Risk of proarrhythmia with class III antiarrhythmic agents: sex-based differences and other issues

Aggravation of Arrhythmia by Antiarrhythmic Drugs (Proarrhythmia)

Arrhythmia aggravation by antiarrhythmic drugs (proarrhythmia) can be caused by worsening or a change of a preexisting arrhythmia, development of a new arrhythmia, or development of a bradyarrhythmia. Aggravation of arrhythmia usually occurs within several days of beginning an antiarrhythmic drug or increasing the dose of the drug. The time of occurrence is based on the particular drug and its pharmacokinetic properties. Although there are no ways to predict the patient at risk for developing arrhythmia aggravation with any specific agents, risk factors include QT interval prolongation, elevated serum levels of the drug, electrolyte abnormalities, presence of heart failure, a history of a sustained ventricular tachyarrhythmia, and underlying myocardial ischemia.

Amiodarone for the treatment and prevention of ventricular fibrillation and ventricular tachycardia

Amiodarone has emerged as the leading antiarrhythmic therapy for termination and prevention of ventricular arrhythmia in different clinical settings because of its proven efficacy and safety. In patients with shock refractory out-of-hospital cardiac arrest and hemodynamically destabilizing ventricular arrhythmia, amiodarone is the most effective drug available to assist in resuscitation. Although the superiority of the transvenous implantable cardioverter defibrillator (ICD) over amiodarone has been well established in the preventive treatment of patients at high risk of life-threatening ventricular arrhythmias, amiodarone (if used with a beta-blocker) is the most effective antiarrhythmic drug to prevent ICD shocks and treat electrical storm. Both the pharmacokinetics and the electrophysiologic profile of amiodarone are complex, and its optimal and safe use requires careful patient surveillance with respect to potential adverse effects.

Inappropriate Implantable Cardioverter-Defibrillator Therapy

Although improvements in implantable cardioverter-defibrillator (ICD) therapy have taken place, many challenges do remain. Inappropriate delivery of therapy is a big problem that impacts the quality of life of ICD recipients. Although there is now a clear understanding that atrial arrhythmias are the main cause of inappropriate ICD therapies, physicians have not been very successful in preventing them. Additionally, although many tachycardia detection discriminators have been shown to be helpful, it is not clear that there is a particular combination that is ideal for all patients. Until such an algorithm is developed (which may not be possible), a detailed knowledge and use of all available programming options, guided by special characteristics of each unique patient, are the only foreseeable solutions. Finally, one must face the prospect that this problem cannot be vanquished, but only ameliorated.

Drug-induced torsades de pointes: data mining of the public version of the FDA Adverse Event Reporting System (AERS)

AIMS

To investigate spontaneous reports of TdP present in the public version of the FDA Adverse Event Reporting System (AERS) in the light of what is already known on their TdP-liability.

METHODS

Reports of TdP from January 2004 through December 2007 were retrieved from the public version of the AERS database. All reports were selected from REACTION files and the relevant suspected and/or interacting drugs were identified from DRUG files. Qualitative analysis was performed by the case/non-case method. Cases were represented by TdP reports, whereas non-cases were all reports of adverse drug reactions other than TdP. Quantitative analysis was assessed by calculating the crude and adjusted reporting odds ratio (ROR), as a measure of disproportionality, with the 95% confidence interval.

RESULTS

Reports of TdP were 1665 over a 4-year period, involving 376 active substances. Thirty-five drugs with at least 10 reports were identified: amiodarone and methadone were associated with the highest number of cases (113 and 83 respectively) and most of the other reports were ascribable to antibacterials, antidepressants and antipsychotics; remarkable differences in number of cases and ROR were present among agents within each therapeutic class. A disproportionate reporting was also observed for other compounds such as donepezil, famotidine and mitoxantrone.

CONCLUSIONS

Large spontaneous reporting databases represent an important source for signal detection of rare adverse drug reactions (ADR), such as TdP. The number of reports associated to donepezil, famotidine and mitoxantrone could be considered unexpected on the basis of current evidence and needs further investigations on their true TdP-liability.

Women encounter ADRs more often than do men

BACKGROUND

Several publications indicate that the female gender experiences a higher incidence of adverse drug reactions (ADRs) than does the male gender. The reasons, however, remain unclear. Gender-specific differences in the pharmacokinetic and pharmacodynamic behaviour of drugs could not be identified as an explanation. The aim of this study was to analyse ADR risk with respect to gender, age and number of prescribed drugs.

