Ventriculoatrial Dissociation Research Articles

Atrial rates during treated ventricular tachycardia in patients with implantable cardioverter defibrillators: clinical implications of a vagal sinus node response

Abstract Introduction Autonomic tone plays an important role in the genesis and sustenance of ventricular tachycardia (VT). Whilst sympathetic hyperactivity is an established driver of ventricular arrhythmias, sinus node response during VT varies broadly between patients, and can be paradoxical. Purpose We hypothesized that device-detected changes in sinus node rate could be an important surrogate of the autonomic response to VT, and may exert significant – and potentially modifiable – haemodynamic consequences independent of ventricular activity. Methods Device electrograms were analysed from consecutive patients with dual chamber implantable cardioverter defibrillators (ICDs) requiring anti-tachycardia pacing (ATP) or defibrillation for sustained monomorphic VT. Atrial rates were measured before VT onset (‘baseline’) and again at the point of detection by the device. Sinus node response was characterized as ‘stable’ (atrial rate remained within 10% of baseline), ‘sympathetic’ (atrial rate increased >10%) or ‘vagal’ (atrial rate decreased >10%). Patients who did not maintain ventriculoatrial dissociation or who presented in atrial tachyarrhythmia were excluded. Symptoms and electrical response to ICD therapies were recorded. Results 172 treated episodes of VT were included from 97 patients (median age: 69 years, 65% male, 31% ischaemic cardiomyopathy, median ventricular rate: 205bpm, median ejection fraction: 30%). Sinus node response was stable in 55%, sympathetic in 24% and vagal in 21%. A vagal response was associated with ATP-refractory VT (OR: 2.2 (1.1-4.8) p=0.03) and, when adjusting for ventricular rate, was independently associated with symptoms of presyncope or syncope (adjusted OR: 6 (2.7-13.7), p<0.0001). Conclusions This preliminary analysis suggests that a vagal sinus node response during VT is associated with adverse outcomes in ICD patients. Vagolytic therapy has recently been demonstrated to improve haemodynamic tolerance during VT ablation; whether supportive atrial pacing during VT could mitigate symptoms and potentiate arrhythmia termination in ICD patients warrants further exploration. Figure 1: Change in sinus node rate during sustained monomorphic ventricular tachycardia in patients with dual chamber ICDs, stratified by the occurrence of presyncopal symptoms or syncopeFigure 1

Absent ventriculo-atrial conduction during right ventricular apical pacing but nodal response during para-Hisian pacing – What is the mechanism?

A 13-year-old-girl presented with one episode of pre-syncope while standing in a train. Her ECG was suggestive of preexcitation. Echocardiography revealed structurally normal heart without any ventricular hypertrophy. During electrophysiology study, her ventriculo-atrial (VA) conduction was absent even on isoprenaline. However, a para-Hisian pacing maneuver (PHP) revealed consistent VA conduction with a nodal response. This finding indicated that the VA dissociation at baseline was at infra-Hisian (VH) level and conduction at HA level was intact. In addition, this finding is coherent with a speculation of a fasciculo-ventricular pathway (FVP) resulting in such an ECG pattern in her. Pacing from various atrial sites (right atrium, coronary sinus) exhibited nearly fixed preexcitation and short non-varying HV interval confirmatory of FVP. Testing for a PRKAG mutation was advised for her.

Abstract 15372: The Lewis Lead

The Lewis lead is a modified ECG configuration that can enhance the amplitude of the atrial electrical activity and is useful when the atrial activity cannot be discerned in the standard ECG. The configuration involves applying the right arm electrode on the manubrium, left arm electrode to the 5th intercostal space on the right sternal border, left leg electrode over the right lower costal margin and right leg electrode in the standard position. The ECG is then interpreted in lead I and II. Herein we present a case where the Lewis lead aided in the diagnosis of complete heart block with underlying atrial fibrillation. Case Presentation: A 75 year old female with severe tricuspid regurgitation was admitted for tricuspid valve replacement. She had previous paroxysmal atrial fibrillation status post pulmonary vein isolation. The preoperative ECG revealed normal sinus rhythm. Postoperatively, ECG demonstrated a narrow complex ventricular rhythm at 70 beats per minute. No atrial activity could be clearly discerned (Image 1). The epicardial atrial wire placed intraoperatively was not functioning, therefore atrial electrogram could not be obtained. It was unclear from repeat ECGs if there was sinus arrest or atrial fibrillation in the atria. The Lewis lead was then utilized and revealed underlying atrial fibrillation (Image 1); together, this was consistent with atrial fibrillation and complete heart block with a junctional escape rhythm. The rhythm did not recover and there was progressive conduction system disease with widening of the QRS and episodes of severe bradycardia. She underwent pacemaker implantation. Discussion: By utilizing the Lewis lead we were able to establish the atrial rhythm and differentiate between atrial fibrillation and sinus arrest. The Lewis lead can also help narrow the differential for wide complex tachycardia by magnifying the p wave, thus making it easier to detect ventriculoatrial dissociation, a hallmark feature of ventricular tachycardia.

