Left Middle Cerebral Artery Flow Research Articles

Correlation between heart rate variability and cerebral autoregulation in septic patients.

Heart rate variability (HRV) may provide an estimation of the autonomous nervous system (ANS) integrity in critically ill patients. Disturbances of cerebral autoregulation (CAR) may share common pathways of ANS dysfunction. To explore whether changes in HRV and CAR index correlate in critically ill septic patients. Prospectively collected data on septic adult (> 18years) patients admitted into a mixed Intensive Care between February 2016 and August 2019 with a recorded transcranial doppler CAR assessment. CAR was assessed calculating the Pearson's correlation coefficient (i.e. mean flow index, Mxa) between the left middle cerebral artery flow velocity (FV), insonated with a 2-MHz probe, and invasive blood pressure (BP) signal, both recorded simultaneously through a Doppler Box (DWL, Germany). MATLAB software was used for CAR assessment using a validated script; a Mxa >0.3 was considered as impaired CAR. HRV was assessed during the same time period using a specific software (Kubios HRV 3.2.0) and analyzed in both time-domain and frequency domain methods. Correlation between HRV-derived variables and Mxa were assessed using the Spearman's coefficient. A total of 141 septic patients was studied; median Mxa was 0.35 [0.13-0.60], with 77 (54.6%) patients having an impaired CAR. Mxa had a significant although weak correlation with HRV time domain (SDNN, r=0.17, p=0.04; RMSSD, r=0.18, p=0.03; NN50, r=0.23, p=0.006; pNN50, r=0.23, p=0.007), frequency domain (FFT-HF, r=0.21; p=0.01; AR-HF, r=0.19; p=0.02), and non-linear domain (SD1, r=0.18, p=0.03) parameters. Impaired CAR patients had also all of these HRV-derived parameters higher than those with intact CAR. In this exploratory study, a potential association of ANS dysfunction and impaired CAR during sepsis was observed.

Sex Differences in the Cerebral Hemodynamic Response to Hypercapnia in Young Adults

Despite sexual dimorphism present in stroke and risk for Alzheimer’s disease, sex differences in cerebral blood flow regulation remain controversial. Discrepancies in the literature may be due to menstrual cycle control as well as the inherent difficulty of quantifying cerebral blood flow in humans. The purpose of this study was to evaluate the cerebral hemodynamic response to hypercapnia in young men and premenopausal women using two approaches: 1) transcranial Doppler ultrasound (TCD); and 2) 4D flow MRI. Twenty habitually physically active participants including young men (YM; n = 10, age = 24±2 y) and young women (YW; n = 10, age = 26±4 y) were studied. Young women were studied during days 2–6 of the menstrual cycle. During separate, randomized study visits, left middle cerebral artery (LMCA) velocity was measured with TCD and LMCA flow was measured with 4D flow MRI during normocapnia and two levels of hypercapnia (4% and 6% CO2). 4D flow MRI quantifies cerebral hemodynamic and angiographic data simultaneously. End‐tidal carbon dioxide and mean arterial pressure were continuously monitored with an anesthesia monitor. At baseline, LMCA velocity (YM: 53±3 cm/s vs. YW: 60±4 cm/s, p=0.15) and LMCA flow (YM: 121±10 ml/min vs. YW: 131±6 ml/min, p=0.41) were not significantly different between groups. There was a trend for YM to demonstrate a larger LMCA cross‐sectional area compared with YW at baseline (YM: 0.071±0.002 cm2 vs. YW: 0.065±0.002 cm2, p=0.052). In response to hypercapnia, the LMCA velocity response was not different between groups (YM: 1.17±0.29 cm/s/mmHg vs. YW: 1.24±0.17 cm/s/mmHg, p=0.83). However, YM demonstrated a greater LMCA flow response compared with YW (YM: 2.98±0.40 ml/min/mmHg vs. YW: 1.38±0.26 ml/min/mmHg, p<0.01), even when accounting for changes in blood pressure. In addition, the LMCA significantly vasodilated in YM in response to hypercapnia (p<0.05); however, there was no significant change in LMCA cross‐sectional area in response to hypercapnia in YW (p=0.13). These results suggest that young men have augmented cerebral blood flow response to hypercapnia compared with young women. In addition, due to small changes in vessel cross‐sectional area during hypercapnia, sex differences may be underestimated if cerebral blood velocity is used as a surrogate of blood flow.Support or Funding InformationSupported by the Wisconsin Alumni Research Foundation and the National Institutes of Health T32 HL‐007936.

