Analyzing solitary wave solutions of the nonlinear Murray equation for blood flow in vessels with non-uniform wall properties.

Solitary wave solutions are of great interest to bio-mathematicians and other scientists because they provide a basic description of nonlinear phenomena with many practical applications. They provide a strong foundation for the development of novel biological and medical models and therapies because of their remarkable behavior and persistence. They have the potential to improve our comprehension of intricate biological systems and help us create novel therapeutic approaches, which is something that researchers are actively investigating. In this study, solitary wave solutions of the nonlinear Murray equation will be discovered using a modified extended direct algebraic method. These solutions represent a uniform variation in blood vessel shape and diameter that can be used to stimulate blood flow in patients with cardiovascular disease. These solutions are newly in the literature, and give researchers an important tool for grasping complex biological systems. To see how the solitary wave solutions behave, graphs are displayed using Matlab.

Impact of Breathing Control Training Program on sonographic quantification of abdominal vasculature.

OBJECTIVES: To compare vascular scanning parameters (vessel diameter, peak systolic velocity, end-diastolic velocity, and resistive index) and scanning time before and after breathing control training program for selected abdominal vessels. METHODS: This study was pre and post quasi-experimental. The researchers designed a breathing training program that gives participants instructions through a video describing breathing maneuvers. Data were collected at the ultrasound laboratory/College of Health and Rehabilitation Sciences in Princess Nourah bint Abdul Rahman University, Riyadh, Saudi Arabia from January 2023 to November 2023. About 49 volunteers at the university participated in the study. Scanning was performed two times for the right renal artery, upper abdominal aorta, inferior vena cava, and superior mesenteric artery. Scanning time was measured before and after the program as well. A paired sample t-test was used to compare the parameters means and time before and after the program. RESULTS: The program had a significant effect on the following parameters: right renal artery peak systolic velocity (p=0.042), upper abdominal aortic peak systolic velocity, and resistive index (p=0.014, p=0.014 respectively), superior mesenteric artery and inferior vena cava diameters (p=0.010 and p=0.020). The scanning time was reduced significantly (p<0.001). CONCLUSION: The breathing training program saves time and improves ultrasound measurement quality. Hospitals and health centers should consider the importance of breathing control training programs before abdominal scanning.

Heat-related changes in the velocity and kinetic energy of flowing blood influence the human heart's output during hyperthermia.

Passive whole-body hyperthermia increases limb blood flow and cardiac output ( Q ̇ $\dot Q$ ), but the interplay between peripheral and central thermo-haemodynamic mechanisms remains unclear. Here we tested the hypothesis that local hyperthermia-induced alterations in peripheral blood flow and blood kinetic energy modulate flow to the heart and Q ̇ $\dot Q$ . Body temperatures, regional (leg, arm, head) and systemic haemodynamics, and left ventricular (LV) volumes and functions were assessed in eight healthy males during: (1) 3 h control (normothermic condition); (2) 3 h of single-leg heating; (3) 3 h of two-leg heating; and (4) 2.5 h of whole-body heating. Leg, forearm, and extracranial blood flow increased in close association with local rises in temperature while brain perfusion remained unchanged. Increases in blood velocity with small to no changes in the conduit artery diameter underpinned the augmented limb and extracranial perfusion. In all heating conditions, Q ̇ $\dot Q$ increased in association with proportional elevations in systemic vascular conductance, related to enhanced blood flow, blood velocity, vascular conductance and kinetic energy in the limbs and head (all R2 ≥ 0.803; P < 0.001), but not in the brain. LV systolic (end-systolic elastance and twist) and diastolic functional profiles (untwisting rate), pulmonary ventilation and systemic aerobic metabolism were only altered in whole-body heating. These findings substantiate the idea that local hyperthermia-induced selective alterations in peripheral blood flow modulate the magnitude of flow to the heart and Q ̇ $\dot Q$ through changes in blood velocity and kinetic energy. Localised heat-activated events in the peripheral circulation therefore affect the human heart's output. KEY POINTS: Local and whole-body hyperthermia increases limb and systemic perfusion, but the underlying peripheral and central heat-sensitive mechanisms are not fully established. Here we investigated the regional (leg, arm and head) and systemic haemodynamics (cardiac output: Q ̇ $\dot Q$ ) during passive single-leg, two-leg and whole-body hyperthermia to determine the contribution of peripheral and central thermosensitive factors in the control of human circulation. Single-leg, two-leg, and whole-body hyperthermia induced graded increases in leg blood flow and Q ̇ $\dot Q$ . Brain blood flow, however, remained unchanged in all conditions. Ventilation, extracranial blood flow and cardiac systolic and diastolic functions only increased during whole-body hyperthermia. The augmented Q ̇ $\dot Q$ with hyperthermia was tightly related to increased limb and head blood velocity, flow and kinetic energy. The findings indicate that local thermosensitive mechanisms modulate regional blood velocity, flow and kinetic energy, thereby controlling the magnitude of flow to the heart and thus the coupling of peripheral and central circulation during hyperthermia.