Selective and non-selective right bundle pacing for the diagnosis of bundle branch reentry ventricular tachycardia.

Bundle branch reentry ventricular tachycardia (BBRVT) can be seen in patients with conduction disease. In this report, we describe the use of conduction system pacing for its diagnosis. BBRVT was induced in two patients with infra-nodal conduction disease. Bundle branch reentry ventricular tachycardia with a left bundle branch block morphology was observed in the first patient (type A), whereas the second patient had a right bundle branch block morphology (type C).The diagnosis of BBRVT was confirmed in both patients by ventriculo-atrial dissociation, and the interdependence of the conduction system and the ventricular tachycardia cycle length variations.Selective and non-selective RB pacing was observed in the two patients during apical right ventricular pacing for entrainment of BBRVT with evidence of manifest entrainment with non-selective RB capture in the first patient, and concealed entrainment by selective RB capture in the second patient. Other criteria for entrainment including a short post-pacing interval at the right bundle pacing site were noted. Right bundle pacing is feasible in patients with BBRVT and may be a helpful manoeuver for the diagnosis of BBRVT.

Atypical fetal junctional ectopic tachycardia: a case report and literature review

BackgroundJunctional ectopic tachycardia (JET) is caused by ectopic rhythms, originating in the atrioventricular node, typically with heart rate between 200 and 250 bpm. Herein, we present a case of fetal JET with normal fetal heart rate and a review of nine cases.Case presentationA 32-year-old, gravida 2, para 1, woman in whom fetal JET could not be diagnosed prenatally because the fetal heart rate was within the normal range. The fetus was diagnosed with premature restriction of the foramen ovale, and a cesarean section was performed, owing to the right heart overload that was characterized by fetal ascites and abnormal fetal Doppler velocity. Postnatally, the female neonate was diagnosed with JET on a 12-lead electrocardiogram, which revealed a neonatal heart rate of 158 bpm with narrow QRS and atrioventricular dissociation. After failure to respond to amiodarone therapy, she was treated with flecainide, which controlled the JET rate from 120 to 150 bpm. Fetal tachycardia with ventriculo-atrial (VA) dissociation or 1:1 VA conduction with a shorter VA interval than that of atrioventricular reentrant tachycardia confirmed the diagnosis of fetal JET.ConclusionsJET should be suspected even in the absence of tachycardia in patients with ductus venosus and pulmonary vein retrograde flow or tricuspid and mitral regurgitation without a cardiac anomaly, as tachycardia might sometimes be intermittent in cases of JET.

An interesting response to His-synchronous ventricular stimulation: What is the mechanism of this supraventricular tachycardia?

Inappropriate therapies are frequent in patients with ICDs and are associated with adverse outcomes, including increased mortality. Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common reentrant narrow complex tachycardia and a cause of inappropriate therapies in these patients. The differential diagnosis of narrow QRS complex tachycardia with ventriculoatrial (VA) dissociation or variable block to the atrium is a pivotal role to avoid inappropriate ICD implantation or then shock therapies. This article is protected by copyright. All rights reserved.

Arrhythmias Utilizing ConcealedNodoventricular or His-Ventricular Pathways: AStructuredApproach to Diagnosis and Management.

