“I Dread the Heart Surgery but it Keeps My Child Alive”—Experiences of Parents of Children with Right Ventricular Outflow Tract Anomalies during the Assessment for Cardiac Reoperation

Background:Parents of children with complex right ventricular outflow tract(RVOT)anomalies are confronted with their child’s need for heart surgery early in life and repeated reoperations later on.Preoperative assessment needs to be performed whenever an indication for reoperation is suspected.The aim was to illuminate the experiences of parents of children diagnosed with RVOT anomalies,in particular,how they experience their child’s heart disease and everyday life during the assessment and after the decision on whether to perform a reoperation.Method:Individual interviews(n=27)were conducted with nine parents on three occasions between 2014 and 2016 and analyzed using reflexive thematic analysis.Results:The analysis resulted in the following five main coexisting themes:The heart surgery keeps my child alive illuminates parents’experiences during and after the assessment and emphasizes that heart surgery,although dreaded,is central for their child’s survival;Everyday struggles illuminates the different struggles parents had to face to ensure that their child would be in the best possible condition;the remaining three themes,Unconditional love,Trust in life,and Togetherness,illuminate the ways in which the parents gained inner strength and confidence in their everyday lives.Conclusion:Although the parents were grateful for the assessment and had learned to navigate among the fears it aroused,they experienced several distressing situations during the assessment process that should be addressed.By inviting both the parents and their child to participate in the child’s care,individualized support can take into account the needs of both parents and child.

Electrophysiological changes of autonomic cells in left ventricular outflow tract in guinea pigs with iron deficiency anemia complicated with chronic heart failure

Objective: To investigate the electrophysiological changes of autonomic cells in left ventricular outflow tract in guinea pigs with iron deficiency anemia complicated with chronic heart failure.Methods: Guinea pigs model of iron deficiency anemia complicated with chronic heart failure in 10 guinea pigs of the experimental group was made by feeding a low iron diet,pure water and subcutaneous injection of isoproterenol. The control group consisting of 11 guinea pigs was given normal food, normal water and injected with normal saline. The left ventricular outflow tract model specimen was also prepared. The standard microelectrode technique was used to observe electrophysiological changes of autonomic cells in the outflow tract of left ventricular heart failure complicated with iron deficiency anemia in guinea pig model. The indicators of observation were maximal diastolic potential, action potential amplitude, 0 phase maximal depolarization velocity, 4 phase automatic depolarization velocity, repolarization 50% and 90%, and spontaneous discharge frequency.Results: Compared with the control group, 4 phase automatic depolarization velocity,spontaneous discharge frequency and 0 phase maximal depolarization velocity decreased significantly(P < 0.01) and action potential amplitude reduced(P < 0.01) in model group. Moreover, repolarization 50% and 90% increased(P < 0.01).Conclusions: There are electrophysiological abnormalities of the left ventricular outflow tract in guinea pigs with iron deficiency anemia complicated with heart failure.

Effect of iron overload on electrophysiology of slow reaction autorhythmic cells of left ventricular outflow tract in guinea pigs

Objective: To investigate the electrophysiology effects and mechanism of iron overload on the slow response autorhythmic cells in the left ventricular outflow tract of guinea pigs.Methods: Standard microelectrode cell recording techniques were adopted to observe the electrophysiological effects of different concentrations of Fe^(2+)(100 μmol/L, 200 μmol/L) on the left ventricular outflow tract autorhythmic cells.Heart tissues were perfused with FeSO_4(200 μmol/L) combing with CaCl_2(4.2 mmol/L), Verapamil,(1 μmol/L), and nickel chloride(200μmol/L) respectively to observe the influences of these contents on electrophysiology of FeSO_4(200μmol/L) on the left ventricular outflow tract autorhythmic cells.Results: Fe^(2+)at both 100 μmol/L and 200 μmol/L could change the electrophysiological parameters of the slow response autorhythmic cells of the left ventricular outflow tract in a concentrationdependent manner resulting into decrease in Vmax, APA and MDP, slower RPF and VDD, and prolonged APD_(50) and APD_(90)(P all <0.05).Besides, perfusion of increased Ca^(2+) concentration could partially offset the electrophysiological effects of Fe^(2+)(200 μmol/L).The L-type calcium channel(LTCC) blocker Verapamil(1 μmol/L) could block the electrophysiological effects of Fe^(2+)(200 μmol/L).But the T-type calcium channel(TTCC) blocker nickel chloride(NiCl_2, 200 μmol/L) could not block the electrophysiological effects of Fe^(2+)(200 μmol/L).Conclusions: Fe^(2+) can directly change the electrophysiological characteristics of the slow response autorhythmic cells of the left ventricular outflow tract probably through the L-type calcium channel.

