Profiles of aprindine, cibenzoline, pilsicainide and pirmenol in the framework of the Sicilian Gambit. The Guideline Committee for Clinical Use of Antiarrhythmic Drugs in Japan (Working Group of Arrhythmias of the Japanese Society of Electrocardiology)

Characterization of remodeling processes in the atria of atrioventricular block dogs: Utility as an early-stage atrial fibrillation model

To characterize utility of atrioventricular block (AVB) dogs as atrial fibrillation (AF) model, we studied remodeling processes occurring in their atria in acute (<2 weeks) and chronic (>4 weeks) phases. Fifty beagle dogs were used. Holter electrocardiogram demonstrated that paroxysmal AF occurred immediately after the production of AVB, of which duration tended to be prolonged in chronic phase. Electrophysiological analysis showed that inter-atrial conduction time and duration of burst pacing-induced AF increased in the chronic phase compared with those in the acute phase, but that atrial effective refractory period was hardly altered. Echocardiographic study revealed that diameters of left atrium, right pulmonary vein and inferior vena cava increased similarly in the acute and chronic phases. Histological evaluation indicated that hypertrophy and fibrosis in atrial tissue increased in the chronic phase. Electropharmacological characterization showed that i.v. pilsicainide effectively suppressed burst pacing-induced AF with increasing atrial conduction time and refractoriness of AVB dogs in chronic phase, but that i.v. amiodarone did not exert such electrophysiological effects. Taken together, AVB dogs in chronic phase appear to possess such pathophysiology as developed in the atria of early-stage AF patients, and therefore they can be used to evaluate drug candidates against early-stage AF.

Prognostic benefits of prior amiodarone or β-blocker use before the onset of ventricular arrhythmia with hemodynamic collapse

Although antiarrhythmic drugs have long been used for the suppression of various types of arrhythmias, their prior use before the onset of ventricular arrhythmia with hemodynamic collapse and the effect on prognosis is not well known. Data from 1004 consecutive patients with cardiovascular shock in the Japanese Circulation Society's Shock Registry were analyzed. Eighty-four cases of ventricular arrhythmia-induced shock and ROSC (return of spontaneous circulation) were divided into the prior amiodarone or β-blockers use group (Aβ group, n = 27) and the non-amiodarone and non-β-blockers use group (non-Aβ group; n = 57) based on treatment before the onset of those arrhythmias. Clinical outcomes related to hemodynamic collapse such as OHCA (out-of-hospital cardiovascular arrest) was less in the Aβ group [Aβ group, 11/26 (42%) vs. non-Aβ group, 41/56 (73%); p = 0.007]. Similarly, syncope was less common in the Aβ group than in the non-Aβ group [Aβ group 4/27 (15%) vs. non-Aβ group 27/57 (47%); p = 0.004]. Furthermore, prior amiodarone or β-blockers use before the onset of ventricular arrhythmias was strongly associated with both survival at discharge (odds ratio 3.19; 95% confidence interval 1.06-9.67; p = 0.040) and neurological outcomes at discharge (odds ratio 3.96; 95% confidence interval 1.32-11.85; p = 0.014) based on multivariate logistic regression analysis. Prior amiodarone or β-blockers use before the onset of malignant ventricular arrhythmia and maintaining appropriate blood concentrations in advance is associated with a good survival rate and better neurological outcomes after recovery from ventricular arrhythmia with hemodynamic collapse.

Association between clinical outcome and antiarrhythmic treatment in heart failure patients who have atrial fibrillation upon admission to the hospital

BACKGROUND

Atrial fibrillation (AF) and heart failure (HF) are associated with significant mortality and morbidity. We sometimes encounter patients who have AF upon admission to the hospital, but it spontaneously converts to sinus rhythm within several days (i.e. converter).

PURPOSE

We examined the association between the outcome and types of strategy for AF treatment in converters.

METHODS

From January 2000 to December 2005, we identified 95 converters (age 69 ± 12 years) presenting with worsening HF and AF upon admission, in which sinus rhythm was restored within 7 days without either electrical or pharmacological cardioversion. The patients were classified into three groups according to the antiarrhythmic drug (AAD) therapy used: class I AAD, class III AAD, and rate-control drug. The patients were followed for 36 ± 23 months.

RESULTS

The left ventricular ejection fraction (LVEF) significantly improved with conversion to sinus rhythm (38 ± 14% vs. 47 ± 13%, p<0.05). Those receiving class I AAD had a trend toward a well-preserved LVEF (50 ± 13%, n=35) as compared to those receiving class III AAD (43 ± 12%, n=24) or rate-control drug (47 ± 14%, n=36). In the patients receiving class I AAD, the rate of all-cause death increased 1.9-fold (p=0.009) compared to those receiving class III AAD, and 1.7-fold (p=0.010) compared to those taking rate-control drug. A hospitalization for HF was observed in 49 (52%) patients, however there was no significant difference in the rate of hospitalization among the three groups (p=0.890). Those receiving rate-control drugs had a 50% lower rate of the development of persistent AF than those taking class III AAD (p=0.019).

CONCLUSIONS

A rate-control strategy should be the primary approach for converters to reduce mortality and development of persistent AF.

