The treatment of atrial fibrillation: pharmacologic and nonpharmacologic strategies

Rate Control Strategy Elevated To Primary Treatment For Atrial Fibrillation: Has The Last Word Already Been Spoken?

In the last decade, we were able to see the light shed by several trials and observational studies that dealt with the appropriate manner of treating patients with atrial fibrillation (AF). Recently the AF management by cardiologists has become more aggressive, in part because of an improved comprehension of this rhythm disturbance, as well as, the availability of new treatment strategies. Increasing awareness of AF as a disease rather than as an acceptable alternative to sinus rhythm has led to search for clear arguments to support a certain strategy as a gold standard. In this respect, the decision of whether to restore sinus rhythm, or to control the ventricular rate and allow AF to persist is of critical importance. The results of randomized, controlled trials addressing this matter shed some light on the proper way of treatment for these AF patients. The AFFIRM and RACE trials and their respective sub-studies showed surprising results. The vast majority of physicians were surprised to learn that the rate control strategy was elevated to the position of primary treatment for the AF management instead of the all-time recognized rhythm control approach to restoration and maintenance of sinus rhythm. The use of anticoagulants in the trials was different in the treatment strategies. There was a greater anticoagulant use in the rate control arm because of the belief that anticoagulation can be discontinued in the rhythm control arm when sinus rhythm was restored and maintained for one month. On the other hand, only pharmacological agents were used to maintain sinus rhythm in those trials, however, there is increasing evidence that AF ablation can restore and maintain sinus rhythm in a great proportion of patients. Indeed, there are some limitations and several interesting aspects of these trials and other studies that will be discussed. The last word has not been spoken yet.

[Severe bacterial infection: increased mortality in elderly women with low body weight taking drugs prolonging the QTc interval]

AIMS

Women have a higher risk of acquired long QT syndrome which could be of vital importance in severe bacterial infections when macrolides or fluoroquinolones are administered. This study evaluated whether age, drugs prolonging the QTc interval and body weight were additional influencing factors on mortality in the critically ill with respect to gender.

METHODS

In an exploratory investigation 204 intensive care unit (ICU) patients (78 f, 126 m, 61.1±16.1 years) with severe bacterial infections were studied (mortality probability model II(0) 49.1±28%). Antibiotic therapy was carried out following standard guidelines. In 65.2% of patients potentially QTc prolonging drugs were administered for ≥48 h. Body weight was ascertained on ICU admission.

RESULTS

By comparable severity of illness and comparable effect of antibiotic therapy, age, QTc prolonging drugs and less body weight showed significant effects on survival in women (p<0.001, 0.008 and 0.009, respectively). For women mortality increased with age ≥60 years (p=0.01). The division between survival versus non-survival was intensified by addition of QTc prolonging medication and body weight. As such a best risk assessment in women was achieved if age, QTc prolonging therapy and less body weight were combined (p<0.001). In a direct comparison to men, women with at least two of these factors had a significantly poorer outcome (OR 2.37; 95% CI 1.13-4.98; p=0.022).

CONCLUSIONS

Age, QTc prolonging drugs and lower body weight can additionally increase mortality in critically ill women. If negative outcome is attributed to a higher dosage, an adjustment for body weight must be carried out. Until now it should be considered whether it would be better to replace QTc prolonging antibiotics in routinely performed drug alternation in elderly lean women.

