Loss of cerebral regulation during cardiac output variations in focal cerebral ischemia

Whole Blood Viscosity and Cerebral Blood Flow in Acute Ischemic Stroke

Existing effective treatments for ischemic stroke restore blood supply to the ischemic region using thrombolysis or mechanical removal of clot. However, it is increasingly recognized that successful removal of occlusive thrombus from the large artery-recanalization, may not always be accompanied by successful restoration of blood flow to the downstream tissues-reperfusion. Ultimately, brain tissue survival depends on cerebral perfusion, and a functioning microcirculation. Because capillary diameter is often equal to or smaller than an erythrocyte, microcirculation is largely dependent on erythrocyte rheological (hemorheological) factors such as whole blood viscosity (WBV). Several studies in the past have demonstrated elevated WBV in stroke compared with healthy controls. Also, elevated WBV has shown to be an independent risk factor for stroke. Elevated WBV leads to endothelial dysfunction, decreases nitric oxide-dependent flow-mediated vasodilation, and promotes hemostatic alterations/thrombosis, all leading to microcirculation sludging. Compromised microcirculation further leads to decreased cerebral perfusion. Hence, modulating WBV through pharmacological agents might be beneficial to improve cerebral perfusion in stroke. This review discusses the effect of elevated WBV on endothelial function, hemostatic alterations, and thrombosis leading to reduced cerebral perfusion in stroke.

Measurement of non-invasive cardiac output during cycling exercise in ischemic stroke inpatients: A pilot study

BACKGROUND

Cardiac dysfunction accompanies acute ischemic stroke and affects the effective implementation of early rehabilitation interventions. There is a lack of reference hemodynamic data on cardiac function in the subacute phase of ischemic stroke.

OBJECTIVE

In this study, we aimed to identify appropriate cardiac parameters for exercise training utilizing a pilot study.

METHODS

We used a transthoracic electrical bioimpedance non-invasive cardiac output measurement (NICOM) device to monitor cardiac function in real time for two groups [i.e., subacute ischemic stroke inpatients group (n= 10) and healthy control group (n= 11)] using a cycling exercise experiment. The parameters of both groups were compared to highlight the cardiac dysfunction in the subacute phase in patients with ischemic stroke.

RESULTS

We considered stroke volume index (SVI) and systemic vascular resistance index (SVRi) as the primary outcomes, and there was significant intragroup difference (stroke group: P< 0.001; control group: P< 0.001, using one-way ANOVA) and significant intergroup difference at each individual time segment (P< 0.01, using independent t-test). Among the secondary outcomes, i.e., cardiac index (CI), ejection fraction (EF), end-diastolic volume (EDV), and cardiac contraction index (CTI), we found significant intergroup differences in CI, EF, and CTI scores (P< 0.01, using independent t-test). Significant interaction with respect to time and group were seen only in the SVRi and CI scores (P< 0.01, using two-way ANOVA). There was no significant inter- or intra-group differences in EDV scores.

CONCLUSION

SVRI, SVI, and CI values highlight cardiac dysfunction in stroke patients the most. At the same time, these parameters suggest that cardiac dysfunction in stroke patients may be closely related to the increased peripheral vascular resistance caused by infarction and the limitation of myocardial systolic function.

Role of albumin-induced volume expansion therapy for cerebral vasospasm in aneurysmal subarachnoid hemorrhage: A systematic review

Objectives

This study reviews the effect of albumin-induced volume expansion therapy on symptomatic vasospasm and clinical outcome in aneurysmal subarachnoid hemorrhage (aSAH).

Materials and Methods

Computer searches carried out from the Scopus, Medline, Embase, Web of Science, the Cochrane Library, and Internet documents; hand searching of medical journals; and review of reference lists. Randomized controlled trials (RCT) and observational studies (OSs) comparing albumin therapy in combination or alone with crystalloid therapy for the treatment of cerebral vasospasm in aSAH were included in the study. Risk-of-bias assessment was conducted using ROB2.0 and ROBINS-I tools for RCTs and Oss, respectively.

Results

Out of a total of 1078 searches, one RCT (published in two articles) and one observational (retrospective) study were included for final analysis. In RCT, albumin was used for volume expansion therapy with a baseline crystalloid regime and comparison made between hypervolemic and normovolemic groups and it showed no beneficial effects on symptomatic vasospasm and clinical outcomes based on the Glasgow outcome scale. Furthermore, the use of albumin showed a tendency for sodium retention with lowering of glomerular filtration rate, limiting the amount of total fluid required for targeted central venous pressure values, and thereby avoiding fluid overload manifestations. The retrospective study results between albumin versus non-albumin groups (crystalloids only) supported improved outcomes in the former group with lower in-hospital mortality. Cardiorespiratory complications were equivocal in RCT and increased in non-albumin group in the retrospective study. Risk-of-bias assessment analyses revealed "some concerns" in RCT and "serious" limitation in OS due to its retrospective design.

Conclusion

Albumin-induced volume expansion therapy for cerebral vasospasm does not have substantiative evidence to improve cerebral vasospasm and clinical outcomes in aSAH. Studies with well-designed RCTs are required to compare the use of albumin for volume expansion therapy versus standard fluid management using crystalloids to mitigate the scarcity of published data.

Assessing electrocardiogram changes after ischemic stroke with artificial intelligence

OBJECTIVE

Ischemic stroke (IS) with subsequent cerebrocardiac syndrome (CCS) has a poor prognosis. We aimed to investigate electrocardiogram (ECG) changes after IS with artificial intelligence (AI).

METHODS

We collected ECGs from a healthy population and patients with IS, and then analyzed participant demographics and ECG parameters to identify abnormal features in post-IS ECGs. Next, we trained the convolutional neural network (CNN), random forest (RF) and support vector machine (SVM) models to automatically detect the changes in the ECGs; Additionally, We compared the CNN scores of good prognosis (mRS ≤ 2) and poor prognosis (mRS > 2) to assess the prognostic value of CNN model. Finally, we used gradient class activation map (Grad-CAM) to localize the key abnormalities.

RESULTS

Among the 3506 ECGs of the IS patients, 2764 ECGs (78.84%) led to an abnormal diagnosis. Then we divided ECGs in the primary cohort into three groups, normal ECGs (N-Ns), abnormal ECGs after the first ischemic stroke (A-ISs), and normal ECGs after the first ischemic stroke (N-ISs). Basic demographic and ECG parameter analyses showed that heart rate, QT interval, and P-R interval were significantly different between 673 N-ISs and 3546 N-Ns (p < 0.05). The CNN has the best performance among the three models in distinguishing A-ISs and N-Ns (AUC: 0.88, 95%CI = 0.86-0.90). The prediction scores of the A-ISs and N-ISs obtained from the all three models are statistically different from the N-Ns (p < 0.001). Futhermore, the CNN scores of the two groups (mRS > 2 and mRS ≤ 2) were significantly different (p < 0.05). Finally, Grad-CAM revealed that the V4 lead may harbor the highest probability of abnormality.

CONCLUSION

Our study showed that a high proportion of post-IS ECGs harbored abnormal changes. Our CNN model can systematically assess anomalies in and prognosticate post-IS ECGs.

Carotid doppler indices do not predict fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting surgery

BACKGROUND AND AIM OF THE STUDY

This study aimed to determine the predictive value of carotid artery blood flow (CABF), corrected carotid flow time (CFT), and respiratory variation in carotid peak systolic velocity (DVPeakCA) for fluid responsiveness in mechanically ventilated patients undergoing coronary artery bypass grafting (CABG) surgery. It also aimed to correlate each of these indices with changes in stroke volume index (SVI) after a fluid bolus.

METHODS

This prospective, interventional, before-after study recruited 45 adult patients undergoing CABG. Following induction of anesthesia, a fluid challenge of 6 ml/kg of a crystalloid solution was delivered over 10 min. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), CABF, CFT, and DVPeakCA were recorded before and following the intervention. Patients with an increase in SVI of >15% from baseline were considered responders.

RESULTS

We had 22 responders and 23 nonresponders. Areas under the receiver operating characteristic (AUROC) curves for the studied indices (CABF, 0.516, CFT, 0.502, and DVPeakCA, 0.671) did not suggest any strong predictive value to detect fluid responsiveness. Similarly, the r values for correlation of these carotid doppler-derived indices, both baseline and as % change from baseline with the % alteration of SVI were all <0.2, which demonstrates a very weak correlation between these variables.

CONCLUSIONS

Carotid doppler indices are unreliable to assess fluid responsiveness, and cannot replace invasive methods of analyzing preload optimization. There was no significant correlation between carotid doppler-derived indices and alterations in SVI before and after the fluid bolus.

The effect of the volemic and cardiac status on brain oxygenation in patients with subarachnoid hemorrhage: a bi-center cohort study

Background

Fluid management in patients after subarachnoid hemorrhage (SAH) aims at the optimization of cerebral blood flow and brain oxygenation. In this study, we investigated the effects of hemodynamic management on brain oxygenation by integrating advanced hemodynamic and invasive neuromonitoring.

