The effects of epicardial
lidocaine on
ventricular tachycardia (VT) induced by rapid ventricular pacing (50 Hz) were studied in dogs.
Lidocaine-
polyurethane (28% wt/wt) matrixes (40-50 mg, 5 x 5 mm) were placed proximal to bipolar left ventricular epicardial
electrodes in open-chest anesthetized dogs (n = 9) after VT was established by rapid ventricular pacing. In the first set of experiments, matrices were removed immediately after VT had converted to sinus rhythm. Control animals underwent VT induction protocol with a nondrug-containing matrix positioned next to the epicardial
electrode. In the
lidocaine-treated animals, VT conversion was noted in all animals and occurred after 51.7 +/- 8.9 s (mean +/- SE), with a VT threshold current elevation of 73.5 +/- 11.2% above baseline at the time of conversion which progressed to 259 +/- 44% of the initial value by 5.4 +/- 0.5 min post-matrix placement.
Lidocaine 1.4 +/- 0.1 mg was delivered to the myocardium at the time of VT conversion (0.11 +/- 0.01 mg/kg). In comparison, accelerated VT persisted for 5 min in three of five control animals, and progressed to
ventricular fibrillation (VF) in the other two animals. In a separate series of eight dogs, the
lidocaine-
polyurethane matrixes were left in palce for 4 h so that we could study the sustained antiarrhythmic action of controlled-release
lidocaine on VT induction. The results of these experiments demonstrated a maintenance of the VT threshold elevation at a level of 53.9 +/- 10.8% after 4 h, with a net
lidocaine dose of 0.52 +/- 0.06 mg/kg after 4 h of controlled release.(ABSTRACT TRUNCATED AT 250 WORDS)