The ESVEM trial. Electrophysiologic Study Versus Electrocardiographic Monitoring for selection of antiarrhythmic therapy of ventricular tachyarrhythmias. The ESVEM Investigators

Antiarrhythmic Drugs for Atrial Fibrillation: Selected Features of Ventricular Repolarization That Facilitate Proarrhythmic Torsades de Pointes and Favor Inpatient Initiation

The management approaches to patients with atrial fibrillation (AF) include rhythm-control strategies for those patients who are symptomatic despite rate control and for selected others in whom sinus rhythm is necessary for reasons beyond current symptoms (including commercial pilots, those who are felt likely to develop symptoms as comorbidities progress, and more). First-line therapies among the rhythm-control options are antiarrhythmic drugs (AADs). For many AADs, their initiation in-hospital is either a requirement or strongly advised- especially when the patient is in AF. This article explores some of the rationale behind this requirement to give clinicians a better understanding of the reasons for this undesired inconvenience.

Role of Imaging in the Management of Ventricular Arrhythmias

The management of ventricular arrhythmias (VA) has evolved over time to an advanced discipline, incorporating many technologies in the diagnosis and treatment of the myriad types of VA. The first application of imaging is in the assessment for structural heart disease, as this has the greatest impact on prognosis. Advanced imaging has its greatest utility in the planning and execution of ablation for VA. The following review outlines the application of different imaging modalities, such as ultrasonography, magnetic resonance imaging, computed tomography, and positron emission tomography, for the treatment of VA.

Reflections on the early invasive clinical cardiac electrophysiology era through fifty manuscripts: 1967-1992

In 1967, researchers in The Netherlands and France independently reported a new technique, later called programmed electrical stimulation. The ability to reproducibly initiate and terminate arrhythmias heralded the beginning of invasive clinical cardiac electrophysiology as a medical discipline. Over the next fifty years, insights into the pathophysiologic basis of arrhythmias would transform the field into an interventional specialty with a tremendous armamentarium of procedures. In 2015, the variety and complexity of these procedures were major reasons that led to the recommendation for an increase in the training period from one year to two years. The purpose of this manuscript is to present fifty manuscripts from the early invasive clinical cardiac electrophysiology era, between 1967 and 1992, to serve as an educational resource for current and future electrophysiologists. It is our hope that reflection on the transition from a predominantly noninvasive discipline to one where procedures are commonly utilized will lead to more thoughtful patient care today and to inspiration for innovation tomorrow. In the words of the late Dr. Mark E. Josephson, "It is only by getting back to the basics that the field of electrophysiology will continue to grow instead of stagnate."

A modified approach for programmed electrical stimulation in mice: Inducibility of ventricular arrhythmias

BACKGROUND

Electrophysiological studies in mice, the prevailing model organism in the field of basic cardiovascular research, are impeded by the low yield of programmed electrical stimulation (PES).

OBJECTIVE

To investigate a modified approach for ventricular arrhythmia (VA) induction and a novel scoring system in mice.

METHOD

A systematic review of literature on current methods for PES in mice searching the PubMed database revealed that VA inducibility was low and ranged widely (4.6 ± 10.7%). Based on this literature review, a modified PES protocol with 3 to 10 extrastimuli was developed and tested in comparison to the conventional PES protocol using up to 3 extrastimuli in anesthetized wildtype mice (C57BL/6J, n = 12). Induced VA, classified according to the Lambeth Convention, were assessed by established arrhythmia scores as well as a novel arrhythmia score based on VA duration.

RESULTS

PES with the modified approach raised both the occurrence and the duration of VA compared to conventional PES (0% vs 50%; novel VA score p = 0.0002). Particularly, coupling of >6 extrastimuli raised the induction of VA. Predominantly, premature ventricular complexes (n = 6) and ventricular tachycardia <1s (n = 4) were observed. Repeated PES after adrenergic stimulation using isoprenaline resulted in enhanced induction of ventricular tachycardia <1s in both protocols.

CONCLUSION

Our findings suggest that the presented approach of modified PES enables effective induction and quantification of VA in wildtype mice and may well be suited to document and evaluate detailed VA characteristics in mice.

The Use of Ambulatory Electrocardiography in the Emergency Medicine Ward to Assess Patients with Symptoms Possibly Related to Cardiac Arrhythmia: A Sharing of Experience in a Local Hospital

Ambulatory electrocardiography (AECG) or Holter has a long history of use in patients with suspected symptomatic arrhythmia. In Hong Kong, patients with AECG monitoring were entirely under the care of internal medicine in the past. This report described a pioneer trial on the use of AECG in a local emergency setting under the supervision of emergency physicians. A departmental guideline for AECG use on suitable patients was drawn up and patients underwent AECG monitoring in the emergency medicine ward. The AECG results were reported preliminarily by emergency physicians and then confirmed with additional comments by cardiologists. This report presented the clinical features, AECG results and clinical outcomes of all patients recruited from the start of the protocol in May 2008 to July 2009.

Treatment of Ventricular Arrhythmias and Use of Implantable Cardioverter-Defibrillators to Improve Survival in Older Adult Patients with Cardiac Disease

Ventricular arrhythmia (VA) and sudden cardiac death (SCD) are well-recognized problems in the overall heart failure population, but treatment decisions can be more complex and nuanced in older patients. Sustained VA does not always lead to SCD, but identifies a higher risk population and may cause significant symptoms. Antiarrhythmic drugs (AAD) and catheter ablation are the mainstays for prevention of VA, but have not been shown to improve mortality. The value of implantable cardiac defibrillators (ICDs) may be influenced by patient age. This article discusses long-term treatment of VA and the use of ICDs in the elderly.

Medical therapy to prevent recurrence of ventricular arrhythmia in normal and structural heart disease patients

INTRODUCTION

Recurrent ventricular arrhythmias (VA) are a source of significant morbidity in patients without structural heart disease (SHD) and also mortality in patients with SHD. The treatment goals for these two patient populations differ greatly. Areas covered: The secondary prevention of recurrent VA in patients without and with SHD will be reviewed, focusing on clinical data (especially randomized, controlled trials) in the literature as determined through searches in PubMed and ClinicalTrials.gov. This will include β blockers, non-dihydropyridine calcium channel blockers and antiarrhythmic drugs in both subgroups and non-antiarrhythmic medications in SHD. Expert commentary: The available options for medical therapy for VA in both normal hearts and SHD are insufficient, due to substandard efficacy and toxicities. While non-pharmacologic therapies may provide an excellent option, further drug development and randomized trials are needed, as is a reappraisal of the current mode of utilization.

Effect of corticosteroid therapy on ventricular arrhythmias in patients with cardiac sarcoidosis

BACKGROUND

Ventricular arrhythmias are one of the main causes of sudden death in cardiac sarcoidosis (CS). Little is known about the efficacy of corticosteroid therapy for ventricular arrhythmias in CS.

METHODS

Thirty-one CS patients presenting premature ventricular contractions (PVCs, ≥300/day) were investigated. Fourteen patients had nonsustained ventricular tachycardia (NSVT). All of patients were treated with corticosteroid, and the initial dosage is 30 mg/day of prednisone, which was tapered over a period of 6 months to a maintenance dosage of 10 mg/day. Twenty-four hour Holter monitoring, signal averaged electrocardiography (SAECG), echocardiography, gallium-67 scintigraphy, serum angiotensin converting enzyme (ACE) and plasma B-type natriuretic peptide (BNP) concentrations were assessed before and after corticosteroid therapy.