Comparison of acute reduction in left ventricular outflow tract pressure gradient in obstructive hypertrophic cardiomyopathy by disopyramide versus pilsicainide versus cibenzoline

Negative inotropic agents are often administered to decrease the left ventricular (LV) pressure gradient in patients with obstructive hypertrophic cardiomyopathy (HC). Little information is available regarding comparisons of the effects on LV pressure gradient among negative inotropic agents. The present study compared the decrease in the LV pressure gradient at rest in patients with obstructive HC after treatment with pilsicainide versus treatment with disopyramide or cibenzoline. The LV pressure gradient and LV function were assessed before and after the intravenous administration of each drug. In 12 patients (group A, mean pressure gradient 90 ± 24 mm Hg), the effects of disopyramide, propranolol, and verapamil were compared. In another 12 patients (group B, mean pressure gradient 98 ± 34 mm Hg), a comparison was performed among disopyramide, cibenzoline, and pilsicainide. In group A, the percentage of reduction in the LV pressure gradient was 7.7 ± 9.9% with verapamil, 19.0 ± 20.2% with propranolol, and 58.6 ± 15.0% with disopyramide, suggesting that disopyramide was more effective than either verapamil or propranolol. In group B, the percentage of reduction in the LV pressure gradient was 55.3 ± 26.6% with disopyramide, 55.3 ± 20.6% with cibenzoline, and 54.7 ± 15.4% with pilsicainide, suggesting an equivalent effect on the LV pressure gradient for these 3 agents. In conclusion, these results indicate that the acute efficacy for the reduction of the LV pressure gradient at rest by pilsicainide (a pure sodium channel blocker) was equivalent to that of disopyramide or cibenzoline (combined sodium and calcium channel blockers). Accordingly, sodium channel blockade might be more important for reducing the LV pressure gradient at rest in patients with obstructive HC than calcium channel blockade or β blockade.

Relationship between serum aprindine concentration and neurologic side effects in Japanese

The aim of this study was to evaluate the relationship between the neurologic side effects associated with serum aprindine concentrations and the safety range of aprindine for the prevention of neurologic side effects in 142 Japanese inpatients. Serum aprindine concentrations were determined by high-performance liquid chromatography. A poor positive correlation was observed between dose and serum aprindine concentration (r(2)=0.0419, p=0.0114), and between age and ratio of serum aprindine concentration to the dose per body weight of aprindine (r(2)=0.0159, p=0.121). When aprindine concentration was <1 microg/ml, almost no patients showed neurologic side effects associated with aprindine. On the other hand, about 50% of the patients showed neurologic side effects when aprindine concentrations were >1 microg/ml. Here, the side effects associated with aprindine such as dizziness or intention tremors were observed in 15 patients, which later disappeared after discontinuance of aprindine therapy or a decrease in the dose. In conclusion, serum aprindine concentration should be maintained under approximately 1 microg/ml in Japanese patients to prevent neurologic side effects.

Early termination of spiral wave reentry by combined blockade of Na+ and L-type Ca2+ currents in a perfused two-dimensional epicardial layer of rabbit ventricular myocardium

BACKGROUND

Modification of spiral wave (SW) reentry by antiarrhythmic drugs is a central issue to be challenged for better understanding of their benefits and risks.

OBJECTIVE

We investigated the effects of pilsicainide and/or verapamil, which block sodium and L-type calcium currents (I(Na) and I(Ca,L)), respectively, on SW reentry.

METHODS

A two-dimensional epicardial ventricular muscle layer was created in rabbit hearts by cryoablation (n = 32), and action potential signals were analyzed by high-resolution optical mapping.

RESULTS

During constant stimulation, pilsicainide (3-5 microM) caused a frequency-dependent decrease of conduction velocity (CV; by 20%-54% at 5 Hz) without affecting action potential duration (APD). Verapamil (3 microM) caused APD shortening (by 16% at 5 Hz) without affecting CV. Ventricular tachycardias (VTs) that were induced were more sustained in the presence of either pilsicainide or verapamil. The incidence of sustained VTs (>30 s)/all VTs per heart was 58% +/- 9% for 5 microM pilsicainide vs. 22% +/- 9% for controls and 62% +/- 10% for 3 microM verapamil vs. 22% +/- 8% for controls. The SWs with pilsicainide were characterized by slower rotation around longer functional block lines (FBLs), whereas those with verapamil were characterized by faster rotation around shorter FBLs. Combined application of 3 microM pilsicainide and 3 microM verapamil resulted in early termination of VTs (sustained VTs/all VTs per heart: 2% +/- 2% vs. 29% +/- 9% for controls); SWs showed extensive drift and decremental conduction, leading to their spontaneous annihilation.

CONCLUSION

Blockade of either I(Na) or I(Ca,L) stabilizes SWs in a two-dimensional epicardial layer of rabbit ventricular myocardium to help their persistence, whereas blockade of both currents destabilizes SWs to facilitate their termination.

Pharmacological Cardioversion of Long-Lasting Atrial Fibrillation

Pharmacological therapy for atrial fibrillation (AF) is difficult because AF induces atrial remodeling. Randomized prospective studies using amiodarone could not show the superiority of rhythm control strategy to rate control strategy for treatment of AF. Bepridil is a multichannel blocker like amiodarone and expected to be effective for termination of AF without exacerbation of extracardiac adverse effects. Efficacy and safety of bepridil in pharmacological cardioversion of long-lasting AF (≥3 months) was assessed. To avoid the risk of excessive QT prolongation, bepridil dosage was limited to ≤200 mg/day and aprindine (class Ib) was added if necessary. Bepridil alone or in combination with aprindine restored sinus rhythm in 69% of patients. No adverse effects necessitating drug termination occurred. The average time to conversion after starting bepridil was 30 days and cardioversion was associated with significant increase in fibrillation cycle length. After cardioversion, atrial contraction recovered faster within 1 week and sinus rhythm was maintained better than conventional electrical cardioversion. The history of drug-resistant AF did not affect efficacy of bepridil. These observations suggest that pharmacological cardioversion of long-lasting AF could become a new therapeutic option. Although the precise mechanism of cardioversion by bepridil is not clear, reversal of the remodeled atria may play an important role.

