To the Editor: I would like to comment on the interesting observations of Greenspon et al.1 and suggest an alternative explanation. From the figures, it would appear that the authors inserted four catheters percutaneously, to record the right atrial, left atrial, and His-bundle electrocardiograms while stimulating the right ventricle. The amount of lidocaine required to produce local anesthesia for insertion of four catheters may result in therapeutic blood concentrations.2 Thus, the first study of electrical stimulation (Figure 1 in their article) could have been performed when the patient had therapeutic or near-therapeutic blood concentrations of lidocaine. The patient had only.
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