Surgical treatment of accessory atrioventricular pathways and symptomatic tachycardia in children and young adults

Beyond Fontan conversion: Surgical therapy of arrhythmias including patients with associated complex congenital heart disease

BACKGROUND

Arrhythmia operations may be extended to patients with failed ablation procedures or associated structural defects requiring surgical intervention. The purpose of this study is to review our experience with arrhythmia operations in 29 patients who did not have Fontan conversions after the introduction of catheter ablation.

METHODS

Between July 1992 and January 2002, 29 patients had operations for refractory atrial (n = 24) or ventricular (n = 5) arrhythmias. Mechanisms of arrhythmia included atrial reentry (n = 11), atrial fibrillation (n = 5), automatic atrial (n = 3), accessory connections (n = 6), atrioventricular nodal reentry (n = 2), and ventricular tachycardia (n = 5). Median age at operation was 12.3 years (range, 6 days to 45 years). Two patients had structurally normal hearts; the remaining 27 patients underwent concomitant repair of structural heart disease, including atrioventricular valve replacement or repair (n = 8), anatomy-specific repair of Ebstein's anomaly (n = 4), tetralogy of Fallot repair or revision (n = 4), atrial septal defect closure (n = 3), ventricular septal defect repair (n = 2), Mustard takedown with arterial switch (n = 2), initial Fontan (n = 2), right ventricle-to-pulmonary artery conduit revision (n = 2), Norwood procedure (n = 1), 1 ventricular repair for Uhl's anomaly (n = 1), Mustard baffle revision (n = 1), pulmonary valve replacement with aneurysm resection (n = 1), and aortic valve replacement with complex repair (n = 1).

RESULTS

No patient developed heart block, and the surgical mortality rate was 7%. One patient died after Mustard takedown and arterial switch operation, and 1 neonate died after repair of severe Ebstein's anomaly. There was one late death after arterial switch conversion at another institution. Recurrent clinical supraventricular tachycardia was present in 2 patients (2 of 27, 7.4%) and 2 patients had new-onset tachycardias with different underlying mechanisms of arrhythmia at late follow-up (median follow-up 47 months).

CONCLUSIONS

Successful surgical therapy of arrhythmias can be performed safely at the time of repair of complex congenital heart disease or in patients with failed catheter ablation procedures. Early consideration for single-stage therapy of arrhythmia and structural heart disease is indicated.

Radiofrequency ablation for supraventricular and ventricular tachycardia in young patients

Radiofrequency ablation therapy was conducted in 86 consecutive children and young patients with a mean age of 14 +/- 3 years (range = 3-18). Fifty-two patients had Wolff-Parkinson-White syndrome, one had re-entry tachycardia incorporating a nodoventricular fiber, 22 had atrioventricular node re-entry tachycardia, two had atrial tachycardia and nine had idiopathic ventricular tachycardia. Radiofrequency ablation was successful in 50 of the 52 patients (96%) with Wolff-Parkinson-White syndrome and the one with nodoventricular fiber. Radiofrequency modification of the atrioventricular node using the inferior approach was successful in eliminating atrioventricular node re-entry tachycardia in 20 of the 22 patients (91%). Radiofrequency ablation in the two patients with atrial tachycardia was unsuccessful. Of the nine patients with idiopathic ventricular tachycardia, eight from the left ventricle and one from the right ventricular outflow tract, eight were successfully ablated (88%). Follow-up over a period ranging from 1 to 46 months (21 +/- 13) revealed a recurrence of tachycardia in seven patients; a late electrophysiological study in 38 patients revealed the induction of tachycardia in 11 patients (seven with accessory pathway-mediated tachycardia, three with atrioventricular node re-entry tachycardia and one with idiopathic ventricular tachycardia). All 11 patients were successfully ablated by a second trial. In conclusion, radiofrequency ablation therapy is effective and safe in pediatric patients with supraventricular and ventricular tachycardia and should be considered as the therapy of choice in this group of patients.

