Tong-yuan Zhang, et al. the upper thoracic sympathetic chain (endoscopic thoracic sympathotomy) has proven to be a minimally invasive and effective treatment for which to permanently abolish pal- mar hyperhidrosis, refractory to conservative modalities.2,3 However, from a location where sympathetic fibers that in- nervate the heart and lungs are derived, sympathetic fibers to the exocrine glands of the palms of the hands also arise from the cervicalis and upper thoracic ganglia.4,5 Thus, transection of the upper interganglionic branches may also interrupt the conduction of the heart sympathetic nervous system. Accordingly, a few studies have shown that thoracic sym- pathotomy may influence cardiac and pulmonary function.6-8 The authors of those studies attributed this observation to a change in the activity of the autonomous nervous system, but without convincing evidence. The aim of the study was to investigate the evolution of heart rate variability before and after thoracic sympathoto- my and to assess the effects of the surgery on autonomic nerve system balance. MATERIALS AND METHODS Study population Between January 2007 and August 2009, a prospective study of endoscopic thoracic sympathectomies for palmar hyperhidrosis was undertaken. Twenty patients (12 males and 8 females) with severe bilateral palmar essential hyper- hidrosis (some combined with axillary hyperhidrosis) with a mean age of 22.4 (range, 18-35) years were included in the study. Diagnosis of primary palmar hyperhidrosis was mainly based on case histories and exclusions of secondary hyperhidrosis. Most patients reported childhood onset of excessive sweating of the palms of the hands and exacerba- tion of symptoms during puberty and adolescence. In most cases, symptoms were aggravated by emotional factors and heat. None of the patients was under medication two weeks prior to the study. Surgical procedure Patients were place in the supine position with 30-40° anti- Trendelenburg tilt of the surgical table. Under general anes- thesia with single lumen tracheal intubation, the patient’s arms were abducted to expose the axilla. The procedure was performed with two ports: an 8 mm port at the mid-ax- illary line at the fifth intercostal space for the introduction of telescope, and a 5-10 mm port at the anterior axillary line at the third intercostal space for working instruments. After identification of the second, third and fourth ribs, the parietal pleura were opened with a diathermy hook at the level where the sympathetic chain crossed the ribs. The sympathetic chain was cauterized and transected at the lev- el of R3 and R4, and the communicating rami were gently cauterized and transected completely, leaving the ganglia in position without removal. The lung was inflated after the procedure under direct vision to confirm that it was well ex- panded.9 Monitor the 24-hour Holter ECG To analyze heart rate variability and interpretation, 24-hour Holter Electrocardiobram (ECG) was performed in all pa- tients on two or three days before and on the first day after endoscopic thoracic sympathotomy. A twelve-lead digital ECG recorder equipped with a Holter analyzer (MARS Holter Analysis Workstation, GE MEDICAL SYSTEMS INFORMATION TECHNOLOGIES) was used, with the sampling frequency of 250 Hz. Supraventricular and ven- tricular ectopic beats, as well as artifacts, were identified and manually eliminated from the analysis.10 Long-term time domain and frequency domain variables from 24-hour recordings were analyzed. The time domain variables in- cluded the following: 1) SDNN, standard deviation of all normal R-R intervals over the entire 24-hour recording; 2) SDANN, standard deviation of the average normal R-R in- terval for all 5-min segments of a 24-hour recording; 3) root mean square differencer (rMSSD), the square root of the mean of the sum of squared differences between adja- cent normal R-R intervals over the entire 24-hour record- ing; and 4) pNN50, the number of adjacent normal R-R in- tervals differing by more than 50 ms, as a percent of the total number of normal R-R intervals. In addition, the fol- lowing frequency domain parameters were analyzed: very low frequency (VLF, 0.003 to 0.04 Hz); low frequency (LF, 0.04 to 0.15 Hz); high frequency (HF, 0.15 to 0.40 Hz); and LF/HF ratio. Statistical analysis The data are expressed as mean±standard derivation (SD). Statistical software SPSS version 13.0 (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses. Comparisons of heart rate variability before and after surgery were per- formed using two-tailed, paired-Student’s t-tests. p-values of <0.05 were considered statistically significant. 1082 Yonsei Med J http://www.eymj.org Volume 53 Number 6 November 2012