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.

Different Effect of the Pure Na+ Channel-Blocker Pilsicainide on the ST-Segment Response in the Right Precordial Leads in Patients With Normal Left Ventricular Function

BACKGROUND

The response of the ST-segment in the right precordial leads to Na+ channel blockers in patients without structural heart disease and a typical Brugada-type ECG has not been fully elucidated.

METHODS AND RESULTS

A pilsicainide challenge test was performed in 161 patients and according to recently established ECG criteria and an organized computer algorithm, the ST morphology was classified and the maximum increase in the J wave amplitude (maxDeltaJ) from the standard and high right precordial leads V1-3 was examined. Before the test, subjects exhibiting type 1 ECG in the standard leads were excluded. After administering pilsicainide, type 1 ECGs in the standard leads were observed in 31 cases and a maxDeltaJ of >or=200 microV was observed in 29 cases (23 type 1, 2 type 2/3 and 4 normal ECGs). In the additional higher right precordial leads, type 1 ECGs were observed in 55 cases and a maxDeltaJ of >or=200 microV was observed in 45 cases (42 type 1 and 3 type 2/3 ECGs).

CONCLUSIONS

A maxDeltaJ>or=200 microV induced by pilsicainide, including that measured in the high right precordial leads, was associated with a change mainly to a type 1 ECG.

T wave alternans in an in vitro canine tissue model of Brugada syndrome

Macroscopic T wave alternans (TWA) associated with increased occurrence of ventricular arrhythmias has been reported in patients with Brugada syndrome. However, the mechanisms in this syndrome are still unclear. We evaluated the hypothesis that TWA in Brugada syndrome was caused by the dynamic instability and heterogeneity of action potentials (APs) in the right ventricle. Using an optical mapping system, we mapped APs on the epicardium or transmural surfaces of 28 isolated and arterially perfused canine right ventricular preparations having drug-induced Brugada syndrome (in micromol/l: 2.5-15 pinacidil, 5.0 terfenadine, and 5.0-13 pilsicainide). Bradycardia at cycle length (CL) of 2,632 +/- 496 ms (n = 19) induced alternating deep and shallow T waves in the transmural electrocardiogram. Compared with the shallow T waves, deep T waves were associated with epicardial APs having longer durations and larger domes. Adjacent regions having APs with alternating domes, with constant domes, and without domes coexisted simultaneously in the epicardium and caused TWA. In contrast to the alternating epicardial APs, midmyocardial and endocardial APs did not change during TWA. Alternans could be terminated by rapid (CL: 529 +/- 168 ms, n = 7) or very slow (CL: 3,000 ms, n = 7) pacing. The heterogeneic APs during TWA augmented the dispersion of repolarization both within the epicardium and from the epicardium to the endocardium and caused phase 2 reentry. In this drug-induced model of Brugada syndrome, heterogeneic AP contours and dynamic alternans in the dome of right ventricular epicardial, but not midmyocardial or endocardial, APs caused TWA and heightened arrhythmogenicity in part by increasing the dispersion of repolarization.

Multicenter survey on the validity of the CD-ROM guideline for antiarrhythmic drug therapy produced by the Japanese Circulation Society and the Japanese Society on Electrocardiology: preliminary report of the survey of the Japanese guideline for Arrhythmia Management By Individual Therapy (J-GAMBIT)

BACKGROUND

A multicenter investigational survey (Japanese Guideline for Arrhythmia Management By Individual Therapy) was conducted to evaluate the validity of using CD-ROM guidelines vs physician choice for the selection of antiarrhythmic drugs.

METHODS AND RESULTS

Patients with paroxysmal atrial fibrillation (PAF, n=274) or premature ventricular contractions (PVC, n=216) were enrolled. The rate of concordance for drug selection between the treating physician and the CD-ROM was 216 of 274 patients (78.8%) with PAF. Of these, 168 (61.3%) were concordant for first-line agents and the remaining 48 (17.5%) were concordant for second-line agents. The concordance for the treatment of PVC was 154/216 cases (71.3%). Of these, 106 (49.1%) were concordant for first-line agents and the remaining 48 (22.2%) were concordant for second-line agents. Nonconcordance for PAF therapy was more likely to occur for patients with underlying heart disease (p<0.05), depressed cardiac function (p<0.001), and with more frequent ECG abnormalities and renal dysfunction. These differences were not seen in patients with PVC.

CONCLUSION

The CD-ROM guidelines appear to be valid in the selection of antiarrhythmic drugs for both PAF and PVC, but their usefulness is influenced by the patient's clinical characteristics.

