Evaluation of patients with bundle branch block and "unexplained" syncope: a study based on comprehensive electrophysiologic testing and ajmaline stress

Impact of bundle branch block morphology on outcomes of patients with syncope and bifascicular block: A SPRITELY (POST 3) substudy

BACKGROUND

Permanent pacing is often considered for patients with syncope and bifascicular block.

OBJECTIVE

The purpose of this study was to determine whether QRS morphology or other electrocardiographic characteristics can identify patients who may benefit from permanent pacing.

METHODS

The Syncope: Pacing or Recording in the Later Years (SPRITELY) trial was a multicenter trial that randomized patients with bifascicular block and syncope (n = 115) to empiric pacemaker implantation vs implantable loop recorder (ILR) monitoring. In this SPRITELY subanalysis, baseline 12-lead electrocardiograms were evaluated for bundle branch block (BBB) morphology, QRS width, and PR and QT intervals and their impact on clinical outcomes was assessed.

RESULTS

There were 41 patients with left BBB (36%), 69 patients with right bundle branch block (RBBB) and left anterior fascicular block (60%), and 5 patients with RBBB and left posterior fascicular block (4%). Pacemaker implant compared with ILR was associated with a significant reduction of major study-related events (MSREs) in both patients with left BBB (23.8% vs 78.9%; P = .001) and those with RBBB (27% vs 72.9%; P < .0001). Similarly, a reduction of MSREs was observed in both patients with trifascicular block (23% vs 84.6%; P < .0001) and those with bifascicular block (26.6% vs 68.9%; P = .002). In the group randomized to ILR monitoring, the type of BBB was not a predictor of recurrent syncope (P = .30), bradycardia requiring pacemaker (P = .15), or MSREs (P = .42). The presence of PR interval prolongation or QRS width in this group did not predict MSREs (P = .22 and P = .96, respectively).

CONCLUSION

In patients with syncope and bifascicular block, pacemaker implantation reduces adverse events as compared with ILR monitoring, irrespective of the type of BBB or the presence of PR interval prolongation.

Advantages and disadvantages of drug challenge during electrophysiological study in patients with new left bundle branch block after transaortic valve implantation

AIMS

Electrophysiological study (EPS) is recommended in case of new-onset persistent left bundle branch block (NOP-LBBB) after transaortic valve implantation (TAVI) to identify patients at high risk of delayed atrioventricular block (D-AVB). We evaluated the added value of drug challenge, after normal baseline EPS, to predict D-AVB in such patients.

METHODS

We conducted a comparative single-centre study of two successive periods, during which we used baseline EPS alone (first period) or drug challenge in case of normal baseline EPS (second period), for patients with NOP-LBBB after TAVI. The primary endpoint was a composite of pacemaker use, documented D-AVB, cardiac syncope, sudden death, or delayed pacemaker implantation.

RESULTS

Among 736 patients with TAVI implantation between January 2016 and September 2019, 64 with NOP-LBBB were included. During the first period, 4/22 (18.2%) presented with a positive baseline EPS. After a mean (standard deviation [SD]) of 15.6 (8.3) months, 7/22 (31.8%) reached the primary endpoint. During the second period, 19/42 (45.2%) presented with a positive EPS. After a mean (SD) of 12.8 (3.5) months, 8/42 (19.0%) reached the primary endpoint. There was a tendency to increased sensitivity (42.9-87.5%; P = 0.12) and negative predictive value (77.8-95.7%; P = 0.15) of the EPS, respectively during the first to the second period. However, the specificity decreased (93.3-64.7%; P = 0.04).

CONCLUSION

Diagnostic yield improved with drug challenge in case of normal baseline EPS. However, the decrease in specificity led to a high rate of unnecessary pacemaker implantation.

Permanent pacemaker implantation in unexplained syncope patients with electrophysiology study-proven atrioventricular node disease

BACKGROUND

Syncope, whose cause is unknown after an initial assessment, has an uncertain prognosis. It is critical to identify patients at highest risk who may require a pacemaker and to identify the cause of recurrent syncope to prescribe proper therapy. Aim of this study was to evaluate the effect of permanent pacing on the incidence of syncope in patients with unexplained syncope and electrophysiology study-proven atrioventricular node disease.

