Procainamide-induced lupus erythematosus-like syndrome in relation to acetylator phenotype and plasma levels of procainamide

To investigate the relationship between acetylator phenotype and the development of procainamide (PA)-induced systemic lupus erythematosus (SLE-like syndrome, 28 patients with chronic ventricular arrhythmias treated with PA were followed for one year. The therapy was guided by plasma monitoring in all patients in order to obtain the proposed therapeutic plasma level of PA. Nine patients (30%), both slow and rapid acetylators, developed the SLE-like syndrome within one year. PA plasma levels were similar in both slow and rapid acetylators and there was no difference in total dose or duration of therapy before development of the syndrome. Thus, the acetylator phenotype is probably of no or minor predictive importance when PA therapy is guided by plasma monitoring. On the other hand, the antinuclear antibodies appeared significantly more rapidly in patients developing the syndrome and could possible be used as an indicator of the risk. The results support the hypothesis that the primary amino group structure of PA may be of importance in the induction of the SLE-like syndrome.

Massive doses of procainamide for ventricular tachyarrhythmias due to myocardial infarction

Three patients are described in whom malignant ventricular arrhythmias appeared in connection with a reinfarction some days after hospitalization for an acute myocardial infarction and in whom massive doses of procainamide, up to 7.5 g/day i.v., were necessary to prevent these arrhythmias. The serum concentration of procainamide was 2--4 times higher than the recommended upper level, but no side-effects were observed. With the dose given, one would have expected still higher serum concentrations. Several reasons for this finding are discussed, including the effects of renal function, intestinal leakage, storage of the drug in tissues and hitherto unknown metabolic pathways of procainamide in patients, who are slow acetylators.

Propafenone versus procainamide for conversion of atrial fibrillation to sinus rhythm

BACKGROUND AND HYPOTHESIS

Antiarrhythmic drugs are widely used for treatment of atrial fibrillation (AF) and restoration of sinus rhythm. This prospective, randomized, and controlled study compared the efficiency and safety of propafenone versus procainamide for the treatment of acute AF.

METHODS

In all, 117 patients (55 women, 62 men, mean age 64.2 +/- 13 years, median 63 years) who presented with AF were included in the study. Exclusion criteria were signs or symptoms of heart failure on physical examination, recent myocardial infarction or cardiac surgery, cardiogenic shock, or hypotension. Forty-one patients spontaneously recovered sinus rhythm; the remaining 76 patients were randomized to receive propafenone or procainamide. Propafenone was given at a dose of 2 mg/kg body weight intravenously (i.v.) over 30 min. Patients randomized to receive procainamide received a bolus of 100 mg i.v. administered every 5 min up to a maximum dose of 1 g. The clinical characteristics of the two groups were comparable.

RESULTS

The number of patients who recovered sinus rhythm after the treatment was larger in the procainamide-treated group (Group 1) (69.5%) than in the propafenone-treated group (Group 2) (48.7%); p < 0.05. The time required for cardioversion was significantly lower in Group 1 (mean 4.1 +/- 1.3 h), than in Group 2 patients (mean 7.3 +/- 2.6 h) (p < 0.01).

CONCLUSION

In the present study, procainamide was more effective than propafenone for the treatment of AF of short duration.

Electropharmacologic effect of a standard dose of intravenous procainamide in patients with sustained ventricular tachycardia

BACKGROUND

Patients with inducible sustained ventricular tachycardia (VT) sometimes receive intravenous procainamide during electrophysiologic testing. Unfortunately, the responses to intravenous and subsequent oral drug therapy are variable and may be discordant.

HYPOTHESIS

It was the aim of this study to determine whether this variability might be explained by heterogeneity in the electropharmacologic response, even in a homogeneous population.

METHODS

We studied 42 patients who had spontaneous malignant ventricular arrhythmia and were inducible to sustained monomorphous VT during electrophysiologic testing. Each received 15 mg/kg of intravenous procainamide followed by a 2 mg/min infusion. Serum levels were drawn immediately following programmed stimulation. The mean procainamide level was 6.7 +/- 1.4 mcg/ml with an N-acetyl procainamide level of 1.0 +/- 0.5 mcg/ml. The 14 procainamide responders (5 of whom were noninducible and 9 whose VT cycle length increased > 100 ms) and the 28 nonresponders had similar procainamide and NAPA levels (6.5 +/- 1.4 vs. 6.7 +/- 1.4 mcg/ml).

RESULTS

There was no significant difference in baseline clinical parameters, His to ventricular electrogram (HV) interval, effective refractory period, or VT cycle length. Prolongation of the effective refractory period and infra His conduction time occurred to a similar extent in responders and nonresponders.