Topics on the Na+/Ca2+ Exchanger: Pharmacological Characterization of Na+/Ca2+ Exchanger Inhibitors

Using the whole-cell voltage clamp, we examined acute effects of various agents on Na(+)/Ca(2+) exchange current (I(NCX)) in guinea-pig cardiac ventricular cells and transfected cells. Among the antiarrhythmic drugs, amiodarone, bepridil, dronedarone, cibenzoline, azimilide, and aprindine inhibited I(NCX) in a concentration-dependent manner. We also investigated the effects on NCX of 2,3-buanedione monoxim (BDM) and selective NCX inhibitors such as KB-R7943, SEA0400, and SN-6. The presence of trypsin in the pipette solution attenuated the inhibitory effects on NCX of amiodarone, bepridil, and BDM, suggesting that these drugs inhibit NCX from the cytosolic side. In contrast, the trypsin-insensitive NCX inhibitors were aprindine, azimilide, dronedarone, cibenzoline, KB-R7943, SEA0400, and SN-6. KB-R7943, SEA0400, and SN-6 suppressed the uni-directional outward I(NCX) more potently than the uni-directional inward I(NCX). The mechanism of this mode-dependency is unknown, but is suggested to be related to intracellular Na(+) concentration.

Pharmacological Conversion of Persistent Atrial Fibrillation Into Sinus Rhythm With Oral Pilsicainide

BACKGROUND

The present study was conducted to determine the antiarrhythmic efficacy and safety of oral pilsicainide, a class Ic antiarrhythmic drug, in patients with persistent atrial fibrillation (AF).

METHODS AND RESULTS

One hundred and eight patients (mean age, 58.9 years) with AF lasting >or=48 h and <or=6 months were randomized to receive pilsicainide 50 mg t.i.d. (n=58) or placebo (n=50) for 2 weeks in a double-blinded fashion. All patients underwent appropriate anticoagulation therapy with warfarin for >or=3 weeks prior to the study enrolment or after verification of the absence of left atrial thrombi by transesophageal echocardiography. After 2 weeks of treatment, an electrocardiogram was recorded to determine whether sinus rhythm was restored. Sinus rhythm was restored in 22.4% of patients treated with pilsicainide and in 2% treated with placebo (p=0.002). Cardioversion was less likely to occur with oral pilsicainide when the AF duration exceeded 2 months or if the left atrial diameter exceeded 45 mm. There was no significant difference in the adverse cardiovascular event rate between the pilsicainide- and placebo-treated groups. One patient in the pilsicainide group developed an atrial flutter without any hemodynamic deterioration.

CONCLUSION

A 2-week oral administration of pilsicainide is well tolerated and moderately effective in converting persistent AF into sinus rhythm.

Heart Rate Variability Is a Useful Parameter for Evaluation of Anticholinergic Effect Associated with Inducibility of Atrial Fibrillation

BACKGROUND

Disopyramide is thought to have an advantageous effect for atrial fibrillation (AF) associated with vagal activity because of its anticholinergic effect.

METHOD

We used a canine vagal nerve stimulation (VNS) model. The monophasic action potential (MAP) duration at 90% repolarization (MAP(90)), the intraatrial conduction time, the induciblity of AF by electrical stimulation, and the amplitude of high-frequency component (HF-amp) of the heart rate variability (HRV) were evaluated before and after the administration of disopyramide (1 mg/kg) (group D, n = 8) or pilsicainide (1 mg/kg) (group P, n = 5).

RESULTS

In group D, HF-amp decreased in the baseline condition from 1.1 +/- 0.6 to 0.6 +/- 0.4 ms and the degree of VNS-induced augmentation of HF-amp was attenuated from +492% to +127%. VNS-induced shortening of MAP(90) was also attenuated in the right atrium (from -30 +/- 15% to -10 +/- 6%) and in the left atrium (from -15 +/- 9% to -6 +/- 6%). In group P, little effect was shown in these parameters. The vagotonic AF became noninducible in all eight experiments in group D, while in only one of five in group P.

CONCLUSION

The beneficial effect of disopyramide for vagotonic AF is based on the decrease of basal vagal tone and attenuation of the effect of vagal stimulation in the atrial myocardium. HRV is a useful parameter for evaluation of the effect of antiarrhythmic drugs on the autonomic nerve system, and the evaluation of variability may be useful for testing drug efficacy for arrhythmias.

Optical imaging of spiral waves: pharmacological modification of spiral-type excitations in a 2-dimensional layer of ventricular myocardium

Differential effects of sodium channel blockers, an I(Kr) blocker (nifekalant) and amiodarone on the spiral-type reentry, were investigated in rabbit hearts by using a high-resolution optical mapping system. Two-dimensional subepicardial layer of left ventricular myocardium with uniform anisotropy was prepared by endocardial cryoablation. During ventricular tachycardia (VT) elicited by cross-field stimulation, spiral-type excitations rotating around functional block lines (FBLs) were visualized. All the sodium channel blockers stabilized rotors; VT duration was prolonged in association with increases of FBLs and VT cycle length. The rotors in the presence of nifekalant were characterized by large meandering, long FBLs, and frequent front-tail interactions generating wave breaks. Amiodarone (acute application) increased FBLs and VT cycle length, but shortened the VT duration with minimal front-tail interaction. These results suggest that multifaceted drug action on both depolarization and repolarization may be required for the early termination of spiral-type reentry without causing breakup of rotors.

Drug-induced changes in fibrillation cycle length and organization index can predict chemical cardioversion of long-lasting atrial fibrillation with bepridil alone or in combination with aprindine

BACKGROUND

The aim of this study was to investigate whether drug-induced changes in fibrillation wave characteristics can predict pharmacological conversion of long lasting persistent atrial fibrillation (AF).

