Expert cardiologists cannot distinguish between Brugada phenocopy and Brugada syndrome electrocardiogram patterns.

AIMS: Brugada phenocopies (BrPs) are electrocardiogram (ECG) patterns that are identical to true Brugada syndrome (BrS) but are induced by various clinical conditions. The concept that both ECG patterns are visually identical has not been formally demonstrated. The aim of our study was to determine if experts on BrS were able to accurately distinguish between the BrS and BrP ECG patterns. METHODS AND RESULTS: Six ECGs from confirmed cases of BrS and six ECGs from previously published cases of BrP were included in the study. Surface 12-lead ECGs were scanned, saved in JPEG format, and sent to 10 international experts on BrS for evaluation (no clinical history provided). Evaluators were asked to label each case as a Brugada ECG pattern or non-Brugada ECG pattern by visual interpretation alone. The overall accuracy was 53 ± 33% for all cases. Within the BrS cases, the mean accuracy was 63 ± 34% and within the BrP cases, the mean accuracy was 43 ± 33%. Intra-observer repeatability was moderate (κ = 0.56) and inter-observer agreement was fair (κ = 0.36) while evaluator accuracy vs. the true diagnosis was only marginally better than chance (κ = 0.05). Similarly, diagnostic operating characteristics were poor (sensitivity 62%, specificity 43%, +LR 1.1, -LR 0.9). CONCLUSION: Our results provide strong evidence that BrP and BrS ECG patterns are visually identical and indistinguishable. These findings support the use of systematic diagnostic criteria for differentiating BrP vs. BrS as an erroneous diagnosis may have a negative impact on patient morbidity and mortality.

Accelerated idioventricular rhythm unmasking the brugada electrocardiographic pattern.

It has recently been reported that a high-degree right bundle branch block (RBBB) may conceal the electrocardiographic manifestations of the Brugada ECG pattern. An 82-year-old with recent onset palpitations was seen in clinic. The resting ECG showed sinus rhythm, high-degree RBBB, and an irregular idioventricular rhythm. Some fusion beats between sinus rhythm and idioventricular rhythm occurred spontaneously depicting incomplete RBBB pattern and a clear cut elevation of the ST-segment was unveiled, giving rise to a suspicious Brugada ECG pattern. The mechanisms and implications of these findings are discussed.

A reappraisal on lidocaine-sensitive repetitive, uniform atrial tachycardia.

BACKGROUND: Lidocaine sensitive, repetitive atrial tachycardia is an unusual arrhythmia whose electrophysiologic substrate remains undefined. We aimed to analyze the electropharmacologic characteristics of this arrhythmia with emphasis on its cellular substrate and response to drug challenges. METHODS: We retrospectively analyzed a series of 18 patients from an electrocardiographic and electrophysiologic perspective and the response to pharmacological challenge. RESULTS: There was no evidence of structural heart disease in 12 patients, 4 patients presented with systemic hypertension; one patient had a prior myocardial infarction and one a mitral valve prolapse. The arrhythmia depicted a consistent pattern in nine patients. The first initiating ectopic beat showed a long coupling interval, the cycle length of the second atrial ectopic beat presented the shortest cycle length and a further prolongation was apparent towards the end of the atrial salvos. Conversely, in the other nine cases, the atrial tachycardia cycle length was erratic. The arrhythmia was suppressed by asynchronous atrial pacing at cycle lengths longer than those of the atrial tachycardia. Intravenous lidocaine eliminated the arrhythmia in all patients, but intravenous verapamil suppressed the atrial tachycardia in only two patients while adenosine caused a transient disappearance in 2/8 patients. Only one patient responded to all the three agents. Radiofrequency ablation was successfully performed in 10 patients. CONCLUSIONS: Repetitive uniform atrial tachycardia can be sensitive to lidocaine. In few cases, this rare focal arrhythmia may be also suppressed by adenosine and/or verapamil, which suggests a diversity of electrophysiologic substrates that deserve to be accurately identified.

Right bundle branch block and middle septal fiber block with or without left anterior fascicular block manifested as aberrant conduction in apparent healthy individuals: Electro-vectorcardiographic characterization.

