HEART RATE VARIABILITY IN CANCER-RELATED FATIGUE
Background
Cancer-related fatigue (CRF) pathophysiology is unclear. Cardiovascular autonomic nervous system (CVANS) dysfunction may contribute. CVANS can be measured by heart rate variability (HRV) and postural hypotension. 
Objective
Investigate CRF and CVANS function in solid tumours. 
Methods 
Treatment-naïve outpatients recruited from medical oncology. Fatigue measured subjectively (brief fatigue inventory [BFI]) and objectively (hand grip strength, timed up and go [TUG] and sit to stand [STS]). BFI ≥3 indicated fatigue. 
HRV was recorded for five minutes each of spontaneous and paced breathing (BioPac Systems MP36™). Analysis was performed using ARTiiFACT™. HRV reported as root mean square of successive differences (RMSSD) and standard deviation of the NN (R-R) intervals (SDNN). Lower SDNN represents loss of dynamic response. Postural hypotension defined as systolic blood pressure (BP) drop of ≥20mmHg or diastolic BP drop of ≥10mmHg on standing.

Results
10 participants (6F)
Age: Median 54 (range 40-73)
Cancer types: Breast 6, Oesophageal 4
Loco-regional disease: 3

	BFI: Median 1.25 (range 0-5.9)
	BFI ≥3: 3/10 (30%)
 
	
	Fatigued
N=3	Non-Fatigued
N=7
	Median (range)	Median (range)
Grip Strength (kg force)	23 (18-33)	35 (14-48)
TUG (s)	8 (7-8)	7 (6-9)
STS (number in 30s)	13 (9-16)	13 (11-18)
RMSSD, spontaneous	16 (6-25)	18 (11-79)
RMSSD, paced	18 (8-71)	23 (17-86)
SDNN, spontaneous	22 (18-27)	30 (17-124)
SDNN, paced	30 (17-96)	45 (28-121)
	Number (%)	Number (%)
Postural BP drop	1/3 (33%)	0/7


Conclusions 
1. Significant proportion of participants fatigued pre-treatment
2. Lower SDNN in fatigued participants indicates CVANS dysfunction
3. Orthostatic hypotension rarely present

03 / HEART RATE VARIABILITY IN CANCER-RELATED FATIGUE