J. Janousek et al., USEFULNESS OF PROPAFENONE FOR SUPRAVENTRICULAR ARRHYTHMIAS IN INFANTSAND CHILDREN, The American journal of cardiology, 72(3), 1993, pp. 294-300
The relation between propafenone dose, serum level, electrocardiograph
ic parameters, antiarrhythmic drug efficacy and adverse effects was st
udied in 47 children with symptomatic supraventricular arrhythmias age
d 1 day to 10.3 years (median 2.2 months) with a mean follow-up of 14.
3 months. Propafenone trough serum levels were measured using gas chro
matography. Oral propafenone (mean dose 353 mg/m2/day) was effective i
n 41 of the 47 patients (87.2%). Serum levels did not differ between p
atients responding and not responding to propafenone (0.45 +/- 0.40 vs
0.36 +/- 0.41 mg/liter). PR interval and QRS complex duration increas
ed more significantly with propafenone dose increments (p <0.001), tha
n with propafenone serum levels (p <0.05). At successful treatment PR
interval and QRS complex were prolonged by a mean of 19.2 and 20.5% co
mpared with pretreatment status. Five patients exhibited unexpected ma
rked QRS complex prolongation (50 to 200%) despite low propafenone dos
age (<300 mg/m2/day) and level ranging from 0.05 to 1.33 mg/liter. Thr
ee patients (6.1%) were suspected of being ''poor'' metabolizers of pr
opafenone. Mild chronic elevation of serum liver enzymes was observed
in 5 patients treated with a larger dose (mean 448 mg/m2/day, p <0.001
). No proarrhythmia was noted on serial Hotter monitors. One patient w
ith Wolff-Parkinson-White syndrome and a normal heart had cardiac arre
st after aspiration. Serial monitoring of PR interval and QRS complex
duration was more useful for proper dosage adjustment than propafenone
serum levels. Serum liver enzymes should be closely monitored when us
ing higher propafenone doses. Malignant proarrhythmia could not be exc
luded in the 1 patient with cardiac arrest.