Surgical treatment of cardiac dysrhythmias in infants and children

A variety of cardiac rhythm disturbances that occur in infants and children may be refractory to medical or catheter ablation therapy, or both, and thus require surgical ablation. These dysrhythmias include Wolff-Parkinson-White syndrome, atrial automatic tachycardia, atrioventricular node reentry tachycardia, and ventricular tachycardia. The surgical technique originally used in adults may be equally well applied in infants and small children. In the interval from July 1, 1984, through December 31, 1993, a total of 130 infants and children (< or = 16 years old) underwent surgical treatment for various forms of dysrhythmias (96 with Wolff-Parkinson-White syndrome, 8 with atrioventricular node reentry, 11 with atrial automatic tachycardia, and 15 with ventricular tachycardia). The success rate for completely abolishing these arrhythmias has been 92% for the Wolff-Parkinson-White syndrome, 100% for atrioventricular node reentry, and 64% for atrial automatic tachycardia. In infants younger than 2 years, the success rate for the surgical treatment of ventricular tachycardia is 100%, but the long-term success in older children has been poor. One patient sustained a severe intraoperative neurologic event that resulted in her death (operative mortality, 0.7%). Ventricular function returned to normal in all patients in whom it was abnormal preoperatively. These data suggest that the surgical treatment of these dysrhythmias remains a viable alternative in those patients whose dysrhythmias are refractory to medical therapy, those in whom catheter ablation has been unsuccessful, or those in whom both situations apply.

Surgical treatment of Wolff-Parkinson-White syndrome in infants and children

Electrophysiologic features and surgical results were examined in 55 pediatric patients who underwent surgical accessory pathway division for Wolff-Parkinson-White syndrome. There were 31 male and 24 female patients ranging in age from 4 months to 15 years (mean age, 9.8 +/- 4.2 years; 25 patients were less than 10 years old; 4 patients were less than 12 months). Eleven of these patients had associated congenital heart disease and underwent concomitant surgical procedures to treat those conditions. Preoperative effective refractory period of antegrade accessory pathways, the right atrium, atrioventricular node, and cycle length during reentrant tachycardia were shorter in pediatric patients than in adult patients. Antegrade accessory pathways showed right predominance more frequently in the pediatric group than in the adult group. Surgical techniques included an endocardial approach (an epicardial approach was used in 1 patient) and concomitant operation for combined heart disease. The early mortality rate was 3.6%, whereas no late deaths occurred during the follow-up period of 96.8 +/- 54.9 months (maximum follow-up, 205 months). The absolute cure rate was 92%. There were no significant differences in early and late mortality between pediatric and adult patients. Surgical treatment of the Wolff-Parkinson-White syndrome in pediatric patients is as safe and effective as in adults. Considering the potential complications from prolonged fluoroscopic exposure during catheter ablation, surgical division of accessory pathways in children is a promising modality for the treatment of Wolff-Parkinson-White syndrome in selected cases.

Catheter ablation using radiofrequency or low-energy direct current in pediatric patients with the Wolff-Parkinson-White syndrome

Percutaneous ablation of accessory pathways was performed in 22 consecutive children and adolescents (9 boys and 13 girls, age range 8 to 18 years). Low-energy direct current (DC) was used exclusively in the first 6 patients, whereas ablation was performed with radiofrequency energy in the following 16. Accessory pathways were located in the left free wall in 15 patients, were posteroseptal in 3, were in the right free wall in 3 and were anteroseptal in 1. A concealed accessory pathway was present in 7 patients (32%). There was no significant difference in clinical or electrophysiologic variables between both groups. Catheter ablation was successful in the initial 6 patients using low-energy DC, as compared with 13 of 16 patients using radiofrequency ablation. Low-energy DC was successful as a backup power source in all 3 patients who had unsuccessful radiofrequency ablation. There was no complication. The median procedural and fluoroscopic times for successful ablation were 2.5 hours and 49 minutes, respectively (p = NS between both power sources). Accessory pathway conduction recurred in 2 patients (33%) who had low-energy DC as compared with 1 (6%) who had radiofrequency ablation (p = NS). These 3 patients had successful reablation of their accessory pathways. In children and adolescents with accessory pathways, both new power sources compare favorably, with an overall success rate of ablation of 100% (22 of 22 patients). Radiofrequency ablation should be used initially because it does not require general anesthesia and is associated with a lower rate of recurrence of accessory pathway conduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical management of dysrhythmias in infants and small children

