Radiofrequency catheter ablation of idiopathic left ventricular tachycardia guided by a Purkinje potential

Radiofrequency catheter ablation for management of symptomatic ventricular ectopic activity

OBJECTIVES

This study assessed the useful role of intracardiac mapping and radiofrequency catheter ablation in eliminating drug-refractory monomorphic ventricular ectopic beats in severely symptomatic patients.

BACKGROUND

Ventricular ectopic activity is commonly encountered in clinical practice. Usually, it is not associated with life-threatening consequences in the absence of significant structural heart disease. However, frequent ventricular ectopic beats can be extremely symptomatic and even incapacitating in some patients. Currently, reassurance and pharmacologic therapy are the mainstays of treatment. There has been little information on the use of catheter ablation in such patients.

METHODS

Ten patients with frequent and severely symptomatic monomorphic ventricular ectopic beats were selected from three tertiary care centers. The mean frequency +/- SD of ventricular ectopic activity was 1,065 +/- 631 beats/h (range 280 to 2,094) as documented by baseline 24-h ambulatory electrocardiographic (ECG) monitoring. No other spontaneous arrhythmias were documented. These patients had previously been unable to tolerate or had been unsuccessfully treated with a mean of 5 +/- 3 antiarrhythmic drugs. The site of origin of ventricular ectopic activity was accurately mapped by using earliest endocardial activation time during ectopic activity or pace mapping, or both.

RESULTS

During electrophysiologic study, no patient had inducible ventricular tachycardia. The ectopic focus was located in the right ventricular outflow tract in nine patients and in the left ventricular posteroseptal region in one patient. Frequent ventricular ectopic beats were successfully eliminated by catheter-delivered radiofrequency energy in all 10 patients. The mean number of radiofrequency applications was 2.6 +/- 1.3 (range 1 to 5). No complications were encountered. During a mean follow-up period of 10 +/- 4 months, no patient had a recurrence of symptomatic ectopic activity, and 24-h ambulatory ECG monitoring showed that the frequency of ventricular ectopic activity was 0 beat/h in seven patients, 1 beat/h in two patients and 2 beats/h in one patient.

CONCLUSIONS

Radiofrequency catheter ablation can be successfully used to eliminate monomorphic ventricular ectopic activity. It may therefore be a reasonable alternative for the treatment of severely symptomatic, drug-resistant monomorphic ventricular ectopic activity in patients without significant structural heart disease.

The use of radiofrequency energy in pediatric cardiology

The use of radiofrequency energy for the treatment of supraventricular tachycardia in pediatric patients has gained widespread acceptance, especially for tachyarrhythmias associated with palpitations, dizziness, presyncope or syncope, cardiomyopathy, and cardiac arrest. Ablation of the substrate supporting atrioventricular reentry, atrioventricular node reentry, and automatic atrial tachycardia yields a 90%-98% success rate with low incidence (< 1%) of complications and adverse side-effects. Ablation of intra-atrial reentry, including atrial flutter and fibrillation, appears to be promising and would be a significant advance in the management of patients following extensive atrial surgery for congenital heart disease. Radiofrequency energy is also used to treat various forms of idiopathic ventricular tachycardia. Finally, radiofrequency energy has been extended to control the ventricular rate associated with malignant atrial tachycardia by either modification or ablation of the atrioventricular node, and subsequent pacemaker implant. Long-term outcome of radiofrequency ablation is unknown, but the short-to-intermediate (1-5 yrs) outcome is excellent, with low recurrence rate of the tachycardia, no proarrhythmic effect, and excellent clinical state.