MATERIAL AND METHODS

This was an observational study based on a prospective registry of 236 consecutive patients (60.20 ± 18.66 years, 63.1% male, 60.04 ± 9.50 bpm) presenting with recurrent unexplained syncope attacks admitted to our hospital for invasive electrophysiology study (EPS). The decision to implant a permanent pacemaker was made in all cases by the attending physicians according to the results of the EPS. 135 patients received the antibradycardia pacemaker (ABP), while 101 declined.

RESULTS

The mean of reported syncope episodes was 1.97 ± 1.10 (or presyncope 2.17 ± 1.50) before they were referred for a combined EP guided diagnostic and therapeutic approach. Over a mean follow-up of approximately 4 years (49.19 ± 29.58 months), the primary outcome event (syncope) occurred in 31 of 236 patients (13.1%), 6 of 135 (4.4%) in the ABP group as compared to 25 of 101 (24.8%) in the no pacemaker group (p < 0.001).

CONCLUSION

Among patients with a history of unexplained syncope, a set of positivity criteria for the presence of EPS defined atrioventricular node disease, identifies a subset of patients who will benefit from permanent pacing.

Fascicular heart blocks and risk of adverse cardiovascular outcomes: Results from a large primary care population

BACKGROUND

Fascicular heart blocks can progress to complete heart blocks, but this risk has not been evaluated in a large general population.

OBJECTIVE

The purpose of this study was to investigate the association between various types of fascicular blocks diagnosed by electrocardiographic (ECG) readings and the risk of incident higher degree atrioventricular block (AVB), syncope, pacemaker implantation, and death.

METHODS

We studied primary care patients referred for ECG recording between 2001 and 2015. Cox regression models were used to estimate hazard ratios (HRs) as well as absolute risks of cardiovascular outcomes.

RESULTS

Of 358,958 primary care patients (median age 54 years; 55% women), 13,636 (3.8%) had any type of fascicular block. Patients were followed up to 15.9 years. We found increasing HRs of incident syncope, pacemaker implantation, and third-degree AVB with increasing complexity of fascicular block. Compared with no block, isolated left anterior fascicular block (LAFB) was associated with 0%-2% increased 10-year risk of developing third-degree AVB (HR 1.6; 95% confidence interval [CI] 1.25-2.05), whereas right bundle branch block combined with LAFB and first-degree AVB was associated with up to 23% increased 10-year risk (HR 11.0; 95% CI 7.7-15.7), depending on age and sex group. Except for left posterior fascicular block (HR 2.09; 95% CI 1.87-2.32), we did not find any relevant associations between fascicular block and death.

CONCLUSION

We found that higher degrees of fascicular blocks were associated with increasing risk of syncope, pacemaker implantation, and complete heart block, but the association with death was negligible.

Bedside Electrophysiological Study Using a Temporary Pacemaker May Predict Recurrence of Atrioventricular Block After Transcatheter Aortic Valve Replacement

High-degree atrioventricular block (HAVB) or complete heart block (CHB) is a common complication associated with transcatheter aortic valve replacement (TAVR). However, some patients with HAVB/CHB recover with time. The results of electrophysiological studies (EPSs) using permanent pacemaker implantation (PPI) in patients with suspicious HAVB/CHB are considered controversial.This study aimed to evaluate whether HAVB/CHB induction at the bedside using a temporary pacemaker can predict recurrence in patients who had recovered from HAVB/CHB after TAVR.We enrolled a total of 11 patients who had recovered from HAVB/CHB and evaluated their electrophysiology using right ventricular pacing and/or procainamide administration.HAVB/CHB induction was positive. Three patients tested positive for HAVB/CHB, whereas 8 tested negative. The ejection fraction and the interval between HAVB/CHB onset and EPS were found to be significant. HAVB/CHB positive patients underwent PPI. A patient with a balloon-expandable valve tested positive just before recovery of CHB, but tested negative 5 days later and was included in the negative group. The 4 patients who tested negative received a cardiovascular implantable electric device (CIED). We observed HAVB/CHB in 2 patients who had previously tested positive after 3 months. Among those who tested negative, those with CIED had no HAVB/CHB, and others showed neither HAVB/CHB on electrocardiogram nor experienced syncope or sudden death.Our EPS revealed that HAVB/CHB induction may predict HAVB/CHB recurrence after TAVR. Valve type and EPS timing may affect the results.

