Short-term effect of atrial fibrillation on atrial contractile function in humans.

BACKGROUND: Conversion of chronic atrial fibrillation (AF) is associated with atrial stunning, but the short-term effect of a brief episode of AF on left atrial appendage (LAA) emptying velocity is unknown. The purpose of this study was to determine whether a short episode of AF affects left atrial function and whether verapamil modifies this effect. METHODS AND RESULTS: The subjects of this study were 19 patients without structural heart disease undergoing an electrophysiology procedure. In 13 patients, LAA emptying velocity was measured by transesophageal echocardiography in the setting of pharmacological autonomic blockade before, during, and after a short episode of AF. During sinus rhythm, the baseline LAA emptying velocity was measured 5 times and averaged. AF was then induced by rapid right atrial pacing. After either spontaneous or electrical conversion, LAA emptying velocity was measured immediately on resumption of sinus rhythm and every minute thereafter. The mean duration of AF was 15.3+/-3.8 minutes. The mean baseline emptying velocity was 70+/-20 cm/s. The first post-AF emptying velocity was 63+/-20 cm/s (P=0.02 versus baseline emptying velocity). The post-AF emptying velocity returned to the baseline emptying velocity value after 3.0 minutes. The mean percent reduction in post-AF emptying velocity was 9.7+/-21% (range, 15% increase to 56% decrease). A second group of 6 patients were pretreated with verapamil (0.1-mg/kg IV bolus followed by an infusion of 0.005 mg. kg-1. min-1). In these patients, the first post-AF emptying velocity, 58+/-14 cm/s, was not significantly different from the pre-AF emptying velocity, 60+/-13 cm/s (P=0.08). CONCLUSIONS: In humans, several minutes of AF may be sufficient to induce atrial contractile dysfunction after cardioversion. When atrial contractile dysfunction occurs, there is recovery of AF within several minutes. AF-induced contractile dysfunction is attenuated by verapamil and may be at least partially mediated by cellular calcium overload.

Reasons for prolonged or failed attempts at radiofrequency catheter ablation of accessory pathways.

OBJECTIVES: The purpose of this study was to categorize the reasons for a prolonged or failed procedure in a series of patients undergoing catheter ablation of an accessory pathway. BACKGROUND: Radiofrequency ablation of accessory pathways at times requires a lengthy procedure or a second ablation session, or both, and not prior studies have systematically investigated the reasons for this. METHODS: In a consecutive series of 619 patients undergoing catheter ablation of an accessory pathway, the mean ablation time +/- SD was 68 +/- 64 min. The subjects of this study were 14 patients who had an ablation time >2 SD greater than the mean (>196 min) and 51 patients who required a second ablation session for a successful outcome. The accessory pathway in the 65 patients in this study was located in the right free wall in 19 patients (29%), septum in 14 (22%) and left free wall in 32 (49%). RESULTS: The primary reasons for a lengthy or failed ablation attempt were 1) inability to position the ablation catheter at the effective target site (16 patients, 25%); 2) instability of the ablation catheter or inadequate tissue contact at the target site, or both (15 patients, 23%); 3) mapping error due to an oblique course of the accessory pathway (7 patients, 11%); 4) failure to recognize a posteroseptal accessory pathway as being left-sided instead of right-sided (4 patients, 6%); 5) other errors in accessory pathway localization (6 patients, 9%); 6) epicardial location of the accessory pathway (5 patients, 8%); 7) recurrent atrial fibrillation (2 patients, 3%); 8) occurrence of a complication (2 patients, 3%); 9) unusual right-sided accessory pathway that inserted in the anterior right ventricle, 2 cm away from the lateral tricuspid annulus (1 patient, 1.5%); and 10) unexplained factors (7 patients, 11%). The most common effective strategies employed to achieve a successful outcome in these patients were 1) substitution of a more experienced operator; 2) use of ablation catheters of varying configurations; 3) switching from a retrograde aortic to a trans-septal approach; 4) switching from an inferior to a superior vena caval approach; 5) use of a 60-cm guiding sheath; 6) detailed mapping of the atrial or ventricular insertion of the accessory pathway; and 7) searching within the coronary sinus for a presumed accessory pathway potential. CONCLUSIONS: A lengthy or failed attempt at catheter ablation of an accessory pathway may be due to a variety of reasons, the most common of which are problems related to some aspect of catheter manipulation and errors in accessory pathway localization. Knowledge of the most common reasons for a lengthy or ineffective procedure may facilitate successful outcome of accessory pathway ablation.

