Atrial Fibrillation 1992

The frequency analysis of signal-averaged ECG of P wave as predictor of efficacy of class III antiarrhythmic drugs to maintain sinus rhythm in recurrent idiopathic atrial fibrillation

BACKGROUND

The use of class III antiarrhythmic drugs (ADIII) has been considered a good predictor of sinus rhythm in patients post-cardioversion from atrial fibrillation (AF). Several studies using frequency domain analysis of signal-averaged ECG (FDSAECG) of the P wave were able to identify patients at risk for AF. The aim of this study was to assess the FDSAECG in predicting recurrence of idiopathic persistent AF (IPAF) in patients under ADIII therapy.

METHODS

In 33 patients with two or more previous symptomatic episodes of IPAF, despite classes I and II therapy, the FDSAECG of the P wave was performed during sinus rhythm and free-drug state. The parameters were the mean and standard deviation of the frequency intersegmentar spectral correlation and the standard deviation of the signal frequency edge track. During the follow-up of 30 +/- 18 months, all patients received either amiodarone or sotalol.

RESULTS

During the follow-up, the patients were divided into two groups: Group I-frequent recurrence (>or= three events/year; 16 patients), and Group II-infrequent recurrence (< three events/year; 17 patients). With appropriate cutoff points for each parameter analyzed, intense fragmented electrical activity defined by the presence of at least two abnormal criteria were observed in 13 of 16 patients group I and in 3 of 17 patients group II (P = 0.0003). Sensitivity, specificity, positive and negative predictive values for frequent recurrence were 81.3, 82.4, 81.3, and 82.4, respectively.

CONCLUSIONS

The results suggested that FDSAECG analysis of the P wave accurately predicted patients whose ADIII therapy will be effective in maintaining the sinus rhythm without frequent recurrence of IPAF.

Spectral turbulence analysis of the signal-averaged electrocardiogram of the atrial activation as predictor of recurrence of idiopathic and persistent atrial fibrillation

The frequency domain analysis of the P-wave signal-averaged ECG (P-SAECG) is able to identify patients at risk for lone atrial fibrillation (AF) after cardioversion to sinus rhythm. The terminal portion of the P-wave of right precordial leads on 12-lead ECG is associated with electrical abnormalities in the atria. The aim of this study was to assess the spectral turbulence analysis (STA) of the P-SAECG as a predictor of recurrence of idiopathic AF. STA was performed in 41 patients with 2 or more symptomatic episodes of idiopathic and persistent AF after successful electrical cardioversion and drug-free state (Group A), and in 25 control individuals during sinus rhythm (Group B), matched by age, gender, and P-wave duration. The orientation of the terminal portion (positive or negative) of the Z-lead was assessed as representing right precordial leads potentials. After 6 months follow-up, Group A was divided into two groups according to recurrence: G-A1--at least one recurrence (21 patients), and G-A2--no recurrence (20 patients). Fragmented electrical activity (FEA) was observed in 19 patients of G-A1 and in 2 of G-A2 (odds ratio = 85.5; p<<0.001). STA showed 90.5% sensitivity and 90.0% specificity for early recurrence of AF. After 12 months, no patients of G-A2 and 15 of G-A1 developed >3 episodes of persistent AF, being FEA observed in 13 (odds ratio = 14.6, p = 0.002). No episodes of AF were observed in Group B. Average time for recurrence of FEA positive patients (4.3 +/- 0.7 months) was significantly shorter than of G-A2 (7.4+/-0.7 months), and log-rank analysis revealed significant difference of event-free rate over time (p = 0.004). In a logistic regression model FEA, use of amiodarone and a positive terminal portion of the Z-lead of the P-SAECG were independent predictors of recurrence of idiopathic and persistent AF.

Clinical assessment of clonidine in the treatment of new-onset rapid atrial fibrillation: a prospective, randomized clinical trial

PURPOSE

The role of digoxin and verapamil in the control of ventricular response in rapid atrial fibrillation is well established. This study investigates how clonidine compares with these standard therapies in rate control for new-onset rapid atrial fibrillation. We set out to test the hypothesis that clonidine effectively reduces heart rate in patients with new-onset rapid atrial fibrillation.

SUBJECTS AND METHODS

Forty patients were seen in the emergency department with new-onset (< or =24 hours' duration), stable, rapid atrial fibrillation. Eligible patients were randomized to receive either clonidine, digoxin, or verapamil. Changes in heart rate and blood pressure over 6 hours, as well as frequency of conversion to sinus rhythm were recorded and analyzed.

