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.     

Localized reentry. Mechanism of induced sustained ventricular tachycardia in canine model of recent myocardial infarction.

This study was undertaken to investigate the mechanism underlying sustained monomorphic ventricular tachycardia (VT) in late experimental canine myocardial infarction. The hypothesis that sustained and "organized" continuous electrical activity (CEA) displaying a reproducible pattern with recurrent components recorded by bipolar endocardial, intramural, or epicardial electrodes in 10 animals during electrically induced sustained monomorphic VT represented reentrant excitation in an anatomically small area of the ventricle, was evaluated in the light of the following observations: Organized CEA always preceded the first monomorphic ventricular complex (QRS) of VT as well as the discrete local electrograms from closely surrounding sites during the initiation of VT. The site of organized CEA corresponded to the site of origin of sustained VT determined by iso-chronous contour map analysis of activation sequence. Ventricular pacing at rates more rapid than that of VT failed to terminate VT despite ventricular capture unless it transformed CEA into discrete local electrograms. VT could be terminated in three animals, with a single, critically timed premature stimulus delivered at a critically located focus close to the site of CEA, which would result in local capture and interrupted CEA. In six animals, surgical ablation of the site of organized CEA effectively prevented the reinitiation of sustained VT by programmed cardiac stimulation. These data showed that organized CEA and sustained VT were closely associated phenomena and suggested that organized CEA probably represented an important component of the tachycardia circuit.     

Catheter Ablation of Ventricular Tachycardia in Patients with Right Ventricular Dysplasia: Identification of Target Sites by Entrainment Mapping Techniques

Objective: To identify target sites for radiofrequency ablation of ventricular tachycardia (VT) by entrainment mapping techniques in patients with arrhythmogenic right ventricular dysplasia. Methods: Entrainment mapping and radiofrequency ablation of eight VTs was performed in seven patients. Radiofrequency ablation was applied at 31 reentry circuits sites that were classified based on findings during entrainment. Results: By entrainment criteria the 31 sites were classified as: exit sites (n = 12), proximal sites (n = 6), and outer loop sites (n = 13). Radiofrequency current application terminated VT at 7 of 31 sites: 2 of 12 exit sites (17%), 4 of 6 proximal sites (67%), and 1 of 13 outer loop sites (8%). Conclusion: Radiofrequency ablation terminated VTs most often at sites proximal to the exit as opposed to outer loop sites and exit sites (P = 0.05). The critical isthmus for ablation of VT in right ventricular dysplasia often may be distant to the exit.     

Adenosine and Verapamil-Sensitive Ventricular Tachycardia Originating From the Left Ventricle: Radiofrequency Catheter Ablation

A ventricular tachycardia (VT) with right bundle branch block (RBBB) QRS morphology and left axis originating from the inferoapical segment of the left ventricle is described in a 49-year-old man without structural heart disease. This VT could be initiated during isoproterenol infusion and was terminated with intravenous administration of adenosine and verapamil. Radiofrequency ablation eliminated the tachycardia. Previous reports have suggested reentry as the mechanism for a verapamil-sensitive VT with this ECG morphology, while cAMP-mediated triggered activity has been proposed as a mechanism for VTs sensitive to adenosine. The latter more typically arise in the right ventricular outflow tract. The electrophysiological and electropharmacological characteristics of the tachycardia in this patient suggest that this VT morphology is not specific for a mechanism but rather for the location of the site of origin.     

The Relationship between Pacing Site and Induction or Termination of Sustained Monomorphic Ventricular Tachycardia by Antitachycardia Pacing

Background: With the development of left ventricular pacing for cardiac resynchronization, there is an interest in the possibility of improving ventricular antitachycardia pacing (ATP) efficacy by pacing from the LV electrode(s).
Objective: This study assessed the efficacy of pacing delivered from the left coronary vein (LCV) compared to that delivered from the right ventricular apex (RVA) upon ventricular tachycardia (VT) induction and termination.
Methods: Sixty patients undergoing provocative ventricular electrophysiology (EP) studies in three centers were enrolled. Multipolar EP catheters were placed in the atrium, the RVA, and LCV. VT induction was attempted from the RVA and LCV in random order. Upon detection of monomorphic VT, burst ATP for up to 10 pulses at 88% VT cycle length was delivered from the RVA or LCV, in a random order, and crossed over when possible. Identical VT morphologies were reinduced to allow paired comparison of RVA versus LCV ATP.
Results: Data from 55 patients were analyzed. Thirty-four morphologically distinct monomorphic VT types were induced in 22 patients. ATP succeeded in 18 (55%) and VTs in 13 patients. RVA ATP terminated 15 of 23 (65%) VTs, and LCV ATP terminated 10 of 23 (43%) VTs (P = 0.14). ATP delivered ipsilateral to the earliest activation site required 5.0 ± 2.6 pulses to terminate compared to 4.8 ± 1.7 pulses when delivered from the contralateral site (P = 0.90). Paired comparison was possible for 13 VT morphologies in 11 patients. Paired RVA and LCV ATP efficacy was identical (54 % vs 54%, P = 1.0).
Conclusion: ATP delivered from a LCV lead offers no efficacy advantage over pacing from the RVA. (PACE 2010; 27–32)     