Right Ventricular Outflow Tract Septal Pacing versus Apical Pacing: A Prospective, Randomized, Single-blind 5-Years Follow-up Study of Ventricular Lead Performance and Safety

Summary： Lead placement for ventricular pacing variably impacts the physiological benefit of the pa- tient. This study evaluated the ventricular lead performance and safety of right ventricular outflow tract septal pacing in patients with bradyarrhythmia in South China over 60-month follow-up. Totally, 192 patients （108 males, and 84 females, 63-4-21 years old） with bradyarrhythmia were randomly divided into two groups. The right ventricular outflow tract septum （RVOTs） group had lead placement near the sep- tum （n=97）, while the right ventricular apex （RVA） group had a traditional apical placement （n=95）. RV septal lead positioning was achieved with a specialized stylet and confirmed using fluoroscopic projec- tion. All patients were followed up for 60 months. Follow-up assessment included stimulation threshold, R-wave sensing, lead impedance and lead complications. The time of electrode implantation in both the ROVTs and RVA groups were significantly different （4.29±0.61 vs. 2.16±0.22 min; P=0.009）. No dif- ferences were identified in threshold, impedance or R-wave sensing between the two groups at 1 st, 12th, 36th and 60th month during the follow-up period. No occurrence of electrode displacement, increased pacing threshold or inadequate sensing was found. The long-term active fixation ventricular electrode performance in RVOTs group was similar to that in RVA group. RVOTs pacing near the septum using active fixation electrodes may provide stability during long-term follow-up period.

Implantation of Lumenless Pacing Leads at the Inter-atrial Septum and Right Ventricular Outflow Tract with Deflectable Catheter-sheath

Current permanent right ventricular and right atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asynchronous electrical activation pattern, which results in asynchronous ventricular contraction and relaxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class Ⅰ indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French （Fr） lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath （Medtronic Inc., USA） were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results （mean atrial pacing threshold： 0.87 V; mean P wave amplitude： 2.28 mV; mean ventricular pacing threshold： 0.53V; mean R wave amplitude： 8.75 mV） were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.

Long-term follow-up of right ventricular outflow tract septal pacing

Objective Right ventricular outflow tract septum has become widely used us an electrode placement site. However, data concerning lead performances and complications for lead repositioning with this technique were scant. The purpose of this study was to observe long- term lead performances and complications of right ventricular outflow tract septal pacing and provide evidences for choosing an optimal electrode implantation site. Methods Thirty-six patients with septal active electrode implantation and 39 with apical passive electrode implantation were enrolled in this study. Pacing threshold, R-wave sensing, lead impedance, pacing QRS width and pacing-related compli- cations for two groups at implantation and follow-up were compared. Results There were higher pacing threshold and shorter pacing QRS width at implantation in the septal group compared with the apical group. There were no differences between the septal and the apical groups in pacing threshold, R-wave sensitivity, lead impedance and pace-related complication during a follow-up. Conclusions Right ventricular outflow tract septum could be used as a first choice for implantation site because it had long-term stable lead performances and no serious complications compared with the traditional apical site.