RESULTS

The mean reduction in heart rate over 6 hours was 44.4 beats/min (95% confidence interval [CI] 28.4-60.4 beats/min) in the clonidine group, 52.1 beats/min (95% CI 40.8-63.4 beats/min) in the digoxin group, and 41.8 beats/min (95% CI 22.5-61.0 beats/min) in the verapamil group. Analysis of variance of the heart rate changes in the 3 groups after 6 hours was not significant (P =.55). At 6 hours, 7 of 12 clonidine patients, 8 of 15 digoxin patients, and 7 of 13 verapamil patients remained in atrial fibrillation (P =.962 on chi(2)).

CONCLUSION

Clonidine controls ventricular rate in new-onset atrial fibrillation with an efficacy comparable to that of standard agents.

The use of diltiazem for treating rapid atrial fibrillation in the out-of-hospital setting

STUDY OBJECTIVE

We sought to evaluate the use of intravenous diltiazem for treatment of rapid atrial fibrillation or flutter (RAF) in the out-of-hospital setting.

METHODS

This study is a retrospective review of data with historical control subjects. Data were drawn from out-of-hospital patients reported to a statewide paramedic system who presented with atrial fibrillation or flutter and a ventricular response rate (VRR) of 150 beats/min or greater. The intervention (diltiazem) group included patients who received diltiazem during a 9-month period in 1999. The control group included patients from 1998 who did not receive diltiazem. Patients who were intubated or underwent cardioversion were omitted. Therapeutic response was defined as the occurrence of change to sinus rhythm, reduction of VRR to 100 beats/min or less, or reduction of baseline VRR by 20% or greater. Data were analyzed by using the chi(2) test, the Student's t test, and odds ratios (ORs). A Bonferroni adjusted P value of.005 was used to define statistical significance.

RESULTS

Forty-three patients receiving diltiazem and 27 control subjects were included in the study. The mean total diltiazem dose was 19.8 mg (95% confidence interval 17.8 to 21.8). The diltiazem and control groups did not significantly differ with respect to age; sex; history of atrial fibrillation; prior use of digitalis, beta-blockers, or calcium channel blockers; concurrent out-of-hospital therapies; or baseline VRR or systolic blood pressure (P =.09 to 1.00). The difference in VRR reduction between the diltiazem and control groups was 38 beats/min (95% confidence interval 24 to 52); this difference was statistically significant (P <.001). The mean percentage reduction of VRR in the diltiazem group was -33.1%. The difference in systolic blood pressure change between the diltiazem and control groups was not statistically significant (P =.17). The diltiazem group had a higher prevalence of achieving VRR reduction to 100 beats/min or less than did the control group (OR 22.6; P <.001), of achieving a VRR reduction of 20% or greater (OR 19.3; P <.001), and of achieving overall therapeutic response (OR 19.3; P <.001). Few changed to sinus rhythm in either group (estimated OR 6.3; P =.15). No patients in the diltiazem group required treatment for hypotension, endotracheal intubation, resuscitation from cardiac arrest, or emergency treatment of unstable dysrhythmias.

CONCLUSION

The effects of diltiazem on RAF can be appreciated within the constraints of the out-of-hospital environment. Diltiazem should be considered as a viable field therapy for rate control of RAF.

Effectiveness of amiodarone as a single oral dose for recent-onset atrial fibrillation

The efficacy of amiodarone has been proved in long-term maintenance of sinus rhythm (SR) in patients with paroxysmal atrial fibrillation (AF). The present study evaluates the efficacy and safety of a single oral dose of amiodarone in patients with recent-onset AF (<48 hours). Seventy-two patients were randomized to receive 30 mg/kg of either amiodarone or placebo. Conversion to SR was verified by 24-hour Holter monitoring. Ten patients were excluded because of SR in the beginning of monitoring or technical failure during Holter monitoring. The remaining study groups were comparable (n = 31 for each), except that in the placebo group beta blockers were more common. The patients receiving amiodarone converted to SR more effectively than those receiving placebo (p<0.0001). At 8 hours, approximately 50% of patients in the amiodarone group and 20% in the placebo group (Holter successful) had converted to SR, whereas after 24 hours the corresponding figures were 87% and 35%, respectively. The median time for conversion (8.7 hours for amiodarone and 7.9 hours for placebo) did not differ in the groups. Amiodarone was hemodynamically well tolerated, and the number of adverse events in the study groups was similar. Amiodarone as a single oral dose of 30 mg/kg appears to be effective and safe in patients with recent-onset AF.

