Phenylpropanolamine, a nonprescription drug with potentially fatal side effects

[Short history of the DC-Catheter-Ablation]

Direct current (DC) catheter ablation in 5 patients aiming to interrupt rapid atrioventricular (AV) conduction with atrial fibrillation and subsequent pacemaker implantation was first published by M. M. Scheinman et al. (San Francisco, CA, USA) in 1982. In Germany, L. Seipel, G. Breithardt, and M. Borggrefe reported their first experience with DC catheter ablation in 1984, followed by the group in Bonn (M. Manz and B. Lüderitz) in 1985. The first international DC catheter ablation registry, which also included four German centers, reported DC catheter ablation results of 127 patients in 24 centers in 1984. Complete AV block was achieved in 71% patients. In 1992, the Hannover group (H‑J. Trappe, H. Klein and J. Huang) reported results of DC catheter ablation of AV conduction performed between 1983 and 1990 in 100 patients (86% with rapid atrial fibrillation, 14% with AV-node reentry tachycardias). The first successful DC catheter ablation in a patient with Wolff-Parkinson-White (WPW) syndrome was reported in 1985 by F. Morady et al. (San Francisco, CA, USA). In 1987, M. Borggrefe et al. were the first to report a switch from DC catheter ablation to a high-frequency (HF) catheter ablation procedure in a patient with WPW syndrome. The use of DC catheter ablation to treat ventricular tachycardia (VT) was described by G. O. Hartzler (Kansas City, MO, USA) in 3 patients in 1983. M. Borggrefe et al. (1989) reported on 24 patients who underwent DC catheter ablation for VT. Of those, 17 patients did not have VT recurrence within the following 14 months. In 1994, the Hannover group (H-J Trappe, H. Klein) published their 5‑year long-term results of DC catheter ablation of VT in 51 patients. VT recurrence occurred in 57% patients and overall mortality was also high (16%). A comparison of DC catheter ablation with HF catheter ablation for recurrent VT was reported in 1994 by G. Gonska et al. (Göttingen, Germany). After 2 years follow-up, success rates were not found to be significantly different.

Radiofrequency ablation: technological trends, challenges, and opportunities

More than three decades have passed since utilization of radiofrequency (RF) ablation in the treatment of cardiac arrhythmias. Although several limitations and challenges still exist, with improvements in catheter designs and delivery of energy the way we do RF ablation now is much safer and more efficient. This review article aims to give an overview on historical advances on RF ablation and challenges in performing safe and efficient ablation.

Electrophysiology and ablation of arrhythmias

Major advances in diagnosis and treatment of arrhythmias have created the subspecialty of cardiac electrophysiology. This article reviews supraventricular and ventricular arrhythmias and outlines the indications and process of electrophysiological testing, arrhythmia mechanism and their treatment by catheter ablation.

Cardiac arrhythmias: the quest for a cure: a historical perspective

During the last 40 years, much progress has been made in our understanding and management of cardiac arrhythmias. A major step in the late 1960s was to combine programmed electrical stimulation of the heart with intracardiac activation recording. This allowed: 1) localization of the site of the block in the atrioventricular conduction system in patients with bradycardia; and 2) identification of the site of origin and the mechanism of supraventricular and ventricular tachycardia. Combining information from intracardiac studies with findings on the 12-lead electrocardiogram (ECG) resulted in much better localization of conduction abnormalities and arrhythmias using the ECG. This new knowledge led to the development of new therapies, such as bradycardia and antitachycardia pacing, and surgery for supraventricular and ventricular tachycardia. A very important development in the treatment of life-threatening arrhythmias was the implantable defibrillator. Growing concern about failure to protect patients at risk for dying suddenly with antiarrhythmic drugs led to a rapid increase in their number. Cure by catheter ablation became possible for patients with different types of arrhythmias. Genetic analysis allowed the identification of different monogenic arrhythmic diseases. Several challenges remain: the epidemic of atrial fibrillation, arrhythmias in heart failure, and sudden death out-of-hospital. One-fifth of all deaths are sudden and unexpected. The important issue is how we are going to prevent these unnecessary deaths from occurring.

We have come a long way with device therapy: historical perspectives on antiarrhythmic electrotherapy

The history of device therapies is long and fascinating. In the beginning, there is not simply the anatomy and physiology of the heart, but also analysis of the pulse, which indicates the activity of the heart. The analysis of the (peripheral) pulse as a mechanical expression of heart activity goes back several millennia. In China, in 280 BC, Wang Shu He wrote 10 books about the pulse. The Greeks called the pulse "sphygmos"; thus, sphygmology deals with a theory of this natural occurrence. In Roman times, Galen interpreted the various types of pulse according to the widespread presumption of the time that each organ in every disease has its own form of pulse. The growing clinical importance of electrical cardiac stimulation was recognized and renewed as Zoll in 1952 described a successful resuscitation in cardiac standstill by external stimulation. Meanwhile, millions of patients with cardiac arrhythmias worldwide have been treated with pacemakers in the last 40 years. The concept of a fully automatic implantable cardioverter defibrillator system for recognition and treatment of ventricular tachyarrhythmias was first suggested in 1970. The first implantation of the device in a human being was performed in February 1980. Further developments involved atrial and atrioventricular defibrillators, radiofrequency ablation, laser therapy, and advanced antiarrhythmic surgery. Since 1990, there has been a growing interest in using cardiac pacing as additional treatment in severe cardiac failure. Recent reports have suggested that intervention with left ventricular or biventricular pacing may be helpful for a subgroup of patients with congestive heart failure. Despite encouraging (preliminary) acute and short-term results, pacing strategies for heart failure still are limited and currently regarded as investigational. Advances in the field of therapeutic application of pharmacologic and electrical tools as well as alternative methods will continue as rapidly as before and provide us further significant aid in taking care of patients.

