Outcome of resuscitation from bradyarrhythmic or asystolic prehospital cardiac arrest.

Previous studies of outcome as a function of the initial electrophysiologic mechanisms recorded at the scene of prehospital cardiac arrest have demonstrated that bradyarrhythmias and asystole have the worst prognosis. In this report, our observations in bradyarrhythmic and asystolic arrests occurring from 1980 to 1982 are compared with those from 1975 to 1978. From 1980 to 1982, 61 (27%) of 225 cardiac arrest events meeting entry criteria for the study were bradyarrhythmic or asystolic. Only 2 (8%) of 24 patients with asystole and 1 (20%) of 5 patients with sinus bradycardia survived prehospital intervention. Only 1 of these 29 patients was discharged from the hospital alive. In contrast, 15 (47%) of 32 patients who presented with idioventricular rhythm at initial contact survived prehospital intervention and were hospitalized, and 8 (25%) of these 32 were ultimately discharged alive. When compared with the 1975 to 1978 patients with bradyarrhythmia and asystole, both prehospital survival (8 versus 30%, p less than 0.001) and survival after hospitalization (0 versus 15%, p less than 0.05) significantly improved, but the improvement occurred predominantly in the subgroup with idioventricular rhythm. Survivors within this subgroup tended to have a prompt response to prehospital pharmacologic interventions that were not available to the 1975 to 1978 group. The response was manifested by return to a sinus mechanism or increase in the rate of idioventricular rhythm. In conclusion, outcome has improved for a specific subgroup of victims of prehospital cardiac arrest with bradyarrhythmia or asystole; the improved outcome may relate to field interventions by rescue personnel at the scene of arrest but the mortality rate is still high.

Time to first shock and clinical outcome in patients receiving an automatic implantable cardioverter-defibrillator.

The relation between time to first shock and clinical outcome was studied in 60 patients who received an automatic implantable cardioverter-defibrillator (AICD) from August 1983 through May 1988. The mean (+/- SD) patient age was 64 +/- 10 years, 82% were men and the mean ejection fraction was 33 +/- 13%. During follow-up, 38 patients (63%) had one or more shocks; there were no differences in age, gender distribution or ejection fraction at entry between the shock and no shock groups. Among 51 patients with coronary artery disease, 31 (61%) had one or more shocks, whereas all seven patients with cardiomyopathy had one or more shocks (p less than 0.05). Neither of the two patients with idiopathic ventricular fibrillation had shocks. Of the 13 deaths, 12 occurred during post-hospital follow-up and 1 during the index hospitalization. Of the four sudden post-hospital deaths, only one was due to tachyarrhythmia in the absence of acute myocardial infarction. All four sudden deaths and five of eight post-hospital nonsudden deaths occurred in patients who had had one or more appropriate shocks during follow-up. Eight of the nine first appropriate shocks among patients who subsequently died occurred within the first 3 months of follow-up, but the actual deaths were delayed to a mean of 14.1 +/- 13.9 months (p less than 0.05). The mean time to all deaths was 14.8 +/- 13.1 months. The ejection fraction was significantly lower among patients who died than among patients who survived (25 +/- 7% versus 35 +/- 14%, p less than 0.02), but it did not distinguish risk of first shocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oral propafenone on defibrillation and pacing thresholds in patients receiving implantable cardioverter-defibrillators. Propafenone Defibrillation Threshold Investigators.

OBJECTIVES: The effects of propafenone, a predominantly class IC antiarrhythmic drug, on defibrillation and pacing thresholds were evaluated in patients undergoing cardioverter-defibrillator implantation. BACKGROUND: Previous studies have shown that the class IC agents encainide and flecainide may increase the energy requirements for pacing and defibrillation. Animal studies with propafenone have shown inconsistent results regarding its effect on defibrillation energy requirements. This report investigated the effects of propafenone on defibrillation and pacing thresholds in humans. METHODS: After cardioverter-defibrillator implantation, 47 patients were enrolled in a double-blind, three-way parallel, randomized trial of 450 mg/day (Group 1) or 675 mg/day (Group 2) of oral propafenone or placebo (Group 3) for 3 to 7 days. Predischarge defibrillation and pacing thresholds after treatment were compared with baseline thresholds obtained at implantation. RESULTS: There was no statistically significant difference between implantation and predischarge defibrillation thresholds in the three groups (Group 1: [mean +/- SE] 11.0 +/- 1.3 vs. 12.1 +/- 1.5 J; Group 2: 11.5 +/- 1.1 vs. 13.6 +/- 1.3 J; Group 3: 12.5 +/- 1.2 vs. 13.3 +/- 1.6 J), and no significant difference between treatment groups was found with a 0.86 power to detect a 5-J difference between groups. Paired pulse width pacing thresholds at 2.8 V were compared in 14 patients. A small increase of 0.02 ms was noted at predischarge testing in patients treated with propafenone and placebo. CONCLUSIONS: Short-term oral propafenone (450 and 675 mg/day) does not significantly affect defibrillation or pacing thresholds. Concomitant use of propafenone in patients with implantable cardioverter-defibrillators with recurrent ventricular or atrial tachyarrhythmias should not interfere with proper device function.