Ibutilide: an antiarrhythmic agent for the treatment of atrial fibrillation or flutter

OBJECTIVE

To discuss the clinical pharmacology of the antiarrhythmic drug ibutilide in patients with atrial fibrillation (AF) or atrial flutter (AFl).

DATA SOURCES

A MEDLINE search (January 1983-December 1997) was used to identify pertinent English-language articles on ibutilide. Key search terms included ibutilide, AF, AFl, cardioversion, and sinus rhythm. The MEDLINE search was supplemented by references included in the bibliographies of comprehensive review articles and studies.

STUDY SELECTION

Studies and review articles describing the chemistry, pharmacology, and pharmacokinetics of ibutilide were selected. All abstracts and published clinical trials evaluating the efficacy and safety were reviewed.

DATA EXTRACTION

Pertinent information on the pharmacology and mechanism of action of ibutilide was summarized. Data were extracted from the clinical trials describing trial design, patient population, interventions, methods of evaluation, outcomes, and statistical significance.

DATA SYNTHESIS

Ibutilide is a Vaughan-Williams class III antiarrhythmic agent approved for intravenous use for the rapid termination of recent-onset AF or AFl. The drug is extensively metabolized by the liver, has a volume of distribution of 11-15 L/kg, is 40% protein bound, and has an elimination half-life of 6 hours (range 2-12). Data from two placebo-controlled trials demonstrated the efficacy of ibutilide for converting AF or AFl of short duration (< or = 90 d) to normal sinus rhythm. A third placebo-controlled trial demonstrated efficacy in patients who developed AF or AFl following cardiac surgery. Comparative trials with procainamide and sotalol have shown at least similar and perhaps superior efficacy with ibutilide. There are no comparative trials with other antiarrhythmic drugs or with direct current cardioversion (DCC). In 586 clinical trial patients receiving ibutilide, the most significant adverse effect was the development of torsade de pointes in 25 patients (4.3%) including 10 cases (1.7%) in which the rhythm was sustained. All cases of torsade de pointes were terminated electrically and none resulted in death or severe morbidity. No prospective cost-effectiveness studies are available; however, results from two decision models suggest that ibutilide may have advantages over other drugs and first-line electrical cardioversion.

CONCLUSIONS

Ibutilide appears to be an effective alternative method for rapid conversion of recent-onset AF or AFl. The drug may be particularly useful in patients who have undergone recent cardiac surgery or those who are not ideal candidates for DCC. Although studies suggest that the risk of proarrhythmia and in particular torsade de pointes is relatively low, caution is advised until additional experience is gained in clinical practice.

Predictors of primary atrial fibrillation and concomitant clinical and hemodynamic changes in patients with chronic heart failure: a prospective study in 344 patients with baseline sinus rhythm

OBJECTIVES

This study investigated the incidence, predisposing factors and significance of the onset of atrial fibrillation (AF) in patients with chronic congestive heart failure (CHF).

BACKGROUND

The association between CHF and AF is well documented, but the factors that predispose to the onset of the arrhythmia and its impact remain controversial. Methods. We prospectively followed up 344 patients with CHF and sinus rhythm (SR). Over a period of 19 +/- 12 months (mean +/- SD), 28 patients developed atrial fibrillation (AF), which became chronic in 18.

RESULTS

At baseline, no differences were found in any clinical and hemodynamic variables between patients who developed chronic AF and those who did not. Reversible AF occurring during follow-up and lower mitral flow velocity at atrial contraction as detected at the last evaluation in SR were independent predictors of the subsequent development of chronic AF. When AF occurred, New York Heart Association functional class worsened (from 2.4 +/- 0.5 to 2.9 +/- 0.6, p = 0.0001), peak exercise oxygen consumption declined (from 16 +/- 5 to 11 +/- 5 ml/kg per min, p = 0.002), cardiac index decreased (from 2.2 +/- 0.4 to 1.8 +/- 0.4, p = 0.0008), and mitral and tricuspid regurgitation increased (from grade 1.8 +/- 1.1 to grade 2.4 +/- 1.4, p = 0.0001 and from grade 1.0 +/- 1.2 to grade 1.8 +/- 1.2, p = 0.001, respectively). Systemic thromboembolism occurred in 3 of the 18 patients with AF. Nine of 18 patients died after AF, and the occurrence of AF was a predictor of major cardiac events.

