Comparison of d,l-sotalol and implantable defibrillators for treatment of sustained ventricular tachycardia or fibrillation in patients with coronary artery disease

Anesthetic Implications for Patients With Implantable Cardioverter Defibrillators

Implantable cardioverter defibrillators have become one of the preferred methods for treating many life- threatening ventricular arrhythmias. Many tens of thou sands of these devices have been implanted and this, together with the ease of worldwide travel, has made it more likely that anesthesiologists everywhere may come into contact with these patients either for elective or emergency surgery. These patients present unique anesthetic challenges because of the combination of the device and severe underlying cardiac disease. This article presents an overview of the implantable defibril lator as it affects the anesthesiologist, including device function, device assessment, electromagnetic interfer ence, and perioperative management.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy

Arrhythmogenic right ventricular dysplasia (ARVD/C) is one cause of death in young adults in the United States, representing approximately 17% of all ARVD/C cases reported. This study presents 2 cases of ARVD/C diagnosed at a central Texas hospital and reviews the literature regarding this disease. The diagnosis, histology, presentation, prognosis, and therapy are addressed because the rare nature of this disease within the United States makes diagnosis and treatment difficult and creates problems of adaptation for the patient. Clinicians must become more familiar with this potentially fatal cardiac disorder that can create vulnerability within a young adult population.

Role of Antiarrhythmic Therapy in Patients at Risk for Sudden Cardiac Death: An Evidence-Based Review

Sudden cardiac death (SCD) accounts for more than half of all cardiac deaths occurring each year in the United States. Although it has several causes, patients at greatest risk are those with coronary artery disease and impaired left ventricular function, heart failure secondary to ischemia or idiopathic dilated cardiomyopathy, hypertrophic cardiomyopathy, documented sustained ventricular tachycardia or ventricular fibrillation, and survivors of cardiac arrest. The presence of asymptomatic ventricular arrhythmias, positive signal-averaged electrocardiogram (ECG), low heart rate variability index, or inducible ventricular tachycardia or ventricular fibrillation increases the risk. In primary prevention trials in patients with ischemic heart disease, beta-blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among class III agents, d,l-sotalol and dofetilide have a neutral effect on mortality, whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death and cardiac arrest. Three primary prevention trials in patients with ischemic heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricular arrhythmias, and inducible ventricular tachycardia or ventricular fibrillation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythmic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. In those with heart failure, beta-blockers reduced total and SCD mortality, but dofetilide and amiodarone had a neutral effect on mortality. In the secondary prevention of SCD, antiarrhythmic drugs alone generally are not thought to improve survival. In three trials in patients with documented sustained ventricular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs reduced cardiac and arrhythmic mortality. Total mortality, however, was significantly reduced in only one of these trials. The role of antiarrhythmic drugs in secondary prevention of SCD is limited to patients in whom ICD is inappropriate or in combination with ICD. Antiarrhythmics can be given selectively with ICDs to decrease episodes of ventricular tachycardia or fibrillation to reduce ICD discharges, to suppress episodes of nonsustained ventricular tachycardia that trigger ICD discharges, to slow the rate of ventricular tachycardia to increase hemodynamic stability, to allow effective antitachycardia pacing, or to suppress supraventricular arrhythmias.

Infarct related artery patency: relation to serial electropharmacological studies and outcome in patients with previous myocardial infarction and ventricular tachyarrhythmias

