[When and how to treat ventricular ectopic beats]

Ventricular ectopic beats are commonly observed in daily clinical practice, either in symptomatic or asymptomatic subjects. In many subjects these arrhythmias are casually detected during a screening visit. Their occurrence is usually associated with no clinical significance. However, in some cases the presence of ventricular ectopic beats indicates susceptibility towards life-threatening arrhythmias or ventricular dysfunction. Appropriate ECG analysis and clinical evaluation are important to detect subjects in whom effective treatment is necessary.

Impact of the Food and Drug Administration approval of flecainide and encainide on coronary artery disease mortality: putting "Deadly Medicine" to the test

In his book Deadly Medicine and on television, Thomas Moore impugns the process of antiarrhythmic drug approval in the 1980s, alleging that the new generation of drugs had flooded the marketplace and had caused deaths in numbers comparable to lives lost during war. To assess these important public health allegations, we evaluated annual coronary artery disease death rates in relation to antiarrhythmic drug sales (2 independent marketing surveys). Predicted mortality rates were modeled using linear regression analysis for 1982 through 1991. Deviations from predicted linearity were sought in relation to rising and falling class IC and overall class I antiarrhythmic drug use. Flecainide came to market in 1986 and encainide in 1987. Combined class IC sales peaked in 1987 and 1988 (maximum market penetration, 20%, first quarter 1989). Results of the Cardiac Arrhythmia Suppression Trial (CAST) were disclosed in April 1989. Overall annual class I antiarrhythmic prescription sales actually fell slightly (-3% to -4%/yr) in the 2 years before CAST and then more abruptly (- 12%) in the year after CAST (1990). Sales of class IC drugs fell dramatically after CAST (by 75%). Coronary death rates (age adjusted) fell in a linear fashion during the decade of 1982 through 1991. No deviation from predicted rates was observed during the introduction, rise, and fall in class IC (and other class I) sales: rates were 126/100,000 in 1985 (before flecainide), 114 and 110 in 1987 and 1988 (maximum sales), and 103 in 1990 (after CAST). Deviations in death rates in the postulated range of 6,000 to 25,000 per year were shown to be excluded easily by the 95% confidence intervals about the predicted rates. Entry of new antiarrhythmic drugs in the 1980s did not lead to overall market expansion and had no adverse impact on coronary artery disease death rates, which fell progressively. Thus, the allegations in Deadly Medicine could not be confirmed.

The Cardiac Arrhythmia Suppression Trial: Implications for nursing practice

BACKGROUND

Care of patients with ventricular arrhythmia after myocardial infarction requires careful nursing management, including assisting with arrhythmia monitoring and testing. Because ventricular premature depolarization is a known risk factor for sudden cardiac death, it was hypothesized that the suppression of asymptomatic or mildly symptomatic ventricular premature depolarization would improve survival in these patients.

OBJECTIVE

To review the Cardiac Arrhythmia Suppression Trial findings and provide implications for nursing practice for patients after myocardial infarction.

METHODS

The Cardiac Arrhythmia Suppression Trial was a multicenter, randomized, placebo-controlled trial designed to determine whether the suppression of ventricular premature depolarizations in postmyocardial infarction patients would improve survival. Three class I antiarrhythmic drugs were used: encainide, flecainide, or moricizine. Patients for whom the drug suppressed their arrhythmia 80% or more were randomly assigned to that drug and dose or its matching placebo and were followed every 4 months (main study). Patients with 1% to 79% suppression were randomly assigned to the drug or its placebo that best treated their arrhythmia and followed every 4 months.

RESULTS

Suppression of asymptomatic or mildly symptomatic ventricular premature depolarization in patients using encainide, flecainide, or moricizine failed to improve patient survival and was even harmful in some cases.

CONCLUSIONS

Our results showed that in the absence of effective antiarrhythmic drug therapy, supportive nursing care and arrhythmia monitoring is important until appropriate therapy for the management of these arrhythmias in patients who have had a myocardial infarction can be found. Clinical trials are essential to provide an evaluation of therapies and direction for further studies, as well as a basis for practicing clinicians.

