Effects of paced heart rate on cerebral pulsatility
Research type
Research Study
Full title
Effects of paced heart rate on cerebral blood flow velocity and pulsatility
IRAS ID
324378
Contact name
Alastair J S Webb
Contact email
Sponsor organisation
University of Oxford, Research Governance, Ethics and Assurance
Duration of Study in the UK
1 years, 0 months, 31 days
Research summary
Research summary:
Chronic damage to the small blood vessels in the brain (‘small vessel disease’) causes 30% of strokes and 45% of dementia, but has no specific treatment. We recently demonstrated in 759 patients with a minor stroke that these changes are strongly related to a greater variation in the blood flow to the brain during each heart beat (‘pulsatility’). This increases significantly when heart rates are lower, particularly in older patients with ‘stiffer’ blood vessels. However, it remains unclear whether pulsatility can effectively be reduced by increasing heart rate, or whether other factors are responsible for both.This pilot study aims to test whether actively increasing a patient’s heart rate results in a reduction in pulsatility of blood flow to the brain. We will continuously monitor blood pressure and blood flow to the brain in 32 patients who are having a pacemaker inserted, using an ultrasound scanner, similar to those we use to look at babies in the womb. A pacemaker is an implanted device that directly stimulates the heart to beat, and therefore we can directly control a patient’s heart rate during the procedure. During routine implantation of a pacemaker in these patients, we will gradually increase their heart rate from 50 to 100 bpm. By measuring how the pulsatility of blood flow to the brain changes as heart rate increases, we can determine whether increasing heart rate reduces pulsatility of blood flow to the brain. We will retest 10 patients, 4-8 weeks after the pacemaker is implanted to test whether this relationship remains stable.
This study will use simple monitoring during an already required medical procedure to test whether heart rate changes directly cause a change in cerebral pulsatlity, and therefore whether treatments to increase heart rate have the potential to prevent small vessel disease.
Lay summary of study results:
The study recruited 20 participants undergoing implantation of a pacemaker for 'heart block' causing a slow heart rate, either as a planned or emergency procedure, including 10 participants with a planned follow-up visit. During implantation of the pacemaker their heart rate was increased from about 50 beats per minute to hundred beats per minute and back again, whilst we recorded blood flow to the brain with ultrasound. This demonstrated a very strong reduction in the 'pulsatility' of blood flow to the brain, the difference between the maximum and minimum blood flow with each heart beat, without reducing the average blood flow. This is an important marker of chronic damage to the small blood vessels in the brain that is a key cause of vascular dementia. Therefore, this result opens up the possibility that we can reduce risks of stroke and dementia in people with pacemakers by better selection of their heart rate.REC name
London - Brent Research Ethics Committee
REC reference
23/PR/0090
Date of REC Opinion
23 Feb 2023
REC opinion
Favourable Opinion