This study sought to describe the electrophysiologic characteristics, diagnostic maneuvers, and treatment of a series of arrhythmias using concealed nodoventricular (cNV) or His-ventricular (cHV) pathways. Confirming the presence and participation of cNV or cHV pathways in tachyarrhythmias is challenging. We present 4 cases of tachycardias with a participatory cNV or cHV pathway. The first patient had a narrow complex tachycardia with ventriculoatrial dissociation. Findings of an entrainment pacing from the right ventricle and fused premature ventricular complexes suggested cNV pathway involvement. The second patient had nonsustained narrow complex tachycardia with more ventricular than atrial complexes. The tachycardia exhibited an anterograde His-right bundle (RB) activation sequence and normal His-ventricular (HV) interval and consistently terminated with fused ventricular extra stimuli, suggesting cNV pathway participation. The third patient had a wide complex tachycardia (WCT) with either a right or left bundle branch block pattern. The WCT showed an eccentric His-RB activation sequence and short HV interval and terminated with fused premature ventricular complexes, suggesting a cHV (or concealed fasciculoventricular) pathway involvement. The fourth patient had a WCT with alternating bundle branch block morphologies with a short HV interval. Entrainment from the basal right ventricle demonstrated fusion and a short postpacing interval, suggesting cHV(or fasciculoventricular) pathway involvement. Ablation at the proximal RB rendered the tachycardia noninducible. A structured approach can help diagnose and treat cNV or cHV pathways. We emphasize the importance of evaluating both the His-RB activation pattern and HV interval during sinus rhythm and tachycardia as well as the ventricular pacing study.

Abstract 11080: A Young Woman with Incessant Left Atrial Tachycardia

Introduction: Left atrial tachycardia (AT) is uncommon and usually does not occur in the absence of congenital heart disease, or prior catheter ablation (CA). Case: A 29-year-old woman with a 2-year history of SVT refractory to metoprolol and no prior CA presented to the emergency department with palpitations. Initial ECG showed a regular, narrow complex, short RP tachycardia, at 180 bpm, insensitive to adenosine and 2 electrical cardioversions. Echocardiogram showed LVEF of 40%. The patient underwent an entirely non-fluoroscopic electrophysiology study using intracardiac echocardiography and electroanatomic mapping (EAM). AT (cycle length 300 ms) was induced by programmed atrial stimulation with isoproterenol infusion. AT was confirmed with ventriculo-atrial dissociation after pacing maneuvers and adenosine administration. Right atrial (RA) activation map revealed early atrial activation in the mid coronary sinus (CS), raising suspicion of a left atrial (LA) origin. LA was accessed via transseptal puncture. The site of earliest atrial activation was in the LA wall inferior to the left inferior pulmonary vein (LIPV) ostium and was successfully terminated with radiofrequency ablation (40 W, 5 to 10 g) (Figure) with no further inducibility. The patient's symptoms resolved after the procedure. Discussion: Left AT usually originates from PVs or the atrial wall. The EAM in this patient showed centrifugal activation consistent with a focal mechanism. Adenosine is generally not helpful in terminating AT but is useful in diagnosis. Rapid conduction across the LA to CS may have given rise to early activation in the mid CS on RA mapping. However, LA mapping revealed that atrial activation was earliest in the LA wall inferior to the LIPV. Conclusion: AT is unusual in young, healthy women. A high index of suspicion to perform transseptal puncture can lead to successful ablation of AT with LA origin. We surmise that the patient’s EF may improve with termination of the tachycardia.

Fast-slow atrioventricular nodal reentrant tachycardia phenotype mimicking the slow-slow type