Antifibrillary action of class I-IV antiarrhythmic agents in the model of ventricular fibrillation threshold of anesthetized guinea pigs

We compared the effects of class I-IV antiarrhythmic agents on the ventricular fibrillation threshold (VFT) induced by electrical stimulation directly on the myocardium in anesthetized, open-chest guinea pigs. VFT was assessed by determining the intensity (mA) of electrical current required to induce ventricular fibrillation (VF) and is expressed as a percentage change of the baseline premedication value. The following antiarrhythmic agents or their solvent were administered intravenously (i.v.) to pentobarbital-anesthetized animals (n = 6-12 per group): class I antiarrhythmic agent encainide (1.5 mg/kg); class II antiarrhythmic agents atenolol (2.5 mg/kg), metoprolol (2.5 mg/kg), and nebivolol (2.5 mg/kg); class III antiarrhythmic agents dofetilide (0.08 mg/kg), terikalant (0.04 mg/kg), and DL-sotalolol (10 mg/kg); and class IV antiarrhythmic agent verapamil (0.16 mg/kg). The antiarrhythmic compounds or their solvents resulted in the following changes in the VFT at 15 min after treatment: saline control, 1 +/- 14% (mean +/- SEM) from its baseline value; 10% hydroxypropyl-beta-cyclodextrine (CD), 4 +/- 13%; encainide, 183 +/- 46% (p < 0.05 vs. saline); atenolol, 66 +/- 23% (p > 0.05 vs. saline); metoprolol, 89 +/- 25% (p > 0.05 vs. saline); nebivolol, 224 +/- 58% (p < 0.05 vs. 10% CD); DL-sotalol, 485 +/- 119% (p < 0.05 vs. saline); dofetilide, 357 +/- 69% (p < 0.05 vs. saline); terikalant, 487 +/- 183% (p < 0.05 vs. saline), and verapamil, -17 +/- 21% (p > 0.05 vs. saline). At the doses used, all compounds significantly reduced heart rate (HR).(ABSTRACT TRUNCATED AT 250 WORDS)

Proarrhythmia of a class Ic drug: suppression by combination with a drug prolonging repolarization in the dog late after infarction

Encainide treatment in patients after myocardial infarction is associated with increased risk of sudden cardiac death. This may relate to drug-induced changes in the electrophysiologic milieu, thus predisposing the patient to sustained ventricular tachyarrhythmias. The goals of this study were to first develop a model of class Ic-induced ventricular tachycardia (VT) and then to design treatments to oppose this prodysrhythmic activity. Dogs with time-dependent loss of inducible sustained VT in the antiarrhythmic drug-free state were studied late after infarction. These dogs received a series of three loading and maintenance infusions of O-demethyl encainide (ODME) to achieve concentrations of 60 +/- 31, 136 +/- 46 and 339 +/- 171 ng/ml. Drug maintenance continued until programmed stimulation induced monomorphic sustained VT. When ODME infusion allowed this induction, barium chloride infusions were added. ODME treatment allowed induction of monomorphic sustained VT in 9 of 10 dogs studied. Prodysrhythmic monomorphic VT was significantly related (P < .01) to prolongation of conduction velocity in the peri-infarct zone. ODME modestly increased ventricular refractoriness at some but not all peri-infarct sites. Infusion of barium chloride in the above nine dogs caused their hearts to return to the noninducible state. Prolongation of refractoriness in the peri-infarct zone was correlated to this suppression of prodysrhythmia. Prolongation of conduction velocity in the absence of substantial prolongation of refractoriness may underlie ODME-facilitated induction of monomorphic VT. Prolongation of refractoriness in the peri-infarct zone by combination treatment with barium chloride reversed prodysrhythmic VT in all of the dogs.

Association between ease of suppression of ventricular arrhythmia and survival

BACKGROUND

We tested the hypothesis that patients whose ventricular arrhythmias are easy to suppress have a lower rate of arrhythmic death, defined as arrhythmic death and nonfatal cardiac arrest, the primary end point in the Cardiac Arrhythmia Suppression Trials (CAST-I and CAST-II), than patients whose ventricular arrhythmias are hard to suppress. In addition, we evaluated the association between ease of suppression of ventricular arrhythmias and mortality of all causes.

METHODS AND RESULTS

CAST-I investigated the effect on arrhythmic death of ventricular premature depolarization (VPD) suppression achieved by three drugs, encainide, flecainide, and moricizine, at two different dose levels; CAST-II investigated the same effect, using moricizine alone at three dose levels. If suppression was achieved, patients were randomized to the effective active drug or corresponding placebo. To examine the independence of easily suppressed ventricular arrhythmias as a predictor of arrhythmic death, we adjusted statistically for other variables that were related both to ease of suppression and arrhythmic death. Patients with ventricular arrhythmias (n = 1778) that were easy to suppress had fewer arrhythmic deaths during follow-up than those with ventricular arrhythmias that were hard to suppress (n = 1173) (relative risk, .59; P = .003). Patients whose VPDs were easily suppressed were older and had a lower frequency of prior history of heart failure and myocardial infarction. They also had a higher incidence of anterior myocardial infarction, VPD frequency, and average ejection fraction. After adjusting for these variables, we found that easily suppressed ventricular arrhythmias were still significant predictors of arrhythmic death (relative risk, .66; P = .013).

