Left Bundle Branch Block Configuration Research Articles

291 BIVENTRICULAR ARRHYTMOGENIC CARDIOMYOPATHY: COULD ELECTROCARDIOGRAPHY SEE BEYOND THE CARDIAC MRI?

Abstract We described the case of a 34 year-old young athlete who was referred to our Department because of palpitations and fatigue, arising after hard effort but also present at rest. Family history was unremarkable for sudden cardiac death or cardiomyopathies. Electrocardiography (ECG) evidenced multifocal premature ventricular contractions (PVCs): left bundle branch block (LBBB) morphology and superior/inferior axis; right bundle branch block (RBBB) morphology and undetermined axis. Cardiac MRI showed extensive mid wall and subepicardial late gadolinium enhancement in the postero-lateral left ventricular wall. We decided to perform electroanatomic mapping (EAM) because we didn't explain the origin of the PVCs with LBBB configuration. During EAM we found an area extending from the right ventricular outflow tract to the subtricuspidal lateral inferior wall which it had not described by cardiac MRI. In the low voltage areas, the electrograms inscribed by the catheter's electrodes was fractionated with different waveforms, a finding that corresponds to a deficiency of healthy myocardial tissue. We performed an endomyocardial biopsy in the interventricular septum close to the ventricular out flow tract. The histological examination of the biopsy samples showed fibro-fatty replacement. Therefore genetic testing revealed a pathogenic desmoplakin mutation. According to “Padua Criteria”, we made a diagnosis of biventricular arrhythmogenic cardiomyopathy. We finally implanted a transvenous cardioverter defibrillator. Conclusion Diagnosis of arrhythmogenic cardiomyopathy (ACM) is complex and requires the combination of multiple clinical, histological and genetic parameters. This clinical case demonstrated that ECG represent an essential tool in diagnostic work-up of the disease, and electroanatomic mapping is useful in selected cases for the documentation of the diagnosis of arrhytmogenic cardiomyopathy.

Two P waves followed by 1 QRS complex: What is the mechanism?

A 71-year-old man with a history of inferior myocardial infarction was referred to the hospital for management of subarachnoid hemorrhage. The baseline 12-lead electrocardiogram showed sinus rhythm with a left bundle branch block configuration as well as 2:1 atrioventricular (AV) block (Figure 1A). After several hours, the electrocardiogram exhibited a slower rhythm with a right bundle branch block pattern following 2 narrow P waves (red arrows, Figure 1B). The slow ectopic rhythm converted to sinus rhythm after a spontaneous premature ventricular complex (PVC).

Incidence of outflow tract ventricular tachycardia long after surgical aortic valve replacement.

BackgroundThe peri‐outflow tract region could be the origin of ventricular tachycardia (VT) after aortic valve replacement (AVR). However, the clinical characteristics of outflow tract ventricular tachycardias (OTVTs) after AVR are yet to be clarified. This study investigated the incidence, risk factors, and clinical characteristics of patients with OTVTs after AVR.MethodsWe retrospectively analyzed the clinical course of 120 patients who had undergone surgical AVR (SAVR) between April 1980 and October 2018. The patients had no ischemic or diagnosed cardiomyopathies other than primary aortic valve diseases.ResultsSix patients (5.0%) developed OTVTs after SAVR. The average onset was at 10.8 ± 5.7 years after SAVR. All cases of VT arose from the inferior axis and included left and right bundle branch block configuration. Two patients who underwent cardiac magnetic resonance imaging (MRI) had late gadolinium enhancement (LGE) in the midlayer of the left ventricle basal anteroseptal wall. Patients with periaortic VTs had significantly larger left ventricular (LV) diameter at systole, lower LV ejection fraction, higher positive rates of signal‐averaged electrocardiogram (SAECG), and nonsustained VTs on Holter monitoring. On ablation, local fragmented potentials with low voltage zones were observed in accordance with the LGE distribution. Multiple VTs originating from the periaortic region were provoked in the sessions.ConclusionsAcute OTVT was found in 5% of patients after SAVR. Arrhythmia risk stratification by SAECG, Holter ECG, and cardiac MRI should be considered for a long period in patients after SAVR.