CONCLUSION

We conclude that procainamide has a consistent dose-response relationship with respect to refractoriness and conduction in patients with malignant arrhythmias. However, acute antiarrhythmic efficacy of procainamide cannot be predicted by clinical factors, drug levels, or drug-induced changes in common electrophysiologic parameters.

Emergency department use of intravenous procainamide for patients with acute atrial fibrillation or flutter

OBJECTIVES

Acute atrial fibrillation and flutter are very common arrhythmias seen in emergency department (ED) patients, but there is no consensus for their optimal management. The objective of this study was to examine the efficacy and safety of intravenous (IV) procainamide for acute atrial fibrillation or flutter.

METHODS

This health records review included a consecutive cohort of ED patients with acute-onset atrial fibrillation or atrial flutter who received IV procainamide at one university hospital ED during a five-year period. The standard clinical protocol involved IV infusion of 1 g of procainamide over 60 minutes, followed by electrical cardioversion if necessary. A trained observer extracted data from the original clinical records. Outcome measurements included conversion to sinus rhythm, adverse events, and relapse up to seven days.

RESULTS

The 341 study patients had a mean age of 63.9 years (SD +/- 15.5 years), and 56.6% were male. The conversion rates were 52.2% (95% confidence interval = 47% to 58%) for 316 atrial fibrillation cases and 28.0% (95% confidence interval = 13% to 46%) for 25 atrial flutter cases. Mean dose given was 860.7 mg (SD +/- 231.2 mg), and median time to conversion was 55 minutes. Adverse events occurred in 34 cases (10.0%): hypotension, 8.5%; bradycardia, 0.6%; atrioventricular block, 0.6%; and ventricular tachycardia, 0.3%. There were no cases of torsades de pointes, cerebrovascular accident, or death. Most patients (94.4%) were discharged home, but 2.9% of patients returned with a recurrence of atrial fibrillation within seven days.

CONCLUSIONS

This study of acute atrial fibrillation or flutter patients treated in the ED with IV procainamide suggests that this treatment is safe and effective in this setting. Procainamide should be prospectively compared with other ED strategies.

Comparative study of intravenous amiodarone and procainamide in the treatment of atrial fibrillation of recent onset

AIM

The aim of the present study was to compare the safety and efficacy of amiodarone and procainamide in the acute cardiology setting.

METHODS

The study population consisted of 223 patients with symptomatic atrial fibrillation (AF). After administration of digoxin for ventricular rate control, all patients who failed to restore sinus rhythm (SR) were randomized into 2 groups: group A (113 patients) were administered 300 mg amiodarone intravenously over 30 min and, in case of failure to restore SR, amiodarone of 20 mg/kg/24 h was administered intravenously. Group B (110 patients) were intravenously administered a bolus dose of 1 gm procainamide, at an infusion rate 50/mg/min, and, in case of failure to restore SR, 2 mg/min for the next 24 h.

RESULTS

The rate of cardioversion to SR was similar between amiodarone (81.4%) and procainamide (82.7%) (P=NS). Procainamide loading recorded faster cardioversion times than amiodarone loading (P=0.02), but there was no significant difference after that. Amiodarone caused a significant decrease on systolic blood pressure compared to procainamide for the first 18 h (P<0.001), and a significant decrease in the diastolic blood pressure for the first 6 h (P<0.001). Side-effects for either medication were sparse. The only real prognostic factor for successful cardioversion remains the size of left atrium.

CONCLUSION

Both drugs were equally effective in restoring SR, though procainamide acts quicker in the loading phase. Both medications are safe and side effects develop only in the maintenance phase.

A comparative study of the efficacy and safety of procainamide versus propafenone versus amiodarone for the conversion of recent-onset atrial fibrillation

The appropriate treatment for the restoration of sinus rhythm in patients with atrial fibrillation (AF) of recent onset is still the subject of controversy. In this prospective, randomized, single-blind, placebo-controlled clinical study, we investigated the effectiveness and safety of procainamide, propafenone, and amiodarone, administered intravenously, for the conversion of recent-onset AF. We enrolled 362 consecutive patients (183 men; age 34 to 86 years; mean 65+/-10) with AF duration of no >48 hours. Of these patients, 89 were given procainamide, 91 propafenone, 92 amiodarone, and 90 placebo. Treatment was considered successful if conversion to sinus rhythm was achieved within the 24-hour study period. Baseline clinical characteristics were similar in the 4 groups. The treatment was successful in 61 of the 89 patients who received procainamide (68.53%; median time 3 hours), 73 of the 91 patients who received propafenone (80.21%; median time 1 hour), 82 of the 92 patients who received amiodarone (89.13%; median time 9 hours), and 55 of the 90 patients who received placebo (61.11%; median time 17 hours; p<0.05 for all medicated groups vs placebo; p<0.05 for amiodarone and propafenone vs procainamide). In conclusion, all 3 medications, when administered intravenously, are effective in the restoration of sinus rhythm in recent-onset AF. Amiodarone and propafenone are more effective whereas procainamide and propafenone are faster.