CONCLUSIONS

This study shows that the ease of VPD suppression identifies a subgroup of postmyocardial infarction patients who have low risk of arrhythmic death.

Interaction of baseline characteristics with the hazard of encainide, flecainide, and moricizine therapy in patients with myocardial infarction. A possible explanation for increased mortality in the Cardiac Arrhythmia Suppression Trial (CAST)

BACKGROUND

The Cardiac Arrhythmia Suppression Trial (CAST) was designed to test the hypothesis that suppression of ventricular ectopy with antiarrhythmic drugs after a myocardial infarction reduces the incidence of sudden arrhythmic death. Patients in whom ventricular ectopy could be suppressed with encainide, flecainide, or moricizine were randomly assigned to receive either active drug or placebo. The encainide and flecainide arms of the study were discontinued in 1989 (CAST-I) and the moricizine arm in 1991 (CAST-II) because of excess mortality. To explore the mechanisms of these adverse outcomes, we examined the interaction of baseline characteristics with the hazard of therapy with encainide, flecainide, or moricizine compared with their respective placebos.

METHODS AND RESULTS

CAST-I comprised 755 patients assigned to flecainide or encainide and 743 patients assigned to placebo, whereas in CAST-II, 502 patients received moricizine and 491 patients received placebo. Clinical and laboratory baseline variables of patients receiving active drug and those receiving placebo were similar. In CAST-I patients, there was a significant interaction of active therapy with both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest for non-Q-wave myocardial infarction (total mortality hazard ratios, 1.8 versus 7.9 for Q-wave versus non-Q-wave infarction, P = .03). Ventricular premature depolarization (VPD) frequency > or = 50/h and heart rate > or = 74 beats per minute each interacted significantly with total mortality/cardiac arrest only. In the sicker CAST-II patients (ejection fraction < or = 40%), only diuretic use at baseline interacted significantly with moricizine use for both all-cause death/cardiac arrest and arrhythmic death/cardiac arrest (total mortality hazard ratios, 1.9 versus 0.7 for diuretic use versus no use, P = .01).

CONCLUSIONS

Although active treatment in CAST-I was associated with greater mortality than placebo with respect to almost all baseline variables, the therapeutic hazard was more than expected in patients with non-Q-wave myocardial infarction and (for total mortality) frequent premature VPDs and higher heart rates, suggesting that the adverse effect of encainide or flecainide therapy is greater when ischemic and electrical instability are present. The relative hazard of therapy with moricizine in the sicker CAST-II population was greater in those using diuretics. Thus, although these drugs have the common ability to suppress ventricular ectopy after myocardial infarction, their detrimental effects on survival may be mediated by different mechanisms in different populations, emphasizing the complex, poorly understood hazards associated with antiarrhythmic drug treatment.

Predicting mortality after myocardial infarction from the response of RR variability to antiarrhythmic drug therapy

OBJECTIVES

This study was designed to test the hypothesis that antiarrhythmic drugs that decrease RR variability will predict all-cause mortality during follow-up after myocardial infarction.

BACKGROUND

RR variability, a noninvasive indicator of autonomic nervous system activity, predicts death after acute myocardial infarction independently of other risk predictors and changes substantially in response to some drugs. A previous study in patients with chronic heart disease and frequent ventricular premature complexes reported that flecainide decreased vagal modulation of RR intervals but amiodarone did not. The investigators of that study speculated that changes in RR variability during antiarrhythmic drug therapy predict an increased mortality rate during long-term drug treatment. To explore this hypothesis further, we compared the effects of encainide and flecainide, which increase long-term mortality substantially, on RR variability with the effects of placebo and moricizine, which have no significant effect on mortality during long-term treatment of unsustained ventricular arrhythmias after myocardial infarction.

METHODS

The 24-h power spectral density was computed from the baseline electrocardiographic recordings and drug evaluation tapes, and six frequency domain measures of RR variability were calculated: ultra-low frequency (< 0.0033 Hz), very low frequency (0.0033 to < 0.04 Hz), low frequency (0.04 to < 0.15 Hz) and high frequency power (0.15 to < 0.40 Hz), plus total power (< 0.40 Hz) and the ratio of low to high frequency power. Changes in power spectral measures were related to drug treatment and to mortality.