Evidence suggests that infarct related artery (IRA) patency may improve survival after acute myocardial infarction, which is thought to be partially due to a lower incidence of malignant ventricular tachyarrhythmias. However, little is known about the effect of IRA patency on antiarrhythmic drug response and long-term outcome in patients with previous infarction who already experienced sustained ventricular tachyarrhythmias. A total of 152 patients with remote myocardial infarction and documented ventricular tachycardia (VT) or ventricular fibrillation (VF) underwent coronary angiography and programmed ventricular stimulation before and after oral administration of d,l-sotalol (240-640 mg/day). D,l-sotalol suppressed inducibility of VT/VF in 37 (25.2%) patients. The IRA was patent in 38.1% of all patients. There was no significant difference in the frequency of drug response between patients with patent or occluded IRAs (26.8% vs 24.2%, P = 0.87). In patients with a patent IRA, d,l-sotalol tended to be more effective in the absence of a left ventricular aneurysm, although this difference did not reach statistical significance (P = 0.38). Ejection fraction and collateral blood flow had no effect on drug response in the presence or absence of IRA patency. During follow-up (13.0 +/- 19.9 months) of 29 patients discharged on oral d,l-sotalol, 3 patients experienced symptomatic VT and 4 sudden death. Arrhythmia recurrence and death of all cause (n = 6) and cardiac death (n = 4) were independent of IRA patency status. IRA patency had no effect on short-term drug response to d,l-sotalol in patients with remote myocardial infarction and documented VT/VF. Long-term outcome of patients with sustained ventricular tachyarrhythmias is independent of IRA patency status. In contrast to a previous report, outcome of electropharmacological testing was not predicted by the patency of the IRA.

Drug therapy of sustained ventricular tachyarrhythmias. Is there still a role?

This article provides a review of the risks faced by patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) in the absence of a reversible or transient cause so that the goals of therapy can be clearly defined. The therapeutic approaches that have been proposed to achieve these goals are outlined and evidence comparing these various approaches to therapy is then summarized in order to propose an algorithm for the optimal use of antiarrhythmic drug therapies as primary therapy for selected VT/VF patients. Options for the ancillary uses of antiarrhythmic drug therapies in ICD patients are considered.

Implantable devices versus antiarrhythmic drug therapy in recurrent ventricular tachycardia and ventricular fibrillation

The implantable cardioverter defibrillator (ICD) protects patients from sudden cardiac death due to ventricular tachyarrhythmias. The capability of an improved overall survival of high-risk patients in comparison to the best pharmacologic therapy has been evaluated over the last few years in prospective randomized trials. In patients with a history of resuscitated ventricular fibrillation (VF) or unstable ventricular tachycardia (VT), the ICD was superior to therapy with amiodarone in 3 large trials involving 2,024 patients. At 2-year follow-up, ICD therapy was associated with a relative reduction in the risk of death of 20% to 30%. With respect to primary prevention of arrhythmogenic death, data are less convincing. The Multicenter Automatic Implantable Defibrillator (MADIT) study proved superiority of ICD therapy over medical treatment in coronary patients with depressed left ventricular function, nonsustained VT, and inducible but not suppressible sustained VT/VF. The second trial, the Coronary Artery Bypass Graft (CABG)-Patch trial, failed to show a similar superiority in 900 patients with an ejection fraction of < or = 35% and an abnormal signal-averaged electrocardiograph undergoing coronary artery bypass grafting. Thus, the role of device therapy for primary prevention of sudden death has not been established. Future prospective studies are needed to clarify this issue.

Predicting the effect of D,L-sotalol on ventricular tachycardia inducibility from the RR variability response

AIM

To find a rapid way of identifying non-responders to D, L-sotalol in patients with ventricular tachycardia.

METHODS

Programmed ventricular stimulation and RR variability were studied in the control state and 10 days after treatment with 160 to 320 mg of D,L-sotalol in 36 consecutive patients with ventricular tachycardia.

RESULTS

In 14 patients (group I) D,L-sotalol suppressed ventricular tachycardia inducibility. In 22 patients (group II) sustained ventricular tachycardia remained inducible during D,L-sotalol treatment. The ventricular tachycardia rate was slowed in eight patients and unchanged or accelerated in 14. At baseline, heart rate variability was similar in both groups. During treatment with D,L-sotalol, variables reflecting parasympathetic activity (pNN50, rMSSD, and high frequency amplitude (HF)) increased in both groups: HF increased from (mean (SD)) 75 (68) to 146 (134) in group I (p < 0.05) and from 60 (49) to 125 (79) in group II (p < 0.05). Other variables were unchanged in group I. In group II, the variables associated with sympathetic activity (coefficient of variance (CV), ratio of low frequency amplitude (LF) to HF) decreased significantly: CV decreased from 13 (4) to 9 (2) (p < 0. 001) and LF/HF from 4.74 (3.02) to 3.00 (2.02) (p < 0.05).