Electrophysiology studies for predicting atrioventricular block in patients with syncope: A systematic review and meta-analysis

BACKGROUND

Syncope may be caused by intermittent complete heart block in patients with bundle branch block. Electrophysiology studies (EPS) testing for infra-Hisian heart block are recommended by the European Society of Cardiology syncope guidelines on the basis of decades-old estimates of their negative predictive values (NPVs) for complete heart block.

OBJECTIVE

The aim of this study was to determine the NPV of EPS for complete heart block in patients with syncope and bundle branch block.

METHODS

We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL without language restriction from database inception to October 2019 for Medical Subject Headings terms and keywords related to "syncope," "heart block," and "programmed electrical stimulation." A random effects meta-analysis was conducted with a primary outcome of the proportion of patients with a negative EPS who later presented with complete heart block, diagnosed with surface electrocardiographic (ECG) recordings vs continuous implantable cardiac monitor (ICM).

RESULTS

Ten reports contained 12 cohorts with 639 patients who met the inclusion criteria. The mean age was 69 ± 7 years; 35% ± 10% were women; and 85% of patients had bifascicular block. Seven cohorts recorded clinical outcomes with external ECG recordings, and 5 cohorts featured ICMs. The mean prespecified His-to-ventricle interval criterion was ≥70 ms. In studies featuring surface ECG recordings, there were 7% (95% confidence interval 7%-17%) patients who developed complete heart block compared with 29% (95% confidence interval 24%-35%) in the studies featuring ICM (P = .0001).

CONCLUSION

The NPV of EPS in patients with syncope and bundle branch block is 0.71, sufficiently low to question its use.

Canadian Cardiovascular Society Clinical Practice Update on the Assessment and Management of Syncope

Syncope is a symptom that occurs in multiple settings and has a variety of underlying causes, ranging from benign to life threatening. Determining the underlying diagnosis and prognosis can be challenging and often results in an unstructured approach to evaluation, which is ineffective and costly. In this first ever document, the Canadian Cardiovascular Society (CCS) provides a clinical practice update on the assessment and management of syncope. It highlights similarities and differences between the 2017 American College of Cardiology/American Heart Association/Heart Rhythm Society and the 2018 European Society of Cardiology guidelines, draws on new data following a thorough review of medical literature, and takes the best available evidence and clinical experience to provide clinical practice tips. Where appropriate, a focus on a Canadian perspective is emphasized in order to illuminate larger international issues. This document represents the consensus of a Canadian panel comprised of multidisciplinary experts on this topic with a mandate to formulate disease-specific advice. The primary writing panel wrote the document, followed by peer review from the secondary writing panel. The CCS Guidelines Committee reviewed and approved the statement. The practice tips represent the consensus opinion of the primary writing panel authors, endorsed by the CCS. The CCS clinical practice update on the assessment and management of syncope focuses on epidemiology, the initial evaluation including risk stratification and disposition from the emergency department, initial diagnostic work-up, management of vasovagal syncope and orthostatic hypotension, and syncope and driving.

Predictors of positive electrophysiological study in patients with syncope and bundle branch block: PR interval and type of conduction disturbance

BACKGROUND

Electrophysiological study (EPS) is indicated in patients with syncope and bundle branch block (BBB). Data about predictors of positive EPS in these patients is scarce.

OBJECTIVE

To assess clinical and electrocardiographic (ECG) predictors of positive EPS in patients with syncope and BBB.

METHODS

Observational single-center study that included all consecutive patients with syncope and BBB that underwent EPS from January 2011 to June 2017. Results of EPS were considered positive according to current ESC syncope guidelines.

