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Dronedarone is a new multichannel blocking antiarrhythmic drug for treatment of atrial fibrillation (AF). In patients with recently decompensated congestive heart failure (CHF) and depressed LV function, the drug was associated with excess mortality compared with a placebo group. The present study aimed to analyse in detail the effects of dronedarone on mortality and morbidity in AF patients CHF.
We performed a post hoc analysis of ATHENA, a large placebo-controlled outcome trial in 4628 patients with paroxysmal or persistent AF, to evaluate the relationship between clinical outcomes and dronedarone therapy in patients with stable CHF. The primary outcome was time to first cardiovascular (CV) hospitalization or death. There were 209 patients with NYHA class II/III CHF and a left ventricular ejection fraction ≤0.40 at baseline (114 placebo, 95 dronedarone patients). A primary outcome event occurred in 59/114 placebo patients compared with 42/95 dronedarone patients [hazard ratio (HR) 0.78, 95% CI = 0.52–1.16]. Twenty of 114 placebo patients and 12/95 dronedarone patients died during the study (HR 0.71, 95% CI = 0.34–1.44). Fifty-four placebo and 42 dronedarone patients were hospitalized for an intermittent episode of NYHA class IV CHF (HR = 0.78, 95% CI = 0.52–1.17).
In this post-hoc analysis of ATHENA patients with AF and stable CHF, dronedarone did not increase mortality and showed a reduction of CV hospitalization or death similar to the overall population. However, in the light of the ANtiarrhythmic trial with DROnedarone in Moderate to severe CHF Evaluating morbidity DecreAse study, dronedarone should be contraindicated in patients with NYHA class IV or unstable NYHA classes II and III CHF.
Dronedarone is a new multichannel blocking antiarrhythmic drug for the treatment of patients with atrial fibrillation (AF). Two large randomized placebo-controlled trials have demonstrated the rhythm-controlling efficacy of the compound.1 In addition, dronedarone has been shown to have rate-controlling properties in patients with permanent AF.2 In ATHENA [A placebo-controlled, double-blind, parallel arm trial to assess the efficacy of dronedarone 400 mg bid for the prevention of cardiovascular (CV) hospitalization or death from any cause in patients with AF/atrial flutter (AFL)], a large outcome trial in 4628 patients, dronedarone reduced major clinical outcomes in patients with AF including CV hospitalizations, CV mortality, and stroke.3 However, the ANDROMEDA [ANtiarrhythmic trial with DROnedarone in Moderate to severe congestive heart failure (CHF) Evaluating morbidity DecreAse] study in patients with recently decompensated heart failure and depressed left ventricular function was stopped prematurely due to excess mortality in the dronedarone arm relative to the placebo group.4 The reasons for the observed excess mortality have not been fully elucidated.
In order to investigate in more detail the effects of dronedarone in AF patients with stable CHF, we performed an exploratory analysis of ATHENA to evaluate the relationship between clinical outcomes and dronedarone therapy in this important subpopulation of patients.
The design and the primary results of the ATHENA trial have been previously published.3,5 In short, patients with paroxysmal or persistent AF and at least one additional risk factor for CV events including age ≥75 years or <75 years with one or more of the following risk factors: hypertension, diabetes mellitus, prior stroke or TIA, left atrial enlargement (≥50 mmHg), or depressed left ventricular ejection fraction (LVEF) (≤0.40) were eligible. They were randomized to receive dronedarone 400 mg bid or matching placebo. Main exclusion criteria were unstable haemodynamic condition, such as CHF of NYHA functional class IV within 4 weeks, and presence of permanent AF. The follow-up visit schedule included clinical evaluations at days 7 and 14 and at months 1, 3, 6, 9, 12 and every 3 months thereafter. In the case of clinical deterioration, patients were seen as indicated clinically. At each visit, a physical examination was performed and a 12-lead electrocardiogram (ECG) was recorded at each visit up to 6 months and every 6 months thereafter.
The primary outcome measure was time to first CV hospitalization or death [hazard ratio (HR) = 0.76, 95% CI = 0.69–0.84, P < 0.001].3 Pre-specified secondary outcome measures were total mortality (HR = 0.84, 95% CI = 0.66–1.08, P = 0.18), CV mortality (HR = 0.71, 95% CI = 0.51–0.98, P = 0.03), and CV hospitalization (HR = 0.74, 95% CI = 0.67–0.82, P < 0.001).3 Deaths were categorized by a blinded Adjudication Committee into four categories: cardiac arrhythmic; cardiac non-arrhythmic; vascular non-cardiac; and non-vascular. Information on the occurrence of new or worsened CHF was gathered from hospitalization and death reports which included specific information on the occurrence of CHF.
Analyses were performed on the intention-to-treat population. The time to event was estimated according to the non-parametric Kaplan–Meier method and compared by a two-sided log-rank's asymptotic test. Hazard ratio was calculated using Cox's proportional hazard model with treatment group as covariate. Interactions between several subgroups were tested using a likelihood ratio test. All P-values were two-tailed and threshold used for significance was 0.05. Statistical analyses were done using SAS version 8.2 on UNIX environment.
