Purkinje Potentials Research Articles

Non-Reentrant Fascicular Tachycardia: Clinical and Electrophysiological Characteristics of a Distinct Type of Idiopathic Ventricular Tachycardia.

The most common form of idiopathic Purkinje-related ventricular tachycardia (VT) is the reentrant type. We describe the clinical and electrophysiological characteristics of focal non-reentrant fascicular tachycardia. Among 530 idiopathic VT patients who were referred for ablation, we identified 15 (2.8%) with non-reentrant fascicular tachycardia (11 men, 45±21 years). Sinus rhythm ECG showed normal conduction intervals with a His-ventricular interval of 41±4 ms. All patients had monomorphic VT (cycle length: 337±88 ms) with a relatively narrow QRS (123±12 ms), and they did not respond to verapamil during the initial presentation. VT exhibited right bundle-branch block/superior axis configuration in 11 patients (73%) and inferior axis in 3 (20%). In 1 patient (7%), VT exhibited left bundle-branch block/superior axis configuration. During ablation, spontaneous VT occurred in 3 patients (20%) and nonentraintable VT or identical premature ventricular complex was induced in 9 (60%). A high-frequency presystolic Purkinje potential was recorded during VT/premature ventricular complex, preceding the QRS by 25±16 ms. VT recurrence was observed in 4 patients (27%), and among them, 3 underwent pacemap-guided ablation during the first session. A second ablation with activation mapping guidance eliminated the VT during the 88±8-month follow-up. Among idiopathic VT cases referred for ablation, 2.8% were focal non-reentrant fascicular tachycardia, which had distinct clinical characteristics and usually originated from the left posterior fascicle, and less commonly from the left anterior fascicle and right ventricular Purkinje network. Catheter ablation is effective, whereas pacemap-guided approach is less efficacious.

Catheter ablation of premature ventricular contractions arising from left anterior fascicle guided by an earliest presystolic Purkinje potential

Catheter ablation of premature ventricular contractions arising from left anterior fascicle guided by an earliest presystolic Purkinje potential

Circumferential ablation at the base of the left ventricular papillary muscles: A highly effective approach for ventricular arrhythmias originating from the papillary muscles

BackgroundRadiofrequency catheter ablation (RFCA) of ventricular arrhythmias (VAs) originating from the left ventricular (LV) papillary muscles (PMs) is challenging. MethodsWe enrolled 16 consecutive patients who received RFCA for VAs from LV PMs. Three-dimensional electroanatomical mapping was used to construct activation and/or pace maps. RFCA was performed first at the earliest activation site or at the best matched site in the pace maps. When an acceleration or reduction in the incidence of VAs was observed during the first few seconds of the application, the ablation energy was delivered continuously for 60–120s. Additional ablation was then circumferentially delivered at the base of the PMs. ResultsRFCA was successfully performed in all 16 patients with no cases of recurrence of VAs after a mean follow-up of 20±12months. VAs originated from the anterior (n=8) and posterior (n=8) PMs. Purkinje potentials were identified at the target sites in seven patients. All VAs were temporarily suppressed by one to two long-duration shots of RFCA at the initial targeted site, but recurrence was subsequently noted. In six patients, the QRS morphologies of the VAs changed after the initial RFCA. A subsequent circumferential approach with multiple ablations applied to the base of the PMs completely eliminated all VAs. In all but one patient, successful RFCA was achieved using an open-irrigated ablation catheter. ConclusionsCircumferential RFCA at the base of the PMs overcame anatomical limitations, leading to a high success rate of RFCA for VAs from LV PMs.

Novel Electrophysiology Signal Recording System Enables Specific Visualization ofthe Purkinje Network and OtherHigh-Frequency Signals.

