Quinidine treatment of chronic lone atrial fibrillation

Appropriate outcome measures in trials evaluating treatment of atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is a widespread disease that has only recently received the focused attention of arrhythmia specialists despite being the most frequently occurring significant cardiac arrhythmia.

METHODS AND RESULTS

The wide variety of trial designs used to evaluate AF treatment is a reflection of the diverse outcomes associated with this condition. The best trials assess the impact of treatment on a clearly measured outcome that is of clinical relevance to patients. This review discusses the different designs of AF treatment trials and analyzes the utility of the various outcomes that can be assessed.

CONCLUSIONS

A sensible goal of AF treatment is to reduce the frequency of recurrences and to prolong the time between them. The most appropriate trials focus on AF recurrences that are symptomatic and therefore relevant to the patient. We still do not know if there is value in AF prevention, beyond preventing symptoms. However, ongoing and future studies will show whether AF suppression reduces the longer-term risks of stroke or death and improves patient quality of life. Cost of care will increasingly be studied in future trials of AF management.

Pharmacologic cardioversion of chronic atrial fibrillation in the goat by class IA, IC, and III drugs: a comparison between hydroquinidine, cibenzoline, flecainide, and d-sotalol

INTRODUCTION

Recently, we reported that repetitive induction of atrial fibrillation (AF) in the goat causes electrical remodeling of the atria leading to the development of sustained AF. The aim of the present study was to compare Class IA, IC, and III drugs in their ability to cardiovert chronic AF in remodeled atria.

METHODS AND RESULTS

In 16 goats with sustained AF, hydroquinidine (HQ), cibenzoline (Ci), flecainide (FI), and d-sotalol (dS) were infused. HQ, Ci, Fl, and dS restored sinus rhythm (SR) in 83%, 91%, 67%, and 92% of the cases, while adverse drug effects occurred in 17%, 36%, 56%, and 8%. Prior to restoration of SR, AF cycle length prolonged by 68%, 103%, 53%, and 20%, respectively. The QRS width increased by 14%, 64%, and 58% (HQ, Ci, and Fl), and remained unchanged by administration of dS. RR intervals were slightly prolonged by HQ, Ci, and Fl, and markedly prolonged by dS (48%). The QT interval was moderately prolonged by HQ, Ci, and Fl, and considerably by dS (34%). QTc was only slightly prolonged by each of the drugs. Directly after cardioversion of AF, the atrial refractory period was 87+/-29 (HQ), 119+/-32 (Ci), 66+/-10 (Fl), and 73+/-18 msec (dS) (control: 146+/-18 msec). Atrial conduction velocity was 85+/-6, 71+/-11, 86+/-12, and 110+/-11 cm/sec compared with a control value of 116+/-10 cm/sec. Because directly after cardioversion the atrial wavelength was still very short (5.7 to 8.4 cm), the vulnerability for AF was still very high, and a single premature beat reinduced AF in 71% (Ci) to 100% (HQ, Fl, and dS) of the cases.

CONCLUSION

In a goat model of sustained AF, Class IA, IC, and III drugs restored sinus rhythm in 67% to 92% of the cases. However, after cardioversion, the atrial wavelength was still abnormally short, and AF was readily inducible in 71% to 100% of the cases.

Cost effectiveness of inpatient initiation of antiarrhythmic therapy for supraventricular tachycardias

This study assessed the cost effectiveness of inpatient antiarrhythmic therapy initiation for supraventricular tachycardias using a metaanalysis of proarrhythmic risk and a decision analysis that compared inpatient to outpatient therapy initiation. A MEDLINE search of trials of antiarrhythmic therapy for supraventricular tachycardias was performed, and episodes of cardiac arrest, sudden or unexplained death, syncope, and sustained or unstable ventricular arrhythmias were recorded. A weighted average event rate, by sample size, was calculated and applied to a clinical decision model of therapy initiation in which patients were either hospitalized for 72 hours or treated as outpatients. Fifty-seven drug trials involving 2,822 patients met study criteria. Based on a 72-hour weighted average event rate of 0.63% (95% confidence interval, 0.2% to 1.2%), inpatient therapy initiation cost $19,231 per year of life saved for a 60-year-old patient with a normal life expectancy. Hospitalization remained cost effective when event rates and life expectancies were varied to model hypothetical clinical scenarios. For example, cost-effectiveness ratios for a 40-year-old without structural heart disease and a 60-year-old with structural heart disease were $37,510 and $33,310, respectively, per year of life saved. Thus, a 72-hour hospitalization for antiarrhythmic therapy initiation is cost effective for most patients with supraventricular tachycardias.

Cardioversion of atrial fibrillation

Cardioversion to sinus rhythm should be considered for all patients in atrial fibrillation in order to improve cardiac performance and perhaps to reduce the long-term risk of thromboembolic complications. Different methods of cardioversion, whether electrical or pharmacological, exist and there is often uncertainty about performing the procedure. In particular, there is often confusion about the use of anti-arrhythmic drugs and the suitable length of anticoagulant therapy required pre- and post-cardioversion. This review discusses the current understanding of electrical and pharmacological cardioversion of atrial fibrillation, the clinical effects and the role of prophylactic anti-arrhythmic and anticoagulant therapy in this procedure.