Long-term infection rates associated with the pectoral versus abdominal approach to cardioverter- defibrillator implants

Infection is an uncommon (0% to 6.7%) but serious complication after implantable cardioverter-defibrillator (ICD) implantation. All ICD primary implants, replacements, or revisions performed at the Massachusetts General Hospital between April 1983 and May 1999 were reviewed. A total of 21 ICD-related infections (1.2%) were identified among 1,700 procedures affecting 1.8% of the 1,170 patients who underwent a primary implant, a generator change, or a revision of their systems. The mean follow-up time was 35 +/- 33 months. Of the 959 patients with long-term follow-up, 19 of the 584 patients (3.2%) with abdominal and 2 of the 375 patients (0.5%) with pectoral systems developed ICD-related infections (p = 0.03). There was no significant difference between the infection rate among the 959 primary ICD implants and the 447 replacements or system revisions. Only 5 of the patients (24%) had systemic signs of infection, including fever (T>100.5) and elevated white blood count >12,000. Cultures from the wound revealed staphylococcal species in 16 patients (76%). Nineteen patients were treated with removal of the entire ICD system in addition to intravenous antibiotics for 2 to 4 weeks. A decrease in the incidence of ICD-related infection has occurred since the advent of transvenous pectoral systems. The main organism responsible for ICD infection is Staphylococcus. The mainstay of ICD infection management consists of complete removal of the entire implanted system.

Long-term clinical outcome of patients with prior myocardial infarction after palliative radiofrequency catheter ablation for frequent ventricular tachycardia

Patients with coronary artery disease and hemodynamically tolerated, highly frequent, sustained monomorphic ventricular tachycardia (VT) may undergo radiofrequency catheter ablation (RFCA) for elimination of > or = 1 morphologically distinct VTs. The purpose of this study was to evaluate the long-term clinical benefit following RFCA as a palliative treatment of highly frequent or incessant ischemic VT. Fifty-five patients underwent RFCA of 62 VTs. The target VT was successfully ablated in 82% of patients. Complication and perioperative mortality rates were 7.2% and 1.8%, respectively. At 5 years, total mortality was 51% and probability of freedom from all ventricular tachyarrhythmias was 28%. All patients had highly frequent or incessant drug-refractory VT before RFCA. Clinical benefit was defined as either freedom from all ventricular tachyarrhythmias, or a reduction in frequency of recurrence from > 1 episode per month before RFCA to < or = 1 episode per year of any ventricular tachyarrhythmia, including all appropriate implantable cardioverter defibrillator (ICD) therapies. By this definition, 54% of the patients continued to benefit from RFCA at 5 years. Of 19 variables analyzed with a Cox univariate model, only the presence of a left ventricular aneurysm and a previously implanted ICD were predictive of any ventricular arrhythmia recurrence. However, at 5 years over half of the surviving patients still continued to benefit from RFCA of their clinical VT. Because the overall rate of any ventricular tachyarrhythmia occurrence during follow-up is high, additional protection, such as an ICD, is required.

Changes in health status and quality of life and the impact of uncertainty in patients who survive life-threatening arrhythmias

OBJECTIVE

The purpose of this study was to describe the changes in perception of health status and quality of life from before treatment to 6 months after and the impact of uncertainty on these variables in survivors of life-threatening arrhythmia.

DESIGN AND SETTING

A descriptive correlational design at a large urban teaching hospital.

MEASURES

We measured health status, quality of life, and uncertainty before treatment and 6 months after a life-threatening arrhythmia.

RESULTS

Survivors included 66 men and 15 women, 41 of whom received pharmacologic therapy and 36 of whom received an implantable cardioverter defibrillator (ICD), completed the Medical Outcomes Survey (SF-36), Ferrans and Powers Quality of Life Index (QLI), and the Mishel Uncertainty in Illness Scale (MUIS-C) before treatment and 6 months after. There were significant improvements in the mental and physical health composite summaries as measured by the SF36 (P <.01). Conversely, there were significant reductions in the overall score and specifically in socioeconomic and psychological/spiritual quality of life domains as measured by the QLI (P <.05). An increased perception of uncertainty was related to decreased perception of health status and quality of life at both measurement times, with higher correlations 6 months later.

CONCLUSIONS

Survivors demonstrated improvements in perceived health status, although this did not appear to translate into improvements in the subjective domains of quality of life. The overall quality of life and the domains of psychological/spiritual state and socioeconomic status were lower 6 months after a life-threatening arrhythmia. Uncertainty had a significant impact on these perceptions, identifying an area for nursing interventions.

Mechanism of sustained monomorphic ventricular tachycardia in systemic sclerosis

Three patients with advanced systemic sclerosis and recurrent or incessant monomorphic ventricular tachycardia underwent cardiac electrophysiologic studies. Biventricular transcatheter mapping showed findings most compatible with a reentrant mechanism, which was effectively treated with transcatheter ablation.

Runaway pacemaker in an implantable cardioverter defibrillator

INTRODUCTION

Runaway pacemaker is a potentially catastrophic complication of any permanent pacing system.

METHODS AND RESULTS

A 70-year-old man was found to have erratic behavior of his implantable cardioverter defibrillator (ICD) during a routine outpatient interrogation. His device was turned off, and he was hospitalized in preparation for a pulse generator replacement. During his hospitalization, his ICD unexpectedly began pacing rapidly. Despite prompt resuscitation attempts, the patient died. Postmortem examination of the device demonstrated a crystal oscillator failure.

CONCLUSION

A previously unrecognized component malfunction is a potentially lethal complication of ICDs.