Treatment of underlying atrial fibrillation: paced rhythm obscures recognition.

OBJECTIVES: The purpose of this study was to evaluate the rate of recognition of atrial fibrillation (AF), use of warfarin and prevalence of cerebrovascular accident (CVA) in paced versus unpaced patients during admission to a tertiary care teaching hospital. BACKGROUND: The presence of AF underlying a continuously paced rhythm may be under recognized and result in a lower rate of anticoagulation and higher incidence of CVA. METHODS: The identification of AF on 12 lead electrocardiogram (ECG) and telemetry, "optimal use" of anticoagulants that is, warfarin or aspirin, when warfarin is contraindicated and history of prior CVA was studied in three groups: 1) group A with continuously paced rhythm on ECG and telemetry (n = 30), 2) group B with intermittently paced rhythm on ECG and telemetry (n = 59), and 3) group C with persistent AF and no permanent pacemaker (n = 50). RESULTS: The identification and documentation of AF was significantly lower in the continuously paced group A (20%) versus the intermittently paced group B (44%). Both groups A and B were substantially lower than unpaced controls. "Optimal use" of anticoagulants was significantly lower in group A (40%) compared with groups B (78%) and C (72%) but was not different between groups B and C. The prevalence of prior CVA was not significantly different between the three groups. CONCLUSIONS: All ECGs in patients with paced rhythm should be examined closely for underlying AF to prevent under-recognition and under-treatment with anticoagulants.

Prospective, randomized comparison of conventional and high dose loading regimens of amiodarone in the treatment of ventricular tachycardia.

OBJECTIVES: The purpose of this prospective randomized study was to compare the electrophysiologic effects of conventional and high dose loading regimens of amiodarone in patients with sustained ventricular tachycardia. BACKGROUND: Uncontrolled studies in which patients have been treated with an oral loading dose of 2 to 4 g/day of amiodarone have suggested that, compared with a conventional loading dose, this dosing regimen results in more rapid control of spontaneous ventricular tachycardia and ventricular tachycardia induced by programmed stimulation. METHODS: Patients in whom sustained monomorphic ventricular tachycardia was inducible by programmed stimulation and who were refractory to class I antiarrhythmic medications were randomly assigned to receive either a conventional (n = 15) or a high (n = 17) loading dose of amiodarone. The conventional dose consisted of 600 mg twice a day for 10 days. The high dose regimen consisted of 50 mg/kg body weight per day on days 1 to 3, 30 mg/kg per day on days 4 and 5 and 600 mg twice a day on days 6 to 10. An electrophysiologic test was performed in the baseline state and after 3 and 10 days of therapy. An adequate response to amiodarone was defined as the inability to induce ventricular tachycardia or the ability to induce only relatively slow (cycle length > or = 350 ms) hemodynamically stable ventricular tachycardia. RESULTS: After 3 days of therapy, 2 of 14 patients who received the conventional loading dose and 6 of 15 patients who received the high dose loading regimen had an adequate response to amiodarone (p = 0.08). After 10 days of therapy, four patients in each group had an adequate response to amiodarone (p = NS). Three patients who received the high dose and one patient who received the conventional dose of amiodarone had an adequate response after 3 days of therapy but not after 10 days of therapy. There were significant increases in the sinus cycle length, atrioventricular block cycle length, ventricular effective refractory period and ventricular tachycardia cycle length after 3 and 10 days of therapy compared with baseline values regardless of the dosing regimen. The extent of the effects of amiodarone on these variables after 3 and 10 days of therapy was similar with both dosing regimens. CONCLUSIONS: The therapeutic and electrophysiologic effects of conventional and high dose loading regimens of amiodarone do not differ significantly after 3 or 10 days of therapy. High oral loading doses of amiodarone do not offer any significant clinical advantage over a conventional loading dose of amiodarone for controlling ventricular tachycardia induced by programmed stimulation.

Recognition and catheter ablation of subepicardial accessory pathways.