RESULTS

During study period, 271 patients were included (64.9% male, age: 73.9 ± 12.2 years, number of syncopal episodes: 2.4 ± 2.5, LVEF: 56.1 ± 9.9%). Type of BBB: RBBB + LAFB/LPFB in 39.8%, isolated LBBB in 38.7% and isolated RBBB in 18.5% of the patients. Duration of QRS and PR interval were 141.9 ± 16.7 and 182.8 ± 52.2 milliseconds. EPS was positive in 41.7% of the patients. In multivariate analysis, conduction disturbance pattern and long PR interval (OR 8.6; 2.9-25; P < 0.0001) were predictors of positive EPS. Conduction disturbance patterns related with positive EPS were: BBB different than isolated RBBB (OR 15.2; 2.2-23.4; P = 0.005), LBBB or RBBB+long PR + left fascicular block (OR 4.5; 1.06-20.01; P < 0.042), and RBBB+left fascicular block compared with LBBB (OR 4.8; 1.2-16.7; P = 0.025). Clinical factors and syncope characteristics were not related with EPS result.

CONCLUSIONS

Diagnostic yield of EPS in patients with syncope and BBB is moderate (41%). Type of conduction disturbance pattern and PR interval are associated with the electrophysiological (EP) test result. Patients with LBBB or bifascicular block have the highest rate of positive EP test. Long PR interval increases the proportion of positive EPS in all conduction disturbance patterns.

Recommendations for the use of electrophysiological study: Update 2018

The field of cardiac electrophysiology has greatly developed during the past decades. Consequently, the use of electrophysiological studies (EPSs) in clinical practice has also significantly augmented, with a progressively increasing number of certified electrophysiology centers and specialists. Since Zipes et al published the Guidelines for Clinical Intracardiac Electrophysiology and Catheter Ablation Procedures in 1995, no official document summarizing current EPS indications has been published. The current paper focuses on summarizing all relevant data of the role of EPS in patients with different types of cardiac pathologies and provides up-to-date recommendations on this topic. For this purpose, the PubMed database was screened for relevant articles in English up to December 2018 and ESC and ACC/AHA Clinical Practice Guidelines, and EHRA/HRS/APHRS position statements related to the current topic were analyzed. Current recommendations for the use of EPS in clinical practice are discussed and presented in 17 distinct cardiac pathologies. A short rationale, evidence, and indications are provided for each cardiac disease/group of diseases. In conclusion, because of its capability to establish a diagnosis in patients with a variety of cardiac pathologies, the EPS remains a useful tool in the evaluation of patients with cardiac arrhythmias and conduction disorders and is capable of establishing indications for cardiac device implantation and guide catheter ablation procedures.

Syncope: Electrocardiographic and Clinical Correlation

Syncope is a frequent condition, owing to a transient global cerebral hypoperfusion, that may depend on a reduction of vascular total peripheral resistance and/or cardiac output. Cardiac syncope doubled the risk of death from any cause and increased the risk of nonfatal and fatal cardiovascular events. Arrhythmias are the most common cardiac causes of syncope. Both bradyarrhythmias and tachyarrhythmias may predispose to syncope. The first line evaluation relies on clinical history, physical examination, active standing test, 12-lead echocardiogram. The diagnostic yield of electrophysiological study in detecting the cause of syncope depends highly on the pretest probability.

Ajmaline Challenge To Unmask Infrahisian Disease In Patients With Recurrent And Unexplained Syncope, Preserved Ejection Fraction, With Or Without Conduction Abnormalities On Surface ECG