Drug therapy for atrial fibrillation--interactions with interventional therapy and implications for local drug delivery

Multiple therapeutic alternatives, both pharmacological and non-pharmacological, are under active investigation for the treatment of atrial fibrillation. Although many promising approaches are being investigated, there is as yet no universally accepted therapy, nor is there likely to be in the foreseeable future. It is possible that, since no one therapeutic intervention is ideal, a combination of pharmacological and non-pharmacological approaches may succeed in patients in whom neither therapy alone would be effective. In this paper, we explore interactions between devices and antiarrhythmic drugs, as well as novel methods of delivering anti-arrhythmic drug therapy.

Transient right bundle branch block causing R wave attenuation postdefibrillation

Transient and significant decrease in R wave amplitude, associated with transient right bundle branch block, was noted to occur after defibrillation in a defibrillator patient. The mechanism is probably stunning of the right bundle branch, causing right intraventricular conduction delay and decrease in signal amplitude reaching the endocardial sensing dipoles.

The treatment of patients with infected implantable cardioverter-defibrillator systems

OBJECTIVE

The purpose of this study was to evaluate the treatment of patients with infected implantable cardioverter-defibrillator systems.

METHODS

Retrospective analysis was done of the cases of 21 patients treated for implantable cardioverter-defibrillator infection during an 11-year period.

RESULTS

Of 723 cardioverter-defibrillator implantations (550 primary implants, 173 replacements), nine (1.2%) were complicated by early postoperative device-related infections. Late infections developed in two patients 19 and 22 months, respectively, after implantation. Ten other patients were transferred to our institution for treatment of cardioverter-defibrillator infection. The time from implantation to overt infection was 2.2 +/- 1.3 months, excluding the two late infections. The responsible organisms were Staphylococcus aureus (9), Staphylococcus epidermidis (6), Streptococcus hemolyticus (1), gram-negative bacteria (3), Candida albicans (1), and Corynebacterium (1). All patients were treated with intravenous antibiotic drugs. Total system removal was done in 15 patients and partial removal in 2; in 4, the cardioverter-defibrillator system was not explanted. There were no perioperative deaths. A new implantable cardioverter-defibrillator system was reimplanted in 7 patients after 2 to 6 weeks of antibiotic therapy. Ten patients were treated without reimplantation (2 arrhythmia operation, 8 antiarrhythmic drugs). Four patients (3 patients without explantation and 1 with partial system removal) were treated with maintenance long-term antibiotic therapy. During a mean follow-up of 21 +/- 2.8 months, no patient had clinical recurrence of infection. One patient treated with antiarrhythmic drugs without system reimplantation died suddenly.

CONCLUSIONS

Infections that involve implantable cardioverter-defibrillator systems can be safely managed by removing the entire system with reimplantation after intravenous antibiotic therapy. In selected patients in whom the risk for system explantation is high and anticipated life expectancy is short, long-term antibiotic therapy to suppress low-virulence infections may represent an acceptable alternative.

Evolving role of sotalol in the management of ventricular tachyarrhythmias

Sotalol is a unique compound with several potential antiarrhythmic mechanisms, including beta blockade (class II activity), action potential duration prolongation (class III activity), and possibly reduction of QT dispersion. In recent years, trials such as the Cardiac Arrhythmia Suppression Trial (CAST) and the Electrophysiologic Study versus Electrocardiographic Monitoring (ESVEM) trial reported disappointing results with the use of class I agents in the management of ventricular arrhythmias in patients with coronary artery disease. These results have led to increased interest in class III antiarrhythmic agents, including sotalol. Sotalol is effective in suppressing ventricular premature complexes as well as nonsustained and sustained ventricular tachyarrhythmias. The interaction between sotalol and implantable cardioverter-defibrillators (ICDs) is generally favorable. As is the case with other antiarrhythmic drugs, there is no placebo-controlled trial assessing the effect of sotalol on mortality. It is not known if sotalol is more effective than placebo, conventional beta blockade, amiodarone, or ICDs in reducing mortality from life-threatening ventricular arrhythmias. In addition, the optimal method of selecting patients for sotalol therapy has yet to be determined. The safety profile of sotalol has been well established in > 3,000 patients worldwide. Proarrhythmia occurs in approximately 4% of patients, and torsades de pointes occurs in approximately 2.5%. The majority of episodes of torsades de pointes occurs within 3 days of commencing sotalol therapy, and the risk of torsades de pointes increases sharply at dosages > 320 mg daily. It is recommended that initiation of sotalol therapy or dosage increases be performed in a monitored setting. Overall, only 1% of patients enrolled in clinical trials of sotalol discontinued therapy as a result of drug-related congestive heart failure. However, these trials have excluded patients with poor left ventricular systolic function and/or overt heart failure. The optimal management of these patients, who are at greatest risk of sudden cardiac death, and of patients with substrates other than coronary artery disease remains to be elucidated.

Arrhythmias induced by exercise in athletes and others

Athletes are subject to the same arrhythmias as the general population, but the frequency and significance of the arrhythmias may be different. Cardiovascular conditioning slows the heart rate and may make athletes more vulnerable to neurocardiogenic syncope and atrial fibrillation. Tachyarrhythmias may be precipitated by vigorous exercise and more severe rate-related symptoms may result because of the high sympathetic drive during sports activities. For those with pre-existing cardiovascular abnormalities, athletic activity may be beneficial in some cases, but dangerous and even life-threatening in others. A review of the subject and recommendations based on our personal experience and a recent consensus conference are provided.

Sex differences in cardiac arrest survivors

BACKGROUND

Important sex differences in the epidemiology of sudden death and in the results of electrophysiological testing in survivors of cardiac arrest have been identified. These differences are currently poorly understood.