CONCLUSIONS

The beta blocking effect of D,L-sotalol produced a significant improvement over control values in indices of parasympathetic tone in all treated patients. However, the heart rate variability indices related to sympathetic activity were decreased only in non-responders. This effect of D,L-sotalol on heart rate variability could help detect non-responders to the drug and avoid an electrophysiological study.

Sudden Cardiac Death

Great strides have been made in the approach to the management of sudden cardiac death. Patients who have been successfully resuscitated from an episode of sudden cardiac death are at high risk of recurrence. Much larger groups of patients who have not had episodes of sudden cardiac death are also at substantial risk for this event, however. Because the survival rates associated with out-of-hospital cardiac arrest are dismal, these high-risk populations must be targeted for prophylaxis. Beta-blockers have been shown to be an effective pharmacologic therapy in patients who have had myocardial infarction and, most recently, in patients with congestive heart failure. When possible, these agents should be used in these populations. No class I or class III antiarrhythmic drugs, with the possible exception of amiodarone, have been shown to have efficacy as prophylactic agents for the reduction of mortality in these populations. In patients who have hemodynamically significant sustained ventricular tachyarrhythmias or an aborted episode of sudden cardiac death, the current therapy of choice is an implantable cardioverter-defibrillator (ICD). For prophylaxis of sudden cardiac death in patients who have not had a previous event, several approaches may be considered. Currently, the best therapeutic approach for prophylaxis of sudden cardiac death seems to be the ICD; however, use of this device can be justified only in patients at substantial risk of sudden cardiac death. Defining the high-risk populations that will benefit from ICDs is critical in managing the problem of sudden cardiac death.

Comparison of the long-term efficacy of implantable defibrillators and sotalol for documented spontaneous sustained ventricular tachyarrhythmias secondary to coronary artery disease

BACKGROUND

The relative efficacy of antitachycardia pacing implantable cardioverter defibrillators (ATPICD) and sotalol in the treatment of ventricular tachyarrhythmias is controversial.

AIM

To compare the mortality in patients treated with ATPICD and sotalol for documented spontaneous sustained ventricular tachyarrhythmias occurring late after previous myocardial infarction.

METHODS

In this non-randomised retrospective study of 139 consecutive patients all patients had inducible ventricular tachycardia at baseline electrophysiological studies. Before the availability of ATPICD, 22 patients were treated with sotalol as part of a randomised study comparing the efficacy of sotalol to amiodarone. After ATPICD became available sotalol was used in 49 patients in whom intravenous testing predicted sotalol to be effective and ATPICD were implanted in 68 patients in whom sotalol was predicted to be ineffective at electrophysiological testing. Thus, 68 patients were treated with an ATPICD and 71 with sotalol.

RESULTS

The two groups were well-matched for age, type of presenting arrhythmia, severity of coronary artery disease and ventricular function. At 36 months Kaplan-Meier estimates of mortality from ventricular tachyarrhythmia were 0% with ATPICD and 15% with sotalol (p=0.03). Kaplan-Meier estimates of total mortality at 36 months were 12% with ATPICD and 25% with sotalol (p=0.09). Multivariate analysis showed hazard ratio of 7.9 (p=0.06) for death from ventricular tachyarrhythmia in patients treated with sotalol compared to ATPICD.

CONCLUSIONS

While no difference in total mortality was demonstrated, treatment with ATPICD is probably superior to sotalol for preventing deaths due to ventricular tachyarrhythmia.

Antiarrhythmic drugs or implantable cardioverter defibrillators in heart failure: the "poor heart"

Ventricular tachycardia and ventricular fibrillation account for a substantial proportion of all deaths in patients with heart failure. Of currently available therapies, amiodarone and the implantable cardioverter defibrillator (ICD) appear to have the greatest potential to decrease sudden death in heart failure. In this article, the presently available information on the relative role of antiarrhythmic drugs, with a focus on amiodarone and ICDs in heart failure, is reviewed.