High-frequency signals (e.g., Purkinje potentials) are of interest in arrhythmia syndromes such as fascicular tachycardia and ventricular fibrillation. However, restricted dynamic range and sampling rate in modern electrophysiology recording systems make it challenging to identify high-frequency,

A Reminder of Treatments Past

The Wolff-Parkinson-White (WPW) syndrome was initially described in 1930 as a clinical syndrome of paroxysmal tachycardias in healthy young people that demonstrated “bundle-branch block and short P-R interval”. These tachycardias were eventually determined to be macro-reentrant arrhythmias utilizing accessory pathways. Surgical approaches for transecting these accessory pathways were being developed as early as the 1960s. Since 1984, catheter ablation has developed into a safe and highly effective therapy option, and the treatment of choice for WPW syndrome today. We present a unique case of a patient with previous surgically treated WPW syndrome that serves as a reminder of treatments past and caution for current therapies. A 54-year-old man with a remote history of WPW syndrome, treated in 1989 with surgical cryoablation of a left ventricular free wall accessory pathway, now presented with an hour of sustained palpitations after a triathlon practice session. He was found to have ventricular tachycardia at a rate of 180 bpm on EKG requiring external cardioversion. The troponin I level peaked at 2.59 ng/mL. Left heart catheterization revealed a peculiar truncated 100% occlusion of the proximal circumflex artery with extensive bridging collaterals to the mid circumflex artery, and also confirmed an infero-basal aneurysm. The cause of the ventricular tachycardia (VT) was deemed non-ischemic and he was referred for electrophysiology study. 3D electroanatomic mapping of the left ventricular (LV) endocardial surface was performed, revealing a discrete posterior wall scar. Reentrant VT was repeatedly induced utilizing a zone of slow conduction along the border zone of the scar. Radiofrequency ablation of Purkinje potentials on the LV septum, running alongside the scar border zone, eliminated the VT. The entire endocardial surface of the postero-basal scar was electrically silenced to prevent further VT events. Typically, during the surgical approach of WPW, a wide endocardial (rarely an epicardial) incision was made along the atrial surface of the mitral valve annulus, dissecting deeply and caudally until ventricular myocardium was exposed. Despite the close proximity of the circumflex artery to the epicardial incision line during these surgeries, there are only rare reports of coronary artery complications, generally considered to be either catheter-induced dissections or embolic events. The development of a network of extensive bridging collaterals in our patient supports progressive stenosis of the left circumflex artery from cryoablation thermic injury, leading to scar formation and VT years later. In conclusion, this case reminds us that current ablative therapies are still relatively new, and long-term follow-ups for delayed complications remain a necessity. J Med Cases. 2016;7(6):216-219 doi: http://dx.doi.org/10.14740/jmc2488w

Where is the exact origin of narrow premature ventricular contractions manifesting qR in inferior wall leads?

BackgroundIn recent years, radiofrequency catheter ablation(RFCA) has been established as an effective therapy for idiopathic premature ventricular contractions (PVCs), however, its effect on the narrow PVCs (QRS duration < 130 msec) with qR pattern in inferior leads, may not been fully concluded.MethodsCharacteristics of 12-lead electrocardiogram (ECG) and electrophysiologic recordings were analyzed in 40 patients with symptomatic PVCs manifesting narrow QRS complex with qR pattern in inferior leads. The procedure of RFCA was performed based on pace mapping and activation mapping.ResultsAmong the 40 patients with narrow PVCs, complete elimination of PVCs was achieved by RFCA in 35 patients during a median follow-up period of 23 months. Successful ablation was achieved on 19 patients at the sites where earliest Purkinje potentials were recorded in left ventricular anterosuperior septum, thus PVCs arising from left anterior fascicle (LAF) were confirmed, for these PVCs, the QRS morphology were right bundle branch and left posterior fascicle block (RBBB + LPFB) with rightward axis, the average QRS duration 116.07 ± 7.96 ms, R or rsR’in lead V1,with transition zone ahead of lead V1 in precordial leads. Another 16 successful RFCA were achieved by energy delivery at interleaflet triangle(ILT) between right coronary cusp(RCC) and left coronary cusp(LCC) where no Purkinje potentials were recorded, for narrow PVCs arising from the L-RCC ILT, the QRS morphology were similar to the PVCs arising from LAF but much narrower in QRS duration (100.44 ± 3.49 vs. 116.07 ± 7.96 ms, p < 0.05), they were also R or Rs in lead V1 with the transition zone ahead of lead V1. For 5 symptomatic narrow PVCs failed to the procedure of RFCA, their electrocardiographic characteristics showed that the narrowest QRS duration (91.80 ± 6.94 vs. 100.44 ± 3.49, 116.07 ± 7.96 ms, p < 0.05), rs or rS (r/s or r/S≦1) morphology in lead V1 with the precordial transition zone behind lead V3.ConclusionsMost of idiopathic PVCs of narrow QRS duration (<130 msec) with qR pattern in inferior leads can be cured by the procedure of RFCA. On the basis of our study, we proposed that for narrow PVCs presenting qR pattern in inferior leads, when the ablation procedure failed at proximity of LAF within left anterosuperior septum, mapping and ablation in L-RCC ILT can be tried. The present findings can be helpful for planning catheter ablation for narrow PVCs manifesting qR in inferior leads.