METHODS AND RESULTS

Three hundred fifty-five consecutive survivors of out-of-hospital cardiac arrest (84 women and 271 men) referred for electrophysiologically guided therapy were analyzed retrospectively for sex differences in underlying pathology and predictors of outcome. Women were significantly less likely to have underlying coronary artery disease than men (45% versus 80%) and more likely to have other forms of heart disease or structurally normal hearts (P<.0001). The mean left ventricular ejection fraction was higher in women (0.46+/-0.18 versus 0.41+/-0.18, P<.05), and women were more likely to have no inducible arrhythmia at baseline electrophysiological testing (46% versus 27%, P=.002), although when the patients were stratified by coronary artery disease status, these sex differences were no longer present. The independent predictors of outcome differed between men and women. In men, a left ventricular ejection fraction of <0.40 was the most powerful independent predictor of total (relative risk, 2.8; 95% CI, 1.6 to 5.0; P<.0001) and cardiac (relative risk, 6.3; 95% CI, 2.9 to 13.5; P<.0001) mortality. In contrast, the presence of coronary artery disease was the only independent predictor of total (relative risk, 4.5; 95% CI, 1.5 to 13.4; P=.003) and cardiac (relative risk, 4.4; 95% CI, 1.2 to 15.6; P=.012) mortality in women.

CONCLUSIONS

Females survivors of cardiac arrest are less likely to have underlying coronary artery disease. The predictors of total and cardiac mortality differ between male and female survivors. Coronary artery disease status is the most important predictor in women, and impaired left ventricular function is the most important predictor in men.

Comparison of cycle lengths between induced and spontaneous sustained ventricular tachycardia during concordant antiarrhythmic therapy associated with healed myocardial infarction

We propose that in clinical practice, whenever possible, the VT detection interval should be selected by adding >60 ms to the induced maximal VT cycle length in order to ensure a high sensitivity for the detection of future spontaneous VT episodes.

Influence of the implantable cardioverter/defibrillator on sudden death and total mortality in patients evaluated for cardiac transplantation

BACKGROUND

Implantable cardioverter/defibrillators (ICDs) may reduce sudden tachyarrhythmic death in patients with severe left ventricular dysfunction. It is uncertain whether this improves survival, particularly in patients awaiting cardiac transplantation.

METHODS AND RESULTS

The effect of treatment for spontaneous ventricular arrhythmias (ICD [n = 59], antiarrhythmic drugs [n = 53], or no antiarrhythmic treatment [n = 179]) on total mortality and mode of cardiac death was analyzed in 291 consecutive patients evaluated for cardiac transplantation between January 1986 and January 1995. There were 109 deaths (37.4%) (63 [21.6%] sudden, 40 [13.7%] nonsudden, and 6 [2.1%] noncardiac) during mean follow-up of 15 months (range, 1 to 118 months). Baseline clinical variables, medical therapies for heart failure, and actuarial rates of transplantation were similar between treatment groups. Kaplan-Meier sudden death rates were lowest in the ICD group, intermediate in the no antiarrhythmic treatment group, and highest in the drug treatment group throughout follow-up (12-month sudden death rates, 9.2%, 16.0%, and 34.7%, respectively; P = .004). Total mortality and nonsudden death rates did not differ. Cox proportional-hazards model revealed that antiarrhythmic drug treatment was associated with sudden death (relative risk, 2.1; 95% CI, 1.04 to 3.39; P = .04) and ICD was associated with nonsudden death (relative risk, 2.26; 95% CI, 1.12 to 4.62; P = .02).

CONCLUSIONS

Sudden death rates were lowest in patients treated with ICDs compared with drug treatment or no antiarrhythmic treatment. However, although ICDs reduced sudden death in selected high-risk patients with severe left ventricular dysfunction, the effect on long-term survival was limited, principally by high nonsudden death rates.

Malfunction of implantable cardioverter defibrillators placed by a nonthoracotomy approach: frequency of malfunction and value of chest radiography in determining cause

OBJECTIVE

The purpose of this study was to determine the frequency of system malfunction in patients with nonthoracotomy implantable cardioverter defibrillators and to assess the role of chest radiography in detecting and determining the cause of malfunction.

MATERIALS AND METHODS

The study population consisted of 300 consecutive patients in whom implantable cardioverter defibrillators were implanted using an initial nonthoracotomy approach between September 1990 and October 1994. Transvenous electrodes were placed via the subclavian or cephalic vein under local anesthetic. Intraoperative testing, pulse generator implantation, and, if necessary, subcutaneous patch or extrapericardial patch placement via thoracotomy were done in the operating room under general anesthetic. Follow-up consisted of routine device interrogation every 2-3 months and annual chest radiography. Chest radiographs were obtained more often if patients were symptomatic or if results of device interrogation were abnormal.

RESULTS

Patients were followed up for a mean +/- SD of 19 +/- 14 months following implantation. Implantable cardioverter-defibrillator malfunction occurred in 17 patients (6%) during the follow-up period. Of these, 12 (71%) had component abnormalities on chest radiographs. Patients with radiographically apparent implantable cardioverter-defibrillator abnormalities presented in two discrete time periods after device implantation, early (mean, 35 +/- 14 days) and late (mean, 18 +/- 5 months).

CONCLUSION

Malfunction of nonthoracotomy implantable cardioverter-defibrillator systems develops infrequently after device implantation. In most cases, the cause can be identified on chest radiographs.