Basal Exit Site of Clinical Ventricular Tachycardia is an Independent Predictor of Antitachycardia Pacing Failure in Implantable Cardioverter‐Defibrillators Recipients

Background: Little is known about predictors of antitachycardia pacing (ATP) failure in implantable cardioverter defibrillator (ICD) recipients. Distance between the stimulation site and the ventricular tachycardia (VT) site of origin may critically affect ATP effectiveness. We hypothesized that ATP may be less effective in ICD patients who had basal VT than in those who had apical VT. Methods: We reviewed data from 52 patients with sustained monomorphic VT and left ventricular disease referred for ICD implantation. ATP was delivered exclusively at the right ventricular apex. The clinical VTs site of origin (basal, midventricular, or apical) was determined in each patient, using 12‐lead electrocardiogram. VTs episodes treated with ATP during the 1‐year follow‐up were studied. ATP success rate (%), defined as the ratio between the number of successful ATP sequences and the number of delivered ATP sequences, was determined in each patient. Results: VT exit site was apical in 19 patients (36%), basal in 18 patients (35%), and midventricular in 15 patients (29%). In those 52 patients, 1,393 ATP sequences, delivered to treat 761 VT episodes, were analyzed. ATP success rate was found to be associated with the VT site of origin (median [interquartile range]): basal (33%[11–67]), midventricular (50%[37–100]), apical (100%[41–100]) (P = 0.027). Multivariate analysis identified basal VT site of origin as an independent predictor of ATP failure (P = 0.023). Conclusion: ATP is less effective in ICD patients who had basal VT than in those who had apical VT before ICD implantation. (PACE 2012; 35:1209–1216)     

Successful Radiofrequency Catheter Ablation for Macroreentrant Ventricular Tachycardias in a Patient with Tetralogy of Fallot After Corrective Surgery

CHINUSHI, M., et al .: Successful Radiofrequency Catheter Ablation for Macroreentrant Ventricular Tachycardias in a Patient with Tetralogy of Fallot After Corrective Surgery . Radiofrequency (RF) catheter ablation was applied to two macroreentrant ventricular tachycardias (VTs) documented after corrective operation for tetralogy of Fallot. The activation wavefront of VT with a right bundle branch block pattern was found to revolve in a clockwise manner around a presumed myotomy scar in the right ventricle, and VT with a left bundle branch block pattern revolved around the same anatomical obstacle in a counterclockwise manner. In both VTs, the biggest conduction delay was confirmed at the right ventricular outflow tract. RF applications to the slow conduction area terminated each VT within a few seconds but were insufficient to cure the VTs. RF lesions were then applied to the, slow conduction area in a line to intersect the macroreentrant circuit, and both VTs became noninducible.     

Adenosine- and verapamil-sensitive ventricular tachycardia in the newborn

Two neonates presented with sustained, monomorphic VT. Transesophageal electrophysiological studies demonstrated that the VTs were initiated with burst atrial pacing in one and noninducible in the other, and both terminated with burst atrial pacing and with adenosine. Oral verapamil suppressed the VTs in both. Following discontinuation of verapamil at 1 year of age, both children remain free of tachycardia recurrence at 3 and 4 years of age. These cases suggest that cAMP-mediated triggered activity may be responsible for some VTs in infancy.     