Methods

This observational cohort bi-center study included data of consecutive poor-grade SAH patients who underwent pulse contour cardiac output (PiCCO) monitoring and invasive neuromonitoring. Fluid management was guided by the transpulmonary thermodilution system and aimed at euvolemia (cardiac index, CI ≥ 3.0 L/min/m²; global end-diastolic index, GEDI 680–800 mL/m²; stroke volume variation, SVV < 10%). Patients were managed using a brain tissue oxygenation (P_btO₂) targeted protocol to prevent brain tissue hypoxia (BTH, P_btO₂ < 20 mmHg). To assess the association between CI and P_btO₂ and the effect of fluid challenges on CI and P_btO₂, we used generalized estimating equations to account for repeated measurements.

Results

Among a total of 60 included patients (median age 56 [IQRs 47–65] years), BTH occurred in 23% of  the monitoring time during the first 10 days since admission. Overall, mean CI was within normal ranges (ranging from 3.1 ± 1.3 on day 0 to 4.1 ± 1.1 L/min/m² on day 4). Higher CI levels were associated with higher P_btO₂ levels (Wald = 14.2; p < 0.001). Neither daily fluid input nor fluid balance was associated with absolute P_btO₂ levels (p = 0.94 and p = 0.85, respectively) or the occurrence of BTH (p = 0.68 and p = 0.71, respectively). P_btO₂ levels were not significantly different in preload dependent patients compared to episodes of euvolemia. P_btO₂ increased as a response to fluid boluses only if BTH was present at baseline (from 13 ± 6 to 16 ± 11 mmHg, OR = 13.3 [95% CI 2.6–67.4], p = 0.002), but not when all boluses were considered (p = 0.154).

Conclusions

In this study a moderate association between increased cardiac output and brain oxygenation was observed. Fluid challenges may improve P_btO₂ only in the presence of baseline BTH. Individualized hemodynamic management requires advanced cardiac and brain monitoring in critically ill SAH patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00960-z.

Cardiac Stroke Volume Index Is Associated With Early Neurological Improvement in Acute Ischemic Stroke Patients

Early neurological improvement as assessed with the NIH stroke scale (NIHSS) at 24 h has been associated with improved long-term functional outcomes following acute ischemic stroke (AIS). Cardiac dysfunction is often present in AIS, but its association with outcomes is incompletely defined. We performed a pilot study to evaluate the association between non-invasively measured cardiac parameters and 24-h neurological improvement in prospectively enrolled patients with suspected AIS who presented within 12 h of symptom-onset and had an initial systolic blood pressure>140 mm Hg. Patients receiving thrombolytic therapy or mechanical thrombectomy were excluded. Non-invasive pulse contour analysis was used to measure mean arterial blood pressure (MAP), cardiac stroke volume index (cSVI), cardiac output (CO) and cardiac index (CI). Transcranial Doppler recorded mean middle cerebral artery flow velocity (MFV). We defined a decrease of 4 NIHSS points or NIHSS ≤ 1 at 24-h as neurological improvement. Of 75 suspected, 38 had confirmed AIS and did not receive reperfusion therapy. Of these, 7/38 (18.4%) had neurological improvement over 24 h. MAP was greater in those without improvement (108, IQR 96-123 mm Hg) vs. those with (89, IQR 73-104 mm Hg). cSVI, CO, and MFV were similar between those without and with improvement: 37.4 (IQR 30.9-47.7) vs. 44.7 (IQR 42.3-55.3) ml/m2; 5.2 (IQR 4.2-6.6) vs. 5.3 (IQR 4.7-6.7) mL/min; and 39.9 (IQR 32.1-45.7) vs. 34.4 (IQR 27.1-49.2) cm/s, respectively. Multivariate analysis found MAP and cSVI as predictors for improvement (OR 0.93, 95%CI 0.85-0.98 and 1.14, 95%CI 1.03-1.31). In this pilot study, cSVI and MAP were associated with 24-h neurological improvement in AIS.

Cardiac Output and Cerebral Blood Flow: A Systematic Review of Cardio-Cerebral Coupling

Control of cerebral blood flow (CBF) is crucial to the management of neurocritically ill patients. Small studies which have examined the role of cardiac output (CO) as a determinant of CBF have inconsistently demonstrated evidence of cardio-cerebral coupling. Putative physiological mechanisms underpinning such coupling include changes in arterial blood pressure pulsatility, which would produce vasodilation through increased oscillatory wall-shear-stress and baroreceptor mediated reflex sympatholysis, and changes in venous backpressure which may improve cerebral perfusion pressure. We sought to summarize and contextualize the literature on the relationship between CO and CBF and discuss the implications of cardio-cerebral coupling for neurocritical care. A systematic review of the literature yielded 41 studies; all were of low-quality and at high-risk of bias. Results were heterogenous, with evidence for both corroboration and confutation of a relationship between CO and CBF in both normal and abnormal cerebrovascular states. Common limitations of studies were lack of instantaneous CBF measures with reliance on transcranial Doppler-derived blood flow velocity as a surrogate, inability to control for fluctuations in established determinants of CBF (eg, PaCO2), and direct effects on CBF by the interventions used to alter CO. Currently, the literature is insufficiently robust to confirm an independent relationship between CO and CBF. Hypothetically, the presence of cardio-cerebral coupling would have important implications for clinical practice. Manipulation of CBF could occur without the risks associated with extremes of arterial pressure, potentially improving therapy for those with cerebral ischemia of various etiologies. However, current literature is insufficiently robust to confirm an independent relationship between CO and CBF, and further studies with improved methodology are required before therapeutic interventions can be based on cardio-cerebral coupling.

Intravenous milrinone for treatment of delayed cerebral ischaemia following subarachnoid haemorrhage: a pooled systematic review

Small trials have demonstrated promising results utilising intravenous milrinone for the treatment of delayed cerebral ischaemia (DCI) after subarachnoid haemorrhage (SAH). Here we summarise and contextualise the literature and discuss the future directions of intravenous milrinone for DCI. A systematic, pooled analysis of literature was performed in accordance with the PRISMA statement. Methodological rigour was analysed using the MINORS criteria. Extracted data included patient population; treatment protocol; and clinical, radiological, and functional outcome. The primary outcome was clinical resolution of DCI. Eight hundred eighteen patients from 10 single-centre, observational studies were identified. Half (n = 5) of the studies were prospective and all were at high risk of bias. Mean age was 52 years, and females (69%) outnumbered males. There was a similar proportion of low-grade (WFNS 1-2) (49.7%) and high-grade (WFNS 3-5) (50.3%) SAH. Intravenous milrinone was administered to 523/818 (63.9%) participants. Clinical resolution of DCI was achieved in 375/424 (88%), with similar rates demonstrated with intravenous (291/330, 88%) and combined intra-arterial-intravenous (84/94, 89%) therapy. Angiographic response was seen in 165/234 (71%) receiving intravenous milrinone. Hypotension (70/303, 23%) and hypokalaemia (31/287, 11%) were common drug effects. Four cases (0.5%) of drug intolerance occurred. Good functional outcome was achieved in 271/364 (74%) patients. Cerebral infarction attributable to DCI occurred in 47/250 (19%), with lower rates in asymptomatic spasm. Intravenous milrinone is a safe and feasible therapy for DCI. A signal for efficacy is demonstrated in small, low-quality trials. Future research should endeavour to establish the optimal protocol and dose, prior to a phase-3 study.

Outcome Predictors of Stroke Mortality in the Neurocritical Care Unit

Background: Risk factors for medium to long-term mortality after stroke are well-established but predictors of in-hospital stroke mortality are less clearly characterized. Kazakhstan has the highest age-standardized mortality rate from ischemic stroke in the world. Methods: We performed a retrospective analysis of patients with stroke who were admitted over a 3.5-years period to the neurocritical care unit of a tertiary care hospital in Nur-Sultan, Kazakhstan. Results: In total, 148 critically ill patients were included in the analysis (84 ischemic stroke, 64 hemorrhagic stroke). The mean age was 63 years, 45% were male and the mean Glasgow Coma Score (±SD) at baseline was 10.3 (±3.4). The in-hospital mortality rate was similar in patients with ischemic (36%) and hemorrhagic (39%) stroke (HR 0.88, 95%CI 0.48-1.60). Median survival was 38 days (range: 1-89 days) in patients with ischemic stroke and 39 days (range: 1-63 days) in patients with hemorrhagic stroke. Univariable analysis found that patients who had a lower Glasgow Coma Scale, were in coma and who had cerebral edema were more likely to die in-hospital (P = 0.04, 0.02, <0.01, respectively). Conclusions: Our analysis showed that mortality risk in critically ill patients with hemorrhagic stroke was closer to mortality risk in patients with ischemic stroke than has been reported in other analyses. Hypertension, chronic heart failure, ischemic heart disease and atrial fibrillation were the most frequent comorbidities in patients who developed severe (life-threatening) stroke. Coma and cerebral edema on admission appear to be associated with poor outcome. This is the first publication of in-hospital stroke mortality from a Central Asian population and could form the basis for future research including development of risk scores and identifying modifiable risk factors.

