Right Ventricular Tachycardia with Left Bundle Branch Block and Inferior Axis Morphology: Clinical and Arrhythmological Characteristics in 15 Patients

Fifteen patients (mean age 30) presenting with right ventricular tachycardia (VT) of the outflow tract type (left bundle branch block with inferior axis morphology), in the absence of obvious organic heart disease, were studied. Seven patients had palpitations, one presyncope and seven were asymptomatic. The echo and/or angiographic findings were normal in 11 patients (73%), suggesting arrhythmogenic right ventricular dysplasia (ARVD) in three (20%) and dubious in one (7%). The VT was sustained in three patients (20%), nonsustained (11 +/- 6 beats) in twelve (80%), inducible during exercise in two out of 15 patients (13%) and with ventricular stimulation in one out of eight (12.5%). Four patients were treated with sotalol, three with Class IC drugs and one with amiodarone. At follow-up of 36 +/- 30 months, only three patients had VT recurrences due to drug withdrawal. In conclusion: (1) abnormal echo and/or angiographic findings suggested that ARVD was observed in a minority of the patients (22%); (2) the low inducibility of VT and the good response to sotalol suggested a possible mechanism of abnormal automaticity; and (3) at a 3-year follow-up the prognosis appeared to be good in both patients with or without echo-angiographic signs suggestive of right ventricular dysplasia.     

Time-Domain Signal-Averaged Electrocardiogram in Nonischemic Ventricular Tachycardia

The prevalence of late ventricular potentials (LVPs) detected by signal averaged ECG (SAECG) is variable in nonischemic heart diseases. In idiopathic dilated cardiomyopathy, the prevalence increases from about 25% to 70%-90% in cases of spontaneous sustained ventricular tachycardia (VT), is not significantly correlated with hemodynamic and Holter data, and has a good positive predictive value for induced and spontaneous sustained VT. However, its predictive value for cardiac death has not been established. In primary hypertrophic cardiomyopathy, LVPs are rare (about 10%), not correlated to hemodynamic data, enhanced in cases of spontaneous sustained VT (up to 77%), and have a good predictive value of induced VT. LVP-SAECG are frequent in arrhythmogenic right ventricular dysplasia (ARVD) (70%-80%). They can identify patients with VT and an unapparent or limited form of this disease, or ARVD with few ventricular arrhythmias. The prevalence (26%-37%) of LVPs in mitral valve prolapse is clearly higher than in normal individuals or in other valvular diseases and is enhanced in cases of spontaneous and induced VT. Its significance remains speculative. After surgical repair of tetralogy of Fallot, LVPs can identify a group of patients with higher probability of induced and spontaneous risk of VT. The usefulness and significance of LVPs in other nonischemic cardiac diseases have not to date been established. In "true" idiopathic VT, without proved structural cardiac disease, the prevalence of LVPs does not exceed that observed in normal individuals (0%-5%), but in "apparent" idiopathic VT the prevalence of LVPs rises to 20%-40%. In these latter cases more invasive techniques must be used to discover a limited form of myocardiopathy.     

Activation of the Right Ventricular Apical Electrogram during Ventricular Tachycardia: Suitahility for Synchronizing Intracavitary Cardioversion

An intravascular catheter positioned in the right ventricular apex has been used for intracavitary cardioversion in patients with recurrent ventricular tachycardia. We examined the timing of the right ventricular apical electrogram during sinus rhythm and ventricular tachycardia (VT) in order to determine if this signal could be used to synchronize the delivery of a countershock. Sixty-three distinct morphologies of VT were observed in 33 patients undergoing electrophysiologic testing with programmed stimulation. Regardless of VT morphology or site of origin, the bipolar right ventricular electrogram always occurred within the peripheral QRS complex during ventricular tachycardia. Relative timing occurred within the QRS ranging from the initial 13% of the QRS to the last 12%. When all episodes of VT were examined, the timing of the right ventricular electrogram did not correlate linearly with the peak of the ECG, but the right ventricular electrogram occurred within 60 ms of the peak ECG in 83% of episodes of ventricular tachycardia. In one case of arrhythmogenic right ventricular dysplasia, the right ventricular electrogram occurred 160 ms after the peak ECG in ventricular tachycardia, a time when delivery of a countershock may have precipitated ventricular fibrillation. Six of these patients underwent cardioversion utilizing an intracavitary catheter and external generator. Acceleration of VT, or conversion to ventricular fibrillation, occurred following two of 27 shocks (7.4%). The right ventricular electrogram occurred the latest within the QRS complex in the two patients who developed acceleration of the tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Repetitive Ventricular Responses Induced by Radiofrequency Ablation for Idiopathic Ventricular Tachycardia Originating from the Outflow Tract of the Right Ventricle