Antitachycardia pacing for rapid VT during ICD charging: a method to prevent ICD shocks

In patients with ICDs, rapid VTs are usually treated with shocks. It is unknown, if antitachycardia pacing (ATP) delivered once for rapid VT during capacitor charging can avoid painful shocks without increasing the risk of syncope. In patients in whom rapid monomorphic VT (cycle length 300-220 ms) could be reproducibly induced during predischarge ICD testing, the success of cardioversion (defibrillation threshold plus 10 J) and a single ATP attempt (burst with 8 or 16 stimuli) was compared using a randomized crossover study design. Consciousness of the patients was checked by the signal from a button constantly pushed by the patient. In 20 patients (ejection fraction 0.50 +/- 0.19) rapid VTs (253 +/- 26 ms) were reproducibly induced. A single burst successfully terminated 11 (55%) of 20 rapid VTs, 6 episodes could not be terminated with a single burst pacing and 3 VTs accelerated. Rapid VTs not terminated by ATP were significantly faster than those that could be terminated (246 vs 258 ms, P = 0.026). Cardioversion (19 +/- 3 J) terminated the VTs in all cases. No patient suffered syncope during rapid VTs. A single ATP may terminate rapid VT with cycle lengths < 300 ms in 55% of patients without increasing the risk of syncope. Therefore, in rapid VTs one attempt of ATP may be suitable as an additional therapy option during ICD capacitor charging to avoid painful shocks without compromise of safety. Thus, future ICDs should implement the option of ATP during charging of capacitors.     

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.     

Comparison of Fixed Burst Versus Decremental Burst Pacing for Termination of Ventricular Tachycardia

The objective of this study was to compare prospectively the efficacy of fixed burst pacing with that of decremental hurst pacing in terminating VT. Forty-four patients with inducible sustained monomorphic VT were studied. The efficacy of fixed burst and decremental burst pacing in terminating 57 distinct types of VT were compared during 50 eiectrophysiology tests fmean VT cycle length = 334 ± 84 msec. Termination of each type of VT was attempted with fixed burst and decremental burst pacing, Both pacing algorithms were delivered in an adaptive fashion with an increasing number of stimuli with each successive attempt at VT termination. Seventy percent of VT episodes were successfully terminated with fixed burst pacing, The mean number of stimuli required for VT termination was 5 ± 2. Seventy-two percent of VT episodes were successfully terminated with decremental burst pacing. The mean number of stimuJi required for VT termination ivas 5 ± 2. For fixed burst and decremental burst pacing, the efficacy of VT termination was greater for VTs with a cycle length > 300 msec than for faster VTs (P < 0.05). The efficacy of VT termination and the incidence of VT acceleration were no different for the two pacing algorithms (P > 0.1). The results of this study demonstrate that fixed burst and decrementai burst pacing are equally effective in terminating VT and that a single adaptive pacing algorithm is effective in terminating nearly three fourths of VTs.     

Entrainment of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Tachycardia

In two patients with arrhythrnogenic right ventricular dysplasia (ARVDJ, sustained ventricular tachycardia (VT) was induced by programmed stimulations during serial drug testings. One patient had five and the other had two VT morphologies, and the sites of origin were determined by endocardial catheter mappings. When overdrive pacing was performed, constant fusion in the QflS complex was observed in the two patients. Constant fusion of a different degree was also observed at different paced cycle lengths. Both patients had dilated right ventricles and wall-motion abnormality, and the diagnosis of ARVD was further confirmed by the specimen resected at the site of origin of VT. Therefore, VT in ARVD can be entrained and reentry is the most likely mechanism of such VT.     

Suppression of Storms of Ventricular Tachycardia by Epicardial Ablation of Isolated Delayed Potential in Noncompaction Cardiomyopathy

A 65‐year‐old recipient of an implantable cardioverter defibrillator suffering from ventricular noncompaction developed storms of ventricular tachycardia (VT). Epicardial voltage mapping revealed the presence of a large low‐voltage area in the left ventricular apical and inferoposterior wall, and isolated delayed potential was recorded over 1.5 cm in the posterior border between low and normal myocardial voltage. Pacemapping at the delayed potential recording site produced two different QRS depending on pacing output strength, and these two QRS morphologies were similar to clinically documented VTs. During one of the VTs, a mid‐diastolic potential was recorded from the site with the delayed potential, and rapid pacing produced concealed entrainment. After epicardial radiofrequency ablation of the isolated delayed potential, VTs were noninducible and the VT storm was suppressed.     

