway effective refractory period (AERPAP) and this test has been proposed as a reliable noninvasive method to identify patients with the Wolff-Parkinson-White syndrome who are at risk of sudden death. However, sudden death correlates best with a shortest preexcited RR interval during atrial fibrillation (SRRPE) of 260 msec or less. We infused 10 to 12 mg/kg procainamide to 56 patients to determine whether persistence or loss of preexcitation in sinus rhythm identified patients with SRRPEs of 260 or less or greater than 260 msec, respectively. Atrial fibrillation was induced in 53 patients. Of these, 32 patients had persistence of preexcitation with procainamide infusion and SRRPE in this group of patients was shorter than that in patients in whom preexcitation was lost (194 +/- 44 vs 235 +/- 55 msec, p less than .05). However, preexcitation persisted after procainamide infusion in only 31 of 46 (67%) patients with SRRPEs of 260 msec or less. Furthermore, 15 of 21 patients who lost preexcitation had SRRPEs of 260 msec or less and two of these patients had a history of ventricular fibrillation. The correlation between AERPAP and SRRPE was studied in a separate group of 79 patients with single accessory pathways. There was a significant (p less than .001) but poor (r = .58) correlation between these two variables. Thus, the procainamide test regarding accessory pathway refractoriness often cannot be extrapolated to SRRPE.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial lead perforation: a case report.

We report a patient in whom a chronic atrial lead perforated the right atrium and the right lung. This resulted in an hemopneumothorax and pneumomediastinum which was clearly documented by a chest computerized tomographic scan. The finding of pneumomediastinum should suggest atrial lead perforation. The utility of the chest computerized tomographic scan in diagnosing lead perforation is well illustrated by this case.

Beta-blocker therapy for the Wolff-Parkinson-White syndrome.

Two types of arrhythmias are associated with the Wolff-Parkinson-White syndrome: those in which the accessory pathway is a required part of the reentrant circuit, e.g., orthodromic atrioventricular reciprocating tachycardia, and those that conduct over the accessory pathway but do not require its activation for maintenance of tachycardia, e.g., atrial flutter/fibrillation. Increased sympathetic tone shortens the refractoriness of atrial and ventricular tissue; however, conduction in the atrium and ventricle is not considered the limiting factor for maintenance of atrioventricular reciprocating tachycardia or conduction over the accessory pathway in atrial arrhythmias. Intravenous beta-adrenergic blockers given to patients in the resting state have a minimal to moderate effect in depressing atrioventricular nodal conduction, but have little or no effect on accessory pathway refractoriness or conduction in most patients. In patients presenting with atrioventricular reentry, intravenous administration of beta-adrenergic blocking drugs often is not effective to terminate tachycardia. However, long-term oral therapy with these agents may be beneficial, especially in patients in whom enhanced sympathetic tone is responsible for the initiation or maintenance of tachycardia.

Familial occurrence of accessory atrioventricular pathways (preexcitation syndrome).

Accessory atrioventricular pathways, the anatomical structures responsible for the preexcitation syndromes, may result from a developmental failure to eradicate the remnants of the atrioventricular connections present during cardiogenesis. To study whether preexcitation syndromes could also be transmitted genetically, we determined the prevalence of preexcitation in the first-degree relatives of 383 of 456 consecutive patients (84 percent) with electrophysiologically proved accessory pathways. We compared the observed prevalence of preexcitation among the 2343 first-degree relatives with the frequency reported in the general population (0.15 percent). For 13 of the 383 index patients (3.4 percent), accessory pathways were documented in one or more first-degree relatives. At least 13 of the 2343 relatives identified (0.55 percent) had preexcitation; this prevalence was significantly higher than that in the general population (P less than 0.0001). Identification of affected relatives may have been incomplete because clinical information was obtained only about symptomatic relatives. Patients with familial preexcitation have a higher incidence of multiple accessory pathways and possibly an increased risk of sudden cardiac death. Our data suggest a hereditary contribution to the development of accessory pathways in humans. The pattern of inheritance appears to be autosomal dominant.

Comparison of survival of amiodarone-treated patients with coronary artery disease and malignant ventricular arrhythmias with that of a control group with coronary artery disease.

Although amiodarone is effective in the treatment of ventricular arrhythmias, it is associated with serious toxic effects. In addition, the prognosis of patients with malignant ventricular arrhythmias and coronary artery disease treated with amiodarone remains poor. The survival of 54 consecutive patients with angiographically documented coronary artery disease and symptomatic ventricular tachycardia or ventricular fibrillation treated with amiodarone was compared with that of 5,125 medically treated patients with coronary artery disease. The amiodarone group was older, with worse left ventricular function and more peripheral and cerebrovascular disease. The 1 year survival probability was 0.73 for the amiodarone group and 0.94 for the control coronary artery disease group. At 2 years of follow-up, the survival probabilities were 0.60 and 0.90 for the amiodarone and the control group, respectively. When the survival curves were adjusted for group differences in baseline prognostic characteristics (integrated as a previously published hazard score), there was no difference in the prognosis of the two groups. These findings suggest that treatment with amiodarone of malignant ventricular arrhythmias associated with coronary artery disease maintains patients on an underlying survival curve determined by the degree of myocardial dysfunction, clinical characteristics and coronary anatomy, and that amiodarone does not have a deleterious effect on survival.

