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Physiology & Behavior Jul 2024Postural change from supine or sitting to standing up leads to displacement of 300 to 1000 mL of blood from the central parts of the body to the lower limb, which causes... (Review)
Review
Postural change from supine or sitting to standing up leads to displacement of 300 to 1000 mL of blood from the central parts of the body to the lower limb, which causes a decrease in venous return to the heart, hence decrease in cardiac output, causing a drop in blood pressure. This may lead to falling down, syncope, and in general reducing the quality of daily activities, especially in the elderly and anyone suffering from nervous system disorders such as Parkinson's or orthostatic hypotension (OH). Among different modalities to study brain function, functional near-infrared spectroscopy (fNIRS) is a neuroimaging method that optically measures the hemodynamic response in brain tissue. Concentration changes in oxygenated hemoglobin (HbO2) and deoxygenated hemoglobin (HHb) are associated with brain neural activity. fNIRS is significantly more tolerant to motion artifacts compared to fMRI, PET, and EEG. At the same time, it is portable, has a simple structure and usage, is safer, and much more economical. In this article, we systematically reviewed the literature to examine the history of using fNIRS in monitoring brain oxygenation changes caused by sudden changes in body position and its relationship with the blood pressure changes. First, the theory behind brain hemodynamics monitoring using fNIRS and its advantages and disadvantages are presented. Then, a study of blood pressure variations as a result of postural changes using fNIRS is described. It is observed that only 58 % of the references concluded a positive correlation between brain oxygenation changes and blood pressure changes. At the same time, 3 % showed a negative correlation, and 39 % did not show any correlation between them.
Topics: Humans; Spectroscopy, Near-Infrared; Brain; Blood Pressure; Posture; Hemodynamics
PubMed: 38697274
DOI: 10.1016/j.physbeh.2024.114574 -
American Journal of Therapeutics
Meta-Analysis
Topics: Humans; Midodrine; Syncope, Vasovagal
PubMed: 35703495
DOI: 10.1097/MJT.0000000000001513 -
Open Heart Jun 2024Neurocardiogenic syncope is a common condition with significant associated psychological and physical morbidity. The effectiveness of therapeutic options for... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Neurocardiogenic syncope is a common condition with significant associated psychological and physical morbidity. The effectiveness of therapeutic options for neurocardiogenic syncope beyond placebo remains uncertain.
METHODS
The primary endpoint was the risk ratio (RR) of spontaneously recurring syncope following any therapeutic intervention. We also examined the effect of blinding on treatment efficacy. We identified all randomised trials which evaluated the effect of any pharmacological, device-based or supportive intervention on patients with a history of syncope. A systematic search was conducted on Medline, Embase, PubMed databases and Cochrane Central Register for Controlled Trials from 1950 to 25 April 2023. Event rates, their RRs and 95% CIs were calculated, and a random-effects meta-analysis was conducted for each intervention. Data analysis was performed in R using RStudio.
RESULTS
We identified 47 eligible trials randomising 3518 patients. Blinded trials assessing syncope recurrence were neutral for beta blockers, fludrocortisone and conventional dual-chamber pacing but were favourable for selective serotonin reuptake inhibitors (SSRIs) (RR 0.40, 95% CI 0.26 to 0.63, p<0.001), midodrine (RR 0.70, 95% CI 0.53 to 0.94, p=0.016) and closed-loop stimulation (CLS) pacing (RR 0.15, 95% CI 0.07 to 0.35, p<0.001). Unblinded trials reported significant benefits for all therapy categories other than beta blockers and consistently showed larger benefits than blinded trials.
CONCLUSIONS
Under blinded conditions, SSRIs, midodrine and CLS pacing significantly reduced syncope recurrence. Future trials for syncope should be blinded to avoid overestimating treatment effects.
PROSPERO REGISTRATION NUMBER
CRD42022330148.