Electrocardiographic pseudo-infarct patterns after implantation of cardioverter-defibrillators

Postoperative electrocardiographic (ECG) changes are frequently present after insertion of implantable cardioverter-defibrillators (ICD) and may mimic perioperative myocardial infarction (MI). The purpose of this study was to assess the incidence and clinical significance of postoperative ECG changes in relation to clinical, laboratory, and implantation data. In 25 (16%) of 156 patients undergoing ICD implantation, significant ECG changes (> or = 50% reduction in R-wave amplitude in > or = 3 leads or new Q waves in > or = 2 leads) were present 1 to 3 days after the operation and persisted at hospital discharge in 12 (8%). Presence of thoracotomy, the total number of induced ventricular fibrillation episodes, and the number of defibrillation shocks required during defibrillation threshold (DFT) testing correlated with postoperative ECG changes. Other factors associated with a significant R-wave loss in the lateral precordial leads included left-sided pleural effusion, lung infiltrates or atelectasis, and large defibrillator patch electrodes over the left ventricle or the lateral chest wall. Myocardial necrosis documented by elevated cardiac enzymes occurred in 6 (5%) of 151 patients without significant ECG changes and in 3 (12%) with (p value not significant). However, postoperative ECG changes associated with elevated enzymes were indistinguishable from changes unrelated to necrosis. Therefore the sensitivity and specificity of the surface ECG for detection of MI after ICD placement is poor. Multiple factors such as thoracotomy, myocardial injury from DFT testing, electric insulation, or shielding of the heart may contribute to the development of electrocardiographic pseudo-infarct patterns.

Implantation of transvenous nonthoracotomy cardioverter-defibrillator systems in patients with permanent endocardial pacemakers

Among 177 patients in whom a nonthoracotomy approach was initially used to implant a cardioverter-defibrillator system, 11 (6%) patients also received a separately implanted permanent pacemaker. The main problem encountered in these patients were previously implanted unipolar pacemakers (n = 3) and ventricular pacing leads positioned at the right ventricular apex, the latter interfering with optimal placement of the tripolar implantable cardioverter-defibrillator (ICD) lead (n = 9). The approaches used to solve these problems were individualized and included placement of the ICD sensing lead at the right ventricular outflow tract (n = 3), initial placement (n = 1) or subsequent repositioning (n = 2) of the right ventricular pacing lead at the outflow tract, upgrade from unipolar to bipolar systems (n = 2), reprogramming from the DDD to AAI mode (n = 2), inactivation of the pacemaker (n = 1), and simultaneous placement of a single-chamber atrial pacemaker with the ICD lead (n = 2). These revisions fulfilled the pacing needs in each patient and prevented unfavorable sensing interaction between the two systems.

Three-year outcome of a nonthoracotomy approach to cardioverter-defibrillator implantation in 189 consecutive patients

To date, no long-term clinical data have been published in patients undergoing a nonthoracotomy approach to cardioverter-defibrillator system implantation. In the present report, 189 consecutive patients prospectively underwent a standardized approach to cardioverter-defibrillator system implantation in which the nonthoracotomy configurations were tested first. If satisfactory defibrillation thresholds were not obtained, thoracotomy was performed during the same intraoperative session. A nonthoracotomy system was successfully implanted in 149 of 189 patients (79%), with a higher success rate (90%) observed in patients who had more recent implantations. The overall rate of complications associated with these systems was low (11%). Over a mean follow-up of 12.5 +/- 9.3 months, 17 patients (9%) died. Three-year total, cardiac, and sudden death-free actuarial survival for all patients was 83 +/- 11%, 88 +/- 7%, and 94 +/- 2%, respectively. Three-year sudden death-free actuarial survival was higher in the nonthoracotomy than in the thoracotomy patients (97 +/- 2% vs 87 +/- 6%, p = 0.047), although total survival was similar (77 +/- 11% vs 83 +/- 7%, p = 0.77). These data suggest that a majority of patients (> 80%) requiring a cardioverter-defibrillator system can undergo implantation using a nonthoracotomy approach. Patients receiving nonthoracotomy systems have 3-year outcomes comparable to those implanted via thoracotomy. If these results are maintained, a nonthoracotomy approach will supplant thoracotomy-implanted systems as the preferred method because of the simpler implant procedure and lower overall cost involved.

Operation for recurrent ventricular tachycardia. Predictors of short- and long-term efficacy

The success of ventricular operation in ablating drug-refractory ventricular tachycardia secondary to ischemic heart disease varies with surgical technique, the presence of certain identified risk factors, and patient selection biases. Forty-eight patients with drug-refractory ventricular tachycardia secondary to ischemic heart disease underwent directed ventricular operation. All patients had previous myocardial infarction, and 46 of 48 patients had a left-ventricular aneurysm. Mapping was done in 81% of patients. Patients underwent a combination of subendocardial resection, aneurysmectomy, and cryoablation. The operative mortality rate was 8%. Age greater than 65 years was the only risk factor for operative mortality. Forty-one patients underwent postoperative programmed electrical stimulation. In 26 patients (63%) tachycardia was noninducible, whereas it was inducible in 15 patients (37%). Stepwise logistic regression identified septal and inferior focus location as the most significant predictors of outcome. Septal focus location was a significant (p = 0.008) predictor of surgical success whereas inferior focus location was a significant (p = 0.015) predictor of surgical failure. Other identified independent risk factors for surgical failure were (1) use of cardioplegia, (2) lack of a completed intraoperative endocardial map, and (3) decreased ejection fraction. This generated model to predict success or failure had a sensitivity of 93.3% and a specificity of 92.4%. The success of ventricular operation is affected by the presence of certain risk factors. In the management of those patients at high risk for failure, other surgical options such as the placement of implantable cardioverter-defibrillator electrode patches at the time of ventricular operation or the alternative placement of a palliative implantable cardioverter-defibrillator should be considered.

Treatment of ventricular tachycardia by transcatheter radiofrequency ablation in patients with ischemic heart disease

BACKGROUND

Recurrent sustained ventricular tachycardia (VT) is not responsive to antiarrhythmic drugs in the majority of patients, who therefore need therapy with nonpharmacological methods. We evaluated prospectively the feasibility, safety, and efficacy of transcatheter radiofrequency (RF) ablation of VT in 21 selected patients with ischemic heart disease and VT.