RESULTS

In the placebo group, values for RR interval and RR variability increased because of recovery from the effects of acute myocardial infarction. Contrasting placebo treatment with all three active antiarrhythmic drug treatments taken together showed that of all the measures of RR variability, only NN50, pNN50 and low frequency power changed significantly during drug treatment (Bonferroni adjusted p value < 0.025); these variables all decreased during drug therapy. Contrasting encainide and flecainide with moricizine, we found that the encainide and flecainide groups taken together showed a larger decrease in dLF than moricizine, but the difference was of borderline significance (Bonferroni adjusted p value < 0.08). Survival was significantly worse in the groups treated with encainide and flecainide than in the groups treated with placebo or moricizine (relative risk > 2.0, adjusted p < 0.05). The antiarrhythmic drug-induced change in measures of RR variability was not a significant predictor of all-cause mortality during a year of follow-up after myocardial infarction.

CONCLUSIONS

Encainide, flecainide and moricizine all caused a decrease in RR variability in patients studied approximately 1 month after acute myocardial infarction. Encainide and flecainide caused a significant increase in mortality rates; placebo and moricizine did not. Baseline measurements of RR variability also predicted all-cause mortality after myocardial infarction. The decrease in RR variability produced by the three antiarrhythmic drugs did not predict mortality during follow-up.

Circadian pattern of arrhythmic death in patients receiving encainide, flecainide or moricizine in the Cardiac Arrhythmia Suppression Trial (CAST)

OBJECTIVES

The purpose of this study was to assess the effect of antiarrhythmic drugs on the timing of arrhythmic death.

BACKGROUND

Sudden cardiac death remains a problem of epidemic proportions. Delineating its pathophysiology is an important step in devising preventive measures. Previous studies have shown a circadian pattern of onset of sudden cardiac death. The effect of antiarrhythmic drugs on this pattern has not been systematically studied.

METHODS

The Cardiac Arrhythmia Suppression Trial (CAST) was a multicenter double-blind, placebo-controlled study designed to determine whether suppression of ventricular ectopic activity by means of antiarrhythmic drugs (encainide, flecainide or moricizine) after acute myocardial infarction would reduce the incidence of arrhythmic death.

RESULTS

The trial was terminated prematurely because of an unexpectedly high mortality rate in the active treatment group. The onset of arrhythmic death in this group (in patients not receiving beta-adrenergic blocking agents) displayed a bimodal variation, with significant peaks in midmorning and late afternoon/early evening. More than half of the symptomatic events were accompanied by anginalike symptoms. Approximately 30% of all events occurred within 2 h of awakening.

CONCLUSIONS

Our data suggest the possibility of a complex interaction among antiarrhythmic drugs, sympathetic nervous system activation and acute myocardial ischemia. Planning of future antiarrhythmic drug trials will need to take this information into account.

Efficacy of type 1C antiarrhythmic agents for treatment of resistant atrial fibrillation

In order to determine the efficacy of type 1C agents (flecainide, encainide, propafenone) in patients with atrial fibrillation who have failed to maintain sinus rhythm with type 1A agents (quinidine, procainamide, disopyramide), 147 patients, that were admitted into the John Dempsey Hospital with new or recurrent atrial fibrillation between 1987-1991, were studied retrospectively. Out of the total, 29 patients converted spontaneously to sinus rhythm, 14 patients were left in atrial fibrillation, and 104 patients were given a type 1A antiarrhythmic. Sixty-five of these patients remained in sinus rhythm (54% converted on drug alone, 46% required electrical cardioversion) for at least 6 months. Of the remaining 39 patients, 28 were given a type 1C antiarrhythmic; 13 were successfully converted (61% chemical, 39% electrical) to and remained in sinus rhythm for at least 6 months; the remaining 15 either failed to convert or reverted to atrial fibrillation. New onset atrial fibrillation had a significantly lower incidence of congestive heart failure (10%) than recurrent atrial fibrillation (33%; P < 0.01). No differences in digoxin, beta blocker use, or other clinical characteristics were seen either between type 1A or type 1C successes or failures. Similarly, echocardiographic dimensions did not predict success or failure with either class of agent. In conclusion, type 1C antiarrhythmics for suppression of recurrent atrial fibrillation represent a reasonable therapeutic alternative for suppression of atrial fibrillation in patients who have failed type 1A agents. Prognostic factors predicting success or failure remain undetermined.

