Management of atrial tachyarrhythmias in the critically ill: a comparison of intravenous procainamide and amiodarone

Pharmacological and non-pharmacological treatments and outcomes for new-onset atrial fibrillation in ICU patients: the CAFE scoping review and database analyses

BACKGROUND

New-onset atrial fibrillation occurs in around 10% of adults treated in an intensive care unit. New-onset atrial fibrillation may lead to cardiovascular instability and thromboembolism, and has been independently associated with increased length of hospital stay and mortality. The long-term consequences are unclear. Current practice guidance is based on patients outside the intensive care unit; however, new-onset atrial fibrillation that develops while in an intensive care unit differs in its causes and the risks and clinical effectiveness of treatments. The lack of evidence on new-onset atrial fibrillation treatment or long-term outcomes in intensive care units means that practice varies. Identifying optimal treatment strategies and defining long-term outcomes are critical to improving care.

OBJECTIVES

In patients treated in an intensive care unit, the objectives were to (1) evaluate existing evidence for the clinical effectiveness and safety of pharmacological and non-pharmacological new-onset atrial fibrillation treatments, (2) compare the use and clinical effectiveness of pharmacological and non-pharmacological new-onset atrial fibrillation treatments, and (3) determine outcomes associated with new-onset atrial fibrillation.

METHODS

We undertook a scoping review that included studies of interventions for treatment or prevention of new-onset atrial fibrillation involving adults in general intensive care units. To investigate the long-term outcomes associated with new-onset atrial fibrillation, we carried out a retrospective cohort study using English national intensive care audit data linked to national hospital episode and outcome data. To analyse the clinical effectiveness of different new-onset atrial fibrillation treatments, we undertook a retrospective cohort study of two large intensive care unit databases in the USA and the UK.

RESULTS

Existing evidence was generally of low quality, with limited data suggesting that beta-blockers might be more effective than amiodarone for converting new-onset atrial fibrillation to sinus rhythm and for reducing mortality. Using linked audit data, we showed that patients developing new-onset atrial fibrillation have more comorbidities than those who do not. After controlling for these differences, patients with new-onset atrial fibrillation had substantially higher mortality in hospital and during the first 90 days after discharge (adjusted odds ratio 2.32, 95% confidence interval 2.16 to 2.48; adjusted hazard ratio 1.46, 95% confidence interval 1.26 to 1.70, respectively), and higher rates of subsequent hospitalisation with atrial fibrillation, stroke and heart failure (adjusted cause-specific hazard ratio 5.86, 95% confidence interval 5.33 to 6.44; adjusted cause-specific hazard ratio 1.47, 95% confidence interval 1.12 to 1.93; and adjusted cause-specific hazard ratio 1.28, 95% confidence interval 1.14 to 1.44, respectively), than patients who did not have new-onset atrial fibrillation. From intensive care unit data, we found that new-onset atrial fibrillation occurred in 952 out of 8367 (11.4%) UK and 1065 out of 18,559 (5.7%) US intensive care unit patients in our study. The median time to onset of new-onset atrial fibrillation in patients who received treatment was 40 hours, with a median duration of 14.4 hours. The clinical characteristics of patients developing new-onset atrial fibrillation were similar in both databases. New-onset atrial fibrillation was associated with significant average reductions in systolic blood pressure of 5 mmHg, despite significant increases in vasoactive medication (vasoactive-inotropic score increase of 2.3; p < 0.001). After adjustment, intravenous beta-blockers were not more effective than amiodarone in achieving rate control (adjusted hazard ratio 1.14, 95% confidence interval 0.91 to 1.44) or rhythm control (adjusted hazard ratio 0.86, 95% confidence interval 0.67 to 1.11). Digoxin therapy was associated with a lower probability of achieving rate control (adjusted hazard ratio 0.52, 95% confidence interval 0.32 to 0.86) and calcium channel blocker therapy was associated with a lower probability of achieving rhythm control (adjusted hazard ratio 0.56, 95% confidence interval 0.39 to 0.79) than amiodarone. Findings were consistent across both the combined and the individual database analyses.

CONCLUSIONS

Existing evidence for new-onset atrial fibrillation management in intensive care unit patients is limited. New-onset atrial fibrillation in these patients is common and is associated with significant short- and long-term complications. Beta-blockers and amiodarone appear to be similarly effective in achieving cardiovascular control, but digoxin and calcium channel blockers appear to be inferior.

FUTURE WORK

Our findings suggest that a randomised controlled trial of amiodarone and beta-blockers for management of new-onset atrial fibrillation in critically ill patients should be undertaken. Studies should also be undertaken to provide evidence for or against anticoagulation for patients who develop new-onset atrial fibrillation in intensive care units. Finally, given that readmission with heart failure and thromboembolism increases following an episode of new-onset atrial fibrillation while in an intensive care unit, a prospective cohort study to demonstrate the incidence of atrial fibrillation and/or left ventricular dysfunction at hospital discharge and at 3 months following the development of new-onset atrial fibrillation should be undertaken.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN13252515.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 71. See the NIHR Journals Library website for further project information.

Rhythm-control therapy for new-onset atrial fibrillation in critically ill patients: A post hoc analysis from the prospective multicenter observational AFTER-ICU study

BACKGROUND

Sustained new-onset atrial fibrillation (AF) in the intensive care unit has been reported to be associated with poor outcomes. However, in critical illness, whether rhythm-control therapy can achieve sinus rhythm (SR) restoration is unknown. This study aimed to assess the impact of rhythm-control therapy on SR restoration for new-onset AF in critically ill patients.