In 23 consecutive patients, radiofrequency (RF) ablation was used as treatment for idiopathic ventricular tachycardia (VT) originating from the outflow tract of the right ventricle. In this study, we focused on the repetitive ventricular response (> 5 consecutive QRS beats during RF application). The incidence and clinical implications of the repetitive ventricular response were examined through the results of endocardial mapping and RF ablation. VT origin was mapped as the earliest activation site during VT, and it was determined within 0.5 × 0.5 cm (narrow site) in 13 patients and wider than 0.5 × 0.5 cm (wide origin) in the other 10 patients. The repetitive ventricular response was induced during application of RF current in 14 of 23 patients (61%), and it was more frequently observed in VT from a wide origin (100%) than in the VT from a narrow site (31%). The QRS morphology of the repetitive ventricular response was identical to that of clinical VT. As RF application was continued and/or repeated, the RR interval of the repetitive ventricular response was gradually prolonged, the number of consecutive QRS complexes was decreased, and clinical VT was finally eliminated. The overall success rate of RF ablation was 96% (22/23 patients), and no complications were observed. In conclusion, a repetitive ventricular response was frequently observed in idiopathic right VT. The changing pattern of repetitive ventricular response, slowing, and/or disappearing was consistent with successful RF ablation.     

Early Afterdepolarizations in a Patient with Idiopathic Monomorphic Right Ventricular Tachycardia

To identify the role of afterdepolarizations in the induction of idiopathic monomorphic right ventricular tachycardia (VT), monophasic action potentials (MAPs) were recorded in a patient with this type of VT. The VT had a left bundle branch block configuration and inferior axis, and originated in the right ventricular outflow tract (RVOT). MAPs were recorded with a contact electrode at the origin of the VT, as well as other ventricular sites. The VT was induced by the intravenous administration of isoproterenol and/or rapid ventricular pacing and was preceded by short-long-short sequences of RR intervals. Early afterdepolarizations (EADs) in MAPs were recorded at the origin of VT (RVOT), but not recorded at other ventricular sites. These data suggest that catecholamine sensitive triggered activity seems to be the mechanism of idiopathic monomorphic right VT and EADs can be recorded in association with the occurrence of this type of VT.     

Demonstration of Entrainment and Presence of Slow Conduction During Ventricular Tachycardia in Arrhythmogenic Right Ventricular Dysplasia

During VT in two cases with arrhythmogenic right ventricular dysplasia, entrainment criteria, constant fusion beats except for the last entrainment beat, progressive fusion, and a localized conduction block associated with interruption of VT, were demon strated with rapid ventricular pacing performed during VT. Furthermore, a long conduction interval was present during entrainment from the pacing site to the earliest activation site during VT. indicating the presence of a slow conduction area. VT in these cases was, thus, due to reentry with an area of slow conduction within the circuit.     

Two Cases of Ventricular Parasystole Associated with Ventricular Tachycardia

In two patients, ventricular pamsystole (VP) was associated with ventricular tachycardia (VT), and in one patient, catheter ablation was successful. In patient 1, with dilated cardiomyopathy, VP led to VT, which converted to ventricular fibrillation. In patient 2, VP led to symptomatic nonsustained polymorphic VT. The origin of parasystolic focus was determined byendocardial mapping, and a radiofrequency current was delivered to patient 2. Both VP and VT disappeared immediately, and no recurrence has been observed during a follow-up of 8 months. Catheter ablation to the parasystolic focus was effective and a relationship between VP and VT was strongly suggested.     

Successful Radiofrequency Current Catheter Ablation of Sustained Ventricular Tachycardia

We performed radiofrequency current catheter ablation in two patients with nonischemic sustained ventricular tachycardia (VT). In one patient, two morphologically distinct VTs were induced by electrical stimulation. One showed right bundle branch block pattern and the other left bundle branch block pattern. The earliest site of activation during each VT was determined at the septum of the right ventricle. However, these two sites were close to the His-bundle elecfrogram recording area. In the other patient, a VT with a left bundle branch block pattern occurred spontaneously after the administration of isoproterenol. The earliest site of activation during VT was determined at the outflow tract of the right ventricle. During tachycardia, radiofrequency current ablation (40 W ± 30 sec) was delivered to the earliest site of activation, A few seconds after fulguration, each VT was terminated and additional radio-frequency currents were given near these sites. After the ablation, VT could not be induced by the electrical stimulations, nor did it recur. No side effects were observed and the atrioventricular conduction remained intact. We feel that nonischemic VTs could possibly be treated by using radiofrequency current catheter ablation.     