P2630Incidence and prognostic impact of new-onset left bundle branch block in patients with heart failure and reduced ejection fraction

Abstract Background Cardiac resynchronization therapy (CRT) improves survival in patients with heart failure, reduced ejection fraction (HFrEF) and left bundle branch block (LBBB). However, little is known about the incidence of LBBB in HFrEF and the risk factors for developing this. We addressed these questions in the PARADIGM-HF and ATMOSPHERE trials. Methods We identified 7703 patients with a non-paced rhythm on their baseline ECG, a QRS<130 ms, and at least one follow-up ECG (done at annual visits and end of study). Patients were stratified by baseline QRS duration (≤100 ms - reference; 101–115 ms and 116–129 ms) and followed until development of QRS duration ≥130 ms with a LBBB configuration or latest available ECG. The crude LBBB incidence rate per 100 person-years (py) was identified in the three QRS duration subgroups. Additionally, we examined risk of the primary composite outcome of cardiovascular death or HF hospitalization, and all-cause mortality, in patients with incident LBBB vs. no incident LBBB. Results Overall, 313 of 7703 patients (4%) developed LBBB during a mean follow-up of 2.7 years, yielding an incidence rate of 1.5 per 100 py. The rate ranged from 0.9 in those with QRS ≤100 ms to 4.0 per 100 py in patients with QRS 116–129 ms. Other predictors of incident LBBB included male sex, age, lower LVEF, HF duration and absence of AF. The risk of the primary composite endpoint was higher among those who developed incident LBBB vs no incident LBBB; event rates 13.5 vs 10.0 per 100 py, yielding an adjusted HR of 1.43 (1.05–1.96). For all-cause mortality the corresponding rates were 12.6 vs 7.3 per 100 py; HR 1.55 (1.16–2.07) (Table 1). Table 1. Risk of outcomes according to incident LBBB during follow-up No. events Crude rate per 100py Adjusted* HR (95% CI) HF hospitalization or CV death No incident LBBB 2145 10.0 (9.6–10.4) 1.00 (ref.) Incident LBBB 43 13.5 (10.0–18.2) 1.43 (1.05–1.96) All-cause mortality No incident LBBB 1662 7.3 (6.9–7.6) 1.00 (ref.) Incident LBBB 48 12.6 (9.5–16.7) 1.55 (1.16–2.07) Conclusion Among patients with HFrEF, the annual incidence of new-onset LBBB (and a potential indication for CRT), was around 1.5%, ranging from 1% in those with QRS duration below 100 ms to 4% in those with QRS 116–129 ms. Incident LBBB was associated with a much higher risk of adverse outcomes, highlighting the importance of repeat ECG monitoring in patients with HFrEF. Acknowledgement/Funding Novartis

Long-Term Effect of Different Optimizing Methods for Cardiac Resynchronization Therapy in Patients with Heart Failure: A Randomized and Controlled Pilot Study

Aim: During cardiac resynchronization therapy (CRT), optimized programming of the atrioventricular (AV) delay and ventricular-to-ventricular (VV) interval can lead to improved hemodynamics, symptomatic response, and left ventricular systolic function. Currently, however, there is no recommendation for the best optimization method. This study aimed to compare the long-term clinical outcomes of 4 different CRT optimization methods. Methods: One hundred and twenty-four consecutive CRT patients with severe heart failure and left bundle-branch block configuration were randomly assigned into four groups to undergo AV/VV delay optimization through echocardiogram (ECHO; n = 30), electrocardiogram (ECG; n = 32), QuickOpt algorithm (n = 28), and nominal AV/VV (n = 36) groups. Patients were followed up and underwent examinations, including New York Heart Association (NYHA) cardiac functional classification, 6-min walking distance (6MWD), and echocardiography, at 6, 12, 24, 36, and 48 months, respectively. The patients’ survival and clinical outcomes were compared among the four groups. Results: Kaplan-Meier survival analyses showed that the median survival was the same in the 4 groups: ECHO, 43 months; ECG, 44 months; QuickOpt, 44 months, and nominal, 41 months. At the 6-month follow-up, the reduction in left ventricular end diastolic diameter (LVEDD) was significantly less in the nominal group (–1.91 ± 2.58 mm) than that in the other three groups (ECHO: –3.70 ± 2.78 mm, p = 0.012; ECG: –3.53 ± 3.14 mm, p = 0.020; QuickOpt: –3.46 ± 2.65 mm, p = 0.032); 6MWD was significantly shorter in the nominal group (87.88 ± 34.76 m) than that in the other three groups (ECHO: 120.63 ± 56.93 m, p = 0.006; ECG: 114.97 ± 54.95 m, p = 0.020; QuickOpt: 114.57 ± 35.41 m, p = 0.027). Left ventricular ejection fraction (LVEF) significantly increased in ECHO (7.23 ± 2.76%, p = 0.010), ECG (8.50 ± 3.17%, p < 0.001), and QuickOpt (8.39 ± 2.90%, p < 0.001) compared with the nominal group (5.35 ± 2.59%). There were no significant differences among the groups in the aforementioned parameters at 24, 36, and 48 months, respectively. Conclusion: While LVEDD, LVEF, 6MWD, and NYHA were significantly improved in ECHO, ECG, and QuickOpt at 6 months, there were no significant improvements in any of the groups at 12, 24, and 48 months. These findings suggested that the long-term effect of the four CRT methods for heart failure was not significantly different.