A preview of implantable cardioverter defibrillator systems in the next millennium: an integrative cardiac rhythm management approach

The implantable cardioverter defibrillator (ICD), a primary therapeutic option for preventing sudden cardiac death, has rapidly evolved since being introduced clinically in 1980. Technologic advances in several key areas have enabled ICDs to provide more sophisticated rhythm management. Recent emphasis has been placed on dual-chamber ICDs possessing adaptive-rate pacing capabilities. Adoption of dual-chamber ICD systems has been rapid. The capabilities of future ICD systems will be governed by an integrative strategy that brings together sets of features specifically targeted at multifaceted rhythm disorders. The addition of atrial therapy will require more sophisticated rhythm discrimination algorithms. ICD technology will improve on several fronts including leads, integrated circuits, batteries, and capacitors. Additionally, state-of-the-art pacemaker technology will continue to be incorporated into ICDs. As these new ICD systems become increasingly sophisticated from an engineering viewpoint, tremendous emphasis will be placed on decreasing the complexity of programming, device interrogation, and patient monitoring during routine patient follow-up. Vast improvements in ICD programming systems may ultimately permit the 1-minute follow-up.

Suppression of sustained ventricular tachyarrhythmias: a comparison of d,l-sotalol with no antiarrhythmic drug treatment

OBJECTIVES

This study evaluates the clinical efficacy of d,l-sotalol in patients with sustained ventricular tachyarrhythmias.

BACKGROUND

D,l-sotalol is an important antiarrhythmic agent to prevent recurrences of sustained ventricular tachyarrhythmias (VT/VF). However, evidence is lacking that an antiarrhythmic agent like d,l-sotalol can reduce the incidence of sustained ventricular tachyarrhythmias in comparison to no antiarrhythmic drug treatment.

METHODS

A prospective study was performed in 146 consecutive patients with inducible sustained ventricular tachycardia or ventricular fibrillation. In 53 patients, oral d,l-sotalol prevented induction of VT/VF during electrophysiological testing and patients were discharged on oral d,l-sotalol (sotalol group). In 93 patients, VT/VF remained inducible and a defibrillator (ICD) was implanted. After implantation of the device patients were randomly assigned to oral treatment with d,l-sotalol (ICD/sotalol group, n=46) or no antiarrhythmic medication (n=47, ICD-only group).

RESULTS

During follow-up, 25 patients (53.2%) in the ICD-only group had a VT/VF recurrence in comparison to 15 patients (28.3%) in the sotalol group and 15 patients (32.6%) in the ICD/sotalol group (p=0.0013). Therapy with d,l-sotalol, amiodarone or metoprolol was instituted in 12 patients (25.5%) of the ICD-only group due to frequent VT/VF recurrences or symptomatic supraventricular tachyarrhythmias. In nine patients, 17% of the sotalol group, an ICD was implanted after VT/VF recurrence, three patients (5.7%) received amiodarone. Total mortality was not different between the three groups.

CONCLUSIONS

D,l-sotalol significantly reduces the incidence of recurrences of sustained ventricular tachyarrhythmias in comparison to no antiarrhythmic drug treatment.

Comparison of metoprolol and sotalol in preventing ventricular tachyarrhythmias after the implantation of a cardioverter/defibrillator

The purpose of this prospective study was to evaluate, on an intention-to-treat basis, the efficacy of d,l-sotalol and metoprolol with regards to the recurrence of arrhythmic events after implantable cardioverter defibrillator (ICD) implantation. After ICD implantation, 70 patients were randomly assigned to treatment with either metoprolol (mean dosage 104+/-37 mg/day in 35 patients) or d,l-sotalol (mean dosage 242+/-109 mg/day in 35 patients). During follow up ventricular tachycardia (VT), fast VT, and ventricular fibrillation (VF) episodes were calculated. Metoprolol treatment led to a marked reduction in the recurrence of arrhythmic events. Actuarial rates for absence of VT recurrence at 1 and 2 years were significantly higher in the metoprolol group compared with the d,l-sotalol group (83% and 80% vs 57% and 51%, respectively, p=0.016). The actuarial rates for absence of fast VT or VF were 80% in the metoprolol group compared with 46% in the d,l-sotalol group (p=0.002). During a follow up of 26+/-16 months, there were 3 deaths in the metoprolol group compared with 6 deaths in the d,l-sotalol group. Actuarial rates of overall survival were not significantly different in the 2 groups (91% vs 83%, p=0.287). In this prospective, randomized, controlled study the recurrence rate of ventricular tachyarrhythmias in patients treated with metoprolol was lower than in patients treated by d,l-sotolol.