RESULTS

As a whole, there were no significant differences in the number of PVCs and in the prevalence of NSVT before and after steroid therapy. However, the less advanced LV dysfunction patients (EF ≥ 35%, n = 17) showed significant reduction in the number of PVCs (from 1820 ± 2969 to 742 ± 1425, P = 0.048) and in the prevalence of NSVT (from 41 to 6%, p = 0.039). Late potentials on SAECG were abolished in 3 patients. The less advanced LV dysfunction group showed a significantly higher prevalence of gallium-67 uptake compared with the advanced LV dysfunction group (EF < 35 %, n = 14). In the advanced LV dysfunction patients, there were no significant differences in these parameters.

CONCLUSIONS

Corticosteroid therapy may be effective for ventricular arrhythmias in the early stage, but less effective in the late stage.

Impact of percutaneous coronary intervention or coronary artery bypass grafting on outcome after nonfatal cardiac arrest outside the hospital

Survivors of cardiac arrest due to ventricular arrhythmias are at risk for recurrent events. The role of revascularization in secondary prevention for survivors of cardiac arrest has been addressed in various studies with conflicting results. A total of 142 survivors of cardiac arrest with coronary artery disease were evaluated according to a standardized protocol, including 2-dimensional echocardiography, myocardial perfusion scintigraphy, coronary angiography, and electrophysiologic testing. Revascularization of scintigraphically documented ischemic myocardial regions was performed in 44 patients (31%). Final therapy was based on the results of electrophysiologic testing. Four-year survival rates were 100% for revascularized noninducible patients, 84% for revascularized inducible patients, 91% for nonrevascularized noninducible patients, and 72% for nonrevascularized inducible patients. Only 1 patient (<1% of study population) died suddenly. Recurrences were much more frequent in patients without revascularization (38% vs 7%, p <0.001) and the recurrence rate was 0% in the revascularized noninducible patients. Thus, revascularization of ischemically jeopardized myocardium in survivors of cardiac arrest resulted in excellent survival; moreover, in absence of inducible ventricular arrhythmias, the recurrence rate was 0%. Systematic evaluation of survivors of cardiac arrest due to ventricular arrhythmias allows risk stratification and guidance of subsequent antiarrhythmic therapy.

E 047/1: a new class III antiarrhythmic agent

The efficacy, pharmacokinetics, safety, and tolerability of E 047/1, an amiodarone derivative, were evaluated in patients with acute supraventricular or ventricular arrhythmia. In an open, nonrandomized prospective multicenter trial, 20 patients were treated with three different i.v. dosage regimens of E 047/1. Arrhythmia termination indicated efficacy. Pharmacokinetics were determined by measurements of drug plasma levels. Safety was judged by changes of blood pressure, heart rate, ECG parameters, and appearance of adverse events. For local tolerability, effects at the site of infusion were assessed. In patients with atrial fibrillation and/or atrial flutter, drug plasma levels and prolongation of QT interval were correlated with efficacy. In 10 (50%) patients, therapeutic intervention with E 047/1 was successful. Drug plasma levels rapidly decreased within 1 h after administration. Blood pressure values and ECG parameters stayed constant during the observation period. Proarrhythmic effects were not observed. As adverse events, vertigo, vomiting, and nausea in three (15%) and hypotension in one (5%) patient, respectively, occurred in the high-dose bolus regimen only. At the site of infusion, no adverse effects were found. No dependency between drug plasma levels and arrhythmia termination was found. E 047/1 has proven to be efficient and safe in the treatment of arrhythmia. E 047/1 is characterized by rapid plasma elimination, absence of proarrhythmic or cardiodepressive effects, mild adverse events, and excellent local tolerability. For further investigation, we recommend a combined bolus- and weight-adapted infusion regimen.

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.

[Spanish Society of Cardiology practice guidelines on ambulatory monitoring of electrocardiogram and blood pressure]

In the present paper, a historical review and a clinical up-date are done on two procedures of great medical interest: Holter electrocardiography and ambulatory blood pressure monitoring. Technical and methodological characteristics of each procedure are carefully exposed, emphasizing each the lack of an international agreement in order to establish regulations that make all the equipment homogeneous and reliable in order to increase both accuracy and reliability in diagnosis. Based on published international scientific documents and the personal experience of the authors, guidelines for clinical applications, indications and limitations of each technique are analyzed in relation to capacities of the Spanish political and social public health system profile. New concepts and dynamics of developments such as; dynamic QT, RR variability or pulse wave velocity are exposed, in the frame of the present time and future for improving efficiency and clinical application.

Dynamics of low-frequency R-R interval oscillations preceding spontaneous ventricular tachycardia

BACKGROUND

Increased sympathetic activity is believed to be an important trigger of sustained ventricular tachyarrhythmias (VT) and is believed to be responsible for the increased heart rate that we and others have reported before the onset of spontaneous VT. However, in the patients reported herein, heart rate variability (HRV) indexes that reflect sympathetic activity unexpectedly declined, whereas heart rate increased. To explain this apparent paradoxic behavior, we tested the hypothesis that baseline levels of HRV determine its reaction to short-term autonomic perturbations before the onset of VT.

METHODS AND RESULTS

Holter electrocardiograms from 47 patients (ejection fraction 36% +/- 15%) with recorded VT were analyzed. Frequency domain HRV indexes (low-frequency power [LFP] 0. 04 to 0.15 Hz, high-frequency power [HFP] 0.15 to 0.4 Hz, and total power [TP] 0.01 to 0.4 Hz) were studied in 5-minute intervals and over a period of 24 hours. Patients were divided into those with a decrease in LFP in the 2-hour period before VT (group A, n = 32) and those with an increase or no change (group B, n = 15). The data were logarithmically transformed. Heart rate increased 15 minutes before the onset of VT compared with the 24-hour mean in both groups (group A: 80.3 +/- 15.4 to 86.1 +/- 20.0 beats/min, P =.005; group B: 80.6 +/- 13.5 to 86.7 +/- 14.0 beats/min, P =.017). Group A had higher TP, LFP, and LFP/HFP 2 hours before VT, and these variables decreased 15 minutes before the onset of VT (TP from 7.31 +/- 1.28 to 6.88 +/- 1.35, LFP from 6.09 +/- 1.28 to 5.38 +/- 1.33, LFP/HFP from 1.33 +/- 0.89 to 0.96 +/- 0.80, P <.001 for all 3 variables). HFP also decreased 15 minutes before VT compared with 2 hours (from 4.78 +/- 1.05 to 4.49 +/- 1.24, P =.028). In group B, which had lower baseline TP, LFP, and LFP/HFP at 2 hours before VT, these variables increased 15 minutes before the event (TP from 6.41 +/- 1.41 to 6.86 +/- 1.42, P =.004; LFP from 4.59 +/- 1.51 to 4.95 +/- 0.62, P <.001; LFP/HFP from 0.22 +/- 1.22 to 0.52 +/- 1.38, P =.10), whereas HFP did not change significantly (4.40 +/- 0.94 and 4.53 +/- 1.01, P =. 50).