Therapeutic Levels of Intravenous Procainamide in Neonates: A Retrospective Assessment

STUDY OBJECTIVES

To evaluate dosing and pharmacokinetic parameters of intravenous continuous-infusion procainamide in neonates, and to identify dosage regimens and factors leading to therapeutic procainamide levels and minimal adverse events.

DESIGN

Retrospective, observational study.

SETTING

Pediatric hospital.

PATIENTS

. Twenty-one patients (seven preterm, 14 full term) younger than 30 days who received continuous-infusion procainamide therapy for more than 15 hours or had two consecutive therapeutic procainamide levels obtained while receiving therapy between June 1, 2002, and December 31, 2005.

MEASUREMENTS AND MAIN RESULTS

Data on demographics, dosing, drug levels, and adverse effects were collected. Doses that achieved therapeutic levels were documented, and procainamide clearance was calculated and evaluated with regard to renal function and gestational age in patients who were at steady state. Mean clearance and mean N-acetylprocainamide (NAPA):procainamide ratios were compared between preterm and term neonates. No patients experienced hemodynamic instability or other adverse effects due to procainamide. Procainamide was given as a mean +/- SD 9.6 +/- 1.5-mg/kg bolus in 20 of 21 patients before continuous infusion. The mean +/- SD dose at which two therapeutic levels were achieved was 37.56 +/- 13.52 microg/kg/minute. Procainamide clearance was 6.36 +/- 8.85 ml/kg/minute and correlated with creatinine clearance (r=0.78, p<0.00001) and age at day of sampling (r=0.49, p<0.00001). The NAPA:procainamide ratio at steady state was 0.84 +/- 0.53; two patients were determined to be fast acetylators (ratio > 1). Preterm infants had lower mean clearance rates (p<0.001) but higher NAPA:procainamide ratios (p<0.01) than those of term infants. Five patients experienced seven supratherapeutic levels while receiving therapy; four of these patients were preterm, and all had creatinine clearances less than 30 ml/minute/1.73 m(2). Three patients had four pairs of levels obtained after discontinuation of procainamide, and elimination rate constant and half-life were calculated.

CONCLUSION

Procainamide can be safely used in neonates, with no short-term adverse effects. The dosage regimen for intravenous procainamide required to achieve therapeutic levels in neonates is similar to that of older infants and children. Doses may need to be reduced in premature infants and in those with renal dysfunction.

Study of feasibility of the treatment with procainamide hydrochloride and cisplatin in pregnant mice

Cisplatin is one of the most widely utilized anticancer drugs; nevertheless its use is often hampered by the onset of serious side effects. In spite of its tight binding to DNA, great teratogenic effects do not characterize cisplatin, although its embryolethal and growth retardation activities are quite remarkable. On the basis of our previous observations, demonstrating the usefulness of procainamide hydrochloride for the protection against cisplatin toxic effects in adult mice and rats, we now analyze the feasibility of the combined treatment with cisplatin and the antiarrhythmic drug procainamide hydrochloride in pregnant mice and the possible protective action of procainamide against the embryotoxic activity of cisplatin. Our data, obtained in CD-1 dams after treatment with 8 or 12 mg/kg cisplatin ip, with or without 50 mg/kg procainamide hydrochloride iv, confirm the embryotoxic effects of cisplatin. We also demonstrate that procainamide may be administered with cisplatin without causing an increase in its embryotoxic effects, but slightly improving some embryotoxicity parameters in living embryos such as the fetal weight, the percentage of fetuses with skeletal anomalies, and the number of ossification centres. The mechanism of action of this partially protective activity seems to be linked in part to the lower cisplatin accumulation in fetal tissue, probably due to an interaction of drugs at the level of placenta, in part to the protection of procainamide against maternal toxicity of cisplatin. A relevant result of this research is the suggestion that procainamide hydrochloride might be administered in case of pregnancy to protect against the maternal toxic effects of cisplatin without an increased embryotoxic/teratogenic risk for the offspring.

Intrapericardial drug delivery: pharmacologic properties and long-term safety in swine

BACKGROUND

Intrapericardial drug delivery is a promising new technique, but the pharmacologic properties of various agents delivered via this route are not known. Furthermore, the long-term safety of intrapericardial catheters has not been previously examined.