Surgery for cardiac dysrhythmias is infrequently reported in infants and children as compared with adults. This report reviews 55 infants and small children (age, less than or equal to 5 years) operated on during the interval July 1, 1984 to December 31, 1991 for Wolff-Parkinson-White Syndrome (41), atrioventricular node reentry (two), atrial automatic tachycardia (two), and ventricular tachycardia (nine). Ages ranged from 3 weeks to 71 (mean, 29) months. Associated congenital heart defects were present in five (10%). Indications for surgery included failure of medical therapy, life-threatening dysrhythmias, and more recently, failure of catheter ablation. There were no hospital or late deaths. One patient sustained perioperative central nervous system injury. Surgery was successful in 52 of 55 (94.5%) (Wolff-Parkinson-White, 38/41 (93%); atrioventricular node reentry, 2/2 (100%); atrial automatic tachycardia, 3/3 (100%); ventricular tachycardia, 9/9 (100%). Ventricular function returned to normal in all 12 patients in whom it was abnormal before operation. Thus, surgical ablation is highly successful in the management of various forms of refractory or life-threatening dysrhythmias in infants and small children. Catheter ablation techniques require significant fluoroscopic time, are more difficult in infants, and as yet do not have adequate long-term follow-up. Accordingly, surgery may continue to play a role in this particular group of patients.

Radiofrequency catheter ablation of accessory atrioventricular connections in 250 patients. Abbreviated therapeutic approach to Wolff-Parkinson-White syndrome

BACKGROUND

The purpose of this study was to report the results and complications of radiofrequency catheter ablation of accessory atrioventricular (AV) connections by using an abbreviated approach aimed at minimizing the duration of the procedure.

METHODS AND RESULTS

Two hundred fifty consecutive patients with the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardia involving a concealed accessory AV connection underwent catheter ablation with the use of radiofrequency current. In 179 of the 250 patients, catheter ablation was performed at the time of an initial electrophysiology test. Two hundred thirty-five patients had one accessory AV connection and 15 patients had two or more. One hundred eighty-three accessory AV connections were manifest and 84 were concealed. One hundred sixty-one were were located in the free wall of the left ventricle, 47 were in the right free wall, 44 were posteroseptal, 10 were anteroseptal, and five were intermediate test, and the ablation procedure was recorded for each patient, as was the total duration of fluoroscopy. A follow-up electrophysiology test was performed 2-3 months after the ablation procedure. Ninety-four percent of patients had all accessory AV connections successfully ablated and remained free of symptomatic tachycardia during a mean follow-up of 10 +/- 4 months. Two hundred nineteen patients (88%) had all accessory AV connections ablated during the initial attempt at catheter ablation. Mean duration of the entire procedure was 134 +/- 75 minutes. Procedure duration was longest in patients with multiple accessory AV connections, shortest in patients with intermediate septal accessory AV connections, and similar in all other locations. A nonfatal complication occurred in nine patients (4%).

CONCLUSIONS

The results of this study indicate that catheter ablation of accessory AV connections with radiofrequency current can be performed safely and expeditiously in a majority of patients and confirm in a large series the feasibility of catheter ablation at the time of an initial diagnostic electrophysiology test. This abbreviated therapeutic approach avoids the need for electropharmacological testing, long-term antiarrhythmic drug therapy, and surgical therapy in the majority of patients with the Wolff-Parkinson-White syndrome or with symptomatic tachycardias involving accessory AV connections.