LEFT ‐RIGHT PUPIL DIAMETER DIFFERENCE‐DURING RADIOGRAPHIC READING OF BRONCOPULMONARY CARCINOMA: AN EXPLORATION WITH COGNITIVE LOAD AMONG NOVICES AND EXPERTS

INTRODUCTIONThe visual reading of an x‐ray image is a necessary process in order to find specific pathological patterns. With Functional Near Infrared Spectroscopy study have shown that increased levels of oxy and deoxy hemoglobin in the left hemisphere are associated with greater cognitive load in visual challenges and Transcranial Doppler has shown an increase on left middle cerebral artery flow associated with cognitive tasks in the face of visual challenges. Nowdays, pupil diameter begins to be recognized as a non‐intrusive method for measuring cognitive load during radiographic, dental radiographic, and histopathological diagnosis processes. The present work’s objective, is to show the difference in left and right pupillary diameters during the radiographic reading of bronchopulmonary carcinoma, to explore the cognitive burdens of novice, intermediate and expert groups.MATERIAL AND METHODSWith a 60 Hz Gazepoint GP3 Eyetracker, the pupil diameter of 8 doctors was quantified during the chest radiographic reading postero‐anterior projection of a bronchopulmonary carcinoma, taken from RadioGrapichs Magazine; first‐to‐fourth year resident physicians with age = 30.6 were classified as novice with 8.5‐month training, intermediate years with 41‐month training and expert doctors with age = 67 years and with 462 months of experience. All the diagnostic challenge was exposed on a monitor with 300 DPI connected to an Intel Core i5 PC with 8GB RAM.RESULTSThe average found of pupil diameter was 4.05 mm to all groups, over the course of 2 minutes, and the difference in pupil diameter went from 3.66 mm to 4.08 mm. However, the expert group demonstrated a pattern of smaller right pupil diameter with 3.98 mm, while the left pupillary diameter reached 4.22 mm. In contrast, during the same diagnostic task, the intermediate and novice groups showed a more homogeneous pupillary opening between left and right eye, being 4.05 mm and 4.01 mm respectively.Differences obtained between the left and right pupillary diameters during the chest x ray reading tasked were observed in all groups. However, it was observed that this difference occurred at different times. The expert group increased left pupillary diameter immediately while novice and intermediate achieved the same pupillary effect 50 seconds after the task was initiated. Fig 1.CONCLUSIONIn the two minutes radiological diagnosis process for bronchopulmonary carcinoma, radiologist doctors express greater left pupil diameter with respect to the right. However, experts make such a statement almost from the beginning of the task; while the intermediate and novice groups reach this same pattern approximately half way through the task’s total time. This finding, suggests that differences in pupil diameter may be associated with visual cognitive processing during diagnostic processes. This possible relationship may be related to cognitive load lateralization to the left hemisphere. Therefore, studies of cognitive load laterality vs. ipsilateral pupil diameter during imaging are necessary, since their possible effects on academic and labor scenarios are yet to be established.Support or Funding InformationPROSEIMLEFT ‐RIGHT PUPIL DIAMETER DIFFERENCE‐ DURING 2 MINUTES OF RADIOGRAPHIC READING OF BRONCHOPULMONARY CARCINOMA AMONG NOVICES AND EXPERTSFigure 1

P4518Cerebral blood flow is lower in heart failure patients with reduced ejection fraction

Abstract Purpose Heart and brain interaction is a well-known entity in heart failure (HF) and left ventricular systolic dysfunction poses an increased risk for stroke and cognitive impairment. Transcranial Doppler (TCD) provides valuable information on cerebral blood flow and detects microembolic signals that can be used to determine the risk of cerebrovascular events. However, less is known about cerebral blood flow in HF patients with reduced EF. So, we aimed to evaluate cerebral blood flow rates by means of TCD in HF patients with reduced ejection fraction (EF). Methods This study included 46 HF patients with an EF less than 35% (mean age 65.2±11 years, mean EF 20.1±3.8%) who underwent to TCD examination. In addition, 26 healthy individuals with sinus rhythm and EF >50% (mean age 64.4±9.0 years, mean EF 63.5±2.38%) were included in the study as a control group. Minimum, maximum and mean flow velocities of the both right middle cerebral artery (RMCA) and left middle cerebral artery (LMCA) determined by TCD were analyzed. Results The average of RMCA maximum and mean flow velocities were found to be significantly lower in HF patients than those in control group (76,06±23,7 cm/s and 48,49±16,4 cm/s in HF group vs 87,84±14,5 cm/s and 56,41±10,7 cm/s in control group, p=0,025 and p=0,016, respectively). The average of LMCA maximum and mean flow velocities were also significantly lower in HF patients than those in control group (75,1±22,3 cm/s and 47,57±14.8 cm/s in HF group vs 88,73±17,7 cm/s and 57,15±12,4 cm/s in control group, p=0,009 and p=0,007, respectively). However, there was no significant difference in minimum RMCA or LMCA flow velocities between HF group and control groups (33,5±10,6 cm/s and 32,86±9,58 cm/s in HF group vs 36,34±9,2 cm/s and 36,53±10,4 cm/s in control group, p=0,226 and p=0,157, respectively). No significant microembolic signals were detected in HF and control groups. Conclusions The results of this study showed that HF patients with reduced EF have lower cerebral blood flow velocities as compared to healthy controls, which might be one of the explanations of the adverse interaction between heart and brain in HF.

