Electrocardiographic changes induced by the stellate ganglion block in normal subjects

In order to examine the laterality of the sympathetic control of the human heart, electrocardiographic changes induced by a unilateral stellate ganglion block (SGB) were observed. 10ml of 1% lidocaine was used for the block and post-block ECG was recorded just after the appearance of Horner's sign. Patients who developed vocal hoarseness were excluded. 15 recordings of 14 subjects with right SGB and 16 recordings of 12 subjects with left SGB were used for analysis. A significant increase in the P-P interval from 0.90 +/- 0.17 sec to 0.96 +/- 0.16 sec. was observed only with right SGB and the predominance of the right side in the sympathetic nervous control of the human heart was thus demonstrated. The atrioventricular conduction time was not affected by either the right or left SGB. The QTc was slightly but significantly prolonged only by the right SGB, from 0.40 +/- 0.04 sec. to 0.43 +/- 0.04 sec. This prolongation was not large enough to support a definite conclusion and further investigations should be made.