Amiodarone in the Management of Patients with Ventricular Tachycardia and Ventricular Fibrillation

Fifty-eight patients with symptomatic ventricular tachycardia (VT) or ventricular fibrillation (VF) were treated with amiodarone. All had clinical episodes of VT/VF or inducible VT during electropharmacologic testing despite treatment with maximumtolerated doses of conventional antiarrhythmic agents. Chronic treatment with amiodarone was begun at a dose of 800–1000 mg per day. Thirty-two patients were also treated with a previously ineffective conventional agent. Thirty patients underwent programmed ventricular stimulation after 2.6 ± 1.7 months (mean ± S. D.) of treatment with amiodarone at a mean daily dose of 588 ± 155 mg. VT was induced in 25 patients (sustained in 20, nonsustained in five). Seventeen patients had a recurrence of VT or VF after 0.5–9 months of treatment with amiodarone (fatal in seven, non-fatal in 10). Forty-one patients (71%) had no recurrence of symptomatic VT or VF while being treated with amiodarone (mean follow-up period, 17.1 ± 12.4 months). Among the 25 patients who had inducible VT with programmed ventricular stimulation while being treated with amiodarone, 19 patients (76%) have had no recurrence of symptomatic VT or VF overa follow-up period of 21.5 ± 7.3 months. Ambulatory electrocardiographic recordings obtained after one week of treatment with amiodarone were not helpful in predicting clinical response. Twenty-two patients (38%) developed ataxia and/or an intention tremor which improved with a decrease in the amiodarone dose. Amiodarone, either by itself or in combination with conventional antiarrhythmic drugs, has a significant therapeutic effect in high risk patients with refractory VT. The finding of inducible VT during electropharmacologic testing in patients taking amiodarone does not preclude a favorable clinical response. Neurologic toxicity is common in patients treated with 600–800 mg per day of amiodarone.     

Atrial Epicardial Pacing with Long Stimulus to P Wave Interval in a Patient with Arrhythmogenic Right Ventricular Dysplasia Complicated by Right Atrial Thrombosis

Atrial epicardial pacing with a long stimulus to P wave interval in a patient with arrhythmogenic right ventricular dysplasia complicated by right atrial thrombosis is discussed. Arrhythmogenic right ventricular dysplasia (ARVD) is associated with a high incidence of malignant ventricular arrhythmias. Most patients with ARVD need antiarrhythmic drugs, catheter ablation, or an implantable cardioverter defibrillator. We report a patient with ARVD in whom effective treatment with sotalol caused severe, symptomatic sinus bradycardia requiring permanent pacing. Due to leftward displacement of the right ventricle and the presence of two thrombi in the right atrium, an epicardial atrial lead and AAI pacemaker were implanted. A long stimulus to P wave interval caused by severe dilatation of the right atrium was recorded. During a 6 months of follow-up on sotalol treatment there were neither ventricular tachycardia (VT) attacks nor pacing problems.     

Fusion with the Prolonged First Postpacing Interval in Pacing of Ventricular Tachycardia

In cases of recurrent sustained ventricular tachycardia (VT), constant fusion and progressive fusion in fhe surface electrogram were observed during overdrive pacing of VT. However, following cessation of pacing, the return cycle of VT (stimulus to the first nonpaced QRS) was longer than the VT cycle length. This phenomenon can be explained by orthodromic capture of the exit site of the VT current with a conduction time (stimulus to QRS) exceeding the VT cyde length. This site can therefore be activated during entrainment of VT during the mid-to-terminal portion of the paced QRS complex, resulting in constant fusion.     

Recurrent Ventricular Tachycardia Responsive to Verapamil

We describe five young patients with recurrent ventricular tachycardia in the absence of organic heart disease. In all patients tachycardia could be terminated or prevented with verapamil. Tachycardia in four patients was very similar, with a QRS pattern of right bundle branch block and left axis deviation. Electrophysiology studies in two patients showed that VT was inducible in one patient (rapid atrial or ventricular pacing, ventricular extrastimuli) but not in the other. The clinical and electrocardiographic similarities in these patients suggest that their ventricular tachycardias may share a common pathophysiology and may be dependent on slow channel activity.     