A total of 4628 patients were enrolled in ATHENA with 2301 assigned to dronedarone and 2327 to placebo. Overall, there was no significant interaction between the treatment effects of dronedarone and the presence or absence of a history of CHF or impaired left ventricular function (Table 1).
A total of 209 patients with stable CHF NYHA functional class II or III in the setting of a documented LVEF ≤0.40 were enrolled in ATHENA. Of these, 114 were assigned to receive placebo and 95 to receive dronedarone. Compared with the overall patient population, these patients had more often coronary artery disease, ischaemic or non-ischaemic cardiomyopathy, and were more often having a permanent pacemaker or an implanted defibrillator (Table 2). As summarized in Figures 1 and 22 and Table 3, the results for all outcome measures in this patient population were consistent with those observed in the overall population, with fewer events in the dronedarone compared with the placebo group. Furthermore, in this subgroup, outcomes were not related to impairment in renal function. The HR for dronedarone in terms of all-cause mortality was 0.71 (95% CI = 0.33–1.55) for patients with a creatinine clearance (determined by the Cockcroft Gault formula) of <65 mL/min and 0.75 (95% CI = 0.13–4.51) for those with a clearance of ≥65 mL/min (P-value for interaction 0.98).
Treatment-emergent adverse events (adverse events occurring between first study drug intake and last study drug intake + 10 days) occurred in 90 of 114 placebo patients (78.9.2%) and in 65 of 95 dronedarone patients (58.4%). Serious treatment-emergent adverse events occurred in 28.1% of placebo patients and in 16.8% of dronedarone patients. The most frequent adverse events were infections and gastrointestinal disorders that occurred at similar rates in the dronedarone group. The overall adverse event profile was similar to the overall patient population with bradycardia (placebo 0.9% and dronedarone 3.2%), QT-interval prolongation (placebo 2.6% and dronedarone 4.2%), creatinine increase (placebo 2.6% and dronedarone 10.5%), nausea (placebo 4.4% and dronedarone 8.4%), diarrhea (placebo 9.6% and dronedarone 14.7%), and rash (placebo 0% and dronedarone 3.2%). Fourteen patients in the placebo group (12.3%) and 18 dronedarone patients (18.9%) permanently discontinued study drug due to adverse events. The dronedarone-mediated increase in serum creatinine was similar to the overall ATHENA population (Figure 3).
In ATHENA, an analysis of time to first hospitalization for heart failure included 132 events in the placebo group vs. 112 events in the dronedarone group (HR = 0.85, 95% CI = 0.66–1.10).3 When patients were further followed after this hospitalization, 12 patients died in the dronedarone group compared with 26 in the placebo group.
A further analysis concerned those patients who developed an episode of NYHA functional class IV CHF during the course of the study. Fifty-four placebo and 42 dronedarone patients were hospitalized while in CHF class IV (HR = 0.78, 95% CI = 0.52–1.17). The median time from randomization to hospitalization with NYHA class IV CHF was 227 days in the placebo arm and 228 days in the dronedarone arm, respectively. Patients with NYHA class IV CHF episodes were older, had more structural heart disease (notably coronary disease and ischaemic cardiomyopathy), and less lone AF compared with patients without such episodes. When patients were further followed after in-hospital resolution of CHF, 15 placebo patients and 10 dronedarone patients died.
The present exploratory analysis of ATHENA demonstrates a lack of excess mortality or morbidity in AF patients with stable CHF treated with dronedarone. In fact, consistent with the results of the main trial,3 therapy with dronedarone was associated with a decrease in the primary study outcome in patients with NYHA functional class III CHF at baseline. Similarly, in patients with NYHA class II/III CHF and a LVEF ≤0.40, representing the subpopulation with systolic heart failure, event rates were not different in the dronedarone and the placebo groups.
Most antiarrhythmic drugs are not recommended for the treatment of AF in the setting of CHF and/or depressed LV function because these patients are particularly prone to ventricular proarrhythmic effects and to negative inotropic action of antiarrhythmic drugs. Current guidelines for the treatment of AF recommend only the use of amiodarone or dofetilide in heart failure patients with AF.6 Whereas amiodarone is well tolerated in patients with impaired LV function7 and has very little proarrhythmic side effects,8 its use is hampered by the extracardiac side effects that can be serious and necessitate discontinuation in a significant proportion of patients. Dofetilide, on the other hand, carries a significant proarrhythmic potential9 which is why the drug has to be initiated in-hospital with ECG monitoring for at least a few days. For this reason dofetilide is not marketed in all countries. The lack of safe and efficacious pharmacological treatment options for AF in the setting of CHF warrants careful evaluation of new antiarrhythmic compounds.