Selective surgical approach for atrioventricular reentrant tachycardia

From September 1986 through September 1990, 60 operations were performed in 55 patients (32 male and 23 female; age, 1 to 76 years) for ablation of accessory pathways of atrioventricular reentrant tachycardia; 6 patients had additional cardiac procedures. Between September 1986 and August 1988 the initial surgical approach was exclusively epicardial with adjuvant cryoablation (EPI) in 23 patients (group 1) for a left free wall (LFW) pathway in 11, right free wall (RFW) in 3, posteroseptal (PS) in 7, and anteroseptal in 2. During September 1988 through September 1990, 32 patients (group 2) had the initial surgical approach tailored to the location of the mapped accessory pathway: endocardial approach (ENDO) for LFW in 17 and for juxtanodal pathway in 2, EPI for RFW in 3 and for PS in 9, and combined ENDO and EPI for AS in 1. There was no early or late death in either group. In group 1, 2 patients with LFW pathway had development of recurrent preexcitation in the same compartment requiring ENDO reoperation 10 and 11 months later, 1 with anteroseptal pathway needed immediate ENDO and EPI reoperation, and another with LFW, who required pericardial patch repair of a left atrial tear, had a thromboembolic stroke 2 days later. No serious complications occurred in group 2, but 2 patients with PS required reoperation before discharge for a second accessory pathway in another compartment (1 RFW and 1 LFW). Additionally, 4 patients (2 in each group) had from the beginning ablation of two pathways in different compartments. On complete late follow-up (mean, 28 months) all patients are back to preoperative levels of activity and are free of preexcitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Supraventricular tachycardia: diagnosis and current acute management

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Daily bedside electrophysiological testing following surgery for the WPW syndrome

A simple technique is described that allows daily bedside evaluation of the results of surgery for the Wolff-Parkinson-White (WPW) syndrome, using standard postoperative myocardial wires, a single-channel ECG machine, and a temporary pacer capable of rapid stimulation. Rate incremental atrial and ventricular ramp pacing was performed daily in 40 postoperative WPW patients. This technique, together with underdrive pacing in some individuals permits quick assessment of anterograde and retrograde conduction. Two surgical failures were identified in early postoperative days, and promptly returned to the operating room for successful reoperation. No additional failures were identified at formal predischarge electrophysiological testing or following discharge. The technique permits reassurance on a daily basis to apparent successes and early identification in the event of failure, permitting prompt intervention.

Surgical treatment of dysrhythmias in infants and children

The recognition of medically refractory dysrhythmias in children has necessitated the use of more invasive nonpharmacologic therapies. The role of ablative surgery in the management of pediatric rhythm disturbances is presented.

Overview of the clinical electrophysiology study

Clinical electrophysiology testing is now a standard, useful technique for assessing patients with bradyarrhythmias or tachyarrhythmias. The technique requires specialized training and equipment. The recording equipment and program stimulator have evolved to sophisticated devices allowing accurate reproduction of intracardiac electrograms and timing of programmed extrastimuli. Electrophysiologic studies are useful for determining the mechanisms of a tachycardia or bradycardia and identifying the most appropriate therapy, whether it be pacing, antiarrhythmic medications, transvenous ablation, or electrosurgery.

Management strategies for surgical treatment of dysrhythmias in infants and children

To elucidate the role of surgery in the management of refractory pediatric dysrhythmias, the investigators' 1987 experience with this therapy was reviewed. Sixteen patients (8 male, 8 female) had surgery. Age ranged from 3 months to 21 years (mean 7.7 years) with 2 being younger than 1 year of age. Eight patients had Wolff-Parkinson-White syndrome with supraventricular tachycardia (SVT), 6 had SVT alone and 2 had ventricular tachycardia. Patient symptoms fell into 3 distinct categories. Nine patients had frequent non-life-threatening tachycardia episodes despite aggressive medical management, 4 patients had life-threatening symptoms either related to frequent tachycardia episodes or due to side effects of drugs and 3 patients had minimal tachycardia symptoms but were judged to be at risk for sudden death. The mechanisms of the tachycardias included reentrant SVT using an accessory atrioventricular connection in 9, the permanent form of junctional reciprocating tachycardia in 2, atrioventricular node reentrant SVT in 2, atrial ectopic focus in 1 and ventricular ectopic foci in 2. Ablation techniques involved either surgical dissection or cryoablation of the arrhythmogenic substrates. There was no surgical mortality and follow-up shows 15 of 16 patients to have had no recurrence of symptomatic tachycardia without any therapy. Based on this experience, management strategies for surgical control of recalcitrant pediatric dysrhythmias are proposed. Surgery for infant dysrhythmias should be performed only for life-threatening symptoms. Beyond the first year of life, after failing 2 medications, surgical options for SVT should be considered. For patients with ventricular tachycardia, aggressive medical management with class II, IC and III agents should be attempted before surgical therapy.