CONCLUSIONS

In patients with CHF, reversible AF and reduction of left atrial contribution to left ventricular filling predict the subsequent development of chronic AF. The onset of AF is associated with clinical and hemodynamic deterioration and may predispose to systemic thromboembolism and poorer prognosis.

The peri-operative management of atrial fibrillation

Atrial fibrillation is a common arrhythmia frequently seen in surgical patients. The onset of new atrial fibrillation during the peri-operative period is less common. There are many possible precipitating factors, although volatile agents themselves may have an antifibrillatory action. The management of atrial fibrillation includes removal of any precipitating factors and treatment of the arrhythmia itself. Immediate management of acute-onset atrial fibrillation is usually direct current cardioversion. Alternatively, anti-arrhythmic drugs can be used to achieve cardioversion. In patients with rapid, chronic atrial fibrillation or those refractory to cardioversion, priority is given to control of the ventricular rate. Thrombo-embolism is a significant risk if atrial fibrillation is paroxysmal or persists for more than 48 h.

Evaluation and management of atrial fibrillation in the emergency department

AF is the most common sustained cardiac arrhythmia. Recognition and appropriate management of AF is important to optimize care of concurrent medical problems and prevent long-term consequences. DC cardioversion under sedation should be performed in patients with pulmonary edema, angina, or hypotension. Ventricular rate control is the first choice in stable patients with rapid ventricular rate. Anticoagulation should be considered in all patients with AF duration < 48 hours, except for those under 65 years old and having no other risk factors of stroke. Recent data imply that early attempts at cardioversion may increase success rates and decrease AF recurrence rates. Thus, transesophageal echocardiogram-guided early cardioversion may become more widely used.

Atrial fibrillation: a review of mechanism, etiology, and therapy

The prevalence of elderly individuals in the populations of developed countries is increasing rapidly, and atrial fibrillation (AF) is quite common in these elderly patients: currently, 11% of the U.S. population is between the ages of 65 and 85 years; 70% of people with AF are between the ages of 65 and 85 years. AF causes symptoms secondary to hemodynamic derangements that are the result of increased ventricular response and loss of atrial booster function. AF can lead to reversible impairment of left ventricular function, cardiac chamber dilatation, clinical heart failure, and thromboembolic events. AF requires treatment in order to prevent these potential complications. Type Ia, Ic, and III antiarrhythmics are capable of converting AF to normal sinus rhythm (NSR). Amiodarone has the greatest efficacy and safety for converting AF and maintaining NSR while digoxin and verapamil are ineffective in restoring NSR. Quinidine, flecainide, disopyramide, and sotalol have also been shown to maintain NSR after conversion of AF. Proarrhythmia is a definite concern with the latter four agents. Alternative therapy for AF includes anticoagulation with warfarin or aspirin for the prevention of thromboembolic events, and a variety of agents to control the ventricular response. All medications used to treat AF carry significant risks in the elderly, whether from proarrhythmia, overdosing because of compliance errors, or hemorrhage secondary to anticoagulation. Treatment of AF must be based on a careful risk-benefit evaluation. The physician must know the capability of the particular patient as well as drug mechanisms and effects in the elderly. The decision to convert patients from AF to NSR or to leave the patient in AF and control the ventricular response represents a complex intellectual challenge. Factors favoring one or the other of these two clinical strategies are discussed. Multicenter clinical trials, for example, the Atrial Fibrillation Follow-up Investigation Rhythm Management (AFFIRM) trial, are currently underway to assess various clinical strategies for maintenance of NSR following conversion from AF. Amiodarone is one of the drugs under investigation.

Dilemmas in the acute pharmacologic treatment of uncontrolled atrial fibrillation

A recently conducted observational study of the prehospital treatment of uncontrolled atrial fibrillation brought to light therapeutic inconsistencies by emergency providers in dealing with this dysrhythmia. A review of the literature suggests that digoxin lacks efficacy in controlling ventricular rate in atrial fibrillation and that the slow onset of digoxin makes its use in the emergency setting questionable. Because of their demonstrated ability to rapidly slow ventricular rate, the calcium channel blocker, diltiazem, or the beta-adrenergic blocker, esmolol, should be the preferred agents for treating rapid atrial fibrillation in the emergency department or the paramedic ambulance.