METHODS AND RESULTS

Twenty-one patients with ischemic heart disease and recurrent, drug-refractory VT documented by 12-lead ECG were selected who had sufficient hemodynamic tolerance of VT to undergo transcatheter mapping. Documented clinical VT was reproduced by programmed cardiac stimulation (PCS), and the site of origin was localized by a combination of techniques, including pace mapping, activation-sequence mapping, recordings of middiastolic potentials, and application of resetting and entrainment principles. RF current at 55 V was applied (3.8 +/- 3.1 applications per patient) for as long as 30 seconds at a time to target sites. Twenty-four distinct clinical VTs (mean cycle length, 445 +/- 52 milliseconds) were mapped and ablated in 21 patients. In 17 of 21 patients (81%), the procedure was acutely successful, and the target clinical VT could no longer be induced by PCS after the procedure, whereas in 4 patients, clinical VT remained inducible. By contrast, VTs with shorter cycle length and different QRS morphology than the ablated VT could still be induced by PCS in 12 of 21 patients. One patient died in intractable congestive heart failure 10 days after the procedure, and the remaining 20 are alive at the end of the follow-up period. The majority of the patients continued to be treated with at least one additional mode of antiarrhythmic therapy; 12 patients were still taking antiarrhythmic drugs, and 9 patients received an implantable cardioverter/defibrillator. During a mean follow-up period of 13.2 +/- 5.0 months, 9 of 20 patients (45%) had recurrent VT. In 4 patients, the recurrent VT was different than the previously ablated one. Clinical VT recurred in all 4 patients in whom RF ablation had been acutely unsuccessful. Four patients with recurrent VT underwent repeat RF ablation procedures that were acutely successful and had no further recurrence.

CONCLUSION

Transcatheter RF ablation is feasible but has only moderately high efficacy in a small, selected group of patients with ischemic heart disease and drug-refractory, highly frequent, hemodynamically tolerated, sustained VT. In the majority of the patients, this treatment technique is palliative rather than definitive, and many of the patients continue to require other methods of antiarrhythmic therapy.

Analysis of the initiation of spontaneous monomorphic ventricular tachycardia by stored intracardiac electrograms

OBJECTIVES

This study was designed to analyze stored intracardiac electrograms generated during spontaneous monomorphic ventricular tachycardia to examine the possible mechanisms responsible for the initiation of ventricular tachycardia in a group of postinfarction patients.

BACKGROUND

Implantable cardioverter-defibrillators capable of storing electrograms during an arrhythmic event provide an intracardiac electrogram analog to Holter ambulatory electrocardiographic monitoring. Such electrograms are of value in arrhythmia diagnosis and in determining the appropriateness of implantable cardioverter-defibrillator therapy and may aid in understanding the initiation of ventricular arrhythmias.

METHODS

We studied 73 stored electrograms in 22 postinfarction patients with spontaneous monomorphic ventricular tachycardia. Premature depolarizations before tachycardia were classified by morphology and number. Electrogram morphology was compared with the morphology of the baseline rhythm and ventricular tachycardia. Prematurity was assessed by the coupling interval and a calculated prematurity ratio.

RESULTS

During baseline rhythm, ectopic activity was present in 30 (41%) of 73 stored episodes. Ventricular tachycardia was preceded by a short-long-short sequence in 14% of episodes and by a rapid ventricular rhythm in 5.5% of episodes. The onset of ventricular tachycardia was marked by single premature depolarizations in 33 episodes (45%), by pairs in 16 (22%) and by multiple complexes in 24 (33%). Morphology was similar to that of the ensuing tachycardia in 35 episodes (48%). The mean coupling interval was 364 ms, and the mean prematurity ratio was 0.56. In all 10 episodes (14%) where the prematurity ratio was < 0.40, a short-long-short sequence was responsible. When classified by morphology, the mean prematurity ratio of depolarizations dissimilar to ventricular tachycardia (0.53) was significantly less than that of the morphologically similar group (0.60, p = 0.035).

CONCLUSIONS

In this select group of postinfarction patients with recurrent sustained monomorphic ventricular tachycardia treated with implantable cardioverter-defibrillators, ventricular tachycardia was most often preceded by late-coupled premature depolarizations. Not infrequently, a short-long-short sequence occurred before tachycardia. Premature depolarizations with a morphology different from that of the tachycardia occurred earlier in the cardiac cycle than did those with a morphology similar to that of the tachycardia. These findings may reflect different mechanisms of ventricular tachycardia initiation.

Determinants of successful nonthoracotomy cardioverter-defibrillator implantation: experience in 101 patients using two different lead systems

OBJECTIVES

This study was conducted to identify the determinants of successful nonthoracotomy cardioverter-defibrillator implantation.

BACKGROUND

Until recently, either median sternotomy or thoracotomy was necessary to implant the electrodes used for internal cardioverter-defibrillator systems. A number of manufacturers have developed nonthoracotomy lead systems comprising two transvenous coil electrodes and a subcutaneous patch electrode. At present, the factors associated with the success or failure of a nonthoracotomy approach are unknown.

METHODS

A total of 101 consecutive patients requiring a cardioverter-defibrillator underwent an initial nonthoracotomy approach. Factors associated with successful nonthoracotomy implantation were prospectively determined.

RESULTS

A nonthoracotomy system was implanted in 72 (71%) of 101 patients. Twenty-nine patients (29%) required thoracotomy. Univariate predictors of successful nonthoracotomy implantation included smaller cardiac size (p < 0.0001), smaller cardiothoracic ratio (p < 0.0002), QRS duration < 120 ms (p = 0.003), female gender (p = 0.006), ventricular fibrillation as the presenting arrhythmia (p = 0.03) and smaller echocardiographic left ventricular size (p = 0.04). Multivariate predictors included smaller cardiac size (p < 0.002) and female gender (p < 0.007). Total actuarial survival over a mean (+/- SD) follow-up interval of 12 +/- 7 months was 91 +/- 0.03% and was not different in the thoracotomy and nonthoracotomy groups.