Mortality following ventricular arrhythmia suppression by encainide, flecainide, and moricizine after myocardial infarction. The original design concept of the Cardiac Arrhythmia Suppression Trial (CAST)

OBJECTIVE

To test the hypothesis that in survivors of myocardial infarction, the suppression of ventricular premature depolarizations improves survival free of cardiac arrest and arrhythmic death.

DESIGN

International, prospective, multicenter, randomized, placebo-controlled trial.

SETTING

University and community hospitals.

PATIENTS

A total of 3549 patients with myocardial infarction and left ventricular dysfunction.

INTERVENTION

Administration of encainide, flecainide, moricizine, or placebo to suppress ventricular premature depolarizations.

MAIN OUTCOME MEASURES

Overall survival and survival free of cardiac arrest or arrhythmic death were compared in patients randomized to long-term, active antiarrhythmic drug therapy vs corresponding placebo, using the stratified log rank statistic.

RESULTS

At 1 year from the time of randomization to blinded therapy, 95% of placebo-treated patients vs 90% of active drug-treated patients remained alive (P = .0006). Similarly, at 1 year, 96% of placebo-treated patients vs 93% of active drug-treated patients remained free of cardiac arrest or arrhythmic death (P = .003).

CONCLUSIONS

The suppression of asymptomatic or mildly symptomatic ventricular arrhythmias after myocardial infarction does not improve survival and can increase mortality. Treatment strategies designed solely to suppress these arrhythmias should no longer be followed.

Efficacy of class 1C antiarrhythmic agents in patients with inducible ventricular tachycardia refractory to therapy with class 1A antiarrhythmic drugs

The efficacy of class 1C antiarrhythmic agents was determined in 36 patients with inducible sustained monomorphic ventricular tachycardia during baseline electrophysiology study (EPS), who continued to have inducible monomorphic ventricular tachycardia during EPS on class 1A antiarrhythmic therapy. Of 12 patients who partially responded to class 1A drugs, 11 (91.7%) continued to have a partial response during EPS on class 1C therapy, whereas one patient did not respond. Of 24 nonresponders to class 1A therapy, 2 (8.3%) responded during EPS on class 1C therapy, 7 (29.2%) partially responded, and 15 (62.5%) did not respond. In the 24 nonresponders to class 1A therapy, 9 of 17 patients (53%) with left ventricular ejection fraction (EF) > or = 30% responded or partially responded to class 1C therapy, compared with none of 7 patients with EF < 30% (P < .05). The EPS on class 1C agents in patients who fail to respond to class 1A therapy may be warranted only in those with EF > or = 30%.

Demonstration of proarrhythmic activity with the class IC antiarrhythmic agent encainide in a canine model of previous myocardial infarction

The antiarrhythmic efficacy and proarrhythmic potential of the class IC antiarrhythmic agent encainide were assessed in subacute and chronic postinfarction canine models, respectively. In conscious dogs with spontaneous premature ventricular complexes (PVCs) at 48 h after anterior myocardial infarction (MI), cumulative intravenous (i.v.) administration of 1.0 and 3 mg/kg encainide significantly reduced PVC frequency. However, in anesthetized dogs studied more chronically after anterior MI (range 8-44 days), i.v. administration of 0.3-3 mg/kg encainide resulted in induction of new ventricular tachyarrhythmias by programmed ventricular stimulation in 6 of 10 dogs with no inducible arrhythmias prior to encainide. Newly induced arrhythmias after encainide administration included unimorphic and polymorphic ventricular tachycardia (VT) as well as VT degenerating rapidly into ventricular fibrillation (VF). The incidences of new arrhythmia induction after cumulative i.v. administration of encainide were 3 of 9 after 0.3 mg/kg i.v. encainide, 4 of 9 after 1.0 mg/kg i.v. encainide, and 5 of 10 after 3.0 mg/kg i.v. encainide. Time elapsed between MI and electrophysiologic testing tended to predict proarrhythmic response to encainide, with the six preparations with newly induced arrhythmias tested earlier than the four preparations that remained nonresponsive to postencainide programmed stimulation (13.2 +/- 3.1 vs. 26.5 +/- 6.5 days postinfarction, respectively, p = 0.07). There was also a trend toward larger underlying anterior MIs in the six preparations with newly induced arrhythmias as compared with the four preparations that remained nonresponsive to postencainide programmed stimulation (13.2 +/- 2.9 vs. 7.5 +/- 2.1% of left ventricle, respectively, p = 0.19).(ABSTRACT TRUNCATED AT 250 WORDS)