Background: Pharmacological challenge with class I antiarrhythmic drug is a recommended diagnostic test in patients with unexplained syncope only in the presence of bundle branch block, when non-invasive tests have failed to make the diagnosis. Its role in patients with minor or no conduction disturbances on 12-leads ECG has not been evaluated yet. It is also not clear which are the values of His-Ventricular interval to be considered diagnostic. We sought to evaluate the role of ajmaline challenge in unmasking the presence of an infrahisian disease in patients with recurrent and unexplained syncope, regardless of the existence of conduction disturbances on surface ECG. Materials And Methods: Patients with history of recurrent syncope, preserved EF and a negative first level workup were enrolled. Conduction disturbances on ECG were not considered as an exclusion criteria. During EPS, basal HV conduction was determined. In the presence of a HV >70 msec the study was interrupted and the patient was implanted with a pacemaker. If the HV was ≤ 70 msec, ajmaline was infused and HV was reassessed. The maximum value of HV was considered. A prolongation ≥ 100 msec was considered as diagnostic and indicative of conduction disease, and the patient underwent pacemaker implantation. Patients with an HV <100 msec were implanted with an ILR. Results: Sixteen consecutive patients were studied (age 76±5.2 years). Nine patients had conduction disturbances at baseline ECG (group ECG+). Among them, 5 had a basal diagnostic HV interval and 4 had a non-diagnostic HV interval. In the latter group, abnormal response to ajmaline was observed in 3 patients. In this group only one patient was implanted with an ILR, 8 patients were implanted with a pacemaker. Among the seven patients without conduction disturbances (group ECG-), no one had a diagnostic basal HV interval. After drug administration, 4 patients had a non-diagnostic response and were implanted with an ILR, while 3 patient had a pathological response and were implanted with a pacemaker. No difference was found in the values of maximum HV interval prolongation after ajmaline between the two groups (P = 0.89). During a mean follow up of 13±3 months, no patient has developed a syncopal episode. One patient in group ECG- and negative drug test was implanted after 3 months with a permanent pacemaker because of a two to one asymptomatic AV block at ILR interrogation. Conclusions: Ajmaline challenge is a useful tool to unmask the presence of a infrahisian disease in patients with preserved EF, unexplained syncope and negative workup, even in the absence of conduction disturbances on 12-leads ECG. It is a simple and safe test that may disclose the detection of the disease. In these patients, an earlier pacemaker implantation of a pacemaker, may avoid the consequences of a syncopal recurrence. Values of HV interval > 70 msec in basal conditions and ≥ 100 msec after ajmaline administration seem appropriate to unmask infrahisian disease. Larger population is required to validate this hypothesis.

Prevention of Syncope Through Permanent Cardiac Pacing in Patients With Bifascicular Block and Syncope of Unexplained Origin

Background—

Syncope in patients with bifascicular block (BFB) is a common event whose causes might be difficult to assess.

Methods and Results—

Prevention of syncope through permanent cardiac pacing in patients with bifascicular block (PRESS) is a multicenter, prospective, randomized, single-blinded study designed to demonstrate a reduction in symptomatic events in patients with bifascicular block and syncope of undetermined origin implanted with permanent pacemaker. Device programming mode (NASPE/BPEG code) at DDD with a lower rate of 60 ppm is compared with backup pacing at DDI with a lower rate of 30 ppm. The end point consisted of (1) syncope, (2) symptomatic presyncopal episodes associated with a device intervention (ventricular pacing), and (3) symptomatic episodes associated with intermittent or permanent atrioventricular block (any degree). One hundred one patients were enrolled and randomized. Primary end point events at 2 years were observed in 23 patients, with a significant lower incidence in the study group (hazard ratio, 0.32; 95% confidence interval [CI], 0.10–0.96; P =0.042). Reduction of any symptoms, associated or not with device intervention, was superior in DDD60 compared with DDI30 (hazard ratio, 0.4; 95% confidence interval, 0.25–0.78; P =0.0053). Fourteen patients developed other rhythm diseases and met class I indication for pacing. The annual incidence of rhythm disease development was 7.4%.

Conclusions—

In patients with bifascicular block and syncope of undetermined origin, the use of a dual chamber pacemaker programmed to DDD60 led to a significant reduction of syncope or symptomatic events associated with a cardioinhibitory origin, compared with DDI30 programming. Symptoms associated with a new onset of rhythm disease were found in 15% of the population at 2 years.

Correlation of noninvasive electrocardiography with invasive electrophysiology in syncope of unknown origin: implications from a large syncope database

BACKGROUND

The evaluation of syncope can be expensive, unfocussed, and unrevealing yet, failure to diagnose an arrhythmic cause of syncope is a major problem. We investigate the utility of noninvasive electrocardiographic evaluation (12-lead ECG and 24-hour ambulatory electrocardiographic recordings) to predict electrophysiology study results in patients with undiagnosed syncope.