METHODS

A prospective multicenter study based on intensive pharmacovigilance was conducted. Information on patient characteristics and evaluated ADRs was stored in a pharmacovigilance database--KLASSE.

RESULTS

In 2,371 patients (1,012 female subjects), 25,532 drugs were prescribed. In 782 patients, at least one ADR was found. A multivariate regression analysis adjusting for age, body mass index (BMI) and number of prescribed drugs showed a significant influence of female gender on the risk of encountering ADRs [odds ratio (OR) 1.596, confidence interval (CI) 1.31-1.94; p < 0.0001). Dose-related ADRs (51.8%) were the dominant type in female subjects. Comparing system organ classes of the World Health Organisation (SOC-WHO), cardiovascular (CV) ADRs were particularly frequent in female subjects (OR 1.92, CI 1.15-3.19; p = 0.012).

CONCLUSION

Our data confirm the higher risk of ADRs among female subjects compared with a male cohort. Several explanations were investigated. No single risk factor could be identified.

Pharmacological modulation of gap junction function with the novel compound rotigaptide: a promising new principle for prevention of arrhythmias

Existing anti-arrhythmic therapy is hampered by lack of efficacy and unacceptable side effects. Thus, ventricular tachycardia and fibrillation remains the strongest predictor of in-hospital mortality in patients with myocardial infarction. In atrial fibrillation, rhythm control with conventional ion channel blockers provide no therapeutic benefit relative to rate control. Several lines of research indicate that impaired gap junctional cell-to-cell coupling between neighbouring cardiomyocytes is critical for the development of cardiac re-entry arrhythmias. Rotigaptide is the first drug that has been developed to prevent arrhythmias by re-establishing gap junctional intercellular communication. During conditions with acute cardiac ischaemia, rotigaptide effectively prevents induction of both ventricular and atrial tachyarrhythmia. Moreover, rotigaptide effectively prevents ischaemia reperfusion arrhythmias. At the cellular level, rotigaptide inhibits ischaemia-induced dephosphorylation of Ser297 and Ser368, which is considered important for the gating of connexin43 gap junction channels. No drug-related toxicity has been demonstrated at plasma concentrations 77,000 times above therapeutic concentrations. In rats and dogs, rotigaptide reduces infarct size following myocardial infarction. A series of phase I trials has been completed in which rotigaptide has been administered intravenously to ~200 healthy persons. No drug-related side effects have been demonstrated in healthy human beings. Clinical safety, tolerability and efficacy in patients with heart disease are being evaluated in ongoing clinical trials. Rotigaptide represents a pioneering pharmacological principle with a highly favourable preclinical and clinical safety profile, which makes this molecule a promising drug candidate for the prevention of cardiac arrhythmias.

The role of sex-specific results reporting in cardiovascular disease

Cardiovascular disease (CVD) is the primary cause of death among women worldwide. In the United States, more women than men die of CVD every year. Research has shown that there are important sex differences in terms of prevention, diagnosis, treatment, and outcomes in patients with CVD. Although women are being included in clinical trials in increasing numbers, lack of knowledge about sex differences persists because sex-specific analysis and reporting of sex-specific results remains limited. This knowledge gap limits the ability of health care professionals to provide optimal care for both women and men. Ongoing support and encouragement is needed for both the inclusion of sufficient numbers of women in clinical trials and for the reporting of sex-specific results of CVD trials. This increased knowledge and awareness can then be used to optimize high quality care for men and women.

Sex differences in the relationship between amiodarone use and the need for permanent pacing in patients with atrial fibrillation

BACKGROUND

Amiodarone use was associated with an increased need for pacemaker insertion in a retrospective study of patients with atrial fibrillation (AF) and prior myocardial infarction. The aims of this study were to determine prospectively whether amiodarone increases the need for pacemakers in a general population of patients with AF and whether this effect is modified by sex.

METHODS

The study included 1005 patients with new-onset AF who were enrolled in the Fibrillation Registry Assessing Costs, Therapies, Adverse events, and Lifestyle (FRACTAL). Multivariable Cox regression models, including time-dependent covariates accounting for medication exposure, were used to evaluate the risk of pacemaker insertion associated with amiodarone use.