BACKGROUND: Right bundle branch block (RBBB) evident in the precordial ECG leads may be associated with evidence of left bundle branch involvement in the limb leads. Any of the components of the left bundle can be involved, and this complex interventricular conduction abnormality has previously been described in patients with underlying heart disease. OBJECTIVES: To analyze the electro-vectorcardiographic manifestations of RBBB with left middle septal fiber block (LMSFB), with or without left anterior fascicular block (LAFB) in premature atrial beats of patients without apparent structural heart disease. METHODS: Twelve patients (8 men/4 women; mean age: 32±8years) with premature atrial contractions with this conduction abnormality were included. Surface 12 simultaneous lead ECG recordings and the corresponding vectorcardiographic loops were analyzed. RESULTS: The QRS complexes with RBBB and also LMSFB persisted for between 150 and 190ms. There were no q waves in lead I. The maximum spatial vector (72-86ms) was directed posteriorly, superiorly, and leftward, and the terminal forces were oriented anteriorly, inferiorly and rightward. In 10 patients, small q waves were apparent in leads V1-V2 and the frontal QRS axis was -60° and -70°, with the 46ms vector located at -50°±5. All of these patients most probably had LAFB in addition to LMSFB. In two patients, the initial electrical forces were directed anteriorly, inferiorly, and leftward, and the 46ms vector axis in the frontal plane was 6° and 11°, respectively, indicating absence of LAFB. CONCLUSIONS: The combination of RBBB and LMSFB occurring in patients without apparent structural heart disease may be related to the simultaneous occurrence of block of conduction through these components of the Purkinje network. The anterior fascicle of the left bundle may also be involved.

The link in Linking.

We present 2 cases of the slow-fast form of AVNRT with initially narrow QRS complexes followed by sudden unexpected transition to persistently wide QRS complexes due to aberrant intraventricular conduction. Introduction of a properly timed extrastimulus in one case and critical oscillations in cycle length due to short-long coupling in the second case set the stage for the initial bundle branch block. However, persistence of the aberrancy pattern once the initial event abated was maintained by the "linking" phenomenon. Delayed, retrograde concealed activation from the contralateral bundle branch perpetuated the initial bundle branch block.

The electrocardiographic diagnosis of intraventricular blocks coexisting with ventricular preexcitation.

The electrocardiographic diagnosis of intraventricular conduction disturbances may be hindered by the coexistence of ventricular preexcitation. In fact, the premature depolarization of ventricular myocardium through an accessory pathway tends to conceal any electrocardiographic manifestation of a bundle-branch block. However, there are several conditions favoring the diagnosis of bundle-branch block associated with ventricular preexcitation: intermittency of ventricular preexcitation and/or bundle-branch block, fast atrioventricular (AV) nodal impulse propagation, slow conduction over the accessory pathway or between its ventricular insertion site and the remaining myocardium, and presence of atrioventricular junctional ectopic beats exposing the intraventricular conduction disturbance. This article reexamines the available data on preexcitation in patients with intraventricular blocks and presents clinical examples to emphasize the importance of a thorough examination of the electrocardiogram to attain the correct diagnosis of this association.

Implantable cardioverter defibrillators and Chagas' disease: results of the ICD Registry Latin America.

AIMS: Chagas' disease is an endemic parasitic affliction in Latin America. It is frequently associated with ventricular tachyarrhythmia and sudden death. The aim of this study is to assess the evolution of patients with Chagas' disease treated with an implantable cardioverter defibrillator (ICD). METHODS AND RESULTS: Eighty-nine chagasic patients with ICD were included for analysis from the Medtronic ICD Registry Latin America. At implant, mean age was 59 +/- 10 years, and 72% were male. Eighty-one patients (91%) had secondary prevention indications. Mean left ventricular ejection fraction was 40 +/- 11%, and mean follow-up was 12 +/- 7 months. During follow-up, six patients died (6.7%); three due to congestive heart failure, one due to sudden death, and two due to non-cardiac cause. Hospitalization occurred in seven patients. Thirty-eight patients (42%) received appropriate ICD therapies. A total of 737 episodes were detected by the ICD. The mean period between ICD implantation and the first appropriate therapy was 104 days. Electrical storms were observed in 14 of the 89 patients (15.7%). Inappropriate therapies were observed in seven patients. CONCLUSION: This registry confirms that ICD therapy provides protection by effectively terminating life-threatening arrhythmias in patients with Chagas' disease. This is especially so when patients receive the device for secondary prevention.