OBJECTIVES: The purpose of this study was to characterize left-sided accessory pathways that traverse the atrioventricular (AV) groove subepicardially and to describe results of radiofrequency catheter ablation within the coronary sinus in the patients studied. BACKGROUND: Radiofrequency catheter ablation has proved to be a safe and effective method for treatment of accessory pathways; however, subepicardial accessory pathways may account for some of the failures encountered during endocardial ablation. METHODS: The study group comprised 51 consecutive patients with a left-sided accessory pathway who were undergoing radio-frequency catheter ablation. Initially, the ablation catheter was introduced into a femoral artery and positioned on the ventricular aspect of the mitral annulus. If this endocardial approach was unsuccessful, the ablation catheter was introduced into the coronary sinus and energy applied at sites with shorter activation times than those recorded from the endocardium. RESULTS: Five (10%) of 51 patients with a left-sided accessory pathway could not have accessory pathway conduction interrupted with a median of 18 endocardial radiofrequency energy applications. Accessory pathway potentials were less frequent during endocardial mapping in these 5 patients than in the 46 patients whose accessory pathway was successfully ablated from the endocardial surface. All five of these patients later had successful ablation using one or two applications of radiofrequency energy from within the coronary sinus. Effective target site electrograms in the coronary sinus were characterized by an accessory pathway potential that was larger than the corresponding atrial or ventricular electrogram. There were no complications or recurrences after ablation within the coronary sinus. CONCLUSIONS: Some left-sided accessory pathways may be difficult to ablate from the endocardial surface because they traverse the AV groove subepicardially. The absence of an accessory pathway potential during endocardial mapping in combination with a relatively large accessory pathway potential within the coronary sinus may be a useful marker of a subepicardial pathway. In this select group of patients, radiofrequency catheter ablation from within the coronary sinus appears to enhance efficacy.

Effect of first-phase polarity of biphasic shocks on defibrillation threshold with a single transvenous lead system.

OBJECTIVES: The purpose of this study was to determine whether the polarity of the first phase of a biphasic shock affects the defibrillation threshold. BACKGROUND: The polarity of a monophasic shock has been shown to affect the defibrillation threshold. METHODS: A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 15 consecutive patients, the defibrillation threshold was determined twice using a step-down protocol, in random order: with the distal coil as the anode for the initial phase (anodal biphasic shock) and with the polarity reversed (cathodal biphasic shock). The power to detect a 5.0-J difference in this study is 0.96. These patients were 61 +/- 11 years old (mean +/- SD), and the mean left ventricular ejection fraction was 0.32 +/- 0.10. RESULTS: Mean defibrillation threshold using anodal biphasic shocks was 9.9 +/- 4.8 J, compared with 9.5 +/- 4.2 J using cathodal biphasic shocks (p = 0.8). In three patients the defibrillation threshold was lower by a mean of 6.3 +/- 2.9 J with the former configuration; in three patients the defibrillation threshold was lower by a mean of 6.7 +/- 2.5 J with the latter configuration; and in nine patients it was the same. Using the standard cathodal configuration, a defibrillation threshold < or = 10 J was obtained in approximately 70% of patients, and a subcutaneous patch was not required in any patient. CONCLUSIONS: The polarity of the first phase of a biphasic shock used with a single transvenous lead does not affect the defibrillation threshold.

Effect of shock polarity on ventricular defibrillation threshold using a transvenous lead system.

OBJECTIVES: The purpose of this study was to determine whether the polarity of a monophasic shock used with a transvenous lead system affects the defibrillation threshold. BACKGROUND: The ability to implant an automatic defibrillator depends on achieving an adequate defibrillation threshold. METHODS: A transvenous defibrillation lead with distal and proximal shocking electrodes was used in this study. In 29 consecutive patients, the defibrillation threshold, using a stepdown protocol was determined twice in random order: 1) with the distal coil as the anode, and 2) with the polarity reversed. Only the 20 patients in whom an adequate defibrillation threshold could be obtained with the transvenous lead alone were included in this study. These patients were 61 +/- 14 years old (mean +/- SD) and had a mean ejection fraction of 28 +/- 12%. RESULTS: The mean defibrillation threshold was 11.5 +/- 5.0 J with the distal coil as the anode versus 16.9 +/- 7.7 J with the distal coil as the cathode (p = 0.04). The defibrillation threshold was lower by a mean of 9 +/- 7 J with the former configuration in 14 patients and was lower by a mean of 7 +/- 6 J with the latter configuration in 3 patients; in 3 patients it was the same with both configurations. Use of a subcutaneous patch was avoided in five patients by utilizing the distal electrode as the anode. CONCLUSIONS: Defibrillation thresholds with monophasic shocks are approximately 30% lower with the distal electrode as the anode. The use of anodal shocks may obviate the need for a subcutaneous patch and allow more frequent implantation of a transvenous lead system.