The search for novel antiarrhythmic strategies. Sicilian Gambit

The past fifty years of antiarrhythmic drug development have seen limited success in prolonging life and reducing morbidity. It is likely that arrhythmias are in most instances final common pathways through which changes in the cardiac substrate and in trigger mechanisms are expressed. We propose that the development and administration of therapies for the arrhythmias themselves, while offering a panacea for a disease entity that has evolved and is being overtly manifested, is also an admission of failure to identify and prevent evolution of the substrate and triggers such that arrhythmias can occur. We suggest that while strategies for treatment and prevention of recurrence of arrhythmias still warrant exploration, greater hope for the future lies in identifying means for earlier diagnosis of the arrhythmogenic substrate and triggers, and in developing therapies that are "upstream" to the arrhythmia and prevent their initial expression. Means to achieve this end are suggested, using specific arrhythmias as examples. Similarly, to increase the likelihood that clinical studies of new therapies can be successfully concluded and interpreted, we suggest new approaches to patient selection, risk stratification, trial endpoints, outcome events and trial methodologies.

Antiarrhythmic drugs and devices for the management of ventricular tachyarrhythmia in ischemic heart disease

Ischemic heart disease is the most frequent cardiac abnormality in patients with sustained or nonsustained ventricular tachyarrhythmias. The goals of therapy in such patients are to decrease the severity and incidence of symptoms and prolong life. In this article, we review the current views on antiarrhythmic drug therapy and an implantable cardioverter-defibrillator (ICD) in patients with ischemic heart disease. The importance of beta blockade as part of the therapy is emphasized. In addition, the superiority of sotalol and amiodarone over class I drugs, the benefits of combined treatment with amiodarone and a beta blocker, and the impact and limitations of current trials comparing the effectiveness of drug therapy with that of an ICD are all considered. Also discussed is the combined use of an antiarrhythmic drug and an ICD. In this approach sotalol is generally the agent of choice, with amiodarone the second choice.

A decade of clinical trial developments in postmyocardial infarction, congestive heart failure, and sustained ventricular tachyarrhythmia patients: from CAST to AVID and beyond. Cardiac Arrhythmic Suppression Trial. Antiarrhythmic Versus Implantable Defibrillators

Multiple trials using antiarrhythmic drugs, pharmacologic therapy, and implantable cardioverter defibrillators have been performed in an attempt to improve survival in patients: (1) postmyocardial infarction; (2) with congestive heart failure, with and without nonsustained ventricular tachycardia; and (3) with sustained ventricular tachycardia and those who have survived an out-of-hospital cardiac arrest. This article reviews some of the key findings and limitations of completed and ongoing trials. We also make recommendations for the current treatment of such patients based on the results of these trials.

Polymorphic ventricular tachyarrhythmias in the absence of organic heart disease: classification, differential diagnosis, and implications for therapy

Different polymorphic ventricular tachyarrhythmias may cause syncope or cardiac arrest in patients with no heart disease: (1) Catecholamine-sensitive polymorphic ventricular tachycardia (VT) presents during childhood: the hallmark is the reproducible provocation of atrial and polymorphic ventricular arrhythmias during exercise, despite a normal QT. Beta-blockers are the treatment of choice. (2) In the long QT syndromes (LQTS), malfunction of ion channels leads to prolonged ventricular repolarization, early afterdepolarizations, and triggered ventricular arrhythmias. Therapeutic options include: beta-blockers, genotype-specific therapy, cardiac sympathetic denervation, and implantation of pacemakers or defibrillators. (3) The "short-coupled variant of torsade de pointes" is a malignant disease that shares several characteristics with idiopathic ventricular fibrillation. Although verapamil is frequently recommended, mortality rates remain high. (4) Idiopathic ventricular fibrillation (VF) with normal electrocardiogram (ECG) strikes young adults of both genders. In contrast to other polymorphic tachyarrhythmias, idiopathic VF is not generally related to stress. Also, familial involvement is rare. Therapeutic options include implantation of defibrillators and therapy with class 1A drugs. (5) The "Brugada syndrome" and the "syndrome of nocturnal sudden death" strike males almost exclusively. Right bundle branch block (RBBB) with ST elevation in the right precordial leads-the "Brugada sign"--is seen in the ECG of both patient populations. Implantation of defibrillators is recommended.