Cardiac resynchronization therapy response in heart failure patients with different subtypes of true left bundle branch block

Left bundle branch block (LBBB) configuration has been described as a predictor of response to cardiac resynchronization therapy (CRT). We investigated whether different subtypes of true LBBB configuration could help select patients with better response and clinical outcome. This retrospective study included 198 consecutive LBBB patients implanted with a CRT. True LBBB was defined using the Strauss and the Predict study criteria. Echocardiographic response was evaluated by the reduction in left ventricular end-systolic volume (LVESV) and the increase in left ventricular ejection fraction (LVEF). Clinical response was defined as an improvement in one category of the NYHA functional class. Patients with true LBBB had a greater improvement in both LVESV reduction (median = - 27.6%, interquartile range = [- 4.9, - 50.1]) and LVEF increase (median 10.8 ± 10) than those with non-true LBBB (- 19.7%, [16.7, - 48.0]) p = 0.04 and 5.1 ± 10, p = 0.03, respectively. No differences were exhibited between true LBBB Strauss group (- 26.7%, [- 11.0, - 46.9]) and true LBBB Predict group (- 26.6%, [- 15.9, - 39.4]). There were no statistically significant differences in the percentage of patients with clinical response, assessed by NYHA improvement, among all groups. In the Cox model for death, age, ischemic etiology, and ΔLVESV were independent predictors of mortality. True LBBB (Strauss + Predict) patients had a trend towards lower mortality than non-true LBBB [HR = 0.55, 95% CI = (0.22-1.15)], p = 0.08. In the Cox model for HF hospitalization, age, sex male, prior LVEF, and ΔLVESV were independent predictors. True LBBB (Strauss + Predict) patients had a significantly lower risk of developing HF hospitalization than those with non-true LBBB [0.45 (0.21-0.90)], p = 0.029. Patients with true LBBB, either Strauss or Predict criteria, had greater echocardiographic response and lower incidence of HF hospitalization than non-true LBBB when implanted with CRT.

Atrial tachycardia with Wenckebach atrioventricular conduction mechanism: What is the origin of the beat following the pause?

Case presentation A 65-year-old woman was suffering from recurrent paroxysmal atrial fibrillation and was being treated with propafenone 150 mg tid. Continuous ECG recording strips of lead V1 are shown in Figure 1. The QRS complexes are associated into groups separated from each other by pauses. Although several P waves are not clearly discernible because they are superimposed on the T waves, analysis of the recordings reveals regular atrial activity with P-P intervals of 520 ms (Figure 2). Often the P waves are partially buried within a coincidental ventricular complex, causing subtle QRS alterations that result in relatively wide “pseudo-r” waves. This occurs with the fourth beat in the top strip of Figure 1, the 13th beat of the middle strip, and the third beat of the bottom strip. The P-R intervals undergo progressive prolongation until a ventricular pause occurs. Such a sequence indicates a Wenckebach atrioventricular (AV) nodal conduction mechanism. During the tachycardia, the morphology of the QRS complexes is typical for left bundle branch block (LBBB). However, the ventricular beats that follow a pause at times are relatively narrow but on other occasions show an LBBB configuration. These late QRS complexes are clearly dissociated from, and independent of, the near-synchronous P wave (Figures 1 and 2). What is the mechanism underlying the beats ending the pauses?

Upgrading and replacement in CRT devices: experience counts.

