Efficacy and Safety of the Additional Bepridil Treatment in Patients With Atrial Fibrillation Refractory to Class I Antiarrhythmic Drugs

BACKGROUND

Bepridil has multiple ion-channel blocking effects and is expected to be useful for managing atrial fibrillation (AF). The purpose of this study was to clarify the efficacy and safety of additional treatment with bepridil in patients with AF who had been treated with class I antiarrhythmic drugs (AADs).

METHODS AND RESULTS

Bepridil (50-200 mg/day) was given to 76 patients with either paroxysmal (n=49) or persistent AF (n=27). All patients had been treated with class I AADs (1.9+/-0.9 drugs/patient) that failed to control the AF. With the addition of bepridil, the frequency of symptomatic AF episodes decreased to less than 10% in 38 (78%) patients with paroxysmal AF, and sinus rhythm was restored within 3 months and maintained during the follow-up in 20 (74%) patients with persistent AF. Efficacy was usually obtained with a small to moderate dose (50-150 mg/day) of bepridil. During a mean follow-up period of 27+/-22 months, no potential complications occurred in any of the patients.

CONCLUSIONS

The addition of bepridil to class I AADs is effective and safe for AF, but careful observation using periodic ECG recordings is essential for avoiding torsades de pointes caused by QT prolongation.

Genotype-specific onset of arrhythmias in congenital long-QT syndrome: possible therapy implications

BACKGROUND

The identification of the molecular-genetic substrate underlying the various forms of the congenital long-QT syndrome (LQTS) has sparked studies into possible genotype-phenotype correlations with the aim of developing genotype-tailored therapy. The onset of torsade de pointes (TdP) may differ among LQTS patients, being pause dependent in some but not all. This disparity may point to different arrhythmia mechanisms and may affect therapy strategies. We studied whether the proportion of pause-dependent TdP onset varies among LQTS genotypes.

METHODS AND RESULTS

We studied all LQT1 (n=10), LQT2 (n=34), and LQT3 (n=6) patients from 4 centers for whom ECGs of TdP onset were available and analyzed whether pauses preceded TdP onset (first available ECG per patient). Pauses preceded TdP significantly more often in LQT2 (68%) than in LQT1 (0%), and the interval immediately before TdP (pause interval) was significantly longer in LQT2 than in LQT1. The proportion of pause dependence in LQT3 (33%) appeared intermediate, but this group was too small for statistical analysis.

CONCLUSIONS

Pause dependence of TdP onset is predominant in LQT2 but absent or rare in LQT1. It is suggested that disparities in pause dependence of TdP onset may reflect different arrhythmia mechanisms.

K201, a multi-channel blocker, inhibits clofilium-induced torsades de pointes and attenuates an increase in repolarization

K201 (JTV519) is a 1,4-benzothiazepine derivative that exhibits a strong cardioprotective action and acts as a multiple-channel blocker, including as a K+ channel blocker. An experimental model of prolongation of the QT interval and torsades de pointes can be induced in rabbits by treatment with clofilium in the presence of the alpha1-adrenoreceptor agonist methoxamine. In this study we examined the effects of K201 with and without methoxamine on the QT and QTc intervals, and determined whether K201 inhibits clofilium-induced torsades de pointes in the presence of methoxamine (15 microg/kg/min) in rabbits (n=74). Administration of K201 (0, 40, 100, 200 and 400 microg/kg/min) with and without methoxamine prolonged the QT interval in a dose-dependent manner, and torsades de pointes did not occur in any animals. However, clofilium (50 microg/kg/min) with methoxamine induced torsades de pointes in all animals (6/6). Torsades de pointes occurred at rates of 100%, 67%, 40% and 0% at K201 concentrations of 0, 50, 200 and 400 microg/kg/min, respectively, in the clofilium-infused torsades de pointes model. Therefore, 400 microg/kg/min of K201 completely inhibited clofilium-induced torsades de pointes and attenuated the increase of repolarization caused by clofilium; the inhibitory effects of K201 may be related to its pharmacological properties as an alpha1-adrenoceptor blocker. Overall, our results show that K201 causes prolongation of the QT and QTc intervals, but does not induce torsades de pointes, with and without alpha1-adrenoceptor stimulation. Furthermore, K201 inhibits clofilium-induced torsades de pointes, despite QT prolongation, suggesting that QT prolongation alone is not a proarrhythmic signal.