METHODS

This post-hoc analysis of a prospective multicenter observational study involving 32 Japan intensive care units compared patients with and without rhythm-control therapy for new-onset atrial fibrillation (AF) and conducted a multivariable analysis using Cox proportional hazards regression analysis including rhythm-control therapy as a time-varying covariate for SR restoration.

RESULTS

Of 423 new-onset AF patients, 178 patients (42%) underwent rhythm-control therapy. Among those patients, 131 (31%) underwent rhythm-control therapy within 6 h after AF onset. Magnesium sulphate was the most frequently used rhythm-control drug. The Cox proportional hazards model for SR restoration showed that rhythm-control therapy had a significant positive association with SR restoration (adjusted hazard ratio: 1.46; 95% confidence interval: 1.16-1.85). However, the rhythm-control group had numerically higher hospital mortality than the non-rhythm-control group (31% vs. 23%, p = 0.09).

CONCLUSIONS

Rhythm-control therapy for new-onset AF in critically ill patients was associated with SR restoration. However, patients with rhythm-control therapy had poorer prognosis, possibly due to selection bias. These findings may provide important insight for the design and feasibility of interventional studies assessing rhythm-control therapy in new-onset AF.

Variable use of amiodarone is associated with a greater risk of recurrence of atrial fibrillation in the critically ill

Background

Atrial fibrillation is a common rhythm disturbance in the general medical-surgical intensive care unit. Amiodarone is a popular drug in this setting but evidence to inform clinical practice remains scarce. We aimed to identify whether variation in the clinical use of amiodarone was associated with recurrent atrial fibrillation.

Methods

This was a retrospective audit of 177 critically ill patients who developed new-onset atrial fibrillation after admission to a tertiary level medical-surgical trauma intensive care unit. Patterns of amiodarone prescription (including dosage schedule and duration) were assessed in relation to recurrence of atrial fibrillation during the intensive care unit stay. Known recurrence risk factors, such as inotrope administration, cardiac disease indices, Charlson Comorbidity Index, magnesium concentrations, fluid balance, and potassium concentrations, were also included in adjusted analysis using forward stepwise logistic regression modelling.

Results

The cohort had a median (interquartile range) age of 69 years (60–75), Acute Physiology and Chronic Health Evalution II score of 22 (17–28) and Charlson Comorbidity Index of 2 (1–4). A bolus dose of amiodarone followed by infusion (P = 0.02), in addition to continuing amiodarone infusion through to discharge from the intensive care unit (P < 0.001), were associated with less recurrent dysrhythmia. Recurrence after successful treatment was associated with ceasing amiodarone while an inotrope infusion continued (P < 0.001), and was more common in patients with a prior history of congestive cardiac failure (P = 0.04), and a diagnosis of systemic inflammatory response syndrome (P = 0.02).

Conclusions

Amiodarone should be administered as a bolus dose followed immediately with an infusion when treating atrial fibrillation in the medical-surgical intensive care unit. Consideration should be given to continuing amiodarone infusions in patients on inotropes until they are ceased.

Cardiovascular collapse during amiodarone infusion in a hemodynamically compromised child with refractory supraventricular tachycardia

We describe a 7-week-old female infant who presented with refractory supraventricular tachycardia (SVT). During amiodarone infusion, she developed hypotension and cardiac arrest requiring extracorporeal membrane oxygenation (ECMO) support. After successful control of SVT using procainamide infusion, she was weaned from ECMO and discharged home on oral flecainide. We conclude that infants with acidosis, ventricular dysfunction, and prolonged refractory SVT may poorly tolerate intravenous amiodarone.

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.

A formula for the stratified selection of patients with paroxysmal atrial fibrillation in the emergency setting: a retrospective pilot study

BACKGROUND

Amiodarone is a commonly used medication in the treatment of atrial fibrillation (AF) of recent onset.

STUDY OBJECTIVES

The aim of the study was to identify a possible formula for selecting Emergency Department (ED) patients with paroxysmal AF who will spontaneously restore sinus rhythm (SR), successfully restore SR with the use of loading intravenous (i.v.) amiodarone, or require 24-h maintenance amiodarone infusion.

METHODS

This retrospective pilot study included 141 patients with recent-onset AF. Patients who did not restore SR spontaneously received i.v. amiodarone (5 mg/kg) within a period of 30 min. In case of no response, an additional dosage of 1000 mg of i.v. amiodarone was administered over a period of 24 h. Binary logistic regression models were used to determine the predictors of spontaneous conversion and the response to amiodarone administration.

RESULTS

The formula ([heart rate/systolic blood pressure] + 0.1 × number of past AF incidences) was chosen as the one with the highest combined sensitivity and specificity. This index identified the patients who spontaneously restored SR (cutoff point 1.31 with 78.6% sensitivity and 77.9% specificity), whereas for patients who responded to the loading i.v. amiodarone dose, the use of the index (cutoff point 1.24) exhibited 84.1% sensitivity and 75.3% specificity.

CONCLUSIONS

This formula may be a useful and reliable bedside diagnostic tool to identify AF patients most likely to spontaneously convert, or respond to loading amiodarone administration in the emergency setting. The use of this index also can assist in patient risk stratification.