A REMINDER OF TREATMENTS PAST

The Wolff-Parkinson-White (WPW) syndrome was initially described in 1930 as a clinical syndrome of paroxysmal tachycardias in healthy young people that demonstrated “bundle-branch block and short P-R interval”. These tachycardias were eventually determined to be macro-reentrant arrhythmias utilizing accessory pathways. Surgical approaches for transecting these accessory pathways were being developed as early as the 1960s. Since 1984, catheter ablation has developed into a safe and highly effective therapy option, and the treatment of choice for WPW syndrome today. We present a unique case of a patient with previous surgically treated WPW syndrome that serves as a reminder of treatments past and caution for current therapies. A 54-year-old man with a remote history of WPW syndrome, treated in 1989 with surgical cryoablation of a left ventricular free wall accessory pathway, now presented with an hour of sustained palpitations after a triathlon practice session. He was found to have ventricular tachycardia at a rate of 180 bpm on EKG requiring external cardioversion. The troponin I level peaked at 2.59 ng/mL. Left heart catheterization revealed a peculiar truncated 100% occlusion of the proximal circumflex artery with extensive bridging collaterals to the mid circumflex artery, and also confirmed an infero-basal aneurysm. The cause of the ventricular tachycardia (VT) was deemed non-ischemic and he was referred for electrophysiology study. 3D electroanatomic mapping of the left ventricular (LV) endocardial surface was performed, revealing a discrete posterior wall scar. Reentrant VT was repeatedly induced utilizing a zone of slow conduction along the border zone of the scar. Radiofrequency ablation of Purkinje potentials on the LV septum, running alongside the scar border zone, eliminated the VT. The entire endocardial surface of the postero-basal scar was electrically silenced to prevent further VT events. Typically, during the surgical approach of WPW, a wide endocardial (rarely an epicardial) incision was made along the atrial surface of the mitral valve annulus, dissecting deeply and caudally until ventricular myocardium was exposed. Despite the close proximity of the circumflex artery to the epicardial incision line during these surgeries, there are only rare reports of coronary artery complications, generally considered to be either catheter-induced dissections or embolic events. The development of a network of extensive bridging collaterals in our patient supports progressive stenosis of the left circumflex artery from cryoablation thermic injury, leading to scar formation and VT years later. In conclusion, this case reminds us that current ablative therapies are still relatively new, and long-term follow-ups for delayed complications remain a necessity. J Med Cases. 2016;7(6):216-219 doi: http://dx.doi.org/10.14740/jmc2488w

A new electrophysiologic observation in patients with idiopathic left ventricular tachycardia