Emergency management of atrial fibrillation and flutter: intravenous diltiazem versus intravenous digoxin

STUDY OBJECTIVE

To compare the effects of i.v. diltiazem and i.v. digoxin on ventricular rate control in the emergency treatment of acute atrial fibrillation and flutter (AFF).

METHODS

This prospective, randomized, open-label trial involved 30 consecutive patients who presented with acute AFF to the emergency department of an urban, 420-bed community teaching hospital from April 1993 through March 1994. Exclusion criteria included systolic blood pressure lower than 100 mm Hg, treatment with calcium-channel blockers other than diltiazem, lack of informed consent, and objection of the private physician. Patients were randomly assigned to receive either i.v. diltiazem alone, i.v. digoxin alone, or both. Heart rate control was defined as a ventricular rate of less than 100 beats/minute. I.v. digoxin, 25 mg, was given as a bolus at time 0 and at time 30 minutes. An initial dose of .25 mg/kg diltiazem was given intravenously over the first 2 minutes, followed by a dose of .35 mg/kg at time 15 minutes and then a titratable i.v. infusion at a rate of 10 to 20 mg/hour to maintain heart rate control. The dosing regimens were the same whether the drugs were given alone or in combination. Heart rhythm, heart rate, and blood pressure were measured at time 0, 5, 10, 15, 30, 60, 120, and 180 minutes. Statistical significance was assessed with the use of Student's t test and ANOVA methodology.

RESULTS

At time 0, the heart rate (mean +/- SD) was 150 +/- 19 beats/minute in the diltiazem group and 144 +/- 12 in the digoxin group (difference not significant, P = .432). The decrease in heart rate from time 0 reached statistical significance at time 5 minutes in the diltiazem group (P = .0006); the mean rates at time 5 minutes were 111 +/- 26 beats/minute for diltiazem and 144 +/- 13 for digoxin. The decrease in heart rate achieved with digoxin did not reach statistical significance until time 180 minutes (P = .0099), at which time the rates were 90 +/- 13 for diltiazem and 117 +/- 22 for digoxin.

CONCLUSION

Treatment of acute AFF with i.v. diltiazem decreases ventricular heart rate significantly within 5 minutes, compared with 3 hours for treatment with i.v. digoxin. No advantage was noted within 3 hours for i.v. treatment with a combination of diltiazem and digoxin. I.v. diltiazem is superior to i.v. digoxin in the emergency control of ventricular rate in acute AFF and should be considered as a drug of choice for this condition. This study was not large enough to adequately assess adverse effects, and further studies may be warranted for clinical validation.

Predictors of atrial fibrillation after coronary artery surgery. Current trends and impact on hospital resources

BACKGROUND

Atrial fibrillation (AF) after coronary artery bypass surgery (CABG) is the most common sustained arrhythmia. Its pathophysiology is unclear, and its prevention and management remain suboptimal. The aim of this prospective study was to determine the current incidence of AF, identify its clinical predictors, and examine its impact on resource utilization.

METHODS AND RESULTS

Over a 12-month period ending July 31, 1994, a CABG procedure was performed on 570 consecutive patients (age range, 32 to 87 years; median age, 67 years; 232 [41%] were > or = 70 years; 175 [31%] were women; 173 [30%] were diabetics; 364 [65%] required nonelective surgery; 86 [15%] had had a prior CABG; and 86 [15%] had had prior percutaneous transluminal coronary angioplasty). AF occurred in 189 patients (33%). The median age for patients with AF was 71 years compared with 66 for patients without (P = .0001). Multivariate logistic regression analysis (odds ratio, +/- 95% CI, P value) was used to identify the following independent predictors of postoperative AF: increasing age (age 70 to 80 years [OR = 2; CI, 1.3 to 3; P = .002], age > 80 years [OR = 3; CI, 1.6 to 5.8; P = .0007]), male gender (OR = 1.7; CI, 1.1 to 2.7; P = .01), hypertension (OR = 1.6; CI, 1.0 to 2.3; P = .03), need for an intraoperative intraaortic balloon pump (OR = 3.5; CI, 1.2 to 10.9; P = .03), postoperative pneumonia (OR = 3.9; CI, 1.3 to 11.5; P = .01), ventilation for > 24 hours (OR = 2; CI, 1.3 to 3.2; P = .003), and return to the intensive care unit (OR = 3.2; CI, 1.1 to 8.8; P = .03). The mean length of hospital stay after surgery was 15.3 +/- 28.6 days for patients with AF compared with 9.3 +/- 19.6 days for patients without AF (P = .001). The adjusted length of hospital stay attributable to AF was 4.9 days, corresponding to > or = $10 055 in hospital charges.