Nonpharmacologic treatment of supraventricular tachycardia

During the last 2 decades, more than 1,000 patients have undergone surgical division of an accessory pathway; many refinements in epicardial mapping and surgical techniques have been made. In institutions where the procedure is routinely performed, the rate of successful accessory pathway interruption now approaches 98%. Concomitant risk of complete heart block among patients with posteroseptal pathways has declined to less than 5%. Among patients with other organic heart disease, myocardial preservation techniques result in mortality rates within 1 to 2%; among those with significant cardiac abnormalities, the mortality rate is 4 to 6%. Two techniques are generally used to ablate an accessory pathway: the endocardial and the epicardial. The aim of both approaches is to identify the site of the accessory pathway and disarticulate the atrioventricular groove or expose and ablate the atrioventricular junction to interrupt accessory pathway conduction. Although each technique has its advantages, the choice of technique is far less important than the skill of the surgeon and clinical electrophysiologist performing the procedure. Newer surgical techniques include application of external epicardial shocks in the area of the accessory pathway and use of a cryosurgical probe in the sinus to ablate accessory pathways. Whereas our current thought is that surgery should be limited to those adults who fail to respond to pharmacologic therapy, advances in atrial endocardial and epicardial mapping, as well as surgical techniques, may expand the role of surgery in the treatment of ectopic atrial tachycardia.

Surgical management of children and young adults with the Wolff-Parkinson-White syndrome

The Wolff-Parkinson-White syndrome, as originally described, includes palpitations, tachycardia, and an abnormal electrocardiogram (short PR interval and wide QRS complex). The clinical manifestations are dependent upon a reentrant tachycardia supported by an accessory connection bridging the atrioventricular junction and frequently appear during the first two decades of life. Palpitations are the usual symptoms; less frequently, severe symptoms, such as syncope and sudden death, may result from very rapid atrioventricular conduction across the accessory connection during atrial fibrillation. We report the surgical management of 30 young patients with this syndrome, including 6 with life-threatening tachycardia. Surgical interruption of the accessory connection(s) was curative in 90% (27/30) of the patients; life-threatening symptoms were eliminated in the other three. Based on the limited knowledge of the natural history of the Wolff-Parkinson-White syndrome, the individual patient symptoms, and the electrophysiologic properties of each patient's accessory pathway(s), an algorithm is presented outlining the treatment options. This experience strongly suggests that surgical treatment of the Wolff-Parkinson-White syndrome is safe, effective, and possibly the preferred treatment for this disorder in selected young symptomatic patients.

Cryosurgical modification of atrioventricular conduction for treatment of atrioventricular node reentrant tachycardia

Cryosurgical modification of atrioventricular (AV) node conduction was performed in five patients with AV node reentrant tachycardia that used dual AV nodal pathways and was refractory to drug therapy. The procedure alleviated the tachycardia in all patients without the development of complete heart block and without any associated surgical morbidity or mortality. These results suggest that cryosurgical modification of AV node conduction is a promising and potentially curative method of treating AV node reentrant tachycardia.

Value of the resting 12 lead electrocardiogram and vectorcardiogram for locating the accessory pathway in patients with the Wolff-Parkinson-White syndrome