Decreasing the blood flow of non-compressible intra-abdominal organs with non-invasive transcutaneous electrical stimulation.

Non-invasive neuromodulation of non-compressible internal organs has significant potential for internal organ bleeding and blood-shift in aero/space medicine. The present study aims to investigate the potential influences of the non-invasive transcutaneous electrical nerve stimulation (TENS) on multiple non-compressible internal organs' blood flow. Porcine animal model (n = 8) was randomized for a total of 48 neuromodulation sessions with two different TENS stimulation frequencies (80 Hz, 10 Hz) and a placebo stimulation. A combination of two different electrode configurations (Abdominal-only or Abdominal and hind limb) were also performed. Intraarterial blood flow measurements were taken during pre and post-stimulation periods at the left renal artery, common hepatic artery, and left coronary artery. Intracranial, and extracranial arterial blood flows were also assessed with digital subtraction angiography. TENS with abdominal-only electrode configurations at 10 Hz demonstrated significant reductions in average peak blood flow velocity (APV) of the common hepatic artery (p = 0.0233) and renal arteries (p = 0.0493). Arterial pressures (p = 0.0221) were also significantly lower when renal APV was reduced. The outcome of the present study emphasises the potential use of TENS in decreasing the blood flow of non-compressible internal organs when the correct combination of electrodes configuration and frequency is used.

Doppler-derived pulmonary pulse transit time measurements in chronic obstructive pulmonary disease: Reproducibility and cardiopulmonary function.

INTRODUCTION: Doppler-derived pulmonary pulse transit time (pPTT) is an auspicious hemodynamic marker in chronic pulmonary diseases. The aim is to compare four distinct pPTT measurements and its relation to right cardiac and pulmonary function. METHODS: Prospectively, 25 chronic obstructive pulmonary disease (COPD) patients (four patients excluded) and 32 healthy subjects underwent repeated distinct pPTT measurements, standard echocardiography, and pulmonary function testing on the same day. pPTT was defined as the interval from the R or Q-wave in the electrocardiogram to the corresponding pulse wave Doppler peak late systolic (S) 2 or diastolic (D) pulmonary vein flow velocity (pPTT R-S, Q-S, R-D, Q-D). Reproducibility was assessed using Bland-Altman analysis, coefficient of variation (COV), intraclass correlation coefficient (ICC), and power calculations. Associations with right ventricular RV tissue and pulse wave Doppler velocities (RV E', RV S', RV A', RV E, RV A, RV E/E', RV E/A), TAPSE, right ventricular fractional area change, left ventricular systolic and diastolic function (LV ejection fraction, E, A, E/A, E/E', septal E', lateral E'), LA diameters, as well as forced expiratory volume in 1 s, forced vital capacity (FVC) predicted (%), and in liters were analyzed. RESULTS: There was no significant difference and no bias between pPTT measures (p range: .1-.9). COV was in COPD 1.2%-2.3%, in healthy subjects 1.0%-3.1%. ICC ranged from .92 (COPD) to .96 (healthy subjects). In COPD significant correlations were found for pPTT R-S, Q-S and R-D with RV E`, (all > ρ: .49, < p = .0364), pPTT R-S, Q-S with RV E/E` (both > ρ: .49, < p = .0291), pPTT Q-S with RV S´ (ρ: .58, p = .0134), RV A (ρ: .59, p = .0339) and heart rate > ρ: -.39, < p = .0297). pPTT R-S, R-D showed significant correlations with FVC predicted (%) (ρ: .48 p = .0224) and FVC (l) (ρ:.47 p = .0347). CONCLUSIONS: All pPTT measures exhibited high reproducibility. In COPD patients pPTT measures correlate with diastolic right ventricular function. Defining Q as starting point seems clinically advantageous considering electromechanical desynchrony in patients with conduction disorders.