METHODS

We evaluated 421 patients with undiagnosed syncope who had an electrocardiogram (ECG), an electrophysiology study, and 24-hour ambulatory monitoring. Noninvasive testing was used to predict electrophysiology testing outcomes. Multivariable logistic regression analysis adjusting for age, sex, presence of heart disease, and left ventricular ejection fraction (LVEF) was used to assess independent predictors for sinus node disease, atrioventricular node disease, and induction of ventricular tachyarrhythmias.

RESULTS

Patients were divided into four groups: group 1, abnormal ECG and ambulatory monitor; group 2, abnormal ECG only; group 3, abnormal ambulatory monitor; and group 4, normal ECG and ambulatory monitor. The likelihood of finding at least one abnormality during electrophysiologic testing among the four groups was highest in group 1 (82.2%) and lower in groups 2 and 3 (68.1% and 33.7%, respectively). In group 4, any electrophysiology study abnormality was low (9.1%). Odds ratios (OR) were 35.9 (P < 0.001), 17.8 (P < 0.001), and 3.5 (P = 0.064) for abnormal findings on electrophysiology study, respectively (first three groups vs the fourth one). ECG and ambulatory monitor results predicted results of electrophysiology testing.

CONCLUSION

Abnormal ECG findings on noninvasive testing are well correlated with potential brady- or/and tachyarrhythmic causes of syncope, in electrophysiology study of patients with undiagnosed syncope.

Mechanism of syncope in patients with bundle branch block and negative electrophysiological test

BACKGROUND

In patients with syncope and bundle branch block (BBB), syncope is suspected to be attributable to a paroxysmal atrioventricular (AV) block, but little is known of its mechanism when electrophysiological study is negative.

METHODS AND RESULTS

We applied an implantable loop recorder in 52 patients with BBB and negative conventional workup. During a follow-up of 3 to 15 months, syncope recurred in 22 patients (42%), the event being documented in 19 patients after a median of 48 days. The most frequent finding, recorded in 17 patients, was one or more prolonged asystolic pause mainly attributable to AV block; the remaining 2 patients had normal sinus rhythm or sinus tachycardia. The onset of the bradycardic episodes was always sudden but was sometimes preceded by ventricular premature beats. The median duration of the arrhythmic event was 47 seconds. An additional 3 patients developed nonsyncopal persistent III-degree AV block, and 2 patients had presyncope attributable to AV block with asystole. No patients suffered injury attributable to syncopal relapse.

CONCLUSIONS

In patients with BBB and negative electrophysiological study, most syncopal recurrences have a homogeneous mechanism that is characterized by prolonged asystolic pauses, mainly attributable to sudden-onset paroxysmal AV block.

Pharmacological stress testing of the His-Purkinje system in patients with bifascicular block

This literature review, based mainly on the English-language literature, focuses on pharmacological stress testing of the His-Purkinje system as part of an invasive electrophysiological study. The main target group for this investigation is patients with bifascicular block and syncope in which intermittent high grade AV block is suspected. Several drugs have been used for this purpose, mainly Class I antiarrhythmic agents such as ajmaline, procainamide, disopyramide, and flecainide. Most studies, unfortunately, suffer from limited patient numbers, lack of adequate control groups, and/or adequate follow-up. The sensitivity of the disopyramide stress test has been shown to be 75%-100% for prediction of impending high grade AV block. The specificity was > 90%. Studies on procainamide have shown a sensitivity of 60% but the specificity has not been assessed. There are no studies allowing a strict comparison of the diagnostic value of pharmacological provocation with different drugs. Based on the similarities of the electrophysiological effects on the His-Purkinje system of the above Class I agents, it is reasonable to assume that all of them might be of diagnostic value in the present clinical context, provided atrial and ventricular stimulation after drug is included in the protocol.

Value and limitations of electrophysical testing for syncope

Syncope is by definition a transient event, and its cause has usually resolved by the time the patient is examined. Electrophysiologic testing provides a method for assessing a patient's risk for future arrhythmias based on the known sensitivity and specificity of the analyses of sinus node function, atrioventricular conduction, and responses to programmed atrial and ventricular stimulation. Interpretation of these data must always be made in the context of the patient's total clinical situation.