Neuroinflammatory Mechanisms in Ischemic Stroke: Focus on Cardioembolic Stroke, Background, and Therapeutic Approaches

One of the most important causes of neurological morbidity and mortality in the world is ischemic stroke. It can be a result of multiple events such as embolism with a cardiac origin, occlusion of small vessels in the brain, and atherosclerosis affecting the cerebral circulation. Increasing evidence shows the intricate function played by the immune system in the pathophysiological variations that take place after cerebral ischemic injury. Following the ischemic cerebral harm, we can observe consequent neuroinflammation that causes additional damage provoking the death of the cells; on the other hand, it also plays a beneficial role in stimulating remedial action. Immune mediators are the origin of signals with a proinflammatory position that can boost the cells in the brain and promote the penetration of numerous inflammatory cytotypes (various subtypes of T cells, monocytes/macrophages, neutrophils, and different inflammatory cells) within the area affected by ischemia; this process is responsible for further ischemic damage of the brain. This inflammatory process seems to involve both the cerebral tissue and the whole organism in cardioembolic stroke, the stroke subtype that is associated with more severe brain damage and a consequent worse outcome (more disability, higher mortality). In this review, the authors want to present an overview of the present learning of the mechanisms of inflammation that takes place in the cerebral tissue and the role of the immune system involved in ischemic stroke, focusing on cardioembolic stroke and its potential treatment strategies.

Aerobic Training and Mobilization Early Post-stroke: Cautions and Considerations

Knowledge gaps exist in how we implement aerobic exercise programs during the early phases post-stroke. Therefore, the objective of this review was to provide evidence-based guidelines for pre-participation screening, mobilization, and aerobic exercise training in the hyper-acute and acute phases post-stroke. In reviewing the literature to determine safe timelines of when to initiate exercise and mobilization we considered the following factors: arterial blood pressure dysregulation, cardiac complications, blood-brain barrier disruption, hemorrhagic stroke transformation, and ischemic penumbra viability. These stroke-related impairments could intensify with inappropriate mobilization/aerobic exercise, hence we deemed the integrity of cerebral autoregulation to be an essential physiological consideration to protect the brain when progressing exercise intensity. Pre-participation screening criteria are proposed and countermeasures to protect the brain from potentially adverse circulatory effects before, during, and following mobilization/exercise sessions are introduced. For example, prolonged periods of standing and static postures before and after mobilization/aerobic exercise may elicit blood pooling and/or trigger coagulation cascades and/or cerebral hypoperfusion. Countermeasures such as avoiding prolonged standing or incorporating periodic lower limb movement to activate the venous muscle pump could counteract blood pooling after an exercise session, minimize activation of the coagulation cascade, and mitigate potential cerebral hypoperfusion. We discuss patient safety in light of the complex nature of stroke presentations (i.e., type, severity, and etiology), medical history, comorbidities such as diabetes, cardiac manifestations, medications, and complications such as anemia and dehydration. The guidelines are easily incorporated into the care model, are low-risk, and use minimal resources. These and other strategies represent opportunities for improving the safety of the activity regimen offered to those in the early phases post-stroke. The timeline for initiating and progressing exercise/mobilization parameters are contingent on recovery stages both from neurobiological and cardiovascular perspectives, which to this point have not been specifically considered in practice. This review includes tailored exercise and mobilization prescription strategies and precautions that are not resource intensive and prioritize safety in stroke recovery.

Carotid and femoral Doppler do not allow the assessment of passive leg raising effects

BACKGROUND

The hemodynamic effects of the passive leg raising (PLR) test must be assessed through a direct measurement of cardiac index (CI). We tested whether changes in Doppler common carotid blood flow (CBF) and common femoral artery blood flow (FBF) could detect a positive PLR test (increase in CI ≥ 10%). We also tested whether CBF and FBF changes could track simultaneous changes in CI during PLR and volume expansion. In 51 cases, we measured CI (PiCCO2), CBF and FBF before and during a PLR test (one performed for CBF and another for FBF measurements) and before and after volume expansion, which was performed if PLR was positive.

RESULTS

Due to poor echogenicity or insufficient Doppler signal quality, CBF could be measured in 39 cases and FBF in only 14 cases. A positive PLR response could not be detected by changes in CBF, FBF, carotid nor by femoral peak systolic velocities (areas under the receiver operating characteristic curves: 0.58 ± 0.10, 0.57 ± 0.16, 0.56 ± 0.09 and 0.64 ± 10, respectively, all not different from 0.50). The correlations between simultaneous changes in CI and CBF and in CI and FBF during PLR and volume expansion were not significant (p = 0.41 and p = 0.27, respectively).

CONCLUSION

Doppler measurements of CBF and of FBF, as well as measurements of their peak velocities, are not reliable to assess cardiac output and its changes.

Subclinical Compromise in Cardiac Strain Relates to Lower Cognitive Performances in Older Adults

BACKGROUND

Global longitudinal strain (GLS), reflecting total shortening of the myocardium during the cardiac cycle, has emerged as a more precise myocardial function measure than left ventricular ejection fraction (LVEF). Longitudinal strain may be selectively affected in subclinical heart disease, even in the presence of normal LVEF. This study examines subclinical cardiac dysfunction, assessed by GLS and LVEF, and cognition among older adults.

METHODS AND RESULTS

Vanderbilt Memory and Aging Project participants who were free of clinical dementia, stroke, and heart failure (n=318, 73±7 years, 58% male) completed neuropsychological assessment and cardiac magnetic resonance to quantify GLS and LVEF. Linear regression models related GLS and LVEF to neuropsychological performances, adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, cognitive diagnosis, and APOE*ε4 status. Models were repeated with a cardiac×cognitive diagnosis interaction term. Compromised GLS (reflected by higher values) related to worse naming (β=-0.07, P=0.04), visuospatial immediate recall (β=-0.83, P=0.03), visuospatial delayed recall (β=-0.22, P=0.03), and verbal delayed recall (β=-0.11, P=0.007). LVEF did not relate to worse performance on any measure (P>0.18). No diagnostic interactions were observed.

CONCLUSIONS

Our study results are among the first to suggest that compromised GLS relates to worse episodic memory and language performance among older adults who are free of clinical dementia, stroke, and heart failure. Subclinical cardiac dysfunction may correlate with cognitive health in late life, even when LVEF remains normal. The results add to growing evidence that GLS may be a more sensitive and preferred method for quantifying subclinical changes in cardiac function.

Paradigm Change? Cardiac Output Better Associates with Cerebral Perfusion than Blood Pressure in Ischemic Stroke

Introduction

In patients with acute ischemic stroke, penumbral perfusion is maintained by collateral flow and so far is maintained by normal mean arterial pressure (MAP) levels. Since MAP is dependent on cardiac function, optimization of cardiac output might be a valuable hemodynamic goal in order to optimize cerebral perfusion (CP).

Methods

Cerebral perfusion was assessed by transcranial color-coded duplex and transcranial perfusion sonography in 10 patients with acute large hemispheric stroke. Time-to-peak (TTP) values of defined regions of interest (ROI) within the middle cerebral artery (MCA) territory were assessed bilaterally in addition to mean flow velocities of the MCA. Via semi-invasive advanced hemodynamic monitoring systemic hemodynamic parameters were assessed, including MAP and cardiac index (CI). Patients received sonographic follow-up after optimizing CI.

Results

TTP values of the deeply located ROIs of the non-affected as well as the affected hemisphere correlated highly significantly with CI (in affected side r = −0.827, p = 0.002; and in non-affected side r = −0.908, p < 0.0001). This demonstrates dependence of CP on CI, while correlation with MAP was not detected. Neither CI nor MAP revealed significant correlation with MCA velocity.

Lower cardiac index levels relate to lower cerebral blood flow in older adults

OBJECTIVE

To assess cross-sectionally whether lower cardiac index relates to lower resting cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) among older adults.

METHODS

Vanderbilt Memory & Aging Project participants free of stroke, dementia, and heart failure were studied (n = 314, age 73 ± 7 years, 59% male, 39% with mild cognitive impairment). Cardiac index (liters per minute per meter squared) was quantified from echocardiography. Resting CBF (milliliters per 100 grams per minute) and hypercapnia-induced CVR were quantified from pseudo-continuous arterial spin-labeling MRI. Linear regressions with ordinary least-square estimates related cardiac index to regional CBF, with adjustment for age, education, race/ethnicity, Framingham Stroke Risk Profile score (systolic blood pressure, antihypertensive medication use, diabetes mellitus, current cigarette smoking, left ventricular hypertrophy, prevalent cardiovascular disease [CVD], atrial fibrillation), APOE ε4 status, cognitive diagnosis, and regional tissue volume.

