Amiodarone versus diltiazem for rate control in critically ill patients with atrial tachyarrhythmias

Life-threatening arrhythmias in the intensive care unit

Symptomatic arrhythmias are frequently observed in the intensive care unit and often lead to significant hemodynamic compromise because of the presence of multisystem disease. In particular, prompt evaluation of patients with tachycardia is critical because treatment depends on the accurate diagnosis of the arrhythmia mechanism. The electrocardiogram remains the most important diagnostic tool for the evaluation of both wide complex and narrow complex tachycardia. For wide complex tachycardia, evaluation of the atrioventricular relationship and QRS morphology are critical, and for narrow QRS complex tachycardias, evaluation focuses on identification of the location and morphology of P waves. Bradycardia can arise from sinus node dysfunction or atrioventricular conduction block.

Enhancing electrical cardioversion and preventing immediate reinitiation of hemodynamically deleterious atrial fibrillation with class III drug pretreatment

Nifekalant for shock-resistant atrial fibrillation.

INTRODUCTION

In severely ill patients, the development of atrial fibrillation (AF) may provoke lethal hemodynamic instability requiring immediate electrical defibrillation, which often is unsuccessful. Using the novel potassium channel blocking agent nifekalant, we prospectively assessed the hypothesis that class III antiarrhythmic drugs facilitate electrical cardioversion and suppress the immediate recurrence of hemodynamically deleterious AF.

METHODS AND RESULTS

Among 1896 adults admitted to the intensive care unit for cardiovascular diseases, hemodynamically destabilizing new-onset AF (systolic blood pressure<90 mm Hg) resistant to conventional electrical cardioversion occurred in 27 patients, and of these, 24 patients (70+/-12 years) were enrolled. Twenty-one patients had congestive heart failure and 11 patients had been mechanically ventilated. After three failed transthoracic cardioversions due to failure of conversion to SR (11 patients) or immediate reinitiation (13 patients), nifekalant (0.25+/-0.04 mg/kg) was administered intravenously, and electrical defibrillation was reattempted. In 18 patients (75%), sinus rhythm was restored and maintained after nifekalant infusion (6 patients) or subsequent transthoracic cardioversion (12 patients). Nifekalant administration significantly decreased the heart rate and increased systolic blood pressure during AF (P<0.001), and successful cardioversion rapidly further ameliorated these parameters (P<0.001). Logistic regression analysis showed that atrial defibrillation failure (relative risk [RR] 19.34, P=0.05) and age of >75 years (RR 15.25, P=0.03) were independent predictors of in-hospital death.

CONCLUSION

Nifekalant renders electrical defibrillation and the prevention of the early recurrence of hemodynamically unstable AF more successful without deteriorating hemodynamics, and successful defibrillation is associated with a more favorable patient outcome. Pretreatment with other class III drugs, e.g., ibutilide or dofetilide, would also be efficacious in patients with failed urgent electrical cardioversion.

Supraventricular tachyarrhythmia as early indicator of a complicated course after esophagectomy

In a group of 89 consecutive patients with a standardized operative procedure, the incidence of supraventricular tachyarrhythmia (SVT), predisposing risk factors (preoperative and intraoperative factors and parameters of intensive care strategy) and therapeutic strategies were evaluated. Operative treatment consisted of transthoracic esophagectomy, gastric interposition and intrathoracic anastomosis. Overall hospital mortality was 6.7%. In 32 (37%) patients a new onset SVT occurred. Age and elevated body temperature were the only significant risk factor for SVT in the multivariate analysis, their odds ratios being 1.3 for each year above 58 and 5.6 for each degree above 37.8 degrees C, respectively. Secondary risk factors were history of hypertension and use of epinephrine, the corresponding odds ratios being 6.6 and 10.2. Digitalis (2/32) and calcium-antagonists (2/9) were unsatisfactory, while beta-blockers (13/20) and amiodarone (12/12) were efficient therapeutic agents. Incidence of SVT was significantly correlated with the development of postoperative septic complications.

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.

Amiodarone-induced acute lung toxicity in an ICU setting

Amiodarone is a highly effective antiarrhythmic drug, albeit notorious for its serious pulmonary toxicity. The incidence of amiodarone-induced pulmonary toxicity (APT) appears to be 1% per year (1). We report a case of very acute APT in a man suffering from postoperative atrial fibrillation.

High-dosage continuous amiodarone therapy to treat new-onset supraventricular tachyarrhythmias in surgical intensive care patients: an observational study

BACKGROUND

New-onset supraventricular tachyarrhythmias (SVTA) are a complication contributing significantly to morbidity and mortality in surgical intensive care unit (SICU) patients. Although only few data on efficiency can be found in the literature, class III antiarrhythmics have become popular in the treatment of SVTA in critically ill patients.