The Clinical Use of External Noninvasive Pacing in the Termination of Sustained Ventricular Tachycardia

In order to evaluate the potential use of external cardiac pacing (EXP) in the clinical termination of sustained ventricular tachycardia (VT), we attempted VT terminations in seven patients. All had recurrent sustained monomorphic ventricular tachycardia (mean rate 145 beats/min), which had previously required cardioversion. During subsequent VT episodes, all seven underwent overdrive pacing with EXP at a pulse amplitude of 120 mA, and rates of 200 pulses/min. A total of 18 of 18 episodes of VT were successfully terminated by EXP alone. In one patient, the first attempt at EXP termination of one episode of VT resulted in an acceleration of the tachycardia, which was then terminated by EXP. All patients tolerated EXP well with minimal sedation. We conclude that EXP may be an effective clinical modality for the termination of sustained monomorphic ventricular tachycardia.     

Atrial Sensing to Augment Ventricular Tachycardia Detection by the Automatic Implantable Cardioverter Defibrillator: A Utility Study

The triggering of automatic implantable cardioverter defibrillator (AICD) discharges by supraventricular tachycardias, despite the presence of a probability density function algorithm, remains a limitation of an otherwise highly effective device. We systematically investigated the diagnostic utility which theroretically could derive form the addition of atrial sensing capability to the AICD in 25 patients with 30 inducible sustained monomorphic ventricular tachycardias (VTs) at clinically relevant rates (greater than or equal to 150 beats/min). Patients were included only if they were not taking medication capable of depressing ventriculoatrial (VA) conduction for at least 5 half-lives prior to electrophysiological testing. We tested the simple criterion for VT that ventricular cycle length (CL) be shorter than the atrial CL (not met in sinus or most other supraventricular tachycardias). Mean VT CL was 283 +/- 47 ms (range 210 to 370). In 25 (83%) VTs, the VT criterion was consistently satisfied. Of the five cases in which the criterion was not met, 1:1 VA conduction during VT was present in four, three of which initially manifested 2:1 VA conduction lasting from 14 to 28 s and therefore would have transiently fulfilled the VT criterion. The remaining patient who failed to satisfy the VT criterion had ongoing atrial flutter during a relatively slower sustained VT, but this circumstance could be recognized because of the varying AV interval. The absence of 1:1 VA conduction at CLS less than or equal to 400 ms during ventricular pacing accurately predicted the absence of 1:1 VA conduction during VT in 95% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Initiation of Ventricular Tachycardia by Interruption of Pacemaker-Mediated Tachycardia in a Patient with a Dual-Chamber Implantable Cardioverter Defibrillator

A 74-year-old man with a dual-chamber implantable cardioverter defibrillator implanted 3 years before experienced multiple ventricular tachycardias (VTs). All episodes were initiated by pacemaker-mediated tachycardia (PMT) that was either stopped by atrial undersensing or the tachycardia termination algorithm of the device. After the termination of PMT, two rapid ventricular paced beats, the first initiated by artificial triggering and the second due to retrograde conduction of the first one, initiated VT that was successfully terminated by antitachycardia pacing or a direct current shock of the device . All episodes revealed this pattern of initiation with a short-long-short ventricular sequence inducing VT.     

Ventricular tachycardia--etiology, mechanisms and therapy

Prevention and therapy of cardiovascular diseases have undergone enormous changes over the last decades. However, ventricular tachycardias (VT) still pose a major problem in a number of cardiac patients. Analysis of the etiology and mechanism of the tachycardia is of paramount importance for initiation of specific therapies. The morphology of VTs on the surface ECG can be either polymorphic or monomorphic. Polymorphic VTs have a constantly changing QRS-morphology due to the variable ventricular activation, without specific origin. This kind of VT is mainly caused by an acute, often reversible condition, such as ischemia or QT-prolongation. These VTs are potentially malignant, they cannot be treated by catheter ablation. In contrast, monomorphic VTs have a constant QRS-morphology, indicative of repetitive ventricular depolarisation in the same activation sequence. This kind of VT is either caused by focal abnormal activity (triggered activity, automaticity, micro-reentry) or by an arrhythmogenic substrate (macro-reentry). Focal idiopathic VTs usually have a benign prognosis and catheter ablation is potentially curative. The majority of ventricular arrhythmias, however, are substrate-related reentry tachycardias, most commonly based on an infarct scar Therapy of first choice for these patients is the treatment with an implantable Cardioverter/Defibrillator (ICD). Catheter ablation is indicated in case of drug refractory recurrent VTs triggering repeated ICD therapies. The different therapeutic strategies are not alternative but complementary options in many patients.     