Comparison of dilated cardiomyopathy and coronary artery disease in patients with life-threatening ventricular arrhythmias: Differences in presentation and outcome in the AVID registry.

BACKGROUND: The etiology of structural heart disease in patients with life-threatening arrhythmias (ventricular tachycardia [VT]/ventricular fibrillation [VF]) may define clinical characteristics at presentation, may require that different therapies be administered, and may cause different mortality outcomes. METHODS: In the Antiarrhythmics Versus Implantable Defibrillators (AVID) registry, baseline clinical characteristics, treatments instituted, and ultimate mortality outcomes from the National Death Index were obtained on 3117 patients seen at participating institutions with VT/VF, irrespective of participation in the randomized trial. By use of these data, 2268 patients with coronary artery disease (CAD) were compared with 334 patients with dilated nonischemic cardiomyopathy (DCM). RESULTS: The CAD group was 7 years older and had a higher percentage of males. DCM patients were more likely to be African American, have severely compromised left ventricular function (52% vs 39%), and have a history of congestive heart failure symptoms (62% vs 44%). Patients with CAD were more likely to be treated with b-blockers and calcium channel blockers and less likely to be treated with angiotensin-converting enzyme inhibitors. Patients with DCM were more likely to be treated with diuretics, warfarin, and an implantable cardioverter defibrillator for VT/VF (54% vs 48% for CAD); the use of other antiarrhythmic therapies did not differ between the 2 groups. Two-year survival was not significantly different between the groups (76.6% [95% CI 74.6%-78.7%] vs 78.2% [95% CI 73.6%-82.9%]). CONCLUSIONS: In AVID registry patients with VT/VF, demographic and clinical characteristics were different between patients with CAD and those with DCM. Despite these differences, overall survival was similar in these 2 groups.

Predischarge arrhythmia induction testing of implantable defibrillators may be unnecessary in selected cases.

Complete postoperative evaluation of implantable cardioverter-defibrillators (ICDs) before discharge, including arrhythmia induction, has been the standard since their introduction. Whereas the original ICDs provided little telemetered information and used separate pace-sense and defibrillation leads, modern, third-generation devices provide pace-sense function information in addition to other data and are used in conjunction with integrated transvenous endocardial leads that combine pace-sense and defibrillation function. Changes in lead position, which can potentially result in either an inability to detect fibrillation or to terminate it, should be mirrored by changes in resting pace-sense function. Thus, for newer ICDs implanted with integrated endocardial lead systems, it is possible that in at least some cases predischarge arrhythmia inductions can be avoided. Two hundred patients receiving third-generation ICDs in conjunction with integrated transvenous leads were evaluated before discharge. Defibrillation detection or termination problems were seen in 8. Declines in resting R-wave amplitude and pacing impedance were significantly associated with such complications (-7 +/- 5 vs -0.3 +/- 2.3 mV [p <0.0001] and -158 +/- 138 vs -93 +/- 76 omega [p <0.05], for those with vs without complications, respectively), as were gross right ventricular lead migrations on chest x-ray. No patient with a defibrillation complication had an R-wave change of <3 mV. However, 13% of patients without complications had R-wave changes of >3 mV. It is concluded that a pace-sense evaluation of ICDs may be a satisfactory screen to determine those who need to go on to complete testing with arrhythmia induction in selected cases.

Compatibility of a nonthoracotomy lead system with a biphasic implantable cardioverter-defibrillator. Cadence-Endotak 60-Series IDE investigators.

