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Background: Despite the high success rate of radiofrequency (RF) ablation, pharmacologic therapy is still considered the standard initial therapeutic approach for atrial flutter., Objective: We prospectively compared the outcome at follow-up of patients with atrial flutter randomly assigned to drug therapy or RF ablation., Methods: Patients with at least two episodes of symptomatic atrial flutter in the last four months were randomized to regimens of either antiarrhythmic drug therapy or first-line RF ablation. After institution of therapy, end points included recurrence of atrial flutter, rehospitalization and quality of life., Results: A total of 61 patients entered the study, 30 of whom were randomized to drug therapy and 31 to RF ablation. After a mean follow-up of 21 +/- 11 months, 11 of 30 (36%) patients receiving drugs were in sinus rhythm, versus 25 of 31 (80%) patients who underwent RF ablation (p < 0.01). Of the patients receiving drugs, 63% required one or more rehospitalizations, whereas post-RF ablation, only 22% of patients were rehospitalized (p < 0.01). Following RF ablation, 29% of patients developed atrial fibrillation which was seen in 53% of patients receiving medications (p < 0.05). Sense of well being (pre-RF 2.0 +/- 0.3 vs. post-RF 3.8 +/- 0.5, p < 0.01) and function in daily life (pre-RF 2.3 +/- 0.4 vs. post-RF 3.6 +/- 0.6, p < 0.01) improved after ablation, but did not change significantly in patients treated with drugs., Conclusion: In a selected group of patients with atrial flutter, RF ablation could be considered a first-line therapy due to the better success rate and impact on quality of life, the lower occurrence of atrial fibrillation and the lower need for rehospitalization at follow-up.

Background: Sustained ventricular tachycardia (VT) and fibrillation (VF) occur in up to 20% of patients with acute myocardial infarction (MI) and have been associated with a poor prognosis. The relationships among the type of arrhythmia (VT versus VF or both), time of VT/VF occurrence, use of thrombolytic agents, and eventual outcome are unclear., Methods and Results: In the GUSTO-I study, we examined variables associated with the occurrence of VT/VF and its impact on mortality. Of the 40 895 patients with ventricular arrhythmia data, 4188 (10.2%) had sustained VT, VF, or both. Older age, systemic hypertension, previous MI, Killip class, anterior infarct, and depressed ejection fraction were associated with a higher risk of sustained VT and VF (P<0.001). In-hospital and 30-day mortality rates were higher among patients with sustained VT/VF than among patients without sustained ventricular arrhythmias (P<0.001). Both early (<2 days) and late (>2 days) occurrences of sustained VT and VF were associated with a higher risk of later mortality (P<0. 001). In addition, patients with both VT and VF had worse outcomes than those with either VT or VF alone (P<0.001). Among patients who survived hospitalization, no significant difference was found in 30-day mortality between the VT/VF and no VT/VF groups. However, after 1 year, the mortality rate was significantly higher in the VT alone and VT/VF groups (P<0.0001)., Conclusions: Despite the use of thrombolytic therapy, both early and late occurrences of sustained VT or VF continue to have a negative impact on patient outcome; patients with both VT and VF had the worst outcome; and among patients who survived hospitalization, the 1-year mortality rate was significantly higher in those who experienced VT alone or VT and VF.

This study was designed to evaluate the ability to distinguish between supraventricular tachycardias (SVTs) and ventricular tachycardias (VTs) based on onset, stability, and width criteria in an implantable defibrillator. Inappropriate detection of atrial fibrillation and sinus tachycardia is a common problem in patients with implantable defibrillators. The onset, stability, and width criteria were studied in 17 patients who underwent implantation of a Medtronic 7218C implantable defibrillator by inducing sinus tachycardia and atrial fibrillation. Additional data on the width criteria was obtained by pacing at separate sites in both the left and right ventricle. Patients were studied at different times for up to 6 months to determine any changes in the criteria. The onset and stability criteria caused inappropriate detections in 36% and 12% of the episodes, respectively. The addition of the width criteria decreased the inappropriate detection using the onset and stability criteria to 5% and 2%, respectively. Pacing from the RV apex, RV outflow tract, and LV apex was appropriately detected as wide in 76%, 41%, and 94%, respectively. The width criteria changed over time in individual patients, but was stable by 6 months in all but one patient. No single criterion is satisfactory for distinguishing between SVT and VT in this patient population, but the combination of criteria seems to provide better discrimination. The width criteria can change dramatically over time and needs to be monitored carefully. Newer algorithms will need to be developed to allow better detection of supraventricular tachycardias.