CONCLUSIONS

An increase in heart rate and a drop in the low-frequency oscillations of R-R intervals before the onset of VT occurred in patients with higher baseline level of oscillatory activity. These changes suggest a dissociation between the average and rhythmic modulation of R-R intervals. A decline of the low-frequency oscillations in the setting of increasing heart rate could reflect an abnormal response to increased sympathetic activity in most of the patients from the studied group. The different behaviors of the HRV indexes before the onset of VT in the 2 groups suggest that change in the dynamics of R-R intervals, rather than the direction of change, facilitates arrhythmogenesis.

Risk stratification after acute myocardial infarction in the reperfusion era

Historically, risk stratification for survivors of acute myocardial infarction (AMI) has centered on 3 principles: assessment of left ventricular function, detection of residual myocardial ischemia, and estimation of the risk for sudden cardiac death. Although these factors still have important prognostic implications for these patients, our ability to predict adverse cardiac events has significantly improved over the last several years. Recent studies have identified powerful predictors of adverse cardiac events available from the patient history, physical examination, initial electrocardiogram, and blood testing early in the evaluation of patients with AMI. Numerous studies performed in patients receiving early reperfusion therapy with either thrombolysis or primary angioplasty have emphasized the importance of a patent infarct related artery for long-term survival. The predictive value of a variety of noninvasive and invasive tests to predict myocardial electrical instability have been under active investigation in patients receiving early reperfusion therapy. The current understanding of the clinically important predictors of clinical outcomes in survivors of AMI is reviewed in this article.

Electrophysiologic parameters to predict clinical recurrence of ventricular tachycardia in patients under electrophysiologic study-guided effective pharmacological therapy

Although an electrophysiologic study (EPS) is the most reliable method for selecting the treatment for a patient with sustained ventricular tachycardia (VT), VT recurrence may occur even during EPS-guided effective therapy. Electrophysiologic parameters were compared between patients with and without arrhythmic events under EPS-guided effective therapy to identify the predictive parameters of VT recurrence during the clinical course. The study population consisted of 77 consecutive patients with sustained VT who were receiving long-term pharmacological therapy that was demonstrated to be effective by the EPS assessment. The VT induction protocol employed 1-3 extrastimuli and rapid ventricular pacing at 2 right ventricular sites and 1 left ventricular site, and isoproterenol was infused when VT was not induced. To determine the 'effective' antiarrhythmic drug, all sustained ventricular arrhythmias had to be prevented during the whole induction protocol, but repetitive ventricular responses (RVR) were allowed to remain for up to 5 beats when they were in the same QRS configurations as the clinical VT and up to 12 beats when they were in polymorphic QRS configurations. The effective refractory periods (ERPs) at the 3 ventricular pacing sites and their difference (i.e., ERP-dispersion) and the maximum number of RVR beats were evaluated in an EPS during the control state and at the time of drug assessment. In the comparison of patients with and without VT recurrence, there was no significant difference in clinical characteristics or ERPs, but the deltaERP-dispersion (i.e., the increase in ERP-dispersion caused by the antiarrhythmic drug) and the maximum number of RVRs were significantly smaller in the group of patients without VT recurrence (deltaERP-dis, -3+/-8 vs. 6+/-12, p = 0.0027; maxRVR, 3+/-3 vs. 5+/-4, p = 0.0160). The VT recurrence rate was significantly lower in the patients with deltaERP-dis < or =0 or maxRVR<6 in comparison with the others (p = 0.01 14 and p = 0.0360). Patients with VT recurrence showed greater deltaERP-disp and a longer duration of RVRs at the time of drug assessment in comparison with the patients without VT recurrence. The prognosis of patients under EPS-guided therapy may be improved by the use of stricter criteria for drug assessment in the EPS, although this may decrease the number of drug responders determined in the EPS.

Sotalol: An important new antiarrhythmic

Sotalol, the most recently approved oral antiarrhythmic drug, has a unique pharmacologic profile. Its electrophysiology is explained by nonselective beta-blocking action as well as class III antiarrhythmic activity (including fast-activating cardiac membrane-delayed rectifier current blockade), which leads to increases in action potential duration and refractory period throughout the heart and in QT interval on the surface electrocardiogram. Its better hemodynamic tolerance than other beta-blockers may be a result of enhanced inotropy associated with class III activity. Sotalol's ability to suppress ventricular ectopy is similar to that of class I agents and better than that of standard beta-blockers. Unlike class I agents, its use in a postinfarction trial was not associated with increased mortality rate. Therapeutically, it has shown superior efficacy for prevention of recurrent ventricular tachycardia and ventricular fibrillation, which was the basis for its approval. In a randomized study, the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial, sotalol was associated with an increased in-hospital efficacy prediction rate (by Holter monitor or electrophysiologic study), reduced long-term arrhythmic recurrence rate with superior tolerance, and lower mortality rate than class I ("standard") antiarrhythmic drugs. Sotalol was 1 of 2 drugs selected for comparison with implantable defibrillators in the recent National Institutes of Health Antiarrhythmics versus Implantable Defibrillator (AVID) study. Sotalol appears to be a preferred drug for use with implantable defibrillators; unlike some other agents (eg, amiodarone) it does not elevate and, indeed, may lower defibrillation threshold. Although unapproved for this use, sotalol is active against atrial arrhythmias. It has shown efficacy equivalent to propafenone and quinidine in preventing atrial fibrillation recurrence, but it is better tolerated than quinidine and provides excellent rate control during recurrence. Sotalol's major side effects are related to beta-blockade and the risk of torsades de pointes (acceptably small if appropriate precautions are taken). Unlike several other antiarrhythmics (eg, amiodarone), it has no pharmacokinetic drug-drug interactions, is not metabolized, and is entirely renally excreted. Initial dose is 80 mg twice daily, with gradual titration to 240 to 360 mg/day as needed. The daily dose must be reduced in renal failure. On the basis of favorable clinical trials and practice experience, sotalol has shown a steadily growing impact on the treatment of arrhythmias during its 5 years of market availability, a trend that is likely to continue.