CONCLUSIONS

A nonthoracotomy cardioverter-defibrillator system can be implanted in a majority of patients. Smaller cardiac size and female gender are associated with a high probability of successful implantation.

Influence of implantable cardioverter-defibrillators on the long-term prognosis of survivors of out-of-hospital cardiac arrest

BACKGROUND

Survivors of out-of-hospital cardiac arrest not associated with acute myocardial infarction are at high risk for recurrent cardiac arrest and sudden cardiac death. The impact of the implantable cardioverter-defibrillator on long-term prognosis in these patients is uncertain.

METHODS AND RESULTS

Three hundred thirty-one survivors of out-of-hospital cardiac arrest (age, 56 +/- 13.7 years) underwent electrophysiologically guided therapy. Implantable defibrillators were placed in 150 patients (45.3%), and 181 patients (54.7%) received pharmacological and/or surgical therapy alone. Left ventricular ejection fraction was 35.2 +/- 16.6% in defibrillator recipients and 45.3 +/- 18.2% in nondefibrillator patients. Median patient follow-up was 24 months in the defibrillator group and 46 months in the nondefibrillator group. In a proportional hazards model, the independent predictors of total cardiac mortality were left ventricular ejection fraction of less than 0.40 (relative risk, 4.55; 95% confidence interval, 2.44 to 8.33; P = .0001), absence of an implantable defibrillator (relative risk, 2.70; confidence interval, 1.41 to 5.00; P = .017), and persistence of inducible sustained ventricular tachycardia (relative risk, 1.84; 95% confidence interval, 0.97 to 3.49; P = .045). The 1- and 5-year probabilities of survival free of cardiac mortality in patients with left ventricular ejection fraction of less than 0.40 were 94.3% and 69.6% with a defibrillator and 82.1% and 45.3% without a defibrillator, respectively. For patients with left ventricular ejection fraction of 0.40 or more, the 1- and 5-year probabilities of survival free of cardiac mortality were 97.7% and 94.6% with a defibrillator and 95.4% and 86.9% without a defibrillator, respectively.

CONCLUSIONS

In survivors of out-of-hospital cardiac arrest, the implantable defibrillator is associated with a reduction in cardiac mortality, particularly in patients with impaired left ventricular function.

Successful implantation of cardioverter-defibrillator systems in patients with elevated defibrillation thresholds

OBJECTIVES

. The purpose of this study was to conduct a retrospective analysis of 16 patients with high initial defibrillation thresholds in whom a three-electrode system was used to lower defibrillation thresholds and permit implantation of a cardioverter-defibrillator system.

BACKGROUND

Patients with high defibrillation thresholds (> 25 J) are uncommon but may be problematic to physicians implanting cardioverter-defibrillator systems. Most conventional systems use two defibrillating electrodes, most commonly two epicardial patches. When defibrillation thresholds remain elevated despite extensive testing of a two-electrode system, a third electrode can be incorporated and tested. However, few published data exist on the use of a three-electrode system in patients with high defibrillation thresholds.

METHODS

After failure to achieve satisfactory defibrillation thresholds < 25 J with a two-patch electrode system, a third electrode was incorporated and tested. In all cases, two electrodes were joined to form a common cathode or anode, while a single electrode was used as the opposite polarity electrode. Various three-electrode configurations were then tested.

RESULTS

In all 16 patients, satisfactory defibrillation thresholds were achieved and a cardioverter-defibrillator was implanted (95% confidence interval [CI] = 0% to 21%). The mean final defibrillation threshold using the revised three-electrode system was 19.5 +/- 3.7 J (p < 0.0001). A mean of 6 +/- 3 electrode configurations/patient were tested before the final configuration was selected. A total of nine different electrode configurations were used in the 16 study patients; the most common of these incorporated left and right ventricular patches as combined cathode and a superior vena cava coil (n = 5) or right atrial patch electrode (n = 3) as single anode.

CONCLUSION

Patients with high initial defibrillation thresholds can generally undergo successful cardioverter-defibrillator implantation with a three-electrode system if enough electrode configurations are tested after a third electrode is incorporated.

Efficacy of a tiered therapy defibrillator system used to treat recurrent ventricular arrhythmias refractory to drugs

OBJECTIVE

To evaluate an implantable tiered therapy defibrillator system that delivered antitachycardia pacing treatment for slower well tolerated ventricular tachycardias and cardioversion or defibrillation for fast tachycardias or ventricular fibrillation.

METHODS

A tiered treatment device (Ventritex Cadence V-100) was implanted in 30 patients with ventricular tachycardia that was refractory to drugs. Efficacy was evaluated by the responses of induced or spontaneous arrhythmias to the treatments delivered.

RESULTS

Antitachycardia pacing successfully terminated 80% of episodes of ventricular tachycardia induced by non-invasive programmed stimulation, but acceleration was brought about by pacing in six patients in 10% of episodes. During a follow up of two to 17 (mean seven) months, 18 patients (60%) had recurrence of ventricular arrhythmias. Antitachycardia pacing terminated ventricular tachycardia in 17 of 18 patients in 87% of episodes. Twelve patients received shocks for ventricular tachycardia or fibrillation. Failure of pacing, with subsequent cardioversion, occurred in nine patients (50%) in one or more episodes. Acceleration of tachycardia by pacing occurred in 10 patients in 5% of episodes. Only two of these patients had experienced acceleration of previously induced arrhythmia. Five patients had spontaneous fast ventricular tachycardia or fibrillation treated by cardioversion or defibrillation. Spurious treatment was delivered in nine patients (30%), during atrial fibrillation in five, sinus tachycardia in two, and because of fracture of the sensing lead system in two patients. The retrieval of stored intracardiac electrograms was of clinical value in assessing spurious treatment.