METHODS

Using a pericardial access device, a catheter connected to a drug-delivery system was implanted in five pigs. Plasma levels and electrocardiographic measurements were obtained after intravenous and intrapericardial administration of digoxin and procainamide. Histological examination was performed after the device had been implanted for a total of 6 months.

RESULTS

The QTc interval did not change significantly after digoxin or procainamide intravenous administration. QTc decreased by 47+/-23 ms (p=0.046) 8 h after digoxin intrapericardial administration and increased by 128+/-60 ms (p=0.002) 1 h after procainamide intrapericardial administration. The QRS duration did not change significantly after intravenous administration of either agent, but it increased by 17+/-9 ms (p=0.004) 1 h and by 15+/-4 ms (p=0.01) 8 h after procainamide intrapericardial administration. After intravenous procainamide the RR interval decreased, but it did not change significantly after intrapericardial administration of either agent. Histology showed moderate inflammatory infiltration and fibrosis adjacent to the catheter.

CONCLUSIONS

Intrapericardial delivery of digitalis and procainamide produces unique electrophysiological properties. In contrast to satisfactory success of the implantation technique, long-term dwell of the catheter in the pericardium induces moderate, albeit probably clinically significant, fibrosis.

Effects of procainamide on electrical activity in thoracic veins and atria in canine model of sustained atrial fibrillation

Focal discharges (FDs) are present in thoracic veins during atrial fibrillation (AF). We hypothesize that procainamide exerts its anti-AF action by suppressing FDs in the thoracic veins. We studied six mongrel dogs (22-27 kg) with sustained (>6 h) AF induced by 47 +/- 20 days of chronic rapid LA appendage (LAA) or pulmonary vein (PV) pacing. Procainamide was infused intravenously until AF was terminated or a cumulative dose of 20 mg/kg was reached. High-resolution mapping during AF showed FDs in the vein of Marshall, PVs, and the LAA. Procainamide significantly (P < 0.05) reduced the frequency of these FDs and suppressed the interactions of wave fronts between PVs and LA. The cumulative dose of PA needed to terminate AF correlated negatively (r =-0.9, P < 0.05) with the baseline effective refractory period (ERP) of PV and positively (r = 0.8, P < 0.05) with the baseline maximum dominant frequency (DF) of AF. In four of five dogs, AF converted to atrial tachycardia originating from the PVs before termination. Attempts to reinduce sustained AF were unsuccessful in these five dogs. AF was resistant to procainamide in the sixth dog. In conclusion, procainamide reduced the rate of FDs in the thoracic veins and the LA and suppressed the interaction between PVs and LA. Second, FDs in the PV are more resistant to procainamide's action than FDs in the atria. Third, inherent PV ERP is important in determining the antifibrillatory efficacy of procainamide.

DNA methylation inhibitor, procainamide, may decrease the tamoxifen resistance by inducing overexpression of the estrogen receptor beta in breast cancer patients

Estrogen is the main stimulant in the development and growth of breast cancer. The estrogen receptor antagonist tamoxifen has been mainstay of hormonal therapy. Although tamoxifen has been an effective adjuvant therapy, approximately 30% of patients treated with this agent still die within 10 years of follow-up treatment, and relapses can occur for > or = 20 years following therapy. However, the underlying cause of treatment failure in many breast cancer patients receiving tamoxifen is resistance to tamoxifen. ERbeta may influence estrogen action through the ERalpha pathway and the hormone refractoriness of breast cancer. ERbetacx, the carboxy terminal splicing variant of ERbeta, has been considered a dominant repressor of ERalpha function, because ERbetacx inhibits transcriptional activity of ERalpha rather than ERbeta wild type (wt). Tamoxifen responders tended to exhibit a lower ratio of ERbetacx to ERbetawt than non-responders. Induction of ERbeta reduces growth of exponentially proliferating cells. Since the promoter region of ERbeta is rich in CpG dinucleotides, loss of expression of ERbeta observed in some tumours could be due to aberrant methylation of CpG islands. Treatment of ERbeta-negative cell lines with DNA methyl transferase inhibitors restored ERbeta expression, providing experimental evidence that silencing of ERbeta in breast carcinomas could be due to promoter hypermethylation. Procainamide, used for cardiac arrhythmias, has been proposed as being a non-nucleoside inhibitor of DNA methylation and also demthylates and reactivate tumor suppressor genes in breast cancer cell lines. Therefore, concomitant use of procainamide with tamoxifen in ERalpha-positive and ERbeta-negative breast cancers may increase the tamoxifen response. Procainamide, given orally may also be used in breast cancer patients who developed resistance during the tamoxifen treatment. In vivo and in vitro studies evaluating effectiveness of concomitant use of procainamide and tamoxifen in tamoxifen resistant and ERbeta-negative breast cancer may further support our hypothesis.