Coronary Artery Complications after Right Ventricular Outflow Tract Reconstruction Surgery

Background:Mechanisms and clinical manifestations of coronary artery complications after right ventricular outflow tract reconstruction surgery are not well known.Methods:Patients who had coronary artery complications after pulmonary valve replacement or the Rastelli procedure at a single tertiary centre were retrospectively analysed.Results:Coronary artery complications were identified in 20 patients who underwent right ventricular outflow tract reconstruction surgery.The median age at diagnosis of coronary artery complication was 21 years(interquartile range:13–25 years).Mechanisms of coronary artery complications were compression by adjacent materials in 12 patients,dynamic compression of intramural course of coronary artery in two patients,and intraoperative injury in six patients.Congenital coronary artery anomalies were identified in 50%(10/20)of patients.Four patients presented with early postoperative haemodynamic instability.Fourteen patients showed late onset symptoms or signs of coronary insufficiency,including chest pain,ventricular dysfunction,or ventricular arrhythmias.Coronary artery stenosis was incidentally found on cardiac computed tomography angiography in two asymptomatic patients.Four patients underwent surgical interventions,and one patient underwent percutaneous coronary intervention for coronary stenosis.One patient with recurrent ventricular tachycardia required an implantable cardioverter-defibrillator.There were two deaths in patients with intraoperative coronary injury.Conclusion:Preoperative coronary evaluation and long-term follow-up for the development of coronary artery complications are required in patients undergoing right ventricular outflow tract reconstruction surgery to prevent ventricular dysfunction,arrhythmias,and death,especially among those with congenital coronary anomalies.

Right Ventricular Myxoma Causing Right Ventricular Outflow Tract Obstruction: A Case Report

A 63-year-old patient presented with dyspnea and chest distress. A computerized tomography and echocardiogram showed a cardiac mass in the right ventricle, which caused obstruction of the right ventricular outflow tract. Coronary angiography revealed a dense meshwork of the abnomorly capillary vessels originating from right coronary artery. The mass was completely excised under cardiopulmonary bypass. The mass attached right ventricle lateral wall and posterior triscupid leaflet. Histology was typical myomatous tissue.

Polytetrafluoroethylene Patch versus Autologous Pericardial Patch for Right Ventricular Outflow Tract Reconstruction in Patients with Tetralogy of Fallot

Objective: For patients of TOF with pulmonary annular hypoplasia, reconstruction of right ventricular outflow tract (RVOT) often requires a trans annular patch (TAP). The present study aims to compare the outcomes of TOF repair using Polytetrafluoroethylene (PTFE) patch versus autologous glutaraldehyde fixed pericardial patch for RVOT reconstruction. Materials and methods: 103 consecutive patients undergoing TOF repair in whom TAP was required were randomized into two groups: Group I (pericardial patch), Group II (PTFE patch). Postoperative outcomes in terms of postoperative heart rhythm, duration of mechanical ventilation, mediastinal and pleural drainage, length of stay in intensive care unit (ICU) and hospital mortality were assessed. A separate team of cardiologists independently evaluated pre- and post-operative gradients across the RVOT, degree of pulmonary insufficiency, right ventricular systolic function. Results: There were no significant differences between the two groups in terms of the incidence of postoperative arrhythmias, duration of mechanical ventilation, length of intensive care unit or hospital stay. The requirement of inotropes was no different in the PTFE patch group as compared with the pericardial patch group (16.84 ± 7.04 vs. 17.90 ± 6.71, median 19 vs. 20, p = 0.825). The re-exploration rate was higher in the PTFE group as compared with the pericardial patch group (6 vs. 1). Postoperative Echocar-diography revealed no differences in the RV systolic function between the two groups before discharge. Conclusion: In patients undergoing TOF repair, using a PTFE patch yields comparable results. However, the efficacy of PTFE will only be established once;mid-term and long-term results are available.