SETTING

12-bed general and surgical ICU in a university teaching hospital.

DESIGN

Observational, retrospective study.

PATIENTS

131 SICU patients with SVTA (narrow-complex non-sinus tachyarrhythmias with heart rates > or = 100 bpm).

INTERVENTION

High-dosage amiodarone infusion according to an institutional protocol.

MEASUREMENTS

Hemodynamic data, acid-base status, and single organ functions were obtained in all patients before amiodarone infusion and at 12, 24, and 48 hours afterwards. Patients were divided into responders and nonresponders. Amiodarone infusion (mean dosage 24 h: 1625+/-528 mg; 48 h: 2708+/-895 mg) restored sinus rhythm in 54% of study patients within 12 h, in 64% within 24 h, and in 75% within 48 h. Heart rate, central venous pressure, and milrinone requirements significantly decreased in all patients; this was accompanied by a significant increase in stroke-volume index and mean arterial pressure. Serum concentrations of creatinine and bilirubin increased in all patients.

CONCLUSION

High-dosage continuous amiodarone infusion during a period of 48 hours resulted in restoration of SR in 75% of SICU patients with new-onset SVTA and moderate to severe multiple-organ dysfunction syndrome. A significant improvement in cardiocirculatory function was more pronounced in responders but could be demonstrated irrespective of restoration of sinus rhythm in all patients. Apart from a possibly amiodarone-mediated increase in concentrations of creatinine and bilirubin, no major drug-related adverse effects occurred during the observation period.

Management of atrial fibrillation

Atrial fibrillation (AF) is the most common clinically important arrhythmia in veterinary medicine. Electrical cardioversion of AF to sinus rhythm is feasible, but pharmacologic rate control is an effective and achievable treatment strategy for most veterinary patients. Recent human trials suggest that rate control and rhythm control are almost equally beneficial. Nevertheless, AF can be a challenging arrhythmia to manage, because most affected animal shave numerous other concurring problems associated with the underlying heart disease that dictate or influence the clinician's choice of treatment and monitoring strategy for each patient.

Clinical review: clinical management of atrial fibrillation - rate control versus rhythm control

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the critically ill and is associated with adverse outcomes. Although there are plausible benefits from conversion and maintenance of sinus rhythm (the so-called 'rhythm-control' strategy), recent randomized trials have failed to demonstrate the superiority of this approach over the rate-control strategy. Regardless of approach, continuous therapeutic anticoagulation is crucial for stroke prevention. This review addresses the findings of these studies and their implications for clinical management of patients with atrial fibrillation.

Arrhythmias in the intensive care patient

PURPOSE OF REVIEW

Atrial fibrillation, atrial flutter, AV-nodal reentry tachycardia with rapid ventricular response, atrial ectopic tachycardia, and preexcitation syndromes combined with atrial fibrillation or ventricular tachyarrhythmias are typical arrhythmias in intensive care patients. Most frequently, the diagnosis of the underlying arrhythmia is possible from the physical examination, the response to maneuvers or drugs, and the 12-lead surface electrocardiogram. In all patients with unstable hemodynamics, immediate DC-cardioversion is indicated. Conversion of atrial fibrillation to sinus rhythm is possible using antiarrhythmic drugs. Amiodarone has a conversion rate in atrial fibrillation of up to 80%. However, caution in the use of short-term administration of intravenous amiodarone in critically ill patients with recent-onset atrial fibrillation is absolutely necessary, and the duration of therapy should not exceed 24 to 48 hours. Ibutilide represents a relatively new class III antiarrhythmic agent that has been reported to have conversion rates of 50% to 70%; it seems that ibutilide is even successful when intravenous amiodarone failed to convert atrial fibrillation.

RECENT FINDINGS

Newer studies compared the outcome of patients with atrial fibrillation and rhythm- or rate-control. Data from these studies (AFFIRM, RACE) clearly showed that rhythm control is not superior to rate control for the prevention of death and morbidity from cardiovascular causes. Therefore, rate-control may be an appropriate therapy in patients with recurrent atrial fibrillation after DC-cardioversion. Acute therapy of atrial flutter in intensive care patients depends on the clinical presentation. Atrial flutter can most often be successfully cardioverted to sinus rhythm with energies less than 50 joules. Ibutilide trials showed efficacy rates of 38-76% for conversion of atrial flutter to sinus rhythm compared with conversion rates of 5-13% when intravenous flecainide, propafenone, or verapamil was administered. In addition, a high dose (2 mg) of ibutilide was more effective than sotalol (1.5 mg/kg) in conversion of atrial flutter to sinus rhythm (70% versus 19%).