Supernormal conduction in the anomalous bundles of the Wolff-Parkinson-White syndrome: an overlooked electrophysiologic property with potential clinical implications.

The anterograde refractory period (RP) of the accessory pathway (AP) is the main determinant factor of ventricular rate during atrial fibrillation in the Wolff-Parkinson-White (WPW) syndrome. We describe 3 examples of anterograde supernormal conduction (SNC) and 1 of retrograde SNC in APs. The paradoxical early recovery of propagation due to SNC, well inside a prolonged anterograde RP in the AP, may play a relevant role to determine the rate of ventricular response during atrial fibrillation, eventually leading to extremely fast ventricular rates, syncope, and even ventricular fibrillation in patients with WPW syndrome supposed a priori to be exposed to a low risk of sudden cardiac death. This may require very precise conditions, including an enhanced adrenergic influence on the heart. Retrograde SNC in APs may also participate in the mechanism of paroxysmal supraventricular tachycardias that are not easily induced by programmed cardiac stimulation.

Inappropriate sinus tachycardia may be related to an immunologic disorder involving cardiac beta andrenergic receptors.

BACKGROUND: The mechanisms underlying inappropriate sinus tachycardia are not fully known. An autonomic imbalance seems to play a role, but no attempts have been made to investigate a relationship between this arrhythmia and the antiautonomic membrane receptor antibodies found in other heart disorders and arrhythmias. OBJECTIVE: The purpose of this study was to investigate the prevalence and the functional and biochemical effects of circulating antiautonomic receptor antibodies in patients with inappropriate sinus tachycardia. METHODS: We studied 21 patients with inappropriate sinus tachycardia and 15 healthy volunteers. The chronotropic effects of the IgG fractions (also of affinity-purified anti-beta1 adrenergic receptor antibodies in selected cases) were assessed on cultured cardiomyocytes before and after exposure to atropine and propranolol. The effects of the IgG fractions from five patients and five healthy volunteers on cAMP production were evaluated in COS-7 cells transfected with genes encoding for beta1 or beta2 adrenergic receptor. RESULTS: The IgG fractions from patients with inappropriate sinus tachycardia exerted a positive chronotropic action with a high prevalence of anti-beta receptor antibodies (52%) and induced a clear-cut and long lasting increment of cAMP. No anti-M2 cholinergic receptor antibodies were found. The IgG fractions from healthy volunteers did not contain antiautonomic receptor antibodies. CONCLUSIONS: Our results suggest, for the first time, a link between inappropriate sinus tachycardia and circulating anti-beta adrenergic receptor antibodies that induce a persistent increment in cAMP production. This finding offers new insight into the physiopathology of inappropriate sinus tachycardia with potential therapeutic consequences.

Recording of high V1-V3 precordial leads may be essential to the diagnosis of Brugada syndrome during the ajmaline test.

Sodium channel-blocking agents are routinely used to unveil the Brugada syndrome in patients in whom the typical electrocardiographic pattern is absent or doubtful. In this article, the authors report a patient with syncopal episodes of unknown origin in whom the conventional electrocardiographic result was normal and a negligibly small "saddle back" type repolarization was present in lead V2 recorded 2 intercostal spaces above the conventional site. Intravenous ajmaline (50 mg) did not elicit the type 1 pattern of the Brugada syndrome in the precordial leads obtained at their usual level, but a clear-cut coved-type repolarization was apparent in high right precordial leads. These findings indicate that high precordial leads should be routinely recorded while assessing the ajmaline test in patients suspected of having the Brugada syndrome.

The mechanisms of spontaneous termination of reentrant supraventricular tachycardias.