RESULTS

Amiodarone use was associated with an increased risk of pacemaker insertion (hazard ratio [HR], 2.01; 95% confidence interval [CI], 1.08-3.76) after adjustment for age, sex, atrial flutter, coronary artery disease, heart failure, and hypertension. The effect of amiodarone use was modified by sex, with a significant risk in women but not in men (HR, 4.69; 95% CI, 1.99-11.05 vs HR, 1.05; 95% CI, 0.42-2.58 [P = .02]). This interaction remained significant after adjustment for weight, body mass index, weight-adjusted amiodarone dose, and use of other antiarrhythmic or rate control drugs.

CONCLUSION

The risk of bradyarrhythmia requiring pacemaker insertion associated with amiodarone use for AF is significantly greater in women than in men, independent of weight or body mass index.

Domperidone: review of pharmacology and clinical applications in gastroenterology

Domperidone is a dopamine-2 receptor antagonist. It acts as an antiemetic and a prokinetic agent through its effects on the chemoreceptor trigger zone and motor function of the stomach and small intestine. Unlike metoclopramide, it does not cause any adverse neurological symptoms as it has minimal penetration through the blood-brain barrier. It thus provides an excellent safety profile for long-term administration orally in the recommended doses. Domperidone is widely used in many countries and can now be officially prescribed to patients in the United States by an investigational new drug application for the treatment of gastroparesis and any condition causing chronic nausea and vomiting. In view of this additional clinical exposure of domperidone to a new generation of gastroenterologists and other specialists, the purpose of this timely review is to revisit the pharmacology, clinical application, and safety profile of this beneficial medication.

Risk factors and predictors of Torsade de pointes ventricular tachycardia in patients with left ventricular systolic dysfunction receiving Dofetilide

The purpose of this study was to identify risk factors of Torsade de pointes (TdP) ventricular tachycardia in patients medicated with a class III antiarrhythmic drug (dofetilide) and left ventricular systolic dysfunction with heart failure (HF) or recent myocardial infarction (MI). The 2 Danish Investigations of Arrhythmia and Mortality on Dofetilide (DIAMOND) studies enrolled patients with HF (DIAMOND-HF) or MI (DIAMOND-MI) and left ventricular systolic dysfunction. The present analysis includes only patients treated solely with dofetilide. The incidence of TdP was 2.1% (32 of 1,511). Twenty-five of the incidences occurred in the DIAMOND-HF study and 7 cases in the DIAMOND-MI study (p = 0.0015). TdP was more frequent in women than in men (47% vs 28%, p = 0.02). Risk factors for developing TdP were female gender (odds ratio 2.2, 95% confidence interval [CI] 1.0 to 5.0), MI within 8 weeks (odds ratio 0.3, 95% CI 0.1 to 0.7), being in New York Heart Association class III or IV (odds ratio 3.2, 95% CI 1.2 to 8.6), and baseline QTc duration (odds ratio 1.14, 95% CI 1.00 to 1.30) per 10 ms. Women with chronic HF, QTc duration >400 ms. and New York Heart Association class III or IV had a risk of TdP of 10%, whereas no TdP episodes were observed in patients with QTc duration <400 ms. In conclusion, severity of HF, female gender, and QTc duration make it possible to identify patients with a high risk of early TdP when treated with dofetilide. Patients with recent MI less often had TdP compared with patients with chronic HF.

Low rate of sex-specific result reporting in cardiovascular trials

OBJECTIVE

To explore the extent to which sex-specific result (SSR) reporting appears in recently published cardiovascular studies.

METHODS

All original adult cardiovascular clinical trials published in Annals of Internal Medicine, Archives of Internal Medicine, Journal of the American Medical Association, The New England Journal of Medicine, Journal of the American College of Cardiology, The American Journal of Cardiology, and Circulation from July 1 through December 31, 2004, were reviewed. Sex-specific result reporting was defined as presenting primary outcomes for women in a format to allow the data to be abstracted for use in a meta-analysis.