The objective of this study was to assess the safety and efficacy of transvenous low energy cardioversion of atrial fibrillation in patients with ventricular tachycardia and atrial fibrillation and to study the mechanisms of proarrhythmia. Previous studies have demonstrated that cardioversion of atrial fibrillation using low energy, R wave synchronized, direct current shocks applied between catheters in the coronary sinus and right atrium is feasible. However, few data are available regarding the risk of ventricular proarrhythmia posed by internal atrial defibrillation shocks among patients with ventricular arrhythmias or structural heart disease. Atrial defibrillation was performed on 32 patients with monomorphic ventricular tachycardia and left ventricular dysfunction. Shocks were administered during atrial fibrillation (baseline shocks), isoproterenol infusion, ventricular pacing, ventricular tachycardia, and atrial pacing. Baseline shocks were also administered to 29 patients with a history of atrial fibrillation but no ventricular arrhythmias. A total of 932 baseline shocks were administered. No ventricular proarrhythmia was observed after well-synchronized baseline shocks, although rare inductions of ventricular fibrillation occurred after inappropriate T wave sensing. Shocks administered during wide-complex rhythms (ventricular pacing or ventricular tachycardia) frequently induced ventricular arrhythmias, but shocks administered during atrial pacing at identical ventricular rates did not cause proarrhythmia. The risk of ventricular proarrhythmia after well-synchronized atrial defibrillation shocks administered during narrow-complex rhythms is low, even in patients with a history of ventricular tachycardia. The mechanism of proarrhythmia during wide-complex rhythms appears not to be related to ventricular rate per se, but rather to the temporal relationship between shock delivery and the repolarization time of the previous QRS complex.

Unlabelled: Several procedures performed in the electrophysiology laboratory (EP lab) require surgical manipulation and are lengthy. Patients undergoing such procedures usually receive general anesthesia or deep sedation administered by an anesthesiologist. In 536 consecutive procedures performed in the EP lab, we assessed the safety and efficacy of deep sedation administered under the direction of an electrophysiologist and in the absence of an anesthetist. Patients were monitored with pulse oximetry, noninvasive blood pressure recordings, and continuous ECGs. The level of consciousness and vital signs were evaluated at 5-minute intervals. Deep sedation was induced in 260 patients using midazolam, phenergan, and meperidine, then maintained with intermittent dosing of meperidine at the following mean doses: midazolam 0.031 +/- 0.024 mg/kg; phenergan 0.314 +/- 0.179 mg/kg; and meperidine 0.391 +/- 0.167 mg/kg per hour. In the remaining 276 patients, deep sedation was induced with midazolam and fentanyl and maintained with a continuous infusion of fentanyl at a mean dose of 2.054 +/- 1.43 micrograms/kg per hour. Fourteen patients experienced a transient reduction in oxygen saturation that was readily reversed following administration of naloxone. An additional 11 patients desaturated secondary to partial airway obstruction, which resolved after repositioning the head and neck. Fourteen patients experienced hypotension with fentanyl. All but one returned to baseline blood pressures following an infusion of normal saline. No patient required intubation and no death occurred. Only three patients had recollection of periprocedure events. No patient remembered experiencing pain with the procedure. Hospital stays were not prolonged as a result of the sedation used., In Conclusion: (1) deep sedation during EP procedures can be administered safely under the guidance of the electrophysiologist without an anesthetist present; (2) the drugs used should be readily reversible in case of respiratory depression; and (3) this approach may reduce the overall cost of the procedures in the EP lab, maintaining adequate patient comfort.