Evaluation of global and regional left ventricular systolic function in patients with frequent isolated premature ventricular complexes from the right ventricular outflow tract

Background Frequent premature ventricular complexes from the right ventricular outflow tract （RVOT-PVCs） are associated with left ventricular dysfunction.This study adopted two-dimensional speckle tracking imaging to evaluate global and regional left ventricular myocardial function in patients with frequent RVOT-PVCs.Methods This study included 30 patients with frequent RVOT-PVCs and 30 healthy subjects.Aortic systolic velocity-time integral （AoVTI） and myocardium strain in circumferential （CS）,radial （RS） and longitudinal （LS） directions were evaluated by conventional echocardiography and speckle tracking imaging.All values of patients with RVOT-PVCs were recorded during sinus （PVC-S） and PVC beats （PVC-V）.Results Significant differences were demonstrated in global CS,RS and LS between the control subjects and the PVC-V （CS：（17.46±2.48）% vs.（11.52±3.28）%,RS：（48.26±10.20）% vs.（20.92±9.78）%,LS：（19.89±2.62）% vs.（11.79±3.66）%,P 〈0.01）,and in segmental RS and LS of nearly all the left ventricular segments.Statistical differences in segmental CS between the PVC-V and the control subjects were only observed in anterior,anteroseptal and septal segments （only seen in anteroseptal and septal segments at apex）.Furthermore,V/S AoVTI （AoVTI during the PVC beat divided by AoVTI during the sinus beat,then multiplied by 100%） correlated with coupling interval （r=0.67,P 〈0.001） and global strain （CS：r=0.48,P=0.007; RS：r=0.65,P 〈0.001; LS：r=0.65,P 〈0.001）.Conclusions Frequent RVOT-PVCs can induce global and regional left ventricular systolic dysfunction.The reduction of hemodynamic parameters relates to the coupling interval and the global systolic function.

L-type calcium current in right ventricular outflow tract myocytes of rabbit heart

The mechanism of idiopathic ventricular tachycardia originating from the right ventricular outflow tract （RVOT） is not clear. Many clinical reports have suggested a mechanism of triggered activity. However, there are few studies investigating this be- cause of the technical difficulties associated with examining this theory. The L-type calcium current （/Ca-L）, an important in- ward current of the action potential （AP）, plays an important role in arrhythmogenesis. The aim of this study was to explore differences in the APs of right ventricular （RV） and RVOT cardiomyocytes, and differences in electrophysiological character- istics of the ICa-L in these myocytes. Rabbit RVOT and RV myocytes were isolated and their AP and Ic,-L were investigated us- ing the patch-clamp technique. RVOT cardiomyocytes had a wider range of AP duration （APD） than RV cardiomyocytes, with some markedly prolonged APDs and markedly shortened APDs. The markedly shortened APDs in RVOT myocytes were abolished by treatment with 4-AP, an inhibitor of the transient outward potassium current, but the markedly prolonged APDs remained, with some myocytes with a long AP plateau not repolarizing to resting potential. In addition, early afterdepolariza- tion （EAD） and second plateau responses were seen in RVOT myocytes but not in RV myocytes. RVOT myocytes had a high- er current density for/Ca-L than RV myocytes （RVOT （13.16±0.87） pA pF-1, RV （8.59±1.97） pA pF-1; P〈0.05）. The ICa-L and the prolonged APD were reduced, and the EAD and second plateau response disappeared, after treatment with nifedipine （10 μmol L^-1）, which blocks the Ica-L. In conclusion, there was a wider range of APDs in RVOT myocytes than in RV myocytes, which is one of the basic factors involved in arrhythmogenesis. The higher current density for ICa-L is one of the factors causing prolongation of the APD in RVOT myocytes. The combination of EAD with prolonged APD may be one of the mechanisms of RVOT-VT generation.

Left ventricular endocardial pacing predicts the reduction of left ventricular outflow tract pressure gradient immediately after percutaneous transseptal myocardial ablation in patients with hypertrophic obstructive cardiomyopathy refractory to medicatio

