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Impairment of cardiovascular autonomic control in patients early after cardiac surgery
R Bauernschmitt1, H Malberg, N Wessel
1Clinic for Cardiovascular Surgery, German Heart Center Munich, Lazarettstr. 36, D-80636 Munich, Germany. bauernschmitt@dhm.mhn.de
Objective:
Impairment of the baroreceptor reflex activity reflects an alteration of the autonomous regulation of the cardiovascular system and has proven to predict fatal outcome in patients after acute myocardial infarction. The following study was performed to analyse the baroreceptor sensitivity, heart rate variability and blood pressure variability in patients early after coronary surgery.
Methods:
Twenty-five male patients undergoing coronary artery bypass were examined in a prospective study; normal values were obtained from healthy volunteers. Arterial pressure signals were recorded from a radial artery catheter for 30 min preoperatively and in short intervals after surgery. Mechanical manipulations and pharmacological interventions were avoided during the sampling periods. Baroreflex function was calculated according to the dual sequence method, heart rate variability and blood pressure variability were calculated including nonlinear methods.
Results:
Initial values of the patients did not differ from healthy volunteers. The strength of baroreflex sensitivity (increase in blood pressure causing a synchronous decrease of heart rate) is low 2 h postoperatively. The number of delayed tachycardic changes of heart rate, which are caused by sympathetic activation, is only moderately reduced as compared to values obtained from healthy volunteers. Heart rate variability is widely unchanged as compared to preoperative values; blood pressure variability showed an increase of low-frequency components, again indicating sympathetic predominance. Nonlinear analyses revealed reduced system complexity at the beginning of the postoperative course.
Conclusion:
Obviously, there is a vagal suppression 20 h after surgery, while the sympathetic tonus works in a normal range. This unbalanced interaction of the autonomous systems is similar to findings in patients after myocardial infarction. The predictive value of these markers has to be elucidated in further clinical studies.
Insights
Early after coronary surgery, baroreceptor reflex activity is impaired, indicating an autonomic imbalance. This vagal suppression and sympathetic predominance early post-surgery may have predictive value for patient outcomes.
Area of Science:
- Cardiovascular physiology
- Autonomic nervous system regulation
- Surgical outcomes research
Background:
- Baroreceptor reflex activity impairment signals altered autonomic cardiovascular regulation and predicts outcomes post-myocardial infarction.
- Understanding autonomic function post-coronary surgery is crucial for assessing patient recovery.
Purpose of the Study:
- To analyze baroreceptor sensitivity, heart rate variability, and blood pressure variability in patients early after coronary artery bypass surgery.
- To compare postoperative autonomic function with preoperative values and healthy volunteers.
Main Methods:
- Prospective study of 25 male patients undergoing coronary artery bypass.
- Arterial pressure signals recorded preoperatively and postoperatively using radial artery catheterization.
- Baroreflex function, heart rate variability, and blood pressure variability analyzed using dual sequence method and nonlinear analyses.
Main Results:
- Baroreflex sensitivity was significantly reduced 2 hours postoperatively.
- Blood pressure variability showed increased low-frequency components, suggesting sympathetic predominance.
- Nonlinear analyses indicated reduced system complexity in the early postoperative period.
Conclusions:
- A significant vagal suppression occurs 20 hours after coronary surgery, with normal sympathetic tone.
- This autonomic imbalance mirrors findings in post-myocardial infarction patients.
- Further clinical studies are needed to determine the predictive value of these markers.
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