Norepinephrine induces ventricular arrhythmias originating distal to the His bundle in anesthetized dogs, emphasizing that surface ECG alone is insufficient to determine arrhythmia mechanisms.
May caution against surface ECG-only localization of ventricular arrhythmias during catecholamine surges; leaves open human translation of distal His origins.
Electrograms have been recorded simultaneously from the right atrium, bundle of His, and both ventricles, together with the lead II electrocardiogram in dogs receiving cyclopropane and oxygen. Following the administration of norepinephrine, both bigeminal rhythms and monofocal ventricular tachycardias were observed. 2. In our studies both the coupled and the monofocal ventricular beats originated distal to the His electrode. 3. The mechanism of the coupled beats could not be analyzed using either gross or intracellular recording methods; the monofocal tachycardias appeared to result from increased pacemaker activity in the ventricular conducting system. 4. The present results emphasize the hazards of proposing mechanisms to explain arrhythmias solely on the basis of electrocardiographic evidence.
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Morse et al. (1964) studied this question.
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