CONCLUSIONS

Tiered treatment was effective in terminating recurrent ventricular arrhythmias in these selected patients. Most episodes were treated successfully by pacing, and resistant tachycardias, pacing induced acceleration, or haemodynamically compromising arrhythmias were treated by shocks.

Prospective evaluation of day-to-day reproducibility of upright tilt-table testing in unexplained syncope

To evaluate the day-to-day reproducibility of upright tilt-table testing, 109 patients with unexplained syncope prospectively underwent testing on 2 consecutive days using a uniform protocol. Results of testing on 2 separate days were concordant in 69 of 109 patients (63%), and discordant in 40 of 109 patients (37%). Thirty-six of 109 patients (33%) had vasodepressor syncope on 1 or both days of testing. Nineteen of 30 patients (63%) with vasodepressor responses on the first day did not reproduce this response during the second day of testing. An additional 6 patients with an initial negative tilt test had a vasodepressor response on the second day. Only 11 of 36 patients (31%) had reproducible vasodepressor responses on both days of testing. Patients with reproducible vasodepressor responses had a significantly higher mean number of preceding clinical syncopal events than patients with 2 normal tests (p < 0.02) or nonreproducible results (p < 0.04). In addition, these patients had a significantly longer duration of clinical symptoms relative to patients with 2 tests that yielded negative results (p < 0.008) and nonreproducible results (p < 0.01). The elapsed time between the most recent clinical event and the performance of tilt-table testing was not significantly different among the 3 groups, and did not appear to influence the outcome of testing. These data show that vasodepressor responses elicited by upright tilt-table testing show day-to-day variability in many patients, a finding that may limit the interpretation of initial and follow-up test results.

Low energy conversion of atrial fibrillation in the sheep

OBJECTIVES

In this study, the feasibility, efficacy and safety of low energy internal atrial cardioversion were investigated in a sheep model. The relation between the level of energy used for atrial defibrillation and the probability of successful cardioversion was examined.

BACKGROUND

Atrial fibrillation is a common clinical arrhythmia that frequently recurs after termination with high energy external cardioversion. In some patients with drug-refractory and poorly tolerated atrial fibrillation, an automatic implantable cardioverter may prove useful by providing rapid restoration of sinus rhythm.

METHODS

In 16 pentobarbital-anesthetized sheep, a right atrial spring electrode was implanted percutaneously and a left thoracic cutaneous patch electrode was placed on the thorax. Sustained atrial fibrillation was induced by rapid atrial pacing and terminated by biphasic cathodal shocks synchronized to the R wave of the surface electrocardiogram (ECG).

RESULTS

During 768 defibrillation attempts in 16 sheep, the percent of successful cardioversion attempts increased in a dose-response manner, reaching a plateau at the average energy level of 5 J. With greater than or equal to 1.5 and greater than or equal to 2.5 J energy levels, cardioversion was achieved, respectively, in greater than 50% and greater than 80% of attempts. Ventricular fibrillation occurred in 18 (2.4%) of 768 cardioversion attempts; in all 18 cases, the shock was poorly synchronized with the ECG R wave.

CONCLUSIONS

Low energy cardioversion of atrial fibrillation to sinus rhythm is feasible with use of a right atrial spring/cutaneous patch electrode configuration. The percent of successful cardioversion attempts depends on the level of energy output, and there is a risk of ventricular fibrillation if cardioversion is poorly synchronized with ventricular depolarization.

Adenosine and the treatment of supraventricular tachycardia

Adenosine has recently become widely available for the treatment of paroxysmal supraventricular tachycardia. In order to evaluate its role in the management of arrhythmias, we have reviewed the literature on the cellular mechanisms, metabolism, potential for adverse effects, and clinical experience of the efficacy and safety of intravenous adenosine. Adenosine produces transient atrioventricular nodal block when injected as an intravenous bolus. This is of therapeutic value in the conversion to sinus rhythm of the majority of paroxysmal supraventricular tachycardias, which involve the atrioventricular node in a re-entrant circuit. The mean success rate was 93% from over 600 reported episodes. Compared with other antiarrhythmic agents, adenosine is remarkable for its rapid metabolism and brevity of action, with a half-life of a few seconds. It commonly produces subjective symptoms, particularly chest discomfort, dyspnea, and flushing, which are of short duration only. No serious adverse effect has been reported. Arrhythmias may recur within minutes in a minority of patients. Comparative studies have shown that adenosine is as effective as verapamil in the treatment of supraventricular tachycardia, and has less potential for adverse effects. Patients with supraventricular tachycardia should initially be treated using vagotonic physical maneuvers. Immediate electrical cardioversion is indicated if the arrhythmia is associated with hemodynamic collapse. Adenosine is the preferred drug in those patients in whom verapamil has failed or may cause adverse effects, such as those with heart failure or wide-complex tachycardia. The safety profile of adenosine suggests that it should be the drug of first choice for the treatment of supraventricular tachycardia, but only limited comparative data to support this view are available at present.

Electrophysiologic response to moricizine in patients with sustained ventricular arrhythmias

OBJECTIVE

To assess the short-term efficacy and safety of moricizine in patients receiving electrophysiologically guided therapy for sustained ventricular arrhythmias refractory to treatment with class IA antiarrhythmic agents.

DESIGN

Uncontrolled clinical trial.

SETTING

Referral-based teaching medical center.

PATIENTS

Twenty-one patients (18 of whom had coronary artery disease) with a mean left ventricular ejection fraction of 32% +/- 11% who presented with sustained ventricular tachycardia (13 patients), syncope (4 patients), or cardiac arrest (4 patients).