Background Hypertrophic obstructive cardiomyopathy （HOCM） carries an increased risk for sudden cardiac death. No data regarding the percutaneous transseptal myocardial ablation （PTSMA） and epicardial left ventricular pacing （LVP） were reported. Methods Seven patients with recurrent symptoms and increased resting left ventricular outflow tract pressure gradient （LVOTG） after PTSMA and another 14 patients with HOCM without history of PTSMA were studied. Both resting and dobutamine stress echocardiography, PTSMA and LVP were routinely performed. Results In patients without previous PTSMA procedure, mild reduction of resting LVOTG was detected at 5 minutes after left ventricular pacing, and this reduction became significant at 10 minutes. All patients were divided into successful and unsuccessful groups according to their response to LVP. In contrary to patients in unsuccessful group, resting and R-S2 stimuli-induced LVOTG during PTSMA procedure were decreased dramatically （（9±5） mmHg vs （58±12） mmHg, （12±2） mmHg vs （113±27） mmHg, P〈0.001）. Analysis of Logistic regression demonstrated that only LVOTG level dudng left ventdcular pacing was an independent factor predicting the reduction of LVOTG immediately after PTSMA （odds ratio （OR）, 0.59; 95% CI 2.67 to 5.82; P=0.0002）. Conclusion Left ventricular endocardial temporary pacing plays a critical role in predicting acute effect on the reduction of LVOTG immediately after PTSMA procedure.

Handmade tri-leaflet ePTFE conduits versus homografts for right ventricular outflow tract reconstruction

Background This study aimed to investigate the performance of handmade tri-leaflet expanded polytetrafluoroethylene(ePTFE)conduits in the absence of a suitable homograft.Methods Patients who underwent right ventricular outflow tract reconstruction with tri-leaflet ePTFE conduits or homografts between December 2016 and August 2020 were included.The primary endpoint was the incidence of moderate or severe conduit stenosis(>36 mmHg)and/or moderate or severe insufficiency.The secondary endpoint was the incidence of severe conduit stenosis(>64 mmHg)and/or severe insufficiency.Results There were 102 patients in the ePTFE group and 52 patients in the homograft group.The median age was younger[34.5(interquartile range:20.8-62.8)vs.60.0(interquartile range:39.3-81.0)months,P=0.001]and the median weight was lower[13.5(10.0-19.0)vs.17.8(13.6-25.8)kg,P=0.003]in the ePTFE group.The conduit size was smaller(17.9±2.2 vs.20.5±3.0 mm,P<0.001)and the conduit Z score was lower(1.48±1.04 vs.1.83±1.05,P—0.048)in the ePTFE group.There was no significant difference in the primary endpoints(log rank,T3=0.33)and secondary endpoints(log rank,P=0.35).Multivariate analysis identified lower weight at surgery[P=0.01;hazard ratio:0.75;95%confidence interval(CI)0.59-0.94]and homograft conduit use(P=0.04;hazard ratio:8.43;95%CI 1.14—62.29)to be risk factors for moderate or severe conduit insufficiency.No risk factors were found for moderate or severe conduit stenosis or conduit dysfunction on multivariate analysis.Conclusion Handmade tri-leaflet ePTFE conduits showed acceptable early and midterm outcomes in the absence of a suitable homograft,but a longer follow-up is needed.

Giant blood cyst tumor in the left ventricular outflow tract

Blood cyst is a rare primary cardiac tumor usually affecting the cardiac valves. Associated with severe occlusion-related complications, it is generally removed surgically. With a brief review of the literature, we present a case of pedunculated tumor in the left ventricular outflow tract identified by echocardiography.

The Pregnancy Heart Team Approach for the Adult with Hypertrophic Cardiomyopathy and Severe Left Ventricular Outflow Tract Obstruction

Hypertrophic cardiomyopathy (HCM), the most common single-gene cardiovascular disease, is associated with increased risk for arrhythmias, heart failure, and sudden cardiac death. The hemodynamic changes known to occur during pregnancy can exacerbate heart failure and arrhythmias in women with HCM. We present a 30-year-old woman with HCM to illustrate the benefits of multidisciplinary team management of severe left ventricular outflow tract obstruction (peak gradient >100 mmHg) for optimal maternal and fetal outcomes.