METHODS AND RESULTS

The study group comprised 23 consecutive patients with AF lasting > or =1 month. Patients first received bepridil (200 mg/day) for 2-4 weeks. When sinus rhythm was not restored with bepridil, oral aprindine (40 or 60 mg/day) was added to bepridil. Fast Fourier transform analysis of fibrillation waves using lead V1 was performed to calculate the fibrillation cycle length (FCL). The spectral areas were measured and the maximum area divided by the total area was termed the fibrillation organization index (FOI). Sinus rhythm was restored in 16 of 23 patients (70%); 8 of these 16 patients received only bepridil (Group I) and the other 8 responders received bepridil and aprindine (Group II). In Group I bepridil increased both FCL (p<0.001) and FOI (p<0.01) and terminated AF after 20+/-12 days. In Group II bepridil increased FCL (p<0.001), but did not change FOI. The addition of aprindine terminated AF in association with an increase in both FCL (p<0.005) and FOI (p<0.005) within 19+/-8 days. In the remaining 7 patients who did not have restoration of sinus rhythm, bepridil increased both FCL and FOI significantly, but less than in Group I, and the addition of aprindine did not further increase either of them. Chemical cardioversion of AF occurred in all patients with FCL > or =190 ms and FOI > or =45% after drug administration.

CONCLUSION

Bepridil alone or in combination with aprindine converted long lasting persistent AF in association with an increase in both FCL and FOI. The combination of FCL and FOI after drug administration is helpful in predicting chemical cardioversion of persistent AF.

Oral cibenzoline reduces postoperative atrial fibrillation in coronary artery bypass grafting

OBJECTIVE

The objective of the present study was to investigate the effectiveness of postoperative oral administration of cibenzoline for the prevention of atrial fibrillation (AF) in coronary artery bypass grafting (CABG).

METHODS

A total of 39 patients who underwent isolated CABG from September 2000 to February 2001 and who took oral cibenzoline (300 mg per day for 10 days beginning immediately after surgery) were compared to 59 patients who underwent surgery in our department 8 months prior to the study and who did not take cibenzoline for incidence of postoperative AF. Exclusion criteria encompassed age (>80 years), low ejection fraction (<30%), high serum creatinine level (>2.0 mg/dL), and history of supraventricular arrhythmia with or without treatment by anti-arrhythmic drugs.

RESULTS

Postoperative AF occurred in 2 patients in the cibenzoline group (2/35, 5.7%) and 20 patients in the control group (20/59, 33.9%). There were significant differences in the incidence of postoperative AF (p = 0.002). Multivariate analysis revealed that the administration of cibenzoline reduced the incidence of AF significantly, and that a large number of bypass grafts significantly contributed to postoperative AF in CABG. The number of bypass grafts was significantly larger in the cibenzoline group, indicating that cibenzoline administration significantly suppresses the incidence of AF after CABG in high-risk patients.

CONCLUSIONS

Postoperative administration of oral cibenzoline for 10 days is one effective method for the prevention of AF after CABG.

Maintenance of Sinus Rhythm and Recovery of Atrial Mechanical Function After Cardioversion With Bepridil or in Combination With Aprindine in Long-Lasting Persistent Atrial Fibrillation

BACKGROUND

The aim of this study was to evaluate pharmacological cardioversion of long-lasting persistent atrial fibrillation (AF) using bepridil in terms of recovery of atrial mechanical function and maintenance of sinus rhythm. Bepridil alone or in combination with aprindine is effective for termination of persistent AF.

METHODS AND RESULTS

The study group comprised 38 consecutive patients (24 men, 58.8+/-9.3 years) with successful conversion of persistent AF lasting >1 month either pharmacologically (Group I) or electrically (Group II). Fast Fourier transform analysis of fibrillation waves was performed and fibrillation cycle length (FCL) was calculated from the peak frequency. In Group I, sinus rhythm was pharmacologically restored in 22 patients after an average 30 days (7-49 days) of bepridil administration, either alone (11) or in combination with oral aprindine (11); they were followed up while using the same drugs. In Group II, electrical conversion restored sinus rhythm in 16 patients, and they were followed up with conventional antiarrhythmic drugs other than bepridil and aprindine. After bepridil treatment FCL increased and became significantly longer in Group I than in Group II (190+/-39 vs 150+/-29 ms, p<0.001). Atrial peak velocity in transmitral flow within the first week after cardioversion was greater in Group I than in Group II (68+/-35 vs 32+/-20 cm/s, p<0.05). By Kaplan-Meier analysis, 83% of Group I patients were free of AF recurrence at the 12-month follow-up, compared with 36% in Group II (p<0.005).

CONCLUSIONS

In patients with long-lasting AF, pharmacological conversion with bepridil alone or in combination with aprindine recovered atrial mechanical function better and maintained sinus rhythm longer than electrical conversion.

Effects of Na+ channel blocker, pilsicainide, on HERG current expressed in HEK-293 cells

PURPOSE

Pilsicainide, classified as a relatively pure Na+ channel blocker, occasionally causes QT prolongation, suggesting inhibitory actions on K+ currents. We studied effects of pilsicainide on the K+ channel current of the human ether-a-go-go-related gene (HERG) in heterologous expression system.

METHODS

The Patch-clamp technique in whole-cell configuration was used to record the channel current of HERG stably expressed in HEK293 cells.