Topics: Humans; Syncope, Vasovagal; Randomized Controlled Trials as Topic; Treatment Outcome; Recurrence
PubMed: 38890128
DOI: 10.1136/openhrt-2024-002669 -
Heart Rhythm Mar 2024Implantable loop recorders (ILRs) are increasingly used to evaluate patients with unexplained syncope. Identification of all predictors of bradycardic syncope and...
BACKGROUND
Implantable loop recorders (ILRs) are increasingly used to evaluate patients with unexplained syncope. Identification of all predictors of bradycardic syncope and consequent permanent pacemaker (PPM) insertion is of substantial clinical interest as patients in the highest risk category may benefit from upfront pacemaker insertion.
OBJECTIVE
We performed a systematic review and meta-analysis to identify risk predictors for PPM insertion in ILR recipients with unexplained syncope.
METHODS
An electronic database search (MEDLINE, Embase, Scopus, Cochrane) was performed in June 2023. Studies evaluating ILR recipients with unexplained syncope and recording risk factors for eventual PPM insertion were included. A random effects model was used to calculate the pooled odds ratio (OR) for clinical and electrocardiographic characteristics with respect to future PPM requirement.
RESULTS
Eight studies evaluating 1007 ILR recipients were included; 268 patients (26.6%) underwent PPM insertion during study follow-up. PPM recipients were older (mean age, 70.2 ± 15.4 years vs 61.6 ± 19.7 years; P < .001). PR prolongation on baseline electrocardiography was a significant predictor of PPM requirement (pooled OR, 2.91; 95% confidence interval, 1.63-5.20). The presence of distal conduction system disease, encompassing any bundle branch or fascicular block, yielded a pooled OR of 2.88 for PPM insertion (95% confidence interval, 1.53-5.41). Injurious syncope and lack of syncopal prodrome were not significant predictors of PPM insertion. Sinus node dysfunction accounted for 62% of PPM insertions, whereas atrioventricular block accounted for 26%.
CONCLUSION
Approximately one-quarter of ILR recipients for unexplained syncope require eventual PPM insertion. Advancing age, PR prolongation, and distal conduction disease are the strongest predictors for PPM requirement.
PubMed: 38508296
DOI: 10.1016/j.hrthm.2024.03.038 -
MedRxiv : the Preprint Server For... Mar 2024Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia caused by mutations in the ryanodine receptor type 2 (RyR2). Diagnosis of...
Location of ryanodine receptor type 2 mutation predicts age of onset of sudden death in catecholaminergic polymorphic ventricular tachycardia - A systematic review and meta-analysis of case-based literature.
BACKGROUND
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare inherited arrhythmia caused by mutations in the ryanodine receptor type 2 (RyR2). Diagnosis of CPVT often occurs after a major cardiac event, thus posing a severe threat to the patient's health.
METHODS
Publication databases, including PubMed, Scopus, and Embase, were searched for articles on patients with RyR2-CPVT mutations and their associated clinical presentation. Articles were reviewed by two independent reviewers and mutations were analyzed for demographic information, mutation distribution, and therapeutics. The human RyR2 cryo-EM structure was used to model CPVT mutations and predict the diagnosis and outcomes of CPVT patients.
FINDINGS
We present a database of 1008 CPVT patients from 227 papers. Data analyses revealed that patients most often experienced exercise-induced syncope in their early teenage years but the diagnosis of CPVT took a decade. Mutations located near key regulatory sites in the channel were associated with earlier onset of CPVT symptoms including sudden cardiac death.
INTERPRETATION
The present study provides a road map for predicting clinical outcomes based on the location of RyR2 mutations in CPVT patients. The study was partially limited by the inconsistency in the depth of information provided in each article, but nevertheless is an important contribution to the understanding of the clinical and molecular basis of CPVT and suggests the need for early diagnosis and creative approaches to disease management.
FUNDING
The work was supported by grant NIH R01HL145473, P01 HL164319 R25HL156002, T32 HL120826.
PubMed: 38559077
DOI: 10.1101/2024.03.15.24304349