Aortic Sinus of Valsalva Aneurysm Isolation by Radiofrequency Ablation in Outflow Tract Ventricular Tachycardia

Idiopathic monomorphic ventricular tachycardia and premature ventricular complexes (PVCs) commonly arise from the right and left ventricular outflow tracts (VOT). Their mechanism is most commonly triggered activity from delayed after-depolarizations and successful ablation is performed at the site of earliest endocardial activation. Re-entrant mechanisms have been rarely described. We report a case of an otherwise healthy patient who ultimately underwent six electro-physiology studies (EPS) and suffered numerous implantable cardiac defibrillator (ICD) discharges prior to the successful radiofrequency ablation (RFA) of two idiopathic VOT tachycardias. During the sixth EPS, a proximal aortogram demonstrated a left aortic sinus of valsalva (LASV) aneurysm. Subsequntly, a novel and successful RFA strategy of aneurysm isolation was undertaken. The presence of multiple clinical or inducible VT morphologies and the characterization of a VT as re-entrant should raise concerns that a complex arrhythmogenic substrate is present and defining the anatomy with angiography or an alternative imaging modality is essential in achieving a successful ablation strategy.

Ⅰ导联R/(R+S)对胸前V3导联移行流出道室性心律失常起源部位的鉴别价值

目的:探索鉴别胸前V3导联移行流出道室性心律失常(OT-VA)起源部位的体表心电图指标。方法:连续选择2017年1月至2022年8月行导管射频消融术的胸前V3导联移行OT-VA患者65例。比较左室流出道起源组(LVOT组)和右室流出道起源组(RVOT组)室性心律失常发作时体表心电图QRS波振幅及相关指标的差异,选择差异有统计学意义的指标,绘制ROC曲线评价所选取指标鉴别OT-VA起源部位的效能。结果:LVOT组11例,RVOT组54例,两组间差异有统计学意义且ROC曲线下面积(AUC)最大的指标为Ⅰ导联R波/(R+S)波振幅比[R/(R+S)],其鉴别OT-VA起源部位的AUC(95%CI)为0.949(0.894~1.000),截断值为0.50。Ⅰ导联R/(R+S)<0.50诊断胸前V3导联移行LVOT起源OT-VA的敏感度、特异度和准确度分别为0.909、0.944和0.938。结论:Ⅰ导联R/(R+S)<0.50可准确鉴别LVOT起源的胸前V3导联移行OT-VA。

激动标测和起搏标测联合指引下解剖消融治疗特发性右室流出道室性早搏的效果

目的探讨激动标测和起搏标测联合指引下解剖消融治疗特发性右室流出道(RVOT)室性早搏的临床价值。方法回顾性分析2023年1—10月在郑州大学第一附属医院心血管内科和许昌市中心医院心血管内科住院接受室性早搏射频消融术的36例患者的资料,经电生理检查证实室性早搏来源于RVOT,根据术中室性早搏数量多少灵活采用激动标测和或起搏标测找到靶点进行对应肺动脉根部瓣下和瓣上联合消融,分析该方法即刻及3个月成功率。结果术中室性早搏数量少的患者也可以快速有效地进行导管消融术并取得满意的远期效果。结论激动标测和起搏标测联合指引下解剖消融治疗特发性RVOT室性早搏临床可行,效果较好。

室间隔射频消融及心室起搏术治疗左室流出道动态梗阻的效果对比

目的 探讨室间隔射频消融及心室起搏术治疗左室流出道动态梗阻(LVOTO)的效果。方法 选取2017年6月—2023年1月成都大学附属医院心血管内科收治的90例LVOTO患者,按照随机数字表法分为观察组和对照组,每组45例。观察组采取室间隔射频消融治疗,对照组采取心室起搏术治疗,对比两组术后1年的疗效。结果 观察组手术前后左心室舒张末期内径、左心室射血分数、左心室质量指数、静息左心室流出道压差(LVOTPG)、负荷LVOTPG水平的差值均高于对照组(P <0.05)。观察组手术前后N末端B型钠尿肽前体(NTproBNP)、肌钙蛋白Ⅰ(cTnⅠ)的差值均高于对照组(P <0.05)。两组室间隔中间段厚度、室间隔基底段厚度、左心室后壁厚度比较,差异均无统计学意义(P>0.05)。两组总并发症发生率比较,差异无统计学意义(P>0.05)。结论LVOTO患者采取心室起搏术、室间隔射频消融术均能改善心功能和cTnI和NT-proBNP水平,且并发症发生率较低,值得临床推广。

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.