Cryosurgical versus catheter ablation of the atrioventricular junction.

Results of catheter ablation of the atrioventricular (AV) junction in 41 patients were compared with results of cryosurgical ablation in 42 patients. Mean follow-up was 29 months among patients who underwent catheter ablation and 53 months among those who underwent cryosurgical ablation. In both groups complete heart block was produced in most patients (88% in the catheter ablation group, 86% in the cryosurgery group), and similar proportions of patients continued to receive antiarrhythmic drugs (27% in the catheter ablation group, 36% in the cryosurgery group). However, the short-term morbidity rate was significantly lower among patients who underwent catheter ablation (12% vs 42%) (p = 0.004). Long-term mortality and morbidity rates were not significantly different; most deaths were related to underlying cardiopulmonary disease and morbidity to problems with permanent pacemakers. Both catheter ablation and cryosurgical ablation of the AV junction are effective in creating complete AV block and controlling supraventricular tachycardia in medically refractory patients. Because catheter ablation is associated with lower short-term morbidity and avoids the need for a major surgical procedure, it is preferable to cryosurgical ablation of the AV junction when permanent abolition of AV conduction is necessary.

Frequency, diagnosis and clinical characteristics of patients with multiple accessory atrioventricular pathways.

Multiple accessory atrioventricular (AV) pathways were documented in 52 of 388 patients (13%) who underwent detailed electrophysiologic evaluation. Multiple AV pathways were identified during intraoperative mapping or electrophysiologic study by different patterns of ventricular preexcitation during atrial fibrillation, flutter or atrial pacing with different delta-wave morphologic and ventricular activation patterns; different sites of atrial activation during right ventricular pacing or orthodromic reciprocating tachycardia; or preexcited reciprocating tachycardia using a second pathway as the retrograde limb of the tachycardia. A logistic model was used to determine which clinical, electrocardiographic and electrophysiologic variables were associated with multiple AV pathways. Right free-wall and posteroseptal accessory AV pathways were more common in patients with multiple AV pathways and were frequently associated. Multivariate logistic regression identified Ebstein's anomaly, and a history of preexcited reciprocating tachycardia as significant variables (p less than 0.0001). Pathway location was not subjected to statistical analysis because of confounding variables.

Value of the 12-lead electrocardiogram in discriminating atrioventricular nodal reciprocating tachycardia from circus movement atrioventricular tachycardia utilizing a retrograde accessory pathway.

The value of the 12-lead electrocardiogram for distinguishing atrioventricular (AV) nodal reciprocating tachycardia from circus movement AV tachycardia utilizing a retrograde accessory pathway was studied in 100 patients with narrow QRS complex tachycardia. Intracardiac electrograms showed AV nodal reciprocating tachycardia in 40 patients and circus movement AV tachycardia in 60. The 12-lead electrocardiograms recorded during tachycardia were randomly sorted and reviewed by 4 experienced cardiac electrophysiologists who were blinded to the diagnosis associated with each tracing, the relative proportion of each arrhythmia and the hypotheses to be tested. Each reviewer was asked to indicate the location of the P wave relative to the QRS complex, electrical axis of the P wave in the frontal and horizontal planes and presence or absence of QRS alternation, and to interpret the most likely mechanism. The performance of published electrocardiographic criteria to differentiate AV nodal reciprocating tachycardia from circus movement AV tachycardia was evaluated. The overall accuracy of the reviewers' interpretations was 75%, similar to the accuracy of the predefined criteria when applied by these observers (71% correct, difference not significant). Interobserver agreement of reviewer interpretations was 76% and the intraobserver agreement was 78%. Features associated with circus movement AV tachycardia by univariable analysis were P waves after the QRS complex, faster tachycardia rates and QRS alternation. Multivariable analysis showed that only the location of the P wave relative to the QRS complex was independently associated with the mechanism of tachycardia (p = 0.002). QRS alternation was found by multivariate analysis to be associated with the rate but not the mechanism of the tachycardia.

Wolff-Parkinson-White syndrome and sudden cardiac death.

