Newly developed systolic murmur in patients with a transvenous pacemaker.

We encountered four cases in which a transvenous cardiac pacemaker produced a systolic musical murmur in the absence of any complications. This systolic murmur appeared only when the pacing was being cut off and disappeared soon after the pacing had been turned on. Although the exact mechanism of production of the murmur remains uncertain, several possible mechanisms for its occurrence are discussed. It is apparent from this study that a systolic murmur can newly occur without any obvious cause in patients with a transvenous pacemaker.