RESULTS

Lower cardiac index corresponded to lower resting CBF in the left (β = 2.4, p = 0.001) and right (β = 2.5, p = 0.001) temporal lobes. Results were similar when participants with prevalent CVD and atrial fibrillation were excluded (left temporal lobe β = 2.3, p = 0.003; right temporal lobe β = 2.5, p = 0.003). Cardiac index was unrelated to CBF in other regions assessed (p > 0.25) and CVR in all regions (p > 0.05). In secondary cardiac index × cognitive diagnosis interaction models, cardiac index and CBF associations were present only in cognitively normal participants and affected a majority of regions assessed with effects strongest in the left (p < 0.0001) and right (p < 0.0001) temporal lobes.

CONCLUSIONS

Among older adults without stroke, dementia, or heart failure, systemic blood flow correlates with cerebral CBF in the temporal lobe, independently of prevalent CVD, but not CVR.

Brain-Heart Interaction: Cardiac Complications After Stroke

Neurocardiology is an emerging specialty that addresses the interaction between the brain and the heart, that is, the effects of cardiac injury on the brain and the effects of brain injury on the heart. This review article focuses on cardiac dysfunction in the setting of stroke such as ischemic stroke, brain hemorrhage, and subarachnoid hemorrhage. The majority of post-stroke deaths are attributed to neurological damage, and cardiovascular complications are the second leading cause of post-stroke mortality. Accumulating clinical and experimental evidence suggests a causal relationship between brain damage and heart dysfunction. Thus, it is important to determine whether cardiac dysfunction is triggered by stroke, is an unrelated complication, or is the underlying cause of stroke. Stroke-induced cardiac damage may lead to fatality or potentially lifelong cardiac problems (such as heart failure), or to mild and recoverable damage such as neurogenic stress cardiomyopathy and Takotsubo cardiomyopathy. The role of location and lateralization of brain lesions after stroke in brain-heart interaction; clinical biomarkers and manifestations of cardiac complications; and underlying mechanisms of brain-heart interaction after stroke, such as the hypothalamic-pituitary-adrenal axis; catecholamine surge; sympathetic and parasympathetic regulation; microvesicles; microRNAs; gut microbiome, immunoresponse, and systemic inflammation, are discussed.

Comparison of Initial Vasopressors Used for Delayed Cerebral Ischemia after Aneurysmal Subarachnoid Hemorrhage

BACKGROUND

The main reason for morbidity after aneurysmal subarachnoid hemorrhage (aSAH) is delayed cerebral ischemia (DCI). The mainstay of medical therapy for treating DCI is induced hypertension with vasopressors to restore cerebral perfusion. Both phenylephrine (PE) and norepinephrine (NE) are commonly used for induced hypertension, but the impact of the initial choice of vasopressor on the efficacy, adverse effects, or outcome after hemodynamic therapy for DCI is unknown.

METHODS

Sixty-three patients with aSAH between January 2012 and October 2014, who developed DCI (defined as new focal deficit or decline in Glasgow Coma Score) and in which PE (n = 45) or NE (n = 18) treatment was initiated were evaluated in this retrospective study. Baseline characteristics, adverse effects, the need to change or add vasopressors, the response to therapy, the need for endovascular therapy, new infarct development, discharge disposition, and 3 months modified Rankin score were all compared between pressor groups.

RESULTS

Baseline characteristics (e.g., Hunt Hess and Fisher grades) were similar. There were no differences in the overall rate of complications including arrhythmia, pulmonary edema, or kidney injury. However, those initiated on PE were more likely to be changed to an alternate vasopressor (64 vs. 33%, p = 0.016), mostly for bradycardia or failure to reach therapeutic targets. Patients initially treated with PE were less likely to respond neurologically (71 vs. 94%, p = 0.01) or to be discharged to home or acute rehabilitation facilities (73 vs. 94%, p = 0.02) and were more likely to have a delayed infarct on imaging (62 vs. 33%, p = 0.04).

CONCLUSIONS

Our study suggests that patients with DCI after aSAH initiated on PE are more likely to require treatment change to another vasopressor and are at greater risk for poor clinical outcomes compared to patients started on NE. Larger comparative studies are warranted.

The N-terminal pro B-type natriuretic peptide, and risk of dementia and cognitive decline: a 10-year follow-up study in the general population

BACKGROUND

The N-terminal pro B-type natriuretic peptide (NT-proBNP) has a well-documented prognostic value for cardiovascular disease (CVD) and higher levels are associated with cognitive-dysfunction in patients with CVD. However, how NT-proBNP relates to incident dementia and cognitive-decline in community-dwelling persons is unknown.

METHODS

Between 1997 and 2001, serum NT-proBNP was measured in 6040 participants (mean age 69 years, 57% women) free of heart-failure and dementia from the Rotterdam Study. Participants were continuously followed-up for incident dementia until 2012, for 56,616 person-years. Cognition was assessed at baseline and reassessed between 2002 and 2006 by Letter-Digit-Substitution-task, Stroop test and Word-Fluency test. Associations of NT-proBNP with dementia (555 cases), Alzheimer's disease (357 cases) and vascular dementia (32 cases) were assessed linearly, and in quartiles using Cox regression. Associations of NT-proBNP with cognitive-decline were assessed using multiple linear regression. All analyses were repeated after excluding patients with CVD.

RESULTS

Higher NT-proBNP was associated with a higher risk of dementia, even after excluding patients with CVD and adjusting for cardiovascular risk factors, HR per SD 1.27 (95% CI 1.13 to 1.44). Associations were particularly strong for vascular dementia, HR per SD 2.04 (95% CI 1.18 to 3.55), but also for Alzheimer's disease when comparing the second and third quartile with first. Higher NT-proBNP was cross-sectionally associated with poorer performance in multiple cognitive tests but longitudinally only in Letter-Digit-Substitution-task.

CONCLUSIONS

NT-proBNP reflecting subclinical CVD is associated with dementia, particularly vascular dementia. NT-proBNP can be a useful marker of imminent cognitive-decline and dementia in absence of clinical CVD.

Low cardiac index is associated with incident dementia and Alzheimer disease: the Framingham Heart Study

BACKGROUND

Cross-sectional epidemiological and clinical research suggests that lower cardiac index is associated with abnormal brain aging, including smaller brain volumes, increased white matter hyperintensities, and worse cognitive performances. Lower systemic blood flow may have implications for dementia among older adults.

METHODS AND RESULTS

A total of 1039 Framingham Offspring Cohort participants free of clinical stroke, transient ischemic attack, and dementia formed our sample (age, 69±6 years; 53% women). Multivariable-adjusted proportional hazard models adjusting for Framingham Stroke Risk Profile score (age, sex, systolic blood pressure, antihypertensive medication, diabetes mellitus, cigarette smoking, cardiovascular disease history, atrial fibrillation), education, and apolipoprotein E4 status related cardiac magnetic resonance imaging-assessed cardiac index (cardiac output divided by body surface area) to incident all-cause dementia and Alzheimer disease (AD). Over the median 7.7-year follow-up period, 32 participants developed dementia, including 26 cases of AD. Each 1-SD unit decrease in cardiac index increased the relative risk of both dementia (hazard ratio [HR]=1.66; 95% confidence interval [CI], 1.11-2.47; P=0.013) and AD (HR=1.65; 95% CI, 1.07-2.54; P=0.022). Compared with individuals with normal cardiac index, individuals with clinically low cardiac index had a higher relative risk of dementia (HR=2.07; 95% CI, 1.02-4.19; P=0.044). If participants with clinically prevalent cardiovascular disease and atrial fibrillation were excluded (n=184), individuals with clinically low cardiac index had a higher relative risk of both dementia (HR=2.92; 95% CI, 1.34-6.36; P=0.007) and AD (HR=2.87; 95% CI, 1.21-6.80; P=0.016) compared with individuals with normal cardiac index.

CONCLUSION

Lower cardiac index is associated with an increased risk for the development of dementia and AD.

Relationship between cognitive impairment and echocardiographic parameters: a review

With >24 million people affected worldwide, dementia is one of the main public health challenges modern medicine has to face. The path leading to dementia is often long, with a wide spectrum of clinical presentations, and preceded by a long preclinical phase. Previous studies have demonstrated that clinical strokes and covert vascular lesions of the brain contribute to the risk for developing dementia. Although it is not yet known whether preventing such lesions reduces the risk for dementia, it is likely that starting preventive measures early in the course of the disease may be beneficial. Echocardiography is a widely available, relatively inexpensive, noninvasive imaging modality whereby morphologically or hemodynamically derived parameters may be integrated easily into a risk assessment model for dementia. The aim of this review is to analyze the information that has accumulated over the past two decades on the prognostic value of echocardiographic factors in cognitive impairment. The associations between cognitive impairment and echocardiographic parameters, including left ventricular systolic and diastolic indices, left atrial morphologic parameters, cardiac output, left ventricular mass, and aortic root diameter, have previously been reported. In the light of these studies, it appears that echocardiography may help further improve currently used risk assessment models by allowing detection of subclinical cardiac abnormalities associated with future cognitive impairment. However, many limitations, including methodologic heterogeneity and the observational designs of these studies, restrict the scope of these results. Further prospective studies are required before integrating echocardiography into a preventive strategy.