An overview of contemporary approaches to antiarrhythmic therapy

This review discusses the evolution in the approach to the therapy of cardiac arrhythmias that has occurred during the past 2 decades. The major changes have been driven by advances in understanding arrhythmia mechanisms, in bioengineering, and in clinical trials. It seems likely that progress in understanding the cellular and molecular basis of arrhythmias and their response to drug therapy may allow further identification of patient subsets in which specific therapies are indicated or contraindicated.

LocaLisa: new technique for real-time 3-dimensional localization of regular intracardiac electrodes

BACKGROUND

Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate if a systematic lesion pattern is required in the treatment of complex arrhythmogenic substrates.

METHODS AND RESULTS

We developed a new technique for online 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy within the right atrium, right ventricle, and left ventricle by comparing measured and true interelectrode distances of a decapolar catheter. Long-term stability was analyzed by localization of the most proximal His bundle before and after slow pathway ablation. Electrogram recordings were unaffected by the applied electrical field. Localization data from 3 catheter positions, widely distributed within the right atrium, right ventricle, or left ventricle, were analyzed in 10 patients per group. The relationship between measured and true electrode positions was highly linear, with an average correlation coefficient of 0.996, 0.997, and 0.999 for the right atrium, right ventricle, and left ventricle, respectively. Localization accuracy was better than 2 mm, with an additional scaling error of 8% to 14%. After 2 hours, localization of the proximal His bundle was reproducible within 1.4+/-1.1 mm.

CONCLUSIONS

This new technique enables accurate and reproducible real-time localization of electrode positions in cardiac mapping and ablation procedures. Its application does not distort the quality of electrograms and can be applied to any electrode catheter.

Predictors of fluoroscopy time and estimated radiation exposure during radiofrequency catheter ablation procedures

The objective of this study was to identify factors that predict fluoroscopy duration and radiation exposure during catheter ablation procedures. The patient population included 859 patients who participated in the Atakr Ablation System clinical trial at 1 of 9 centers (398 male and 461 female patients, aged 36 +/- 21 years). Each patient underwent catheter ablation of an accessory pathway, the atrioventricular junction, or atrioventricular nodal reentrant tachycardia using standard techniques. The duration of fluoroscopy was 53 +/- 50 minutes. Factors identified as independent predictors of fluoroscopy duration included patient age and sex, the success or failure of the ablation procedure, and the institution at which the ablation was performed. Catheter ablation in adults required longer fluoroscopy exposure than it did in children. Men required longer durations of fluoroscopy exposure than did women. The mean estimated "entrance" radiation dose was 1.3 +/- 1.3 Sv. The dose needed to cause radiation skin injury was exceeded during 22% of procedures. The overall mean effective absorbed dose from catheter ablation procedures was 0.025 Sv for female patients and 0.017 Sv for male patients. This degree of radiation exposure would result in an estimated 1,400 excess fatal malignancies in female patients and 2,600 excess fatal malignancies in male patients per 1 million patients.

Catheter ablation of the accessory pathways of the Wolff-Parkinson-White syndrome and its variants

The basis of arrhythmias in the Wolff-Parkinson-White (WPW) syndrome and its variants is the presence of accessory atrioventricular connections. Those variants include the concealed form of the WPW syndrome, the permanent form of junctional reciprocating tachycardia, and Mahaim preexcitation. In all forms of symptomatic WPW syndrome, catheter ablation of the accessory atrioventricular connections using radiofrequency current has become the treatment of choice. This review traces the development of this therapy, outlines the basics of the technique, summarizes the results reported in the largest series, indicate remaining areas of controversy, and discusses the indications and limitations of radiofrequency ablation therapy.

Catheter ablation in supraventricular tachycardia

The evolution of catheter ablation for the treatment of supraventricular tachycardias represents a major advance in the management of cardiac arrhythmias. Excellent results in the majority of patients undergoing the procedure, together with a low rate of early complications and a brief hospitalization, make catheter ablation a highly cost-effective permanent cure. At present, however, its place in relation to alternate therapies in the management of supraventricular tachycardias has not been clearly established owing to unresolved risk-benefit issues. Continuing technical advances will likely enable catheter ablation to be successfully applied to a broader range of cardiac arrhythmias.

Results of a comparative study of low energy direct current with radiofrequency ablation in patients with the Wolff-Parkinson-White syndrome

OBJECTIVE

To compare two new power sources for catheter ablation in patients with the Wolff-Parkinson-White syndrome.

DESIGN

120 consecutive patients with accessory pathways had catheter ablation. Low energy direct current (DC) was used in the first 60 patients and radio-frequency current in the next 60 patients.

SETTING

Electrophysiological laboratory of a large heart institute.

PATIENTS

72 men and 48 women (mean (SD) age 35 (14) years (range 9-75)). The accessory pathways were in the left free wall in 73 patients. They were posteroseptal in 35 patients, in the right free wall in five, and anteroseptal in seven. There was no significant difference in the clinical or electrophysiological variables between the two ablation groups.

RESULTS

Catheter ablation with low energy direct current was successful in 55/60 patients (92%) and radiofrequency energy was successful in 52/60 patients (87%). Low energy direct current was also successful in four of the eight patients in whom radiofrequency ablation had failed. Radiofrequency ablation was successful in two of the five patients in whom low energy direct current ablation had failed. The mean (SD) procedure and fluoroscopy times for successful ablation were 3.2 (1.5) h and 61 (40) min respectively. These times were similar for both power sources. Accessory pathway conduction recurred in 17 patients (28%) who had low energy direct current and four patients (7%) who received radiofrequency energy (p < 0.004). All patients with recurrence of an accessory pathway had successful re-ablation.