Pharmacokinetic-pharmacodynamic modelling of QT interval prolongation following citalopram overdoses

AIMS

To develop a pharmacokinetic-pharmacodynamic model describing the time-course of QT interval prolongation after citalopram overdose and to evaluate the effect of charcoal on the relative risk of developing abnormal QT and heart-rate combinations.

METHODS

Plasma concentrations and electrocardiograph (ECG) data from 52 patients after 62 citalopram overdose events were analysed in WinBUGS using a Bayesian approach. The reported doses ranged from 20 to 1700 mg and on 17 of the events a single dose of activated charcoal was administered. The developed pharmacokinetic-pharmacodynamic model was used for predicting the probability of having abnormal combinations of QT-RR, which was assumed to be related to an increased risk for torsade de pointes (TdP).

RESULTS

The absolute QT interval was related to the observed heart rate with an estimated individual heart-rate correction factor [alpha = 0.36, between-subject coefficient of variation (CV) = 29%]. The heart-rate corrected QT interval was linearly dependent on the predicted citalopram concentration (slope = 40 ms l mg(-1), between-subject CV = 70%) in a hypothetical effect-compartment (half-life of effect-delay = 1.4 h). The heart-rate corrected QT was predicted to be higher in women than in men and to increase with age. Administration of activated charcoal resulted in a pronounced reduction of the QT prolongation and was shown to reduce the risk of having abnormal combinations of QT-RR by approximately 60% for citalopram doses above 600 mg.

CONCLUSION

Citalopram caused a delayed lengthening of the QT interval. Administration of activated charcoal was shown to reduce the risk that the QT interval exceeds a previously defined threshold and therefore is expected to reduce the risk of TdP.

Calmodulin antagonist W-7 prevents sparfloxacin-induced early afterdepolarizations (EADs) in isolated rabbit purkinje fibers: importance of beat-to-beat instability of the repolarization

INTRODUCTION

The occurrence of early afterdepolarizations (EADs) has been related to the incidence of torsades de pointes in drug-induced long QT (LQT). The generation of EADs may be facilitated by Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase).

METHODS AND RESULTS

In the present study, we investigated a possible involvement of Ca(2+)/Calmodulin dependent protein kinase in the generation of sparfloxacin-induced EADs in isolated rabbit Purkinje fibers by means of a calmodulin antagonist W-7. EADs were evident in 8 of the 10 preparations perfused with sparfloxacin at 1 x 10(-4) M and stimulated at 0.2 Hz. The induction of EADs by sparfloxacin was associated with a large prolongation of the duration of the action potential (APD), an increase in the triangulation, and the short-term instability of the repolarization. CaM kinase blockade with the calmodulin antagonist W-7 inhibited sparfloxacin-induced EADs in a concentration-dependent manner (EADs were induced in 3 of 10, 1 of 10, and 0 of 8 preparations in the presence of W-7 at 5 x 10(-7) M, 5 x 10(-6) M, and 5 x 10(-5) M, respectively; P < 0.01 at 5 x 10(-6) M and 5 x 10(-5) M). The inhibition of sparfloxacin-induced EADs by W-7 at 5 x 10(-7) M and 5 x 10(-6) M was associated with a significant decrease in the beat-to-beat instability but not associated with a significant shortening of the APD and reduction of V(max).

CONCLUSION

The present findings support the hypothesis that CaM kinase may be a proarrhythmic signaling molecule and demonstrate that CaM kinase may be involved in the generation of EADs in drug-induced LQT and enhanced beat-to-beat instability of repolarization is essential for the genesis of EADs in rabbit in vitro.