New pharmacological strategies for the treatment of atrial fibrillation

Atrial fibrillation (AF) is a growing clinical problem, increasing in prevalence as the population of the United States and countries around the world ages. Intensive research aimed at improving prevention, diagnosis, and treatment of AF is ongoing. Although the use and efficacy of catheter ablation-based approaches in AF treatment have increased significantly in the last decade, pharmacological agents remain the first-line therapy for rhythm management of AF. Currently available anti-AF agents are generally only moderately effective and associated with extracardiac toxicity and/or a risk for development of life-threatening ventricular arrhythmias. Included among current investigational strategies for improving the effectiveness and safety of anti-AF drugs is the development of (1) Agents that produce atrial-specific or predominant inhibition of I(Kur), I(K-ACh), or I(Na); (2) "Upstream therapies" that effect nonion channel targets that reduce atrial structural remodeling, hypertrophy, dilatation, inflammation, oxidative injury, etc; (3) Derivatives of "old" anti-AF drugs with an improved safety pharmacological profile; and (4) Gap junction therapy aimed at improving conduction without affecting sodium channels. This review focuses on new pharmacological approaches under investigation for the treatment of AF.

Non-antiarrhythmic agents for prevention of postoperative atrial fibrillation: role of statins

PURPOSE OF REVIEW

Atrial fibrillation is the most common arrhythmia following cardiac surgery, having both serious medical and socioeconomic consequences. Although there are established antiarrhythmic agents for preventing and treating postoperative atrial fibrillation, these therapies are neither 100% reliable, nor without risks and limitations. Thus, there remains a strong need for non-antiarrhythmic, adjunctive therapies for the prevention of postoperative atrial fibrillation.

RECENT FINDINGS

Long-term statin administration in ambulatory patients is associated with a reduced risk of adverse cardiovascular events, including death, myocardial infarction, stroke, renal dysfunction and atrial fibrillation. Recent evidence suggests, however, that statins may also reduce the risk of acute adverse outcomes following invasive procedures, including postoperative atrial fibrillation. Although the exact mechanisms by which statins may reduce postoperative atrial fibrillation are unclear, accumulating evidence suggests that statins exert multiple effects independent of their effect on LDL cholesterol. For example, in patients with acute coronary syndromes, statin therapy has been shown to modulate remodeling of the cardiac extracellular matrix and to reduce markers of inflammation, including C-reactive protein, serum amyloid A, tumor necrosis factor-alpha, and IL-6.

SUMMARY

Perioperative statin therapy may represent an important non-antiarrhythmic, adjunctive therapeutic strategy for the prevention of postoperative atrial fibrillation.

Long QT syndrome caused by noncardiac drugs

Numerous medications not intended for cardiac use (including antibiotics, histamine blockers, and antipsychotic medications) incidentally block potassium channels in myocardial cells, prolong the QT interval, and may trigger malignant arrhythmias. Although the odds for a given patient for developing arrhythmias are small, the number of patients receiving such drugs is enormous. Most patients developing proarrhythmia have additional risk factors that could be easily identified from their medical history. The list of risk factors includes female gender, organic heart disease, hypokalemia, and a history of long QT or drug-induced arrhythmias. Patients without risk factors are at very low risk. For these patients, it is neither practical nor necessary to record an electrocardiogram before therapy is initiated and the most important preventive measure is to avoid concurrent administration of 2 or more drugs that prolong the QT interval or administration of a medication that impairs the metabolism of a QT-prolonging drug. We performed a computerized literature search using the key words "long QT," "torsade," "drug-adverse effects," and "drug-ventricular arrhythmias," searching for published reports of drug-induced torsade de pointes. The references in each of these reports also were reviewed to identify additional publications. In addition, we reviewed the published reviews and the Internet sites dealing with drug-induced arrhythmias. All the original articles quoted in these reviews and Web sites were examined critically.

Cardioversion of atrial fibrillation with ibutilide: when is it most effective?

BACKGROUND

Atrial fibrillation (AF) is found in 1% of persons above the age of 60 years. More than 5% of the population older than 69 years and about 14% of octogenarians are at risk for this arrhythmia. It is estimated that 1.5 to 3 million persons in the United States alone suffer from AF. The public health implications and attendant morbidity are a significant drain on our health care system.

HYPOTHESIS

The purpose of this study was to determine the clinical and echocardiographic predictors of success in converting AF of > or = 24 h duration.

METHODS

Demographic and clinical and echocardiographic parameters of 101 patients with recent onset AF (> 24 h) who received ibutilide were studied.