Pharmacokinetic and pharmacodynamic analysis of platinum after combined treatment of cisplatin and procainamide hydrochloride in mice bearing P388 leukemia

BACKGROUND

Our previous studies showed that procainamide hydrochloride may be an important modulator of cisplatin toxicity and antitumour activity. This study was performed in order to investigate if procainamide hydrochloride may influence the therapeutic index of cisplatin by inducing modifications of its pharmacokinetics and pharmacodymanics in vivo.

MATERIALS AND METHODS

The pharmacokinetic profile of cisplatin administered either in the presence or absence of procainamide hydrochloride was investigated in BDF1 female mice bearing 6-day P388 leukemia. Procainamide hydrochloride was administered i.v. at the dose of 50 mg/kg, immediately before cisplatin which, in turn, was administered i.p. at the dose of 8 mg/kg.

RESULTS

The combined administration of the antiarrhythmic drug and cisplatin caused significant differences in the pharmacokinetic profiles of Pt in plasma, ascites fluid and tissues. Filterable Pt was significantly increased both in plasma and ascites fluid in animals given the combined treatment. Similarly, a small increase was also found for total plasma Pt. These differences caused some changes of the pharmacokinetic parameters of filterable (plasma: AUC0-1 h = +16%, t1/2 alpha = +29%, t1/2b = +14%, K2p = -32%; ascites fluid: AUC0-1 h = +23%, t1/2 alpha = +78%, t1/2 beta = -49%, and total Pt (plasma: AUC0-1 h = +19%, t1/2 alpha = +27%, t1/2 beta = -22%; ascites fluid: AUC0-1 h = +6%, AUC0-infinity = +43%, t1/2 alpha = +30%). The analysis of tissue Pt content showed the general increase of Pt concentration in the main organs of animals treated with cisplatin and procainamide hydrochloride, with AUC0-24 h increased by 95%, 22%, 90% and 28% in kidney, liver, spleen and lung, respectively. The analysis of binding of Pt to DNA and percent interstrand cross-links (%ISCL) in P388 tumour cells showed that the % ISCL (10.44 +/- 3.81% vs. 3.51 +/- 0.01%) and the efficiency of ISCL formation (0.51 +/- 0.14 vs. 0.17 +/- 0.02 %ISCL.microgram DNA/pg Pt) were significantly greater when cisplatin was administered in association with procainamide hydrochloride.

CONCLUSION

Our results show that procainamide hydrochloride may alter the pharmacodynamics and the pharmacokinetics and distribution of Pt in tumored mice treated with cisplatin.

Comparison of the in vivo electrophysiological and proarrhythmic effects of amiodarone with those of a selective class III drug, sematilide, using a canine chronic atrioventricular block model

Amiodarone effectively blocks both the sodium and calcium channels and beta-adrenoceptors, in addition to blocking several potassium currents including IKr, IKs, Ito, IK1, IKACh and IKNa. The incidence of clinical torsade de pointes (TdP) associated with amiodarone has been reported to be low and the present study compared the proarrhythmic potential of amiodarone with that of a selective IKr channel blocker, sematilide, using a canine chronic atrioventrucular block model. Amiodarone or sematilide (3 and 30 mg/kg; n=4 for each group) was administered orally without anesthesia under continuous ECG monitoring. Both drugs prolonged the QT interval, although the onset was faster for sematilide. The high dose of sematilide induced TdP in 3 of 4 animals, which caused their death, but neither the low dose of sematilide nor the 2 dosages of amiodarone induced lethal ventricular arrhythmias. These results suggest that IKr channel inhibition by amiodarone with its additional ion channel blocking action may contribute to the prevention of TdP.

Intrapericardial therapeutics: a pharmacodynamic and pharmacokinetic comparison between pericardial and intravenous procainamide delivery

INTRODUCTION

Procainamide delivery into the pericardial space may produce a greater and more prolonged electrophysiologic effect, particularly in thin superficial atrial tissue, compared with intravenous delivery.