Every year, individuals with no history of heart disease succumb to sudden cardiac death (SCD). Pathologic examination of the hearts usually reveals various forms of heart disease as hypertrophic cardiomyopathy or coronary artery disease. In other cases, however, there is no obvious structural heart disease, and it is possible that some of these individuals died because of a cardiac arrhythmia involving an accessory pathway. If this were the case, the most likely scenario would be onset of atrioventricular reciprocating tachycardia (AVRT), degeneration of the AVRT into atrial fibrillation with a rapid ventricular response over the accessory pathway, and subsequent death caused by the development of ventricular fibrillation. Although these events have been documented, albeit rarely, during intracardiac electrophysiologic studies, in reality very little is known about the natural history of asymptomatic and untreated patients with Wolff-Parkinson-White (WPW) syndrome. In fact, SCD in a previously asymptomatic patient with WPW syndrome is probably relatively rare. Whether asymptomatic WPW patients should undergo electrophysiologic or pharmacologic testing to determine their 'potential' to develop serious cardiac arrhythmias is controversial. The present paucity of data concerning the natural history of WPW syndrome in asymptomatic patients militates against successful identification of those patients who are at risk for sudden death. Long-term prospective studies are necessary to clarify which asymptomatic patients with WPW syndrome require treatment.

The long R-P' tachycardias.

The family of tachycardias that are called long R-P' tachycardias represent a unique group of tachycardias which have been notably refractory to pharmacologic therapy in the past. On the surface electrocardiogram, the rhythms may be indistinguishable. It is only with careful electrophysiological evaluation in many cases that these rhythms can be sorted out. The differential diagnosis in these rhythms is important because with incessant tachycardia, ventricular dysfunction may be produced. In many of the instances of long R-P' tachycardias definitive and directed ablation of the tachycardia can be accomplished. New techniques involving catheter ablation and super-selective surgical dissection are now present which makes ablation of these tachycardias possible.

Computer-assisted intraoperative mapping of the entire ventricular epicardium in the Wolff-Parkinson-White syndrome.

Intraoperative mapping with a hand-held, roving electrode requires a sustained rhythm lasting 5 to 10 minutes. To overcome this limitation, a computerized mapping system that records from 60 epicardial electrodes simultaneously was used to study 16 patients with Wolff-Parkinson-White syndrome. A sock containing 6 rows of electrodes arranged concentrically from base to apex was place over the ventricles. The total time from placing the sock to analyzing the most basal row of electrode recordings was 5 minutes. A 39 X 44-mm plaque containing 56 electrodes was than placed across the atrioventricular (AV) groove for detailed simultaneous mapping of the ventricle and atrium in the preexcited region identified from the most basal row of sock electrodes. During plaque placement and recording, the remaining sock recordings were analyzed and a complete isochronal epicardial map was drawn. The plaque recordings were then analyzed. This technique rapidly detects early activation at the AV groove as do other computer systems using only a band of electrodes around the AV groove. Also, complete epicardial mapping supplied important additional information. One patient with a posterior paraseptal accessory pathway had ventricular epicardial breakthrough below the strip recorded by the AV band. When more than 1 early activation site was present along the AV groove, complete maps allowed multiple pathways to be differentiated from normal activation fronts ascending from the bundle branches. Complete epicardial maps allowed the study of rapidly changing or short-lived electrical events including isolated premature impulses, initiation and termination of reciprocating tachycardia by pacing, entrainment and changing degrees of fusion created by pacing during reciprocating tachycardia, and ventricular responses during atrial fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acute tachycardia on left ventricular adenine nucleotide levels and subsequent tolerance to ischemia.

Electrophysiologically guided surgical procedures for the ablation of supraventricular and ventricular dysrhythmias often require prolonged periods of tachycardia to complete intraoperative mapping studies. It is unknown whether tachycardia depletes the myocardium of high-energy compounds or alters subsequent tolerance to ischemia. In the present study, 12 anesthetized dogs were paced from the right ventricle at a cycle length of 250 msec for 60 minutes. In seven animals, drill biopsy specimens were taken from the left ventricular free wall for analysis of adenine nucleotide levels and their breakdown products before and after pacing and after 20 minutes of recovery from pacing. In the remaining five animals, the heart was made totally ischemic immediately after tachycardia and the time to the onset of ischemic contracture was determined and compared to that of five nonpaced control dogs. Acute tachycardia resulted in no significant reduction in adenine nucleotide levels compared to control values. Furthermore, in hearts rendered totally ischemic after tachycardia, the mean time to ischemic contracture was 65.6 +/- 1.3 minutes versus 63.6 +/- 2 minutes in nonpaced control animals (no significant difference). These data show that pacing-induced tachycardia in the normal heart does not decrease adenine nucleotide levels or affect subsequent tolerance to ischemia. These results may be clinically relevant to patients without coronary artery disease who undergo operative procedures necessitating prolonged periods of tachycardia for intraoperative mapping to identify the site of arrhythmogenesis.