Whether the presence of abnormal PR before selective slow pathway ablation for AV node reentrant tachycardia increased the risk of complete heart block remains controversial. We report our experience in seven patients with prolonged PR intervals undergoing catheter ablation for AV reentry tachycardia. Their mean age was 66 +/- 12 years; four patients were female and three were male. RF ablation was performed using an anatomically guided stepwise approach. In six patients, common type AV node reentry was induced and uncommon type was observed in the remaining patient. In all seven patients, successful selective slow pathway ablation was associated with no occurrence of complete heart block and was followed by shortening of the AH interval in five patients. In all seven patients, successful ablation was achieved at anterior sites (M1 in two patients and M2 in five patients). Despite AH shortening after ablation, the 1:1 AV conduction was prolonged after elimination of the slow pathway, excluding either sympathetic tone activation or parasympathetic denervation. In conclusion, selective slow pathway ablation can be performed safely in the majority of patients with prolonged PR interval before the procedure. Because successful ablation is achieved at anterior sites in most patients, careful selection and monitoring of catheter position is required.

Limited information is available regarding potential adverse interactions between transvenous nonthoracotomy cardioverter defibrillators and pacemakers. We describe our experience with 37 patients who have undergone successful implantation of both a transvenous defibrillator and pacemaker. The patients' mean age was 64 +/- 12.9 years. Thirty-three were male and four were female. The mean LVEF was 30.8% +/- 11.8%. The indications for pacemaker implantation included sick sinus syndrome in 13 patients, complete heart block in 15 patients, sinus bradycardia secondary to medications in 8 patients, and neurocardiogenic syncope in 1 patient. The indications for insertion of a defibrillator included medically refractory VT in 27 patients and sudden cardiac death in 10 patients. Twenty-three patients received an Endotak lead and 14 patients received a Transvene lead. Eighteen patients had a pacemaker prior to an ICD, 14 patients had an ICD prior to a pacemaker, and 4 patients had both devices placed simultaneously. Interaction was evaluated at implant of the second device and 1-3 days after both devices were placed. Detection of VF/VT was analyzed during asynchronous pacing (DOO/VOO) with maximum pacing output. In addition, in six patients, DFT was determined before and after pacemaker implantation. In 14 patients (38%), device interactions that could not always be optimally corrected were observed. In five patients, the pacemaker was reset to the "noise reversion" mode after high energy ICD discharge. Oversensing of atrial pacemaker stimuli resulted in inappropriate ICD firings in four patients. This was observed only with a specific device and could not be prevented by atrial lead repositioning in two of them, but required reprogramming of the pacemaker to the VVI mode. An increase in DFT was observed in five patients who had a pacemaker implanted after an ICD. Compared with previously published studies, a greater frequency of transvenous ICD and pacemaker interactions were observed. Considering that almost 50% of the patients already have a pacemaker at the time of ICD implant, the availability of defibrillators with dual chamber pacing capability will not eliminate the potential for this problem.

Unlabelled: No definitive data are available about the possibility of predicting improvement in patients with neurocardiogenic syncope treated with beta blockers. Among 112 patients with syncope and a positive head-up tilt test (HUT), independent predictors for prevention of symptoms with beta blockers were determined using the Cox proportional hazards model. Each patient underwent HUT at 70 degrees for 20 minutes both in the drug-free state and during isoproterenol infusion given to increase the heart rate by at least 25%. Fifty-nine patients had a positive HUT during isoproterenol infusion and 53 in the drug-free state. All patients were then given esmolol infusion at 500 micrograms/kg per minute for 3 minutes followed by 300 micrograms/kg per minute maintenance dose. HUT was then repeated as previously described with or without isoproterenol, depending upon the initial positive response. Regardless of the response during esmolol, all patients were treated with metoprolol 50 to 100 mg twice daily. At follow-up, 36 patients experienced symptom relapse. Four of them had negative HUT on esmolol, whereas the remaining 32 did not respond to the acute infusion of esmolol. Only four patients with positive HUT on esmolol had a favorable response to metoprolol. Patients responding to metoprolol were older (55 +/- 12 years vs 42 +/- 15 years, P < 0.05). Response to metoprolol was predicted by a negative test on esmolol (P < 0.0001) and a positive HUT on isoproterenol (P < 0.001). Age older than 42 years was also associated with a higher likelihood of metoprolol success (P < 0.02)., Conclusion: Acute challenge with esmolol infusion appears to be an accurate predictor of response to chronic beta blockers, together with age and a positive HUT during low-dose isoproterenol infusion.