Body surface potentials during discharge of the implantable cardioverter defibrillator

INTRODUCTION

Little is known about the hazard for persons in contact with patients experiencing a high-voltage discharge of their implantable cardioverter defibrillator (ICD). Compared to epicardial systems, this risk may be increased with transvenous electrode systems and particularly in active can configurations.

METHODS AND RESULTS

In 23 patients with a transvenous active can ICD system, body surface potentials Vs and current through an external resistance were measured during 35 discharges. Vs was detected using skin electrodes positioned over the left subpectorally implanted pulse generator [C], apex of the heart [A], and the right pectoral region [RP]. Mean Vs during discharges without an external shunt resistance ranged between 13 and 63.8 V [C to A] and 12.5 to 47.3 V [C to RP] (ICD peak stored/output voltage Vcap = 183 to 606 V, n = 20). Mean current flow [C to A] was 8.2 to 46.8 mA (Vcap = 288 to 633 V, n = 10) and 42 to 120.7 mA (Vcap = 447 to 579 V, n = 5) across a resistance of 1,696 and 797 omega, respectively.

CONCLUSION

During high-output shocks, a considerable potential difference is present on the body surface of ICD patients that, according to the literature, may induce a single cardiac response in a bystander. Analogous to spontaneous extrasystoles, there is only a minimal chance of triggering a tachyarrhythmia by this stimulated extra beat. Direct induction of ventricular fibrillation is unlikely, since reported fibrillation threshold values are much higher than the observed magnitudes of current and voltage.

[Current indications for implantable automatic defibrillators]

Since the first implantation in man in 1980 implantable cardioverter defibrillator technology has greatly improved and the number of devices implanted has increased considerably in recent years. Non-thoracotomy lead systems and biphasic shocks are now the approach of choice, offering nearly a 100% success rate. This paper version reviews the current indications for the implantation of implantable cardioverter defibrillator and is an upgraded of an article previously published by the Arrhythmia's Section of the Spanish Society of Cardiology. Recommendations for qualification of centres implanting defibrillators and follow up are also addressed.

Antiarrhythmic therapy--future trends and forecast for the 21st century

This article discusses recent changes in antiarrhythmic therapy, with a focus on nonpharmacologic therapy (electrode catheter ablation, implantable cardioverter-defibrillators [ICDs]), and puts them into perspective for the coming years. The treatment of supraventricular tachycardias and tachycardia involving accessory pathways is likely to remain the domain of catheter ablation. With promising new techniques under investigation, the spectrum of arrhythmias that can be cured will probably be expanded. Treatment of life-threatening ventricular arrhythmias is likely to remain the domain of the ICD in the foreseeable future. With the safety net of the ICD in place, new antiarrhythmic drugs or other forms of antiarrhythmic therapy can be developed and tested.

Drugs versus devices in controlling ventricular tachycardia, ventricular fibrillation, and recurrent cardiac arrest

Patients with symptomatic ventricular tachycardia, ventricular fibrillation, or aborted sudden cardiac death remain at high risk for arrhythmia recurrence. In recent years, strategies to treat these patients have changed. Concerns about the proarrhythmia risk and uncertain efficacy of class I agents have resulted in a shift in interest to non-class I antiarrhythmic drugs such as sotalol and amiodarone. Both drugs have class III antiarrhythmic properties (i.e., both lengthen repolarization and refractoriness); however, each also has its own additional electrophysiologic effects. Prospectively designed, randomized studies have shown that both sotalol and amiodarone have more potent antiarrhythmic actions than class I agents. However, even as the advantages of sotalol and amiodarone have been recognized, enthusiasm for nonpharmacologic modes of treatment, particularly the implantable cardioverter-defibrillator (ICD), has also markedly increased. The ICD has been shown to decrease dramatically the incidence of sudden death, which may lead to the reduction of total mortality. Whether patients with life-threatening ventricular tachyarrhythmias should be treated first with antiarrhythmic agents or with an ICD is an important question. The results of recent studies suggest that treatment with an ICD is more effective than electrophysiologically guided treatment with class I agents. However, results of prospectively designed randomized studies comparing the efficacy of the ICD with that of sotalol and amiodarone must become available before definitive recommendations can be made concerning the use of the ICD as first-line therapy in patients with ventricular tachycardia/ventricular fibrillation or aborted sudden cardiac death. In addition, there may be a significant role for the use of antiarrhythmic drugs in conjunction with ICDs.