CONCLUSIONS

Both new power sources successfully ablated accessory pathways, (overall success rate 94% (113/120 patients)). Radiofrequency ablation, however, did not require general anaesthesia and was associated with a significantly lower rate of recurrence of accessory pathway conduction. Therefore radiofrequency should be used initially for ablation. Low energy direct current may be most useful as a back-up in patients in whom radiofrequency ablation fails.

Radiofrequency endocardial catheter ablation of accessory atrioventricular pathway atrial insertion sites

BACKGROUND

High rates of success using radiofrequency ablation energy have rapidly transformed catheter ablation from an investigational procedure to the nonpharmacological therapy of choice for symptomatic Wolff-Parkinson-White syndrome. Prior studies of radiofrequency accessory pathway ablation were based on a ventricular approach. Risks associated with prolonged arterial catheter manipulation, retrograde left ventricular catheterization, and production of ventricular lesions required for successful ventricular insertion ablation can be avoided using atrial insertion ablation procedures. The purpose of the present study was to define the safety and efficacy of accessory pathway ablation using radiofrequency energy delivered solely to accessory atrioventricular pathway atrial insertion sites.

METHODS AND RESULTS

One hundred fourteen patients with accessory pathway-mediated tachycardia underwent attempted radiofrequency current ablation at the accessory pathway atrial insertion site. All catheters were introduced transvenously. Left-sided accessory pathways were approached using transseptal left atrial catheterization techniques. Retrograde localization of the atrial insertion site during reentrant tachycardia was characterized by 40 +/- 15-msec local ventriculoatrial and 79 +/- 17-msec surface QRS to local atrial electrogram intervals. Presumed accessory pathway potentials were present in only 30% of ablation site electrograms. Successful ablation required 6.2 +/- 5.3 radiofrequency energy applications. Cumulative energy dose required for success was 2,341 +/- 2,233 J. There were no complications associated with transseptal catheterization. Energy delivery to accessory pathway atrial insertion sites was associated with non-life-threatening complications in two patients. Recurrent conduction requiring repeat ablation occurred in 10 of 115 (9%) successfully ablated accessory pathways, all within 1 month of the ablation procedure. After 21.2 +/- 4.6 months of follow-up, 108 of 114 (95%) patients are asymptomatic and without evidence of accessory pathway conduction.

CONCLUSIONS

The atrial insertion approach to accessory pathway ablation is safe and highly effective. This approach compares favorably with the retrograde ventricular insertion ablation technique. Atrial insertion ablation eliminates the need to produce ventricular lesions and avoids the risks of prolonged arterial catheter manipulation and retrograde left ventricular catheterization.

Long-term effects of percutaneous laser balloon ablation from the canine coronary sinus

BACKGROUND

Radiofrequency catheter ablation of left-sided accessory pathways is becoming the first line of therapy for patients with symptomatic Wolff-Parkinson-White syndrome. Nevertheless, alternative ablation techniques merit development, at least as supplementary modalities for cases in which conventional ablation approaches may prove unsuccessful. We recently reported the short-term results with transcatheter laser balloon ablation from the coronary sinus in a canine model, proving that the procedure is feasible for the potential ablation of left-sided accessory pathways. We now report the effects of percutaneous transcatheter laser balloon ablation in a chronic canine model.

METHODS AND RESULTS

Twenty adult mongrel dogs were studied. After baseline coronary arteriography, left ventriculography, and coronary sinus angiography were obtained, 15 dogs received two or three consecutive laser doses from the coronary sinus of 30-40 W for 15-30 seconds, for a total cumulative energy of 1,200-2,400 J. The five remaining animals underwent a procedure consisting of balloon sham inflation without laser exposure and served as controls. After a mean follow-up of 6 weeks, the angiographic procedures were repeated, and the animals were killed. The mean extent of the fibrotic lesion was 15 mm long, 6 mm wide, and 4.5 mm deep and involved the coronary sinus wall, atrium, and, frequently, the summit of the posterior left ventricular wall. Six animals (four in the study group and two in the control group) showed asymptomatic narrowing of the coronary sinus lumen but always with total angiographic reconstitution due to extensive collateral circulation. The circumflex artery and mitral valve were intact angiographically and histologically in all animals.

CONCLUSIONS

Percutaneous transcatheter laser balloon ablation via the coronary sinus produces a lesion that may be anatomically well suited for left-sided accessory pathway ablation. Although coronary sinus narrowing may occur, adverse physiological effects are unlikely due to the development of extensive collateral circulation. Systematic clinical studies of this new approach to catheter ablation appear warranted.

Catheter ablation of hemodynamically compromising incessant atrioventricular tachycardia

A 27-year-old woman was admitted to the Georgetown University Hospital with refractory hemodynamically compromising incessant atrioventricular tachycardia. A single left-sided accessory pathway was identified and successfully modified acutely. Endocardial delivery of direct current energy provided an extremely effective therapeutic intervention resulting in termination of atrioventricular tachycardia and restoration of stable hemodynamic status. Although a second ablation procedure was necessary to permanently interrupt accessory pathway conduction, the patient has remained free of symptoms without medications for 13 months.

Catheter ablation of accessory atrioventricular pathways (Wolff-Parkinson-White syndrome) by radiofrequency current

BACKGROUND

Surgical or catheter ablation of accessory pathways by means of high-energy shocks serves as definitive therapy for patients with Wolff-Parkinson-White syndrome but has substantial associated morbidity and mortality. Radiofrequency current, an alternative energy source for ablation, produces smaller lesions without adverse effects remote from the site where current is delivered. We conducted this study to develop catheter techniques for delivering radiofrequency current to reduce morbidity and mortality associated with accessory-pathway ablation.