Psychosocial predictors of mortality in the Cardiac Arrhythmia Suppression Trial-1 (CAST-1)

Psychosocial variables predict the recurrence of clinical events in symptomatic patients, controlling for measures of disease severity. The Cardiac Arrhythmia Suppression Trial-1, a pharmacologic test of the arrhythmia suppression and mortality hypothesis among postmyocardial infarction patients, allowed a prospective test of the relationship of distress, perceived support, social interaction, life stress, and other variables, to mortality, adjusting statistically for ejection fraction, arrhythmia rates, and other known risk factors for coronary heart disease. Results indicated that the treatment medications, encainide and flecainide, were powerful predictors of mortality. Although the psychosocial variables were significant as univariate predictors, these variables were not significant as predictors in a multivariate model that included drug treatment. When the data analysis was restricted to patients randomized to placebo, thereby eliminating the antiarrhythmic drug effect, the level of perceived social support was a significant multivariate predictor of mortality, adjusting for measures of disease severity. The adjusted hazards ratio for a 1-point decrease in the perceived support score is equal to 1.46, based on the multivariate model.

Effects of advancing age on the efficacy and side effects of antiarrhythmic drugs in post-myocardial infarction patients with ventricular arrhythmias. The CAST Investigators

OBJECTIVE

To determine the effect of age on the response to anti-arrhythmic drugs.

DESIGN

Randomized controlled trial comparing particular drugs.

SETTING

Multi-institutional (The Cardiac Arrhythmia Suppression Trial, CAST).

PARTICIPANTS

2,371 patients, age less than 80, with ventricular arrhythmias after a recent myocardial infarction. Subjects classified by age as less than or equal to 55, 56-65, and 66-79 years.

INTERVENTION

Upwardly titrated doses of encainide, flecainide or moricizine. After identification of a tolerated and effective dose of one of the drugs, participants were randomized to that drug and dose versus its placebo for up to 10 months.

MAIN OUTCOME MEASURES

Efficacy of drug (suppression of ventricular premature depolarizations and/or non-sustained ventricular tachycardia), side effects and mortality.

RESULTS

Older patients had more previous MIs, congestive heart failure (CHF), hypertension, NSVT, repolarization abnormalities, digitalis use, and diuretic use. They had less pathologic Q-waves or electrocardiographic injury pattern, and their left ventricular ejection fraction (LVEF) was lower. First dose VPD suppression with the first drug averaged 53% and is not associated with age (P = 0.29). Adverse events including death are more frequent in older patients taking study drugs (P less than 0.001). This trend is consistent in all three study drugs and at varying LVEFs. History of prior MI, low LVEF, VPD (in log scale), and digitalis therapy also correlates with adverse events (all P less than 0.05). Following adjustment for these factors, older age is an independent predictor of adverse events (relative risk 1.30 per decade of age, P less than 0.001).

CONCLUSIONS

Older age increases the susceptibility to adverse cardiac events from a class of relatively toxic antiarrhythmic agents.

The Cardiac Arrhythmia Suppression Trial: first CAST ... then CAST-II

The Cardiac Arrhythmia Suppression Trial (CAST) was a study designed to test the hypothesis that suppression of ventricular premature complexes after a myocardial infarction would improve survival. Preliminary results showed that suppression of ventricular premature complexes with encainide and flecainide worsened survival, and the CAST continued as the CAST-II with moricizine compared with its placebo. The protocol for the CAST-II was changed to attempt to enroll patients more likely to experience serious arrhythmias. The enrollment time was narrowed to 4 to 90 days after myocardial infarction; the qualifying ejection fraction was lowered to less than or equal to 0.40; a higher dose of moricizine could be used; early titration itself was double-blind with a placebo, and the definition of disqualifying ventricular tachycardia was changed to allow patients with more serious arrhythmias to be entered into the trial. The Cardiac Arrhythmia Suppression Trial-II was subsequently terminated prematurely because 1) patients treated with moricizine had an excessive cardiac mortality rate during the 1st 2 weeks of exposure to the drug, and 2) there appeared to be little chance of showing a long-term survival benefit from treatment with moricizine. This report outlines the rationale behind the Cardiac Arrhythmia Suppression Trial and the reasons for selection of the drugs used in the CAST and CAST-II.