Entrainment of Ventricular Tachycardia by Sinus Rhythm

Entrainment of ventricular tachycardia (VT) may be manifest as fixed and progressive QRS fusion with ventricular and, rarely, atrial pacing. Only a single example of spontaneous VT entrainment by another rhythm, rapid atrioventricular nodal tachycardia, has been reported. This article describes an example of fixed and progressive QRS fusion between conducted sinus rhythm and VT consistent with entrainment. In contrast to entrainment with pacing, entrainment of VT by sinus rhythm occurred with drug-mediated arrhythmia slowing and demonstrated progressive QRS fusion at a constant cycle length. However, it did not demonstrate unfused but entrained QRS complexes. The resulting short PR interval and wide QRS mimicked a preexcited rhythm.     

Differentiation Between Monomorphic Ventricular Tachycardia and Sinus Tachycardia Based on the Right Ventricular Evoked Potential

The differentiation between ventricular tachycardia (VT) and smus tachycardia (ST) is problematic in some patients with implantable defibrillators and/ or antitachycardia pacemakers. The Integral of the ventricular endocardial evoked response, or paced depolarization integral (PDI), has been demonstrated to undergo characteristic changes with a variety of stimuli including catecholamines, pacing rate, and exercise. We hypothesized that the PDI recorded from a unipolar transvenous right ventricular endocardial catheter would differentiate VT from ST. The PDI was calculated from a unipolar pacing stimulus, delivered via a cathode in the right ventricular apex, and the reference electrode, a quadripolar catheter positioned in the superior vena cava. PDIs were measured in 22 patients during VT and sinus rhythm. The PDI measured during sinus rhythm was 579 ± 240 μV-sec and the PDI during VT was 894 ± 411 μV-sec (P < 0.001). In a subset of seven patients, PDIs were measured during VT, sinus rhythm, and ST induced by catecholamine infusion or exercise. In this subset, the PDI during sinus rhythm was 645 ± 295 μV-sec, during ST 588 ± 308 μV-sec (9% decrease from sinus, P = 0.05), and during VT 863 ± 342 μV-sec (33.9% increase, P = 0.01). These data indicate that the measurement of the PDI is potentially useful in differentiating VT from ST.     

Nonclinical Ventricular Tachycardia in the WolflF-Parkinson-White Syndrome

Between September 1980 and June 1984 we assessed the specificity of induction of ventricular tachycardia (VT) with one or two ventricular extrastimuli in a consecutive series of 148 patients undergoing electrophysiological assessment for the Wolff-Parkinson-White (WPW) syndrome by standard electrophysiological techniques. Fifteen patients (10%) had six or more beats of VT induced by one ventricular extrastimulus after a ventricular drive (9 patients), two ventricular extrastimuli during reciprocating tachycardia (6 patients), and during a single atrial extrastimulus (1 patient). None of the six men and nine women, aged 16-61 years, had apparent heart disease. VT lasted for 20 +/- 14 (mean +/- standard deviation) cycles with a cycle length of 235 ms +/- 27 and was generally polymorphic. One patient had ventricular fibrillation. These patients were compared to 15 age- and sex-matched patients studied in the same time period. There was no difference in anterograde effective refractory period of the accessory pathway (316 +/- 92 vs 319 +/- 68 ms), ventricular effective refractory period (218 +/- 12 vs 227 +/- 23), shortest pacing cycle length maintaining 1:1 anterograde conduction over the accessory pathway (306 +/- 132 vs 320 +/- 67) or minimum R-R interval between preexcited beats during atrial fibrillation (280 +/- 68 vs 294 +/- 105). All patients are alive and well over a follow-up interval of 20 +/- 11 months on no antiarrhythmic therapy (13 patients) or on propranolol (2 patients).(ABSTRACT TRUNCATED AT 250 WORDS)     

Chest Thump and Ventricular Tachycardia

Chest thump is a simple method of treatment of some paraxysmal arrhythmias. Its therapeutic efficacy, electrophysiological bases and clinical utility have been studied in 17 patients during 45 episodes of ventricular tachycardia (VT). Thumping the precordium interrupted the VT in 22 episodes. Three types of interruption of VT have been observed: (1) In 15 episodes, single ventricular premature beats induced by the blow, occurring randomly in the cycle, stopped the arrhythmia; (2) In 5 episodes, a run of premature beats, induced by a rapid succession of blows, interrupted the tachycardia; (3) In 2 episodes, chest thump caused a short period of asystole followed by sinus rhythm. Chest thump is an antiarrhythmic treatment of definite clinical utility. The complications are rare, although there is a possibility of ventricular fibrillation. Therefore, it should be performed only under careful supervision.     