Beat-to-Beat variability of repolarization determines proarrhythmic outcome in dogs susceptible to drug-induced torsades de pointes

OBJECTIVES

We investigated whether increasing or decreasing beat-to-beat variability of repolarization (BVR) would change drug-induced proarrhythmic outcome accordingly.

BACKGROUND

Increased variability of repolarization has been suggested as a prelude to proarrhythmic circumstances in experimental and clinical situations.

METHODS

The non-cardiovascular, I(Kr)-blocking drug sertindole was administered to anesthetized dogs with chronic atrioventricular block. Three interventions were used to prevent or suppress sertindole-induced torsades de pointes (TdP).

RESULTS

Supratherapeutic doses of sertindole (1.0 mg/kg intravenously) induced TdP in 10 of 13 dogs whereas 0.2 mg/kg induced no TdP, despite increases in QT intervals by both doses. The BVR, quantified as short-term variability (STV) from Poincaré plots, was the only parameter that predicted TdP outcome (1.0 mg/kg sertindole: 2.3 +/- 0.7 ms to 5.1 +/- 2.1 ms, p < 0.05; 0.2 mg/kg sertindole: 2.3 +/- 0.8 ms to 3.2 +/- 1.1 ms, p= NS).

INTERVENTIONS

1) KCl, intravenous, reduced the incidence of sertindole-induced TdP from 6 of 7 to 1 of 7 dogs (p<0.05) and prevented sertindole-related increase of STV: 3.0 +/- 1.1 ms vs. 4.5 +/- 1.3 ms (p < 0.05); 2) levcromakalim (I(K,ATP) activator) reduced sertindole-induced TdP and decreased STV from 4.9 +/- 2.1 ms to 2.6 +/- 0.9 ms (p < 0.05); 3) steady-state ventricular pacing (60 beats/min) abolished sertindole-induced TdP and decreased STV from 4.9 +/- 1.5 to 3.2 +/- 1.0 (p < 0.05). Torsades de pointes reappeared upon return to non-paced idioventricular rhythm. None of the 3 interventions reduced the sertindole-induced prolonged QT interval.

CONCLUSIONS

Proarrhythmic intervention is related to an increase in BVR, whereas antiarrhythmic treatment is associated with a decrease in BVR. The BVR is superior to QT interval prolongation in the prediction and prevention of drug-induced TdP in this experimental model.

Atrial-specific drug AVE0118 is free of torsades de pointes in anesthetized dogs with chronic complete atrioventricular block

BACKGROUND

The novel compound AVE0118 has been shown to prevent and terminate persistent atrial fibrillation. AVE0118 blocks I(Kur), I(KAch), and I(to), leading to prolongation of atrial repolarization with no change in ventricular repolarization. This finding suggests that AVE0118 may be devoid of proarrhythmic side effects. Experimentally, AVE0118 has been antiarrhythmic against some specific ventricular arrhythmias.

OBJECTIVES

The purpose of this study was to investigate the proarrhythmic and antiarrhythmic effects of AVE0118 in anesthetized dogs with chronic complete AV block, known for a high proclivity for torsades de pointes (TdP).

METHODS

AVE0118 was administered intravenously as a fast infusion (0.5 mg/kg/5 min) and a slow infusion (3 or 10 mg/kg/60 min). Dofetilide was given to induce TdP. ECG and monophasic action potentials were recorded. Short-term beat-to-beat variability (STV) of the left ventricular monophasic action potential duration (MAPD) was calculated. We examined whether AVE0118 (1) caused ventricular proarrhythmia (both infusions), (2) prevented dofetilide-induced TdP (slow infusion + dofetilide after 30 minutes), and (3) abolished TdP (fast infusion).

RESULTS

At 0.55 +/- 0.10 microg/mL (fast infusion at 10 minutes), AVE0118 did not increase ventricular repolarization or induce TdP; however, right atrial MAPD(50) and MAPD(90) were significantly increased by 26% +/- 9% and 10% +/- 5%, respectively (P <.05 vs baseline). At 1.9 +/- 0.5 microg/mL and 6.1 +/- 1.2 microg/mL (30 minutes of 3 or 10 mg/kg/h), AVE0118 did not induce TdP (0/6 and 0/4) nor prevent dofetilide-induced TdP (6/6 and 2/2). Dofetilide significantly increased all repolarization parameters, including STV from 2.1 +/- 0.4 ms to 4.6 +/- 1.8 ms (P <.05 vs baseline), which were not changed by AVE0118 (to 2.1 +/- 0.3 ms after 30 minutes). Rapid infusion of AVE0118 did not suppress dofetilide-induced TdP.