METHODS

Radiofrequency current (mean power, 30.9 +/- 5.3 W) was applied through a catheter electrode positioned against the mitral or tricuspid annulus or a branch of the coronary sinus; when possible, delivery was guided by catheter recordings of accessory-pathway activation. Ablation was attempted in 166 patients with 177 accessory pathways (106 pathways in the left free wall, 13 in the anteroseptal region, 43 in the posteroseptal region, and 15 in the right free wall).

RESULTS

Accessory-pathway conduction was eliminated in 164 of 166 patients (99 percent) by a median of three applications of radiofrequency current. During a mean follow-up (+/- SD) of 8.0 +/- 5.4 months, preexcitation or atrioventricular reentrant tachycardia returned in 15 patients (9 percent). All underwent a second, successful ablation. Electrophysiologic study 3.1 +/- 1.9 months after ablation in 75 patients verified the absence of accessory-pathway conduction in all. Complications of radiofrequency-current application occurred in three patients (1.8 percent): atrioventricular block (one patient), pericarditis (one), and cardiac tamponade (one) after radiofrequency current was applied in a small branch of the coronary sinus.

CONCLUSIONS

Radiofrequency current is highly effective in ablating accessory pathways, with low morbidity and no mortality.

Percutaneous radiofrequency catheter ablation for supraventricular arrhythmias in children

Nineteen procedures were performed in 17 children, aged 10 months to 17 years, using catheter radiofrequency applications for the management of malignant or drug-resistant supraventricular tachyarrhythmias. Diagnoses were junctional ectopic tachycardia in 1 patient, atrioventricular (AV) node reentrant tachycardia in 4 and accessory pathway-mediated tachycardia in 12. Accessory pathway locations were left lateral (n = 4), posteroseptal (n = 3), left posterior (n = 2), right posterolateral (n = 1), right posterior paraseptal (n = 1), right intermediate septal (n = 1) and right anterior (n = 1). Ablation of accessory pathways was performed using 20 to 40 W of energy. The catheter was passed retrograde to the left ventricle in patients with a left-sided pathway and anterograde to the right atrium in those with a right-sided or posteroseptal pathway. In the 12 patients with an accessory pathway, radiofrequency applications were successful in 11 pathways and failed in 2. There were no recurrences of accessory pathway-mediated tachycardia. Atrioventricular node reentrant tachycardia was treated by AV node modification using 15 W of energy applied until first degree AV block occurred. After radiofrequency catheter ablation, there was a prolonged AH interval, tachycardia was not inducible and tachycardia recurred in one patient. For the patient with junctional ectopic tachycardia, 15 to 18 W of energy was delivered at the site of the maximal His bundle electrogram until sinus rhythm and normal AV conduction appeared. After a recurrence, a second procedure abolished tachycardia and AV conduction. In summary, radiofrequency catheter ablation was initially successful in 17 of 19 procedures and ultimately curative in 14 (82%) of 17 patients with no serious complications. Radiofrequency catheter ablation appears to be a safe and effective method for the management of supraventricular tachyarrhythmias in children.

Percutaneous catheter modification of the atrioventricular node. A potential cure for atrioventricular nodal reentrant tachycardia

Our purpose was to describe a technique of atrioventricular (AV) node modification for patients with drug refractory AV nodal reentrant tachycardia (AVNRT). Nine patients (mean age, 45 +/- 20; range, 14-82) with recurrent drug refractory AVNRT (n = 8) or sudden cardiac death thought to be precipitated by AVNRT (n = 1) underwent a percutaneous catheter procedure to modify AV nodal function. The area between the electrode recording the maximal His-bundle electrogram and the ostium of the coronary sinus was divided into three zones. Perinodal direct current shocks of 100-300 J were delivered to one (n = 2), two (n = 3), or three (n = 4) zones without complications. The procedure endpoints were modification of AV conduction (either first degree AV block or complete retrograde ventriculo-atrial [VA] block) and failure to induce AVNRT before or after isoproterenol and/or atropine administration. Six of nine patients (67%) have had no inducible or spontaneous AVNRT over a mean follow-up of 12.3 +/- 4.1 months (range, 4.5-17). One of the six underwent repeat, successful modification, because AVNRT was inducible at restudy 2 days after the initial procedure. AVNRT recurred in three patients (33%), one early (3 days) and two late (3-4 months). Two of these patients underwent complete ablation of the AV junction and permanent pacemaker placement, whereas one is controlled with drug therapy. Therefore, AV nodal modification resulted in tachycardia control without antiarrhythmic drugs in six of nine (67%) and obviated the need for complete AV junctional ablation in seven of nine patients (78%). Elimination of AVNRT appears to result from either block in the retrograde fast pathway or modification of the antegrade slow pathway, such that AVNRT cannot be sustained. Additional findings suggest that an atrio-Hisian accessory connection may not be involved in AVNRT in some of these patients. Percutaneous catheter AV nodal modification appears to be a promising technique for treatment of refractory AVNRT and may obviate need for complete AV junctional ablation in a substantial number of patients with drug/pacemaker refractory AVNRT.