Cardiac resynchronisation therapy has proven to be highly effective in patients with heart failure and an asynchronous contraction pattern of the left ventricle, due to late activation of the posterolateral wall with left bundle branch block configuration on the ECG of more than 150 ms [1]. In pacemaker patients with a high percentage of right ventricular pacing, pacing-induced left ventricular (LV) dysfunction can appear. This newly developing heart failure is most probably the result of pacing-induced LV asynchrony. These patients with pacing-induced heart failure and ICD patients with heart failure who develop a wide QRS complex during follow-up account for the majority of patients who are eligible for an upgrade to a CRT device. In an European survey, up to 25 % of CRT implants were upgrading procedures [2]. The REPLACE registry demonstrated a high percentage of complications in upgrade and revision procedures in 434 CRT patients from 71 centres. It was not stated how many centres actually contributed to this total number of CRT upgrades [3]. Their conclusion ‘pacemaker and implantable cardioverter-defibrillator generator replacements are associated with a notable complication risk, particularly those with lead additions’ made cardiologists somewhat cautious and even reluctant to perform a therapeutic upgrade to CRT. These REPLACE data support careful decision making before device replacement when managing device advisories and when considering upgrades to more complex systems, concluded the authors [3]. And indeed, an upgrade procedure can be complicated and is in need of an experienced skilled operator or at least her or his direct supervision during the procedure. As experience is a major factor in reducing complications during and after device implantation [4], it is reasonable that experience is an even stronger denominator in complicated procedures as primary CRT implants and CRT upgrades. In this issue, the retrospective data of upgrading procedures to CRT devices were compared with the complications in primary CRT implants during the same period [5]. These retrospective data originate from one tertiary centre with a high patient load. Only three experienced operators performed the majority of procedures or supervised them. A: Total number of individual implants of 165 (62 %), including 82 upgrade procedures. Thirty assists of which 16 assists in an upgrade procedure. B: Total number of individual implants of 30 (11 %), including 13 upgrade procedures. Six assists of which 4 assists in an upgrade procedure. C: Total number of individual implants of 18 (7 %), including 9 upgrade procedures. Three assists of which 0 assists in an upgrade procedure. Though these data are retrospective, the complication rate is considerably lower when compared with the literature [3]. The most determining factor in the difference of complication rate is most likely skill, which comes from experience and cooperation during these complicated procedures. It was not investigated whether the determining factor was cooperation or experience or its combination.

Changes in QRS morphology during atrial fibrillation: What is the mechanism?

Case presentation The electrocardiogram shown in Figure 1 has been recorded from a 58-year-old man suffering from hypertension, thyrotoxicosis, and permanent atrial fibrillation. He was on propranolol, methimazole, and warfarin. The tracing (lead V1) shows atrial fibrillation with an average ventricular rate of 90 beats/min. The QRS complex morphology is variable: most beats show a left bundle branch block (LBBB) configuration, but in some complexes a right bundle branch block (RBBB) pattern or a normal morphology is evident. What is the mechanism underlying such a marked QRS variability?

A case of arrhythmogenic right ventricular cardiomyopathy in a 70-year-old patient.

A 70-year-old man was admitted because of syncope and dyspnea. Two months before admission, exertional dyspnea occurred with syncope. Ventricular tachycardia with a monomorphic left bundle-branch block configuration was detected. An echocardiographic examination showed severe dilatation and diffuse, severe hypokinesis of the right ventricle, with thrombus formation in the right ventricular apex. Based on the clinical picture, the patient was diagnosed with arrhythmogenic right ventricular cardiomyopathy (ARVC). This case emphasizes the need for early identification of RV abnormalities in patients with ARVC to determine appropriate therapy.

Programmed versus Effective VV Delay during CRT Optimization: When What You See Is Not What You Get