RESULTS

Of 101 patients, 56 (55%) converted to sinus rhythm. Age, gender, hypertension, diabetes mellitus, left ventricular ejection fraction (< or = 35%), congestive heart failure, and previous medication for rate control had no significant effect on the conversion rate. Conversion rate was only 30% (9/30 patients) in the presence of an enlarged left atrium (LA > or = 5 cm) and 37.7% (23/61 patients) in the presence of mitral valve disease (MVD), whereas the conversion rate was 82.5% (33/40 patients) in the absence of MVD and 85% (29/34 patients) in the absence of both enlarged LA and MVD (p = <0.001). Patients with coronary artery disease (CAD) also exhibited a significantly greater response to ibutilide than patients without CAD (77 vs. 46%, p-value 0.005).

CONCLUSION

As a therapy for cardioversion of AF, ibutilide is most effective in a selected subgroup patients, such as in patients with CAD and in patients without MVD and/or markedly enlarged left atrium.

[The efficacy of scheduled cardioversion in atrial fibrillation. Comparison of two schemes of treatment: electrical versus pharmacological cardioversion]

INTRODUCTION AND OBJECTIVES

Atrial fibrillation is an arrhythmia with high morbidity and mortality. Restoring sinus rhythm is one of the principle objectives in its management. The present study aimed to assess the efficacy of scheduled cardioversion on atrial fibrillation by comparing two different therapeutic approaches: electrical vs. pharmacological cardioversion.

PATIENTS AND METHOD

Two hundred thirty patients with atrial fibrillation of more than 48 hours duration and requiring sinus rhythm restoration were included. One hundred forty-four patients underwent external electrical cardioversion and 86 patients received quinidine. We analyzed the rate of success, duration of hospital stay, complications and clinical and echocardiographic variable that might predict success.

RESULTS

Sinus rhythm was restored in 181 of 230 patients (79%). The rate of success was 77% (111/144 patients) in the electrical group and 81% (70 of 86 patients) in the pharmacological group (ns). In 13 pharmacological group patients for whom the first attempt failed attempt, a second attempt with electrical cardioversion was made and was successful in 8 patients (61%). No embolic complication was recorded and only two electrical disturbances were seen. Only atrial fibrillation lasting less than 8 weeks was associated with a higher success rate (p < 0.01).

CONCLUSIONS

Scheduled cardioversion in atrial fibrillation is an effective technique with a high success rate and a very low rate of complication. Electrical cardioversion and pharmacological cardioversion with quinidine are similarly effective, although the latter involves a longer hospital stay.

Prevention of ventricular arrhythmias in the congenital long QT syndrome

Life-long therapy is necessary for patients with symptomatic long QT syndrome to prevent arrhythmic death. The merits and limitations of the different therapeutic modalities are discussed. beta-blockers remain the mainstay of therapy, but this medication may not be sufficient for cardiac arrest survivors and for those with the LQT3 genotype. "Genotype-specific" therapy, like potassium-channel openers for patients with inadequate potassium outflow (LQT1 and LQT2 genotypes) or sodium-channel blockers for patients with excessive sodium inflow (LQT3), significantly shortens the QT interval, but the effects of these drugs on arrhythmia prevention is less well established. Cardiac pacemakers may be especially beneficial for patients with LQT2 or LQT3 and for those with pause-dependent torsade de pointes. More important is to recognize that device programming for preventing tachyarrhythmias in patients with long QT differs from the standard pacemaker programming. Finally, implantable defibrillators with dual-chamber pacing capability are indicated for patients at high risk for arrhythmic death, including all cardiac arrest survivors.