RESULTS

Of the 645 studies reviewed, 17 were excluded because they were appropriately single-sex trials. Of the remaining 628 studies, only 153 (24%) provided SSRs. The percentage of studies reporting SSRs was 37% (23/62) for general medical journals and 23% (130/566) for cardiovascular journals (P = .10). Among National Institutes of Health (NIH)-sponsored research, 31 (51%) of 61 trials analyzed outcomes by sex compared with 125 (22%) of 567 trials not sponsored by the NIH (P < .01).

CONCLUSION

Only a few current cardiovascular trials provide sex-specific data. Sex differences remain poorly understood, and this deficiency limits our ability to optimize medical care for both sexes. The stipulation that SSRs be investigated has led to significantly more SSR reporting in NIH-funded research. A parallel mandate by journal editors that requires authors to provide sex-specific data and analysis may help to bridge this knowledge gap.

Second-generation antipsychotics: is there evidence for sex differences in pharmacokinetic and adverse effect profiles?

Six second-generation antipsychotics (SGAs), aripiprazole, clozapine, olanzapine, quetiapine, risperidone and ziprasidone, are currently US FDA approved. The aim of this review is to investigate whether sex differences exist for efficacy and adverse effects of these drugs.Sex-related differences have been shown in the pharmacokinetics of cytochrome P450 (CYP), with a higher activity in females for CYP3A4 and CYP2D6. However, even if there are pharmacokinetic differences between females and males, significantly higher plasma concentrations in women have been demonstrated only for olanzapine and clozapine. To date, sex differences in adverse effects have not been well studied, but some adverse effects such as weight gain, hyperprolactinaemia and cardiac effects are reported to be particularly problematic for women. Most of the studies reviewed indicate that clozapine and olanzapine are associated with greater bodyweight gain than the other atypical antipsychotics, and that serious adverse effects such as metabolic syndrome, which includes increased visceral adiposity, hyperglycaemia, hypertension and dyslipidaemia induced by SGAs, are more frequent in females. According to most studies, the risk for cardiac adverse effects induced by SGAs is the same in male and female patients. Although women are at a lower risk of sudden cardiac death, they have a higher risk of induced long QT syndrome from antiarrhythmic and, probably, antipsychotic drugs. The propensity of sexual dysfunctions is higher with conventional antipsychotics than with SGAs. Additionally, there is some evidence that female sexual dysfunction is associated with high prolactin levels; however, whether the degree of prolactin level elevation is different between female and male patients remains controversial. There is no evidence for sex differences for any of the SGAs to cause a higher rate of extrapyramidal symptoms, acute dystonia or any other movement disturbance. Knowledge of the risks and benefits associated with the use of SGAs during pregnancy and lactation is limited, although the direction of dose adjustments during pregnancy depends on the drug and the enzyme that is responsible for its metabolism. In general, data on sex differences were mostly obtained by posthoc analysis and, therefore, the conclusions that can be drawn are limited. For a better understanding of the basic mechanisms of sex differences, future studies with a primary focus on this topic are required. Data that are more specific will help determine the extent to which these differences will have implications for clinical management.

Implication from randomized trials of rate and rhythm controls on management of patients with persistent atrial fibrillation

Recently, several randomized trials were published on the issue of rate or rhythm control for patients with atrial fibrillation (AF). Patients were typically minor symptomatic, relatively old, with age above 70, presenting with a recurrence of AF and suffering from only mild to moderate underlying heart disease. The main outcome of these trials is that rate control is not inferior to rhythm control for the management of patients with AF concerning morbidity and mortality. Also patients' quality of life did not differ significantly in follow-up in these trials. However, rhythm control is not redundant in the treatment of AF. Focus is now on subgroups of patients who could still have benefit being in sinus rhythm. For severely symptomatic patients, patients presenting with the first episode of AF and probably those with severe congestive heart failure, to restore and maintain sinus rhythm should still be the goal. With the failure of antiarrhythmic therapy, nonpharmacological approaches such as pulmonary vein isolation can be performed. Another finding of the randomized trials is that being in sinus rhythm does not prevent from the occurrence of thromboembolic complications. This means that for patients with AF, with risk factors for thromboembolic events, adequate anticoagulant therapy is indicated irrespective of the current heart rhythm. As with antiarrhythmic therapy, the search for new and safer anticoagulant therapy is underway. This review will focus on the key aspects we have learned from the randomized trials on rate and rhythm controls for patients with AF.