In cardiac resynchronization therapy (CRT) devices, the interventricular (VV) delay denotes the time interval between left (LV) and right ventricular (RV) pacing. This study aimed to determine the proportion of patients in whom the effective VV delay (VVeff , delay between LV and RV depolarization, being induced either by pacing or intrinsic conduction) is different from the programmed VV delay during a standard VV delay optimization procedure. Thirty-three patients with heart failure and left bundle branch block configuration without total atrioventricular (AV) block receiving CRT were prospectively included. VVeff was calculated from intrinsic AV intervals, programmed optimal AV delay, and programming system. Intrinsic AV intervals were measured on intracardiac electrograms. The optimal AV and VV delays were determined by highest increase in maximum rate of LV pressure rise (dP/dtmax ). VV delays of 20-80 ms LV and RV preactivation were tested. Calculated maximum possible VVeff was shorter than 80 ms LV preactivation in up to 46% of patients and shorter than 40 ms LV preactivation in up to 3% of the patients. These proportions were 6% and 0% during 80 and 40 ms RV preactivation, respectively. In CRT patients with left bundle branch block without total AV block, the effective VV delay is shorter than the programmed VV delay during a standard optimization procedure in approximately half of the patients and this phenomenon is encountered predominantly during LV preactivation by 40 ms or more. Calculation of the individual maximum VVeff in advance can shorten the VV delay optimization procedure.

Delayed-Onset Complete Atrioventricular Block in a Patient with Murine Typhus Myocarditis

Murine typhus is a flea-borne infectious disease caused by Rickettsia typhi, of which myocarditis is a rare complication in the acute disseminating phase. A 62-year-old female presented with a fever and was diagnosed with murine typhus. She was treated with doxycycline and discharged after complete resolution of the fever. However, recurrent presyncope and exertional dyspnea developed 6-8 weeks later. Complete atrioventricular (AV) block with a wide QRS escape rhythm and a left bundle branch block configuration was documented. Subacute myocarditis was diagnosed based on persistent cardiac troponin-I elevation and typical cardiac magnetic resonance imaging findings. A permanent pacemaker was implanted for symptomatic complete AV block. Few reports of myocarditis in murine typhus have been published. We report a case of murine typhus myocarditis complicated by complete AV block in the late convalescence phase. (Korean J Med 2013;84:723-727)

Successful Catheter Ablation of Bidirectional Ventricular Premature Contractions Triggering Ventricular Fibrillation in Catecholaminergic Polymorphic Ventricular Tachycardia With RyR2 Mutation

The subject of this report is a 38-year-old woman who often experienced syncope since childhood. Syncope occurred >10 times a year and was associated with convulsion during exercise and emotionally exciting situations. The patient's 13-year-old daughter had also experienced frequent episodes of syncope and developed ventricular fibrillation (VF) during treadmill exercise testing that was successfully defibrillated with electric shock. Witnessing this situation, the patient also lost consciousness, with documented VF that was converted to sinus rhythm by cardiopulmonary resuscitation without electric defibrillation. Both the patient and her daughter were admitted to our hospital. We performed echocardiography, coronary angiography, and cardiac CT, the results of which revealed no structural heart disease. Resting 12-lead ECG did not indicate any abnormalities, including long-QT syndrome or Brugada syndrome. A signal-averaged ECG revealed no late potentials. Treadmill exercise testing easily induced bigeminal ventricular premature contractions (VPCs) with a right bundle branch block configuration and inferior axis (Figure 1A), and the exercise was terminated because of intolerable symptoms. Catecholamine stress test was started with administration of continuous intravenous infusion of epinephrine in a stepwise manner from 0.025 μg/kg per minute.1 During epinephrine infusion at a rate of 0.1 μg/kg per minute, multifocal VPCs (VPC #1, right bundle branch block configuration and superior axis; VPC #2, right bundle branch block configuration and inferior axis [the same VPC configuration as that induced during the treadmill exercise testing]; and VPC #3, left bundle branch block configuration and inferior axis) appeared, and VPC #1 following VPC #2 subsequently induced VF (Figure 1B). Figure 1. A , Twelve-lead ECG recording during treadmill exercise testing. Bigeminal ventricular premature contractions (VPCs) appeared during the second stage of the Bruce protocol. VPC morphology …

Radiofrequency Catheter Ablation for Unifocal Premature Ventricular Complexes Triggering Recurrent Ventricular Fibrillations in a Young Man Without Structural Heart Disease

A 17-year-old man was referred for aborted sudden cardiac death. Ventricular fibrillation (VF) was recorded by automated external defibrillator. Post-resuscitation electrocardiograms showed frequent monomorphic premature ventricular complexes (PVCs), with left bundle branch block configuration and inferior axis. Cardiac arrest due to VF recurred twice within the initial 42 hours. Rhythm monitoring revealed multiple episodes of sustained VF triggered by a triplet of monomorphic PVCs having similar morphology with isolated PVCs. Comprehensive cardiologic workup revealed no structural heart disease and ion-channelopathies. With the impression of idiopathic VF triggered by unifocal PVCs of right ventricular outflow tract (RVOT) origin, radiofrequency catheter ablation was performed to prevent frequent VF recurrence before implantable cardioverter-defibrillator (ICD) implantation. After successful ablation of the origin of unifocal PVCs at anterolateral wall of RVOT, the burden of PVCs decreased remarkably and VF did not recur. The patient was discharged after ICD implantation.