RESULTS

Pilsicainide suppressed peak currents of HERG channel during depolarizing pulses and tail currents upon repolarization. Pilsicainide blocked HERG current with IC50 = 20.4 microM and Hill coefficient = 0.98. Voltage-dependent activation was shifted in a negative direction by approximately 10 mV by 10 to 20 microM pilsicainide. Block increased with depolarization to voltages between -20 and 0 mV and reached the maximum level at positive voltages to 0 mV without further increase. Following drug equilibration for 10 minutes (holding potential at -100 mV), the peak outward current upon the first depolarization showed time-dependent block; tail current block was maximal. Frequency-dependent block evaluated from tail current was absent with pulse frequencies of 1.33, 0.5, and 0.2 Hz. After a steady state block was achieved, time course of current activation and deactivation was slowed by pilsicainide, and steady-state inactivation and time course of fast inactivation were mildly affected.

CONCLUSIONS

Pilsicainide blocks HERG current with a preferential affinity, at least, to the open state of the channels with a fast access to binding sites.

Intravenous administration of class I antiarrhythmic drug induced T wave alternans in an asymptomatic Brugada syndrome patient

A 53-year-old man with an abnormal ECG was referred to the Nihon University School of Medicine. The 12-lead ECG showed right bundle branch block and saddleback-type ST elevation in leads V1-V3 (Brugada-type ECG). Signal-averaged ECG showed positive late potentials. Double ventricular extrastimuli (S1: 500 ms, S2: 250 ms, S3: 210 ms) induced VF. Amiodarone (200 mg/day) was administered for 6 months and programmed ventricular stimulation was repeated. VF was induced again by double ventricular stimuli (S1: 600 ms, S2: 240 ms, S3: 170 ms). Intravenous administration of class Ic antiarrhythmic drug, pilsicainide (1 mg/kg), augmented ST-T elevation in leads V1-V3, and visible ST-T alternans that was enhanced by atrial pacing was observed in leads V2 and V3. Visible ST-T wave alternans disappeared in 15 minutes. However, microvolt T wave alternans was present during atrial pacing at a rate of 70/min without visible ST-T alternans.

Usefulness and safety of bepridil in converting persistent atrial fibrillation to sinus rhythm

The aim of this study was to investigate the efficacy and safety of bepridil (a multichannel blocker including several potassium channels) for conversion of long-lasting atrial fibrillation (AF). Bepridil restored sinus rhythm alone or in combination with aprindine in 69% of 32 patients with persistent AF lasting > or = 3 months. The time to conversion after starting bepridil was 30 +/- 12 days. An increase in fibrillation cycle length with bepridil was greater in responders (31 +/- 10%), but an increase in QTc did not differ between responders and nonresponders. Bepridil is effective and safe for terminating long-lasting persistent AF.

Therapeutic monitoring of class I antiarrhythmic agents using high-resolution electrocardiography instead of blood samples

Antiarrhythmic therapy requires monitoring of serum drug concentrations to determine a patient's optimal oral dose of medication. Repeated examination of blood samples, however, is costly and time-consuming, so the present study evaluated whether changes in serum concentrations could be estimated from changes in electrocardiographic (ECG) parameters. Of 36 patients receiving antiarrhythmic drugs for supraventricular or ventricular arrhythmias, 12 were treated with flecainide, 12 with pilsicainide, and 12 with pirmenol. Signal-averaged ECG (SAECG) were recorded before starting drug administration, 1 month later, and twice during ongoing therapy. At the time of the 2nd to the 4th recordings, serum concentrations of the drugs were also measured. As previously reported, all agents, but especially flecainide and pilsicainide, prolonged the filtered QRS (f-QRS) and the duration of low-amplitude signals at the terminal portion of the QRS complex. The SAECG parameters varied between the recordings made during therapy. Differences in the duration of the f-QRS between 2 recordings correlated significantly with differences in serum drug concentrations (r=0.91 for flecainide, r=0.70 for pilsicainide, and r=0.61 for pirmenol). No significant correlation between drug concentration and other SAECG parameters was found. Changes in the serum concentration of flecainide, pilsicainide and pirmenol can be estimated from changes in the duration of the f-QRS on the SAECG and periodic monitoring of such could help reduce the number of repeat measurements of drug concentrations in blood samples.

Widening of the excitable gap and enlargement of the core of reentry during atrial fibrillation with a pure sodium channel blocker in canine atria

BACKGROUND

This study aimed to assess the effects of pilsicainide, a pure sodium channel blocker, on electrophysiological action and wavefront dynamics during atrial fibrillation (AF).

METHODS AND RESULTS

In a newly developed model of isolated, perfused, and superfused canine atria (n=12), the right and left endocardia were mapped simultaneously by use of a computerized mapping system. AF was induced with 1 to 5 micromol/L acetylcholine. The antifibrillatory actions of pilsicainide on AF cycle length (AFCL), refractory period (RP), conduction velocity (CV), excitable gap (EG), and the core of the mother rotor were studied. The RP was defined as the shortest coupling interval that could capture the fibrillating atrium. The EG was estimated as the difference between the AFCL and RP. At baseline, multiple wavefronts were observed. After 2.5 microg/mL infusion of pilsicainide, all preparations showed irregular activity, and AF was terminated in 2 preparations. The AFCL and RP were prolonged, and CV was decreased significantly. The EG was widened (147%; P<0.01), and the core perimeter was increased (100%; P<0.01). Increasing the dosage either terminated AF (6 preparations) or converted to organized activity (ie, atypical atrial flutter) (4 preparations). On the maps, all "unorganized" AFs were terminated with the excitation of the core of the mother rotor by an outside wavefront, whereas in preparations with atrial flutter, pilsicainide did not terminate its activity.