Long QT syndromes and torsade de pointes

In the long QT syndromes (LQTS), malfunction of ion channels impairs ventricular repolarisation and triggers a characteristic ventricular tachyarrhythmia: torsade de pointes. Symptoms in the LQTS (syncope or cardiac arrest) are caused by this arrhythmia. In congenital LQTS, mutations in the genes encoding for ion channels cause this channel malfunction. Six genotypes (LQT1 to LQT6) have been identified, and attempts are being made to correlate different mutations with clinical signs and specific therapy. In acquired LQTS, channel malfunction is caused by metabolic abnormalities or drugs. The list of drugs that may impair ion-channel function expands continuously. Moreover, attributes that increase the risk for drug-induced torsade (eg, female sex, recent heart-rate slowing, or hypokalaemia) and electrocardiographic "warning signs" are recognised. Recent data suggest that patients with an acquired LQTS have some underlying predisposition to proarrhythmia. Mutations causing "silent" forms of congenital LQTS, in which the patient remains free of arrhythmias until exposed to drugs that further impair repolarisation, are now recognised.

Electrophysiological imaging of the right atrium using a noncontact multielectrode cavitary probe: study of normal and abnormal rhythms

Cavitary electrograms previously were measured from multiple directions simultaneously in the canine left ventricle with the use of noncontact multielectrode probes. The objective of the present study was to measure cavitary electrograms in the canine right atrium (RA) and describe the corresponding global activation sequences during normal and abnormal atrial rhythms. A 64-electrode custom probe was inserted into the RA of six dogs. Probe position and orientation were guided by fluoroscopy. Probe unipolar electrograms were acquired simultaneously during sinus rhythm, RA pacing, and ventricular pacing. Vagally mediated atrial fibrillation (AF) was induced in four dogs. Probe electrograms were acquired during AF induced at baseline and after intravenous infusion of ibutilide (0.075 mg/kg followed by 0.075 mg/kg infusion over 10 minutes). Isochrone maps were derived from noncontact probe electrograms and were displayed on a beat-by-beat basis during normal and paced rhythms. During AF, maps were displayed for 10 consecutive 100-ms windows. Isochrone maps of normal and paced beats revealed regions of early activation that were consistent with sites of wavefront initiation. During AF, multiple varying activation wavefronts were observed. At baseline, AF cycle length was 110 +/- 15 ms and the number of wavefronts was 1.72 +/- 0.25 per 100-ms window. After ibutilide, AF cycle increased to 182 +/- 36 ms (P = 0.018) and the number of wavefronts decreased to 0.82 +/- 0.14 per 100-ms window (P = 0.009). In conclusion, global electrophysiological imaging with a noncontact multielectrode probe delineates RA anatomy. Furthermore, images of AF activation depict multiple wandering wavefronts. Ibutilide reduces the number of these wavefronts and organizes AF.

Unexpected instant death following successful coronary artery bypass graft surgery (and other clinical settings): atrial fibrillation, quinidine, procainamide, et cetera, and instant death

Primum non nocere. Atrial fibrillation (AF) occurs commonly following coronary artery bypass graft surgery, although new onset atrial fibrillation in this setting is usually transient. When AF reverts or is converted to sinus rhythm it is unlikely to recur, whether or not the patient takes preventive medication. As no benefit (and sometimes increased risk) associated with reduced mortality or morbidity in this setting has been reported for antiarrhythmic agents, standard treatment should consist of observation or control of ventricular response with an appropriate agent until AF relapses to sinus rhythm. If an antiarrhythmic agent, especially a class I agent, is used because of persistent or recurrent AF in the early postoperative period, heart rhythm should be monitored as long as the class I agent is administered and treatment initiated if an undersirable rhythm develops. Atrial fibrillation in other clinical settings in patients with structural heart disease presents a more difficult management problem. Class I agents are reported to be associated with an increased risk of death, despite an efficacious effect of maintaining sinus rhythm. Amiodarone is reported to be well tolerated with respect to the cardiovascular system, but unacceptable noncardiac effects are reported. A safe amiodarone-like agent is greatly needed. Atrial fibrillation in patients with no structural heart disease is not discussed in this presentation.