Response to pacing at sites of isolated diastolic potentials during ventricular tachycardia in patients with previous myocardial infarction.

OBJECTIVES: The goal of this study was to determine whether isolated diastolic potentials (IDPs) recorded during ventricular tachycardia (VT) are generated in zones of slow conduction and whether the arcs of block that bound these zones of slow conduction are functional or anatomic in nature. BACKGROUND: No previous studies have systematically investigated the response to pacing during VT and sinus rhythm at sites where IDPs are recorded. METHODS: The study included 11 patients with a previous infarction who underwent radiofrequency catheter ablation of 15 hemodynamically stable, sustained VTs and in whom an IDP that could not be dissociated from the VT was detected during mapping. RESULTS: Pacing during VT at the site where the IDP was recorded resulted in concealed entrainment in each of the 15 VTs. In 10 of the 15 VTs, an IDP was present during sinus rhythm at the same site at which a diastolic potential was recorded during VT. In nine VTs, the isolated potential occurred early in diastole; in these cases, the QRS configuration during pacing in the setting of sinus rhythm was different from that during VT. In six VTs, the isolated potential occurred later in diastole, and in these cases, the QRS configuration during pacing in the setting of sinus rhythm was the same as that during VT. CONCLUSIONS: Isolated diastolic potentials may often be generated in an area of slow conduction bounded by arcs of block that are anatomically determined and present during sinus rhythm.

Slow pathway ablation in patients with documented but noninducible paroxysmal supraventricular tachycardia.

OBJECTIVES: The purpose of this study was to assess the clinical efficacy of radiofrequency ablation of the slow pathway in patients with documented but noninducible paroxysmal supraventricular tachycardia (PSVT) who have evidence of dual atrioventricular (AV) node pathways. BACKGROUND: Patients with a documented history of PSVT at times do not have inducible PSVT in the electrophysiology laboratory. Because dual AV node pathways serve as the substrate for AV node reentrant tachycardia (AVNRT), ablation of the slow pathway potentially may be useful in these patients. METHODS: The subjects in this prospective study were seven consecutive patients who underwent an electrophysiologic procedure because of documented PSVT and were found to have dual AV node physiology or inducible single AV node echo beats, but no inducible PSVT despite the administration of isoproterenol and atropine. Their mean (+/- SD) age was 33 +/- 13 years, and they had been symptomatic for 12 +/- 12 years. The frequency of the episodes of PSVT ranged from > or = 1/day to 1/month. The rate of the documented episodes ranged from 170 to 260 beats/min, and discrete P waves were not apparent. Slow pathway ablation was performed with 9 +/- 4 applications of radiofrequency energy using a combined anatomic and electrogram mapping approach. RESULTS: All evidence of dual AV node pathways was eliminated in six patients, and dual AV node physiology remained present in one patient. During a mean follow-up period of 15 +/- 10 months (range 8 to 27), no patient had a recurrence of symptomatic tachycardia (success rate 95% confidence interval 65% to 100%). CONCLUSIONS: Slow pathway ablation may be clinically useful in patients with documented but noinducible PSVT who have evidence of dual AV node pathways.

2:1 atrioventricular block during atrioventricular node reentrant tachycardia.

OBJECTIVES: The purpose of this study was to determine the incidence and to clarify the mechanism of 2:1 atrioventricular (AV) block during AV node reentrant tachycardia induced in the electrophysiology laboratory. BACKGROUND: In patients with 2:1 AV block during AV node reentrant tachycardia, the absence of a His bundle potential in the blocked beats has been considered evidence of intranodal, lower common pathway block. METHODS: In consecutive patients with AV node reentrant tachycardia, the incidence of 2:1 AV block and the response to atropine and a single ventricular extrastimulus was observed. RESULTS: Persistent 2:1 AV block occurred in 13 of 139 patients with AV node reentrant tachycardia. A His bundle deflection was present in the blocked beats in eight patients and absent in five. Patients with 2:1 AV block had a shorter tachycardia cycle length than did patients without such block (mean +/- SD 312 +/- 32 vs. 353 +/- 55 ms, p < 0.01). Atropine did not alter the 2:1 block in any patient. In every patient, a single ventricular extrastimulus introduced during the tachycardia converted the 2:1 block to 1:1 conduction. CONCLUSIONS: The incidence of induced 2:1 AV block during AV node reentrant tachycardia is approximately 10%. The lack of a response to atropine and the consistent conversion of 2:1 block to 1:1 conduction by a ventricular extrastimulus indicate that, regardless of the presence or absence of a His bundle potential in blocked beats, 2:1 block during AV node reentrant tachycardia is due to functional infranodal block.

