Sabayan, Behnam

Complex bidirectional interactions between the nervous and cardiovascular systems are integrated through the heart–brain axis, a physiological pathway that governs both neural regulation of cardiovascular function and cardiovascular influences on brain health. Emerging evidence indicates that even in the absence of overt disease, subclinical changes in the heart, aortic arch, and extracranial arteries contribute to brain injury and cognitive vulnerability. This review synthesizes current knowledge on how subclinical heart–brain axis dysfunction affects brain structure and function, highlighting the roles of central and autonomic neural pathways as well as hormonal signaling in driving neurological decline. Key biomarkers linked to silent brain injury, cognitive decline, and dementia are discussed, emphasizing their potential for early risk stratification and as targets for preventive interventions. We also outline mechanistic pathways connecting subclinical heart–brain axis dysfunction to adverse brain outcomes, identify major gaps in current evidence, and propose priorities for future research and clinical trials aimed at early detection and risk reduction to preserve brain health.

Introduction: Mechanical thrombectomy (MT) is a primary treatment for acute ischemic stroke due to large vessel occlusions. While effective, 20-40% of patients experience hemorrhagic transformation (HT), and around 50% fail to achieve favorable functional outcomes. Transcranial Doppler (TCD) is a non-invasive and cost-effective method for real-time monitoring of hemodynamic status following MT. However, the prognostic value of TCD parameters in predicting HT and poor functional outcome is unclear. We performed a systematic review and meta-analysis of 4 TCD parameters (mean flow velocity (MFV), MFV index, peak systolic velocity (PSV), and pulsatility index (PI) in patients with and without HT and favorable vs poor functional recovery (modified Rankin Scale (mRS) 0-2 vs 3-6). Methods: PubMed, Embase, and Scopus were searched on July 25, 2024 to identify observational studies in which TCD parameters were measured within 48 hours from successful MT (Thrombolysis in Cerebral Infarction 2b–3) of anterior circulation. Risk of bias assessment was performed using a standardized tool tailored for TCD studies. The standardized mean difference (Hedges’ g) with 95% CI and risk ratios (RRs) with 95% CI were calculated using random-effects models. The review was prospectively registered on PROSPERO (registration number CRD42024575381). Results: Eleven studies met inclusion criteria. No study had high risk of bias. MFV and MFV index were higher in patients with HT+ compared with HT- (Hedges' g = 0.42 and 0.54, p = 0.015 and 0.005, respectively). Patients with MFV index ≥1.3 showed a higher risk of all HT (RR = 2.01, 95% CI = 1.27–3.17, p = 0.003), symptomatic HT (RR, 4.68; 95% CI,1.49–14.65, p=0.008), and poor functional recovery at 90 days (RR, 1.66; 95% CI,1.32–2.08, p<0.001), respectively. There was no difference in mean PSV (p=0.1) and PI (p=0.3) among groups with and without HT. Conclusion: Our study highlights the prognostic value of TCD parameters, particularly MFV index, in predicting HT, symptomatic HT, and poor functional recovery after successful MT in the anterior circulation. Our findings were limited by low number of studies. Large-scale and multi-center studies are needed to confirm these findings and validate the MFV index as a reliable predictor to improve post-thrombectomy care.

Background Transcranial Doppler (TCD) is a non-invasive, bedside tool that allows for real-time monitoring of the patient’s hemodynamic status following mechanical thrombectomy (MT). This systematic review and meta-analysis aims to evaluate the predictive value of TCD parameters following successful MT (Thrombolysis in Cerebral Infarction 2b–3). Methods In July 2024, we searched PubMed, Embase, and Scopus, to identify observational studies in which TCD parameters were measured within 48 hours of MT. Using random-effects models, we compared four TCD parameters (mean flow velocity (MFV), MFV index, pulsatility index (PI), and peak systolic velocity (PSV) among groups with vs without hemorrhagic transformation (HT) and favorable vs poor functional recovery (modified Rankin Scale 0–2 vs 3–6). Results Eleven studies comprising 1432 patients (59% male; mean age range: 63–73 years) were included. The MFV and MFV index were higher in patients with HT (Hedges' g=0.42 and 0.54, P=0.015 and 0.005, respectively). Patients with MFV index ≥1.3 showed a higher risk of all HT (RR 1.97; 95% confidence interval (CI) 1.28 to 3.03, P=0.002), symptomatic HT (RR 4.68; 95% CI 1.49 to 14.65, P=0.008), and poor functional status at 90 days (RR 1.65; 95% CI 1.27 to 2.14, P=0.029), respectively. There was no difference in mean PSV (P=0.1) and PI (P=0.3) among groups with and without HT. Conclusion This study underscores the prognostic value of the MFV index in predicting HT, symptomatic HT, and poor functional recovery after successful MT in the anterior circulation. Large-scale, multi-center studies are necessary to confirm these findings and to validate the MFV index as a reliable predictor for improving post-thrombectomy care.

AbstractBackgroundCervical artery dissection (CAD) is a common cause of ischemic stroke in young adults. Local blood clot formation and distal emboli are the key mechanisms for the development of stroke in patients with CAD. Microemboli distal to the dissection point can be detected as high‐intensity transient signals (HITS) using transcranial Doppler (TCD). Despite this unique capability, TCD is used inconsistently in the management of CAD. In this international survey, we aim to explore the frequency and potential barriers to TCD use in CAD.MethodThis study was an international electronic survey, based on the Antithrombotic Treatment for Stroke Prevention in Cervical Artery Dissection (STOP‐CAD) study, aiming at evaluating the use of TCD in diagnosing and managing CAD patients. A comprehensive questionnaire was developed to gather insights into the current practices, perceptions, and potential barriers to the effective use of TCD in participating centers. The collected data was then analyzed.ResultsFifty‐eight medical centers with advanced stroke care capabilities from Europe and United States participated in this study. Half (29 out of 58) of the sites routinely perform TCD on CAD patients, particularly in the presence of carotid or vertebral artery stenosis, complete carotid occlusion, and early neurologic deterioration. The primary reason for participating institutions not performing TCD was because its results would not change their practice. The protocol for TCD monitoring and managing HITS‐positive CAD patients varied among centers but transitioning from antiplatelet to anticoagulant was the most common practice in this patient population.ConclusionHalf of the stroke centers in our survey routinely perform TCD monitoring for CAD patients. The detection of HITS in CAD patients is a warning sign for providers, which may prompt a change in secondary stroke prevention management. However, a standard protocol for performing TCD in CAD and treatment recommendations for HITS‐positive CAD are not currently available, which warrants further research.