Conductive Properties of the Reentrant Pathway of Ventricular Tachycardia During Entrainment From Outside and Within the Zone of Slow Conduction

Ventricular tachycardia (VT) was entrained with rapid ventricular pacing outside and within the zone of slow conduction (SCZ), and the conductive properties of the reentrant pathway were compared between the two pacing sites. Underlying heart diseases were old myocardial infarction (n = 2), postoperative tetralogy of Fallot (n = 1) or double outlet of the right ventricle (n = 1), dilated cardiomyopathy (n = 1), and pulmonary regurgitation of unknown cause (n = 1). Rapid pacing was continued for 5–10 seconds, and the time interval from paced stimulus to the entrained electrogram at the exit from SCZ (St-Ex) or to the QRS complex (St-QRS) was measured. Rapid pacing was performed at three or more cycle lengths after a decrement in steps of 10 msec. During rapid pacing outside of SCZ and entrainment of VT, constant fusion and progressive fusion were observed, and St-Ex and St-QRS showed the same response pattern: either a frequency dependent prolongation in 4 of 7 VTs or a constant time interval in the others VTs. When rapid pacing was attempted within SCZ, the response of the time intervals from paced site to the QRS (St-QRS) was the same as those observed during pacing outside SCZ except for one VT. In VT with repaired tetralogy of Fallot, the frequency dependent prolongation was observed during pacing from outside of SCZ but not within SCZ. Diseased myocardium extending widely into the outflow tract of the right ventricle may be responsible for the frequency dependent prolongation of St-Ex. In conclusion, the conductive property of the reentrant pathway might be assessed by observing the response patterns of St-Ex or St-QRS interval during transient entrainment of VT outside of SCZ, but exceptions may exist.     

Localization of precise origin of idiopathic ventricular tachycardia from the right ventricular outflow tract by a 12-lead ECG: a study of pace mapping using a multielectrode "basket" catheter

Radiofrequency catheter ablation guided by pace-mapping techniques has proven effective in eliminating idiopathic ventricular tachycardia (VT) originating from the right ventricular outflow tract (RVOT). A method for rapidly identifying the origin of VT from 12-lead electrocardiogram (ECG) findings would be helpful for the catheter ablation procedure. The purpose of this study is to precisely localize the origin of idiopathic VT from the RVOT by a 12-lead ECG from a study of multipoint pace mapping. In one patient with premature ventricular complex (PVC) and 3 with VT, a "basket" catheter was deployed in the RVOT for bipolar pacing from 56 sites in the endocardium of RVOT. Under fluoroscopy the pacing sites were classified into the septum and free wall. We investigated the QRS morphology in leads, I, II, and III; the depth of the QS wave in leads aVR and aVL; and the height of the initial r wave in leads V1 and V2. Pacing was captured in 30-47 of 56 sites (54%-84%). As the pacing sites changed from the anterior to posterior of the septum, the QS notch (-) type in lead I shifted through rs to R, while a shift from R type to rR' or Rr' was noted in leads II and III. As the pacing sites changed from the anterior to posterior of the free wall, lead I showed a shift from the QS notch (+) type to R, while a shift from rR' to Rr' (or rR' unchanged) was found in leads II and III. The depth of the QS wave in leads aVR and aVL showed a tendency for aVR to be deeper than aVL toward the posterolateral attachment of both the septum and free wall, whereas aVL tended to be deeper than aVR toward the anterior attachment. The initial r waves in V1 and V2 became greater as the pacing site was positioned at a higher or more posterior location. These findings may provide more precise and clinically useful diagnostic information on the site of the origin of idiopathic VT originating from the RVOT by a 12-lead ECG.     

The Use of the Block Cycle Length as a Safe and Efficient Means of Interrupting Sustained Ventricular Tachycardia and Its Pharmacological Modification

In nine patients who had inducible monomorphic sustained ventricular tachycardia (VT), rapid pacing was performed in 11 episodes of morphologically distinct VT at progressively shorter cycle lengths and VT was interrupted at a critical cycle length. The VT interrupting critical cycle length was defined as the block cycle length (BCL) and the effect of Class I antiarrhythmic drugs were examined. Both the VT cycle length (VTCL) and the BCL were prolonged after administration of either drug. The overall mean ratio of the BCL to the VTCL was unchanged after procainamide administration, but increased after the use of mexiletine. The ratio, however, varied in individual VTs and the BCL after treatment with Class I antiarrhythmic drugs could not be predicted from the ratio baseline value, although the ratio was always > 60% and the hazard of VT acceleration might be avoided if the BCL is used.