Association between Cardiac Output and Cerebral Blood Flow in Older Adults from a General Population of GÅS - Good Aging in Scania Study

Introduction

In healthy adults, 15-20% of cardiac output is distributed to the brain. During aging, absolute cerebral blood flow (CBF) values show significant decline across most parts of the brain, approximately 0.38 ∼ 0.45% per year. CBF decline is suggested to be associated with reduction in neuronal activity and degeneration in microvasculature. However, there was no significant association between global CBF and several vascular risk factors. We examined therefore if Cardiac output, a hemodynamic measure of left ventricular pump capacity, is associated with regional CBF during aging.

Methods

A population based randomised cohort of older adults (n=341), aged 73-87 years (mean 77.4; SD 3.8), took part in a Swedish GÅS study. The regional CBF was examined with arterial spin labelling MRI. The CBF-maps were directly obtained from the MRI-system without any additional processing and regions (ROIs) were positioned upon anatomical preferences. Hemodynamic measures were obtained with Finometer within 6 months from MRI examination, and Cardiac Output was calculated through waveforms recorded from the middle finger and brachial level. Pulsatility Index was calculated (PSV-EDV/MeanV) in both Common Carotid Arteries using ultrasound. Aortic stiffness has been estimated by carotid-femoral pulse wave velocity (cfPWV) (table 1).

Results

Age was associated with Pulsatility indexes (Right r=0.21; left r=0.19), cfPWV (r=0.16), and cardiac output (r= −0.16), but not with mean blood pressure, heart rate or regional CBF.

Cardiac Output was associated with regional CBF in a majority of areas in left and right hemisphere. A linear regression unstandardized coefficients (B) are presented in Table 2 , adjusted for: age, gender, heart rate, mean blood pressure, pulsatility index of corresponding carotid, and cfPWV. Strongest associations were observed in posterior and cerebellar areas, as well as border zone /watershed areas. Gender was a significant confounder in several ROIs, indicating stronger association in females.

Discussion

The variability of regional CBF increases in elderly population and cardiac output is decreasing with age. In older adults, Cardiac Output is strongly associated with regional CBF, especially in posterior and watershed brain areas, independently of central or peripheral arterial stiffness. Sex-related difference observed in younger elderly is still present in aging.