Treatment of new-onset atrial fibrillation in noncardiac intensive care unit patients: a systematic review of randomized controlled trials

OBJECTIVE

Atrial fibrillation is a common problem associated with morbidity and mortality in critically ill patients; however, evidence-based treatment recommendations are lacking. The objective of this systematic review was to evaluate the efficacy of pharmacologic rhythm control of new-onset atrial fibrillation in noncardiac, critically ill adults.

DATA SOURCE

Citations identified from an electronic search of Medline, the Cochrane register of controlled trials, and Embase databases (1966 to August 2006) were independently reviewed by two investigators.

STUDY SELECTION

All prospective randomized controlled trials evaluating pharmacologic rhythm conversion regimens for new-onset atrial fibrillation in (noncardiac surgery) critically ill adult patients were included. The primary end point was atrial fibrillation resolution.

DATA EXTRACTION

Using a standardized data extraction form, data related to study design, population characteristics, pharmacologic intervention, and outcome measures were collected.

DATA SYNTHESIS

Four trials met inclusion criteria from 1995 citations screened. Of the 143 evaluable patients in these trials 89 (76%) had atrial fibrillation while the remaining ones had other atrial tachyarrhythmias. Drugs evaluated for rhythm conversion included amiodarone (n = 26), procainamide (n = 14), magnesium (n = 18), flecainide (n = 15), esmolol (n = 28), verapamil (n = 15), and diltiazem (n = 27). The definition of treatment success ranged from conversion within 1 hr to conversion within 24 hrs. No study evaluated maintenance of conversion, and one study included hemodynamically unstable patients. Lack of methodologic homogeneity prevented any pooled analysis.

CONCLUSIONS

Using the current published literature, we cannot recommend a standard treatment for atrial fibrillation in noncardiac critically ill adult patients. Clinical trials evaluating rhythm conversion in critically ill populations outside of cardiac surgery are lacking. Further trials that address goals of care in hemodynamically stable and unstable patients and utilize standardized definitions of successful cardioversion are required.

Clinical review: treatment of new-onset atrial fibrillation in medical intensive care patients--a clinical framework

Atrial fibrillation occurs frequently in medical intensive care unit patients. Most intensivists tend to treat this rhythm disorder because they believe it is detrimental. Whether atrial fibrillation contributes to morbidity and/or mortality and whether atrial fibrillation is an epiphenomenon of severe disease, however, are not clear. As a consequence, it is unknown whether treatment of the arrhythmia affects the outcome. Furthermore, if treatment is deemed necessary, it is not known what the best treatment is. We developed a treatment protocol by searching for the best evidence. Because studies in medical intensive care unit patients are scarce, the evidence comes mainly from extrapolation of data derived from other patient groups. We propose a treatment strategy with magnesium infusion followed by amiodarone in case of failure. Although this strategy seems to be effective in both rhythm control and rate control, the mortality remained high. A randomised controlled trial in medical intensive care unit patients with placebo treatment in the control arm is therefore still defendable.

Intravenous and oral administration of amiodarone for the treatment of recent onset atrial fibrillation after digoxin administration

BACKGROUND

Atrial fibrillation (AF) remains a significant contributor to cardiovascular morbidity. Amiodarone is a potent antiarrhythmic drug. The safety and efficacy of oral versus intravenous (i.v.) Amiodarone in the treatment of AF of recent onset (duration <48 h) was investigated.

METHODS

The study population consisted of 223 patients with symptomatic AF, of whom 110 received 600 mg oral Amiodarone (Group A) in three divided doses and 113 received i.v. Amiodarone (5 mg/kg over 30 min followed by 1000 mg over the next 24 h) (Group B). Digoxin was administered to all patients, who had not previously received it. All patients were monitored for 24 h.

RESULTS

Conversion to sinus rhythm occurred in 85.45% of group A and 82.30% in group B (p=NS). Mean time of cardioversion in group A was 20+/-4.5 h and in group B was 12+/-8 h (p<0,001). However, blood pressure (BP) in group A remained stable for the observation period, whereas it fell significantly in group B. Treatment was not discontinued in any of the patients in either group, however 13 patients in group B developed superficial phlebitis.

CONCLUSIONS

Both forms of the drug are extremely efficient in restoring sinus rhythm in AF of recent onset, although the i.v. form acts quicker. The oral form of the drug does not alter significantly the patients' BP.

Effects of a high dose intravenous bolus amiodarone in patients with atrial fibrillation and a rapid ventricular rate

BACKGROUND

Amiodarone, given as intravenous bolus has not yet been studied in patients with atrial fibrillation and a high ventricular rate.

METHODS

One hundred consecutive patients with atrial fibrillation and a ventricular rate above 135 bpm were randomized to receive either 450 mg amiodarone or 0.6 mg digoxin given as a single bolus through a peripheral venous access. If the ventricular rate exceeded 100 bpm after 30 min, another 300 mg amiodarone or 0.4 mg digoxin were added. Primary endpoints of the study were the ventricular rate and the occurrence of sinus rhythm after 30 and 60 min. Secondary endpoints were blood pressure during the first hour after drug administration, and safety regarding drug induced hypotension, and phlebitis at the infusion site.

RESULTS

Baseline heart rate was 144+/-19 in the amiodarone group and 145+/-15 in the digoxin group (p=0.72). Following amiodarone, heart rate was 104+/-25 after 30 min compared to 116+/-23 in the digoxin group (p=0.02) and 94+/-22 versus 105+/-22 after 60 min (p=0.03). After 30 min, sinus rhythm was documented in 14 (28%) patients following amiodarone compared to 3 (6%) patients in the digoxin group (p=0.003), and after 60 min in 21 (42%) versus 9 (18%) patients (p=0.012). Asymptomatic hypotension was observed in 4 amiodarone treated patients, and superficial phlebitis in 1 patient.