METHODS AND RESULTS

Swine were randomized to sequential procainamide doses delivered intravenously (n = 6) or into the pericardial space (n = 7). The cumulative pericardial doses were 0.5, 1.5, and 3.5 mg/kg, and the intravenous doses were 2, 10, and 26 mg/kg. Pericardial procainamide prolonged right atrial effective refractory period from baseline by 22% (P < 0.01) but only at the 3.5 mg/kg cumulative dose. This dose slowed interatrial conduction time by 14% (P < 0.05) and raised atrial fibrillation threshold by 70 mA (P < 0.05). Pericardial procainamide had minimal effect on ventricular electrophysiology. Similar results occurred with a single 2 mg/kg pericardial dose in a closed chest model. Intravenous 10 and 26 mg/kg cumulative doses prolonged atrial effective refractory period from baseline by 24% and 18% (P < 0.01), respectively. The 26 mg/kg cumulative intravenous dose slowed interatrial and atrial-ventricular conduction times by 27% and 17%, respectively (P < 0.05), raised atrial fibrillation threshold, and slowed ventricular conduction time by 29% (P < 0.05). Pericardial procainamide produced pericardial fluid concentrations ranging from 250 to 1,500 microg/mL, but plasma concentrations were <1 microg/mL. Intravenous procainamide doses produced pericardial fluid concentrations similar to plasma trough concentrations 0 to 12 microg/mL.

CONCLUSION

The single 2 mg/kg and 3.5 mg/kg cumulative pericardial procainamide doses prolonged atrial refractoriness and raised atrial fibrillation threshold similar to the 26 mg/kg cumulative intravenous dose, but the duration of effect was similar between delivery methods. Pericardial procainamide did not affect global or endocardial ventricular electrophysiology nor was it associated with ventricular proarrhythmia.

Effects of a typical I(Kr) channel blocker sematilide on the relationship between ventricular repolarization, refractoriness and onset of torsades de pointes

The effects of a typical I(Kr) channel blocker sematilide on the relationship between ventricular repolarization, refractoriness and onset of torsades de pointes (TdP) were studied using the canine isolated, blood-perfused ventricular septum preparation with monophasic action potential (MAP) recording. Intracoronary infusion of sematilide (10-100 microg/min) prolonged the repolarization phase and effective refractory period, the extent of which was greater in the former than in the latter, resulting in prolongation of terminal repolarization process. Prolonging the basic pacing cycle length from 400 to 600 ms and/or increasing the drug doses enhanced each of these actions. Reverse use-dependence was obvious in the drug-induced prolongation of MAP duration, but it was less clear in the effective refractory period. More importantly, during sematilide infusion, in preparations paced at longer basic cycle length of 600 - 2000 ms, TdP-like polymorphic ventricular tachycardia was repeatedly induced by an extra-stimulus applied on the terminal repolarization phase, which indicates the appearance of electrically vulnerable period. Prolonging the basic pacing cycle length and/or increasing the drug doses prolonged this electrically vulnerable period in parallel with the terminal repolarization phase. These results suggest that prolongation of the terminal repolarization process by sematilide would enhance the chance of conduction slowing at less complete repolarization levels, which may be associated with a high incidence of TdP induction.

Interaction of bisoprolol and procainamide in human cardiac impulse generation and conduction

Combined treatment of beta-adrenoceptor-blocking agents and class I antiarrhythmic drugs can potentially have profound and deleterious effects on cardiac impulse formation and conduction. We studied the effect of 5 mg of oral bisoprolol daily and 10 mg/kg of procainamide intravenously with programmed electrical stimulation of the heart in 10 patients with postinfarction ventricular tachyarrhythmias. Oral bisoprolol slowed sinus rhythm and atrioventricular nodal conduction; ventricular effective refractory periods were increased significantly after several days of oral bisoprolol treatment. Combined treatment of oral bisoprolol and intravenous procainamide did not produce clinically relevant changes in parameters of cardiac impulse formation and conduction. This study shows that combined use of bisoprolol and a class I antiarrhythmic drug appears to be safe in patients with ventricular tachyarrhythrhythmias late after myocardial infarction.

In vitro production of antibodies to histones in patients receiving chronic procainamide therapy

OBJECTIVE

Procainamide related autoimmunity is characterized by the production of antibodies to histones and, in particular, to the H2A-2B dimer. We evaluated in vitro production of antibodies to total histones and the H2A-2B dimer by peripheral blood mononuclear cells (PBMC) from patients chronically exposed to procainamide and related this to in vivo production, and assessed possible immunostimulatory response by the postulated reactive metabolite procainamide hydroxylamine (PAHA) using PAHA conjugated autologous erythrocytes.

METHODS

We evaluated in vitro spontaneous and mitogen induced production of histone antibodies by PBMC from 26 asymptomatic patients, who were chronically receiving procainamide, in the presence and absence of PAHA conjugated autologous erythrocytes. Correlations with in vivo production were sought.