In patients with idiopathic left ventricular tachycardia (ILVT), the arrhythmogenic substrate is poorly understood. The purpose of this study was to elucidate the ILVT characteristics and outcome of radiofrequency catheter ablation in patients with ILVT. Twenty-four patients with ILVT and 15 patients with left accessory pathways (control) underwent high-density mapping of the left His-Purkinje system during sinus rhythm (SR) using 3-dimensional electroanatomic mapping. Fragmented antegrade Purkinje potential (FAP) was represented at the left ventricular septum slightly inferoposterior to the left posterior fascicle (LPF) in 23 patients with ILVT. In control subjects, no FAPs could be recorded at the same region, FAPs were identified at the proximal portion of the LPF (4 patients) and at the distal LPF (1 patient). The finding of any FAPs in ILVT patients was significantly higher than that in control patients (23/24 vs 5/15, P < .01). Radiofrequency ablation at the area of FAP resulted in successful ablation in 23 patients with ILVT. No ILVT recurred during follow-up of 16.3 ± 7.2 months. In patients with ILVT, FAP located at the left ventricular septum slightly inferoposterior to the LPF is a novel finding using 3-dimensional electroanatomic mapping. The FAP may represent an arrhythmogenic substrate in ILVT and may be used for guiding successful ablation.

Incessant fascicular VT presenting as cardiogenic shock with multi-organ dysfunction syndrome

We report a rare clinical presentation of incessant idiopathic fascicular ventricular tachycardia (FVT), presenting as multi-organ dysfunction (MOD) syndrome with cardiogenic shock. Our patient was a 19-year-old male who presented with slowly progressive dyspnea from New York Heart Association (NYHA) II to NYHA IV at the time of presentation, palpitations, and dilated cardiomyopathy due to drug-refractory FVT. The patient was in cardiogenic shock with raised central venous pressures and required inotropic support for maintaining systolic blood pressure above 90mmHg. The MOD was seen in the form of deranged liver and kidney parameters. Echocardiography showed a dilated left ventricle (LV, 58mm at end-diastole, 52mm at end-systole) and decreased ejection fraction (20%). Electrocardiography showed a wide-QRS tachycardia (QRS 140ms, cycle length 440ms), with RsR’ in lead V1 and a QRS axis of −60°. After stabilization with ventilation, inotropic support, and cautious use of diuretics, an electrophysiologic study was performed. A Purkinje potential with early local ventricular activation was recorded from the LV inferoseptal region. The tachycardia was ablated at this site with radiofrequency (RF) energy (40W for 35sec). Over a 3-month follow-up, the patient remained asymptomatic and the LV size and function returned to normal.<Learning objective: To highlight a rare and unreported complication of fascicular ventricular tachycardia presenting as multi-organ dysfunction and its reversion with radiofrequency ablation.>

Fascicular Ventricular Tachycardia

Fascicular ventricular tachycardia (fascicular VT) is the most common idiopathic VT of the left ventricle. It presents with a right bundle branch block morphology and predominantly left axis deviation. Most of the available evidence supports the origin of fascicular VT as localized reentry circuits located close to the fascicle of the left bundle branch. During VT, the antegrade limb of the reentry circuit is the abnormal tissue in the left ventricular septum that is associated with slow and decremental conduction with verapamil sensitivity while the retrograde limb is usually the posterior fascicle forming the fast conduction zone. Catheter ablation is a highly effective therapy with long-term success rates of 90% and a low incidence of complications. Most of the fascicular VTs can be ablated during tachycardia by targeting the pre-Purkinje potential or Purkinje potential sites. Key words: Fascicular; Ventricular Tachycardia; Catheter Ablation; Verapamil

Catheter Ablation of Fascicular Ventricular Tachycardia: Long-Term Clinical Outcomes and Mechanisms of Recurrence.