Sustained torsade de pointes occurring early during oral sotalol therapy for atrial fibrillation recurrence prophylaxis in a patient without heart disease

This report describes a 64 year-old female patient admitted to our department for recurrent and symptomatic episodes of atrial fibrillation. Antiarrhythmic therapy with sotalol at 240 mg/day was started, and after 48 h the patient experienced several episodes of sustained torsade de pointes, dramatic marked QT interval prolongation and negative T wave, in absence of overt cardiac disease, renal failure, electrolyte abnormalities or baseline QT interval prolongation. This case emphasizes the importance of hospitalization at the starting of sotalol therapy, especially in female patients, even in absence of predisposing factors for drug-induced tachyarrhythmias.

Female-specific aspects in the pharmacotherapy of chronic cardiovascular diseases

Differences in pharmacokinetics, pharmacodynamics, and physiology contribute to the phenomenon that women and men frequently respond differently to cardiovascular drugs. Hormonal influences, in addition, can play an important role: for example, the menstrual cycle, menopause, and pregnancy--as a result of fluctuations in concentrations of sexual steroids, and of changes in total body water--can be associated with gender-specific differences in the plasma levels of cardiovascular drugs. Clinical relevance accordingly results, especially for substances with a narrow therapeutic margin. This review treats the most important pharmacodynamic gender-relevant differences in this context, and surveys available evidence on the benefits of therapy of chronic cardiovascular diseases in women. On the whole, the study situation for women is appreciably less favourable than for men: owing to the fact that women are under-represented in most studies, and that few gender-specific analyses have been conducted.

Recent advances in understanding sex differences in cardiac repolarization

A number of gender differences exist in the human electrocardiogram (ECG): the P-wave and P-R intervals are slightly longer in men than in women, whilst women have higher resting heart rates than do men, but a longer rate-corrected QT (QT(C)) interval. Women with the LQT1 and LQT2 variants of congenital long-QT syndrome (LQTS) are at greater risk of adverse cardiac events. Similarly, many drugs associated with acquired LQTS have a greater risk of inducing torsades de pointes (TdP) arrhythmia in women than in men. There are also male:female differences in Brugada syndrome, early repolarisation syndrome and sudden cardiac death. The differences in the ECG between men and women, and in particular those relating to the QT interval, have been explored experimentally and provide evidence of differences in the processes underlying ventricular repolarization. The data available from rabbit, canine, rat, mouse and guinea pig models are reviewed and highlight involvement of male:female differences in Ca and K currents, although the possible involvement of rapid and persistent Na current and Na-Ca exchange currents cannot yet be excluded. The mechanisms underlying observed differences remain to be elucidated fully, but are likely to involve the influence of gonadal steroids. With respect to the QT interval and risk of TdP, a range of evidence implicates a protective role of testosterone in male hearts, possibly by both genomic and non-genomic pathways. Evidence regarding oestrogen and progesterone is less unequivocal, although the interplay between these two hormones may influence both repolarization and pro-arrhythmic risk.

