Predictors of class IC antiarrhythmic drugs efficacy in patients with paroxysmal form of atrial fibrillation

Background. Class IC antiarrhythmic drugs (IC-AADs) are recommended as first-line therapy in treatment of lone paroxysmal atrial fibrillation (AF) along with catheter ablation of pulmonary veins. Despite previous attempts to identify predictors of IC-AADs` efficacy, the choice between IC-AADs agents is still most often carried out using empirical approach.Aim. To determine the predictors of IC-AADs ` efficacy in patients with paroxysmal AF in the absence of structural heart disease.Materials and methods. Seventy four patients (22 men, 52 women, average age 65 [57; 70] years) were treated with IC-AADs: 26 patients were prescribed lappaconitine hydrobromide (Al) (allapinin at a dosage of 75 mg/day or allaforte 50100 mg/day), 25 patients were prescribed propafenone (P) 450600 mg/day, 23 patients diethylaminopropionylethoxycarbonylaminophenothiazine hydrochloride (ethacizine, E) 150 mg/day. The average frequency of AF paroxysms was 2 [0.4; 6.25] per month. Patients were divided into 2 groups depending on the effect of AADs.Results. Over a 12 months follow-up IC-AADs therapy was effective in 28 (37.8%) patients (Eff+ group), in the remaining 46 (62.2%) patients AF recurrences or side effects demanding AADs withdrawal were registered (Eff-group). A DC value greater or equal to 5 ms predicted the effectiveness of IC-AADs therapy with 79% sensitivity and 77% specificity (OR 12, 95% CI 3.0749.5, p0.0001). In the Al group the deceleration capacity (DC) value greater or equal to 5.25 ms allowed predicting therapy effectiveness with 86% sensitivity and 100% specificity (OR 7, 95% CI 1.14; 43; p=0.002). In the E group, the DC index was characterized by high sensitivity (80%) and specificity (85%) for a threshold value of 5.9 ms. In case of DC above this value, the probability of E therapy efficacy increased by 22-times (OR 22, 95% CI 1.5; 314; p=0.009). In group P, the DC medians in the Eff+ and Eff- groups did not differ significantly (p=0.821). However, at low DC values (less than 4 ms) P turned out to be the most effective compared to other two IC-AADs: its effectiveness was 50%, which was significantly higher compared to E (0%) and Al (0%) (p=0.046).Conclusion. Estimation of the DC level before starting IC-AADs can make it easier to choose a specific drug from this group and improve treatment results: at DC above 5.2 ms, it is advisable to use Al, at DC6 ms Al or E, at DC less than 4 ms P.