Evaluation of the acute electrophysiologic effects of intravenous dronedarone, an amiodarone-like agent, with special emphasis on ventricular repolarization and acquired torsade de pointes arrhythmias

In the anesthetized dog with complete chronic AV block (CAVB), we evaluated and compared the acute electrophysiologic effects of dronedarone i.v. (Dron, 2 times 2.5 mg/kg/10 min) and amiodarone i.v. (Amio, 2 times 5 mg/kg/10 min). This canine model with a high sensitivity for acquired torsade de pointes (TdP) provides an ideal substrate to evaluate ventricular repolarization abnormalities. Six ECG leads and two endocardial monophasic action potential (MAP) recordings in the left and right ventricle (LV and RV) were simultaneously recorded to measure QT time, action-potential duration (APD), interventricular dispersion (deltaAPD = LV(APD) - RV(APD)), early afterdepolarizations (EADs), ectopic beats (EBs), and TdP. Measurements were made at the spontaneous idioventricular rhythm (IVR) and 1,000-ms steady-state pacing. To investigate its short-term, antiarrhythmic properties, Dron was given after almokalant (0.12 mg/kg)-induced TdP. Furthermore, in another set of experiments, oral Dron (20 mg/kg, b.i.d) was given for 3 weeks to conscious CAVB dogs. Dron, i.v., shortened ventricular repolarization (QT, 435 +/- 60 to 360 +/- 55; LV(APD) 395 +/- 75 to 335 +/- 60 ms; p < 0.05), whereas IVR and ventricular effective refractory period (VERP, 225 +/- 30 to 230 +/- 30 ms) remained similar. Therefore the VERP/QT ratio increased (0.55 +/- 0.04 to 0.61 +/- 0.03; p < 0.05). Similar results were obtained with Amio, i.v.. Almokalant-induced TdP was characterized by an increased repolarization duration, deltaAPD, and EADs. Dron, i.v., suppressed the EADs, EBs, and TdP by a reduction and homogenization of repolarization (LV(APD), 505 +/- 110 to 455 +/- 80 ms, and deltaAPD, 110 +/- 55 to 65 +/- 40 ms). Long-term oral Dron increased the PP interval, CL-IVR, and QT(c) time. In contrast to oral treatment, Dron i.v. shortens ventricular repolarization parameters, resulting in suppression of EAD-dependent acquired TdP. The increased VERP/QT ratio after Dron i.v. may indicate an important second antiarrhythmic property.

Risk Factors for Tachycardia Events Caused by Antiarrhythmic Drugs: Experience From the ESVEM Trial

BACKGROUND: In the Electrophysiology Study versus Electrocardiographic Monitoring (ESVEM) trial, up to seven antiarrhythmic drugs were randomly assigned to 486 patients with a history of sustained ventricular arrhythmia. At baseline, all the patients had inducible sustained ventricular tachycardia (VT) and had >/=10 premature ventricular beats (PVBs) per hour on 48-hour Holter monitoring. A total of 1,229 drug trials were performed. Antiarrhythmic drugs were discontinued during hospitalization because of ventricular tachyarrhythmias thought to be a proarrhythmic effect of the antiarrhythmic drugs in 96 of 479 patients (20%) who received drugs. Proarrhythmic effects were defined as sustained VT, ventricular fibrillation or arrhythmic death, torsade de pointes, or distinct intolerable worsening of the baseline arrhythmia after at least three doses of the drug. METHODS AND RESULTS: Eighteen baseline characteristics were analyzed for factors that would predict a higher incidence of proarrhythmia. These included type of heart disease, previous myocardial infarction, symptom activity scale, gender, type of arrhythmia, VT/ventricular fibrillation, age, left ventricular ejection fraction (LVEF), PVB frequency, heart rate, QRS duration, and QT interval. Multiple logistic regression analysis identified increased mean PVB frequency (P =.003) and increased heart rate (P =.026) as significant predictors of proarrhythmia. Decreased LVEF (<25%) exhibited only a trend toward significance (P =.073). When proarrhythmia was redefined as sustained VT, cardiac arrest of arrhythmic death, or torsade de pointes (n = 59), PVB frequency (P =.003) and heart rate (P =.034) were still the only significant baseline predictors. CONCLUSIONS: In the ESVEM study, higher PVB frequency and higher heart rate were significant predictors of drug-induced proarrhythmia.

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.

Lack of benefit of very short basic drive train cycle length or repetition of extrastimulus coupling intervals for induction of ventricular tachycardia

INTRODUCTION

There are considerable variations of uncertain importance in basic drive train cycle lengths and degree of repetition of extrastimuli used in programmed ventricular stimulation protocols in different laboratories. We compare prospectively three different stimulation protocols to examine the influence of a short basic drive train cycle length and repetition of extrastimuli on induction of ventricular tachycardia.

METHODS AND RESULTS

Thirty consecutive patients who had documented ventricular tachycardia or fibrillation based on underlying coronary artery disease underwent programmed ventricular stimulation with each of the three study protocols. Protocol A used a basic drive train cycle length of 400 msec with each extrastimulus coupling interval delivered only once. Protocol B used the same basic drive train cycle length, but with each extrastimulus coupling interval repeated three times before decrementing. Protocol C used 300 msec as the cycle length of basic drive trains without repetition of extrastimuli. Sixty-three percent, 67%, and 63% of the study patients had ventricular tachycardia inducible with protocols A, B, and C, respectively (P = NS). Ventricular fibrillation was induced in 23% of the 30 patients in all three protocols. There were no significant differences in the mean cycle lengths of induced ventricular tachycardia, the number of extrastimuli used, and the coupling interval of the last extrastimulus inducing ventricular tachycardia among the three protocols.

CONCLUSION

This study showed no clinical benefit for repetition of extrastimuli that have failed to induce a ventricular tachyarrhythmia during programmed ventricular stimulation. A short basic cycle length of 300 msec was not superior to 400 msec for induction of ventricular tachyarrhythmias. We recommend the use of basic cycle length 400 msec with delivery of each extrastimulus interval only once as the initial protocol for programmed ventricular stimulation.

The usefulness of Holter monitoring in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia: studies in patients in whom no effective pharmacologic therapy could be determined by electrophysiologic study

The usefulness of Holter monitoring (HM) in selecting pharmacologic therapy for patients with sustained monomorphic ventricular tachycardia (VT) was evaluated in patients in whom no effective pharmacologic therapy could be determined in an electrophysiologic study (EPS). The study population consisted of 49 consecutive patients with sustained VT who were receiving long-term pharmacologic therapy despite the fact that no pharmacologic therapy had been found to be effective in the EPS. The efficacy of the pharmacologic therapies was assessed by HM. A reduction in frequent (10/h) premature ventricular contractions (PVCs) was used as an index of treatment efficacy, with therapies achieving substantial PVC suppression (>70% of all PVCs) being considered to be effective (HM effective group). When no therapy was found to be effective when assessed by HM, a drug with any other beneficial effect, eg, reduction in VT rate, was chosen (HM ineffective group). VT recurrence and survival were compared between groups. During the follow-up period of 31+/-28 months, VT recurrence was observed in a total of 25/49 patients: 3/17 patients in the HM effective group, in 18/25 in the HM ineffective group, and in 4/7 in the HM undetermined group (p=0.0487). Sudden cardiac death occurred in a total 7/49 patients: 2/17 patients in the HM effective group, 4/25 patients in the HM ineffective group, and 1/7 patient in the HM undetermined group (p=0.2828). Among patients in whom no effective therapy could be determined by EPS, the VT recurrence rate was significantly lower in the group in whom treatment was effective as assessed by HM than among those in whom treatment was assessed by HM to be ineffective. Sudden cardiac death rate was also lowest in the HM effective group, although the difference was not statistically significant. HM assessment was considered useful in selection of pharmacologic therapy for patients in whom no effective therapy could be determined in the EPS.

