Cerebral haemodynamics during arrhythmia in health, ischaemic heart disease and heart failure with reduced ejection fraction, and in a preclinical swine model
Bibliographic record
Abstract
Abstract Ventricular arrhythmias are associated with neurological impairment and could represent a source of cerebral hypoperfusion. In the present study, data from healthy individuals ( n = 11), patients with ischaemic heart disease (IHD; ejection fraction >40%; n = 9) and patients with heart failure with reduced ejection fraction (HFrEF; EF = 31 (5)%, n = 11), as well as data from swine surgeries, where spontaneous ventricular arrhythmias were observed during cerebrovascular examination (transcranial Doppler ultrasound in humans and laser Doppler in swine) were analysed retrospectively to investigate the effect of arrhythmia on cerebral microvascular haemodynamics. A subset of participants also completed the Montreal Cognitive Assessment (MoCA). Middle cerebral artery mean blood velocity (MCA Vmean ) decreased during premature ventricular contraction (PVC) in all groups, and data from swine indicate PVCs reduced cerebral microvascular perfusion. Overall MCA Vmean was decreased in the HFrEF vs . control group. Further, %∆MCA Vmean /%∆mean arterial pressure during the PVC was greater in the HFrEF vs . control group and was correlated with decreased MoCA scores. Subanalysis of HFrEF data revealed that during bigeminy MCA Vmean decreased owing to reductions during irregular beats only. During non‐sustained ventricular tachycardia, MCA Vmean decreased but recovered above baseline upon return to sinus rhythm. Also, haemodynamic perturbations during and following the PVC were greater in the brachial artery vs . the MCA. Therefore, ventricular arrhythmias decreased indices of cerebral perfusion irrespective of IHD or HFrEF. The relative magnitude of arrhythmia‐induced haemodynamic perturbations appears to be population specific and arrhythmia type and organ dependent. The cumulative burden of arrhythmia‐induced deficits may exacerbate existing cerebral hypoperfusion in HFrEF and contribute to neurological abnormalities in this population. Key points Irregular heartbeats are often considered benign in isolation, but individuals who experience them frequently have a higher prevalence of cerebrovascular and/or cognitive associated disorders. How irregular heartbeats affect blood pressure and cerebral haemodynamics in healthy and cardiovascular disease patients, those with and without reduced ejection fraction, remains unknown. Here it was found that in the absence of symptoms associated with irregular heartbeats, such as dizziness or hypotension, single, multiple non‐sustained and sustained irregular heartbeats influence cerebral haemodynamics in a population‐specific, arrhythmia‐type and organ‐dependent manner. Relative deficits in the index of cerebral blood flow normalized to relative deficits in blood pressure were greatest in patients with heart failure with reduced ejection and inversely related with cognitive performance. Chronic arrhythmias may exacerbate existing cerebral hypoperfusion in heart failure with reduced ejection fraction, thereby providing a mechanistic link between otherwise benign irregular heartbeats and cognitive dysfunction, independent of embolism.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".