Inappropriate discharge of an implantable cardioverter defibrillator during atrial flutter and intermittent ventricular antibradycardia pacing

INTRODUCTION

Inappropriate discharges of an implantable cardioverter defibrillator (ICD) are troublesome to the patient and sometimes a difficult task for the physician trying to identify and treat the cause.

METHODS AND RESULTS

For the first time, we report a mechanism of inappropriate ICD discharges during episodes of atrial flutter with a slow ventricular response and intermittent antibradycardia pacing. The episodes occurred in two patients and were triggered by the unique sensing algorithm of the Ventritex Cadence V-100 in combination with the tripolar CPI Endotak 072 transvenous defibrillation lead, which provides integrated bipolar sensing.

CONCLUSION

Besides treatment of the underlying arrhythmia, reprogramming of the device, an electrode position far away from the atria, and true bipolar sensing will enhance the performance of ICD systems with respect to the episodes described here. In addition, more flexible sensing algorithms may, in the future, prevent this overall rare complication.

[The current status of implantable automatic defibrillators]

The implantable cardioverter defibrillator has become an important therapy for patients with sustained or life threatening ventricular arrhythmias. Although the concept for the implantable cardioverter defibrillator originated in the late 1960s, the first device was implanted in humans in 1980. Since then, the technology has improved rapidly the design, function and reliability of the devices have been greatly modified. There are currently five companies dealing with defibrillators in Spain incorporating multiple options in defibrillation, pacing and sensing capabilities. New devices with atrioventricular pacing and atrial defibrillation possibilities will soon become available. The purpose of this article is to review the principal functions of implantable cardioverter defibrillators currently available.

Efficacy and safety of d,l-sotalol in patients with ventricular tachycardia and in survivors of cardiac arrest

OBJECTIVE

The aim of this study was to assess the antiarrhythmic efficacy and safety of d,l-sotalol in patients with ventricular tachycardia (VT) or ventricular fibrillation (VF) and in survivors of cardiac arrest and to identify the factors that are associated with arrhythmia suppression and therefore might be helpful in predicting drug efficacy.

BACKGROUND

Despite increasing use of the class III antiarrhythmic agent d,l-sotalol, data on its short- and long-term efficacy in a large patient cohort are lacking. Information on its long-term tolerability and safety is limited.

METHODS

A total of 396 patients with inducible sustained VT or VF (VT/VF) underwent programmed stimulation before and after receiving oral d,l-sotalol (240 to 640 mg/day). Patients in whom VT/VF was rendered either noninducible or more difficult to induce (more extrastimuli or faster drive cycle length needed for VT/VF induction) were discharged on a regimen of oral d,l-sotalol.

RESULTS

d,l-Sotalol suppressed VT/VF in 151 patients (38.1%) and rendered the arrhythmia more difficult to induce in 76 patients (19.2%). The extent of drug-induced prolongation of right ventricular refractoriness and a shorter VT cycle length at baseline were independent predictors of immediate drug efficacy. Torsade de pointes developed in seven patients (1.8%). Two hundred ten patients (53%) continued to receive d,l-sotalol and were followed up for 34 +/- 18 months (mean +/- SD). The actuarial rates for the absence of arrhythmic recurrence (either VT/VF or sudden death) at 1 and 3 years were 89% and 77%, respectively. Actuarial rates for overall survival at 1 and 3 years were 94% and 86%, respectively. VT/VF suppression by d,l-sotalol was an independent discriminant variable that separated patients with and without arrhythmia recurrence. However, noninducibility of VT/VF did not predict freedom from sudden death.

CONCLUSION

Oral d,l-sotalol is effective and safe in patients with VT/VF. However, sudden cardiac death develops in a significant proportion of patients, and programmed stimulation seems to be of limited value for its prediction.