Catheter ablation of accessory pathways with a direct approach. Results in 35 patients

Thirty-five consecutive patients with an overt accessory pathway, all but two suffering from arrhythmia (atrial fibrillation, reciprocating tachycardia, or both), underwent attempted transcatheter ablation (fulguration) of their accessory pathway. Thirty-three patients had been treated with a mean of 2.3 +/- 1.4 antiarrhythmic drugs. A standard bipolar catheter was positioned on the internal surface of the right or left atrioventricular anulus with 1) a subclavian approach of the right cardiac cavities in 29 patients with right-sided accessory pathway (n = 27) or left posteroseptal accessory pathway (n = 2), 2) a patent foramen ovale in five patients (two with a left posterolateral accessory pathway and three with a left parietal accessory pathway), and a transseptal catheterism (one patient with a left parietal accessory pathway). Cathodic shocks (mean, 4.3 shocks/patient) with a mean cumulative energy of 690 J enabled the ablation (disappearance of both anterograde and retrograde conduction) of the accessory pathway in 32 patients with a follow-up ranging from 1 to 32 months (mean, 10 +/- 8 months). Two of the remaining three accessory pathways were impaired: one pathway became intermittent, the anterograde effective refractory period of the second pathway increased from 260 to 410 msec, and the third pathway was slightly impaired. This latter patient is the only one who still requires therapy, with a single antiarrhythmic drug. All others are free of arrhythmias and require no therapy. Not using coronary sinus catheterism inclusive of its os has led to only a few, benign side effects. Only one third-degree atrioventricular block occurred in a posteroseptal accessory pathway ablation. Three cases of patients with incessant reciprocating tachycardia involving a further successful ablation occurred at the beginning of our experience. The best area for ablation is, in our opinion, the recording site for the Kent-bundle activity (18 of 35 patients), but a meticulous mapping of the atrioventricular anulus during orthodromic reciprocating tachycardia makes ablation possible when the shortest ventriculoatrial time (V-A') can be recorded with reliability (mean, 85 +/- 18 msec). Such a procedure is an alternative to surgical ablation regardless of the location of the accessory pathway--not only posteroseptally.

Short- and long-term effects of transcatheter ablation of the coronary sinus by radiofrequency energy

Catheter ablation of left-sided atrioventricular accessory pathways through the coronary sinus by direct-current shock may be complicated by rupture and thrombosis of the coronary sinus and injury to the coronary arteries. This study examined short and long-term effects of radiofrequency catheter ablation of the coronary sinus in 20 closed-chest dogs to determine whether this technique is feasible for potential interruption of left-sided accessory pathways. Single-pulsed radiofrequency energy (750 kHz, 85-293 J) was delivered to three sites in the distal and middle coronary sinus between the distal (1) or the proximal electrodes (2 or 3) of a standard 6 French quadripolar catheter and a chest-wall patch electrode. Single-pulsed radiofrequency energy (78-293 J) was also applied to two sites near the ostium of the coronary sinus with the proximal (4) or the distal (1) electrode of the same catheter. Coronary artery and levophase coronary sinus angiograms obtained before and immediately after ablation, as well as before killing, showed intact vascular structures in all dogs. Right atrial, pulmonary arterial, and aortic pressures measured in three dogs did not change significantly at the time of energy delivery. No significant changes were found in atrioventricular nodal refractoriness and conduction. None of the dogs had significant rhythm disturbances during and after ablation as evaluated by ambulatory electrocardiographic monitoring and periodic rhythm strips at follow-up. Ten dogs were killed 1-7 days after ablation, three dogs were killed at 4 weeks, three dogs at 6 weeks, two dogs at 8 weeks, and two dogs at 12 weeks. Discrete lesions ranging in size from 3 x 3 to 8 x 10 mm2 in surface area and 0.5-4.5 mm in depth were found in the coronary sinus with most of the lesions extending to the left atrial and left ventricular myocardium. There was neither rupture of the coronary sinus nor occlusion of the coronary arteries. Mural thrombus was found in the coronary sinus on five acute lesions in two dogs, but none was noted on the chronic lesions, which was characterized by chronic granulation tissue and fibrosis. Two dogs in the study during chronic conditions had damage to branches of the underlying coronary artery that showed necrotizing arteritis and arterial sclerosis. Conduction system studies in four dogs showed some chronic inflammatory and fibrotic changes. Similar discrete lesions were found in situ in the coronary sinus of four postmortem human hearts with radiofrequency catheter ablation.(ABSTRACT TRUNCATED AT 400 WORDS)

Transvenous catheter ablation of extranodal accessory pathways

Twelve patients with an accessory pathway and recurrent symptomatic reciprocating tachycardia or atrial fibrillation, or both, underwent attempted transvenous catheter ablation of the accessory pathway. In one patient with a small right coronary artery, the pathway was along the right free wall. In 11 patients, the pathway was located at or within 15 mm of the coronary sinus os. For these patients, a quadripolar electrode catheter was placed in the coronary sinus and positioned, if possible, so that the proximal pair of electrodes straddled the pathway. For those patients with a pathway greater than 5 mm within the coronary sinus, the most proximal electrode was placed at the os. This proximal pair of electrodes was connected to the cathodal output of a defibrillator with an anterior chest wall patch serving as the current sink. Two shocks were then delivered for a cumulative energy of 500 to 600 J (stored energy). Among the eight patients with a pathway at or within 5 mm of the coronary sinus os, conduction over the pathway was abolished in five and modified in one. Among the four patients with a pathway farther from the os (10 to 15 mm) and along the right free wall, pathway conduction was modified only in two. Rupture of the coronary sinus did not occur in any patient. There were no serious complications. Minor damage surrounding the area of ablation was seen at the time of surgical division of the accessory pathway in two of five patients with unsuccessful ablation who subsequently underwent surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Developments, complications and limitations of catheter-mediated electrical ablation of posterior accessory atrioventricular pathways