Fascicular ventricular tachycardia (FVT) is a common form of sustained idiopathic left ventricular tachycardia with an Asian preponderance. This study aimed to prospectively investigate long-term clinical outcomes of patients undergoing ablation of FVT and identify predictors of arrhythmia recurrence. Consecutive patients undergoing FVT ablation at a single tertiary center were enrolled. Activation mapping was performed to identify the earliest presystolic Purkinje potential during FVT that was targeted by radiofrequency ablation. Follow-up with clinic visits, ECG, and Holter monitoring was performed at least every 6 months. A total of 120 consecutive patients (mean age, 29.3±12.7 years; 82% men; all patients with normal ejection fraction) were enrolled. FVT involved left posterior fascicle and left anterior fascicle in 118 and 2 subjects, respectively. VT was noninducible in 3 patients, and ablation was acutely successful in 117 patients. With a median follow-up of 55.7 months, VT of a similar ECG morphology recurred in 17 patients, and repeat procedure confirmed FVT recurrence involving the same fascicle. Shorter VT cycle length was the only significant predictor of FVT recurrence (P=0.03). Six other patients developed new-onset upper septal FVT that was successfully ablated. Ablation of FVT guided by activation mapping is associated with a single procedural success rate without the use of antiarrhythmic drugs of 80.3%. Arrhythmia recurrences after an initially successful ablation were caused by recurrent FVT involving the same fascicle in two thirds of patients or new onset of upper septal FVT in the remainder.

Cryoablation for Ventricular Arrhythmias Arising From the Papillary Muscles of the Left Ventricle Guided by Intracardiac Echocardiography and Image Integration

ObjectivesThis case series reports outcomes and complications of catheter cryoablation at the papillary muscles (PM) of the left ventricle (LV). BackgroundCatheter radiofrequency ablation is an effective treatment for ventricular arrhythmias (VAs) arising from the PM of the LV. The use of cryoablation at PMs has not been described. MethodsTen patients (70% men; median age: 38 years [range: 34 to 45 years]) with drug-refractory premature ventricular contractions or ventricular tachycardia underwent catheter cryoablation. VAs were localized using 3-dimensional (3D) mapping, multidetector computed tomography, and intracardiac echocardiography, with arrhythmia foci being mapped at either the anterolateral PM or posteromedial papillary muscle (PMPM) of the LV. Focal ablation, up to 240 s with freeze–thaw–freeze cycles was performed using an 8-mm cryoablation catheter via a transmitral approach. ResultsTermination of ventricular arrhythmia was observed in all 10 patients during ablation. Median follow-up was 6 months after ablation. The PMPM had higher prevalence of clinical arrhythmias (100% PMPM VAs vs. 10% anterolateral PM VAs). The PM base was the most frequent site of origin of the arrhythmias (60% of patients). Pace-mapping showed ≥11/12 match in all treated PM at the site of effective lesion. All VAs arising from the base of the PM showed Purkinje potentials. There were no post-procedure complications. VA recurred in 1 patient. ConclusionsCryoablation for arrhythmias arising from the PMs of the LV can be performed, and is a safe and effective alternative energy source for ablation.

Verapamil-Sensitive Upper Septal Idiopathic Left Ventricular Tachycardia: Prevalence, Mechanism, and Electrophysiological Characteristics

ObjectivesThis study sought to demonstrate the prevalence, mechanism, and electrocardiographic and electrophysiological characteristics of upper septal idiopathic left fascicular ventricular tachycardia (US-ILVT). BackgroundILVT is classified into left anterior and posterior types with no clear data about US-ILVT. MethodsAmong 193 ILVT patients, we identified 12 patients (6.2%; age 41 ± 22 years, 7 men) with US-ILVT. ResultsOf 12 patients with US-ILVT, 6 patients (50%) had previous history of radiofrequency catheter ablation for common ILVT. Sustained VT (cycle length: 349 ± 53 ms) was seen in all patients with a QRS interval slightly wider (104 ± 18 ms) than that during sinus rhythm (90 ± 19 ms). The VT exhibited an identical QRS configuration as sinus rhythm in 6 (50%) and incomplete right bundle branch block configuration in another 6. His-ventricular interval during VT was always shorter than that during sinus rhythm (27 ± 5 ms vs. 47 ± 10 ms). Purkinje potentials were activated in a reverse direction to that of common ILVT; namely, the diastolic potential (P1) was activated retrogradely but the pre-systolic potential (P2) was activated antegradely. At the left upper-middle ventricular septum, P1 potential was recorded during VT, preceding the QRS by 54 ± 20 ms. Radiofrequency catheter ablation at that site eliminated the VT with no recurrence during a 58 ± 35 months of follow-up. ConclusionsUS-ILVT is an identifiable VT that shares common criteria with ILVT and has a narrow QRS interval. Some US-ILVT cases appeared after common ILVT ablation. It is a reverse type of common ILVT (orthodromic form) with baseline morphological abnormalities that might provide a potential substrate for such VT.