CONCLUSIONS

Amiodarone, given as an intravenous bolus is relatively safe and more effective than digoxin for heart rate control and conversion to sinus rhythm in patients with atrial fibrillation and a rapid ventricular rate.

Intravenous Amiodarone for the Treatment of Atrial Fibrillation in the Nonsurgical Patient

Purpose: To review the literature to define the efficacy of intravenous (IV) amiodarone in the treatment of atrial fibrillation in the nonsurgical patient. Method: A MEDLINE search was conducted using the key words “intravenous amiodarone” and “atrial fibrillation.” All trials evaluating the use of intravenous amiodarone in the surgical setting were excluded. Results: Twenty articles were identified, which were divided into acute and chronic atrial fibrillation. Within the acute setting, IV amiodarone was used alone, compared to a placebo-control, or compared to active drug regimens. In the trials without a control group, it was difficult to determine how much of the effect was due to spontaneous conversion. When compared to placebo, IV amiodarone offered a 61% to 92% conversion at 24 hours. Compared to active drug therapy, there was a trend to increased efficacy at 24 hours. However, amiodarone was no more effective for the conversion of atrial fibrillation than alternative therapies. In the case of chronic atrial fibrillation, intravenous amiodarone had no benefit. The incidence of thrombophlebitis, bradycardia, and hypotension was quite high, reported to be around 15% to 30% in many of the trials. Conclusion: The use of intravenous amiodarone should not be recommended as the first line agent for the conversion of atrial fibrillation.

Meta-analysis of randomised controlled trials of the effectiveness of antiarrhythmic agents at promoting sinus rhythm in patients with atrial fibrillation

OBJECTIVE

To conduct a meta-analysis of randomised controlled trials to estimate the effectiveness of antiarrhythmic drugs at promoting sinus rhythm in patients with atrial fibrillation.

DESIGN

Articles were identified by using a comprehensive search of English language papers indexed in Medline from 1966 to August 2001. For the outcomes of sinus rhythm and death, a random effects model was used to model repeated assessments within a study at different time points.

SETTING

Emergency departments and ambulatory clinics.

PATIENTS

Patients with atrial fibrillation.

INTERVENTIONS

Antiarrhythmic agents grouped according to their Vaughan-Williams class.

MAIN OUTCOME MEASURES

Sinus rhythm and mortality.

RESULTS

91 articles met a priori criteria for inclusion in the analysis. Median duration of follow up was one day (range 0.04-1096, mean (SD) 46 (136) days). The median proportion of patients in sinus rhythm at follow up was 55% (range 0-100%) and 32% (range 0-90%) receiving active treatment and placebo, respectively. Median survival was 99% (range 55-100%) and 99% (range 55-100%). Compared with placebo, the following drug classes were associated with increased sinus rhythm at follow up: IA (treatment difference 21.5%, 95% confidence interval (CI) 16.3% to 26.8%); IC (treatment difference 33.1%, 95% CI 23.3% to 42.9%); and III (treatment difference 17.4%, 95% CI 11.5% to 23.3%). Class IC drugs were associated with increased sinus rhythm at follow up compared with class IV drugs (treatment difference 43.2%, 95% CI 11.5% to 75.0%). There was no significant difference in mortality between any drug classes.

CONCLUSIONS

Class IA, IC, and III drugs are associated with increased sinus rhythm at follow up compared with placebo. It is unclear whether any antiarrhythmic drug class is associated with increased or decreased mortality.

Conversion of recent-onset atrial fibrillation with intravenous amiodarone: a meta-analysis of randomized controlled trials

STUDY OBJECTIVE

To evaluate efficacy and safety of intravenous amiodarone for conversion of recent-onset atrial fibrillation.

DATA SOURCES

MEDLINE search of published, randomized, controlled trials assessing the efficacy and safety of intravenous amiodarone in recent-onset (< 7 days) atrial fibrillation, supplemented with searches of reference lists of identified articles and bibliographies of secondary and tertiary review articles.

STUDY SELECTION

The identified trials were eligible for meta-analysis if they met the following criteria: patients had recent-onset atrial fibrillation; patients were randomized to intravenous amiodarone, placebo, or another antiarrhythmic agent; no other antiarrhythmic agent except digoxin was administered simultaneously with intravenous amiodarone or other active treatments; the number and percentage of conversions to sinus rhythm after treatment began were reported; and the number and type of adverse drug reactions occurring after treatment began were reported.

RESULTS

Eighteen randomized controlled trials, including active control cohorts and placebo cohorts, met inclusion criteria. Atrial fibrillation was spontaneous in 13 trials, postoperative in 4, and combined spontaneous and postoperative in 1. A total of 550 patients received intravenous amiodarone, 451 received other antiarrhythmic therapy, and 202 received placebo. Unadjusted averages for cardioversion were as follows: intravenous amiodarone, 417 (76%) of 550 patients; other antiarrhythmics, 324 (72%) of 451 patients; and placebo, 121 (60%) of 202 patients. Pooled estimates of cardioversion for active cohort studies were 72.1% for intravenous amiodarone and 71.9% for other antiarrhythmics (p=0.84). Pooled estimates of cardioversion for placebo cohort studies were 82.4% for intravenous amiodarone and 59.7% for placebo (p=0.03). Unadjusted averages for adverse event rates were intravenous amiodarone, 94 (17%) of 550 patients; other antiarrhythmics, 63 (14%) of 451 patients; and placebo, 23 (11%) of 202 patients. Pooled estimates of adverse event rates for active cohort studies were 12.2% for intravenous amiodarone and 14.0% for other antiarrhythmics (p=0.64). Pooled estimates of adverse event rates for placebo cohort studies were 26.8% for intravenous amiodarone and 10.8% for placebo (p=0.02). The most common adverse drug reactions reported with intravenous amiodarone were infusion phlebitis, bradycardia, and hypotension.

