ALTERATION OF SINUS VARIABILITY AFTER CAR DIAC-SURGERY

Sinus tachycardia is frequent after cardiac surgery and this tachycard ia is probably due to changes of the autonomic nervous system. The obj ective of this study was to evaluate the changes possibly induced by c ardiac surgery, by studying sinus variability (SV) during a 24-hour Ho lter monitoring. The examination was performed in 28 patients who had undergone cardiac surgery 1 to 6 weeks previously. These patients had no alteration of left ventricular function, or any causes likely to mo dify SV and they had a normal postoperative course. Their results were compared to those of 4 subjects developing a postoperative complicati on (1 case of ventricular tachycardia and 3 cases of resuscitated card iac arrest). The results were also compared to those of 24 age-matched adult controls without heart disease (control group). The study of SV included temporal and spectral analysis of SV with measurement of the standard deviation of normal RR intervals (SD), mean heart rate (HR), percentage of RR intervals differing by more than 50 m/sec from the a djacent interval (pNN50), coefficient of variability (CV) (SD/RR), squ are root of the differences between successive RR (rMSSD), spectral pr operties of low frequencies (LF) and high frequencies (HF) and the fra ctionated spectral property (LF/HF). Results: (see tables, page 151 an d 152). An alteration of SV was therefore observed in the surgical gro up, and lasted 4 to 6 months after surgery. No difference was observed between subjects without cardiac events and those presenting a cardia c event. In conclusion : cardiac surgery decreases all parameters of S V during the first few postoperative months. Certain unexpected cardia c accidents during this period could be explained by these changes.