Flexural pulse wave velocity in blood vessels.

Arteriosclerosis is a major risk factor for cardiovascular disease and results in arterial vessel stiffening. Velocity estimation of the pulse wave sent by the heart and propagating into the arteries is a widely accepted biomarker. This symmetrical pulse wave propagates at a speed which is related to the Young's modulus through the Moens Korteweg (MK) equation. Recently, an antisymmetric flexural wave has been observed in vivo. Unlike the symmetrical wave, it is highly dispersive. This property offers promising applications for monitoring arterial stiffness and early detection of atheromatous plaque. However, as far as it is known, no equivalent of the MK equation exists for flexural pulse waves. To bridge this gap, a beam based theory was developed, and approximate analytical solutions were reached. An experiment in soft polymer artery phantoms was built to observe the dispersion of flexural waves. A good agreement was found between the analytical expression derived from beam theory and experiments. Moreover, numerical simulations validated wave speed dependence on the elastic and geometric parameters at low frequencies. Clinical applications, such as arterial age estimation and arterial pressure measurement, are foreseen.

Experiences of Participation in a Study Investigating Feasibility of the Implantable Doppler Probe in Kidney Transplantation: An Embedded Qualitative Study.

OBJECTIVES: Kidney transplant survival can be improved with better graft surveillance postoperatively. In the quest to explore new technologies, we explored the feasibility of an implantable Doppler probe as a blood flow monitoring device in kidney transplant patients. This qualitative study was embeddedin a feasibility trial and aimed to test the device's clinical acceptability and obtain suggestions for the development of the intervention. Objectives included exploring the experiences of feasibility study participants and identifying barriers to the implementation of implantable Doppler probes in clinical practice. MATERIALS AND METHODS: We conducted semi-structured interviews containing open-ended questions with 12 feasibility study participants recruited by purposive sampling. All interviews were audio-recorded with verbatim transcription. Thematic data analysis was performed at the latent level by using an inductive approach with a previously published 6-phase guide. RESULTS: Three key themes emerged: (1) perceived value of the intervention in clinical practice, (2) challenges and barriers to implementation of the intervention, and (3) suggestions forthe development of the intervention. Due to functional limitations and lack of research, medical professional participants revealed clinical equipoise regarding the utility of implantable Doppler probes. However,the device was well received by patient participants. Challenges included device training needs for medical professionals and educational sessions for patients. Innovative ideas for development included the insertion of a display screen, adopting disposable units to reduce overall cost, online access allowing remote monitoring, decreasing external monitoring unit size, and integrating a wireless connection with the probe to reduce signal errors and increase patient safety. CONCLUSIONS: The clinical need for blood flow sensing technology in kidney transplants has been widely acknowledged. Implantable Doppler probes may be a beneficial adjunct in the early postoperative surveillance of kidney transplant patients. However, the device's technical limitations are the main challenges to its acceptance in clinical practice.

Laser speckle flowgraphy has comparable accuracy to indocyanine green fluorescence angiography in assessing bowel blood perfusion.

