PubMed · 14068382
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E M VAUGHANWILLIAMS. 1963. FIBRILLATION.. https://doi.org/10.1016/0002-8703(63)90392-2
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BACKGROUND: A variety of antiarrhythmic drugs have been used to prevent recurrence of atrial fibrillation after conversion to sinus rhythm. We performed a systematic review to determine the effect of long-term treatment with those drugs on death, embolisms, adverse effects, and atrial fibrillation recurrence. METHODS: We searched MEDLINE, EMBASE, the Cochrane Library (all up to May 2005), and the reference lists of retrieved articles. We included randomized controlled trials that compared any antiarrhythmic against control (placebo or no treatment) or another antiarrhythmic, for more than 6 months. Postoperative atrial fibrillation was excluded. Two evaluators independently reviewed the retrieved studies and extracted all data. Disagreements were resolved by discussion. All results were calculated at 1 year of follow-up. RESULTS: Forty-four trials were included, with a total of 11 322 patients. Several class IA (disopyramide phosphate, quinidine sulfate), class IC (flecainide acetate, propafenone hydrochloride), and class III (amiodarone, dofetilide, sotalol hydrochloride) drugs significantly reduced recurrence of atrial fibrillation (number needed to treat, 2-9), but all increased withdrawals due to adverse effects (number needed to harm [NNH], 9-27) and all but amiodarone and propafenone increased proarrhythmia (NNH, 17-119). Class IA drugs, pooled, were associated with increased mortality compared with controls (Peto odds ratio, 2.39; 95% confidence interval, 1.03-5.59; P = .04; NNH, 109). No other antiarrhythmic showed a significant effect on mortality compared with controls. We could not analyze other outcomes because data were lacking. CONCLUSION: Class IA, IC, and III drugs are effective in maintaining sinus rhythm but increase adverse effects, and class IA drugs may increase mortality.
Arrhythmias are potentially life-threatening problems in the fetus and newborn. Appropriate management depends on accurate diagnosis. Atrioventricular re-entry is the most common type of supraventricular tachycardia in both the fetus and newborn. It should be distinguished from other types of tachycardia - such as atrial flutter, atrial ectopic tachycardia, permanent junctional re-entry tachycardia, and ventricular tachycardia. Neonatal and fetal bradycardias are less common clinical problems. Sustained bradycardia is most often caused by complete atrioventricular block. It can be mimicked by the more common but benign occurrence of non-conducted atrial premature beats.
Cytochrome P450 2D6 (CYP2D6) metabolizes approximately one-third of the medicines in current clinical use and exhibits genetic polymorphism with interindividual differences in metabolic activity. To precisely investigate the effect of CYP2D6*10B and CYP2D6*36 frequently found in Oriental populations on mexiletine metabolism in vitro, CYP2D6 proteins of wild-type (CYP2D6.1) and variants (CYP2D6.10 and CYP2D6.36) were heterologously expressed in yeast cells and their mexiletine p- and 2-methyl hydroxylation activities were determined. Both variant CYP2D6 enzymes showed a drastic reduction of CYP2D6 holo- and apoproteins compared with those of CYP2D6.1. Mexiletine p- and 2-methyl hydroxylation activities on the basis of the microsomal protein level at the single substrate concentration (100 microM) of variant CYP2D6s were less than 6% for CYP2D6.10 and 1% for CYP2D6.36 of those of CYP2D6.1. Kinetic analysis for mexiletine hydroxylation revealed that the affinity toward mexiletine of CYP2D6.10 and CYP2D6.36 was reduced by amino acid substitutions. The Vmax and Vmax/Km values of CYP2D6.10 on the basis of the microsomal protein level were reduced to less than 10% of those of CYP2D6.1, whereas the values on the basis of functional CYP2D6 level were comparable to those of CYP2D6.1. Although it was impossible to estimate the kinetic parameters for the mexiletine hydroxylation of CYP2D6.36, the metabolic ability toward mexiletine was considered to be poorer not only than that of CYP2D6.1 but also than that of CYP2D6.10. The same tendency was also observed in kinetic analysis for bufuralol 1''-hydroxylation as a representative CYP2D6 probe. These findings suggest that CYP2D6*36 has a more drastic impact on mexiletine metabolism than CYP2D6*10.