Hemodynamic effects of Purkinje potential pacing in the left ventricular endocardium in patients with advanced heart failure

BackgroundVarious difficulties can occur in patients who undergo cardiac resynchronization therapy for drug-refractory heart failure with respect to placement of the left ventricular (LV) lead, because of anatomical features, pacing thresholds, twitching, or pacing lead anchoring, possibly requiring other pacing sites. The goal of this study was to determine whether Purkinje potential (PP) pacing could provide better hemodynamics in patients with left bundle branch block and heart failure than biventricular (BiV) pacing. MethodsEleven patients with New York Heart Association functional class II or III heart failure despite optimal medical therapy were selected for this study. All patients underwent left- and right-sided cardiac catheterization for measurement of LV functional parameters in the control state during BiV and PP pacing. ResultsMaximum dP/dt increased during BiV and PP pacing when compared with control measurements. This study compared parameters measured during BiV pacing with PP pacing and non-paced beats as the control state in each patient (717±171mmHg/s vs. 917±191mmHg/s, p<0.05; and 921±199mmHg/s, p<0.005); however, the difference between PP pacing and BiV pacing was not significant. There was no difference in heart rate, electrocardiographic wave complex duration, minimum dP/dt, left ventricular end-diastolic pressure, left ventricular end-systolic pressure, pulmonary capillary wedge pressure, or cardiac index when comparing BiV pacing and PP pacing to control measurements. ConclusionsThe hemodynamic outcome of PP pacing was comparable to that of BiV pacing in patients with advanced heart failure.

Mechanisms of Long-Duration Ventricular Fibrillation in Human Hearts and Experimental Validation in Canine Purkinje Fibers

ObjectivesThis study sought to determine the characteristics of human LDVF, particularly as it contrasts with short-duration VF (SDVF), and evaluate the role of Purkinje fibers in its maintenance. BackgroundThe electrophysiological mechanisms of long-duration ventricular fibrillation (LDVF) have not been studied in the human heart. MethodsVF was induced in 12 human Langendorff hearts, and the hearts were examined from initiation to LDVF (10 min). Endocardial, epicardial, and transmural plunge needle mapping were performed on the hearts. Simulated LDVF was studied in canine hearts to determine the potential role of Purkinje fiber automaticity. ResultsThe mean age at transplant was 48 ± 20 years, and the mean ejection fraction was <20%. The mean cycle length of local activation times on the endocardium was 252 ± 66 ms in SDVF and 441 ± 80 ms in LDVF (p = 0.0002). On the endocardium and the epicardium in LDVF, cycle length was 441 ± 80 ms and 590 ± 88 ms, respectively (p = 0.0002). No endocardial to epicardial activation frequency gradient was seen in SDVF. Simultaneous transmural needle activation was most common in SDVF, whereas endocardial to epicardial activation was most common in LDVF (47.7% and 38.8% of activations, respectively [p = 0.031]). Re-entry was less common in LDVF, and over time, wave break (i.e., nontransmural propagation of wave fronts) developed. Isochronal maps of the left ventricular endocardium in LDVF identified Purkinje potentials as preceding and predominating endocardial activations. In explanted canine heart preparations, rapid pacing led to spontaneous Purkinje fiber activity that was dependent on pacing rate and duration. ConclusionsLDVF in human hearts is characterized by focal endocardial activity with mid-myocardial wave break and not by re-entry. This arrhythmia is modulated by rapid activations in early VF that lead to spontaneous Purkinje fiber activity.