CONCLUSIONS

AF remains the most common complication after CABG and consequently is a drain on hospital resources. Concerted efforts to reduce the incidence of AF and the associated increased length of stay would result in substantial cost saving and decrease patient morbidity.

Atrial fibrillation, anticoagulation, and stroke

There is a demonstrated statistical association between atrial fibrillation, rheumatic valvular disease, and embolic stroke. This article assesses the results of 6 major clinical trials (AFASAK, BAATAF, SPINAF, SPAF [parts I and II], CAFA and EAFTA--see text for trial names). Multivariate analysis revealed 4 independent clinical features that identified patients with atrial fibrillation at an increased risk for stroke: hypertension, increasing age, previous transient ischemic attack, and diabetes mellitus. Without anticoagulation therapy, patients with any of these risk factors had a 4% annual risk of stroke. Patients with cardiac disorders such as congestive heart failure and coronary artery disease have a stroke rate 3 times higher than patients without any risk factors; patients with atrial fibrillation but no concomitant risk factors or structural heart disease seemed to have little concomitant risk for stroke. Meta-analysis revealed a 64% reduction of risk for stroke in patients treated with warfarin, as compared with placebo. The value of warfarin therapy in patients > 75 years old is less clear because of a high risk of hemorrhagic complications.

Newer developments in the management of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice. Unlike reentrant supraventricular tachycardia and malignant ventricular tachyarrhythmias, for which highly effective and safe nonpharmacologic therapies are available, the treatment of AF remains controversial and often problematic. Whereas electrical cardioversion restores sinus rhythm in most patients with AF, the maintenance of sinus rhythm often requires membrane-active antiarrhythmic drugs that may increase mortality by inducing ventricular proarrhythmia. The control of ventricular response rate, often associated with oral anticoagulation to prevent thromboembolic complications, is an alternative strategy in AF management. The relative efficacy and risks of these strategies and their respective role in different patient subgroups remain to be established. This article focuses on newer developments in the management of AF, including prospects for improved methods to maintain sinus rhythm, newer approaches to rate control, controversies regarding the use of oral anticoagulation, and novel nonpharmacologic therapies. These newer developments may lead over the next 10 years to a revolution in the management of AF as profound as that produced over the last 10 years by nonpharmacologic therapy of other arrhythmias.

Contemporary management of atrial fibrillation

The incidence of atrial fibrillation approximately doubled for every 10-year increment in age in the Framingham Heart Study cohort; thus physicians will be faced with an increasing patient population with atrial fibrillation. Hypertension is observed to be the most common associated risk factor in both sexes. The management of patients with atrial fibrillation is evolving as a result of a number of published studies. Calcium channel blockers and beta-blockers are emerging as the preferred choices for rate control rather than digoxin. Low-dose anticoagulation therapy has shown beneficial effects not only in primary prevention, but also for secondary prevention of thromboembolism. Thus, patients who cannot be successfully cardioverted should be anticoagulated if there are no contraindications (Table 3) and if they do not fall into the low-risk group--defined as patients under the age of 65 without risk factors (hypertension, diabetes, previous stroke). Patients not eligible for anticoagulation should be on aspirin therapy. Patients with lone atrial fibrillation are not at higher risk for thromboembolism than the general population; therefore, they can be managed without anticoagulation or antiplatelet therapy. Antiarrhythmic treatment should be approached cautiously; amiodarone in low doses is the most effective and safe treatment, but this remains controversial.

Cardiac arrhythmia diagnosis

Cardiac dysfunction is often manifested as arrhythmia, with disruption of the normal periodicity and regularity of electromechanical activity. Cardiac arrhythmias, or abnormalities of cardiac rhythm, are associated with a diverse group of conditions, including congenital, metabolic, structural, physiological, and immunological, and infectious abnormalities. Dysarrhythmia may also be classified as primary because of endogenous electrical abnormalities, or secondary, because of exogenous influences such as ischemia or adrenergic stimuli. Clinical arrhythmia syndromes begin with a single asymptomatic abnormal complex that is benign, progressing to grouped, sustained complexes associated with worsened symptoms and outcome. Proper diagnosis of arrhythmia reflecting symptomology and outcome is essential in acute cardiac care.

