A Case of Wide-complex Tachycardia

During tachycardia, atrial overdrive pacing resulted in entrainment of the tachycardia with an AVA response upon cessation of pacing.Similarly, ventricular overdrive pacing resulted in a VAV response on cessation of pacing.A narrow-complex tachycardia was never observed.These findings were in keeping with orthodromic atrioventricular re-entrant tachycardia during ipsilateral bundle branch block (BBB) using a concealed left-sided accessory pathway.Thus ipsilateral BBB was necessary for induction and maintenance of the SVT, which was manifested as a wide-complex tachycardia because of ipsilateral BBB.