Electrophysiological and anatomical background of the fusion configuration of diastolic and presystolic Purkinje potentials in patients with verapamil-sensitive idiopathic left ventricular tachycardia

BackgroundIt is unclear whether false tendons (FTs) are a substantial part of the reentry circuit of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT). This study aimed to prove the association between FTs and the slow conduction zone by evaluating the electro-anatomical relationship between the so-called diastolic Purkinje (Pd) potentials and FTs using an electro-anatomical mapping (EAM) system (CARTO). MethodsThe 1st protocol evaluated the spatial distribution of Pd and presystolic Purkinje (Pp) potentials in 6 IVLT patients using a conventional CARTO system. In the remaining 2 patients (2nd protocol), the electro-anatomical relationship between the Pd–Pp fusion potential and the septal connection of the FT was evaluated using an EAM system incorporating an intra-cardiac echo (CARTO-Sound). ResultsPd potentials were observed in the posterior–posteroseptal region of the LV and had a slow conduction property, whereas Pp potentials were widely distributed in the interventricular (IV) septum. At the intersection of the 2 regions, which was located in the mid-posteroseptal area, both Pd and Pp potentials were closely spaced and often had a fused configuration. In the latter 2 patients (2nd protocol), it was confirmed that the intra-cardiac points at which the Pd–Pp fusion potential was recorded were located in the vicinity of the attachment site of the FT to the IV septum. In all patients, ILVTs were successfully eliminated by the application of radiofrequency at those points. ConclusionFTs may at least partly contribute to the formation of the Pd potential, and thus form a critical part of the reentry circuit of ILVT.

Trigger elimination of polymorphic ventricular tachycardia and ventricular fibrillation by catheter ablation: trigger and substrate modification.

Ventricular fibrillation (VF) is a malignant arrhythmia, usually initiated by a ventricular premature contraction (VPC) during the vulnerable period of cardiac repolarization. Ablation therapy for VF has been described and increasingly reported. Targets for VF triggers are VPCs preceded by Purkinje potentials or from the right ventricular outflow tract (RVOT) in structurally normal hearts, and VPC triggers preceded by Purkinje potentials in ischemic cardiomyopathy. During the session, mapping should be focused on the earliest activation and determining the earliest potential is the key to a successful ablation. However, suppression of VF can be achieved by not only the elimination of triggering VPCs, but also by substrate modification of possible reentry circuits in the Purkinje network, or between the PA and RVOT. The most important issue before the ablation session is the recording of the 12-lead ECG of the triggering event, which can prove invaluable in regionalizing the origin of the triggering VPC for more detailed mapping. In cases where the VPC is not spontaneous or inducible, ablation may be performed by pace mapping. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

Mapping and ablating ventricular premature contractions that trigger ventricular fibrillation: trigger elimination and substrate modification.

Ventricular fibrillation (VF) is a malignant arrhythmia, usually initiated by a ventricular premature contraction (VPC) during the vulnerable period of cardiac repolarization. Ablation therapy for VF has been described and increasingly reported. Targets for VF triggers are VPC preceded Purkinje potentials or the right ventricular outflow tract (RVOT) in structurally normal hearts, and VPC triggers preceded by Purkinje potentials in ischemic cardiomyopathy. The most important issue before the ablation session is the recording of the 12-lead electrocardiogram (ECG) of the triggering event, which can prove invaluable in regionalizing the origin of the triggering VPC for more detailed mapping. In cases where the VPC is not spontaneous or inducible, ablation may be performed by pacemapping. During the session, mapping should be focused on the earliest activation and determining the earliest potential is the key to a successful ablation. However, a modification of the Purkinje network might be applied when the earliest site cannot be determined or is located close to the His-bundle. Furthermore, the electrical isolation of the pulmonary artery (PA) can suppress RVOT type polymorphic ventricular tachycardia in some patients with rapid triggers from the PA. Suppression of VF can be achieved by not only the elimination of triggering VPCs, but also by substrate modification of possible reentry circuits in the Purkinje network, or between the PA and RVOT. Further studies are needed to evaluate the precise mechanisms of this arrhythmia.