Usefulness of the 12-lead electrocardiogram in the follow-up of patients with cardiac resynchronization devices. Part II

The interval from the pacemaker stimulus to the onset of the earliest paced QRS complex (latency) may be prolonged during left ventricular (LV) pacing. Marked latency is more common with LV than right ventricular (RV) pacing because of indirect stimulation through a coronary vein and higher incidence of LV pathology including scars. During simultaneous biventricular (BiV) pacing a prolonged latency interval may give rise to an ECG dominated by the pattern of RV pacing with a left bundle branch block configuration and commonly a QS complex in lead V1. With marked latency programming the V-V interval (LV before RV) often restore the dominant R wave in lead V1 representing the visible contribution of the LV to overall myocardial depolarization. When faced with a negative QRS complex in lead V1 during simultaneous BiV pacing especially in setting of a relatively short PR interval, the most likely diagnosis is ventricular fusion with the intrinsic rhythm. Fusion may cause misinterpretation of the ECG because narrowing of the paced QRS complex simulates appropriate BiV capture. The diagnosis of fusion depends on temporary reprogramming a very short atrio-ventricular delay or an asynchronous BiV pacing mode. Sequential programming of various interventricular (V-V) delays may bring out a diagnostic dominant QRS complex in lead V1 that was previously negative with simultaneous LV and RV apical pacing even in the absence of an obvious latency problem. The emergence of a dominant R wave by V-V programming strongly indicates that the LV lead captures the LV from the posterior or the posterolateral coronary vein and therefore rules out pacing from the middle or anterior coronary vein. In some cardiac resynchronization systems LV pacing is achieved with the tip electrode of the LV lead as the cathode and the proximal electrode of the bipolar RV as the anode. This arrangement creates a common anode for both RV and LV pacing. RV anodal capture can occur at a high LV output during BiV pacing when it may cause slight ECG changes. During LV only pacing (RV channel turned off) RV anodal pacing may also occur in a more obvious form so that the ECG looks precisely like that during BiV pacing. RV anodal stimulation may complicate threshold testing and ECG interpretation and should not be misinterpreted as pacemaker malfunction. Programming the V-V interval (LV before RV) in the setting of RV anodal stimulation cancels the V-V timing to zero.

Electrocardiographic versus Echocardiographic Optimization of the Interventricular Pacing Delay in Patients Undergoing Cardiac Resynchronization Therapy

Echocardiographic optimization of the VV interval may improve CRT response, but it is time-consuming and not routinely performed. The aim of this study was to compare the response to cardiac resynchronization therapy (CRT) when the interventricular pacing (VV) interval was optimized by tissue Doppler imaging (TDI) to CRT response when it was optimized following QRS width criteria. The study included 156 consecutive CRT patients with severe heart failure and left bundle-branch block configuration. Atrioventricular interval was selected according to a pulsed Doppler assessment, and VV optimization was randomly assigned to echocardiography (ECHO group, n = 78) or electrocardiography (ECG group, n = 78). Optimal VV was defined for the ECHO group as producing the best LV intraventricular synchrony according to TDI displacement curves and for the ECG group as resulting in the narrowest QRS measured from the earliest deflection. At 6-month follow-up, percentage of echocardiographic responders (defined as neither death nor heart transplantation and a LV end-systolic volume reduction >10%) was higher in the ECG optimized group (50.0% vs 67.9%; P = 0.023), whereas clinical response (defined as neither death nor heart transplantation and >10% improvement in the 6-minute walking test) was similar in both groups (71.8% vs 73.1%; P = 0.858). VV optimization based on QRS width obtained a higher percentage of responders in terms of LV reverse remodeling compared to the TDI method.

Reversal of left bundle and His bundle potentials during wide complex tachycardia: What is the mechanism?