Nineteen patients with posterior accessory pathways and disabling, refractory arrhythmias, underwent catheter ablation using standard defibrillator pulses at energy settings of 150 to 400 J. Accessory pathway ablation was successful in 13 of 19 (68%). Effective catheter ablation correlated with local ventriculoatrial (VA) intervals determined from the coronary sinus catheter at the site of earliest retrograde atrial activation during orthodromic reciprocating tachycardia. In 12 of the 13 successfully ablated patients, the local VA interval was less than 80 ms. In 4 of the 6 unsuccessfully treated patients, the local VA interval was greater than or equal to 80 ms, p less than 0.01. Transient abnormalities noted with the procedure included sinus bradycardia (3 patients), atrioventricular block (5), accelerated junctional rhythm (3), ectopic atrial tachycardia (2), myocardial depression (1), "ischemic" appearing T-wave inversions (10) and hemodynamically insignificant small pericardial effusions (5) Creatine kinase-MB increased from 3 +/- 2 U/liter to 26 +/- 18 U/liter (p less than 0.001), 4 to 8 hours after ablation. In addition, electrical shorts occurring during the ablation procedure in 2 patients were identified and corrected only with oscilloscopic monitoring of voltage and current waveforms. Significant adverse sequelae were seen in 4 patients. Three patients required sternotomy for control of cardiac tamponade secondary to a ruptured coronary sinus and 1 patient had a small posterior left ventricular infarction related to spasm of a right coronary artery extension branch. Coronary sinus rupture correlated with the ratio of catheter diameter to coronary sinus diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

High frequency alternating current ablation of an accessory pathway in humans

High frequency alternating current ablation of an accessory pathway was performed in a patient with incessant circus movement tachycardia using a right-sided, free wall accessory pathway. Antiarrhythmic drugs, antitachycardia pacing and transvenous catheter ablation using high energy direct current shocks could not control the supraventricular tachycardia. A 7F bipolar electrode catheter with an interelectrode distance of 1.2 cm was positioned at the site of earliest retrograde activation during circus movement tachycardia. At this area, two alternating current high frequency impulses were delivered with an energy output of 50 W through the distal tip of the bipolar catheter, while the patient was awake. After the first shock supraventricular tachycardia terminated and accessory pathway conduction was absent without altering anterograde conduction in the normal atrioventricular (AV) conduction system. No reports of pain or other complications were noted. In short-term follow-up of 5 months, the patient had been free of arrhythmias without antiarrhythmic medication. Thus, high frequency alternating current ablation was performed for the first time in the treatment of an arrhythmia incorporating an accessory pathway in a human. This technique may be an attractive alternative to the available transcatheter ablation techniques and to antitachycardia surgery.

Effects of catheter-delivered electrical discharges near the tricuspid anulus in dogs

The possibility of using electrical discharges to ablate right free wall accessory pathways by delivering a series of catheter shocks near the tricuspid anulus was assessed in a canine model. Before the shock, the amplitudes of the atrial and ventricular electrograms recorded from the distal electrodes were compared (A/V ratio), and the atrial pacing threshold was determined. To assess effects on function and arrhythmogenicity, right heart pressures were measured and programmed ventricular stimulation was performed before the shock and prior to sacrifice 7 to 10 days after the shock. Nine dogs received a total of 24 discharges at varying energies (50 to 400 J). Nonsustained ventricular tachycardia occurred with 13 shocks (62%) and transient atrioventricular block with 9 shocks (43%). There was no worsening in cardiac or valvular function as determined by right heart pressure measurements or right ventriculography. Programmed ventricular stimulation performed before the shocks and repeated before sacrifice failed to induce ventricular arrhythmias. The endocardial lesion produced by the shock was roughly circular and its area correlated with both the magnitude of the shock as well as the atrial pacing threshold. Transmural necrosis always occurred at the anulus when the A/V ratio was between 1.00 and 1.50 and preshock atrial pacing threshold suggested adequate wall contact (less than 1.5 mA). There was mild inflammation of the adventitia of the right coronary artery near two discharge sites (both 200 J) and inflammation of the media near one discharge site (400 J); no intimal involvement was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheter ablation of the atrioventricular junction and activity responsive pacing. Effect on refractory atrial fibrillation with hypertrophic cardiomyopathy

A 50-year-old man had chronic atrial fibrillation that was refractory to conventional therapy. He was intolerant of amiodarone, but successfully managed by transcatheter atrioventricular junction ablation. Activity-initiated rate-responsive ventricular pacing resulted in a fourfold greater increase in cardiac output with exercise compared to fixed rate pacing.

Anterograde conduction of a concealed accessory pathway after transvenous electric catheter ablation

An 18-year-old woman with a concealed right midseptal accessory pathway and refractory supraventricular tachycardia with a cycle length of 280-400 ms and a wide echo zone of 280-520 ms is reported. The transvenous electric catheter ablation with two shocks of 200 and 300 J, each on a separate occasion, was followed by anterograde and retrograde atrioventricular block. The patient received an implantable pacemaker (VVI). Four weeks later we observed a stable anterograde conduction of the pathway in spite of a persisting retrograde block. It is concluded that the site of unidirectional block in this patient is at the origin of the concealed accessory pathway in the ventricular septal muscle. The necrosis after ablation changed conduction conditions at the site of unidirectional block. Presently, the patient has been free of tachycardia for 19 months. This observation is of importance for the patient because another mechanism of tachycardia might be possible after ablation.

The current status of ablation of cardiac conduction tissue and ectopic myocardial foci by transvenous electrical discharges

Ablation of AV nodal/His bundle conduction by fulgurative electrical discharges has revolutionized the management of refractory supraventricular tachycardias of any type which requires AV conduction over the normal anatomical pathways. The success and safety of the technique is such that it has eclipsed operative ablation of AV conduction. It is increasingly clear that both anomalous pathway conduction and ventricular tachycardia foci may be destroyed by the technique of fulguration and preliminary evidence suggests that certain types of atrial foci may also be susceptible to this method of ablation. Development of purpose-designed electrodes for delivery of the discharges is likely to reduce maximum energy requirements and increase the safety of fulguration.