CONCLUSION

The efficacy and safety profile of intravenous amiodarone is similar to that of other antiarrhythmics for cardioversion of recent-onset atrial fibrillation. Intravenous amiodarone is significantly more effective than placebo but is associated with significantly higher frequency of adverse events, although most were not considered to be dose limiting.

Pharmacologic conversion of atrial fibrillation: a systematic review of available evidence

This report reviews the efficacy of currently available antiarrhythmic agents for conversion of atrial fibrilation (AF) to normal sinus rhythm (NSR). A systematic search of literature in the English language was done on computerized databases, such as MEDLINE, EMBASE, and Current Contents, in reference lists, by manual searching, and in contact with expert informants. Published studies involving humans that described the use of antiarrhythmic therapy for conversion of AF to NSR were considered and only studies that examined the use of agents currently available in the United States were included. Studies exclusively describing antiarrhythmic therapy for conversion of postsurgical AF were excluded. The methodology and results of each trial were assessed and attempts were made to acquire additional information from investigators when needed. Assessment of methodological quality was incorporated into a levels-of-evidence scheme. Eighty-eight trials were included, of which 34 (39%) included a placebo group (level I data). We found in recent-onset AF of less than 7 days, intravenous (i.v.) procainamide, high-dose i.v. or high-dose combination i.v. and oral amiodarone, oral quinidine, oral flecainide, oral propafenone, and high-dose oral amiodarone are more effective than placebo for converting AF to NSR. In recent-onset AF of less than 90 days, i.v. ibutilide is more effective than placebo and i.v. procainamide. In chronic AF, oral dofetilide converts AF to NSR within 72 hours, and oral propafenone and amiodarone are effective after 30 days of therapy. We conclude than for conversion of recent-onset AF of less than 7 days, procainamide may be considered a preferred i.v. agent and propafenone a preferred oral agent. For conversion of recent-onset AF of longer duration (less than 90 days), i.v. ibutilide may be considered a preferred agent. For patients with chronic AF and left ventricular dysfunction, direct current cardioversion is the preferred conversion method. Larger, well-designed randomized controlled trials with clinically important endpoints in specific populations of AF patients are needed.

Termination of recent-onset atrial fibrillation/flutter in the emergency department: a sequential approach with intravenous ibutilide and external electrical cardioversion

Safety and effectiveness are the goals in treating patients with arrhythmias. In an open prospective study, we observed the efficacy and safety of up to 2 mg intravenous ibutilide, a new class III antiarrhythmic agent in haemodynamically stable patients presenting in the emergency department (ED) with symptoms of recent-onset (<48 h) atrial fibrillation/flutter. Arrhythmia termination within 90 min, haemodynamic parameters and proarrhythmic effects were assessed. Non-responders to the ibutilide infusion underwent external electrical cardioversion. We included 51 patients. In 31 patients therapeutic intervention with intravenous ibutilide was successful within 90 min (61%). In another seven patients conversion to sinus rhythm occurred after 90 min without any other intervention (14%). Blood pressure remained stable and no relevant proarrhythmic effects were observed. The 13 patients who did not respond to ibutilide treatment underwent successful external electrical cardioversion. The overall conversion rate was 100%. Forty-seven patients (92%) were discharged within a median of 9 h and managed as outpatients. In conclusion, in haemodynamically stable patients with recent-onset atrial fibrillation/flutter intravenous ibutilide and external electrical cardioversion for conversion to sinus rhythm turned out to be effective and safe. The short duration of admission makes this strategy attractive for use in the ED.

The Management of Atrial Fibrillation in the ICU

Atrial tachyarrhythmias are the most frequent arrhythmias occurring in ICU patients, being particularly common in patients with cardiovascular and respiratory failure. Unlike ambulatory patients in whom atrial fibrillation/flutter (AF) is likely to be short lived, in the critically ill these arrhythmias are unlikely to resolve until the underlying disease process has improved. Urgent cardioversion is indicated for hemodynamic instability. Treatment in hemodynamically stable patients includes correction of treatable precipitating factors, control of the ventricular response rate, conversion to sinus rhythm, and prophylaxis against thromboembolic events in those patients who remain in AF. Diltiazem is the preferred agent for rate control, while procainamide and amiodarone are generally considered to be the antiarrhythmic agents of choice.