[Holter monitoring and programmed ventricular stimulation]

Long-term ECG recordings are the method of choice to evaluate quantity and quality of spontaneous rhythm disturbances. However, this method is limited by the variability of the arrhythmias. Invasive procedures such as programmed stimulation allow the provocation of tachyarrhythmias. Indications for both methods are diagnostic clarification of clinical symptoms, risk stratification with respect to arrhythmogenic sudden cardiac death as well as the control of antiarrhythmic therapy.Due to the high variability of spontaneous complex ventricular arrhythmias, Holter monitoring often fails to document the cause of severe symptoms such as syncope or sudden cardiac death. In these patients, invasive electrophysiological testing is required to provoke the arrhythmia.The prognostic significance of spontaneous ventricular arrhythmias recorded during ambulatory monitoring depends on the underlying cardiac disease. In patients with coronary artery disease and a history of myocardial infarction there is evidence that frequent single and/or complex ventricular extrasystoles indicate an increased risk of sudden cardiac death, especially in the presence of a reduced left ventricular function. In these patients, programmed ventricular stimulation can further characterize a highrisk group.For the management of antiarrhythmic therapy in symptomatic patients, under certain conditions both methods appear to be helpful. For the majority of these patients, however, the invasive electrophysiologic study should be preferred.Thus, long-term ECG recordings and programmed electrical stimulation are no competing, but complementary methods in clinical cardiology.

Management of patients with life-threatening ventricular tachyarrhythmias in the defibrillator era: the need to differentiate

Patients with a history of sustained ventricular tachyarrhythmias form an extremely inhomogeneous group with respect to presenting arrhythmia, underlying cardiac disease, and therefore, risk of dying suddenly. For subgroups such as ventricular tachycardia in the absence of underlying cardiac disease, radiofrequency catheter ablation offers cure. In others, implantation of a cardioverter defibrillator already appears to have gained the therapy of first choice, leaving only a secondary role to antiarrhythmic drugs. It must be emphasized however, that these new therapeutic strategies have their pros and cons like the older, seemingly out-fashioned approaches of noninvasively or invasively guided antiarrhythmic drug therapy or empiric amiodarone treatment. Until the advent of controlled randomized trials comparing the implantable cardioverter defibrillator (ICD) with the best other, usually medical form of treatment, physicians must continue to base their individual therapeutic decisions on circumstantial published and personal experience. In doing so, the recent achievements of catheter ablation and defibrillator implantation have definitely improved patient care, but have not made antiarrhythmic drugs jobless. With all the alternatives at hand, it remains a challenging task to weigh the benefits and risks of the various approaches against each other in an attempt to tailor the antiarrhythmic intervention to the very individual need of the patient.

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.

Reproducibility of drug efficacy predictions by Holter monitoring in the electrophysiologic study versus electrocardiographic monitoring (ESVEM) trial. ESVEM Investigators

Selection of antiarrhythmic therapy may be based on suppression of spontaneous ventricular arrhythmias assessed by Holter monitoring, but the implications of discordant Holter results on repeat 24-hour monitoring has not been defined. This study examines the frequency and significance of reproducible Holter suppression on two 24-hour recordings in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial. Repeat 24-hour Holter monitoring was obtained in patients randomized to the Holter monitor limb of the ESVEM trial, during the same hospitalization, after a drug efficacy prediction. These Holters were not used to define drug efficacy but were subsequently analyzed to determine the reproducibility of drug efficacy predictions by Holter monitoring. A repeat 24-hour Holter monitor, following the one that predicted drug efficacy, was available in 119 patients. Ninety-nine patients (83%) also had suppression that met efficacy criteria on the second Holter monitor. There were no significant differences in arrhythmia recurrence (p = 0.612) or mortality (p = 0.638) in patients with concordant Holter results (n = 99; 1-year arrhythmia recurrence = 45%; 1-year mortality = 10%) compared with those with discordant Holter results (n = 20; 1-year arrhythmia recurrence = 45%; 1-year mortality = 16%). We conclude that (1) there is discordance between the first effective Holter monitor and a repeat Holter monitor in 17% of patients, and (2) suppression of ventricular ectopic activity on 2 separate 24-hour Holter monitors does not identify a group with a better outcome, nor does failure of suppression on the second Holter monitor identify a group with a worse prognosis.

Long-term cost-effectiveness of alternative management strategies for patients with life-threatening ventricular arrhythmias. Electrophysiologic Study versus Electrocardiographic Monitoring (ESVEM) Investigators

BACKGROUND

Serial antiarrhythmic drug testing guided by Holter monitoring and electrophysiologic study had similar clinical outcomes in the Electrophysiologic Study versus Electrocardiographic Monitoring (ESVEM) trial, while patients treated with sotalol had improved outcomes. The purpose of this study was to compare long-term cost-effectiveness of these management alternatives.

METHODS

Patients in the ESVEM trial were linked to computerized files of either the Health Care Finance Administration or the Department of Veterans Affairs. Total hospital costs and survival time over five year follow-up were measured using actuarial methods, and cost-effectiveness was calculated.

RESULTS

Patients randomized to therapy guided by electrophysiologic study had more hospital admissions, higher costs, and a cost-effectiveness ratio of $162,500 per life year added compared with therapy guided by Holter monitoring. Patients randomized to sotalol had fewer hospitalizations, lower costs, and better survival than patients randomized to other drugs, and sotalol was a dominant strategy in the cost-effectiveness analysis. Patients for whom an effective drug was found had fewer hospital admissions, lower costs, and longer survival. These findings were robust in sensitivity analyses and in bootstrap replications.

CONCLUSIONS

Serial drug testing guided by electrophysiologic study had an unfavorable cost-effectiveness ratio relative to Holter monitoring, while sotalol was cost-effective relative to other antiarrhythmic drugs.

Intracoronary arterial occlusion: a novel technique potentially useful for ablation of cardiac arrhythmias

To develop a new technique for ablating arrhythmias by interrupting coronary perfusion of the myocardium, we studied six mongrel dogs, weighing 20-35 kg. Under angiographic guidance a microcatheter (1.0 mm diameter) was introduced into a branch of the left anterior descending or posterior descending coronary artery. A detachable platinum coil (0.0254 cm diameter, 3 cm length) soldered onto a stainless-steel delivery wire (Guglielmi) was inserted through the microcatheter and advanced to occlude the arterial branch. A 0.5-mA electric current applied to the proximal end of the delivery wire resulted in intravascular thrombosis due to attraction of the negatively charged blood cells, platelets, and fibrinogen to the positively charged platinum coil. In approximately 4.5 minutes, as the thrombus was formed, electric current dissolved the soldering and detached the platinum coil from the delivery wire. Electrocardiograms showed focal ST-T changes but no ventricular tachyarrhythmias. Pathologic studies revealed thrombosis around the platinum coil and well-demarcated focal ischemia/infarction that was correlated with elevation of cardiac enzymes. We conclude that intracoronary arterial embolization and electrothrombosis using an electrolytic platinum coil can be selectively performed in a very small coronary arterial branch, resulting in a limited area of myocardial damage. This technique is potentially useful for ablating arrhythmias and may be safer and more controllable than intracoronary alcohol infusion.

Evaluation and Management of Sudden Death Survivors

Only 20% of patients survive a cardiac arrest. Up to 80% of patients have a cardiac arrest secondary to a ventricular tachyarrhythmia. In the adult population, over 70% of the above patients have obstructive coronary artery disease; thus, coronary arteriography should be performed in all survivors of cardiac arrest. Once reversible causes have been treated, antiarrhythmic therapy is usually guided by Holter monitoring, electrophysiologic testing or both. Due to high recurrence rates on antiarrhythmic drugs, many patients are now treated with implantable cardioverter defibrillators. Although these devices appear to improve sudden death survival, long-term overall survival may not be superior to “best drug therapy.” This hypothesis is currently being tested in two prospective randomized, multicenter trials.