Case presentation A 14-year-old male patient presented to our institution with a wide complex tachycardia. An echocardiogram showed an ejection fraction of 60%, moderate mitral and tricuspid regurgitation, mild aortic regurgitation, and moderate pulmonary hypertension. He had a history of 2 prior ablations at another institution. During his first procedure, he was found to have ventricular tachycardia with a right bundle branch block, left superior axis morphology at a cycle length of 375 ms. Cryoablation was performed along the mid-left ventricular septum, after which the patient developed a left posterior fascicular block pattern during sinus rhythm. The next day, the patient developed ventricular tachycardia with a right bundle branch block, right inferior axis morphology. Ablation was targeted in the region of the left anterior fascicle and rendered the tachycardia noninducible. After the procedure, the electrocardiogram demonstrated a left bundle branch block configuration. Several months later, the patient presented to our institution in a wide complex tachycardia with a left bundle branch block, left superior axis morphology. Electrocardiograms during sinus rhythm and tachycardia are shown (Figures 1A and 1B). During electrophysiological study, baseline AH and HV intervals were 87 ms and 55 ms, respectively. The HV remained constant during incremental atrial pacing. Tachycardia was reproducibly induced with rapid atrial and ventricular pacing, and had a cycle length of 370 ms and an HV interval of 55 ms. Atrial activity was dissociated from the tachycardia. Adenosine 24 mg had no effect on tachycardia cycle length. Intracardiac tracings during sinus rhythm (Figure 2) and tachycardia (Figure 3) are shown. What is the mechanism of the wide complex tachycardia?

Idiopathic Reentrant Right Ventricular Outflow Tract Tachycardia With Presystolic Potential of Central Pathway

A 12-year-old girl with recurrent palpitation due to idiopathic ventricular tachycardia (VT) with a left bundle branch block configuration and inferior axis was referred to our hospital. During the VT, a spiky presystolic potential (SP) was recorded at the septum of right ventricular outflow tract (RVOT) just below pulmonary valve. The SP was entrained with a decremental property by pacing from right ventricular apex. Concealed entrainment was observed by pacing where the SP was recorded. Delivery of radiofrequency current targeting the SP abolished the VT. The SP with the decremental property could represent the central pathway of this idiopathic RVOT reentrant VT.

Clinical Spectrum and Prognostic Factors of Pediatric Ventricular Tachycardia

There have been no studies on the clinical characteristics and prognostic factors of pediatric ventricular tachycardia (VT). Eighty-one patients with pediatric VT were studied retrospectively at a single center. The median follow-up period was 6.0 years (0.7-23.5 years). Patients were categorized into 6 groups: idiopathic VT (IVT, n=37), catecholaminergic polymorphic VT (CPVT, n=10), congenital heart disease-associated VT (n=15), myocarditis-associated VT (n=8), cardiomyopathy-associated VT (CMP-VT, n=5) and miscellaneous. The age distribution of VT had 2 peaks (infant and teenager). VT with left bundle branch block configuration was more frequently nonsustained than VT with right bundle branch block configuration (61% vs 8%). Although 22% were asymptomatic, 38% experienced syncope or seizure and 16% had cardiac arrest. The overall mortality rate was 7.4%. The expected life span without cardiac arrest was <4 years in the CMP-VT group and the 10-year survival rate in CPVT patients was approximately 55%. Onset at infancy, monomorphic type and transcatheter/surgical ablation were related to the successful resolution of VT. Logistic regression analysis revealed that CPVT, CMP-VT, polymorphic VT and sustained VT were significantly correlated with death or cardiac arrest. The clinical features and prognosis of pediatric VT differed with the VT type, clinical categories and onset age. Accurate diagnosis and proper treatment according to the clinical categories may improve the outcome.

Naxos disease presenting with ventricular tachycardia and troponin elevation

Naxos disease is a recessively inherited stereotype association of arrhythmogenic cardiomyopathy with a cutaneous phenotype, characterized by peculiar woolly hair and palmoplantar keratoderma. The cardiomyopathy clinically manifests by adolescence and the symptomatic presentation is usually with syncope and/or sustained ventricular tachycardia of left bundle branch block configuration. We report the case of a 43-year-old man without any history of heart disease who was admitted to the hospital because of an episode of sustained ventricular tachycardia and troponin I elevation, in the absence of coronary artery disease. Diagnostic workup, including genetic assessment, revealed Naxos disease as the underlying cause. In this case, acute myocarditis seems to be the most plausible explanation for the nonischemic myocardial injury.