Abstract Background Fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is characterized by a short atrio-His (AH) interval and the earliest site of atrial activation (EAA) in the proximal coronary sinus (EAA-CS), while slow-slow (S/S-) AVNRT presents a long AH interval and EAA-CS. Those intracardiac appearances are initial indicators for making a diagnosis. Purpose To identify an unknown phenotype of F/S-AVNRT. Methods Among 46 consecutive patients with F/S-AVNRT, 6 patients (1 man, age 59±9) had an apparent but not typical (pseudo-) S/S-AVNRT during an electrophysiologic study. In 2 patients, pseudo-S/S-AVNRT was clinically documented. Results In all 6 patients, the diagnosis of F/S-AVNRT was made by an exclusion of atrial tachycardia with findings of 1) a V-A-V response following ventricular entrainment or 2) termination without atrial capture by ventricular pacing, and an exclusion of AV reentrant tachycardia with a ventriculoatrial dissociation during an initial (so-called QRS transition) zone of ventricular entrainment. An initial A-A-V activation sequence on atrial induction of F/S-AVNRT observed in 1 patient and Wenckebach-type AV block during ongoing F/S-AVNRT developing in 3 patients suggested the presence of the lower common pathway (LCP). Like the typical S/S-AVNRT, pseudo-S/S-AVNRT was induced with atrial stimulation after a jump in the AH interval or double ventricular response. However, in all patients, the pseudo-S/S-AVNRT transited to F/S-AVNRT following AV block in a single cycle and/or pseudo-S/S-AVNRT transited from spontaneously or triggered by atrial contractions. Importantly, on these transitions, the atrial cycle length (CL) and EAA-CS remained unchanged, that is, the atrial CL of S/S-AVNRT was almost identical to that of F/S-AVNRT, suggesting that the essential circuit of both tachycardias was identical. Actually, both tachycardias were cured by ablation at a single site in the traditional slow pathway (SP). Collectively, the pseudo-S/S-AVNRT was diagnosed as another phenotype of F/S-AVNRT accompanied by sustained antegrade conduction via another bystander (likely the left-sided or superior) SP breaking through the His bundle owing to the repetitive antegrade block at the LCP occurring by linking phenomenon, thus representing a long AH interval during the ongoing F/S-AVNRT. When the antegrade conduction is blocked at the bystander SP during the pseudo-S/S-AVNRT, releasing the linking phenomenon, the subsequent antegrade conduction reach the His-bundle via the fast pathway, thus returning to F/S-AVNRT. Conclusions An unknown, but not rare F/S-AVNRT phenotype exists that apparently mimics the typical S/S-AVNRT and is also an unknown subtype of apparent S/S-AVNRT. The presence of this pseudo-S/S-AVNRT suggests the limitation of classifying types of AVNRT based on AH and HA intervals during tachycardia. Understandings of this phenotype can advance a diagnosis of atypical AVNRT with multiple phenotypes. Funding Acknowledgement Type of funding sources: None.

Ventriculoatrial conduction in patients without high-grade AV block: when is it present?

Ventriculoatrial (VA) conduction is a critical component in many arrhythmias, has a diagnostic value in electrophysiology study (EPS), and is implicated in pacemaker-mediated arrhythmias. This study sought to characterize retrograde conduction during EPS and to utilize it as a diagnostic tool in patients without AV block. Patients with intact AV conduction undergoing EPS were included in this study to systematically evaluate baseline VA conduction. If absent, parahisian pacing was used to determine the level of block (nodal or infranodal). Recovery of VA conduction with increased sympathetic activity was assessed with isoproterenol infusion. Baseline characteristics and electrophysiological data were collected and analyzed. Among the 801 patients studied, VA conduction was present in 98% (81% at baseline and 17% after isoproterenol infusion). Parahisian pacing demonstrated that the block was at the AV node level among 150 patients with VA dissociation at baseline. Among patients presenting with supraventricular tachycardia (SVT), 98.7% with atrioventricular nodal reentrant tachycardia (AVNRT) had VA conduction at baseline versus 82.7% presenting with other SVT (atrial fibrillation excluded), P < 0.001. Thus, the absence of VA conduction at baseline during an EPS for SVT carries a negative predictive value (NPV) of 96.9% for AVNRT. VA conduction is present in most patients (98%) with intact AV conduction. The level of VA dissociation when present at baseline is always at the level of the AV node. Patients with SVT presenting for EPS that lacked VA conduction at baseline were unlikely to have AVNRT.

SEVEN TYPES OF PAROXYSMAL SUPRAVENTRICULAR TACHYCARDIA IN ONE PATIENT

The report describes the case of electrophysiological study and catheter ablation of seven types of supraventricular tachycardia in one patient. During radiofrequency ablation for WPW-syndrome three functionated discrete retrograde conductive accessory atrioventricular pathways were documented and were successfully ablated. Further incessant activity of two ectopic atrial focuses was revealed. First localized in upper part of crista terminalis and another – in left superior pulmonary vein ostium. Five months after patient had a recurrence of supraventricular tachycardia. EPI-study demonstrated evidence for retrograde ventriculoatrial dissociation with induction of atypical fast/slow and typical slow/fast atrioventricular nodal reentry tachycardia, wich were successfully ablated. With further observation, rhythm disturbances did not recur.

General Approach to a Wide QRS Complex.