Feasibility of common carotid artery point of care ultrasound in cardiac output measurements compared to invasive methods

BACKGROUND

Cardiac output (CO) measurement in the intensive care unit (ICU) requires invasive devices such as the pulmonary artery (PA) catheter or arterial waveform pulse contour analysis (PCA). This study tests the accuracy and feasibility of point of care ultrasound (POCUS) of the common carotid artery to estimate the CO non-invasively and compare it to existing invasive CO measurement modalities.

METHODS

Patients admitted to the surgical and cardiothoracic ICU in a tertiary university-affiliated academic center during a 4-month period, with invasive hemodynamic monitoring devices for management, were included in this cohort study. Common carotid artery POCUS was performed to measure the CO and the results were compared to an invasive device.

RESULTS

Intensivists and ICU fellows, using ultrasound of the common carotid artery, obtained the CO measurements. Images of the Doppler flow and volume were obtained at the level of the thyroid gland. Concurrent CO measured via invasive devices was recorded. The patient cohort comprised 36 patients; 52 % were females. The average age was 59 ± 13 years, and 66 % were monitored via PCA device and 33 % via PA catheter. Intraclass correlation coefficient (ICC) analysis demonstrated almost perfect correlation (0.8152) between measurements of CO via ultrasound vs. invasive modalities. The ICC between POCUS and the invasive measurement via PCA was 0.84 and via PA catheter 0.74, showing substantial agreement between the ultrasound and both invasive modalities.

CONCLUSIONS

Common carotid artery POCUS offers a non-invasive method of measuring the CO in the critically ill population.

The heart-brain connection: mechanistic insights and models

While both cardiac dysfunction and progressive loss of cognitive function are prominent features of an ageing population, surprisingly few studies have addressed the link between the function of the heart and brain. Recent literature indicates that autoregulation of cerebral flow is not able to protect the brain from hypoperfusion when cardiac output is reduced or atherosclerosis is prominent. This suggests a close link between cardiac function and large vessel atherosclerosis on the one hand and brain perfusion and cognitive functioning on the other. Mechanistically, the presence of vascular pathology leads to chronic cerebral hypoperfusion, blood brain barrier breakdown and inflammation that most likely precede neuronal death and neurodegeneration. Animal models to study the effects of chronic cerebral hypoperfusion are available, but they have not yet been combined with cardiovascular models.

Cardiac complications in acute ischemic stroke

Introduction

To characterize cardiac complications in acute ischemic stroke (AIS) patients admitted from an urban emergency department (ED).

Methods

Retrospective cross-sectional study evaluating AIS patients admitted from the ED within 24 hours of symptom onset who also had an echocardiogram performed within 72 hours of admission.

Results

Two hundred AIS patients were identified with an overall in-hospital mortality rate of 8% (n = 16). In our cohort, 57 (28.5%) of 200 had an ejection fraction less than 50%, 35 (20.4%) of 171 had ischemic changes on electrocardiogram (ECG), 18 (10.5%) of 171 presented in active atrial fibrillation, 21 (13.0%) of 161 had serum troponin elevation, and 2 (1.1%) of 184 survivors had potentially lethal arrhythmias on telemetry monitoring. Subgroup analysis revealed higher in-hospital mortality rates among those with systolic dysfunction (15.8% versus 4.9%; P = 0.0180), troponin elevation (38.1% versus 3.4%; P < 0.0001), atrial fibrillation on ECG (33.3% versus 3.8%; P = 0.0003), and ischemic changes on ECG (17.1% versus 6.1%; P = 0.0398) compared with those without.

Conclusion

A proportion of AIS patients may have cardiac complications. Systolic dysfunction, troponin elevation, atrial fibrillation, or ischemic changes on ECG may be associated with higher in-hospital mortality rates. These findings support the adjunctive role of cardiac-monitoring strategies in the acute presentation of AIS.

Hemodynamic management of subarachnoid hemorrhage

Hemodynamic augmentation therapy is considered standard treatment to help prevent and treat vasospasm and delayed cerebral ischemia. Standard triple-H therapy combines volume expansion (hypervolemia), blood pressure augmentation (hypertension), and hemodilution. An electronic literature search was conducted of English-language papers published between 2000 and October 2010 that focused on hemodynamic augmentation therapies in patients with subarachnoid hemorrhage. Among the eligible reports identified, 11 addressed volume expansion, 10 blood pressure management, 4 inotropic therapy, and 12 hemodynamic augmentation in patients with unsecured aneurysms. While hypovolemia should be avoided, hypervolemia did not appear to confer additional benefits over normovolemic therapy, with an excess of side effects occurring in patients treated with hypervolemic targets. Overall, hypertension was associated with higher cerebral blood flow, regardless of volume status (normo- or hypervolemia), with neurological symptom reversal seen in two-thirds of treated patients. Limited data were available for evaluating inotropic agents or hemodynamic augmentation in patients with additional unsecured aneurysms. In the context of sparse data, no incremental risk of aneurysmal rupture has been reported with the induction of hemodynamic augmentation.

Treatment options for cerebral vasospasm in aneurysmal subarachnoid hemorrhage

Cerebral vasospasm occurs frequently after aneurysmal subarachnoid and contributes to delayed cerebral ischemia. In this article we address systematic problems with the literature on vasospasm and then review both established and experimental treatment options.

Vascular contributions to cognitive impairment and dementia: a statement for healthcare professionals from the american heart association/american stroke association

BACKGROUND AND PURPOSE

This scientific statement provides an overview of the evidence on vascular contributions to cognitive impairment and dementia. Vascular contributions to cognitive impairment and dementia of later life are common. Definitions of vascular cognitive impairment (VCI), neuropathology, basic science and pathophysiological aspects, role of neuroimaging and vascular and other associated risk factors, and potential opportunities for prevention and treatment are reviewed. This statement serves as an overall guide for practitioners to gain a better understanding of VCI and dementia, prevention, and treatment.

METHODS

Writing group members were nominated by the writing group co-chairs on the basis of their previous work in relevant topic areas and were approved by the American Heart Association Stroke Council Scientific Statement Oversight Committee, the Council on Epidemiology and Prevention, and the Manuscript Oversight Committee. The writing group used systematic literature reviews (primarily covering publications from 1990 to May 1, 2010), previously published guidelines, personal files, and expert opinion to summarize existing evidence, indicate gaps in current knowledge, and, when appropriate, formulate recommendations using standard American Heart Association criteria. All members of the writing group had the opportunity to comment on the recommendations and approved the final version of this document. After peer review by the American Heart Association, as well as review by the Stroke Council leadership, Council on Epidemiology and Prevention Council, and Scientific Statements Oversight Committee, the statement was approved by the American Heart Association Science Advisory and Coordinating Committee.

RESULTS

The construct of VCI has been introduced to capture the entire spectrum of cognitive disorders associated with all forms of cerebral vascular brain injury-not solely stroke-ranging from mild cognitive impairment through fully developed dementia. Dysfunction of the neurovascular unit and mechanisms regulating cerebral blood flow are likely to be important components of the pathophysiological processes underlying VCI. Cerebral amyloid angiopathy is emerging as an important marker of risk for Alzheimer disease, microinfarction, microhemorrhage and macrohemorrhage of the brain, and VCI. The neuropathology of cognitive impairment in later life is often a mixture of Alzheimer disease and microvascular brain damage, which may overlap and synergize to heighten the risk of cognitive impairment. In this regard, magnetic resonance imaging and other neuroimaging techniques play an important role in the definition and detection of VCI and provide evidence that subcortical forms of VCI with white matter hyperintensities and small deep infarcts are common. In many cases, risk markers for VCI are the same as traditional risk factors for stroke. These risks may include but are not limited to atrial fibrillation, hypertension, diabetes mellitus, and hypercholesterolemia. Furthermore, these same vascular risk factors may be risk markers for Alzheimer disease. Carotid intimal-medial thickness and arterial stiffness are emerging as markers of arterial aging and may serve as risk markers for VCI. Currently, no specific treatments for VCI have been approved by the US Food and Drug Administration. However, detection and control of the traditional risk factors for stroke and cardiovascular disease may be effective in the prevention of VCI, even in older people.