CONCLUSION

In the anesthetized chronic complete AV block dog, the atrial-specific drug AVE0118 is free of TdP and has no antiarrhythmic properties against dofetilide-induced torsades de pointes.

An overview of QT interval assessment in safety pharmacology

Medicinal products that prolong cardiac repolarization unintentionally, as assessed in terms of prolongation of the QT interval of the electrocardiogram, may trigger a potentially fatal arrhythmia called torsade de pointe (TDP). This lethal risk necessitates a detailed preclinical evaluation before initiating clinical trials. There are two different and complementary approaches to assess the potential of drugs to cause QT interval prolongation. The in vivo approach provides information on the potential of the compound to prolong the QT interval under near-physiological conditions. It is mostly descriptive and not explanatory in terms of mechanisms of action. The in vitro approach provides much more mechanistic information, but is far removed from the clinical situation. While both approaches appear to possess reasonable predictive value, the results may depend largely on the experimental conditions employed. This unit reviews these issues and discusses a strategy aimed at understanding the problems associated with this cardiovascular risk.

Drug-induced q-T prolongation

Drug therapy may induce Q-T prolongation by alteration of potassium ion currents in cardiac cells, resulting in abnormal repolarization. Q-T prolongation, whether congenital or acquired, has been associated with the development of the malignant dysrhythmia Torsade de Pointes (TdP), which may result in sudden death. Re-cent regulatory actions and drug withdrawals due to Q-T prolongation or TdP have focused attention on this issue. Although our understanding of the pathophysiology continues to evolve, both patient and medication factors contribute to the individual risk of drug-induced Q-T prolongation or TdP. The clinician should be aware of these issues when prescribing new drugs and should weigh the risks and benefits carefully when prescribing drugs known to prolong the Q-T interval.

Verapamil prevents torsade de pointes by reduction of transmural dispersion of repolarization and suppression of early afterdepolarizations in an intact heart model of LQT3

BACKGROUND

In long QT syndrome (LQTS), prolongation of the QT-interval is associated with sudden cardiac death resulting from potentially life-threatening polymorphic tachycardia of the torsade de pointes (TdP) type. Experimental as well as clinical reports support the hypothesis that calcium channel blockers such as verapamil may be an appropriate therapeutic approach in LQTS. We investigated the electrophysiologic mechanism by which verapamil suppresses TdP, in a recently developed intact heart model of LQT3.

METHODS AND RESULTS

In 8 Langendorff-perfused rabbit hearts, veratridine (0.1 microM), an inhibitor of sodium channel inactivation, led to a marked increase in QT-interval and simultaneously recorded monophasic ventricular action potentials (MAPs) (p < 0.05) thereby mimicking LQT3. In bradycardic (AV-blocked) hearts, simultaneous recording of up to eight epi- and endocardial MAPs demonstrated a significant increase in total dispersion of repolarization (56%, p < 0.05) and reverse frequency-dependence. After lowering potassium concentration, veratridine reproducibly led to early afterdepolarizations (EADs) and TdP in 6 of 8 (75%) hearts. Additional infusion of verapamil (0.75 microM) suppressed EADs and consecutively TdP in all hearts. Verapamil significantly shortened endocardial but not epicardial MAPs which resulted in significant reduction of ventricular transmural dispersion of repolarization.

CONCLUSIONS

Verapamil is highly effective in preventing TdP via shortening of endocardial MAPs, reduction of left ventricular transmural dispersion of repolarization and suppression of EADs in an intact heart model of LQT3. These data suggest a possible therapeutic role of verapamil in the treatment of LQT3 patients.