Antiarrhythmic drugs in patients with implantable cardioverter-defibrillators

Antiarrhythmic drugs need to be initiated in up to 70% of patients with implantable cardioverter-defibrillators (ICDs) in order to treat atrial tachyarrhythmias, decrease the frequency of defibrillator shocks, and terminate ventricular arrhythmias along with antitachycardia pacing. trial fibrillation (AF) occurs in about 20% of patients with ICDs (the majority with congestive heart failure [CHF]). Antiarrhythmic drugs are initiated for this indication in 2-20% of the ICD population. Data from CHF-STAT (Congestive Heart Failure: Survival Trial of Antiarrhythmic Therapy; amiodarone vs placebo) and DIAMOND-AF (Danish Investigations of Arrhythmia and Mortality ON Dofetilide--rial Fibrillation; dofetilide vs placebo) support the approach that restoration and maintenance of sinus rhythm might be beneficial in CHF, even though no study has specifically addressed the CHF population with ICDs. Further clarification on potential benefits of rhythm control in CHF-associated AF will come from the AF-CHF (Atrial Fibrillation and Congestive Heart Failure) trial that is currently underway. The vast majority of patients with ICDs will have discharges of their devices during follow-up. Although class III antiarrhythmic drugs are widely considered to be effective for prophylaxis against frequent shocks, there are surprisingly few controlled studies that demonstrate this. In contrast to conflicting amiodarone data, sotalol has been found to be effective in preventing shocks from ICDs in prospective, randomized, placebo-controlled studies. A large study (SHIELD; SHock Inhibition Evaluation with azimiLiDe) has shown that azimilide significantly reduces ventricular tachyarrhythmia recurrence, thereby reducing the burden of symptomatic ventricular tachyarrhythmia. Other novel antiarrhythmic drugs, such as dofetilide or dronedarone, as well as different strategies (e.g. in the OPTIC [Optimal Pharmacological Therapy in Implantable Cardioverter] trial; beta-adrenoceptor antagonist therapy alone, amiodarone plus beta-adrenoceptor antagonist therapy, or sotalol alone) for the prevention of ICD shocks are under evaluation. The majority of antiarrhythmic drugs, including sotalol, dofetilide, and azimilide, have no effect on, or are even associated with a decrease in, defibrillation thresholds in humans. Amiodarone, in contrast, has been shown to be related to higher defibrillation thresholds at implant and during follow-up of monophasic devices. Potential cardiac (e.g. ventricular proarrhythmia, negative inotropic effect) and drug-specific non-cardiac adverse effects are a frequent cause for drug discontinuation and need to be considered when initiating and maintaining antiarrhythmic drug therapy. In conclusion, antiarrhythmic drugs are frequently used in ICD patients, the main indications being treatment of atrial tachyarrhythmias and prevention of ICD shocks. Despite potential adverse effects, antiarrhythmics can be administered safely, as long as ICD/drug interactions are appreciated. Controlled studies that will further define the role of concomitant antiarrhythmic drug utilization in patients with ICDs are underway.

Long QT syndrome. Why does sex matter?

There is increased awareness of the extent to which cardiac function is influenced by gender. One of the most dramatic and potentially lethal differences is that seen in cardiac repolarization reflected in the QT interval of the surface ECG. Gender differences in QT and QTc intervals have been observed to change during the lifetime in the general population. These differences can be explained to a large extent by sex hormone driven differences in gene expression of myocardial ion channels. Numerous studies have shown that women's risk to suffer arrhythmias in the context of QT prolonging drugs is doubled compared to men. For familial long QT syndrome there is no conclusive evidence for gender effects with respect to disease onset or mortality. Only subgroup analysis by genotype demonstrated a higher risk in female patients carrying mutations in the LQT2 locus. Special attention should be given to drug-induced QT prolongation in women.

Medical therapy for sudden death

Drug therapy can reduce the incidence of sudden death in many subgroups of patients. Patients who have long QT syndrome, in particular, benefit significantly from the use of beta-blockers and other antiarrhythmic agents. Although less useful, drug therapy has an important adjunctive role in patients who have conditions, such as hypertrophic cardiomyopathy and congestive heart failure. Proarrhythmia, which is a potentially dangerous side effect of drug therapy, needs to be watched for with special care in this group of high-risk patients.

Antiarrhythmic drug therapy of atrial fibrillation

In the post-AFFIRM era, treatment of AF has become the treatment of symptoms. In some patients, this will be simple rate control, but there remain a significant cohort of patients in whom rate control alone does not give acceptable symptom relief. In this group, antiarrhythmic therapy still has a role, and the AFFIRM trial indicates that this therapeutic strategy is without significant deleterious effect on mortality. The choice of antiarrhythmic agent must be individualized according to underlying cardiac pathologies and comorbidities, however. Most recently, the introduction of dofetilide has widened the therapeutic options in patients with severe heart disease, and the Canadian Trial of Atrial Fibrillation indicated the superior efficacy of amiodarone at low doses. The release/ development of newer Class III antiarrhythmic agents may offer hope for the benefits of amiodarone without the serious adverse effects with long-term therapy.

Atrial Fibrillation

Atrial fibrillation is the most common clinically significant dysrhythmia. It has great impact on quality of life especially related to complications such as stroke and heart failure as well as functional status and the cost of chronic treatment. Pharmacologic treatment strategies are now better defined and more efficacious. Side effects of drugs are better understood. Recent clinical studies have contributed recommended treatment guidelines. The identification of atrial ectopic foci in cardiac venous sites has defined targets for isolation ablations. Novel catheter ablation techniques are offering improved prognosis for patients with atrial fibrillation.