CONCLUSIONS

Vascular contributions to cognitive impairment and dementia are important. Understanding of VCI has evolved substantially in recent years, based on preclinical, neuropathologic, neuroimaging, physiological, and epidemiological studies. Transdisciplinary, translational, and transactional approaches are recommended to further our understanding of this entity and to better characterize its neuropsychological profile. There is a need for prospective, quantitative, clinical-pathological-neuroimaging studies to improve knowledge of the pathological basis of neuroimaging change and the complex interplay between vascular and Alzheimer disease pathologies in the evolution of clinical VCI and Alzheimer disease. Long-term vascular risk marker interventional studies beginning as early as midlife may be required to prevent or postpone the onset of VCI and Alzheimer disease. Studies of intensive reduction of vascular risk factors in high-risk groups are another important avenue of research.

Cardiac output in idiopathic normal pressure hydrocephalus: association with arterial blood pressure and intracranial pressure wave amplitudes and outcome of shunt surgery

BACKGROUND

In patients with idiopathic normal pressure hydrocephalus (iNPH) responding to shunt surgery, we have consistently found elevated intracranial pressure (ICP) wave amplitudes during diagnostic ICP monitoring prior to surgery. It remains unknown why ICP wave amplitudes are increased in these patients. Since iNPH is accompanied by a high incidence of vascular co-morbidity, a possible explanation is that there is reduced vascular compliance accompanied by elevated arterial blood pressure (ABP) wave amplitudes and even altered cardiac output (CO). To investigate this possibility, the present study was undertaken to continuously monitor CO to determine if it is correlated to ABP and ICP wave amplitudes and the outcome of shunting in iNPH patients. It was specifically addressed whether the increased ICP wave amplitudes seen in iNPH shunt responders were accompanied by elevated CO and/or ABP wave amplitude levels.

METHODS

Prospective iNPH patients (29) were clinically graded using an NPH grading scale. Continuous overnight minimally-invasive monitoring of CO and ABP was done simultaneously with ICP monitoring; the CO, ABP, and ICP parameters were parsed into 6-second time windows. Patients were assessed for shunt surgery on clinical grade, Evan's index, and ICP wave amplitude. Follow-up clinical grading was performed 12 months after surgery.

RESULTS

ICP wave amplitudes but not CO or ABP wave amplitude, showed good correlation with the response to shunt treatment. The patients with high ICP wave amplitude did not have accompanying high levels of CO or ABP wave amplitude. Correlation analysis between CO and ICP wave amplitudes in individual patients showed different profiles [significantly positive in 10 (35%) and significantly negative in 16 (55%) of 29 recordings]. This depended on whether there was also a correlation between ABP and ICP wave amplitudes and on the average level of ICP wave amplitude.

CONCLUSIONS

These results gave no evidence that the increased levels of ICP wave amplitudes seen in iNPH shunt responders prior to surgery were accompanied by elevated levels of ABP wave amplitudes or elevated CO. In the individual patients the correlation between CO and ICP wave amplitude was partly related to an association between ABP and ICP wave amplitudes which can be indicative of the state of cerebrovascular pressure regulation, and partly related to the ICP wave amplitude which can be indicative of the intracranial compliance.

Cardiac output as a potential risk factor for abnormal brain aging

Heart failure has served as a clinically useful model for understanding how cardiac dysfunction is associated with neuroanatomic and neuropsychological changes in aging adults, theoretically because systemic hypoperfusion disrupts cerebral perfusion, contributing to clinical brain injury. This review summarizes more recent data suggesting that subtle cardiac dysfunction or low normal levels of cardiac function, as quantified by cardiac output, are related to cognitive and neuroimaging markers of abnormal brain aging in the absence of heart failure or severe cardiomyopathy. Additional work is required, but such associations suggest that reduced cardiac output may be a risk factor for Alzheimer's disease (AD) and abnormal brain aging through the propagation or exacerbation of neurovascular processes, microembolism due to thrombosis, and AD neuropathological processes. Such mechanistic pathways are discussed in the context of a theoretical model that posits a direct pathway of injury between cardiac output and abnormal brain aging (i.e., reduced systemic blood flow disrupts cerebral blood flow homeostasis), contributing to clinical brain injury, independent of shared risk factors for both cardiac dysfunction and abnormal brain aging.

The relationship between cardiac output and dynamic cerebral autoregulation in humans

Cerebral autoregulation adjusts cerebrovascular resistance in the face of changing perfusion pressures to maintain relatively constant flow. Results from several studies suggest that cardiac output may also play a role. We tested the hypothesis that cerebral blood flow would autoregulate independent of changes in cardiac output. Transient systemic hypotension was induced by thigh-cuff deflation in 19 healthy volunteers (7 women) in both supine and seated positions. Mean arterial pressure (Finapres), cerebral blood flow (transcranial Doppler) in the anterior (ACA) and middle cerebral artery (MCA), beat-by-beat cardiac output (echocardiography), and end-tidal Pco(2) were measured. Autoregulation was assessed using the autoregulatory index (ARI) defined by Tiecks et al. (Tiecks FP, Lam AM, Aaslid R, Newell DW. Stroke 26: 1014-1019, 1995). Cerebral autoregulation was better in the supine position in both the ACA [supine ARI: 5.0 ± 0.21 (mean ± SE), seated ARI: 3.9 ± 0.4, P = 0.01] and MCA (supine ARI: 5.0 ± 0.2, seated ARI: 3.8 ± 0.3, P = 0.004). In contrast, cardiac output responses were not different between positions and did not correlate with cerebral blood flow ARIs. In addition, women had better autoregulation in the ACA (P = 0.046), but not the MCA, despite having the same cardiac output response. These data demonstrate cardiac output does not appear to affect the dynamic cerebral autoregulatory response to sudden hypotension in healthy controls, regardless of posture. These results also highlight the importance of considering sex when studying cerebral autoregulation.

Cardiac index is associated with brain aging: the Framingham Heart Study

BACKGROUND

Cardiac dysfunction is associated with neuroanatomic and neuropsychological changes in aging adults with prevalent cardiovascular disease, theoretically because systemic hypoperfusion disrupts cerebral perfusion, contributing to subclinical brain injury. We hypothesized that cardiac function, as measured by cardiac index, would be associated with preclinical brain magnetic resonance imaging (MRI) and neuropsychological markers of ischemia and Alzheimer disease in the community.

METHODS AND RESULTS

Brain MRI, cardiac MRI, neuropsychological, and laboratory data were collected on 1504 Framingham Offspring Cohort participants free of clinical stroke, transient ischemic attack, or dementia (age, 61+/-9 years; 54% women). Neuropsychological and brain MRI variables were related to cardiac MRI-assessed cardiac index (cardiac output/body surface area). In multivariable-adjusted models, cardiac index was positively related to total brain volume (P=0.03) and information processing speed (P=0.02) and inversely related to lateral ventricular volume (P=0.048). When participants with clinically prevalent cardiovascular disease were excluded, the relation between cardiac index and total brain volume remained (P=0.02). Post hoc comparisons revealed that participants in the bottom cardiac index tertile (values <2.54) and middle cardiac index tertile (values between 2.54 and 2.92) had significantly lower brain volumes (P=0.04) than participants in the top cardiac index tertile (values >2.92).

CONCLUSIONS

Although observational data cannot establish causality, our findings are consistent with the hypothesis that decreasing cardiac function, even at normal cardiac index levels, is associated with accelerated brain aging.

Atlas-derived perfusion correlates of white matter hyperintensities in patients with reduced cardiac output

Reduced cardiac output is associated with increased white matter hyperintensities (WMH) and executive dysfunction in older adults, which may be secondary to relations between systemic and cerebral perfusion. This study preliminarily describes the regional distribution of cerebral WMH in the context of a normal cerebral perfusion atlas and aims to determine if these variables are associated with reduced cardiac output. Thirty-two participants (72 ± 8 years old, 38% female) with cardiovascular risk factors or disease underwent structural MRI acquisition at 1.5T using a standard imaging protocol that included FLAIR sequences. WMH distribution was examined in common anatomical space using voxel-based morphometry and as a function of normal cerebral perfusion patterns by overlaying a single photon emission computed tomography (SPECT) atlas. Doppler echocardiogram data was used to dichotomize the participants on the basis of low (n=9) and normal (n=23) cardiac output. Global WMH count and volume did not differ between the low and normal cardiac output groups; however, atlas-derived SPECT perfusion values in regions of hyperintensities were reduced in the low versus normal cardiac output group (p<0.001). Our preliminary data suggest that participants with low cardiac output have WMH in regions of relatively reduced perfusion, while normal cardiac output participants have WMH in regions with relatively higher regional perfusion. This spatial perfusion distribution difference for areas of WMH may occur in the context of reduced systemic perfusion, which subsequently impacts cerebral perfusion and contributes to subclinical or clinical microvascular damage.

