POM-V
Research type
Research Study
Full title
Vagus nerve function in surgical patients.
IRAS ID
272224
Contact name
Gareth Ackland
Contact email
Sponsor organisation
Queen Mary University of London
Duration of Study in the UK
0 years, 8 months, 0 days
Research summary
Research Summary:
Surgical patients with multiple medical problems who are at most risk of postoperative complications have profound vagus nerve dysfunction. The vagus nerve is important for helping control the speed at which the heart beats. In particular, patients with cardiac vagal dysfunction, which is quantified by higher resting heart rate and delayed heart rate recovery after exercise-testing, are at particularly elevated risk. In the general population, loss of cardiac vagal activity is an independent, robust predictor of cardiovascular morbidity and all-cause mortality. Previous studies show that patients with features of subclinical vagal autonomic dysfunction are most likely to sustain myocardial injury and die after non-cardiac surgery.\n\nIn this project, I will develop a simple test using changes in patients’ heart rate (measured with holter monitors) when they stand up to identify those with poor vagus nerve function. The posture changes elicited by standing from a seated position offers a highly scalable, robust measure of vagal autonomic nervous system function. Heart rate increases rapidly in the first few seconds after standing to counteract the gravitational forces that redistribute blood towards the lower extremities. After standing for 10-20 seconds, vagal activation rapidly reduces heart rate. The slower speed of heart rate recovery 10-20s after standing is associated with a higher risk of long-term mortality.Summary of Results:
A total of 87 participants (mean age: 64 years [95%CI: 61–66]; 48 (55%) females) completed both tests. Mean heart rate change every 10 s for 1 min after peak heart rate after standing and exercise was significantly correlated (R2=0.81; P<0.0001). HRRorthostatic was unchanged in individuals with HRRexercise ≤12 beats min−1 (n=27) but was lower when HRRexercise >12 beats min−1 (n=60; mean difference: 3 beats min−1 [95% confidence interval 1–5 beats min−1]; P<0.0001). Slower HRRorthostatic was associated with lower peak VO2 (mean difference: 3.7 ml kg-1 min−1 [95% confidence interval 0.7–6.8 ml kg-1 min−1]; P=0.039).
Conclusion
Prognostically significant heart rate recovery after exhaustive exercise is characterised by quantitative differences in heart rate recovery after orthostatic challenge. These data suggest that orthostatic challenge is a valid, simple test indicating vagal impairment.REC name
South Central - Oxford B Research Ethics Committee
REC reference
19/SC/0656
Date of REC Opinion
6 Jan 2020
REC opinion
Favourable Opinion