BACKGROUND: Atrioventricular nodal reentrant tachycardia (AVNRT) and atrioventricular reentrant tachycardia (AVRT) often terminate spontaneously, presumably due to changes in the electrophysiological properties of the reentrant circuit. However, the mechanism of spontaneous termination of these arrhythmias is incompletely understood. METHODS: We included 70 consecutive patients with reentrant supraventricular tachycardias (35 AVNRT, 35 AVRT) in whom the arrhythmia ended spontaneously during the electrophysiologic study. We determined in each patient the duration of the induced arrhythmia, site of block, beat-to-beat oscillations in tachycardia cycle-length (CL), A-H, H-V, H-A and V-A intervals. RESULTS: In 21/34 (62%) patients with AVNRT and 19/30 (63%) with orthodromic AVRT, tachycardia termination was preceded by progressive increase in tachycardia CL due to prolongation of the A-H interval (Mobitz type-I pattern). In 13/34 patients with AVNRT (38%) and 11/30 with orthodromic AVRT (37%), termination occurred suddenly without a preceding change in CL, with block ensuing retrogradely either in the fast AV nodal pathway or the accessory pathway (Mobitz type-II pattern). In 4/5 patients with antidromic AVRT the tachycardia ended at the retrograde limb with previous prolongation of the VA interval. CONCLUSION: Spontaneous termination of AVNRT and AVRT is a time-related phenomenon. Despite different pathways being involved in these two reentrant tachycardias, termination can follow antegrade or retrograde block in similar ratio (60% antegradely and 40% retrogradely). Antegrade block is preceded by prolongation of the AH interval (Mobitz type-I), whereas retrograde block occurs unexpectedly in the retrograde limb (Mobitz type-II). Fatigue of conduction appears to be involved in this phenomenon.

Pharmacologic reversion of persistent atrial fibrillation with amiodarone predicts long-term sinus rhythm maintenance.

OBJECTIVE: The study analyzed the role of different variables that determine long-term sinus rhythm maintenance in patients with persistent atrial fibrillation who are treated with amiodarone. BACKGROUND: It has been recognized that different factors influence long-term sinus rhythm preservation after the conversion of persistent atrial fibrillation. Although the duration of the arrhythmia appears to be the most important factor, consistent information regarding the role of the mode of arrhythmia conversion (pharmacologic or electric) is still lacking. METHODS: One hundred and forty one anticoagulated patients with persistent atrial fibrillation (median duration 8 months, percentiles 25 and 75: 2-24) were treated for 4 weeks with oral amiodarone (600 mg/day). Those in whom the arrhythmia persisted underwent electric cardioversion. After restoration of normal sinus rhythm (either pharmacologic or electric), all patients received a daily dose of amiodarone (200 mg) and were followed for a median of 19 months (percentiles 25 and 75: 8-34 months). RESULTS: Sixty eight patients (48.22%) regained sinus rhythm during the initial period of amiodarone treatment with 600 mg/day (Group I) and 73 (51.78%) required electric cardioversion (Group II). During the entire follow-up, atrial fibrillation relapsed in 63 patients: 17 (25%) in Group I and 46 (63%) in Group II. Recurrences of the arrhythmia were strikingly less frequent in patients whose atrial fibrillation lasted 12 months or less (33/103, 32.3%) than in those whose atrial fibrillation lasted more than 12 months (30/38, 78.94%). In the multivariate analysis, the mode of reversion (HR, 0.37; CI, 0.21-0.65) and the duration of the arrhythmia (HR, 2.55; CI, 1.54-4.20) were the determinants for long-term sinus rhythm maintenance. Age, sex, left atrium size, left ventricle diameter, and the shortening fraction did not significantly influence the rate of arrhythmia recurrence. Among the 141 patients included in the study, 113 patients were followed for at least 1 year, and cardiac rhythm was assessed at this time. Of these, only 1 of 48 patients (2.1%) in Group I was in atrial fibrillation, in marked contrast with 18 of 65 patients (27.8%) in Group II (RR, 0.075; 95% CI, 0.01-0.54). CONCLUSIONS: In patients with persistent atrial fibrillation, long-term preservation of sinus rhythm under chronic amiodarone treatment may be anticipated when the arrhythmia lasts 12 months or less and/or its reversion is obtained pharmacologically. We may confidently assume that these two factors have a beneficial additive influence on the outcome.

Clinical and experimental evidence of supernormal excitability and conduction.