Blood viscosity modulates tissue perfusion: sometimes and somewhere

Each organ possesses specific properties for controlling microvascular perfusion. Such specificity provides an opportunity to design transfusion fluids that target thrombo-embolic or vasospasm-induced ischemia in a particular organ or that optimize overall perfusion from systemic shock. The role of viscosity in the design of these fluids might be underestimated, because viscosity is rarely monitored or considered in critical care decisions. Studies linking viscosity-dependent changes of microvascular perfusion to outcome-relevant data suggest that whole blood viscosity is negligible as a determinant of microvascular perfusion under physiological conditions when autoregulation is effective. Because autoregulation is driven to maintain oxygen supply constant, the organism will compensate for changes in blood viscosity to sustain oxygen delivery. In contrast, under pathological conditions in the brain and elsewhere, increases of overall viscosity should be avoided - including all the situations where vascular autoregulatory mechanisms are inoperative due to ischemia, structural damage or physiologic dysfunction. As latter conditions are not to identify with high certainty, the risks that accompany therapeutic correction of blood viscosity are outweighing the benefits. The ability to bedside monitor blood viscosity and to link changes in viscosity to outcome parameters in various clinical conditions would provide more solid foundation for evidence-based clinical management.

Effects of hypervolemia and hypertension on regional cerebral blood flow, intracranial pressure, and brain tissue oxygenation after subarachnoid hemorrhage

OBJECTIVE

Hypertensive, hypervolemic, hemodilution therapy (triple-H therapy) is a generally accepted treatment for cerebral vasospasm after subarachnoid hemorrhage. However, the particular role of the three components of triple-H therapy remains controversial. The aim of the study was to investigate the influence of the three arms of triple-H therapy on regional cerebral blood flow and brain tissue oxygenation.

DESIGN

Animal research and clinical intervention study.

SETTING

Surgical intensive care unit of a university hospital.

SUBJECTS AND PATIENTS

Experiments were carried out in five healthy pigs, followed by a clinical investigation of ten patients with subarachnoid hemorrhage.

INTERVENTIONS

First, we investigated the effect of the three components of triple-H therapy under physiologic conditions in an experimental pig model. In the next step we applied the same study protocol to patients following aneurysmal subarachnoid hemorrhage. Mean arterial pressure, intracranial pressure, cerebral perfusion pressure, cardiac output, regional cerebral blood flow, and brain tissue oxygenation were continuously recorded. Intrathoracic blood volume and central venous pressure were measured intermittently. Vasopressors and/or colloids and crystalloids were administered to stepwise establish the three components of triple-H therapy.

MEASUREMENTS AND MAIN RESULTS

In the animals, neither induced hypertension nor hypervolemia had an effect on intracranial pressure, brain tissue oxygenation, or regional cerebral blood flow. In the patient population, induction of hypertension (mean arterial pressure 143 +/- 10 mm Hg) resulted in a significant (p < .05) increase of regional cerebral blood flow and brain tissue oxygenation at all observation time points. In contrast, hypervolemia/hemodilution (intrathoracic blood volume index 1123 +/- 152 mL/m) induced only a slight increase of regional cerebral blood flow while brain tissue oxygenation did not improve. Finally, triple-H therapy failed to improve regional cerebral blood flow more than hypertension alone and was characterized by the drawback that the hypervolemia/hemodilution component reversed the effect of induced hypertension on brain tissue oxygenation.

CONCLUSIONS

Vasopressor-induced elevation of mean arterial pressure caused a significant increase of regional cerebral blood flow and brain tissue oxygenation in all patients with subarachnoid hemorrhage. Volume expansion resulted in a slight effect on regional cerebral blood flow only but reversed the effect on brain tissue oxygenation. In view of the questionable benefit of hypervolemia on regional cerebral blood flow and the negative consequences on brain tissue oxygenation together with the increased risk of complications, hypervolemic therapy as a part of triple-H therapy should be applied with utmost caution.

Chronic hydrocephalus-induced changes in cerebral blood flow: mediation through cardiac effects

Decreased cerebral blood flow (CBF) in hydrocephalus is believed to be related to increased intracranial pressure (ICP), vascular compression as the result of enlarged ventricles, or impaired metabolic activity. Little attention has been given to the relationship between cardiac function and systemic blood flow in chronic hydrocephalus (CH). Using an experimental model of chronic obstructive hydrocephalus developed in our laboratory, we investigated the relationship between the duration and severity of hydrocephalus and cardiac output (CO), CBF, myocardial tissue perfusion (MTP), and peripheral blood flow (PBF). Blood flow measures were obtained using the microsphere injection method under controlled hemodynamic conditions in experimental CH (n=23) and surgical control (n=8) canines at baseline and at 2, 4, 8, 12, and 16 weeks. Cardiac output measures were made using the Swan-Ganz thermodilution method. Intracranial compliance (ICC) via cerebrospinal fluid (CSF) bolus removal and infusion, and oxygen delivery in CSF and prefrontal cortex (PFC) were also investigated. We observed an initial surgical effect relating to 30% CO reduction and approximately 50% decrease in CBF, MTP, and PBF in both groups 2 weeks postoperatively, which recovered in control animals but continued to decline further in CH animals at 16 weeks. Cerebral blood flow, which was positively correlated with CO (P=0.028), showed no significant relationship with either CSF volume or pressure. Decreased CBF correlated with oxygen deprivation in PFC (P=0.006). Cardiac output was inversely related with ventriculomegaly (P=0.019), but did not correlate with ICP. Decreased CO corresponded to increased ICC, as measured by CSF infusion (P=0.04). Our results suggest that CH may have more of an influence on CO and CBF in the chronic stage than in the early condition, which was dominated by surgical effect. The cause of this late deterioration of cardiac function in hydrocephalus is uncertain, but may reflect cardiac regulation secondary to physiologic response or brain injury. The relationship between cardiac function and CBF should be considered in the pathophysiology and clinical treatment of CH.

Doppler sonographic evaluation of cerebral blood flow in anemia resulting from chronic renal failure

OBJECTIVE

This study was undertaken to describe Doppler sonographic measurement of cerebral blood flow in anemia secondary to chronic renal failure and to compare the results with data gathered from healthy control subjects. We also aimed to compare vertebral and internal carotid artery blood flows to see whether any alteration of dominance in cerebral blood supply would occur.

METHODS

We studied 27 predialytic patients with chronic anemia resulting from chronic renal failure and 20 healthy control subjects by means of extracranial Doppler sonography. In these patients, blood flows of bilateral internal carotid and vertebral arteries were measured, and net vertebral artery, net internal carotid artery, and total cerebral blood flows were estimated. Statistical significance was observed between groups, and the data were correlated with hemoglobin level. Variation of the difference of the Doppler measurements between case and control groups by side (left or right) or disease status (patient or control subject) was analyzed.

RESULTS

From the assessed Doppler parameters, only cerebral blood flow and right and net vertebral artery blood flows had a significant difference between groups (P < .05) and showed a negative correlation with hemoglobin level. Vertebral artery blood flow was found to have significant interactions with disease status (P = .009) and side (P = .054).

CONCLUSIONS

Right vertebral artery blood flow is most prone to increase in chronic anemia of chronic renal failure. This effect also appears as increasing net vertebral artery blood flow and cerebral blood flow.

Prophylactic hyperdynamic postoperative fluid therapy after aneurysmal subarachnoid hemorrhage: a clinical, prospective, randomized, controlled study

OBJECTIVE

To investigate the role of prophylactic hyperdynamic postoperative fluid therapy in preventing delayed ischemic neurological deficits attributable to cerebral vasospasm.

METHODS

We designed a prospected, randomized, controlled study and included 32 patients with subarachnoid hemorrhage. Sixteen patients received hypervolemic hypertensive hemodilution fluid therapy; the other 16 patients received normovolemic fluid therapy. All patients were monitored for at least 12 days, with clinical assessments, transcranial Doppler recordings, single-photon emission computed tomographic (SPECT) scanning, and routine computed tomographic scanning. For fluid balance monitoring, a number of blood samples were obtained on a daily basis and continuous central venous pressure and mean arterial blood pressure measurements were performed for both groups. All patients received intravenous nimodipine infusions between Day 1 and Day 12. End points of this study were clinical outcomes, clinically evident and transcranial Doppler sonography-evident vasospasm, SPECT findings, complications, and costs. Clinical examinations (using the Glasgow Outcome Scale) performed 1 year after discharge, together with neuropsychological assessments and SPECT scanning, were the basis for the evaluation of clinical outcomes.

RESULTS

No differences were observed between the two groups with respect to cerebral vasospasm (as observed clinically or on transcranial Doppler recordings). When regional cerebral blood flow was evaluated by means of SPECT analysis performed on Day 12 after subarachnoid hemorrhage, no differences were revealed. One-year clinical follow-up assessments (with the Glasgow Outcome Scale), including SPECT findings and neuropsychological function results, did not demonstrate any significant group differences. Costs were higher and complications were more frequent for the hyperdynamic therapy group.

CONCLUSION

Neither early nor late outcome measures revealed any significant differences between the two subarachnoid hemorrhage treatment models.

Hypoperfusion-related cerebral ischemia and cardiac left ventricular systolic dysfunction

BACKGROUND

Cardiomyopathy and low ejection fraction (EF) are associated with cardiac thrombi and cardiogenic embolism but may also be risk factors for hypoperfusion-related cerebral ischemia (HRCI). Current stroke subtype criteria do not include an HRCI category.