Wide QRS complex is present when the normal activation pattern is modified by various mechanisms and clinical conditions. Correct interpretation is crucial for appropriate decision making. When approaching an electrocardiogram (ECG) with wide complex tachycardia, one must differentiate between ventricular tachycardia and supraventricular tachycardia conducted with aberrancy. ECG criteria are used and algorithms developed to aid in differential diagnosis. They are based on finding ECG signs of ventriculoatrial dissociation and QRS morphologies inconsistent with classic bundle branch block. The conditions able to modify structurally the normal activation of the heart may alter spontaneous ventricular activation during supraventricular tachycardia, creating differential diagnosis problems.

Special electrophysiological characteristics of pediatric idiopathic ventricular tachycardia

BackgroundIdiopathic ventricular tachycardia (VT) is an important pediatric arrhythmia but relevant studies in Asian cohort are rare. We determined the electrophysiological characteristics and outcomes of this rhythm disturbance. MethodsFrom an institutional database, patients aged <18years without structural heart disease who have sustained monomorphic VT (longer than 30s) during 1995–2016 were enrolled. ResultsWe enrolled 57 idiopathic VT patients (male:female=31:26). The initial presentation included palpitation (64.9%) and shock (12.3%). The electrocardiography revealed relatively short QRS duration (123±18ms) and absence of ventriculoatrial dissociation in 33.3% of the patients, causing initial misdiagnosis in 29.8% of these patients. Patients with a VT onset age of <10years were more likely to have a left bundle branch block morphology (52.2% vs. 11.8%, p=0.001) and spontaneous recovery than those with a VT onset age of ≥10years. An electrophysiology study in 44 patients revealed that the most common arrhythmia focus was the left ventricular septal area (78%), called fascicular VT. Radiofrequency ablation showed a satisfactory success rate (90%) and fair recurrence rate (14.3%). Tachycardia-induced cardiomyopathy was noted in 14% of the VT patients and cardiac function returned to normal in 1–18months (median, 3months) after successful ablation. ConclusionsIn an Asian pediatric population, VT has distinct electrophysiological characteristics including dominant left ventricular origin, narrower QRS duration, and more symptomatic presentation. Transcatheter ablation is effective against VT, and the associated cardiomyopathy often resolves rapidly after successful ablation.

Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a "Superior" Slow Pathway: A Distinct Supraventricular Tachyarrhythmia.

The existence of an atypical fast-slow (F/S) atrioventricular nodal reentrant tachycardia (AVNRT) including a superior (sup) pathway with slow conductive properties and an atrial exit near the His bundle has not been confirmed. We studied 6 women and 2 men (age, 74 ± 7 years) with sup-F/S-AVNRT who underwent successful radiofrequency ablation near the His bundle. Programmed ventricular stimulation induced retrograde conduction over a superior SP with an earliest atrial activation near the His bundle, a mean shortest spike-atrial interval of 378 ± 119 milliseconds, and decremental properties in all patients. sup-F/S-AVNRT was characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia in 5 patients or atrioventricular block occurring during tachycardia in 3 patients, excluding atrioventricular reentrant tachycardia; termination of the tachycardia by ATP; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses in 2 patients. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT in 4 patients each. sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP located above the Koch triangle as the retrograde limb, that can be eliminated by radiofrequency ablation.

Should you be worried?

The ECG in Fig. 1 shows a QRS tachycardia with a QRS duration of 146 ms and a frequency of 160 beats/min. There is a left axis deviation and a complete right bundle branch block. It is important to make a differentiation between ventricular tachycardia (VT) and supraventricular tachycardia (SVT). Signs suggestive of both a ventricular and supraventricular origin are present in our patient. The tachycardia was terminated by adenosine. This is (usually) suggestive of a supraventricular origin. So differential diagnostic paroxysmal SVT conducted with aberrancy is a possibility because of its relatively narrow QRS. The presence of ventriculoatrial dissociation in the electrocardiogram makes the diagnosis of VT stronger. If assuming a ventricular origin, VT originating in or near the Purkinje system (fascicular VT or idiopathic left ventricular VT) is likely. Fig. 1 Twelve-lead ECG during and after conversion to sinus rhythm In 1979, Zipes et al. were the first to identify the electrophysiological characteristics of an idiopathic VT. In 1981 Belhassen et al. described the use of verapamil in this VT, which is refractory to conventional treatment [1]. Therefore, this VT is commonly referred to as Belhassen, verapamil-sensitive or fascicular VT. It is characterised by a right bundle branch block pattern and left axis deviation (left posterior fascicle). A right axis deviation is less frequently noted. The prevalence is unknown but patients are typically young and healthy when their first episode occurs. It is more common in males than females. The mechanism of the tachycardia is postulated to be triggered activity or reentry involving the left-sided Purkinje system and abnormal Purkinje or myocardial tissue [2]. The termination of fascicular VT usually requires intravenous antiarrhythmic medication. In patients with frequent or symptomatic fascicular VT long-term medication may be required. Patients with recurrent refractory episodes of VT may be referred for radiofrequency ablation. The prognosis of fascicular VT is good, in just a few cases it can result in a tachycardia-induced cardiomyopathy. Syncope and sudden death are extremely rare [3].

