[The acute treatment of supraventricular tachycardia with endovenous amiodarone]. / Trattamento acuto delle tachicardie sopraventricolari con amiodarone endovena.

In the present study we evaluated 35 patients of both sexes, aged 21-84, with newly occurring supraventricular tachyarrhythmias, 19 atrial fibrillation (AF), 6 atrial flutter (FL) and 10 paroxysmal supraventricular tachycardias (PSVT). They were treated with a single amiodarone infusion up to two hours after the restoration of a stable sinus rhythm or to a maximus dose of 2,400 mg (in 24 hours). Plasma amiodarone concentration and QTc were measured at the restoration of sinus rhythm and twelve hours after the amiodarone withdrawal. Amiodarone infusion restored a stable sinus rhythm in all 10 patients of the PSVT group (100%), in 5 of the FL group (83%) and in 16 of the AF group (84%). The average dose needed to stop PSVT was lesser than for AF and FL (M + SE: 473.3 +/- 36.88 vs 1842.1 + 259.6 vs 1548.8 +/- 345.5 mg; p less than 0.001). The average plasma amiodarone concentration at the restoration of sinus rhythm was 2450.4 +/- 175.9 SE ng/ml in all the tachyarrhythmias as a whole without any statistically significant difference among PSVT, FL and AF. Moreover no correlation exists between plasma amiodarone concentrations and the amount of amiodarone infused. QTc showed a statistically significant transient lengthening at the restoration of sinus rhythm, but not twelve hours after amiodarone withdrawal. In conclusion, a single dose of amiodarone is effective and safe in all newly occurring supraventricular tachyarrhythmias, without any important side effect and with a high therapeutic index in pharmacologic cardioversion as alternative treatment to cardioversion.

[Amiodarone and its infusion velocity in recent-onset atrial fibrillation]. / Amiodarone e velocità di infusione nella fibrillazione atriale di recente insorgenza.

Two intravenous amiodarone dosing schedules in 28 patients with atrial fibrillation arisen less than 10 days before, were evaluated. Their effectiveness in converting to sinus rhythm, the incidence of side effects and the relationship between efficacy and plasma concentrations of amiodarone and desethylamiodarone were compared. Schedule A, with amiodarone infusion at a rate of 1.5 mg/kg/h up to two hours after the restoration of sinus rhythm or to a maximum dose of 1200 mg, reverted 86.7% of all patients. Schedule B, with a single amiodarone infusion of 300 mg over 15 minutes, followed by a 300 mg dose maintenance over three hours, reverted 69.2% of all patients. Schedule A was more effective than schedule B (P less than 0.01). Schedule B reverted before A (P less than 0.05). The only transient adverse effects were: superficial phlebitis, symptomatic hypotension and silent QTc lengthening. Amiodarone and desethylamiodarone plasma concentrations were not related to efficacy of the drug in converting sinus rhythm. In conclusion, an intravenous infusion of amiodarone over few hours showed high efficacy (79.6%), wide therapeutic index, good compliance and irrelevant adverse effects in converting patients with recent-onset fibrillation.