Effects of dofetilide, a class III antiarrhythmic drug, on various ventricular arrhythmias in dogs

Dofetilide, a new class III antiarrhythmic agent, was tested in various kinds of canine ventricular arrhythmias to compare its effects with those of other class III agents. Ventricular arrhythmia models used were induced by two-stage coronary ligation, digitalis, epinephrine, coronary ligation and reperfusion, and programmed electrical stimulation (PES). Dofetilide (100 micrograms/kg intravenously) did not suppress automaticity arrhythmias induced by two-stage coronary ligation and epinephrine or the coronary ligation and reperfusion arrhythmias, but suppressed the reentry arrhythmia induced by PES in dogs with old myocardial infarction (MI). This effect was associated with a prolongation of QT interval. Dofetilide also showed antiarrhythmic effect in some dogs with digitalis arrhythmia. Dofetilide increased QT interval and showed negative chronotropic effect like that of other class III drugs, but was different in antiarrhythmic profiles from those of other class III agents such as D-sotalol, E-4031, and MS-551 in that it did not prevent the occurrence of ventricular fibrillation (VF) immediately after coronary reperfusion and had some antiarrhythmic effects on digitalis arrhythmia.

Reversal of Borrelia burgdorferi associated dilated cardiomyopathy by antibiotic treatment?

It is suggested that Borrelia burgdorferi infection could be associated with dilated cardiomyopathy (IDC). Stanek et al. were able to cultivate Borrelia burgdorferi from myocardial biopsy tissue of a patient with longstanding dilated cardiomyopathy. Here we present a study in which we examined the effect of standard antibiotic treatment on the left ventricular ejection fraction (LVEF) in patients with dilated cardiomyopathy associated with Borrelia burgdorferi infection. In this study we assessed the serum (IgG, IgM Elisa) and history of 46 IDC patients with specific regard to Borrelia burgdorferi infection (mean LVEF 30.4 +/- 1.3%, measured by cardiac catheterization and echocardiography with the length-area-volume method). All 46 patients received standard treatment for dilated cardiomyopathy: ACE inhibitors, digitalis, and diuretics. Eleven (24%) patients showed positive serology and a history of Borrelia burgdorferi infection; nine of these also had a typical history of tick bite and erythema chronicum migrans (ECM) and/or other organ involvement, and two had no recollection of tick bite or ECM but showed other Borrelia burgdorferi-associated disorders (neuropathy, oligoarthritis). These 11 patients with Borrelia burgdorferi infection received standard antibiotic treatment with intravenous ceftriaxone 2 g bid for 14 days. Six (55%) recovered completely and showed a normal LVEF after 6 months, three (27%) improved their LVEF, and two (18%) did not improve at all. This amounts to nine (82%) patients with recovery/improvement in the Borrelia burgdorferi group. The 35 patients who did not show positive serology or a history of Borrelia burgdorferi infection did not receive antibiotic treatment. In this group without Borrelia burgdorferi infection 12 (26%), showed recovery/improvement following the standard treatment of dilated cardiomyopathy (see earlier). Our results indicate that Borrelia burgdorferi infection could play a decisive role in the development of dilated cardiomyopathy, especially in a geographical region such as Graz, where Borrelia burgdorferi is endemic. While we are aware of the small number of Borrelia burgdorferi patients in this study, we nevertheless conclude that in a remarkable number of patients with signs of Borrelia burgdorferi infection, dilated cardiomyopathy could be reversed and LVEF improved.

Antiarrhythmic effects of optical isomers of disopyramide on canine ventricular arrhythmias

Disopyramide is an effective class I antiarrhythmic drug and widely used for the treatment of arrhythmias, but it has anticholinergic side effects. In vitro studies demonstrated that dextrorotatory (D-) disopyramide has a stronger anticholinergic action, whereas the levorotatory (L-) isomer has a stronger Na channel blocking action. Because the antiarrhythmic mechanism of disopyramide suppressing digitalis- and two-stage coronary ligation-induced canine ventricular arrhythmias is the drug-induced Na channel block, we examined the antiarrhythmic efficacy of D- and L-disopyramide on two arrhythmia models. On ouabain-induced ventricular tachycardia (VT), L-disopyramide 3 mg/kg decreased the arrhythmic ratio (number of ectopic beats/total heart rate), whereas the same dose of the D-isomer was ineffective and a higher dose (5 mg/kg) was needed to suppress the arrhythmia. The effective plasma concentrations (IC50) decreasing the arrhythmic ratio to 50% of the control were 5.3 and 11.3 mu g/ml for L- and D-disopyramide, respectively. We obtained similar results using 24-h two-stage coronary ligation VT. The IC50 were 8.9 and 22.2 mu g/ml for the L- and D-isomers, respectively. Our results indicate that L-disopyramide is about twice as strong an antiarrhythmic drug as the D-isomer.