This prospective multicenter study was conducted under the Food and Drug Administration Investigational Device Exemption to evaluate the safety and efficacy of the combination of the Cadence implantable defibrillator (Ventritex, Inc.) and 60-series Endotak C leads (Cardiac Pacemakers, Inc.). Implantation was attempted in 148 patients with hemodynamically compromising ventricular tachycardia or fibrillation (VF), or with pace-terminable ventricular tachycardia. The system was successfully implanted in 97% of patients, with 96% of implants in a transvenous-lead-alone configuration. At implantation, the defibrillation threshold was 455 +/- 94 V (14 +/- 6 J) for lead-alone patients and 532 +/- 40 V (19 +/- 3 J) for those requiring a subcutaneous patch. VF conversion efficacy was reconfirmed in patients who underwent a 3-month chronic induction study. The system successfully detected all 763 induced arrhythmias and terminated 99.5% of them; after system modification, successful conversion was demonstrated in the 2 patients who initially had induced episodes requiring external defibrillation (1 lead revision; 1 reprogramming). All spontaneous episodes were terminated with an implantable-cardioverter defibrillator. Postshock VF redetection times were significantly shorter than initial detection times (4.5 +/- 1.8 seconds detection, 2.1 +/- 0.7 seconds redetection; p<0.0001). During an 8-month mean follow-up (range 1 to 31 months), 2 unwitnessed deaths were classified as sudden cardiac deaths, and 11 patients experienced a total of 12 complications, none of which was associated with the Cadence-Endotak combination.

Linking phenomenon during atrial stimulation with accessory pathways.

Linking is an electrophysiologic phenomenon in which each successive impulse entering a macroreentry circuit propagates preferentially along 1 limb because of the functional impedance to conduction in the contralateral limb produced by the previous impulse. Electrophysiologic studies were performed in 12 patients with a bidirectionally conducting accessory pathway. Linking was analyzed while 1:1 atrioventricular conduction took place through the normal pathway. When atrial pacing (at the same cycle length) could be initiated during sinus rhythm in patients with rapidly conducting accessory pathways, linking was dynamically maintained by repetitive local refractoriness (interference). When it could be initiated during the usual type of orthodromic circus movement tachycardia, linking was sustained by actual impulse collision, the underlying mechanism having also been called entrainment. When it could be initiated during sinus rhythm in a patient with a slowly conducting accessory pathway, linking was maintained by impulse collision, but the underlying mechanism could not be called entrainment because stimulation had not been started during tachycardia. This study showed that 2 terms--linking and entrainment--may be applied to the same mechanism and, conversely, that the same name could not be used in reference to the same mechanism when pacing was initiated under different circumstances. However, using the proposed conceptual formulation for linking, it is apparent that seemingly diverse mechanisms associated with macroreentry circuits involving accessory pathways are, in fact, variations on a common electrophysiologic theme.

Annihilation, entrainment and modulation of ventricular parasystolic rhythms.

Annihilation and one-to-one entrainment of modulated parasystolic rhythms in humans has not been previously discussed. In 9 nonmedicated patients, it was possible to measure the intrinsic, parasystolic ectopic cycle length given by the intervals between 2 consecutive parasystolic beats without any interposed nonparasystolic beat. The corresponding values varied between 960 and 2,350 ms (corresponding to rates between 62 and 26 beats/min). In addition, modulation could be determined, because nonparasystolic beats falling during the initial 59% of the cycle prolonged the parasystolic cycle length (by 12 to 37.5%), whereas those that fell later in the cycle shortened it (by 9 to 25%). Plotting this prolongation or shortening as a function of the temporal position of the nonparasystolic beats in the cycle yielded biphasic response curves, of which 7 were symmetric and 2 asymmetric. In 2 patients, episodes of concealed one-to-one entrainment were initiated by late nonparasystolic (sinus) beats and, later on, terminated by early ventricular extrasystoles. In 2 other patients (and in 2 separate occasions) nonparasystolic beats, falling in part of the cycle located in between those of maximal delay and acceleration, produced pacemaker annihilation (cessation of automatic activity for the remaining monitoring time). Parasystolic annihilation and concealed entrainment may be one of the causes that can explain the large, spontaneous, day-to-day variability in the incidence of ectopic ventricular beats reported in Holter recordings. Nevertheless, future prospective studies performing interventions that can change the sinus and ectopic rates are required to corroborate our finding.