Atrial fibrillation after cardiac operation: risks, mechanisms, and treatment

Atrial fibrillation (AF) is a common complication of cardiac operations that leads to increased risk for thromboembolism and excessive health care resource utilization. Advanced age, previous AF, and valvular heart operations are the most consistently identified risk factors for this arrhythmia. Dispersion of repolarization leading to reentry is believed to be the mechanism of postoperative AF, but many questions regarding the pathophysiology of AF remain unanswered. Treatment is aimed at controlling heart rate, preventing thromboembolic events, and conversion to sinus rhythm. Multiple investigations have examined methods of preventing postoperative AF, but the only firm conclusions that can be drawn is to avoid beta-blocker withdrawal after operation and to consider beta-blocker therapy for other patients who may tolerate these drugs. Preliminary investigations showing sotalol and amiodarone to be effective in preventing postoperative AF are encouraging, but early data have been limited to selective patient populations and have not adequately evaluated safety. Newer class III antiarrhythmic drugs under development may have a role in the treatment of postoperative AF, but the risk of drug-induced polymorphic ventricular tachycardia must be considered. Nonpharmacologic interventions under consideration for the treatment of AF in the nonsurgical setting, such as automatic atrial cardioversion devices and multisite atrial pacing, may eventually have a role for selected cardiac surgical patients.

Intravenous Amiodarone in the Management of Atrial Fibrillation

BACKGROUND: Although approved only for therapy of life-threatening ventricular tachyarrhythmias, intravenous amiodarone is also being used for the treatment of atrial fibrillation (AF), generally in the intensive care unit setting and most often after cardiac surgery. When used for AF, dosing regimens and clinical experience have varied. METHODS AND RESULTS: This article summarizes representative reports in hopes of clarifying the role of intravenous amiodarone for practitioners who prescribe it for the management of AF. The most immediate and most predictable response is reduction of the ventricular rate, which generally is noted after the first 300-400 mg. Restoration of sinus rhythm (cardioversion) may occur, but the precise incidence in a placebo-controlled, blinded study has not been determined. When present, it often takes 24 hours, and a total dose of 1,000 mg or more. Least certain is the efficacy of the drug in preventing the appearance (when used prophylactically) or reappearance of AF. CONCLUSIONS: More data are required with regard to patient characterization, electrical system status, and dosing regimen to better characterize intravenous amiodarone for this role.

Sequential changes in the metabolic response in severely septic patients during the first 23 days after the onset of peritonitis

OBJECTIVE

To quantify the sequential changes in metabolic response occurring in patients with severe sepsis after the onset of peritonitis.

SUMMARY BACKGROUND DATA

Understanding the changes in energy expenditure and body composition is essential for the optimal management of severely septic patients; however, they have not been quantified in the context of modern surgical care.

METHODS

Twelve patients with severe sepsis secondary to peritonitis (median APACHE II score = 21.5) had measurements of energy expenditure and body composition as soon as they were hemodynamically stable and 5, 10, and 21 days later. Sequential measurements of acute-phase proteins and cytokine responses were also made.

RESULTS

Resting energy expenditure rose to 49% above predicted and remained elevated throughout the study period. Total energy expenditure was 1.25 x resting energy expenditure. Body fat was oxidized when energy intake was insufficient to achieve energy balance. There was a positive fluid balance of 12.5 1 over the first 2 days after onset of sepsis; thereafter, body water changes closely paralleled body weight changes and were largely accounted for by changes in extracellular water. During the 21 -day study period, there was a loss of 1.21 kg (13%) of total body protein. During the first 10 days, 67% of the protein lost came from skeletal muscle, but after this time it was predominantly from viscera. Intracellular potassium levels were low but did not deteriorate further after hemodynamic stability had been reached. There was a reprioritization of hepatic protein synthesis that was obligatory and independent of changes in total body protein. The cytokine responses demonstrated the complexity, redundancy, and overlap of mediators.

CONCLUSIONS

The period of hypermetabolism in severely septic patients is similar to that previously described, but the fluid changes are larger and the protein loss is greater. Protein loss early on is predominantly from muscle, thereafter from viscera. Fat loss can be prevented and cell function preserved once hemodynamic stability is achieved.

Treatment strategies for atrial fibrillation

Atrial fibrillation is the most common arrhythmia observed in clinical practice, occurring in 0.4% of the general population and in up to 4% of people greater than 60 years old. It is often associated with other cardiovascular disorders, such as hypertension, coronary artery disease, or cardiomyopathy. Critical evaluation and management of patients with atrial fibrillation requires knowledge of etiology, prognosis, and treatment options of this arrhythmia. On initial presentation, emergency electrical cardioversion should be performed if the patient is hemodynamically unstable. If the patient is stable, initial rate control is recommended, using atrioventricular nodal blocking agents. Further treatment mainly depends upon the duration of the episode. Patients who are in atrial fibrillation <48 hours can be safely cardioverted. Patients who are in atrial fibrillation for >48 hours are commonly anticoagulated for 3 to 4 weeks before and after cardioversion because of the risk of thromboembolism formation in the left atrial appendage. An alternate strategy, which is especially attractive when immediate cardioversion is desired, is transesophageal echocardiography to exclude left atrial thrombus followed by prompt cardioversion. After cardioversion, sinus rhythm can be maintained with class I and III drugs, such as flecainide and propafenone or amiodarone and sotalol. New treatment options, such as atrial defibrillation, atrioventricular junctional ablation, or modification of atrial pacing to prevent atrial fibrillation, are currently under investigation. Although atrial fibrillation is so common in clinical practice, it still remains difficult to treat. Conversion and maintenance to sinus rhythm with antiarrhythmic drug therapy has not shown any improvement in mortality, and some patients may benefit more from ventricular rate control. This review article discusses different treatment strategies for patients with atrial fibrillation.