Importance of the time of onset of supraventricular tachyarrhythmias on prognosis of patients with acute myocardial infarction

It is known that left ventricular (LV) function, severity of coronary artery disease, and the presence of ventricular arrhythmias are major determinants of prognosis in patients surviving an acute myocardial infarction (AMI). However, little is known about the relationship between the time of onset of supraventricular tachyarrhythmias (SVTs) and mortality. Therefore, this study was carried out in a 48-months period on 131 patients with AMI who presented with SVT during hospitalization. Of these, 53 patients (40.5%) had arrhythmia within < 12 h of MI, while 78 patients (59.5%) had arrhythmia between 12 h and 4 days. The arrhythmias studied were atrial fibrillation, atrial flutter, and paroxysmal supraventricular tachycardia. The patients were similar for age, gender, coronary risk factors, creatine kinase-MB peak, cardioversion and LV function. Angiographic features for patients with the < 12-h onset of arrhythmia were: 86.7% of the patients had uniarterial lesions, 8.9% had biarterial lesions, and 4.4% had triarterial lesions. Patients with the 12-h-4-day onset had 16.1%, 53.2%, and 30.6% (p < or = 0.05) of the respective lesions. Inferior wall myocardial infarction was more frequent among patients with the earlier onset (60.4%), while patients with the later onset presented more anterior wall infarctions (50.0%). Only 11.3% of the patients with the earlier onset presented with severe in-hospital congestive heart failure (Killip classes III-IV), versus 62.8% of the patients with the later onset (p < or = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Possible drug interaction between warfarin and combination of levamisole and fluorouracil

OBJECTIVE

To report a possible drug interaction between the combination of fluorouracil (5-FU), levamisole, and warfarin.

CASE SUMMARY

An elderly patient with chronic atrial fibrillation and prosthetic valve replacements had been taking warfarin 22.5 mg/wk. Following the diagnosis of colon cancer (Duke's classification D), a chemotherapy regimen of 5-FU and levamisole was started. Within four weeks after initiation of chemotherapy, the International Normalization Ratio (INR) increased from 3.04 to 39.56. Warfarin was discontinued and restarted at 7.5 mg/wk. Discontinuation of levamisole and 5-FU for a five-week period resulted in the INR falling to a subtherapeutic level. Reinstitution of the chemotherapeutic regimen once again led to an increase in INR.

DISCUSSION

A literature search showed no reports of an interaction between warfarin and levamisole. However, prolongation of 5-FU half-life and an increase in INR have been reported with the concurrent use of 5-FU and warfarin. Inhibition of the hepatic metabolism of warfarin by 5-FU and levamisole is the postulated mechanism of this drug interaction.

CONCLUSIONS

This case describes the clinically significant increase of INR in an elderly patient after adding a chemotherapy regimen of levamisole and 5-FU to a previous regimen of warfarin alone. The increasing incidence of both atrial fibrillation and colon cancer with age could potentially require the concomitant use of 5-FU, levamisole, and warfarin. Because of the potential severity of this interaction, close monitoring of INR and warfarin dosage adjustment is recommended in patients receiving warfarin along with levamisole and 5-FU.

A clinical study of intravenous cibenzoline in selected patients with recent-onset atrial tachyarrhythmia

Twenty-five adult patients with sustained atrial tachyarrhythmia (ATA) and without heart failure were treated by intravenous cibenzoline, 1 mg/kg, as a slow bolus infusion, followed by a 8 mg/kg/24 h continuous infusion. Sinus rhythm conversion was observed in 18 patients (72 percent success rate). Severe adverse cardiac events were observed in only one patient (4 percent occurrence rate), as a wide QRS complex tachycardia finally requiring a semiemergency direct-current cardioversion. Two minor side effects were additionally observed. A similar population of 21 patients was conventionally treated with amiodarone, either given intravenously, 15 to 20 mg/kg/24 h, or orally, 30 mg/kg/24 h as a single dose. An identical success rate (15/21; 71 percent) was observed. Our results indicate that in selected patients with ATA, cibenzoline and amiodarone are highly effective for producing sinus rhythm conversion. We suggest that the former drug may be used as a first-line treatment. In case of failure, the latter may constitute an alternative to transthoracic electrical countershock.