Head-up tilt test. A nonspecific method of evaluating patients with bifascicular block

BACKGROUND

Patients with bifascicular block have an increased risk of syncopal attacks, but the underlying mechanism often remains unclear despite an extensive diagnostic workup. The head-up tilt test has been established as an important diagnostic tool in the unmasking of vasovagal syncope in patients with unexplained syncope. Its role in the evaluation of patients with bifascicular block has not been studied.

METHODS AND RESULTS

A head-up tilt test, using a 60 degrees angle of tilt for 45 minutes without pharmacological provocation, was performed in 25 patients with bifascicular block and syncope that remained unexplained after an extensive invasive and noninvasive electrophysiological investigation. As a control group, 25 subjects with bifascicular block without syncope, matched for age, sex, left ventricular function, and underlying heart disease, were included. A positive head-up tilt test was found in 7 (28%) of the syncope patients and in 8 (32%) of the control subjects (P = NS). Six patients, of whom 3 had a positive tilt test, had recurrent syncopal attacks during 32 months of follow-up. None of the control subjects had syncope during follow-up.

CONCLUSIONS

This study gives rise to serious concern regarding the specificity of the head-up tilt test in patients with bifascicular block. A head-up tilt test should therefore be interpreted with caution, and its role as a diagnostic tool in this patient category remains to be established.

Disopyramide stress test: a sensitive and specific tool for predicting impending high degree atrioventricular block in patients with bifascicular block

OBJECTIVE

To study the value of intravenous disopyramide as part of an invasive electrophysiological study in predicting impending high degree atrioventricular block in patients with bifascicular block.

DESIGN

An invasive electrophysiological study was performed in the basal state and after the infusion of disopyramide (2 mg/kg body weight). The progression to high degree atrioventricular block was assessed by bradycardia-detecting pacemakers or repeated 12-lead electrocardiogram recordings, or both.

PATIENTS

73 patients with bifascicular block were included, of whom 25 had a history of unexplained syncope. The remaining 48 patients had no arrhythmia related symptoms and were included as controls. All patients had an ejection fraction of > 35%.

RESULTS

After a mean follow up of 23 months, seven patients in the syncope group and three in the non-syncope group had a documented high degree atrioventricular block or pacemaker-detected bradycardia of < or = 30 beats/min for > or = 6 s. The sensitivity of the disopyramide test was 71% and the specificity 98%. The corresponding figures for an abnormal electrophysiological study in the basal state were 14% and 91%, respectively.

CONCLUSIONS

The sensitivity of an invasive electrophysiological study in patients with bifascicular block and syncope can be markedly increased by the use of intravenous disopyramide. A positive test is a highly specific finding and warrants pacemaker implantation.

Diagnostic value of programmed ventricular stimulation in patients with bifascicular block: a prospective study of patients with and without syncope

OBJECTIVES

The aim of this study was to examine the inducibility of ventricular arrhythmias in patients with bifascicular block both with and without a history of syncope and to relate the findings to clinical events during follow-up.

BACKGROUND

Patients with bifascicular block have an increased risk of sudden death that is not reduced by pacemaker treatment. This risk could be related to a high incidence of ventricular arrhythmias.

METHOD

Programmed ventricular stimulation was performed in 101 patients with bifascicular block: 41 had a history of unexplained syncope, and 60 were asymptomatic.

RESULTS

Programmed ventricular stimulation resulted in a sustained ventricular arrhythmia in 18 patients (18%), 8 in the syncope group and 10 in the nonsyncope group (p = NS). Three patients in each group had an inducible sustained monomorphic ventricular tachycardia. During a mean follow-up of 21 months, 10 patients experienced a clinical event defined as sudden death (n = 4), syncope (n = 5) or appropriate discharges from an implantable cardioverter-defibrillator (n = 1). Only one of these patients had an inducible ventricular arrhythmia at baseline.

CONCLUSIONS

The inducibility of ventricular arrhythmias is high in patients with bifascicular block and of the same magnitude in patients with and without a history of syncope. Clinical events during follow-up were not predicted by programmed ventricular stimulation in either of the two groups. The finding of inducible ventricular arrhythmia in patients with bifascicular block should therefore be interpreted with caution.