Transcranial Doppler Study to Assess Intracranial Arterial Communication Before Aortic Arch Operation

The assessment of intracranial arterial communication is important to prevent a stroke from occurring during an aortic arch operation. Bilateral axillary artery perfusion was used with the left common carotid artery perfusion for selective cerebral perfusion. A preoperative left carotid artery compression test with measurement of the left middle cerebral artery (LMCA) flow was performed to determine how safe it was to interrupt the perfusion to the left common carotid artery. Eighteen patients who were scheduled for an aortic arch operation underwent the test. Before surgery, the LMCA flow was detected using transcranial Doppler ultrasonography. During manual compression of the left carotid artery, the flow velocity of the LMCA was measured and expressed as a percent in comparison to the precompression value. During carotid artery compression, flow velocity of the LMCA was reduced to 56% +/- 36% (median, 63%; range, 0% to 100%) of the precompression value. The communication to the LMCA assessed with magnetic resonance angiography showed a weak relationship to the functional flow reserve of the LMCA based on a transcranial Doppler study. The results indicated that morphologic observation with magnetic resonance angiography did not reflect the dynamic nature of the intracranial collaterals. A preoperative left carotid artery compression test with a measurement of the flow of the LMCA is useful to assess the feasibility of interrupting perfusion to the left carotid artery during aortic arch surgery with bilateral axillary artery perfusion.

Effects of ischemia‐reperfusion on goat cerebrovascular response to ADP

Brain ischemia-reperfusion (I-R) may produce cerebrovascular endothelial dysfunction, and ADP produces endothelial-dependent cerebral vasodilatation. To analyze the effects of I-R on the cerebrovascular response to ADP, 60 min occlusion followed by 60 min reperfusion of the left middle cerebral artery (MCA) was performed in anesthetized goats. Left MCA flow was electromagnetically measured, and resting cerebrovascular resistance after I-R was decreased by 20 % (P<0.01). In control conditions, local, intraarterial injections of ADP (0.03–0.3 μg) and sodium nitroprusside (SNP, 0.3–3 μg) decreased cerebrovascular resistance, and after I-R ADP increased this resistance whereas the effects of SNP were not altered. Then, the animals were killed and 3 mm-long rings from branches of the left (I-R) and right (control) MCA were prepared for isometric tension recording. Arterial segments precontrated with U46619 (3x 10−7 – 10−6 M) showed concentration-dependent relaxations to ADP (10−8–10−5 M) and SNP (10−8–10−4 M), and the relaxations to ADP but not to SNP were lower in I-R arteries. The relaxations to ADP but not to SNP were inhibited by L-NAME (10−4 M) only in control arteries, and the effects of ADP were inhibited by charybdotoxin (10−7 M) plus apamine (10−6 M) only in control arteries. Therefore, I-R may produce cerebral vasodilatation with decreased vasodilator reserve and inversion of the cerebrovascular effects of ADP. This altered effects of ADP may be related to endothelial dysfunction with decreased availability of NO and function of KCa channels. (This work was supported, in part, by CM (GR/SAL/0106/2004) and FMMM)

Orthostatic‐Mediated Hypoperfusion in Limb‐Shaking Transient Ischemic Attack

In patients with severe carotid stenosis or total occlusion, episodic contralateral motor dysfunction is more likely related to cerebral hypoperfusion than epileptogenic activity. A man with orthostatic-mediated right-sided limb shaking was found to have total left internal carotid artery occlusion. There was prominent reduction of cerebrovascular reserve seen on single photon emission computed tomography (SPECT) performed with and without acetazolomide. During assumption of an upright position transcranial Doppler (TCD) revealed a marked attenuation of the left middle cerebral artery flow pattern not associated with changes during electroencephalographic monitoring, even after administration of acetazolomide. In this man, limb shaking episodes were attributed to hypoperfusion of the contralateral cerebral hemisphere, and not to epileptogenic activity.

Echocardiographic sign for cerebral ischemia

We describe a newborn who underwent balloon dilatation of critical aortic stenosis and surgical correction of coarctation of the aorta. Postoperative Doppler echocardiogram revealed diastolic retrograde flow in the distal aortic arch and increased systolic flow as well as diastolic forward flow in the left common carotid artery. Cranial computed tomography suggested increased left middle cerebral artery flow and a subacute infarction with luxury perfusion and damage to the blood brain barrier. Therefore, in the absence of another reason for diastolic “run-oft” in the distal aortic arch, this flow pattern may represent the echocardiographic sign for cerebral hyperemia associated with subacute ischemia.