RESULTS

PBMC from 9 patients revealed significant spontaneous production of histone antibodies, of whom 2 developed procainamide related lupus within 2 mo of the evaluation. There was a significant increase in in vitro production of antibodies to total histones by PBMC that had been cultured in the presence of PAHA-autologous erythrocyte conjugates, but in the absence of mitogens, from 15 (65%) of 23 patients, and of antibodies to H2A-2B by cells from 10 (42%) of 24 patients. Patients' cells that were co-cultured with PAHA-erythrocyte conjugates produced significantly greater amounts of antibodies to both total histones (p = 0.03) and the H2A-2B dimer (p = 0.009) compared with those cultured alone. Co-culture with similarly pretreated erythrocytes also resulted in a significant increase in the production of antibodies to total histones (p < 0.001), but not to the H2A-H2B dimer, by cells from controls.

CONCLUSION

Some patients receiving chronic procainamide therapy have spontaneous production of histone antibodies. Co-culture with PAHA-erythrocyte conjugates resulted in significantly greater production, suggesting an immunomodulating effect by this metabolite.

Comparison of the effects on drug concentrations, electrophysiologic parameters, and termination of atrial fibrillation in dogs when procainamide and ibutilide are delivered into the right atrium versus intravenously

INTRODUCTION

We tested the hypothesis that right intra-atrial (i.a.) administration of antiarrhythmic drugs resulted in higher peak serum drug concentrations, greater electrophysiologic effects, and greater efficacy for termination of atrial fibrillation (AF) than intravenous (i.v.) drug delivery.

METHODS AND RESULTS

Eight dogs were treated with 9.7 mg/kg procainamide infusion and eight dogs with 0.02 mg/kg ibutilide infusion, injected over 5 minutes. Each dog had both an electrophysiologic (EP) and an AF termination study during i.a. and i.v. drug administration at > or = 2-day intervals (total four studies each). Right atrial pacing capture threshold, right atrial effective refractory period (ERP), right atrial and right ventricular monophasic action potential (MAP) durations at 70% and 90% of repolarization (MAPD70, MAPD90), AH, HV, and QT intervals, QRS width, intra-arterial systolic and diastolic blood pressures, and cardiac output were measured at different time-points. Blood samples were drawn from the coronary sinus and femoral vein for drug level determination. The right atrium was paced at 400-msec cycle length throughout the study. AF was induced by rapid right atrial pacing and maintained by methacholine infusion at 1.5 to 3 microg/kg/min. The sustained AF was allowed to persist for 10 minutes before starting the antiarrhythmic drug infusion. We found no significant difference between the procainamide concentrations in the coronary sinus and femoral vein during i.a. and i.v. drug delivery. The time course and extent of increase in right atrial ERP, MAPD70, MAPD90, and all the other measured EP parameters did not differ between the two routes of drug administration. No significant difference was found in termination of AF between i.v. (5/7 procainamide; 4/8 ibutilide) or i.a. (3/8 procainamide; 3/8 ibutilide) drug delivery or between drugs (8/15 procainamide; 7/16 ibutilide).

CONCLUSION

Our data do not support any beneficial effect of i.a. versus i.v. procainamide or ibutilide delivery.

Rate-control versus conversion strategy in postoperative atrial fibrillation: a prospective, randomized pilot study

BACKGROUND

Atrial fibrillation remains a frequent complication after heart surgery. The optimal strategy to treat the condition has not been established. Several retrospective studies have suggested that a primary rate-control strategy may be equivalent to a strategy that restores sinus rhythm.

METHODS

Fifty patients with atrial fibrillation after heart surgery were randomly assigned to a strategy of antiarrhythmic therapy with or without electrical cardioversion or ventricular rate control. Both arms received anticoagulation with heparin overlapped with warfarin. The primary end point was time to conversion to sinus rhythm analyzed by the Kaplan-Meier method. Atrial fibrillation relapse after the initial conversion was monitored in the hospital over a 2-month period.

RESULTS

There was no significant difference between an antiarrhythmic conversion strategy (n = 27) and a rate-control strategy (n = 23) in time to conversion to sinus rhythm (11.2 +/- 3. 2 vs 11.8 +/- 3.9 hours; P =.8). With the use of Cox multivariate analysis to control for the effects of age, sex, beta-blocker usage, and type of surgery, the antiarrhythmic strategy showed a trend toward reducing the time from treatment to restoration of sinus rhythm (P =.08). The length of hospital stay was reduced in the antiarrhythmic arm compared with the rate-control strategy (9.0 +/- 0.7 vs 13.2 +/- 2.0 days; P =.05). In-hospital relapse rates in the antiarrhythmic arm were 30% compared with 57% in the rate-control strategy (P =.24). There were no significant difference in relapse rates at 1 week (24% vs 28%), 4 weeks (6% vs 12%), and 6 to 8 weeks (4% vs 9%). At the end of the study, 91% of the patients in the rate-control arm were in sinus rhythm compared with 96% in the antiarrhythmic arm (P =.6).