Atrioventricular block progression in patients with bifascicular block assessed by repeated electrocardiography and a bradycardia-detecting pacemaker

Syncope may be due to intermittent high-degree atrioventricular (AV) block, but a cause-relation is sometimes difficult to prove. Diagnostic methods with high predictive value proven by instruments for safe and sensitive follow-up are needed. A bradycardia-detecting pacemaker was used in patients with bifascicular block, who had been the subjects of pharmacologic stress testing of the His-Purkinje system. Thirty-seven patients were included, of whom 26 had experienced at least 1 syncopal episode of suspected bradycardia origin, and 11 had previously documented transient high-degree AV block. The electrophysiologic study included injection of disopyramide 2 mg/kg (up to 150 mg) over 5 minutes. A positive test result was defined as spontaneous or pacing-induced His-Purkinje high-degree AV block after drug or a drug-induced HV prolongation of > or = 50%. Patients were followed an average 63 months with repeated electrocardiography and a diagnostic pacemaker (n = 23). Altogether, 24 patients had a significant bradycardia diagnosed by either or both methods. The sensitivity and positive predictive values were: HV interval > or = 70 ms at baseline, 47% and 88%; a positive disopyramide test result, 75% and 80%; and HV interval > or = 70 ms or a positive disopyramide test result, 93% and 74%, respectively. Thus, the diagnostic pacemaker is a safe and sensitive tool for evaluating the information obtained at electrophysiologic study, and pharmacologic stress testing with disopyramide has an informative value in patients with bifascicular block and syncope when results at baseline are inconclusive.

Syncope

Syncope is a clinical entity of diverse cause. The historical features surrounding the syncopal event and the presence or absence of heart disease are the most important features in establishing the cause for syncope. Passive head-up tilt study provides a means of identifying many patients with vasodepressor syncope. Electrophysiologic study is important in the elucidation of syncope in patients who have syncope undefined after noninvasive evaluation. With proper use of the modalities available, few patients will have an undefined cause for syncope.

Unmasking of sinus node dysfunction by ajmaline

A 75-year-old male with bifascicular block presented with recurrent giddiness and presyncope. Prolonged monitoring of the cardiac rhythm did not reveal any arrhythmia. Electrophysiological evaluation, including an ajmaline stress test, was performed. Ajmaline had an unusual effect. It reproducibly induced sinus arrest and thus unmasked a latent sick sinus syndrome.

Clinical implications of electrophysiology study findings in patients with chronic bifascicular block and syncope

Electrophysiology study was performed in 93 patients with bifascicular block and unexplained syncope. Clinical evidence of organic heart disease was present in 33 (35%). Electrophysiological abnormalities were detected in 45 patients (48%). Of these, 36 had distal conduction disease, including 28 with an HV interval greater than 55 ms (mean 76.4 ms), and eight who developed infraHisian block following either intravenous procainamide (four) or atrial pacing (four). Sick sinus syndrome was evident in six patients and a further two had carotid sinus hypersensitivity. Sustained monomorphic ventricular tachycardia (VT) was induced in only three patients, two of whom also had prolonged HV interval. Among the 93 patients, 45 had therapy which was guided by positive findings at electrophysiology study (Group 1). Of these, 42 received permanent pacemakers, two were treated with combined permanent pacing and antiarrhythmic drug therapy, and one was treated with antiarrhythmic drug alone. In addition, eight patients without electrophysiologic abnormalities were treated empirically by pacing (Group 2). Finally, 40 patients without electrophysiologic abnormalities received no specific therapy (group 3). At a mean follow-up of 39 months (range two-125 months), recurrence of syncope had occurred in 4% of Group 1 patients, and 25% of Group 3 patients (p less than 0.05). No patient in Group 2 had had recurrence. Total mortality was 40%, including 47% of patients in Group 1, 25% of Group 2, and 35% of Group 3. Death was sudden in seven patients. We concluded that among patients with bifascicular block and syncope, therapy directed by findings at electrophysiology study was associated with symptomatic improvement, but mortality was not significantly influenced.(ABSTRACT TRUNCATED AT 250 WORDS)