INTERVENTIONS

Moricizine, 743 +/- 85 mg daily.

MEASUREMENTS

Electrophysiologic testing in the drug-free state and after administration of moricizine unless sustained arrhythmias occurred.

MAIN RESULTS

Sustained ventricular tachycardia was inducible in the absence of antiarrhythmic drugs in 20 patients and was not suppressed by moricizine in any patient. Four patients had six episodes of spontaneous ventricular tachycardia while receiving moricizine. A probable proarrhythmic response occurred in four patients.

CONCLUSION

In patients with compromised left ventricular function caused by coronary artery disease in whom class IA antiarrhythmics were ineffective, moricizine was ineffective in suppressing sustained ventricular arrhythmias and resulted in proarrhythmic effects in some patients.

Current treatment of patients surviving out-of-hospital cardiac arrest

Most out-of-hospital cardiac arrests result from the sudden onset of a sustained ventricular arrhythmia in the absence of a new myocardial infarction. Individuals who survive cardiac arrest are at high risk for recurrent arrhythmias and sudden unexpected death. To prevent recurrent cardiac arrest, effective treatment must be provided during hospitalization after the initial episode. Caring for the survivor of cardiac arrest requires a detailed clinical investigation to define the underlying cardiac anatomy and left ventricular function and to elucidate the mechanism and characteristics of the patient's arrhythmia. Appropriate antiarrhythmic therapy, such as drugs or a nonpharmacological intervention (eg, implantable cardioverter-defibrillator), is then selected based on these considerations. In addition, ischemia is treated aggressively with beta-adrenergic blocking agents and, when appropriate, with surgical coronary artery revascularization.

Usefulness of sotalol in suppressing ventricular tachycardia or ventricular fibrillation in patients with healed myocardial infarcts

The electrophysiologic effects and antiarrhythmic efficacy of oral sotalol were investigated in 42 patients with coronary artery disease and prior myocardial infarction who presented with ventricular tachycardia (VT), ventricular fibrillation (VF) or syncope. The mean left ventricular ejection fraction was 36 +/- 9%. Baseline programmed cardiac stimulation initiated sustained VT (26 patients) or VF (16). The induced arrhythmia was not suppressed by conventional antiarrhythmic drugs in any patient (3 +/- 2 trials/patient). The mean daily dosage of sotalol was 221 +/- 84 mg. The right ventricular effective refractory period increased from 247 +/- 25 to 273 +/- 26 ms with sotalol (p = 0.0001) and the corrected QT interval increased from 431 +/- 35 to 456 +/- 62 ms (p = 0.02). Arrhythmia suppression was defined as no sustained VT or VF in response to programmed cardiac stimulation using up to 3 extrastimuli. Induced VT or VF was suppressed by sotalol therapy in 10 (24%) patients (group 1). Group 1 patients had faster induced arrhythmias at the baseline study than patients whose induced ventricular arrhythmia was not suppressed (group 2). The mean left ventricular ejection fraction tended to be higher in group 1 patients (p = 0.07). Fourteen patients (including 9 group 1 patients) continued receiving sotalol after discharge. In 2 group 2 patients, sotalol was combined with a class IA antiarrhythmic drug. During a mean follow-up period of 7.9 +/- 4.9 months, 2 patients had recurrent VT and in 2 others sotalol was discontinued due to side effects.

Treatment of ventricular arrhythmias

Within the past 20 years, our knowledge concerning the epidemiology, natural history, and treatment of VT has expanded greatly. A variety of effective pharmacologic, surgical and electrical therapies for VT are now available to the clinician. Patients who present with ventricular tachyarrhythmias should undergo a comprehensive medical evaluation directed at identifying and treating such factors as ischemia, congestive heart failure, valvular heart disease, sensitivity to cardioactive drugs, and metabolic derangements. Many patients who present with asymptomatic ventricular arrhythmias do not require specific antiarrhythmic drug therapy. However, certain patients who have already suffered a life-threatening arrhythmia or who are at high risk for such arrhythmia should be vigorously treated with specific antiarrhythmic therapy guided for that individual patient. The efficacy of any antiarrhythmic treatment should be assessed by ECG monitoring, exercise testing, and/or electrophysiologic study. In the near future, potentially revolutionary new electrical therapies for ventricular tachyarrhythmias will be evaluated. It is to be hoped that these devices used in combination with pharmacologic and surgical therapies may dramatically reduce the incidence of sudden cardiac death in high-risk patients.

The effect of potassium ion depletion on postinfarction canine cardiac arrhythmias

The effect of potassium ion (K+) depletion on postmyocardial infarction ventricular arrhythmias was investigated in 32 dogs: 12 control animals, 10 animals that ate a diet extremely low in K+ for 15 days, and 10 others that, in addition to dietary K+ deprivation, received 50 mg of hydrochlorothiazide four times. The experimental myocardial infarction was created by proximal left anterior descending coronary artery ligation. In a subgroup of 24 animals selected for relatively uniform size of myocardial infarction (14% to 22% of left ventricular mass), eight animals with mean cumulative K+ balance of -4.01 +/- 2.19 meq/kg developed spontaneous ventricular fibrillation within 4 to 17 min of coronary ligation, whereas 16 animals with a mean cumulative K+ balance of -0.11 +/- 1.82 meq/kg didn't. By univariate analysis cumulative K+ deficit (p = .001) and plasma K+ concentration (p = .039) correlated significantly with spontaneous ventricular fibrillation. Multivariate analysis of the entire population of 32 animals identified cumulative K+ deficit and size of myocardial infarction as the only independent predictors of ventricular fibrillation. Cumulative K+ deficit was also an independent predictor of ventricular fibrillation induced by programmed cardiac stimulation in the conscious state 1 day after myocardial infarction.