Clinical intracardiac electrophysiologic testing: technique, diagnostic indications, and therapeutic uses

Clinical cardiac electrophysiologic testing has evolved rapidly since 1968, when the technique was first described. In an electrophysiologic study, electrode catheters are positioned within the heart to record electrical activity from the atrium, atrioventricular conduction tissue, and ventricle. Programmed stimulation is then performed, which involves pacing of the atrium or ventricle and introducing critically timed premature stimuli during sinus rhythm or paced rhythm. The use of programmed stimulation in conjunction with intracardiac recordings in electrophysiologic studies has facilitated the diagnosis of mechanisms of arrhythmias and the assessment of therapy. Electrophysiologic testing is useful in selected patients with sinus node dysfunction, conduction system disorders, supraventricular tachycardia, ventricular tachycardia, or ventricular fibrillation and in survivors of out-of-hospital cardiac arrest and patients with symptomatic but unsubstantiated rhythm disturbances. Therapeutic approaches that can be assessed by electrophysiologic testing include serial drug testing to determine the effectiveness of antiarrhythmic agents, antitachycardia pacing, the implantable defibrillator, transcatheter ablation, and electrophysiologically guided surgical procedures. In this review, we discuss the methods of electrophysiologic testing, its clinical applications in diagnosing the various cardiac rhythm disturbances, and its use in assessing various therapeutic modalities.

Transvenous catheter ablation of the His bundle in ventricular tachycardia

The usefulness of transvenous catheter ablation of the His bundle in three patients with recurrent ventricular tachycardia (VT), in which the initiating mechanism was recognized during a rapid atrial rhythm, is reported. Tachycardia was refractory to conventional treatment and required transthoracic direct-current shocks in all patients. In patient No. 1 double tachycardia (atrial flutter and VT) was documented and VT was easily induced by rapid atrial pacing. In patients Nos. 2 and 3 initiation of VT during junctional reciprocating and atrial tachycardia, respectively, was observed. Interruption of the His bundle was performed by means of fulguration. Stable atrioventricular (AV) block was observed in patient No. 1 after the ablative procedure; patient No. 2 showed anterograde conduction over a posterior septal accessory pathway with no evidence of conduction over the normal conduction system in both the anterograde and retrograde directions. In patient No. 3, transient AV block was observed; AV conduction resumed 2 days later and the cardiac rhythm showed persistent ectopic atrial tachycardia with second-degree AV block. Patients Nos. 1 and 2 underwent pacemaker implantation, but patient No. 2 was not pacemaker dependent. After the procedure, VT no longer occurred in any of the patients (follow-up: 2 years, 5 months, and 6 months).

Catheter-mediated electrical ablation of the posterior septum via the coronary sinus: electrophysiologic and histologic observations in dogs

In a series of 12 dogs, the electrophysiologic and histologic effects of a single damped sine-wave shock delivered via standard electrocatheters to the region of the coronary sinus orifice were investigated. Six dogs received 200 J and six received 360 J of stored energy. The shock was delivered to two consecutive proximal poles of a standard quadripolar catheter positioned at the coronary sinus orifice and connected to the positive output (anode) of a defibrillator. A disc electrode positioned on the anterior chest wall served as the cathode (negative pole). During the shock, voltage and current were recorded. Electrophysiologic testing was done before and 4 weeks after the shock. At 4 weeks, animals were killed and serial sections of the atrioventricular groove and conduction system were performed. No significant long-term change in atrioventricular conduction, spontaneous or induced atrial or ventricular arrhythmias was observed. However, transient atrioventricular block was seen in five and idioventricular rhythms in six animals in the short term. No persistent electrocardiographic changes were observed, and no sudden deaths occurred. Microscopically, transmural injury at the anulus proper or basilar ventricular epicardium was inconstant and infrequent. However, transmural atrial injury at the level of the coronary sinus was produced over a 10 +/- 5 mm length with the 200 J shock and a 21 +/- 6 mm length with the 360 J shock. Neither coronary artery injury nor damage to the conduction system was seen and cardiac tamponade did not occur. However, localized intramural atrial rupture of the coronary sinus wall (on the endocardial aspect only) was observed in each dog, consistent with barotrauma. With the present technique, atrial injury potentially capable of blocking the effects of accessory pathway conduction could be produced without other electrophysiologic alterations or complications. Injury to the anulus proper (and therefore to any accessory pathway per se) is probably unlikely. Barotrauma may play a significant role in the type of injury observed in this study.

Evaluation of a percutaneous catheter technique for ablation of ventricular tachycardia in a canine model

Catheter ablation of arrhythmias is a promising new technique. The consequence of high-energy discharges in the right ventricle were investigated in a canine model of inducible ventricular tachycardia. Seventeen dogs were studied. Four served as controls while 13 underwent thoracotomy with right coronary artery ligation. Three animals died suddenly postoperatively. Programmed stimulation was performed 4 days later using a pervenous right ventricular electrode catheter. No control dog had inducible ventricular tachycardia. Eight of the experimental animals had inducible ventricular tachycardia and underwent catheter mapping. The earliest endocardial site during tachycardia was located in four dogs with monomorphic ventricular tachycardia. These sites received one or more 300 J transcatheter stored charges from a defibrillator, and at least temporary ablation was accomplished in each case. Five animals had inducible polymorphic ventricular tachycardia which could not be mapped. The endocardial electrogram amplitude decreased 55 +/- 7% (p less than 0.001) and the pacing threshold increased from 0.7 +/- 0.1 mA to 7.9 +/- 1.7 mA (p less than 0.001) after the shocks. Five of the discharges caused ventricular tachycardia or fibrillation. Autopsy revealed discrete transmural wedge-shaped necrosis without perforation. Thus when monomorphic tachycardia was induced, mapping and ablation were feasible. Transcatheter 300 J discharges produced only localized damage but had a propensity to initiate ventricular arrhythmias.