SUMMARY

There is general agreement that bystander first aid, defibrillation, and advanced life support is essential for neurologic outcome in patients after cardiac arrest due to ventricular tachyarrhythmias. The best survival rate from cardiac arrest can be achieved only when (1) recognition of early warning signs, (2) activation of the emergency medical services system, (3) basic cardiopulmonary resuscitation, (4) defibrillation, (5) management of the airway and ventilation, and (6) intravenous administration of medications occurs as rapidly as possible. Public access defibrillation, which places automatic external defibrillators in the hands of trained laypersons, seems to be an ideal approach in the treatment of ventricular fibrillation. The use of automatic external defibrillators by basic life support ambulance providers or first responder in early defibrillation programs has been associated with a significant increase in survival rates. Drugs such as lidocaine, procainamide, sotalol, amiodarone, or magnesium were recommended for treatment of ventricular tachyarrhythmias in intensive care patients. Amiodarone is a highly efficacious antiarrhythmic agent for many cardiac arrhythmias, ranging from atrial fibrillation to malignant ventricular tachyarrhythmias, and seems to be superior to other antiarrhythmic agents.

New treatments for perioperative cardiac arrhythmias

Cardiac arrhythmias remain a major source of morbidity, mortality, and prolonged postoperative hospital stay in surgical patients. Recent studies in patients experiencing out-of-hospital cardiac arrest have expanded our knowledge in the management of cardiac arrhythmias. Future advances require additional studies focused on the unique proarrhythmic substrates in surgical patients, to provide a clear rationale for antiarrhythmic drug therapy in the perioperative period.

Advances in the acute pharmacologic management of cardiac arrhythmias

Safe and effective control of rapid ventricular rates in acute-onset atrial fibrillation (AF) can be accomplished with intravenous calcium antagonists, beta-blockers or amiodarone; digoxin is less effective. If pharmacologic cardioversion of AF is desired, single oral doses of propafenone or flecainide are safe and effective in patients without structural heart disease. Intravenous ibulitide is moderately effective in the conversion of persistent AF or atrial flutter, with a small risk of proarrhythmia. In wide QRS complex tachycardia of uncertain origin, adenosine and lidocaine are no longer recommended. Procainamide or amiodarone are the treatment options, but attempts should be made to define the origin of tachycardia. In the treatment of monomorphic ventricular tachycardia, lidocaine is no longer recommended; procainamide or amiodarone are the recommended therapies. In polymorphic ventricular tachycardia with a normal QT interval, beta-blockers are recommended. In shock-refractory ventricular fibrillation, lidocaine, and magnesium are ineffective; intravenous amiodarone should be the treatment of choice.

Successful use of iv diltiazem to control perioperative refractory complex atrial tachyarrhythmias in a patient with pneumoconiosis

PURPOSE

To present a patient with pneumoconiosis who developed a complex, life-threatening atrial tachyarrhythmia during anesthesia. Intravenous diltiazem was effective in controlling the ventricular rate and hemodynamics after failure of other antiarrhythmic drugs and direct current cardioversion.

CLINICAL FEATURES

A 79-yr-old man with pneumoconiosis complicated by cor pulmonale suffered from gout-related cellulitis of the left lower limb. Debridement of the left gangrenous big toe was carried out under general anesthesia. During anesthesia, a wide-QRS tachycardia occurred suddenly and a complex atrial tachyarrhythmia was later diagnosed. Hemodynamics deteriorated despite aggressive treatment with lidocaine, verapamil, direct current cardioversion, magnesium, digoxin and amiodarone. Correction of the underlying respiratory acidosis was not sufficient to control the rapid ventricular response. Eventually, iv diltiazem adequately controlled the rapid ventricular rate and quickly improved the deteriorating hemodynamics.

CONCLUSION

Life-threatening complex atrial tachyarrhythmias may occur in patients with chronic lung diseases perioperatively. Intravenous diltiazem was effective in the management of complex atrial tachyarrhythmia in a patient with underlying cor pulmonale.

Electrocardiographic manifestations: narrow QRS complex tachycardias

Narrow QRS complex tachycardia is a common dysrhythmia in Emergency Medicine practice. Diagnosis and mechanism often can be made by 12-lead electrocardiographic (EKG) analysis but may subsequently require electrophysiologic testing. The clinical manifestations are varied and dependent upon heart rate, prior cardiac disease, and general physiologic status. Patient management is directed towards the etiology and mechanism of the dysrhythmia and includes vagal maneuvers, pharmacologic therapy, and cardioversion. Hemodynamically compromised patients must be promptly treated. Patients are often admitted to the hospital but selected patients can be safely discharged from the Emergency Department for outpatient evaluation and management. Pediatric and pregnant patients are, in general, treated the same as adults. Several case examples and EKGs are presented.