Sex Modulates the Arrhythmogenic Substrate in Prepubertal Rabbit Hearts with Long QT 2

Females have a greater susceptibility to Torsade de Pointes in congenital and drug-induced long QT syndrome (LQTS) that has been attributed to the modulation of ion channel expression by sex hormones. However, little is known regarding sex differences in pre-puberty, that is, before the surge of sexual hormones. In patients with congenital LQTS types 1 and 2, male children tend to have a greater occurrence of adverse events, especially in 10-15 year olds, than their female counterpart. To evaluate whether the rabbit model of drug-acquired LQTS exhibits similar age dependences, hearts of prepubertal rabbits were perfused, mapped optically to record action potentials (APs) and treated with an I(Kr) blocker, E4031 to elicit LQTS2. As expected, AP durations (APD) were significantly longer in female (n = 18) than male hearts (n = 10), at long cycle length. Surprisingly, E4031 (50-250 nM) induced a greater prolongation of APDs in male than in female hearts, and in both genders reversed the direction of repolarization (apex --> base to base --> apex), enhancing dispersions of repolarization. Furthermore, in male hearts, E4031 (0.5 microM) elicited early afterdepolarizations (EADs) that progressed to polymorphic ventricular tachycardia (PVT) (n = 7/10) and were interrupted by isoproterenol (40 nM) and prevented by propranolol (0.5-2.5 microM). In female hearts, E4031 (0.5 microM) produced marked prolongations of APDs yet few EADs with no progression to PVT (n = 16/18). Thus, sex differences are opposite in prepubertal versus adult rabbits with respect to E4031-induced APD prolongation, EADs and PVT, underscoring the fact that APD prolongation alone is insufficient to predict arrhythmia susceptibility.

[Calmodulin antagonist inhibits torsade de pointes induced by d-sotalol in an isolated rabbit heart model]

OBJECTIVE

To evaluate the effects of W-7, a calmodulin inhibitor, on transmural dispersion of repolarization (TDR), early after depolarization (EAD) and torsade de pointes (TdP) induction after administration of d-sotalol in isolated rabbit heart.

METHODS

TdP was induced by d-sotalol (30 micromol/L), bradycardia, and hypokalemic (1.5 mmol/L)/hypomagnesaemic (0.35 mmol/L) solution in isolated female rabbit hearts. Thirty six rabbit hearts were divided into 4 groups (n = 9 each): d-sotalol alone, d-sotalol + W-7 (20 micromol/L), d-sotalol + W-7 (50 micromol/L), and d-sotalol + W-7 (100 micromol/L). Monophasic action potentials (MAPs) of the left ventricular epimyocardium (Epi), midmyocardium (M), and endomyocardium (Endo) were recorded simultaneously with ECG. The incidence of EAD and TdP were observed as well.

RESULTS

Treatment with d-sotalol alone prolonged ventricular MAP duration and QT interval, increased TDR, and evoked high incidence of EAD (9/9) and spontaneous TdP (7/9) in hypokalemic/hypomagnesaemic solution in female rabbit heart. W-7 concentration-dependently decreased incidence of TdP (4/9 in 20 micromol/L; 2/9 in 50 micromol/L; 1/9 in 100 micromol/L). This effect of W-7 coincided with the decreased incidence of EAD (5/9 in 20 micromol/L; 4/9 in 50 micromol/L; 1/9 in 100 micromol/L). However, the d-sotalol-induced prolongation of QT interval and TDR was not significantly altered by W-7 at the three concentration used.

CONCLUSIONS

In isolated female rabbit hearts, calmodulin antagonist W-7 suppresses d-sotalol-induced TdP without altering TDR but does suppress EAD. The effects observed with W-7 also suggest a possible important role for calmodulin-activated enzymes in the induction of TdP.

Cellular and ionic mechanism for drug-induced long QT syndrome and effectiveness of verapamil

OBJECTIVES

We examined the cellular and ionic mechanism for QT prolongation and subsequent Torsade de Pointes (TdP) and the effect of verapamil under conditions mimicking KCNQ1 (I(Ks) gene) defect linked to acquired long QT syndrome (LQTS).