[Main cardiotoxic drugs]

A review of the most important iatrogenic pictures is reported. Chemotherapeutic agents, antidepressants, cocaine and amphetamine, oral contraceptives and antiarrhythmic drugs are examined.

Acute antiarrhythmic effects of intravenously administered amiodarone on canine ventricular arrhythmia

We investigated antiarrhythmic effects of intravenously (i.v.) administered amiodarone using four canine ventricular arrhythmia models. Bolus injections of amiodarone 3 mg/kg suppressed epinephrine (EPI)-induced arrhythmia and 5-mg/kg bolus injections of amiodarone suppressed digitalis- and two-stage coronary ligation-induced arrhythmia models, but the antiarrhythmic effects did not correlate with the amiodarone plasma concentrations. The infusion of amiodarone 6.67 mg/kg/h did not prolong the QTc interval or produce antiarrhythmic effects in coronary ligation and reperfusion experiments. Amiodarone significantly decreased the mean blood pressure (MAP), and this effect lasted throughout the observation period. The results indicate that the antiarrhythmic effects of intravenously administered amiodarone may not be due to its class III action, but to other actions, such as class I, II and IV actions.

Patterns of medication use in patients with heart failure: a report from the Registry of Studies of Left Ventricular Dysfunction (SOLVD)

To determine patterns of medication use based on clinical variables in patients with heart failure, we analyzed data from 5,999 patients participating in the Registry of Studies of Left Ventricular Dysfunction (SOLVD). The Registry comprised a broad spectrum of patients with heart failure, including some with predominantly diastolic dysfunction. Drug use was determined in a population cross-sectional manner at the time of identification (74% hospitalized). The median number of drugs per patient was four, with diuretics taken by 62%, digitalis by 45%, angiotensin-converting enzyme inhibitors (ACE-I) by 32%, calcium channel blockers by 36%, antiarrhythmics by 22%, and beta-blockers by 18%. Only 18% were on the combination of ACE-I, diuretic, and digitalis. Stratification for diagnosis, heart failure symptoms, and ejection fractions demonstrated that triple-drug therapy (digitalis, diuretic, and ACE-I) was common only in those with ejection fractions less than .20 and several signs or symptoms of heart failure. Older patients were taking diuretics frequently (73% of patients older than 70 years of age), and our European center used fewer drugs overall, while prescribing digitalis about half as frequently as North American clinics. These data serve as the baseline for analysis of evolving therapeutic practice in patients with heart failure.

[Adenosine triphosphate (ATP) in the management of paroxysmal supraventricular tachycardia: experience in the neonatal period]

INTRODUCTION AND OBJECTIVE

The management of supraventricular tachycardia (SVT) in infants is somewhat controversial since numerous methods of treatment are effective. Regardless of the treatment chosen, it is important to quickly stop the tachycardia in neonates with SVT because they may suddenly become hemodynamically unstable.

METHODS

Seventeen episodes of SVT treated with intravenous ATP are studied in 3 newborns (two were preterm infants: 30 and 34 weeks of pregnancy). Ages at presentation ranged from 2 to 27 days.

RESULTS

ATP is effective in all episodes of SVT, with a mean intravenous doses between 0.10 and 0.50 mg/kg/dose. All patients showed short sinus arrest after ATP. No adverse side effects or hemodynamics changes occurred after ATP administration.

CONCLUSIONS

ATP is a safe and reliable antiarrhythmic in neonatal period, including prematurity. We reviewed the experience in ATP management of SVT, mainly in pediatric population.

[New knowledge on the subject of therapy in cardiac decompensation in the light of large trials]

Although an underlying disturbance in cardiac function can be identified in most patients with congestive heart failure, manifestations of the disease are greatly influenced by other factors, particularly neurohumoral and peripheral adaptive responses which occur secondary to impaired cardiac function. Until recently diuretic agents and digoxin formed the basis of conventional treatment of this condition. The majority of clinical trials published since 1980, indicate that digoxin lessens symptoms and reduces morbidity associated with congestive heart failure particularly in patients with more advanced symptoms and ventricular dysfunction. The efficacy of digitalis in congestive heart failure may in part result from sympathoinhibitory properties such as the activation of baroreceptorial mechanisms. At present there is no conclusive evidence that cardiac glycosides improve survival. Several trials clearly indicate that angiotensin converting enzyme inhibitors (enalapril, captopril) can reduce both morbidity and mortality in symptomatic congestive heart failure. Asymptomatic patients like those with severe left ventricular dysfunction and those who are at high risk for left ventricular remodeling after anterior wall myocardial infarction may also benefit from ACE-inhibition therapy. Increasing evidence suggests that beta-adrenergic blockade can produce symptomatic and hemodynamic improvement in heart failure of idiopathic and ischemic aetiology. Appropriately powered randomized controlled trials are required to determine the impact on survival of beta-blockers.