The AVID trial: evidence based or randomized control trials--is the AVID study too late? Antiarrhythmics Versus Implantable Defibrillators

A great body of clinical evidence has been accumulated--before and without the AVID trial--showing that implantable defibrillators prolong life better than currently available antiarrhythmic drugs. With this evidence already available, we question the validity of a trial that attempted, in effect, to place a price tag on life and quality of life.

The ESVEM trial: impact on treatment of ventricular tachyarrhythmias. Electrophysiologic Study Versus Electrocardiographic Monitoring

The ESVEM (Electrophysiologic Study Versus Electrocardiographic Monitoring) trial was a prospective, randomized study, initiated in 1983, to compare the outcome of patients in whom antiarrhythmic therapy was guided by serial electrophysiological study with the outcome of patients in whom therapy was guided by electrocardiographic monitoring. In a surprising finding, there was no difference in rates of arrhythmia recurrence or mortality between the two methods. Subsequent reanalyses using more stringent criteria for both methods or a combined assessment have not significantly improved the predictive accuracy of guided therapy. Because drug therapy in each limb was also randomized, a comparison of specific antiarrhythmic agents was also possible: sotalol therapy and the absence of previous antiarrhythmic drug therapy were associated with a reduction in arrhythmia recurrence. Survey data suggest that the results of this trial have influenced clinical practice.

Estrogens and atherosclerosis

Estrogens prevent heart disease in women and have also been shown to retard atherogenesis in animal models. Estrogens may act at several steps in the atherogenic process to prevent cardiovascular disease. Some of the benefits of estrogens can be ascribed to their ability to favorably alter the lipoprotein profile, i.e. increase high-density lipoprotein and decrease low-density lipoprotein, and also to their ability to prevent oxidative modification of low-density lipoprotein. Other beneficial effects of estrogens include direct actions on the vascular endothelium and vascular smooth muscle, leading to a decrease in the expression of adhesion molecules involved in monocyte adhesion to endothelial cells, and to a decrease in certain chemokines involved in monocyte migration into the subendothelial space. Estrogens may also affect the later stages of atherogenesis. Finally, estrogens may modify the behavior of atherosclerotic vessels by altering their reactivity and thereby promoting vasodilation, and this may also partly account for their ability to prevent clinical events due to cardiovascular disease.

Drugs or implantable cardioverter-defibrillators in patients with poor left ventricular function?

Poor left ventricular function is a predictor of sudden death. Both antiarrhythmic drugs and implantable cardioverter-defibrillators (ICDs) promise to reduce the sudden death rate in these patients and consequently improve survival. In patients without spontaneous ventricular tachyarrhythmias, only beta-blocking agents and amiodarone have been shown to reduce sudden death and improve survival in some studies, whereas class I antiarrhythmic drugs increased mortality. For patients with documented ventricular tachyarrhythmias, protection against sudden death by serially tested class I antiarrhythmic drugs is at best moderate. There is some evidence suggesting that therapy with class III antiarrhythmic drugs, either amiodarone or dl-sotalol, may reduce sudden death rates and improve overall mortality in comparison to therapy with class I antiarrhythmic drugs. ICDs have been shown to prevent sudden death reliably. In published patient cohorts in which only patients who were not inducible off antiarrhythmic drugs or still inducible on antiarrhythmic drugs received an ICD, the ICD seemed to improve overall survival in comparison to class I antiarrhythmic drugs. A small prospective randomized study that compared a conventional therapy strategy to primary ICD implantations showed an improved outcome with ICDs as therapy of first choice. However, these studies included many patients treated with class I antiarrhythmic drugs considered to be less effective. In matched control studies comparing the ICD to amiodarone or dl-sotalol, less sudden deaths and an improved overall survival could be shown for the ICD in general without stratification for left ventricular function. Thus, in patients with hemodynamically nontolerated ventricular tachyarrhythmias, the ICD seems to improve survival in comparison to class I antiarrhythmic drugs, dl-sotalol, or amiodarone. However, in patients with poor left ventricular function, therapy with ICDs seems to be less cost-effective than in patients with preserved left ventricular function. In patients with very poor left ventricular function who are evaluated for cardiac transplantation, the ICD seems to change only the mode of death from sudden to a nonsudden cardiac death if transplantation cannot be performed soon.