Catheter ablation of idiopathic left ventricular tachycardia

Idiopathic left ventricular tachycardia (ILVT) characterized by right bundle branch block, left axis morphology, response to verapamil and inducibility from the atrium in patients without structural heart disease may represent a distinct clinical entity. We report our experience with catheter ablation of this uncommon arrhythmia using radiofrequency energy (RF) and/or direct current (DC) shocks. Six men and 2 women, aged 16-50 years (mean +/- SD, 32 +/- 13), had recurrent VT for 16 +/- 16 years with a mean frequency of 4 +/- 3 episodes/year. Three patients had syncope during VT. None had identifiable structural heart disease. Catheter ablation was guided by earliest endocardial activation, presence of a high frequency presystolic potential and/or pacemapping of the left ventricle. The left ventricle was accessed via a retrograde aortic approach in 6 patients, a transeptal approach in 1 patient, and a combined approach in the remaining patient. All patients had inducible right bundle branch block morphology, left axis VT with a mean cycle length (CL) of 361 +/- 61 ms. A presystolic potential preceding ventricular activation and the His potential during VT was identified in 4 patients. All ablation sites were identified in a relatively uniform location, in the inferoapical left ventricle. Noninducibility of VT was obtained with RF in 3 patients and with DC in 5 patients. In 1 patient, DC delivery after unsuccessful RF prevented further inducibility. Similarly, RF was successful in 1 patient in whom an initial DC attempt was ineffective. Mean total procedure time was 282 +/- 51 minutes and mean total fluoroscopy time was 40 +/- 15 minutes. There were no complications. One patient treated with DC shock had recurrence of VT during treadmill test the day after ablation and refused repeat ablation. During a mean follow-up of 17 +/- 13 months, no VT recurrences or other cardiovascular events occurred. In conclusion, catheter ablation in the inferoapical left ventricle is an effective treatment for this type of ILVT. RF energy can be safely complemented by low energy DC shocks when the former is ineffective.

Idiopathic left ventricular tachycardia: new insights into electrophysiological characteristics and radiofrequency catheter ablation

OBJECTIVES

This study was performed to investigate the electrophysiological characteristics of idiopathic left ventricular tachycardia and to determine the feasibility of radiofrequency catheter ablation for nonpharmacological cure.

BACKGROUND

The underlying electrophysiological mechanism of idiopathic left ventricular tachycardia with right bundle branch block morphology and left-axis deviation is presently not known. Additionally, only limited data describing the results of radiofrequency catheter ablation for treatment of idiopathic left ventricular tachycardia so far exist.

METHODS

Electrophysiological studies and radiofrequency catheter ablation were performed in 5 patients (3 male and 2 female, mean age 31 +/- 10 years) with idiopathic left ventricular tachycardia (cycle length 376 +/- 72 msec). The patients had a history of recurrent palpitations of 4 +/- 1 years and had been treated unsuccessfully with 2 +/- 1 antiarrhythmic drugs. Sustained ventricular tachycardia with right bundle branch block morphology and left- or right-axis deviation was documented in all patients.

RESULTS

Inducibility with critically timed ventricular extrastimuli, inverse relationships of the coupling interval of the initiating extrastimulus and the interval to the first beat of the tachycardia, continuous diastolic or mid-diastolic electrical activity during ventricular tachycardia, and fragmented late potentials during sinus rhythm suggested reentrant activation as the underlying mechanism in three patients. On the other hand, induction dependent on isoproterenol infusion and rapid ventricular pacing and exercise inducibility indicated different electrophysiological characteristics in the remaining two patients. During electrophysiological study, intravenous verapamil terminated ventricular tachycardia in all patients, whereas ventricular tachycardia did not respond to intravenous adenosine, autonomic maneuvers, or intravenous beta-blocking agent esmolol. Catheter mapping revealed earliest endocardial activation during ventricular tachycardia in different areas of the left ventricular septum being distributed from the base to the mid-apical portion of the septum in all patients. In 4 of 5 patients, radiofrequency catheter ablation (median number of pulses 4, range 1-9) resulted in complete abolition of idiopathic left ventricular tachycardia during a follow-up of 4-43 months (median 10) without antiarrhythmic drugs. Successful target sites for catheter ablation included continuous diastolic or mid-diastolic electrical activity during ventricular tachycardia and late potentials during sinus rhythm (2 patients), polyphasic fragmented presystolic potentials during ventricular tachycardia (1 patient), and pace mapping with identical QRS morphology compared to the ventricular tachycardia and "earliest" detectable activity during tachycardia (1 patient). No procedure related complications occurred.

CONCLUSIONS

Two different patterns of electrophysiological properties of idiopathic left ventricular tachycardia were observed, indicating that this arrhythmia entity does not represent a homogeneous group. The "origin" of the tachycardias as identified by successful radiofrequency catheter ablation was located in different areas of the left ventricular septum and was distributed from the base to the mid-apical region. Radiofrequency catheter ablation was an effective and safe treatment modality in most of these patients. Distinct target site characteristics for successful catheter ablation including polyphasic diastolic activity during tachycardia and fragmented late potentials during sinus rhythm could be identified.