Should you be worried?

The ECG in Fig. 1 shows a QRS tachycardia with a QRS duration of 146 ms and a frequency of 160 beats/min. There is a left axis deviation and a complete right bundle branch block. It is important to make a differentiation between ventricular tachycardia (VT) and supraventricular tachycardia (SVT). Signs suggestive of both a ventricular and supraventricular origin are present in our patient. The tachycardia was terminated by adenosine. This is (usually) suggestive of a supraventricular origin. So differential diagnostic paroxysmal SVT conducted with aberrancy is a possibility because of its relatively narrow QRS. The presence of ventriculoatrial dissociation in the electrocardiogram makes the diagnosis of VT stronger. If assuming a ventricular origin, VT originating in or near the Purkinje system (fascicular VT or idiopathic left ventricular VT) is likely. Fig. 1 Twelve-lead ECG during and after conversion to sinus rhythm In 1979, Zipes et al. were the first to identify the electrophysiological characteristics of an idiopathic VT. In 1981 Belhassen et al. described the use of verapamil in this VT, which is refractory to conventional treatment [1]. Therefore, this VT is commonly referred to as Belhassen, verapamil-sensitive or fascicular VT. It is characterised by a right bundle branch block pattern and left axis deviation (left posterior fascicle). A right axis deviation is less frequently noted. The prevalence is unknown but patients are typically young and healthy when their first episode occurs. It is more common in males than females. The mechanism of the tachycardia is postulated to be triggered activity or reentry involving the left-sided Purkinje system and abnormal Purkinje or myocardial tissue [2]. The termination of fascicular VT usually requires intravenous antiarrhythmic medication. In patients with frequent or symptomatic fascicular VT long-term medication may be required. Patients with recurrent refractory episodes of VT may be referred for radiofrequency ablation. The prognosis of fascicular VT is good, in just a few cases it can result in a tachycardia-induced cardiomyopathy. Syncope and sudden death are extremely rare [3].

Metastatic Melanoma of the Right Ventricular Outflow Tract as a Cause of Ventricular Tachycardia

A 47-year-old woman with a history of melanoma metastatic to her stomach and esophagus presented with palpitations and shortness of breath. Her heart rate was 182 beats/min and her blood pressure was 124/54 mmHg. A new grade 3/6 systolic murmur was present over the left precordium. An electrocardiogram showed a wide QRS complex tachycardia with left bundle branch block, inferior axis, and ventriculoatrial dissociation compatible with a right ventricular outflow tract (RVOT) ventricular tachycardia (Fig. 1). She was cardioverted to sinus rhythm. After cardioversion, she displayed an rSR' QRS morphology in lead V1 and T-wave inversions, with a slow S-wave upstroke in the anterior precordial leads (V1 and V2) (Fig. 2). These findings are associated with right ventricular conduction delay and cardiomyopathy. She had no electrolyte abnormalities. Fig. 1 The 12-lead electrocardiogram at presentation shows a wide QRS complex tachycardia with left bundle branch, inferior axis, and ventriculoatrial dissociation (arrows point to P waves). Fig. 2 Post-cardioversion 12-lead electrocardiogram shows an rSR' QRS morphology in lead V1, as well as T-wave inversions and a slurred S-wave upstroke in the anterior precordial leads. A nuclear stress test showed normal left ventricular function and perfusion. Imaging with both transthoracic echocardiography (Fig. 3) and cardiac magnetic resonance (CMR) (Fig. 4) revealed a mass infiltrating the RVOT. On both T1- and T2-weighted imaging, the mass had high signal intensity consistent with melanoma.1,2 Unfortunately, the mass was inoperable, the patient was not a candidate for further chemotherapy, and she died one year later. Fig. 3 A) Transthoracic echocardiogram (basal short-axis view) shows a mass infiltrating the right ventricular outflow tract (arrow). B) Color-flow Doppler mode at the same location shows turbulent flow in the right ventricular outflow tract as a result of the ... Fig. 4 Cardiac magnetic resonance image shows a mass in the right ventricular outflow tract (*) with high signal intensity on both A) T1-weighted and B) T2-weighted imaging. LV = left ventricle; RV = right ventricle

Sustained Tachycardia in a Cardiac Resynchronization Therapy Recipient: What Is the Mechanism of Tachycardia?