Background: Whether thrombolytic therapy alters the incidence and clinical outcome of bundle-branch block is unclear., Methods and Results: We examined the occurrence of new-onset bundle-branch block, both transient and persistent, in 681 patients with acute myocardial infarction enrolled in the Thrombolysis and Angioplasty in Myocardial Infarction 9 and Global Utilization of Streptokinase and t-PA for Occluded Arteries 1 protocols. Each patient underwent continuous 12-lead ECG monitoring for 36 to 72 hours with the Mortara ST monitoring system. Bundle-branch block was characterized as right, left, alternating, transient, or persistent. The overall incidence of bundle-branch block was 23.6% (n = 161), with transient block in 18.4% (n = 125) and persistent block in 5.3% (n = 36). Right bundle-branch block was found in 13% (n = 89) of the population; left bundle-branch block was found in 7% (n = 48). Alternating bundle-branch block was seen in 3.5% (n = 24) of patients. Left anterior descending artery infarcts accounted for most bundles (54%, n = 79). Patients with bundle-branch block had lower ejection fractions, higher peak creatine phosphokinase levels (P < .0001), and more diseased vessels (P < .019). Mortality rates in patients with and without bundle-branch block were 8.7% and 3.5%, respectively (P < .007). A higher mortality rate was observed in the presence of persistent (19.4%) versus transient (5.6%) or no (3.5%) bundle-branch block (P < .001)., Conclusions: Thrombolytic therapy reduces the overall mortality rate associated with persistent bundle-branch block. However, persistent bundle-branch block remains predictive of a higher mortality rate than either transient or no bundle-branch block. Continuous 12-lead ECG monitoring provides an accurate characterization of the incidence and type of conduction disturbances after acute myocardial infarction.

Unlabelled: The presence of chronic indwelling leads in the area targeted for RF ablation may pose a technical challenge and reduce the chance of success of the ablation. In addition, application of lesions in close proximity to pacemaker leads or other permanent catheters could affect their function. Fourteen patients referred for RF ablation of atrial flutter/fibrillation and atrial tachycardia, who had a permanent dual chamber pacemaker (10 patients), ICD (1 patient), or both (3 patients) were studied to assess the safety, efficacy, and effects of the ablative procedure on device function. Lead impedance, R and P wave amplitude, and pacing threshold of the defibrillator and pacemaker were measured before and after ablation. The procedure was successful in all patients. In one patient who underwent both atrial flutter and atrial fibrillation ablation, the atrial pacing threshold increased from 1.0 preablation to 2.0 V postablation. No P wave was detectable after ablation. In another patient, the P wave amplitude went from 4.0 to 2.0 mV postablation. In both patients the device converted to the power reset mode. No changes were observed in the remaining patients. Postablation defibrillator testing showed no malfunction. Follow-up reinterrogation of the devices revealed no alterations., In Conclusion: (1) RF ablation of atrial flutter and/or tachycardia is feasible even in patients with multiple chronic atrial and ventricular indwelling catheters; and (2) RF applications in close proximity of defibrillator and pacing catheters does not appear to alter their function unless lesions are produced in the area surrounding the distal pacing electrode.