NASPE/ACC/AHA/ESC medical/scientific statement special report--clinical investigation of antiarrhythmic devices: a statement for healthcare professionals from a Joint Task Force of the North American Society of Pacing and Electrophysiology, the American College of Cardiology, the American Heart Association, and the Working Groups on Arrhythmias and Cardiac Pacing of the European Society of Cardiology

The goal of radiofrequency catheter ablation and the criterion for efficacy is the elimination of arrhythmogenic myocardium. The application of radiofrequency current in the heart clearly results in lower morbidity and mortality rates than thoracic and cardiac surgical procedures in general, and comparisons of therapy with radiofrequency catheter ablation and therapy with thoracic and cardiac surgical procedures in randomized clinical trials are unwarranted. Trials of radiofrequency catheter ablation versus medical or implantable cardioverter defibrillator therapy may be indicated in certain conditions, such as ventricular tachycardia associated with coronary artery disease. Randomized trials are recommended for new and radical departures in technology that aim to accomplish the same goals as radiofrequency catheter ablation. Surveillance using registries and/or databases is necessary in the assessment of long-term safety and efficacy.

Clinical investigation of antiarrhythmic devices. A statement for healthcare professionals from a joint task force of the North American Society of Pacing and Electrophysiology, the American College of Cardiology, the American Heart Association, and the Working Groups on Arrhythmias and Cardiac Pacing of the European Society of Cardiology

The goal of radiofrequency catheter ablation and the criterion for efficacy is the elimination of arrhythmogenic myocardium. The application of radiofrequency current in the heart clearly results in lower morbidity and mortality rates than thoracic and cardiac surgical procedures in general, and comparisons of therapy with radiofrequency catheter ablation and therapy with thoracic and cardiac surgical procedures in randomized clinical trials is unwarranted. Trials of radiofrequency catheter ablation versus medical or implantable cardioverter-defibrillator therapy may be indicated in certain conditions, such as ventricular tachycardia associated with coronary artery disease. Randomized trials are recommended for new and radical departures in technology that aim to accomplish the same goals as radiofrequency catheter ablation. Surveillance using registries and/or databases is necessary in the assessment of long-term safety and efficacy.

Microwave ablation of the atrioventricular junction in open-chest dogs

The use of microwave energy for ablation of the atrioventricular (AV) junction was examined in open-chest dogs. Using a specially designed microwave catheter and a 2450 MHz generator, microwave energy was delivered to the AV junction according to one of two protocols. In protocol 1, increasing amounts of energy were delivered until irreversible AV block occurred. In protocol 2, only two applications of energy were used, one at low energy and the other at an energy found to be high enough to cause irreversible AV block. Each dog received between one and six applications of microwave energy. The amount of energy delivered per application ranged from 25.6 to 311.4 J. No AV block was seen at 59.4 +/- 28.3 J. Reversible AV block was seen with an energy of 120.6 +/- 58 J. Irreversible AV block was seen at 188.1 +/- 75.9 J. Irreversible AV block could be achieved in each animal. There was no difference in the energy required to cause irreversible AV block between the two protocols. The tissue temperature measured near the tip of the microwave catheter was correlated with both the amount of energy delivered and the extent of AV block caused. Histologic examination demonstrated coagulation necrosis of the conduction system. Microwave energy is a feasible alternative energy source for myocardial ablation. Since tissue damage is due exclusively to heating and the resulting rise in temperature can be measured, microwave energy may have advantages over currently existing energy sources in terms of both titrating delivered energy and monitoring the extent of tissue destruction.

Long-term outcome of verapamil-sensitive sustained left ventricular tachycardia in patients without structural heart disease

OBJECTIVES

This study attempted to determine the long-term outcome of verapamil-sensitive sustained left ventricular tachycardia in patients without apparent structural heart disease.

BACKGROUND

Several types of idiopathic ventricular tachycardia have been reported, and their clinical, electrophysiologic and electropharmacologic characteristics are different. It is possible that the prognosis of each type of ventricular tachycardia might also be different.

METHODS

We studied mortality and morbidity in 37 consecutive patients (27 male, 10 female; mean [+/- SD] age 33 +/- 14 years) with verapamil-sensitive sustained left ventricular tachycardia who had no apparent structural heart disease. Patients were followed up for 1 to 13 years (mean 5.8). Verapamil repeatedly terminated ventricular tachycardia in all patients. Ventricular tachycardia originated from the inferior and inferoseptal regions of the left ventricle in 33 patients and the superior and superioseptal regions in 4. Severity of ventricular tachycardia was classified according to the extent to which symptoms limited daily activities. Ventricular tachycardia was mild (minimal limitation) in 14 patients, moderate (some limitation) in 17 and severe (severe limitation) in 6.