CONCLUSIONS

Widening of the EG by pilsicainide facilitates the excitation of the core of the mother rotor, leading to the termination of AF. In some experiments, pilsicainide converts AF to persistent atrial flutter.

Bepridil prevents paroxysmal atrial fibrillation by a class III antiarrhythmic drug effect

BACKGROUND

[corrected] Bepridil, a multiple ion-channel blocker, has been reported to prevent paroxysmal atrial fibrillation (PAF). The f-f interval of PAF during treatment with bepridil versus class Ic antiarrhythmic drugs was compared.

METHODS

Fifty-two patients with PAF were randomized to bepridil, 200 mg/day (n = 14) versus flecainide, 100 to 200 mg/day (n = 15) or pilsicainide, 75 to 150 mg/day (n = 23). The drug was considered effective when symptomatic episodes of PAF were decreased to < 50% during a follow-up of 2 to 6 months. The f-f interval was measured in 12-lead ECGs of initial PAF episodes.

RESULTS

Bepridil and Ic were effective in 10 of 14 (71.4%) and 24 of 38 patients (63.2%), respectively (ns). In the Ic group, the f-f interval was longer in successfully (114 +/- 48 ms) than in unsuccessfully (68 +/- 25 ms) treated patients (P = 0.002). In the bepridil group, the f-f interval was shorter in successfully (84 +/- 27 ms) than unsuccessfully (155 +/- 68 ms) treated patients (P = 0.015). When comparing unsuccessfully treated patients, the f-f interval in the bepridil group was significantly longer than in the Ic group (P = 0.007).

CONCLUSIONS

Bepridil was as effective as Ic drugs in the prevention of PAF. Because it was more effective in smaller (functional) than larger (anatomical) reentrant circuits, the effect of bepridil was considered to be mainly attributable to a class III antiarrhythmic action.

Evaluation of the effect of bepridil on paroxysmal atrial fibrillation: relationship between efficacy and the f-f interval in surface ECG recordings

Bepridil, a multi-ion channel blocker, is effective for some types of cardiac arrhythmias, and so its effect on the paroxysmal atrial fibrillation (PAF) was evaluated in the present study, comparing it with class Ic antiarrhythmic drugs. The relationship between efficacy and the f-f interval in the surface ECG recording was also analyzed. Sixty-one symptomatic PAF patients were randomized to a bepridil group (200 mg/day, n=23) or class Ic drug group (flecainide 100-200 mg/day or pilsicainide 75-150 mg/day, n=38). The drug was considered effective for PAF prevention when symptomatic episodes of PAF were decreased to less than 50% during the follow-up period of 2-6 months. The f-f interval in the surface 12-lead ECG trace was evaluated during a PAF episode. Both bepridil and the class Ic drugs were effectively prevented PAF (15/23 (65.2%) vs 24/38 (63.1%) patients, NS). In the class Ic drug group, the f-f interval was longer in the effective cases (114+/-48 ms) than in the non-effective cases (68+/-26 ms, p=0.0002). In contrast, in the bepridil group the f-f interval was shorter in the effective cases (85+/-26 ms) than in the non-effective ones (152+/-45 ms, p=0.0005). When comparing the non-effective cases in the 2 groups, the bepridil group showed a significantly longer f-f interval than the class Ic drug group (p=0.0003). As a result of drug administration, the class Ic drugs prolonged the f-f interval from 78+/-33 ms to 128+/-46 ms (p=0.0004) whereas bepridil showed no change (109+/-39 ms vs 135+/-47 ms). For clinical PAF prevention, the effect of bepridil matched that of class Ic antiarrhythmic drugs. Because bepridil was effective in PAF patients with relatively shorter f-f intervals without prolonging the f-f interval, bepridil is considered to work mainly as a class III antiarrhythmic drug.

Inhibitory effect of aprindine on Na+/Ca2+ exchange current in guinea-pig cardiac ventricular myocytes

1. Using the whole-cell voltage clamp technique, the effect of aprindine on Na+/Ca2+ exchange current (I(NCX)) was examined in guinea-pig single cardiac ventricular myocytes and CCL39 fibroblasts expressing a dog cardiac Na+/Ca2+ exchanger (NCX1). 2. I(NCX) was recorded by ramp pulses from the holding potential of -60 mV with the external solution containing 140 mM Na+ and 1 mM Ca2+, and the pipette solution containing 20 mM Na+, 20 mM BAPTA and 13 mM Ca2+ (433 nM free Ca2+). 3. External application of aprindine suppressed I(NCX) in a concentration-dependent manner. The IC50 values of outward (measured at 50 mV) and inward (measured at -100 mV) I(NCX) components were 48.8 and 51.8 microM with Hill coefficients of 1.3 and 1, respectively. 4. Intracellular application of trypsin via the pipette solution did not change the blocking effect of aprindine, suggesting that aprindine does not affect the exchanger from the cytoplasmic side. 5. Aprindine inhibited I(NCX) of a mutant NCX1 with a deletion of amino acids 247 - 671 in the large intracellular domain between the transmembrane segments 5 and 6 in a similar manner to that of the wild-type, suggesting that the site of aprindine inhibition is not in the large intracellular domain of NCX1. 6. A kinetic study indicated that aprindine was cooperatively competitive with KB-R7943, another inhibitor of NCX and that aprindine was a competitive inhibitor with respect to external Ca2+. 7. We conclude that aprindine may modestly inhibit I(NCX) in a therapeutic range of concentrations (around 2.5 approximately 6.9 microM) possibly at an external or intra-membranous site of the exchanger.