Long-term follow-up after radiofrequency modification of the atrioventricular node in patients with atrial fibrillation.

OBJECTIVES: The purpose of this study was to describe the long-term follow-up results in 62 patients with atrial fibrillation and an uncontrolled ventricular rate, who underwent radiofrequency modification of the atrioventricular (AV) node. BACKGROUND: Previous studies in small numbers of patients have suggested that radiofrequency modification may be effective in controlling the ventricular rate in patients with atrial fibrillation, but long-term follow-up data have been lacking. METHODS: The subjects of this study were 62 consecutive patients (mean age +/- SD 65 +/- 14 years; 43 with structural heart disease) who underwent an attempt at radiofrequency modification of the AV node because of symptomatic, drug-refractory atrial fibrillation with an uncontrolled ventricular rate. The atrial fibrillation was chronic in 46 patients and paroxysmal in 16. Radiofrequency energy was applied to the posteroseptal or mid-septal right atrium to lower the ventricular rate in atrial fibrillation to 120 to 130 beats/min during an infusion of 4 micrograms/min of isoproterenol. RESULTS: Short-term control of the ventricular rate was successfully achieved without the induction of pathologic AV block in 50 (81%) of 62 patients. Inadvertent high degree AV block occurred in 10 (16%) of 62 patients, with the AV block occurring at the time of the procedure in 6 patients and 36 to 72 h after the procedure in 4. During 19 +/- 8 months of follow-up (range 4 to 33), 5 (10%) of 50 patients had a symptomatic recurrence of an uncontrolled rate during atrial fibrillation. Overall, adequate rate control at rest and during exertion, without pathologic AV block, was achieved long term in 45 (73%) of 62 patients. Among 37 patients with a successful outcome, left ventricular ejection fraction increased from (mean +/- SD) 0.44 +/- 0.14 to 0.51 +/- 0.10 one year later (p < 0.001). Complications other than AV block included polymorphic ventricular tachycardia 10 to 24 h after the procedure in two patients who had a predisposing factor for ventricular tachycardia and sudden death 1 to 5 months after the procedure in two patients with idiopathic dilated cardiomyopathy, one of whom had a pacemaker for AV block. CONCLUSIONS: In approximately 70% of properly selected patients with atrial fibrillation and an uncontrolled ventricular rate, radiofrequency modification of the AV node results in excellent long-term control of the ventricular rate at rest and during exertion.

Radiofrequency catheter ablation of inappropriate sinus tachycardia guided by activation mapping.

OBJECTIVE: The purpose of this study was to evaluate the value of activation mapping for radiofrequency modification of the sinus node and the long-term success rate of the procedure in a series of patients with inappropriate sinus tachycardia. BACKGROUND: The results of radiofrequency ablation of inappropriate sinus tachycardia have been reported in only a small number of patients. METHODS: The subjects of this study were 29 consecutive drug-refractory patients who underwent catheter ablation of inappropriate sinus tachycardia. Target sites were selected by activation mapping during sinus tachycardia. RESULTS: The ablation procedure was successful acutely in reducing the baseline sinus rate to <90/min and the sinus rate during isoproterenol infusion by >20% in 22 of 29 patients (76%). In 13 of 22 patients (59%) with a successful acute outcome, successive applications of radiofrequency energy at the site of earliest endocardial activation resulted in a cranial-caudal migration of earliest endocardial activation from the high lateral right atrium, along with a step-wise reduction in heart rate. In the other nine patients (41%) with a successful acute outcome, the reduction in sinus rate occurred abruptly, unaccompanied by migration of the site of earliest activation. Symptoms due to inappropriate sinus tachycardia recurred at a mean of 4.4+/-; 3 months after the ablation procedure in 6 of 22 patients (27%). After additional procedures in three patients, symptoms of inappropriate sinus tachycardia ultimately were successfully eliminated over the long-term in 19 of 29 patients (66%). CONCLUSIONS: In conclusion, radiofrequency ablation is at best only modestly effective for managing patients with inappropriate sinus tachycardia. The two different responses of heart rate to radiofrequency ablation may reflect differences in the number and/or multicentricity of subsidiary sites of impulse generation within the sinus node and/or atrium in patients with inappropriate sinus tachycardia.