RESULTS

Fourteen patients with mild ventricular tachycardia were followed up without any drug therapy, and the ventricular tachycardia remained mild in all patients. Antiarrhythmic therapy was initiated empirically in the 23 patients with moderate and severe ventricular tachycardia (verapamil in 20, propranolol in 2, digoxin in 1). Moderate ventricular tachycardia became mild ventricular tachycardia after drug therapy in all patients, but the six patients with severe ventricular tachycardia showed no improvement. The six patients with severe ventricular tachycardia had nonpharmacologic therapy (cryosurgery in one, catheter ablation in four, antitachycardia pacing device in one). During the follow-up period, all patients remained alive except for one who died suddenly after implantation of an antitachycardia pacing device.

CONCLUSIONS

1) The long-term prognosis of verapamil-sensitive sustained left ventricular tachycardia in patients without apparent structural heart disease is good. 2) Verapamil is the drug of choice for alleviating symptoms, but nonpharmacologic therapy is necessary in some patients.

Insights into the electrophysiology of ventricular tachycardia gained by the catheter ablation experience: "learning while burning"

The success of catheter ablation has significantly improved the treatment of patients with cardiac arrhythmias and has established electrophysiology as an increasingly interventional subspecialty. Some members of the electrophysiology community have expressed concern that this success has been purchased at the cost of undermining what had been our primary concern: understanding the anatomic and physiologic basis of arrhythmia syndromes. In many laboratories, endpoints such as case load and primary success have eclipsed physiologic investigation. Despite these trends, however, catheter ablation is not inherently at odds with investigation and education. On the contrary, because the lesions delivered with current techniques are much more discrete than the effects of antiarrhythmic agents or surgical ablation, catheter ablation can be used as a research tool directed toward a more precise understanding of arrhythmia substrates. Conscious attempts at "learning while burning" have already provided important and unique information about arrhythmia pathogenesis.

Radiofrequency ablation of fascicular tachycardia: efficacy of pace-mapping and implications on tachycardia origin

Verapamil-sensitive but adenosine resistant left ventricular tachycardia (fascicular tachycardia) is a recognised cause of ventricular tachycardia occurring in patients without overt cardiac disease. This study addresses (1) the efficacy of radiofrequency ablation guided by pace-mapping technique in the treatment of this tachycardia, and (2) the location of this tachycardia in the left ventricle as assessed by simultaneous ventriculography. Five patients (two women and three men, mean age 25 +/- 8 years) with ventricular tachycardia exhibiting a right bundle branch block and left axis deviation morphology, with documented response to verapamil but resistance to intravenous adenosine triphosphate were studied. Biplane left ventricular cineangiography was first performed to visualise the topography of the left ventricle. Pace-mapping at a rate within 10 beats/min of the tachycardia rate was performed, and the concordance of paced QRS configuration with that of the induced tachycardia was compared for each of the 12 leads for major or minor differences. A perfect pace-map could be achieved in all five patients (two in posteroseptal left ventricle and three in the posterior left ventricular wall). Five of eight applications at an identical pace-map resulted in suppression of tachycardia induction, whereas none of the 39 applications at sites with a less identical map was successful (P < 0.001). After a successful procedure, there was no recurrence as assessed clinically, by non-invasive monitoring (event recording, Holter monitoring and exercise testing for all patients) and repeat electrophysiology testing (three patients) during a follow-up of 12 +/- 3 months. Thus radiofrequency ablation guided by pace-mapping technique is a highly efficacious treatment for fascicular tachycardia. The response to radiofrequency ablation suggests the origin of tachycardia as reentry circuits involving the lower septum or posterior part of the left ventricle close to or within the endocardial surface.

Three-dimensional endocardial mapping system using a novel x-ray imager and locating catheter

Percutaneous radiofrequency catheter ablation (RFCA) has a very high success rate for certain arrhythmias, such as Wolff-Parkinson-White syndrome and idiopathic ventricular tachycardias in the right ventricular outflow tract. These arrhythmias are typically characterized by a single site of arrhythmogenic tissue that is well bounded by anatomic markers. Success rates for RFCA for reentrant ventricular tachycardias, tachycardias not closely associated with anatomic markers, and those having larger tissue areas requiring multiple overlapping lesions have been significantly lower. An endocardial mapping system is being developed that includes a fluoroscopic imager that scans the field of view with a series of small x-ray beams and electrophysiology catheters modified to include miniature x-ray sensor elements. Preliminary work indicates that the accuracy of determining the mapping catheter location relative to the reference catheters will be +/- 1.5 mm. Substituting a highly accurate three-dimensional coordinate system for anatomic markers could improve the success rate of RFCA for complex arrhythmias.