Optimizing the treatment of heart failure

The introduction of new drugs, and a re-evaluation of older drugs, have radically changed the pharmacological management of heart failure. Angiotensin converting enzyme (ACE) inhibitors, digitalis, diuretics and the combination of nitrates and hydralazine are now used. The first Cooperative North Scandinavian Enalapril Survival Study (CONSENSUS I) and the second Vasodilator therapy in Heart Failure Trial (V-HeFT II) have demonstrated that patients with severe or advanced heart failure should be treated with ACE inhibitors, digitalis and diuretics (other vasodilators can be used if ACE inhibitors are contraindicated) to improve symptoms and duration of life. The Studies Of Left Ventricular Dysfunction (SOLVD) and the Munich Heart Failure trial have shown that patients with mild heart failure should be treated with ACE inhibitors. However, data from several large clinical registries suggest that only 40% of patients with heart failure are being given ACE inhibitors perhaps through fear of serious renal damage or hypotension; these fears are unfounded. Patients with anterior myocardial infarcts and reduced left ventricular function also benefit from ACE inhibitors. The fourth International Study of Infarct Survival (ISIS 4) and results from the Gruppo Italiano per Io Studio della Sopravvivenza nell'Infarto miocardico 3 (GISSI 3) have indicated that patients with acute myocardial infarction benefit from early ACE inhibitor therapy and that survival is increased. Heart failure treatment can be optimized by establishing a disease etiology and stressing the need to restrict dietary sodium. ACE inhibitors should be used for depressed left systolic ventricular function, including patients in New York Heart Association class I heart failure.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of KRN2391 on canine ventricular arrhythmia models

1. KRN2391 (3-30 micrograms/kg, i.v.) produced a decrease in mean blood pressure (MBP) with concomitant increase in heart rate (HR) and change in electrocardiogram (ECG) such as the shortening of PP and PQ intervals and the prolongation of QTc and these changes in HR and ECG were attenuated by pretreatment with propranolol (1 mg/kg) in normal dogs. 2. KRN2391 at 30 micrograms/kg induces neither suppression nor aggravation of ventricular arrhythmias caused by adrenaline and digitalis. 3. In two-stage coronary ligation-induced arrhythmia, KRN2391 inhibited arrhythmia at 48 hr. 4. These results suggest that KRN2391 may be effective on arrhythmia related to ischemia. In addition, it is considered that arrhythmia is not induced even by a high dose of KRN2391 in the normal condition.

Dilated cardiomyopathy in juvenile chronic arthritis

A seven year old boy with seronegative systemic onset juvenile chronic arthritis who developed dilated cardiomyopathy, is presented. Treatment with methotrexate, prednisone, and digitalis has been successful in controlling the acute phase of the disease and congestive heart failure.

Treatment of foxglove extract poisoning with digoxin-specific Fab fragments

A 22-year-old man presented to our emergency department after an intentional overdose of a homemade foxglove extract. Clinical symptoms with symptomatic bradyarrhythmia and ECG changes were consistent with cardiac glycoside poisoning. Treatment with digoxin-specific Fab fragments resulted in transient clinical and ECG improvement. Serum immunoassay demonstrated a digitoxin-like glycoside. The serum levels showed no evidence of altered elimination or distribution with Fab therapy despite temporary improvements in the clinical course. The use of Fab did not result in a shortened clinical course in this episode of foxglove poisoning, as one would expect in the setting of commercial glycoside product poisoning.

Efficacy of phosphodiesterase inhibition with milrinone in combination with converting enzyme inhibitors in patients with heart failure. The Milrinone Multicenter Trials Investigators

We describe the results of two placebo-controlled trials (MIL-1077 and MIL-1078) designed to evaluate the clinical efficacy of oral milrinone administered together with converting enzyme inhibitors to patients with congestive heart failure. Although these trials were terminated prematurely, they provide the only controlled data regarding the effect of oral milrinone on exercise capacity in patients receiving converting enzyme inhibitors. Of the 254 patients randomized, 140 completed one of the trials or reached an end point and are the basis of this report. In both trials, there was a clear trend for an increase in exercise capacity in the milrinone-treated patients (+26 +/- 8% vs. +5 +/- 7% in MIL-1077 and +11 +/- 5% vs. +2 +/- 4% in MIL-1078). Symptoms of congestive heart failure were decreased in one trial but not the other. Quality of life, as assessed by a questionnaire, was not effected in either trial. There was an increased incidence of adverse events in milrinone-treated patients. Adverse events related primarily to hypotension and vasodilation led to discontinuation of drug in 18 milrinone-treated patients vs. 1 placebo-treated patient. Milrinone had little or no proarrhythmic effect and cardiovascular deaths were distributed equally between the milrinone and placebo groups. These data suggest that when used in combination with a converting enzyme inhibitor, oral milrinone improves exercise capacity but is associated with a high incidence of adverse events that appear to be related to excessive vasodilation.