Efficacy and safety of transcatheter ablation of posteroseptal accessory pathways

Eight patients with a posteroseptal accessory pathway and symptomatic atrial fibrillation and/or orthodromic reciprocating tachycardia underwent attempted transcatheter ablation of the accessory pathway. A quadripolar electrode catheter was positioned within the coronary sinus such that the proximal pair of electrodes straddled the os. This proximal pair of electrodes was made electrically common and connected to the cathodal output of a defibrillator. A patch electrode placed over the midthoracic spine was connected to the anodal sink of the defibrillator. Two to three transcatheter shocks were delivered, with a cumulative energy of 600 to 900 J. Immediately after the shocks were delivered, retrograde accessory pathway conduction was absent in each patient. Anterograde conduction through the posteroseptal accessory pathway was absent in six patients. In one patient, retrograde accessory pathway conduction was absent and anterograde conduction was present but was slower than at baseline. In this patient, orthodromic tachycardia was no longer inducible and the ventricular rate during induced atrial fibrillation was 150 beats/min, compared with 220 beats/min before the attempted ablation. He has remained asymptomatic without antiarrhythmic drug therapy for 18 months. In one patient, the transcatheter shocks had no long-term effect on accessory pathway conduction. The shocks delivered at the os of the coronary sinus were well tolerated.(ABSTRACT TRUNCATED AT 250 WORDS)

Right coronary spasm complicating electrode catheter ablation of a right lateral accessory pathway

Severe focal right coronary artery spasm, demonstrated on angiography, occurred in a 12 year old girl undergoing attempted electrode catheter ablation of a right atrial-right ventricular free wall accessory pathway.

Treatment of tachycardias associated with the Wolff-Parkinson-White syndrome by transvenous electrical ablation of accessory pathways

Three patients with tachycardias associated with the Wolff-Parkinson-White syndrome had failed to respond to antiarrhythmic drugs and underwent transvenous ablation of accessory pathways. Intracardiac studies located the site of accessory pathway to the septum in two patients and mid-posterobasal left atrioventricular junction in one. Ablation was performed by positioning an electrode lead as close as possible to the accessory tract and delivering shocks of 50 to 100J using a conventional defibrillator. In all patients the accessory pathway was abolished after the first three shocks. In two patients followed for four and nine months there was no recurrence of tachycardia or pre-excitation. The other patient developed pre-excitation again three weeks later and repeat ablation was performed. This patient has been followed for six months with no evidence of a recurrence of pre-excitation. This method may provide a valuable alternative to pacemaker and surgical treatment in selected patients with drug resistant arrhythmias associated with accessory atrioventricular connexions.

Attempted nonsurgical electrical ablation of accessory pathways via the coronary sinus in the Wolff-Parkinson-White syndrome

Previous canine experiments suggested that transvenous catheters placed in the coronary sinus could be used to deliver limited energy shocks, resulting in fibrosis in the atrial wall and coronary sulcus with sparing of the coronary artery. From the distribution of the fibrosis, it appeared that this approach could be used for attempted ablation of accessory pathways in patients with the Wolff-Parkinson-White syndrome. Eight patients with symptomatic Wolff-Parkinson-White syndrome underwent electrophysiologic testing with attempted ablation of 10 accessory pathways. Shocks were limited to 40 to 80 J, except in one patient who received shocks of 100 and 150 J. From 2 to 26 shocks were given to each accessory pathway. All the accessory pathways were blocked completely immediately after the shocks. Subsequently, evidence of accessory pathway conduction recurred in each patient. Three had early promise of long-term improvement after the procedure, with prolongation of the refractory periods of the accessory pathways during the remainder of the initial hospitalization. Several weeks later, however, there was evidence of return toward original values in two of these. Another patient who appeared not to benefit during her initial hospitalization returned 7 weeks later with very depressed accessory pathway conduction, possibly due to developing fibrosis. The only significant complication occurred in the patient receiving shocks of 100 and 150 J; he had apparent rupture of the coronary sinus requiring pericardial drainage. In two patients in whom nonsurgical ablation was not successful, intraoperative mapping showed that the accessory pathway was located in an area of fibrosis at the site of the attempted ablation. In summary, nonsurgical electrical ablation of accessory pathways via the coronary sinus may be successful using limited energy levels in a few patients. The procedure remains experimental, and widespread application must await more effective means of delivering the shocks.

Catheter ablation of atrioventricular conduction

35 patients with refractory supraventricular arrhythmias were treated in three centres by high-energy shocks delivered to the atrioventricular conduction system from a conventional transvenous pacing catheter. After a mean interval of ten months, 26 patients (74%) had persistent complete heart block, 2 (6%) had intermittent complete heart block, and 3(9%) had first-degree heart block. 3 patients continued to have conducted atrial fibrillation, but with slower ventricular rates than previously, and 1 had normalisation of dual atrio-His conduction. In 1 patient a septal accessory pathway was ablated. 30 patients (86%) are completely symptom-free without additional therapy. There were no important long-term complications. Transvenous ablation of atrioventricular conduction is a safe and effective technique for treating a wide range of refractory atrial and junctional arrhythmias.