Encainide dosing in patients with severe renal dysfunction: report of a case and literature review

Dosage of encainide for patients with lethal ventricular arrhythmias is based on pharmacodynamic effects and efficacy of arrhythmia suppression, coupled with metabolizer phenotype and extent of renal and hepatic dysfunction. Decreased clearance in patients with renal dysfunction necessitates a reduction in dosage to avoid toxic and dose-related proarrhythmic effects. This case represents a patient with severe renal dysfunction and sustained ventricular tachycardia who achieved electrophysiologically guided suppression of induced ventricular tachycardia at a steady-state encainide dose of only 25 mg daily, significantly lower than package insert or compendial recommendations for initial dosage in patients with renal insufficiency. Documented "therapeutic" metabolite concentrations correlated to electrophysiologic response. Literature review illustrates the complexity of encainide dosage in such individuals and underscores the need for therapeutic drug monitoring to individualize dosage.

[What is the latest in anti-arrhythmia therapy?]

Ventricular premature beats are an independent risk factor for sudden cardiac death. Class Ic antiarrhythmic drugs suppress these premature contractions. The Cardiac Arrhythmia Suppression Trial (CAST-Trial) tested the hypothesis that the suppression of ventricular premature beats after myocardial infarction reduces the incidence of cardiac death. The results of treatment in this low risk group were, however, disappointing. Cardiac mortality (mortality related to arrhythmia and myocardial infarction) was higher in the group treated with flecainide or encainide than in the placebo group. After a treatment period of 10 months, 89 of 1498 patients had died, 63 (8.3%) of them in the flecainide/encainide and only 26 (3.5%) in the placebo-treated group. Drugs that increase the refractory period of a myocardial substrate are obviously more effective in suppressing cardiac death than drugs that delay conduction. In the Basel Antiarrhythmic Study of Infarct Survival (BASIS study) patients with complex ventricular arrhythmias after infarction were treated with low dose amiodarone (200 mg/day). After a follow-up period of 12 months, mortality was lower in the amiodarone treated group (5/98 patients, 5%) than in the group that received no antiarrhythmic treatment (15/114 patients, 13%). Amiodarone was also more beneficial than individual antiarrhythmic therapy (mortality 10/100 patients, 10%). In the past few years no new antiarrhythmic drugs have been registered in Switzerland. Our pathophysiological and clinical knowledge has, however, increased and we know that the asymptomatic patient with low grade ventricular ectopies after myocardial infarction need not be treated. However, if we decide to use antiarrhythmic drugs, strict quality control of the effects of the treatment is mandatory.(ABSTRACT TRUNCATED AT 250 WORDS)

Events in the cardiac arrhythmia suppression trial: baseline predictors of mortality in placebo-treated patients

Patients randomized to placebo in the encainide and flecainide arms of the Cardiac Arrhythmia Suppression Trial (CAST) have been found to have a relatively low 1-year mortality rate of 3.9% in comparison with previous studies of patients in the postmyocardial infarction period. To determine the comparability of CAST with previous studies, baseline variables were examined in the 743 patients randomized to placebo in the flecainide and encainide arms of CAST. Twenty-three baseline characteristics were correlated with major outcome events: arrhythmic death (16 events), total mortality (26 events) and congestive heart failure (51 events). On multivariate analysis the risk of new or worsening congestive heart failure was significantly associated with diuretic use, diabetes, high New York Heart Association functional class, age, prolonged QRS duration and low ejection fraction. The risk of arrhythmic death or resuscitated cardiac arrest was significantly associated with an index Q wave myocardial infarction, history of heart failure, use of digitalis, diabetes and prolonged QRS duration. Total mortality or resuscitated cardiac arrest was significantly associated with an index Q wave myocardial infarction, diabetes, ST segment depression, high functional class, prolonged QRS duration and low ejection fraction. The variables at baseline associated with mortality from all causes or arrhythmic death or resuscitated cardiac arrest and heart failure in the CAST placebo-treated patients are similar to those identified in previous postmyocardial infarction studies. Thus, the observation of increased mortality in CAST associated with the administration of encainide and flecainide for suppression of ventricular premature depolarizations is probably applicable to any comparably defined group of patients in the postmyocardial infarction period.

