[Effects of carbamazepine on heart conduction in young patients: a serial study using ambulatory ECG]

Carbamazepine (CBZ) is a first-line drug in the treatment of epileptic seizures and neuralgia. CBZ is also a cardioactive drug and sometimes induces sinusal dysfunction or AV conduction defects.

In order to investigate the effect of CBZ on sinus node function and AV conduction, long-term ECG recording (24 hours) and determination of plasma concentration of CBZ were carried out in 10 epileptic patients without heart disorders (5 males and 5 females, mean age 31 years), in the basal state, during steady-state (7th day) and after 30th day of CBZ treatment. The number of total cardiac beats, mean heart rate, P-Q and Q-T interval, sinus-atrial node and atrioventricular dysfunction and intraventricular conduction delay were evaluated.

Plasma CBZ concentration was always in the therapeutic range (5-12 micrograms/ml): 9.5 micrograms/ml in the 7th day and 7.8 micrograms/ml in the 30th day. No significant differences in the number of cardiac beats, or P-Q and Q-T intervals were found; there was no depression of sinus node function nor delay of AV conduction. In the basal state, ectopic supraventricular beats (105 +/- 20/24 hours) were observed in 7 patients and repetitive in five of them. In the first Holter ECG recording during CBZ treatment, a strong reduction of ectopic supraventricular beats (6 +/- 3/24 hours) and disappearance of the bursts was observed. In the second control, when the CBZ concentration was lower, the number of ectopic supraventricular beats were moderately increased (30 +/- 8/24 hours) and in one patient supraventricular tachycardia reappeared.

In young epileptic subjects without signs of heart disease, CBZ seems to have no significant effect on conduction, yet has a possible antiarrhythmic effect.