BACKGROUND

Agents with an I(Kr)-blocking effect often induce marked QT prolongation in patients with acquired LQTS. Previous reports demonstrated a relationship between subclinical mutations in cardiac K+ channel genes and a risk of drug-induced TdP.

METHODS

Transmembrane action potentials from epicardial (EPI), midmyocardial (M), and endocardial (ENDO) cells were simultaneously recorded, together with a transmural electrocardiogram, at a basic cycle length of 2,000 ms in arterially perfused feline left ventricular preparations.

RESULTS

The I(Kr) block (E-4031: 1 micromol/l) under control conditions (n = 5) prolonged the QT interval but neither increased transmural dispersion of repolarization (TDR) nor induced arrhythmias. However, the I(Kr) blocker under conditions with I(Ks) suppression by chromanol 293B 10 micromol/l mimicking the KCNQ1 defect (n = 10) preferentially prolonged action potential duration (APD) in EPI rather than M or ENDO, thereby dramatically increasing the QT interval and TDR. Spontaneous or epinephrine-induced early afterdepolarizations (EADs) were observed in EPI, and subsequent TdP occurred only under both I(Ks) and I(Kr) suppression. Verapamil (0.1 to 5.0 micromol/l) dose-dependently abbreviated APD in EPI more than in M and ENDO, thereby significantly decreasing the QT interval, TDR, and suppressing EADs and TdP.

CONCLUSIONS

Subclinical I(Ks) dysfunction could be a risk of drug-induced TdP. Verapamil is effective in decreasing the QT interval and TDR and in suppressing EADs, thus preventing TdP in the model of acquired LQTS.

Seltene Ursache einer Prolongierung der QT-Zeit und reanimationspflichtigen Torsade-de-pointes-Tachykardie

A 62 year old patient underwent an intraoperative pancreas biopsy because of a pancreas head process. On 13(th) and 20(th) postoperative day a short syncope episode occurred. On that days calcium blood levels were 1,82 and 1,74 mmol/l, respectively. On 13(th) postoperative day QT(c) interval was 565 ms. On 26(th) postoperative day the patient was resuscitated because of torsade de pointes tachycardia. His actual calcium blood level was 1,47 mmol/l and QT(c) interval 627 ms. An extensive diagnostic work-up revealed no evidence of cardiac disease. After calcium substitution QT interval normalised. During a follow-up period of 16 months the patient remained without symptoms.

A patient with LQTS in whom verapamil administration and permanent pacemaker implantation were useful for preventing torsade de pointes

A 21-year-old woman with long QT syndrome and missense mutation in HERG (T613M), suffered from repeated attacks of pause dependent torsade de pointes, even though she was given beta-blockers and underwent stellate ganglion block twice at the age of eight. After she received permanent pacemaker implantation and administration of verapamil, no premature beats or pause dependent torsade de pointes was observed.

Initiation and monitoring of class III antiarrhythmic agents

Initiation and Monitoring of Class III Agents. Dofetilide is a Class III antiarrhythmic agent that is approved by the United States Food and Drug Administration (FDA) for use in the conversion of atrial fibrillation, as well as in the maintenance of normal sinus rhythm. Because of the risk of torsades de pointes associated with dofetilide, the FDA mandated in-hospital initiation of therapy and initially restricted dofetilide's availability to institutions and prescribers who completed appropriate educational forums. The use of dofetilide within health care systems requires specific procedures for prescribing, dispensing, and monitoring, as well as a format for educating personnel who will be involved in the care of these patients. Several models have demonstrated success in initiating dofetilide and are also used for sotalol, which also can cause torsades de pointes. The utilization of nonphysician personnel, such as nurse practitioners and clinical pharmacists, in conjunction with a team approach were essential components for the success of these models. Preprinted order forms or procedural guidelines, as well as computer-assisted dosing programs, can be utilized to prevent inappropriate or miscalculated dosing of these agents, which potentially can cause life-threatening ventricular arrhythmias.