Multicenter prospective nonrandomized study of long-term antiarrhythmic drug therapy in patients with tachyarrhythmias: Japanese Antiarrhythmics Long-Term Study-2 (JALT-2 Study)

Based on the results of the Cardiac Arrhythmia Suppression Trial (CAST), strategies for the treatment of tachyarrhythmias have changed rapidly. The Japanese Antiarrhythmics Long-Term (JALT) study was planned to investigate the present methods for choosing antiarrhythmic drugs, and the effects on long-term prognosis in patients with tachyarrhythmias in Japan. Following a 6-month preliminary study (JALT-1), there was a multicenter nonrandomized prospective study (JALT-2), with a 2-year follow-up, of patients with paroxysmal atrial fibrillation (PAF), sustained ventricular tachycardia (SVT) and nonsustained VT (NSVT). Four hundred fifty-five patients were registered, and 361 of them (79%) were analyzed. Cerebral infarction occurred in 10 of 193 patients (5.2%) with PAF. Transition to chronic AF was observed in 21 patients (10.9%), but in none of the patients receiving Ca antagonist therapy. Twenty-five patients died: 5 deaths were arrhythmic, 10 were because of pump failure, and 9 were noncardiac. The most significant difference in drug selection between JALT-1 and JALT-2 was the increase in the use of slow kinetic Na channel blockers for PAF and the decrease in the use of the same agents for VT in the JALT-2 study. A marked change of therapeutic strategy occurred in JALT-2 compared with JALT-1. Most patients with a poor prognosis had underlying heart diseases and heart failure, but the per annum rate of death by arrhythmia and pump failure in JALT-2 was less than that in JALT-1.

Comparative actions of cibenzoline and disopyramide on I(Kr) and I(Ks) currents in rat sino-atrial nodal cells

Modulation by class Ia antiarrhythmic drugs, cibenzoline and disopyramide, of the pacemaking activity and the underlying ionic currents in rat sino-atrial nodal cells was investigated using current-clamp and whole-cell patch-clamp techniques. Both drugs depressed the spontaneous activity and often caused sinus arrest. The negative chronotropic effect was significant at 10 microM cibenzoline and 30 microM disopyramide. The L-type Ca(2+) current (I(Ca)) and the hyperpolarization-activated inward current decreased by 69.7+/-3.2% and by 45.8+/-3.0% at 30 microM cibenzoline and by 51. 2+/-3.3% and by 48.3+/-2.7% at 100 microM disopyramide, respectively. The delayed rectifier K(+) current, which is composed of rapidly and slowly activated currents (I(Kr) and I(Ks)), also decreased. The IC(50) values of I(Kr) for cibenzoline and disopyramide were 8.8+/-1. 1 and 25.1+/-2.3 microM, respectively. In the presence of 5 microM E-4031 (1-[2-(6-methyl-2-pyridyl)ethyl]-4-(4-methylsulfonylaminobenzoyl) piperidine), the IC(50) values of I(Ks) for cibenzoline and disopyramide were 12.3+/-1.8 and 81.1+/-2.3 microM, respectively. The I(Ks) was completely blocked by 30 microM 293B (trans-6-cyano-4-(N-ethylsulphonyl-N-methtamino)-3-hydroxy-2 , 2-dimethyl-chromane). These results indicate that the ionic currents are more sensitive to cibenzoline than disopyramide in rat sino-atrial nodal cells, and that I(Ca) and I(Kr) make major contributions to pacemaking activity.

Negative chronotropic and inotropic effects of class I antiarrhythmic drugs assessed in isolated canine blood-perfused sinoatrial node and papillary muscle preparations

The present study was designed to assess the negative chronotropic and inotropic effects of 10 class I antiarrhythmic drugs, using isolated canine blood-perfused sinoatrial node and papillary muscle preparations. Each drug showed negative chronotropic and inotropic effects in a dose-related manner. The potency of the suppressive effect on the sinoatrial automaticity was in the order of aprindine, quinidine, flecainide, lidocaine, mexiletine, cibenzoline, disopyramide, procainamide, tocainide, and phenytoin, while the effect on the ventricular contraction was in the order of aprindine, flecainide, cibenzoline, lidocaine, mexiletine, disopyramide, tocainide, phenytoin, quinidine, and procainamide. The differences in the suppressive effects could not necessarily be explained by their subclassification, based either on action potential duration or kinetic properties of dissociation or association with sodium channels. On the other hand, we found a good correlation between the negative inotropic effects of class I drugs in this study and the canine antiarrhythmic plasma concentrations for the digitalis- and coronary ligation-induced ventricular arrhythmia models in our previous studies. However, the negative chronotropic effects of the drugs showed a poor correlation with the antiarrhythmic plasma drug concentrations. The data shown in this paper may provide a convenient guideline for predicting acute cardiosuppressive effects of antiarrhythmic drugs, especially in patients with reduced cardiac function.