Variations of electroanatomic substrates and markers of successful ablation in idiopathic left ventricular tachycardia: role of electroanatomic substrates and potential mechanism of tachycardia.

The variation of the substrates of verapamil-sensitive idiopathic left ventricular tachycardia (ILVT) was not understood. The purpose of this study was to investigate the variation of electroanatomic substrate [slow conduction zone (SCZ) and left ventricular conduction system (LVCS)] in ILVT and control individuals and markers of successful ablation. Electroanatomical mapping was performed during sinus rhythm in 20 ILVT patients and 26 control individuals with paroxysmal supraventricular tachycardia. LVCS and SCZ were tagged in geometry and the anatomic aspects were investigated. According to the distribution of Purkinje potential, LVCS was distinguished into three types: left bundle branch (LBB) was divided into two discrete fascicles without interconnections; divided into three separate fascicles; and fanlike structure distribution over septum broadly. The length of LBB and its fascicles in patients with ILVT were slightly longer than those of controls (P > 0.05). In the ILVT group, the SCZ was located at the inferoposterior septum in 17, inferior apical septum in one and two SCZs were located at the posterior and mid-septal in the other two patients, which were greater in size and longer in length than those of six controls (P < 0.05). At the crossover junction area with diastolic potential and Purkinje potential, with the size of 1.5 ± 0.4 cm(2), concealed entertainment and ablation were obtained successfully in all patients with ILVT. The anatomy of the LVCS and SCZ is highly variable in patients with ILVT, and the crossover junction area with diastolic potential and Purkinje potential might be a marker of ablation.

Reversible tachycardia mediated cardiomyopathy after radiofrequency ablation of idiopathic left ventricular tachycardia

A 20-year-old girl was admitted to our hospital with a chief complain of 12-days of palpitation and progressive shortness of breath. The symptoms of heart failure were consistent with New York Heart Association (NYHA) grade III. She had fever and cold symptoms 2-days before the onset of palpitation and heart failure symptoms but recovered soon, without other significant medical history. Physical examination demonstrates a heart rate of 170 beats per minute (bpm), a blood pressure of 70/40 mm Hg and bibasilar rales. ECG revealed a relatively narrow QRS tachycardia of 170 bpm with right bundle branch block (RBBB) morphology and a superior left axis configuration (Fig. 1a ). At the emergency department, empirical administration of intravenous verapamil was implemented and sinus rhythm was restored within 3 min with inverted T wave in leads II, III, aVF and V3–6 (Fig. 1b). A chest X-ray revealed bilateral plural effusion and increased cardiothoracic ratio (Fig. 2a ). Transthoracic echocardiography performed demonstrated marginal left ventricular dysfunction (left ventricular ejection fraction [LVEF] of 50%), with a normal LV end-diastolic diameter (LVEDD) of 38 mm and cardiac effusion with a fluid sonolucent area of 6 mm. Electrophysiological study performed in the following day after administration induced narrow QRS tachycardia which did not replicate the clinical morphology and indicated atrio-ventricular tachycardia via left atrio-ventricular bypass (Fig. 3a ), while the tachycardia of clinical morphology was not induced. The atrio-ventricular bypass was successfully ablated and the pre-systolic Purkinje potentials (Fig. 3b) were targeted, resulting in a new Q wave in inferior leads of ECG which mimics left posterior fascicular block after ablation (Fig. 1c). Chest X-ray performed in the 2nd day (Fig. 2b), the 3rd day (Fig. 2c) and the 40th day (Fig. 2d) revealed decreased and demission of plural effusion and decrease cardiothoracic ratio. Transthoracic echocardiography performed in the 3rd day demonstrated normalization of left ventricular dysfunction (LVEF of 76.6%) and cardiac effusion with a fluid sonolucent area of 6 mm, while in the 40th day the cardiac effusion was diminished. ECG in the 40th day revealed T wave restored upright (Fig. 1d). The patient remained free from arrhythmia for 2 months, without anti-arrhythmic medication.