The electrophysiological effects of
L 9394 (benzoyl-
indolizine), a substance chemically related to
amiodarone, but devoid of
iodine atoms, were investigated by programmed electrical stimulation of the heart in 12 patients with various forms of
tachycardia. Four subjects had electrocardiographic evidence of the
WPW syndrome and episodes of circus movement
tachycardia.
Paroxysmal supraventricular tachycardia, confined to the atrioventricular (AV) node, was found in 3 patients. In 2 cases, where a short PR interval was present, the main complaint was the occurrence of
paroxysmal atrial fibrillation. In the remaining 3 instances, the
arrhythmia consisted of
slow ventricular tachycardia (1 case),
supraventricular tachycardia of the focal type (1 case), and episodes of primary
ventricular fibrillation, not related to acute myocardial ischaemia (1 case).
L 9394 injected intravenously was seen to lengthen the transnodal conduction time as well as the effective and functional refractory periods of the node. Similar effects were found on the retrograde VA pathway. The
drug had no action on the infra-Hisian conduction system, on the refractory periods of ventricular muscle, or on the refractory periods of accessory bypasses. The
drug was injected during an episode of
tachycardia in 6 cases with reproducible supraventricular re-entrant
tachycardia. Three had a
tachycardia circuit confined to the node. In those instances, the
drug had beneficial effects (slowing and interruption of
tachycardia, decrease or abolition of echo zone; loss of ability to induce
tachycardia). In the other 3 cases, an accessory pathway was incorporated in the circuit.
L 9394 interrupted the
tachycardia in 2 instances (by anterograde
AV block), but failed to protect all 3 patients against reinitiation of
tachycardia by premature stimuli. It is concluded that L9394 does not share all the pharmacological properties of
amiodarone and will not replace it in all its indications.