CONCLUSIONS

This pilot study shows little difference between a rate-control strategy and a strategy to restore sinus rhythm. Regardless of strategy, most patients will be in sinus rhythm after 2 months. A larger randomized, controlled study is needed to assess the impact of restoration of sinus rhythm on length of stay.

Serial evaluation of left atrial dimension after cardioversion for atrial fibrillation and relation to atrial function

The size of the left atrium is usually increased during atrial fibrillation (AF). The aim of the present study was to evaluate changes in left atrial (LA) dimension after cardioversion for AF, and the relation between LA dimension and atrial function. The initial study population included 171 consecutive patients. Patients who had spontaneous cardioversion to sinus rhythm (56 patients) were compared with patients who had random cardio-version with drugs (50 patients) or direct-current (DC) shock (50 patients). Echocardiographic evaluations included LA size and volume. LA passive and active emptying volumes were calculated, and LA function was assessed. Atrial stunning was observed in 18 patients reverted with DC shock and in 7 patients reverted with drugs. The left atrium was dilated in all patients during AF (48 +/- 5 mm). The size of the left atrium decreased after restoration of sinus rhythm in all patients with spontaneous reversion to sinus rhythm, in 73% of patients reverted with drugs, and in 50% of patients reverted with DC shock. The comparison between patients with a normal mechanical atrial function and patients with reduced atrial function showed that a higher atrial ejection force was associated with a more marked reduction in LA size after restoration of sinus rhythm. A relation between LA volumes and atrial ejection force was observed in the group of patients with depressed atrial mechanical function (r = -0.78; p <0.001). The active emptying fraction was lower, although not significantly, in this group, whereas the conduit volume was increased. Thus, a depressed atrial mechanical function after cardioversion for AF was associated with a persistence of LA dilation.

Procainamide for rate control of postsurgical junctional tachycardia

This study was conducted to determine the efficacy of procainamide therapy for rapid rate control of postoperative junctional tachycardia (JT). Postoperative JT is one of the most difficult forms of tachycardia to manage. Reported success with a variety of treatments of JT in infants and children has been inconsistent and limited. Rate control using procainamide was achieved in 17 children having rapid JT (heart rate >200 beats/min) between 1986 and 1997. In the first 5 patients (protocol A), following a loading dose of 3 mg/kg over 20 minutes, a continuous procainamide infusion was initiated at a rate of 20 microg/kg/min. The infusion dose was increased in 10 microg/kg steps every 30 minutes to 40-120 microg/kg/min until the heart rate decreased below the target rate of 180 beats/min. In the other 12 patients (protocol B), after a higher loading dose of 10 mg/kg the infusion rate was increased every 10-15 minutes until the heart rate decreased below the target rate of 180 beats/min. Procainamide decreased JT rates in all patients but the response was significantly faster in protocol B. In the patients treated with protocol A, pretreatment JT rates ranged from 203 to 240 (213+/-17) beats/min and decreased to 195+/-10 beats/min at 2 hours (p = ns), 186+/-8.8 at 4 hours (p<0.02), and 179+/-8 at 6 hour postinitiation of PA. In protocol B, pretreatment JT rates ranged from 201 to 240 (218+/-17) beats/min and decreased to 183+/-20 beats/min at 2 hours (p<0.001) and 171+/-12 at 4 hours after starting the procainamide therapy. The mean duration to decrease JT rates below the target rate of 180 beats/min was 3.2+/-1.1 hours in protocol B compared to 6.4+/-3.8 hours in protocol A (p<0.02). Eight of 12 patients in protocol B achieved rate control below the target rate of 180 beats/min within 4 hours despite remaining on significant inotropic support. The procainamide infusion rates to maintain heart rates below 180 beats/min were 40-120 (68.4+/-22.1) microg/kg/min. No proarrhythmia, bradycardia, or significant hypotension was observed. In this series procainamide provided safe, effective, and rapid rate control of JT occurring in the immediate postoperative period.

Adenosine induced atrial fibrillation precipitating polymorphic ventricular tachycardia

An 86-year-old female developed supraventricular tachycardia 36 hours after a myocardial infarction (MI). She developed atrial fibrillation and polymorphic ventricular tachycardia (PVT) following administration of 12 mg of adenosine. The PVT caused hemodynamic instability with no response to cardioversion, but termination with procainamide. The heart is vulnerable to hemodynamically unstable, possibly lethal, PVT early after MI under some circumstances. This vulnerability may be exposed following administration of adenosine. Extra caution is warranted when using adenosine in the post-MI period.