Antiarrhythmic drug therapy in the management of atrial fibrillation

Antiarrhythmic drugs have been used for the acute conversion of atrial fibrillation to sinus rhythm, as well as for the long-term maintenance of sinus rhythm. In recent years, concerns regarding antiarrhythmic drug efficacy as well as safety have prompted a re-examination of the indications for antiarrhythmic therapy in patients with atrial fibrillation. This review will focus on the safety and efficacy of antiarrhythmic therapy in the acute and chronic management of patients with atrial fibrillation.

Preoperative therapy with amiodarone and the incidence of acute organ dysfunction after cardiac surgery

We examined the influence of preoperative therapy with amiodarone on the incidence of acute organ dysfunction after cardiac surgery in a matched case-control study. There were 220 case-control pairs matched by day of surgery, source of admission, demographic characteristics, placement of intraaortic balloon pump before surgery, repeat operations, emergency surgery, thoracic aorta surgery and other surgical procedures. History of congestive heart failure was more prevalent in the amiodarone group than in the control group before surgery (60% vs 38%, P < 0.0001). The incidence of acute organ dysfunction, duration of mechanical ventilation, and death was similar in both groups after surgery. The requirement for inotropes (26% vs 17%, P = 0.03) and vasopressors (66% vs 55%, P = 0.02) and the incidence of postoperative nosocomial infections (12% vs 6%, P = 0.04) was greater in the amiodarone group. However, the difference was not significant after adjustment for congestive heart failure (Cochran-Mantel-Haenszel test P = 0.15, P = 0.25, P = 0.16, respectively). Amiodarone did not increase the incidence of acute organ dysfunction or death after cardiac surgery. The requirement for inotropes and vasopressors and the incidence of nosocomial infections were related to the severity of the underlying cardiac disease. The practice of discontinuing amiodarone treatment before surgery to reduce the incidence of postoperative organ dysfunction should be critically reevaluated.

IMPLICATIONS

Amiodarone is often used for the treatment of life-threatening rhythm disorder. Amiodarone has been blamed for causing organ injury after cardiac surgery. In a study of 220 patients, amiodarone did not increase the risk of organ injury or death after cardiac surgery when compared with control patients. There was no evidence to support the practice of stopping amiodarone before cardiac surgery to avoid serious complications.

Intravenous amiodarone

Intravenous amiodarone was approved in 1995 for the treatment of malignant and resistant ventricular arrhythmia. Although it is an "old drug," much has been learned recently about this complex drug and its application in a variety of cardiac arrhythmias. The objectives of this review were to summarize what is known about intravenous amiodarone, including its pharmacologic and electrophysiologic effects, to review its efficacy for the treatment of patients with highly malignant ventricular arrhythmia and to provide specific information about its clinical use for this and other indications. The studies that were reviewed were selected on the basis of time published (from 1983 to 1995) and the completeness of information provided regarding patient clinical characteristics, drug dosing and methods of evaluation, efficacy analyses, long-term follow-up and complications. The full data from the three controlled trials that formed the basis of the drug's approval are contained in published reports that were also extensively reviewed. Intravenous amiodarone has demonstrable efficacy for the treatment of frequently recurrent destabilizing ventricular tachycardia and ventricular fibrillation, with suppression rates of 63% to 91% in uncontrolled trials. The three pivotal trials confirmed these findings and demonstrated a dose-response relation, with at least comparable efficacy to bretylium, a drug with a similar indication. The safety profile has also been well described; cardiovascular adverse effects are the most frequent, especially hypotension. Intravenous amiodarone is a useful addition to the drugs available for the treatment of patients with very severe ventricular arrhythmia. Its use in patients with other rhythm disorders appears promising, but final recommendations must await development of definitive data from ongoing clinical trials.

Intravenous amiodarone is safe and seems to be effective in termination of paroxysmal supraventricular tachyarrhythmias

BACKGROUND

Paroxysmal atrial fibrillation (PAF) and paroxysmal supraventricular tachycardia (PSVT) leading to hemodynamic compromise are among the most common reasons for admission to the coronary care unit (CCU) and need prompt and efficient therapy. Direct current cardioversion is the therapy of choice, but if found contraindicated or unavailable some antiarrhythmic agents are usually given to restore sinus rhythm. Many of these drugs have obvious limitations, especially in patients with acute myocardial infarction and/or heart failure.

HYPOTHESIS

The aim of the present study was to assess the safety and efficacy of intravenous amiodarone in the acute termination of PAF or PSVT refractory to other antiarrhythmic agents in a large group of patients consecutively admitted to our CCU.

METHODS

In the present study, we evaluated the safety and efficacy of amiodarone given intravenously in 142 consecutive patients with PAF or PSVT lasting < 24 h. In 37% of patients no evidence of underlying heart disease which may have caused arrhythmias were defined. A median of two other antiarrhythmic agents given prior to the first amiodarone injection had been ineffective.

RESULTS

Sinus rhythm was restored in 91 patients (64%) (65% in the PAF group and 61% in the PSVT group). The mean time to rhythm conversion was 5.5 +/- 6.1 h for patients with PAF and 1.2 +/- 1.2 h for patients with PSVT. The mean dose of amiodarone administered up to conversion was 340 +/- 220 mg for PAF and 220 +/- 105 mg for PSVT. Except for transient first-degree atrioventricular block in two patients, no adverse effects possibly related to amiodarone were observed (including proarrhythmia and incidence or aggravation of heart failure symptoms).

CONCLUSION

Amiodarone given intravenously for acute termination of supraventricular tachyarrhythmias is completely safe and seems effective. The results of this study, which is the largest ever made, indicate a need of randomized, controlled trials for the ultimate assessment of the efficacy of amiodarone in this clinical setting.

