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September 26, 1966

Ventricular Capture in Demand Pacing

Author Affiliations


JAMA. 1966;197(13):1108. doi:10.1001/jama.1966.03110130108039

To the Editor:—  We would like to comment on a letter of Hirsch and Hecht (197:373, 1966) so that no false hopes would be generated prematurely concerning the medical treatment of the disturbing problem of competitive pacing. The authors imply that complete control over the cardiac mechanism was obtained because guanethidine had slowed the sinus rate below the rate of pacing. However, the creation of a state in which the pacing rate is faster than the sinus rate is not necessarily sufficient to abolish competition, whether this condition is achieved by slowing the sinus or accelerating the pacing rate1 (Figure). Indeed, in order to eliminate this parasystolic type of arrhythmia the fastest pacemaker must be able to depolarize and recycle the firing mechanism of the slower one (ie, if the rate of the ventricular pacing is faster than the existing rate, retrograde depolarization of the sinoatrial (SA) node must