Concealment of manifest, and exposure of concealed, ventricular parasystole produced by isoproterenol.

Few studies have dealt with the effects of isoproterenol on ventricular parasystole. Intravenous isoproterenol (2 to 4 micrograms/min) was administered to 11 nonmedicated patients with ventricular parasystole. At the onset of the drip infusion, 8 patients had continuous parasystole, 2 had intermittent parasystole, and 1 patient (in whom intermittent parasystole was documented 2 to 5 days earlier) showed no manifest parasystolic activity. In all patients, whose control parasystolic cycle length varied between 960 and 2,530 ms, isoproterenol caused a decrease of the parasystolic cycle lengths ranging from 12 to 36%. Therefore, isoproterenol produced a consistent increase of the parasystolic rate. In 4 patients, parasystolic activity ceased to be manifest when the concomitantly enhanced (by isoproterenol) sinus cycle lengths became shorter than 430 ms. This phenomenon reflected a tachycardia-dependent parasystolic concealment, presumably as a result of interference in the parasystolic-ventricular junction. In every case, the arrhythmia reappeared at its initial rate upon stopping the drip infusion. In no patient did parasystolic ventricular tachycardia develop. In the patient without manifest parasystolic beats, isoproterenol unmasked the intermittent parasystole that previously had been intrinsically manifest. The latter effect reflected a true exposure, or unmasking of a latent, rate-independent concealed, parasystolic focus.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical management of post-myocardial infarction ventricular tachyarrhythmia by myocardial debulking, septal isolation, and myocardial revascularization.

Sustained ventricular tachycardia or ventricular fibrillation, associated with severely depressed left ventricular function after myocardial infarction, carries a poor prognosis. We have used an extensive surgical procedure in 18 patients (15 men and three women) with a mean age of 63 years who had more than three episodes of recurrent, hemodynamically significant ventricular tachycardia or fibrillation and congestive heart failure. The operation consisted of complete myocardial revascularization and myocardial debulking by extensive infarctectomy with unguided endocardial resection and septal isolation with support of the necrotic wall with a Teflon patch. Implantable defibrillator patches were placed in eight patients. Blood cardioplegia and intra-aortic balloon assist (12 patients) were used for perioperative myocardial preservation. Postoperative studies demonstrated a significant increase in ejection fraction (n = 16) and a decline in pulmonary wedge pressure. Hospital mortality was 16% (three patients). Two deaths were due to congestive heart failure and one to arrhythmia. During postoperative electrophysiologic studies, ventricular tachycardia was not inducible in six of eight patients (75%). During a mean follow-up of 24 months, 11 of 15 patients who survived operation are alive and are in New York Heart Association Class I or II. Three of four late deaths were due to congestive heart failure and drug toxicity and one was arrhythmia related. This procedure is effective for preventing recurrent ventricular tachycardia or fibrillation in a majority of patients who cannot have intraoperative mapping.

Automatic implantable cardioverter-defibrillator: techniques of implantation and results.

An initial experience with use of the automatic implantable cardioverter-defibrillator (AICD) is described. Twelve patients received the device. One death has occurred during a mean follow-up of 15 months, and it was due to causes other than arrhythmias. Appropriate device discharge terminating a malignant arrhythmia occurred in 9 patients (75%). The observed survival (92%) far exceeds that to be expected in survivors of sudden death treated by conventional means. There have been no operative deaths. Morbidity has been minimal, although three reoperations were required in 2 patients because of lead dislodgment. The AICD has been demonstrated to be effective in treating patients at risk for sudden arrhythmic death. It can be employed safely with minimum morbidity using a variety of implantation techniques.

Simplified subxiphoid placement of implantable cardioverter defibrillators using a posterior rectus pocket.

A simplified subxiphoid procedure using a single longitudinal epigastric incision and posterior rectus pocket for implantable cardioverter defibrillators was used in 100 patients. Through a single incision, ventricular patches are placed via a transverse pericardiotomy, and a pouch is created behind the rectus abdominis muscle in the left upper quadrant for placement of the implantable cardioverter defibrillator. Patients have minimal discomfort soon after operation, and the implantable cardioverter defibrillator generator is imperceptible to most.