Intravenous amiodarone in treatment of recent-onset atrial fibrillation: results of a randomized, controlled study

OBJECTIVES

This study was designed to determine the efficacy of intravenous amiodarone in the management of recent-onset atrial fibrillation.

BACKGROUND

The optimal approach for acute atrial fibrillation has not been established. Amiodarone is a unique antiarrhythmic agent with activity in both supraventricular and ventricular tachyarrhythmias, but its value for the restoration of sinus rhythm in patients with recent-onset atrial fibrillation has not been demonstrated.

METHODS

Sample size was calculated to detect a 25% increase in reversion rate with amiodarone with a statistical power of 80%. One hundred consecutive patients with recent-onset (<1 week) atrial fibrillation and not taking antiarrhythmic agents were randomized to receive either intravenous amiodarone, 5 mg/kg body weight in 30 min followed by 1,200 mg over 24 h, or an identical amount of saline. Both groups received intravenous digoxin, 0.5 mg initially, followed by 0.25 mg at 2 h and 0.25 mg every 6 h thereafter, to complete 24 h while the ventricular rate was >100 beats/min. Amiodarone and digoxin blood levels were determined. Both groups were homogeneous regarding underlying heart disease, time from onset to treatment, initial ventricular rate and left atrial size.

RESULTS

By the end of the 24-h treatment period, 34 patients (68%, 95% confidence interval [CI] 53% to 80%) in the amiodarone group and 30 (60%, 95% CI 45% to 74%) in the control group had returned to sinus rhythm (p = 0.532). Mean times (+/-SD) of conversion were 328 +/- 335 and 332 +/- 359 min, respectively (p =0.957). Among patients who did not convert to sinus rhythm, treatment with amiodarone was associated with a slower ventricular rate (82 +/- 15 beats/min in the amiodarone group vs. 91 +/- 23 beats/min in the control group, p = 0.022). After restoration of sinus rhythm, atrial fibrillation recurred during a 15-day follow-up period in 4 (12%) of 34 patients (95% CI 3% to 27%) in the amiodarone group and in 3 (10%) of 30 (95% CI 2% to 26%) in the control group (p = 0.861).

CONCLUSIONS

Intravenous amiodarone, at the doses used in this study, produces a modest but not significant benefit in converting acute atrial fibrillation to sinus rhythm.

Parenteral magnesium sulfate versus amiodarone in the therapy of atrial tachyarrhythmias: a prospective, randomized study

OBJECTIVE

To compare the efficacy of parenteral magnesium sulfate vs. amiodarone in the therapy of atrial tachyarrhythmias in critically ill patients.

DESIGN

Prospective, randomized study.

SETTING

Multidisciplinary intensive care unit (ICU) at a university teaching hospital.

PATIENTS

Forty-two patients, 21 medical and 21 surgical, of mean (SD) age 67 +/- 15 yrs and mean Acute Physiology and Chronic Health Evaluation II score of 22 +/- 6, with atrial tachyarrhythmias (ventricular response rate of > or = 120 beats/min) sustained for > or = 1 hr.

INTERVENTIONS

After correction of the plasma potassium concentration to > or = 4.0 mmol/L, patients were randomly allocated to treatment with either a) magnesium sulfate 0.037 g/kg (37 mg/kg) bolus followed by 0.025 g/kg/hr (25 mg/kg/hr); or b) amiodarone 5 mg/kg bolus and 10 mg/kg/24-hr infusion. Therapeutic plasma magnesium concentration in the magnesium sulfate group was 1.4 to 2.0 mmol/L. Therapeutic end point was conversion to sinus rhythm over 24 hrs.

MEASUREMENTS AND MAIN RESULTS

At study entry (time 0), initial mean ventricular response rate and systolic blood pressure were 151 +/- 16 (SD) beats/min and 127 +/- 30 mm Hg in the magnesium sulfate group vs. 153 +/- 23 beats/min and 123 +/- 23 mm Hg in the amiodarone group, respectively (p = .8 and .65). Plasma magnesium (time 0) was 0.84 +/- 0.20 vs. 1.02 +/- 0.22 mmol/L in the magnesium and amiodarone group, respectively (p = .1). Eight patients had chronic dysrhythmias (magnesium 3, amiodarone 5). Excluding the two patient deaths (amiodarone group, time 0 + 12 to 24 hrs), no significant change in systolic blood pressure subsequently occurred in either group. In the magnesium group, mean plasma magnesium concentrations were 1.48 +/- 0.36, 1.82 +/- 0.41, 2.16 +/- 0.45, and 1.92 +/- 0.49 mmol/L at time 0 + 1, 4, 12 and 24 hrs, respectively. By logistic regression, the probability of conversion to sinus rhythm was significantly better for magnesium than for amiodarone at time 0 + 4 (0.6 vs. 0.44), 12 (0.72 vs. 0.5), and 24 (0.78 vs. 0.5) hrs. In patients not converting to sinus rhythm, a significant decrease in ventricular response rate occurred at time 0 + to 0.5 hrs (mean decrease 19 beats/min, p = .0001), but there was no specific treatment effect between the magnesium and the amiodarone groups; thereafter, there was no significant reduction in ventricular response rate over time in either group.

CONCLUSIONS

Intravenous magnesium sulfate is superior to amiodarone in the conversion of acute atrial tachyarrhythmias, while initial slowing of ventricular response rate in nonconverters appears equally efficacious with both agents.