Pharmacokinetics and pharmacodynamics of (+/-)-sotalol in healthy male volunteers

1. We investigated the pharmacokinetics and pharmacodynamics of (+/-)-sotalol administered orally to healthy male volunteers in single doses of 40, 80 and 160 mg and in multiple doses of 80 mg twice daily for 7 consecutive days. 2. In the single dose studies, the half-life of (-)-sotalol (7.2-8.5 h) was significantly (P < 0.01) shorter than that of (+)-sotalol (9.1-11.4 h) while the renal clearance of (-)-sotalol (110.6-126.4 ml min-1) was significantly (P < 0.01) faster than that of (+)-sotalol (102.2-110.1 ml min-1). In the multiple dose studies, similar differences in the pharmacokinetics of (+)- and (-)-sotalol were observed. In addition, the pharmacokinetics of both (+)- and (-)-sotalol on day 4 were shown to be essentially the same as those on day 7. 3. In pharmacodynamic examinations, (+/-)-sotalol prolonged QTc intervals on electrocardiograms dose-dependently after single doses of 80 and 160 mg (3.81 +/- 2.96%, 13.23 +/- 5.66%). The correlation between the plasma concentration of (+/-)-sotalol and prolongation of QTc intervals was nearly linear, and showed no hysteresis. 4. In conclusion, we demonstrated that QTc interval was prolonged with a linear correlation to the plasma concentration of (+/-)-sotalol. In addition, our study suggested that differences in the pharmacokinetics of (+)- and (-)-sotalol may be attributable to faster urinary excretion of (-)-sotalol.

Electrophysiologic Study versus Electrocardiographic Monitoring (ESVEM): a critical appraisal

This paper reviews the Electrophysiologic Study versus Holter Monitoring (ESVEM) trial, addressing several areas of concern including potential enrollment bias, an inadequate electrophysiologic testing protocol during drug therapy, and an unexpectedly high recurrence rate in patients deemed to be controlled by either method. The paper concludes that there are insufficient data to warrant extrapolation of the ESVEM results to survivors of cardiac arrest.

Design and analysis of the ESVEM Trial

Inadequate understanding of the design and statistical approach of a clinical trial and the failure to recognize subjective aspects of the analysis often result in misinterpretation of trial results. This is exacerbated by the push to shorten publications and the wish for a simple message that summarizes the outcome of the trial. The purpose of this review is to critically review the design and statistical analyses of the results, to evaluate the assumptions underlying the statistical tests, and to examine the results of exploratory analysis on the interpretation of major findings of the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial. The trial was unusual because its primary objective was to compare testing methods instead of treatments. This necessitated using a subset of the original randomized groups for sensible analysis of the clinical question. Nevertheless, the two groups appeared to be well balanced. The absence of a difference in outcome could be verified by several analyses. In addition, confidence intervals were narrow, indicating the high precision and reliability of the findings. However, the comparison of antiarrhythmic drugs is problematic because the trial was not designed to address this issue. There were differences in the distribution of clinical characteristics between the groups who received different antiarrhythmic drugs. Nevertheless, using both univariate analyses and a variety of adjustments for important prognostic variables, treatment with sotalol appeared to be a significant predictor of reduced arrhythmia recurrence, and sotalol was consistently associated with a trend for nearly a 50% reduction in sudden death and all-cause mortality as compared with the other drugs administered in the trial. In conclusion, the ESVEM trial raises a number of interesting and instructive issues about clinical trial design and analysis.

Electrocardiographic predictors in the ESVEM trial: unsustained ventricular tachycardia, heart period variability, and the signal-averaged electrocardiogram

Sudden death remains a major problem because the causes are uncontrolled and accurate predictors have not been identified. However, new forms of electrocardiographic (ECG) analyses may provide prognostic information. The Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial provides a unique perspective to this issue because baseline and follow-up data were prospectively acquired on a relatively large sample of patients who were homogeneous with respect to sustained ventricular tachyarrhythmias, frequent ectopic activity, and inducible sustained ventricular tachyarrhythmias. Although analysis of the large amount of ECG data collected is in progress, initial studies have provided information about unsustained ventricular tachycardia (VTu), heart period (R-R) variability, and the signal-averaged ECG. VTu has been reported to have prognostic implications in several disorders, but its clinical significance in patients with sustained ventricular tachyarrhythmias is unknown. The significance of VTu recorded in the baseline (antiarrhythmic drug-free) 48-hour ECG recording in ESVEM study patients was examined; no variable representing the presence of VTu, the frequency of VTu events, or the duration of the longest episode of VTu was a significant predictor of arrhythmia recurrence, arrhythmic death, or all-cause mortality, although a trend was present for worse all-cause mortality in patients with VTu. R-R variability provides powerful prognostic information after acute myocardial infarction (AMI) and in patients with chronic ischemic heart disease. In general, R-R variability decreases dramatically at the time of AMI and recovers somewhat during the year after infarction. Although most patients in the ESVEM trial had chronic ischemic heart disease, R-R variability, which has been determined in about three fourths of the patients, was much lower than that reported in patients 1 year after MI. Instead, the mean values were closer to the more depressed values observed shortly after MI. This suggests a greater degree of autonomic dysfunction in patients with sustained ventricular tachyarrhythmias, frequent ventricular ectopic activity, and low ejection fractions, as compared with that for patients with chronic ischemic heart disease in general. Signal-averaged ECGs have also been shown to predict arrhythmic events in patients with ischemic heart disease. In a subset of the ESVEM patients, antiarrhythmic drugs that block sodium channels were found to prolong the filtered, signal-averaged QRS duration, especially the late potential portion. This correlated with prolongation of the cycle length of induced ventricular tachycardia. Sotalol appeared to have a differential effect on the signal-averaged ECG; the signal-averaged QRS shortened slightly in patients in whom induction of VT was suppressed by sotalol, whereas it appeared to lengthen slightly in patients in whom VT remained inducible despite sotalol. This suggests that sotalol may affect conduction in diseased tissue in some patients, and that this may affect suppression of ventricular arrhythmia induction by programmed stimulation.

A summary and assessment of the findings and conclusions of the ESVEM trial

The Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial was completed in 1992 and the primary results were reported in 1993. Since then, considerable discussion about this trial has taken place and new trial results have been reported. Trial analysis has yielded seven principal findings to date concerning treatment of patients with ventricular tachyarrhythmias, ie: (1) similar accuracy of electrophysiologic study (EPS), Holter monitoring (HM), and EPS combined with HM for predicting antiarrhythmic drug efficacy; (2) greater efficiency and lower cost of HM; (3) improved survival associated with predicted drug efficacy; (4) predictors of response to EPS and HM; (5) greater efficacy and lower cost of therapy with sotalol compared with drugs with class-l effects; (6) lack of a relationship between presenting and recurring arrhythmia; and (7) preponderance of nonarrhythmic deaths in trial participants. A number of additional specific findings of the trial are reviewed in this symposium. Several criticisms of the trial's enrollment, methods, and efficacy criteria are reviewed and discussed. Some criticisms are valid. Many are related to misunderstandings of ESVEM trial methodology and to bias of the individual critics. Some are simply incorrect. The importance of the ESVEM trial in the present day may be limited by the growing use of implanted devices rather than drugs for treatment of ventricular tachyarrhythmias. If clinical trials ultimately prove devices to be no more effective than drugs, the findings of the ESVEM investigators will grow in importance.