The resting 12 lead electrocardiogram and vectocardiogram were reviewed in 47 patients with the Wolff-Parkinson-White syndrome (a) who had pre-excitation on the resting 12 lead electrocardiogram, (b) who had a single anterograde conducting accessory pathway assessed and located during preoperative electrophysiological study and during epicardial mapping at operation, and (c) in whom surgical division of the accessory pathway resulted in loss of pre-excitation. The site of the accessory pathway established during operation was compared with that established by evaluating the polarity of the delta wave and QRS complex on the resting 12 lead electrocardiogram. The electrocardiogram was assessed by the Rosenbaum criteria (Wolff-Parkinson-White type A, left-sided pathway; or type B, right-sided pathway), the Gallagher criteria (atrial pacing resulting in maximal pre-excitation), and the World Health Organisation criteria (a composite of previous studies). The Gallagher and World Health Organisation criteria were derived from patients demonstrating maximal pre-excitation that often required atrial pacing. The present study was designed to determine whether these criteria could be accurately applied to the resting 12 lead electrocardiogram on which the degree of pre-excitation was variable. The Rosenbaum criteria correctly identified a left sided accessory pathway in 26 of 34 patients and a right-sided accessory pathway in nine of 13 patients. The Gallagher and World Health Organisation criteria correctly identified the location in only 15 (32%) of the 47 patients. The resting vectorcardiogram was inaccurate for locating the accessory pathway. Although published criteria are useful for identifying the site of the accessory pathway from an electrocardiogram obtained when rapid atrial pacing is being used to achieve maximal pre-excitation, they are not suitable for identifying the exact site of an accessory pathway from the resting 12 lead electrocardiogram.

Surgical treatment of pediatric cardiac arrhythmia

The combination of improved diagnostic techniques, new and potent antiarrhythmia agents, and progress in antiarrhythmia surgical procedures has resulted in successful management of complex cardiac arrhythmia in children. The kinds of arrhythmia that can be considered for possible surgical intervention share several features. Each produces symptoms and usually is hemodynamically compromising. Each requires extensive preoperative and intraoperative electrophysiologic evaluation to establish the mechanism, response to drugs, and suitability for surgery. Although reports of surgical arrhythmia treatment have been limited in children, with increasing success the indications for such treatment may become less stringent. Our recommendations are shown in the Table. In general, patients intolerant of or unresponsive to medical treatment for symptomatic arrhythmia (tachycardia or bradycardia), should be considered candidates for surgical antiarrhythmia procedures. These patients should be referred for testing to cardiac centers staffed by pediatric cardiac electrophysiologists and surgeons experienced in arrhythmia diagnosis and ablation. Careful evaluation can identify those patients in whom surgical approaches are most appropriate. At present, surgical operations for selected, serious pediatric cardiac arrhythmias offer definitive and possibly curative treatment, and may be preferable to inadequate, poorly tolerated, or long-term medical therapy.

Long-term follow-up after surgical correction of Wolff-Parkinson-White syndrome

The long-term efficacy of surgical correction of Wolff-Parkinson-White syndrome was evaluated in 45 consecutive patients. Before surgery, 42 patients had reciprocating tachycardia and 12 had atrial fibrillation. The principal operative procedure was endocardial incision in 42 patients, endocardial cryoablation in 2 patients and epicardial cryoablation without dissection of the atrioventricular (AV) fat pad in 1 patient. Two patients had perioperative complications. One patient had bleeding that necessitated reoperation, and one had a right cerebral stroke with subsequent clearing of neurologic deficit. At postoperative electrophysiologic study, only the patient who underwent epicardial cryoablation had conduction over an accessory connection. Two others had intermittent delta waves in the early postoperative period but no accessory connection conduction at electrophysiologic study. During a mean follow-up of 3.1 years, the patient with ineffective cryoablation had recurrent orthodromic tachycardia, and one other patient had late recurrence of delta waves without arrhythmias. Four other patients had frequent palpitation, which was caused by premature ventricular complexes in three and sinus tachycardia in one. Seventeen patients had occasional "skipped beats" without recurrence of tachyarrhythmias. Twelve of 13 patients whose arrhythmias limited employment before surgery returned to work after surgery. By actuarial analysis at 1, 2 and 3 years, all patients were alive and 98% were free from tachyarrhythmias. Surgical correction of Wolff-Parkinson-White syndrome provides excellent long-term results with low morbidity. Patients who are disabled by arrhythmias return to work after successful surgery. Delta waves may persist or recur without return of arrhythmias. Minor postoperative episodes of palpitation are common and do not correlate with tachyarrhythmias.

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.