Prevalence, characteristics and significance of ventricular premature complexes and ventricular tachycardia detected by 24-hour continuous electrocardiographic recording in the Cardiac Arrhythmia Suppression Trial. CAST Investigators

The prevalence, characteristics and significance of ventricular arrhythmias detected by ambulatory electrocardiography were evaluated in 1,498 patients who were randomized to encainide, flecainide or placebo in the Cardiac Arrhythmia Suppression Trial. The mean ventricular premature complex (VPC) frequency at baseline was 133 +/- 257 VPCs/hour. Nonsustained ventricular tachycardia (VT) (rate greater than or equal to 120 beats/min) was present in 22% of patients. Accelerated idioventricular rhythm (rate less than 120 beats/min) occurred in 22% of subjects. There were 63 deaths/resuscitated cardiac arrests in the active treatment (encainide/flecainide) group and 26 in the placebo group. In the treatment group mortality increased with increasing VPC frequency, (p = 0.006), whereas in the placebo group such a relation was not present. Mortality/resuscitated cardiac arrest increased in patients with greater than or equal to 2 VT episodes than in those with less than or equal to 1 episode in the active treatment group (p = 0.04). There was no significant association between VT and mortality/resuscitated cardiac arrest in the placebo group. The presence of accelerated idioventricular rhythm was not associated with increased mortality/resuscitated cardiac arrest in either the active treatment or placebo groups. However, mortality was lower in patients with accelerated idioventricular rhythm rates less than 100 beats/min than in those with rates greater than or equal to 100 beats/min (p = 0.05). Thus, in the Cardiac Arrhythmia Suppression Trial the previously described association between mortality/resuscitated cardiac arrest and ventricular arrhythmias (VPC and VT) were only observed in the active treatment group. In addition, based on the results obtained in this highly selected population, it is suggested that the definition of accelerated idioventricular rhythm should be a rate less than 100 beats/min, and at a rate greater than or equal to 100 beats/min it should be categorized as VT.

Intravenous 3-methoxy-O-desmethyl-encainide in reentrant supraventricular tachycardia: a randomized double-blind placebo-controlled trial in patients undergoing EP study

Encainide is an agent effective in atrioventricular and atrioventricular nodal reentrant tachycardia. The metabolites O-desmethyl encainide and 3-methoxy-O-desmethyl encainide (MODE) are responsible for the clinical effects of encainide in most patients. In this study, intravenous MODE was evaluated in eight patients with reentrant supraventricular tachycardia undergoing electrophysiological testing. After tachycardia was induced at least twice to ensure reproducibility, MODE (30 micrograms/kg/min x 15 min, then 7.5 micrograms/kg/min) or placebo was administered in a double-blind fashion. If tachycardia remained inducible, the infusion was unblinded; in nonresponding subjects who received placebo, MODE was then administered. Placebo was ineffective in 3/3 patients. MODE prevented tachycardia induction in 5/8 patients and increased the tachycardia cycle length from 302 +/- 38 to 413 +/- 67 msec in the other three. At a mean concentration of 774 +/- 229 ng/ml, MODE prolonged PR, AH, HV, QRS, and QT intervals, right ventricular and accessory pathway effective refractory periods, and slowed or blocked antegrade accessory pathway conduction. Changes in intracardiac conduction were rate independent between cycle lengths 400 to 600 msec, while changes in ventricular effective refractory periods were most pronounced at rapid pacing rates. No adverse effects, hemodynamic changes, or conduction disturbances occurred. Thus, MODE can modify or suppress induction of reentrant atrioventricular or atrioventricular nodal tachycardia. The study design used here is well suited for the evaluation of newer antiarrhythmic agents by electrophysiological testing.

A critical appraisal of the cardiac arrhythmia suppression trial (CAST)

The presence of ventricular ectopic activity in the post-myocardial infarction patient, especially associated with left ventricular dysfunction, has been associated with a high incidence of sudden cardiac death. To test the PVC hypothesis, that PVC suppression in asymptomatic patients with ventricular arrhythmias post-myocardial infarction might reduce sudden death rate, the cardiac arrhythmia suppression trial (CAST) was performed. In patients treated with encainide or flecainide, total mortality at 10 months was 7.7% compared to only 3% overall mortality on placebo. The increase in mortality and sudden cardiac death with these two drugs raised the question of whether PVC suppression in this group of patients should be attempted. In addition, the extrapolation of the results of this study to other patient groups has resulted in a change of our antiarrhythmic prescription habits. Criticism of the CAST study has included a low placebo mortality, which may have been secondary to entry of low-risk groups of patients, deaths in the open label titration groups not being included, and recent advances in thrombolysis and revascularization. In addition, this low placebo mortality may have been explained by the concept that drug-responsive arrhythmias may have more benign prognosis. The above results suggest that, except for the use of beta blockers, benefits of other anti-arrhythmic drug treatment in the post-infarction patient with asymptomatic benign and potentially lethal ventricular arrhythmias is questionable. Flecainide and encainide should be avoided in this group of patients.(ABSTRACT TRUNCATED AT 250 WORDS)