A randomized clinical trial of the noninvasive and invasive approaches to drug therapy for ventricular tachycardia: long-term follow-up of the Calgary trial

Individualized antiarrhythmic drug therapy for patients with ventricular tachyarrhythmias may be selected by the noninvasive approach (suppression of spontaneous ventricular premature beats) or the invasive approach (suppression of ventricular tachyarrhythmias induced at an electrophysiologic study). There is controversy over which approach is superior. From a screened population of 124 patients with symptomatic ventricular tachycardia or ventricular fibrillation, 57 patients with both frequent ventricular premature beats and inducible ventricular tachycardia at baseline were randomized to have chronic therapy selected by either the noninvasive or invasive approach. These patients have now been followed up for a minimum event-free period of 6.5 years. By intention-to-treat, therapy selected by the invasive approach prevented subsequent ventricular tachyarrhythmias better than that selected by the noninvasive approach (6-year probabilities of freedom from symptomatic sustained ventricular tachyarrhythmia recurrence; noninvasive approach, 0.45 +/- 0.10; invasive approach, 0.73 +/- 0.09; p=.02). This advantage of the invasive approach was also evident for the outcome of any ventricular tachyarrhythmia recurrence and for efficacy analyses involving only those patients with a drug-efficacy prediction. We hypothesize that the difference between these results and those of the ESVEM trial are caused, in part, by differences in the characteristics of the enrolled patients and differences in criteria used to define a predicted-effective therapy.

Influence of Holter monitor and electrophysiologic study methods and efficacy criteria on the outcome of patients with ventricular tachycardia and ventricular fibrillation in the ESVEM trial

Because not all laboratories use the monitoring and stimulation protocols used in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) trial, we reanalyzed the ESVEM patients' data using alternative, commonly used Holter monitor (HM) and programmed stimulation efficacy criteria to determine if different criteria would have changed the trial's conclusions. Also, because beta-blocker use and coronary artery disease frequency were not equally distributed between the two limbs in ESVEM, we reanalyzed the ESVEM data adjusting for the possible effect of these variables. In the HM limb, drug efficacy in the original ESVEM analysis was declared by reduction of total premature ventricular complexes (PVCs) by 70%, pairs by 80%, runs of 3 to 15 beats by 90%, and all ventricular tachycardia (VT) more than 15 beats by 100%. In this analysis, we examine outcome in subjects meeting two more stringent sets of criteria, (1) reduction of total PVCs by 70%, of pairs by 80%, and of all VT by 100% (new criteria set 1) and (2) reduction of total PVCs by 80%, of pairs by 90%, and of all VT by 100% (new criteria set 2). In electrophysiology (EPS) limb patients, we compared arrhythmia recurrence when efficacy was declared with triple extrastimuli as compared with maximally testing with double extrastimuli, and arrhythmia recurrence was compared in patients tested with identical versus any more aggressive protocol on drug than was used before drug. We also compared the predictive accuracy of zero versus 3 to 15, and 0 to 5, 6 to 10, and more than 10 induced beats on drug. Additionally, we compared predictive accuracy of the HM- and EP-guided limbs excluding patients on beta blockers and those with noncoronary disease. Lastly, to determine whether concordant results on HM and EPS testing would provide more accurate efficacy predictions than EP testing alone, HM recordings obtained in EPS-limb patients but not processed or used during the course of the EVSEM study were analyzed. The original ESVEM HM criteria, new set 1, and new set 2 yielded predicted drug efficacy rates of 77%, 68%, and 58%, respectively; however, arrhythmia recurrence rates were unchanged. Similarly, arrhythmia recurrence rates for patients tested with triple versus less than triple extrastimuli (p=.238), more aggressive versus identical protocols (p=.955), and 0 to 5 v 6 to 10 v more than 10 induced beats (p=.263) or 0 v 3 to 15 induced beats (p=.106) were unchanged. in the 215 (of 286) patients with coronary disease and not receiving beta blockers, there was still no difference in arrhythmia recurrence or mortality between the noninvasive and invasive limbs in ESVEM. Lastly, in patients with drug efficacy predictions by EPS testing, there was no difference in outcome in patients who had concordant versus discordant efficacy prediction by simultaneously obtained HMs. The use of more stringent testing methods and efficacy criteria would not have significantly improved the predictive accuracy of drug assessment by HM or EPS in the ESVEM trial. Additionally, excess noncoronary disease in EP-guided patients and excess beta-blocker used in HM-guided patients did not influence the results in the ESVEM trial.

Implantable defibrillators are preferable to pharmacologic therapy for patients with ventricular tachyarrhythmias: an antagonist's viewpoint

Despite their intuitive appeal, implantable cardioverter defibrillator s (ICDs) will require testing in randomized studies to establish their relative value as compared with antiarrhythmic drugs in patients with life-threatening ventricular tachyarrhythmias (ventricular tachycardia/ventricular fibrillation [VT/VF]). In these studies, only total mortality is an acceptable primary end point. Lessons from recent drug studies (CAST, ESVEM, CASCADE) have shown that class-III/beta-receptor antagonist therapy is superior to class-I drugs selected by electrophysiologic or Holter monitor testing. Thus, sotalol or amiodarone should now be considered first-line drugs for VT/VF therapy. Advantages of contemporary drug therapy for VT/VF include wide experience among clinicians, progressively better drugs, lower cost, universal availability, greater flexibility in use (easy to start, titrate, and stop), ability to suppress (not just terminate) events, and favorable effect on disease progression (eg, beta-blockade effects in cardiomyopathy and ischemic heart disease). Recent matched observational studies and a small randomized experience (CASH) suggest near equivalence in total mortality in ICD and drug-treated groups. Until or unless modified by the results of large, ongoing, randomized trials (AVID, CIDS), contemporary antiarrhythmic drug therapy has much to be recommended as first-line, standard treatment for patients with VT/VF. Even in patients receiving ICDs, added drug therapy is frequently indicated.