METHOD

To look for evidence of HRCI, we compared mean infarct volume between serial patients with EF < or =35% and high-grade (> or = 70%) carotid stenosis and serial patients with normal EF and high-grade carotid stenosis. We matched serial stroke patients with EF < or =35% with stroke patients with normal EF and compared the number and type of ischemic lesion (symptomatic or asymptomatic) and mean infarct volume on magnetic resonance imaging. We blindly compared stroke subtype in these groups using modified Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria, including an HRCI category.

RESULTS

In patients with carotid stenosis, ipsilateral infarct volume was greater with EF < or = 35% (74.7 mL, 95% CI, 17.3-132.1 mL) than in controls (17.1 mL, 95% Cl, 9.4-24.8 mL) (P<.05). There was no difference in the mean number of HRCI-compatible infarcts on computed tomography scan between patients with low EF and controls. Symptomatic HRCI occurred in 4 of 15 patients with low EF and in 0 of 15 controls.

CONCLUSIONS

Symptomatic HRCI occurs in patients with low EF. Severe arterial stenosis may interact with left ventricular systolic dysfunction to cause cerebral hypoperfusion. Modification of the TOAST criteria to include an HRCI subtype is feasible and HRCI should be included as a stroke subtype.

Effect of hypervolemic therapy on cerebral blood flow after subarachnoid hemorrhage : a randomized controlled trial

BACKGROUND AND PURPOSE

Cerebral blood flow (CBF) is reduced after subarachnoid hemorrhage (SAH), and symptomatic vasospasm is a major cause of morbidity and mortality. Volume expansion has been reported to increase CBF after SAH, but CBF values in hypervolemic (HV) and normovolemic (NV) subjects have never been directly compared.

METHODS

On the day after aneurysm clipping, we randomly assigned 82 patients to receive HV or NV fluid management until SAH day 14. In addition to 80 mL/h of isotonic crystalloid, 250 mL of 5% albumin solution was given every 2 hours to maintain normal (NV group, n=41) or elevated (HV group, n=41) cardiac filling pressures. CBF ((133)xenon clearance) was measured before randomization and approximately every 3 days thereafter (mean, 4.5 studies per patient).

RESULTS

HV patients received significantly more fluid and had higher pulmonary artery diastolic and central venous pressures than NV patients, but there was no effect on net fluid balance or on blood volume measured on the third postoperative day. There was no difference in mean global CBF during the treatment period between HV and NV patients (P=0.55, random-effects model). Symptomatic vasospasm occurred in 20% of patients in each group and was associated with reduced minimum regional CBF values (P=0.04). However, there was also no difference in minimum regional CBF between the 2 treatment groups.

CONCLUSIONS

HV therapy resulted in increased cardiac filling pressures and fluid intake but did not increase CBF or blood volume compared with NV therapy. Although careful fluid management to avoid hypovolemia may reduce the risk of delayed cerebral ischemia after SAH, prophylactic HV therapy is unlikely to confer an additional benefit.

Myocardial injury and left ventricular performance after subarachnoid hemorrhage

BACKGROUND AND PURPOSE

Electrocardiographic abnormalities and elevations of the creatine kinase myocardial isoenzyme (CK-MB) occur frequently after subarachnoid hemorrhage. In some patients, a reversible and presumably neurogenic form of left ventricular dysfunction is demonstrated by echocardiography. It is not known whether cardiac injury of this type adversely affects cardiovascular hemodynamic performance.

METHODS

We retrospectively studied 72 patients admitted to our neuro-ICU for aneurysmal subarachnoid hemorrhage over a 2.5-year period. We selected patients who met the following criteria: (1) CK-MB levels measured within 3 days of onset, (2) pulmonary artery catheter placed, (3) echocardiogram performed, and (4) no history of preexisting cardiac disease. Hemodynamic profiles were recorded on the day after surgery (n=67) or on the day of echocardiography (n=5) if surgery was not performed (mean, 3. 3+/-1.7 days after onset). The severity of cardiac injury was classified as none (peak CK-MB <1%, n=36), mild (peak CK-MB 1% to 2%, n=21), moderate (peak CK-MB >2%, n=6), or severe (abnormal left ventricular wall motion, n=9).

RESULTS

Abnormal left ventricular wall motion occurred exclusively in patients with peak CK-MB levels >2% (P<0.0001), poor neurological grade (P=0.002), and female sex (P=0.02). Left ventricular stroke volume index and stroke work index were elevated above the normal range in patients with peak CK-MB levels <1% and fell progressively as the severity of cardiac injury increased, with mean values for patients with abnormal wall motion below normal (both P<0.0001 by ANOVA). Cardiac index followed a similar trend, but the effect was less pronounced (P<0.0001). Using forward stepwise multiple logistic regression, we found that thick subarachnoid clot on the admission CT scan (odds ratio, 1.9; 95% confidence interval [95% CI], 1.0 to 3.4; P=0.04) and depressed cardiac index (odds ratio, 2.1; 95% CI, 1.0 to 4.1; P=0.04) were independent predictors of symptomatic vasospasm.

CONCLUSIONS

Myocardial enzyme release and echocardiographic wall motion abnormalities are associated with impaired left ventricular performance after subarachnoid hemorrhage. In severely affected patients, reduction of cardiac output from normally elevated levels may increase the risk of cerebral ischemia related to vasospasm.

Preoperative volume expansion improves tolerance to carotid artery cross-clamping during endarterectomy

OBJECTIVE

The benefit of carotid endarterectomy for carotid artery stenosis relates to both appropriate patient selection and careful surgical technique. Critical to the latter is the ability to afford intraoperative neuroprotection during carotid cross-clamping, although the optimal strategy to assure this protection remains debated. This report describes the impact of adding preoperative colloid volume expansion to a surgical algorithm that includes electroencephalographic (EEG) monitoring and barbiturate-induced burst suppression for EEG lateralization refractory to hypertension.

METHODS

The incidence of ischemic EEG change during carotid cross-clamping was observed. The results of an initial series of patients (n = 45) reported before incorporation of volume expansion were compared with the results of the current series (n = 155) of carotid endarterectomies, which included preoperative volume expansion with 6% hetastarch (500 or 1000 cc).

RESULTS

With preoperative volume expansion, there was a 40% decrease in the incidence of EEG lateralization during carotid cross-clamping (17.4 versus 28.9%, P < 0.05) and a 63% decrease in the EEG lateralization refractory to induced hypertension (5.8 versus 15.6%, P < 0.05). The combined perioperative stroke and death rate was 1.3%.

CONCLUSION

These results support the use of preoperative colloid volume expansion in carotid endarterectomy as a means of increasing the cerebral tolerance to carotid cross-clamping.

Effect of 5% albumin solution on sodium balance and blood volume after subarachnoid hemorrhage

OBJECTIVE

Subarachnoid hemorrhage (SAH) predisposes patients to excessive natriuresis and volume contraction. We studied the effects of postoperative administration of 5% albumin solution on sodium balance and blood volume after SAH. We also sought to identify physiological variables that influence renal sodium excretion after SAH.

METHODS

Forty-three patients with acute SAH were randomly assigned to receive hypervolemia or normovolemia treatment for a period of 7 days after aneurysm clipping. In addition to a base line infusion of normal saline solution (80 ml/hr), 250 ml of 5% albumin solution was administered every 2 hours for central venous pressure (CVP) values of < or =8 mm Hg (hypervolemia group, n = 19) or < or =5 mm Hg (normovolemia group, n = 24).

RESULTS

Both groups demonstrated relative volume expansion in base line measurements. The hypervolemia group received significantly more total fluid, sodium, and 5% albumin solution than did the normovolemia group and had higher CVP values and serum albumin levels (all P < 0.02). Cumulative sodium balance was even in the hypervolemia group and persistently negative in the normovolemia group, because of sodium losses that occurred on Postoperative Days 2 and 3 (P = 0.03). In a multiple-regression analysis of all patients, 24-hour sodium balance correlated negatively with glomerular filtration rate (GFR) and positively with serum albumin levels, after correction for sodium intake (P < 0.0001). Hypervolemia therapy seemed to paradoxically lower GFR (P = 0.10) and had no effect on blood volume, which declined by 10% in both groups. Pulmonary edema requiring diuresis occurred in only one patient in the hypervolemia group.

CONCLUSION

Supplemental 5% albumin solution given to maintain CVP values of >8 mm Hg prevented sodium and fluid losses but did not have an impact on blood volume in our patients, who were hypervolemic in base line measurements. The natriuresis that occurs after SAH may be mediated in part by elevations of GFR. In addition to acting as a colloid volume expander, 5% albumin solution lowers the GFR and promotes renal sodium retention after SAH. These properties may limit the amount of total fluid required to maintain a given CVP value and hence may minimize the frequency of pulmonary edema.