A previous study in CHF patients using dronedarone, ANDROMEDA, was terminated prematurely due to the observation of increased mortality with dronedarone.4 ANDROMEDA enrolled patients with advanced CHF characterized by LVEF ≤ 0.35 and, importantly, a recent hospitalization with new or worsening heart failure. There were 627 patients enrolled and followed for a median of 2 months. Thirteen excess deaths occurred on dronedarone (HR = 2.13, 95% CI = 1.07–2.45, P = 0.03). The excess mortality was predominantly related to CHF (10 deaths vs. 2). This finding contrasts the results of ATHENA where dronedarone reduced CV mortality.3 Specifically, ATHENA demonstrated in 4628 patients with AF at moderate to high risk for CV events that dronedarone therapy was not associated with increased mortality due to pump failure (HR = 0.95, 95% CI = 0.41–1.85, P = 0.89) or with an increase in hospitalizations for CHF (HR = 0.86, 95% CI = 0.67–1.10, P = 0.22).3 The present analysis extends these observations and yields results for the population with stable class II/III CHF in the setting of reduced LVEF. All findings are consistent with the overall observations made in ATHENA. Even in these high-risk subsets, there was no sign of harm associated with dronedarone therapy.
How can we understand the difference between ATHENA and ANDROMEDA? There were 356 NYHA class III patients in ANDROMEDA4 compared with 200 such patients in ATHENA. On the other hand, ATHENA included 80 times more patient years of exposure to dronedarone than ANDROMEDA. The presence or absence of clinical stability was the primary feature that distinguished patients enrolled in the ANDROMEDA and ATHENA trials. Specifically, the ANDROMEDA trial was conceptualized primarily as a study that sought to enrol clinically unstable patients with advanced heart disease; as such, this trial enrolled patients who might be most likely to demonstrate a proarrhythmic effect of dronedarone (if one existed). In contrast, the ATHENA trial was conceptualized primarily as an efficacy study and sought to enrol patients likely to receive the drug in clinical practice, i.e. those with recent or current AF/AFL. Although most of the patients in the ATHENA trial had structural heart disease, they were clinically stable. Both trials enrolled patients with low ejection fractions or with NYHA class II or III heart failure; however, these patients had been hospitalized for worsening heart failure in the ANDROMEDA trial but were stable outpatients in the ATHENA trial. The observation of a higher mortality rate in ANDROMEDA is in line with a recent analysis of a large heart failure trial.10 Solomon et al. elucidated the subsequent risk of death associated with a heart failure admission (which all patients enrolled in ANDROMEDA were required to have). They found that the mortality rate was highest early after a heart failure hospitalization and declined thereafter but never reached the relative risk obtained in patients without a heart failure hospitalization.10 These data suggest that patients with CHF are most vulnerable in the immediate aftermath of a hospital admission and should therefore not receive dronedarone during this period.
Both ANDROMEDA and ATHENA observed an increase in serum creatinine in patients receiving dronedarone. It is possible that investigators observing a creatinine increase in ANDROMEDA due to dronedarone inappropriately discontinued angiotensin-converting enzyme inhibitor therapy which might have resulted in worsening of CHF. Therefore, ATHENA investigators were informed that a small rise in creatinine due to a specific partial inhibition of tubular organic cation transporters11 was expected with dronedarone not indicating a decline in renal function.
Exploratory efficacy analyses comprising relatively small subgroups have inherent limitations that result from the loss of a randomization effect. We also acknowledge the fact that the interaction analyses may be underpowered given the small patient numbers in some of the subgroups. However, the consistency of our analyses suggests that our findings are robust.
While patients with unstable haemodynamic conditions were excluded from ATHENA, patients with stable CHF at baseline showed results that were consistent with those observed in the overall ATHENA population. In patients with AF and stable CHF, dronedarone did not increase mortality and showed a trend towards the reduction of CV hospitalization or death. There was no increase in CHF hospitalizations in the dronedarone arm. According to the ANDROMEDA study, however, dronedarone is contraindicated in patients with NYHA class IV heart failure or unstable NYHA classes II and III heart failure with a recent decompensation requiring hospitalization or referral to a specialized heart failure clinic.
Funding to pay the Open Access publication charges for this article was provided by sanofi-aventis.
Conflicts of interest: S.H.H reports receiving consulting fees from Sanofi Aventis, Cardiome, ARYx, BMS, research grants from Sanofi Aventis and St. Jude Medical, and lecture fees from Sanofi Aventis, St. Jude Medical, and BMS; H.J.G.M.C., consulting fees from Medacorp, Astra Zeneca, Sanofi Aventis, Cardiome, research grants from Astra Zeneca and St. Jude Medical, and lecture fees from Astra Zeneca, Sanofi Aventis, and Chugai Pharmaceuticals; R.L.P., consulting fees from Sanofi Aventis, Astellas, and Pfizer; C.T.-P., consulting fees from Sanofi Aventis and Cardiome, research grants from Sanofi Aventis, lecture fees from Sanofi Aventis and Cardiome; S.J.C., consulting fees and research grants from Sanofi Aventis. M.E. and C.G. are employees of Sanofi Aventis and own Sanofi Aventis shares.
The trial is registered under ClinicalTrials.gov #NCT 00174785. The trial was sponsored by Sanofi Aventis, Paris, France.