Ventricular Fibrillation Triggered during and after Radiofrequency Energy Delivery to the Site of Origin of Idiopathic Right Ventricular Outflow Tract Arrhythmia

We observed a case of idiopathic ventricular arrhythmias originating from the right ventricular outflow tract (RVOT). The origin of target premature ventricular contraction (PVC) and nonsustained ventricular tachycardia (VT) was within a wide low‐voltage area around the RVOT. During radiofrequency (RF) application to the site of arrhythmia origin, polymorphic VT and ventricular fibrillation were repeatedly triggered by new PVC that had developed near the site of ablation. This electrical storm persisted >30 minutes after cessation of RF current delivery, and was suppressed by additional RF applications to the site of origin of the new PVC.     

A Prospective Evaluation of Single and Dual Current Pathways for Transvenous Cardioversion in Rapid Ventricular Tachycardia

By using a prospective randomized study design, we compared the clinical efficacy and safety of single unidirectional and bidirectional transvenous cardioversion shocks for termination of rapid ventricular tachycardia (VT) having cycle lengths less than 300 ms. A Medtronic 6880 catheter was placed in the right ventricular apex and an R2 skin patch electrode was placed over the left scapula. Patients were randomized into two groups. Group A patients received unidirectional transvenous shocks using the two catheter electrodes (right ventricular apical cathode and superior vena caval anode) which resulted in a single current pathway. Group B patients received bidirectional transvenous shocks using a common cathode (right ventricular apex) and two separate anodes (superior vena caval and R2 patch) resulting in two current pathways. Identical shocks with total energies of 2.7, 5.0 and 10.0 J and waveform tilt of 27% were delivered to Groups A and B. In selected Group B patients, delivered shock currents through the right ventricular apex/superior vena caval and right ventricular apex/R2 patch electrode pairs were measured. We analyzed the initial episode of VT with a cycle length less than 300 ms in 33 patients with organic heart disease (mean age, 64 +/- 9 years; mean VT cycle length, 248 +/- 37 ms) who underwent programmed electrical stimulation. Transvenous cardioversion shocks terminated 31% of 16 VT episodes in Group A and 41% of 17 VT episodes in Group B (p greater than .2). The mean successful shock energy was 6.1 +/- 3.7 J in Group A and 3.0 +/- 0.9 J in Group B (p less than .05). Forty percent of all successfully cardioverted episodes in Group A and 86% of all successfully cardioverted VT episodes in Group B were terminated at an energy of 2.7 J (p = .09). Analysis of shock waveforms in Group B revealed 47 to 74% of the total current was transmitted through the right ventricular apex/superior vena caval electrodes and 26 to 53% through the right ventricular apex/R2 electrodes. We conclude that single bidirectional transvenous shocks are effective for rapid VT termination in selected patients. Dual current pathways decrease energies needed for successful transvenous cardioversion in this patient population.     

Entrainment of Ventricular Tachycardia in Postoperative Tetralogy of Fallot

The mechanism of ventricular tachycardia (VT) in postoperative tetralogy of Fallot has been ascribed to both reentry and triggered automaticity. We performed electrophysiologic studies on a patient with this condition and induced sustained uniform ventricular tachycardia by programmed extrastimulation. Pacing during the tachycardia at multiple cycle lengths from the right ventricular apex (RVA) and outflow tract (RVOT) produced constant but progressive fusion between the paced and tachycardia QRS. With termination of pacing, the last captured complex was unfused but coupled at the paced cycle length and then the tachycardia resumed at its intrinsic rate. Therefore, the VT was entrained. In addition, an area of slow conduction between the RVOT and RVA was demonstrated. These findings support a reentrant mechanism of this arrhythmia.     

Alternation of QRS Morphology and Effect of Radiofrequency Ablation in Idiopathic Ventricular Tachycardia

We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them.Results: VT was induced by programmed stimulation in all patients and the mean cycle length was 363 ± 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20–40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 ± 5.2 months.Conclusion: RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exits may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.