Use of adenosine in patients hospitalized in a university medical center.

PURPOSE: Adenosine is a useful agent for the diagnosis and termination of tachycardias. The purpose of this study was to identify the rhythms for which adenosine is prescribed in hospitalized adults and to identify the reasons for its misuse. PATIENTS AND METHODS: Data were collected from the medical records of 100 patients who received intravenous adenosine while hospitalized at a university medical center. The characteristics of the patients, rhythms treated with adenosine, and dosages of adenosine were analyzed. In addition, internal medicine house officers were administered a questionnaire referring to an electrocardiogram of atrial fibrillation with a rapid ventricular response. RESULTS: The arrhythmias for which adenosine was administered consisted of regular, narrow-QRS complex tachycardias in 33% of patients; atrial fibrillation in 32% of patients; regular, wide-QRS complex tachycardias in 23% of patients; atrial flutter in 10% of patients, and multifocal atrial tachycardia in 2% of patients. The mean (+/-SD) number of doses of adenosine given to each patient was 1.6+/-0.8, and the mean dose of adenosine was 7.8+/-2.8 mg. Internal medicine house officers prescribed 70% of the doses of adenosine and were as likely to use it for patients with atrial fibrillation as were surgical house officers. There was a 2% incidence of proarrhythmia, including asystole and polymorphic ventricular tachycardia. Thirty-one percent of the 100 house officers in our survey misdiagnosed a 12-lead electrocardiogram of rapid atrial fibrillation as paroxysmal supraventricular tachycardia, suggesting that adenosine may have been misused for atrial fibrillation because of errors in rhythm diagnosis. Only 5% of those who correctly diagnosed atrial fibrillation also answered that adenosine would be likely to terminate the arrhythmia, suggesting that a misunderstanding that adenosine terminates atrial fibrillation is not a common reason for its misuse. CONCLUSIONS: Approximately 40% of hospitalized adults who are treated with adenosine receive the medication unnecessarily for atrial fibrillation or atrial flutter, and this misuse results in unnecessary expenses and risks of adverse effects. The primary reason that adenosine is misused for atrial fibrillation is the inability to recognize that rhythm on an electrocardiogram. House officers need additional education on the electrocardiographic recognition of atrial fibrillation.

Relation between amiodarone and desethylamiodarone plasma concentrations and ventricular defibrillation energy requirements.

The main finding of this prospective, controlled study is that amiodarone and desethylamiodarone plasma concentrations < 1 mg/L are associated with a 23% increase in the acute defibrillation energy requirement and with a 31% increase in the requirement for a subcutaneous patch or array. The defibrillation energy requirement does not correlate with the plasma concentrations of amiodarone, desethylamiodarone, amiodarone plus desethylamiodarone, or with the duration or daily dosage of amiodarone therapy.

A randomized comparison of the right- and left-sided approaches to ablation of the atrioventricular junction.

Radiofrequency ablation of the atrioventricular (AV) junction may be performed using either a right- or left-sided approach. This study prospectively compared the left-sided approach with persistent attempts from the right side in patients in whom initial radiofrequency applications on the right side were unsuccessful. Twenty-one of 54 patients did not have complete AV block induced after 3 right-sided radiofrequency applications. These 21 patients were randomly assigned to undergo either the left-sided approach (n = 10) or to undergo additional attempts from the right side (n = 11). The right-sided approach was performed by positioning the ablation catheter to record the largest possible atrial and His bundle electrograms. The left-sided approach was performed by positioning the ablation catheter along the left ventricular septum, where a His bundle potential was recorded. If either approach was not successful after an additional 17 radiofrequency applications, the alternative approach was then used. The AV junction was successfully ablated in all 10 patients randomized to the left-sided approach, but in only 6 of 11 patients randomized to persistent right-sided attempts (p < 0.05). The 5 patients in whom the AV junction was not successfully ablated using the right-sided approach underwent the left-sided approach and had a successful outcome after a mean of 1.2 +/- 0.4 radiofrequency applications. The left-sided approach required significantly fewer radiofrequency applications after randomization than the right-sided approach (3 +/- 3.4 vs 11 +/- 7.6, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiologic effects of sotalol and amiodarone in patients with sustained monomorphic ventricular tachycardia.