True supernormality of excitability and conduction has been demonstrated in normal Purkinje fibers in in vitro studies. In the clinical setting, supernormality of conduction is manifested better than expected. This phenomenon is much more common than previously thought, particularly in the presence of certain clinical conditions. If a careful scanning of the cardiac cycle is performed on all patients with intermittent bundle branch block and second degree or advanced infranodal AV block, accessory pathways and mulfunctioning pacemakers, it is anticipated that a much larger amount of supernormal excitability and conduction will be unmasked.

Short-term amiodarone therapy after reversion of persistent atrial fibrillation reduces recurrences at 18 months.

BACKGROUND: The aim of this study was to compare the outcome of 3 months vs. 18 months of amiodarone treatment after atrial fibrillation (AF) conversion in patients who experienced the first episode of persistent AF. METHODS: We included 51 patients who experienced the first episode of persistent AF receiving amiodarone (600 mg) daily for 4-6 weeks. If AF persisted, electrical cardioversion (ECV) was performed. All patients received amiodarone (200 mg daily) for 3 months and then were randomized to amiodarone (Group I) or placebo (Group II) and followed for 15 months. The control group comprised 9 untreated patients undergoing ECV. Treatment effectiveness was evaluated using a Bayesian model. RESULTS: Eighteen months after AF reversion, 22 (81.5%) patients in Group I, 13 (54.2%) patients in Group II, and 1 (11.1%) patient in the control group remained in sinus rhythm. No differences were found between Group I patients who required ECV and Group II patients. Sinus rhythm was preserved in all Group I patients when it was achieved during amiodarone administration. Limiting adverse effects occurred in 3 (11.1%) patients in Group I. CONCLUSIONS: In patients regaining sinus rhythm after the first episode of persistent AF, a 3-month amiodarone treatment after reversion is a reasonable option for rhythm control.

Advanced interatrial block is associated with recurrence of atrial fibrillation post pharmacological cardioversion.

INTRODUCTION: Management of atrial fibrillation (AF) is hampered by frequent recurrences after restoration of sinus rhythm. Delayed interatrial conduction has been associated with the development of AF in different clinical settings. The aim of our study was to assess whether advanced interatrial block (aIAB) was associated with AF recurrence after pharmacological cardioversion with two different antiarrhythmic drugs. METHODS: We included 61 patients with recent onset AF without structural heart disease that underwent successful pharmacological cardioversion. Thirty-one patients received a single oral dose of propafenone, and 30 patients received iv vernakalant. A 12-lead ECG (filter 150 Hz, 25 mm/s, 10 mm/mV) after conversion was evaluated for the presence of interatrial block (IAB); partial (pIAB): P-wave duration > 120 ms, and advanced (aIAB): P-wave > 120 ms and biphasic morphology (±) in inferior leads. Clinical follow-up and electrocardiographic recordings were performed for a 12-month period. RESULTS: Age was 58 ± 10.4 years and 50.8% were male. aIAB was present in 11 patients (18%) and pIAB in 10 (16.4%). At 1-year follow-up, 22 patients (36%) had AF recurrence. The recurrence rate with aIAB was 90.9% versus 70% in those with pIAB and 12.5% in normal P-wave duration (P = 0.001). The presence of aIAB was strongly associated with AF recurrence (odds ratio 18.4 in multivariable modeling). Recurrence was not affected by the drug used for cardioversion (P = 0.92). CONCLUSION: Advanced interatrial block is associated with higher risk of AF recurrence at 1 year after pharmacological cardioversion, independent of the drug used.

The multiple electrocardiographic manifestations of ventricular repolarization memory.

T wave "memory" is a peculiar variety of cardiac remodeling caused by a transient change in the course of ventricular depolarization (due to ventricular pacing, rate-dependent intraventricular block, ventricular preexcitation or tachyarrhythmias with wide QRS complexes). It is usually manifested by inverted T waves that appears when normal ventricular activation is restored. This phenomenon is cumulative and occurs earlier if the ventricular myocardium has previously been exposed to the same conditioning stimuli. In this article the different conditions giving rise to "classical" T wave memory development are reviewed and also "another" type of T wave memory is described. It is also shown that cardiac memory may induce not only negative (pseudo-primary) T waves but also a reversal of primary and pseudoprimary T waves leading to "normalization" of ventricular repolarization. The knowledge of these dissimilar consequences of T wave memory is essential to assess the characteristics of ventricular repolarization.