Contemporary clinical trials in ventricular tachycardia and fibrillation: implications of ESVEM, CASCADE, and CASH for clinical management

Recent clinical trials in patients with ventricular tachycardia (VT) or fibrillation (VF) have occurred in the setting of the disappointing results of postinfarction secondary prevention studies using Class I antiarrhythmics (e.g., CAST). ESVEM addressed in a randomized trial whether electrophysiologic study (EPS) or Holter monitoring (HM) is a more accurate predictor of long-term antiarrhythmic drug efficacy in VT/VF patients (N=486) and what the relative efficacy of various antiarrhythmic agents is for VT/VF. Surprisingly, arrhythmia recurrence rates were not significantly different by the method of determining an efficacy prediction. However, arrhythmia recurrence and mortality were lower (by about 50% at 1 year) in patients treated with sotalol (a mixed Class II/III agent) than with other drugs (Class I). CASCADE evaluated empiric amiodarone versus guided (EPS or HM) standard (Class I) therapy in survivors of out-of-hospital cardiac arrest due to VF. The primary endpoint of cardiac death, resuscitated VF, or syncopal shock (in ICD patients) was reduced by amiodarone compared with conventional therapy (9% vs 23% at 1 year). An interim report of the ongoing CASH study suggested in 230 survivors of cardiac arrest that propafenone (Class IC) provided less effective prophylaxis (approximately 20% 1-year mortality) compared with randomly assigned therapies with amiodarone, metoprolol, or an ICD (approximately 14% mortality rates) and was excluded from further study. These studies have led to a paradigm shift in the approach to antiarrhythmic therapy of VT/VF: drugs with antisympathetic plus Class III (refractoriness prolonging) action (i.e., sotalol, amiodarone) are superior to traditional drugs with Class I( conduction slowing) effects, even when guided by EPS or HM.

Spontaneous sustained ventricular tachycardia in the Electrophysiologic Study Versus Electrocardiographic Monitoring (ESVEM) Trial

OBJECTIVES

We compared the QRS waveforms of the initial and subsequent complexes of spontaneous sustained monomorphic ventricular tachycardia and the rhythm induced at electrophysiologic study to test the theory that premature ventricular complexes "trigger" spontaneous ventricular tachycardia and that a stable substrate exists such that the spontaneous arrhythmia can be reproduced at electrophysiologic study.

BACKGROUND

Failure rates have been high in several recent studies in which prevention of ventricular tachyarrhythmias was guided by suppression of premature ventricular complexes or induced ventricular tachycardias.

METHODS

Digital waveform analysis was used to distinguish events of ventricular tachycardia initiated by configurationally distinct, possibly triggering, complexes (type 1) from events in which the initial QRS waveforms were identical to subsequent complexes, suggesting no requirement for premature ventricular beats (type 2).

RESULTS

Of 1,102 episodes of spontaneous ventricular tachycardia, 73 (6.6%) were type 1; 1,012 were type 2 (91.8%); and 17 (1.5%) were uncertain. Of 59 patients only 14 (24%) had only type 1 episodes (group 1), whereas 37 patients (63%) had predominantly type 2 events (group 2) (p < 0.0001). Sustained ventricular tachycardia was inducible in all group 1 patients, and in most (57%) the induced rhythm was similar to the spontaneous rhythm. Ventricular tachycardia could not be induced in 7 patients from group 2 (19%), and in 18 patients (49%) the induced and spontaneous rhythms were dissimilar. Recurrence of arrhythmia rates differed according to the guidance method in group 2.

CONCLUSIONS

Discrepancies between observed and predicted modes of initiation of ventricular tachycardia and between spontaneous and induced rhythms could result in inappropriate guidance and subsequent failure of antiarrhythmic treatment.

Insights into the Electrophysiology Study Versus Electrocardiographic Monitoring Trial: its programmed stimulation protocol may introduce bias when assessing long-term antiarrhythmic drug therapy

OBJECTIVES

We hypothesized that if the Electrophysiology Study Versus Electrocardiographic Monitoring (ESVEM) trial programmed stimulation protocol misclassified some drug trials as effective, then the misclassification rate would be proportionally greater for drugs other than sotalol.

BACKGROUND

In the ESVEM trial, patients treated with sotalol had fewer arrhythmic recurrences than those treated with other antiarrhythmic drugs despite similar efficacy predictions during electrophysiologic testing.

METHODS

We retrospectively compared the standard programmed stimulation protocol used at Case Western Reserve University, which used three extrastimuli during all follow-up studies, with the ESVEM protocol in 176 antiarrhythmic drug trials: sotalol (n = 54), procainamide (n = 73) and quinidine/mexiletine (n = 49).

RESULTS

Predictions of efficacy were higher in the sotalol trials (14 of 54 standard, 20 of 54 ESVEM) than in procainamide trials (7 of 73 standard, 14 of 73 ESVEM) or quinidine/mexiletine trials (1 of 49 standard, 7 of 49 ESVEM). Thus, the two protocols classified 19 of 176 trials differently: not effective by the standard protocol but effective by the ESVEM trial. Discordant predictions of drug efficacy constituted a smaller proportion of ESVEM protocol efficacy predictions for sotalol (6 [30%] of 20) than for the other drugs (13 [62%] of 21, p < or = 0.05).

CONCLUSIONS

In the present study, the ESVEM programmed stimulation protocol predicted efficacy more often than the standard protocol. Discordant predictions represented a smaller portion of efficacy predictions for sotalol than for the other drugs. Thus, in the ESVEM trial, the superior long-term follow-up observed in patients assigned to sotalol may have been an artifact of the stimulation protocol utilized by the ESVEM investigators.

Sotalol: a new beta-adrenergic blocker for ventricular arrhythmias

Sotalol is a water-soluble, nonselective, beta-adrenergic blocker that was recently approved in oral form in the United States for the treatment of ventricular arrhythmias that are judged to be life-threatening. As a beta-blocker, sotalol is unique in having additional class-III antiarrhythmic activity. It is still not resolved whether sotalol is more effective than other beta-blockers in managing arrhythmias, but there are suggestions that it might possess greater antiarrhythmic and life-protecting activities than other types of antiarrhythmic drugs. The drug is well tolerated, but, because of its electrophysiologic activity, there is a small risk of proarrhythmia, specifically the development of polymorphic ventricular tachycardia and torsade de pointes.

Electrophysiologic effects of antiarrhythmic drug therapy in the prediction of successful suppression of induced ventricular tachycardia

Predictors of a successful outcome of serial electrophysiologic (EP) and drug studies have been identified from among baseline patient characteristics but not from among measures of baseline and drug-related EP effects. Identifying such predictors would be useful in explaining the mechanism of successful drug therapy and in guiding drug development and selection. We prospectively studied EP characteristics in 159 trials in 62 patients with ventricular tachycardia or ventricular fibrillation during antiarrhythmic therapy and compared EP measures between successful (n = 30) and failed trials (n = 129). The average age of the patients was 64 years (range 27 to 78 years); 82% were men and 18% women; and 87% had coronary artery disease. Measurements included R-R, QRS, and QT intervals during intrinsic rhythm and during pacing at cycle lengths of 600 of 400 msec; ventricular effective refractory periods (ERP) during pacing at cycle lengths of 600 and 400 msec; and changes in these measures, comparing treatment with drug-free baseline. Univariate predictors of success (in order of significance) included ERP600/QRS600, sotalol versus other drugs, ERP400/QRS400, delta ERP600, delta R-R, ERP600, QRS400 (negative association), delta ERP400, QRS600 (negative association), ERP400 (all p < 0.1). In two separate multivariate models, one for each drive cycle length, only the ratio ERP600/QRS600 (p = 0.01) in the first model and ERP400/QRS400 (p = 0.01) in the second model were significantly and independently associated with achieving noninducibility with drug therapy. Therefore measures of greater refractoriness and lesser delays in conduction velocity (ie, greater "wavelength") relate to drug success.(ABSTRACT TRUNCATED AT 250 WORDS)