Drug-induced torsades de pointes and implications for drug development

Torsades de pointes is a potentially lethal arrhythmia that occasionally appears as an adverse effect of pharmacotherapy. Recently developed understanding of the underlying electrophysiology allows better estimation of the drug-induced risks and explains the failures of older approaches through the surface ECG. This article expresses a consensus reached by an independent academic task force on the physiologic understanding of drug-induced repolarization changes, their preclinical and clinical evaluation, and the risk-to-benefit interpretation of drug-induced torsades de pointes. The consensus of the task force includes suggestions on how to evaluate the risk of torsades within drug development programs. Individual sections of the text discuss the techniques and limitations of methods directed at drug-related ion channel phenomena, investigations aimed at action potentials changes, preclinical studies of phenomena seen only in the whole (or nearly whole) heart, and interpretation of human ECGs obtained in clinical studies. The final section of the text discusses drug-induced torsades within the larger evaluation of drug-related risks and benefits.

Evaluation of the dofetilide risk-management program

BACKGROUND

Dose-dependent torsades de pointes has been shown to occur with dofetilide (Tikosyn) and sotalol HCl (Betapace AF); thus, detailed dosing and monitoring recommendations to minimize this risk are included in the product labeling for both drugs. Only dofetilide, however, has a mandated risk-management program that restricts distribution of the drug and requires prescriber education on the drug. We investigated whether this program improved adherence to dosing and monitoring recommendations for dofetilide as compared with sotalol.

METHODS

Charts for 47 patients taking dofetilide and 117 patients taking sotalol were reviewed.

RESULTS

The recommended starting dose was prescribed more frequently in the dofetilide group than in the sotalol group (79% vs 35%, P <.001). A higher number of patients in the dofetilide group compared with the sotalol group received the recommended baseline tests for potassium (100% vs 82%, P <.001), magnesium (89% vs 38%, P <.001), serum creatinine (100% vs 82%, P <.001), and electrocardiography (94% vs 67%, P <.001). A significantly greater proportion of patients in the dofetilide group received recommended electrocardiograms obtained after the first dose (94% for dofetilide vs 43% for sotalol, P <.001) and subsequent doses (80% for dofetilide vs 3.5% for sotalol, P <.001).

CONCLUSION

Better adherence to several dosing and monitoring recommendations in the dofetilide group may be caused by the presence of the risk-management program. However, low usage of dofetilide during the study period may signify an unintended, negative consequence of the risk-management program.

Mortality in patients after a recent myocardial infarction: a randomized, placebo-controlled trial of azimilide using heart rate variability for risk stratification

BACKGROUND

Depressed left ventricular function (LVF) and low heart rate variability (HRV) identify patients at risk of increased mortality after myocardial infarction (MI). Azimilide, a novel class III antiarrhythmic drug, was investigated for its effects on mortality in patients with depressed LVF after recent MI and in a subpopulation of patients with low HRV.

METHODS AND RESULTS

A total of 3717 post-MI patients with depressed LVF were enrolled in this randomized, placebo-controlled, double-blind study of azimilide 100 mg on all-cause mortality. Placebo patients with low HRV had a significantly higher 1-year mortality than those with high HRV (>20 U; 15% versus 9.5%, P<0.0005) despite nearly identical ejection fractions. No significant differences were observed between the 100-mg azimilide and placebo groups for all-cause mortality in either the "at-risk" patients identified by depressed LVF (12% versus 12%) or the subpopulation of "high-risk" patients identified by low HRV (14% versus 15%) or for total cardiac or arrhythmic mortality. Significantly fewer patients receiving azimilide developed atrial fibrillation than did patients receiving placebo (0.5% versus 1.2%, P<0.04). The incidences of torsade de pointes and severe neutropenia (absolute neutrophil count < or =500 cells/microL) were slightly higher in the azimilide group than in the placebo group (0.3% versus 0.1% for torsade de pointes and 0.9% versus 0.2% for severe neutropenia).

CONCLUSIONS

Azimilide did not improve or worsen the mortality of patients after MI. Low HRV independently identified a subpopulation at high risk of mortality.