Objectives: The goal of this study was to compare the effect of different tilts and capacitances for biphasic shocks on atrial defibrillation efficacy and pain threshold., Background: Although biphasic shocks have been shown to be superior to monophasic shocks, the effect of tilt and capacitance on atrial defibrillation success and pain perception has not been studied in patients., Methods: Atrial defibrillation threshold (DFT) testing was performed using a right atrial appendage/coronary sinus lead configuration in 38 patients with a history of paroxysmal atrial fibrillation undergoing an invasive electrophysiologic study. Biphasic waveforms with 40%, 50%, 65%, 80%, 30%/50% and 40%/50% were tested randomly in 22 patients (Group 1). In 16 patients (Group 2), a 65% tilt waveform with 50- and 120-microF capacitance was tested. Before sedation, pain sensation was graded by 15 patients in Group 1 after delivery of a 0.5-J shock and by 10 patients in Group 2 after two 1.5-J shocks with 50- and 120-microF capacitance were delivered., Results: The DFT energy for the 50% tilt waveform was significantly lower than the 65%, 80% and 30%/50% tilt waveforms. The 40%/50% tilt waveform provided slightly lower energy requirements than the 50% tilt waveform. Nine patients (60%) described the 0.5-J shock as very painful, and four (26.6%) complained of slight pain. The 50-microF capacitor lowered energy requirements compared with the 120-microF capacitor. Six patients (60%) perceived the 1.5-J 50-microF capacitor shock as more painful, whereas three (30%) perceived both shocks as equally painful., Conclusions: Biphasic waveforms with 50% tilt in both phases and a smaller tilt in the positive phase than that in the negative phase (40%/50%) provided a decrease in energy requirements at atrial DFT. In addition, stored energy was reduced by biphasic shocks with 50-microF capacitance compared with 120-microF capacitance. Despite the reduction in energy requirements, shocks < 1 J continued to be perceived as painful in the majority of patients.

In 54 patients with positive tilt and who refused medical therapy, we observed a significant decrease in the frequency of syncopal spells after diagnosis and counseling. However, symptoms were reported at follow-up by 64.8% of the patients and were predicted by the frequency and total number of syncope episodes before upright tilt.

Unlabelled: Implantation of implantable cardioverter defibrillators (ICDs) in the electrophysiology (EP) laboratory has been shown to be safe. However, general endotracheal anesthesia and/or administration of sedatives is mostly performed by anesthesiologists. In 53 patients undergoing ICD implantation in the EP laboratory, we prospectively assessed whether deep sedation without endotracheal intubation can be administered by nursing personnel under medical supervision. The mean patient age was 67 +/- 7 years, and the mean ejection fraction was 32 +/- 8%. All ICDs were placed in the abdomen requiring lead tunneling. Patients were monitored with pulse oximetry and noninvasive blood pressure recordings. The level of consciousness and vital signs were evaluated at 5-minute intervals. Deep sedation was induced with phenergan and midazolam and maintained with either meperidine or fentanyl. The mean doses given were as follows: phenergan 0.33 +/- 0.15 mg/kg, midazolam 0.05 +/- 0.03 mg/kg, meperidine 0.46 +/- 0.10 mg/kg per hour, and fentanyl 1.94 +/- 0.71 micrograms/kg per hour. None of the patients required intubation during or after the procedure. No death occurred and no patient had any recollection of the procedure. In three patients, O2 desaturation was easily managed by transient reversion of the effects of meperidine or fentanyl with naloxone. No patient experienced prolonged hospitalization after the implant (mean 2.4 +/- 0.5 days)., In Conclusion: (1) adequate sedation for ICD implantation and testing can be administered safely by nursing staff in the EP lab; (2) optimum sedation protocols should include drugs easy to reverse in case of excessive respiratory depression; and (3) this may represent a more cost-effective approach to ICD implantation.

In a study of 11 dogs, we assessed whether the defibrillation energy requirements of a single transvenous right ventricular electrode/defibrillator can system depended on the can size. We compared the defibrillation threshold obtained with 65% fixed-tilt biphasic shocks with 20, 40, and 80 ml surface area defibrillator cans. The energy was delivered between a right ventricular coil inserted through the jugular vein and the can placed in the subcutaneous tissue of the left superior chest wall. The testing order of each can size was randomly determined. Triplicate defibrillation thresholds were obtained with each can. Despite a higher impedance (20 ml 85 +/- 22 ohms vs 80 ml 71 +/- 16 ohms, p < 0.01), the 20 ml can resulted in a similar defibrillation threshold compared with the 80 ml (20 ml 7.6 +/- 2.8 J vs 80 ml 7.5 +/- 3.4 J) and the 40 ml cans (20 ml 7.6 +/- 2.8 J vs 7.5 +/- 3.4 J). In conclusion, with the unipolar lead system the can size does not appear to be a factor limiting defibrillation success. Even a can the size of a pacemaker does not appear to significantly affect the defibrillation efficacy of this lead system.