A 67-year-old female with prior circumflex arterial territory myocardial infarction, impaired contractile function (ejection fraction 35%), coronary artery bypass grafting (CABG), renal transplantation with a well-functioning graft, and a cardiac resynchronization therapy defibrillator (CRT-D; Cognis, Boston Scientific, Natick, MA, USA) was seen in the device clinic with acute onset of breathlessness and palpitations. She has had a 1-year history of recurrent symptomatic ventricular tachycardia (VT), refractory to antiarrhythmic agents including amiodarone, and two unsuccessful endocardial ablations. Electrocardiography (ECG) shows an incessant, monomorphic broad complex tachycardia (cycle length of around 470 ms, right bundle branch morphology, right superior axis, and concordantly tall R waves in the chest leads) below the programmed VT detection zone, which was set at 400 ms (Fig. 1). BP was 100/60 mmHg. There was ventriculo-atrial dissociation with more ventricular than atrial events during tachycardia, confirming the diagnosis of VT. During attempts to terminate VT by overdrive pacing from the left ventricular (LV) lead, the electrograms in Figure 2(A) were recorded. Once VT was terminated by overdrive pacing, the following electrograms in Figure 2(B) were recorded during pacing from the

Cryoablation and Angiographic Evidence of a Concealed Right Atrial Appendage to Right Ventricle Accessory Pathway in an Infant

We report a case of successful cryoablation of a concealed accessory pathway from the right atrial appendage to the right ventricle in an infant. A 4-month-old female who had previously undergone successful ablation of a left-sided accessory pathway was taken to the electrophysiology lab due to recurrent supraventricular tachycardia. While in this second supraventricular tachycardia, we found earliest atrial activation in the distal right atrial appendage. Angiography confirmed a connection between right atrial appendage and the right ventricle. Cryoablation at this location promptly terminated the supraventricular tachycardia. Following ablation, there were no further inducible arrhythmias and ventriculo-atrial dissociation was appreciated.

Choice and Utility of Pacing Maneuver in Establishing the Mechanism of Supraventricular Tachycardia: A Single Center Experience.

BackgroundTo evaluate the choice and utility of pacing maneuvers in the electrophysiology (EP) laboratory in establishing supraventricular tachycardia (SVT) mechanism.MethodsWe retrospectively examined a cohort of 160 consecutive patients with SVT presenting for invasive EP evaluation to a single center with 8 electrophysiologists. We analyzed the utility of the two most commonly used pacing maneuvers: (1) ventricular entrainment (VE) and (2) His-refractory premature ventricular stimuli (HRPVC) during SVT.ResultsVE was performed in 96 patients: atrial tachycardia (AT) 12, atrioventricular nodal reentrant tachycardia (AVNRT) 66, and orthodromic reciprocating tachycardia (ORT) 18. During VE, AT patients were most likely to have ventriculo-atrial (VA) dissociation (AT 58%, AVNRT 18%, ORT 0%, P < 0.001) and had a tendency towards less SVT termination (AT 0%, AVNRT 9%, ORT 11%, P = 0.19). HRPVCs were delivered in 39 patients: AT 1, AVNRT 24, and ORT 14. Advancement of atrial signal with HRPVC was only observed in ORT (AT 0%, AVNRT 0%, ORT 79%, P < 0.001) and SVT termination was also mostly observed in ORT (AT 0%, AVNRT 4%, ORT 21%, P = 0.33). The overall diagnostic utility of VE was lowest in AT (AT 42%, AVNRT 71%, ORT 83%, P = 0.04), while HRPVC was rarely used in AT. Furthermore, the utilization of maneuvers varied extensively (0% to100%) among the 8 electrophysiologists.ConclusionThere is great variation in the utilization of pacing maneuvers and their utility in ascertaining the mechanism of SVT. Our results support the fact that discerning AT from AVNRT mechanism remains the most challenging task in SVT diagnosis.