No prospective studies have compared sotalol and amiodarone during electropharmacologic testing. The purpose of this prospective, randomized study was to compare the electrophysiologic effects of sotalol and amiodarone in patients with coronary artery disease and sustained monomorphic ventricular tachycardia (VT). Patients with coronary artery disease and sustained monomorphic VT inducible by programmed stimulation were randomly assigned to receive either sotalol (n = 17) or amiodarone (n = 17). The sotalol dose was titrated to 240 mg twice daily over 7 days. Amiodarone dosing consisted of 600 mg 3 times daily for 10 days. An electrophysiologic test was performed in the baseline state and at the end of the loading regimen. An adequate response was defined as the inability to induce VT or the ability to induce only relatively slow hemodynamically stable VT. During the follow-up electrophysiologic test, 24% of patients taking sotalol and 41% of those taking amiodarone had an adequate response to therapy (p = 0.30). Amiodarone lengthened the mean VT cycle length to a greater degree than sotalol (28% vs 12%, p < 0.01). There were no significant differences in the effects of sotalol and amiodarone on the ventricular effective refractory period. In patients with coronary artery disease, amiodarone and sotalol are similar in efficacy in the treatment of VT as assessed by electropharmacologic testing. The effects of the 2 drugs on ventricular refractoriness are similar, but amiodarone slows VT to a greater extent than sotalol.

Comparison of implantation of nonthoracotomy defibrillators in the operating room versus the electrophysiology laboratory.

Implantable cardioverter-defibrillators (ICDs) with nonthoracotomy lead systems are widely available, and are implanted either in the electrophysiology laboratory or the operating room. The purpose of this study was to prospectively evaluate the safety and efficacy of nonthoracotomy ICD implantation in an electrophysiology laboratory versus an operating room. During a 7-month period, 62 consecutive ICDs with nonthoracotomy lead systems were implanted in patients in an electrophysiology laboratory. During the next 10 months, 110 consecutive ICDs were implanted in patients in a surgical operating room. All ICD implantations were performed under general anesthesia by electrophysiologists. There were no differences in age (58 +/- 14 vs 62 +/- 12 years, p = 0.06), gender distribution (p = 0.3), frequency of structural heart disease (97% vs 97%, p = 0.9), ejection fraction (0.31 +/- 0.15 vs 0.29 +/- 0.13, p = 0.3), or presentation with cardiac arrest (65% vs 53%, p = 0.2) between patients undergoing ICD implantation in the electrophysiology laboratory and operating room, respectively. The rate of successful implantation and of complications for systems implanted in the electrophysiology laboratory (95% and 13%, respectively) and in the operating room (98% and 14%, respectively) were similar (p = 0.4 and p = 0.8, respectively). Specifically, the rate of infection (0% vs 4%, p = 0.3) and hematoma formation (2% vs 4%, p = 0.8) were not statistically significantly different. Three patients who had undergone ICD implantation in an operating room died within 30 days. ICDs with nonthoracotomy lead systems can be implanted with a similarly high rate of success and acceptable complication rate in the electrophysiology laboratory and in the operating room.

Long-term follow-up after radiofrequency ablation of paroxysmal supraventricular tachycardia in patients with tachycardia-induced atrial fibrillation.

Four of 12 patients (33%) with paroxysmal supraventricular tachycardia (PSVT) and tachycardia-induced atrial fibrillation (AF) had recurrences of paroxysmal AF after successful catheter ablation of the PSVT. This study demonstrates that AF often remains a problem after radiofrequency catheter ablation of PSVT in patients with tachycardia-induced AF, and it may not be possible to predict in which patients this will be the case.

Predictors of crossover to a left ventricular approach for atrioventricular junction ablation.

In a retrospective analysis of patients referred for atrioventricular node radiofrequency ablation, male gender and a history of hypertension were found to be predictors of crossover to a left ventricular approach for success. This subgroup of patients may benefit from early crossover if initial attempts at right-sided ablation fail.

Prospective assessment of the minimum energy needed for external electrical cardioversion of atrial fibrillation.

This study demonstrates that shocks <200 J often are effective for transthoracic cardioversion of atrial fibrillation (AF). Lower energy shocks are more likely to be effective when the AF is <24 hours in duration or in patients with idiopathic AF.