Implantable devices for the treatment of cardiac arrhythmias.

The development of implantable devices for the treatment of tachyarrhythmias has resulted in additional therapeutic choices for the affected patients. Technologic advances now permit one to choose from a wide variety of devices capable of intervening automatically in the presence of supraventricular or ventricular arrhythmias. Although all methods remain in the investigational stage at this time, sufficient evidence has been gathered to support the efficacy of certain devices in the presence of various arrhythmias. Pacemaker-energy pulses may be delivered in various sequences to interrupt re-entrant rhythms, and their reproducible success can be effectively demonstrated in the electrophysiology laboratory. Cardioverting and defibrillating devices are capable of recognizing and successfully interrupting malignant ventricular arrhythmias. The automatic defibrillator has already been reported to reduce 1-year arrhythmic mortality in high-risk patients. Although still in the infant stages of development, the continuing advances in device technology suggest that their future applications are indeed promising.

Unstable intraventricular conduction disorders.

Unstable bundle branch blocks may be tachycardia dependent, bradycardia dependent, or rate independent. When appearing at the "critical" rates or "critical" cycle lengths they may seem to be rate independent. Conversely, "true" rate-independent blocks may be reversible or irreversible. Determining if a rate-unrelated block may disappear can be difficult because irreversile bundle branch block seems to develop through a slow process in time during which rate-dependent, rate-independent, and even normal conduction alternate in successive electrocardiograms.

Indications for and management of cardiac pacemakers.

Cardiac pacemakers are now at the forefront of medical technology. The ability to provide pacing therapy adapted to the individual patient has resulted in significant patient benefit. Although the indications for cardiac pacing have changed little over the past decade, the types of pacemakers available for specific bradyarrhythmias have proliferated in leaps and bounds. This technology is complex and sophisticated and requires in-depth knowledge for appropriate utilization. Artificial replacement of the human conduction system is now a reality. Still other advances remain to be achieved in this area, mainly in sensor technology and pacing therapy for tachyarrhythmias. At the current rate of development, the outlook is indeed promising.

The implantable cardioverter defibrillator: modern implantation techniques and their impact on outcomes.

The implantable cardioverter defibrillator has revolutionized the management of lethal ventricular arrhythmias in susceptible patients. In its second decade of existence, the implantable cardioverter defibrillator has undergone significant technologic enhancements which have resulted in ease of implantation, lower mortality rates, and shorter hospital stays. The newer pectoral size devices have been successfully implanted in a variety of patients, using models from several device manufacturers. Improvements in lead technology have paralleled those of the device itself. These include the unique concept of "unipolar" defibrillation as well as the trend toward dual chamber lead systems. Results of these newer technologies are favorable: comparably low defibrillation thresholds have been reported with the newer lead configurations, with lower operative mortality. However, morbidity attached to earlier lead systems remains as high as 16%. It is anticipated that the results will further improve as shorter transvenous leads and better connector material become routinely available. Finally, the clinical outcomes in the early postoperative phase indicate fewer proarrhythmic effects leading to shorter hospital stays in patient equipped with the latest types of pectoral implants. Continued progress at the level of the patient-device interface is expected to result in every better patient acceptance and proliferation of implantable cardioverter defibrillator therapy.

[Pacing and right atrial ventricular dissociation in auricular stimulation in reciprocal tachycardia using an accessory pathway]. / Entraînement et dissociation oreillette droite-ventricule lors de la stimulation auriculaire au cours des tachycardies réciproques utilisant une voie accessoire.

The effects of right atrial (RA) and coronary sinus (CS) stimulation have been studied in 13 patients with circus movement tachycardia (CMT). Tachycardia entrainment has occurred in all patients during RA pacing and in 11/13 during CS pacing, for a pacing rate 10 to 31 beats faster than the tachycardia rate. During RA pacing, short episodes of right atrial ventricular dissociation (6/13 patients) occurred but not during CS pacing. This can be explained by the anatomical proximity of the CS to the AV node (AVN) or by postulating two separate lateral inputs in the upper part of the AVN. Tachycardia entrainment is a criteria in favor of a reentry mechanism. It delineates a ranges of frequency between tachycardia rate and the slowest possible atrial stimulation rate capable of tachycardia termination which may be benefit for patients with drug resistant CMT, for whom antitachycardia pacemaker is envisaged.