PURPOSE: To investigate the accuracy of laser speckle flowgraphy (LSFG), a noninvasive method for the quantitative evaluation of blood flow using mean blur rate (MBR) as a blood flow parameter in the assessment of bowel blood perfusion compared to indocyanine green fluorescence angiography (ICG-FA). METHODS: We enrolled 46 patients who underwent left-sided colorectal surgery. LSFG and ICG-FA were applied to assess blood bowel perfusion, with MBR and luminance as parameters, respectively. In both measurement methods, the position where the parameter suddenly decreased was defined as the blood flow boundary line. Subsequently, the blood flow boundaries created after processing the blood vessels flowing into the intestinal tract were determined using LSFG and ICG-FA, and concordance between the two was examined. Blood flow boundaries were visually identified using color tone changes on a color map created based on MBR in LSFG and using differences in luminance in ICG-FA. The distances between the transection line and blood flow boundaries determined using each method were compared. RESULTS: The location of blood flow boundaries matched in 65% (30/46) of cases. Although locations differed in the remaining 35% (16/46), all were located on the anal side near the transection line, and the difference was not clinically significant. The average distances between the transection line and blood flow boundary were 2.76 (SD = 3.25) and 3.71 (SD = 4.26) mm, respectively. There was no statistically significant difference between the two groups (p = 0.38). CONCLUSION: LSFG was shown to have comparable accuracy to ICG-FA, and may be useful for evaluating bowel perfusion.

Association between the arm-to-choroidal circulation time and clinical profile in patients with polypoidal choroidal vasculopathy.

PURPOSE: To investigate the association between the arm-to-choroidal circulation time (ACT) on indocyanine green angiography (IA) and clinical profile in patients with polypoidal choroidal vasculopathy (PCV). STUDY DESIGN: Single-center retrospective study. METHODS: We included 38 eyes of 38 patients with PCV diagnosed using multimodal imaging and did not undergo previous treatment. All patients were treated with monthly aflibercept injections for 3 months and treat-and-extend regimens for the subsequent 12 months. Posterior vortex vein ACT was assessed on the first visit using Heidelberg IA. The patients were divided into two groups: ACT ≥20 s (L group; eight eyes) and ACT <20 s (S group; 30 eyes). The clinical profiles before and after treatment were analyzed to assess associations with ACT. RESULTS: The mean ACT was 16.39±3.3 s (L group: 21.25±1.49 s, women:men=2:6, mean age: 77.3±6.5 years; S group: 15.10±2.17 s, women:men=7:23, mean age: 75.5±6.9 years). No significant difference was observed in the mean subfoveal choroidal thickness between the L and the S groups (176±75 µm vs. 230±79 µm, P=0.10). However, there were significant differences between the L and S groups in retinal fluid accumulation and hemorrhage recurrence (eight/eight eyes, 100% vs. 13/30 eyes, 43%, P<0.001), mean aflibercept injections (8.8±1.6 vs. 7.0±1.6, P<0.01) during the 12-month period, and the number of polypoidal lesions (1.8±0.7 vs. 1.3±0.5, P<0.05). CONCLUSION: Patients with PCV and ACT >20 s are more likely to experience exudative change recurrence in the retina during treatment because they have more polypoidal lesions.

Could Pan-Immune-Inflammation Value be a Marker for the Diagnosis of Coronary Slow Flow Phenomenon?

Inflammation plays a key role in the pathogenesis of the coronary slow flow phenomenon (CSFP). The newly developed inflammatory marker, pan-immune-inflammation value (PIV), is associated with adverse cardiovascular events. This study investigated the predictive value of PIV for diagnosing CSFP in comparison to other inflammation-based markers. A total of 214 patients, 109 in the CSFP group and 105 in the normal coronary flow (NCF) group, were retrospectively included in the study. Coronary flow was calculated using the Thrombolysis in Myocardial Infarction frame count method. In addition to PIV, other inflammatory markers such as neutrophil-lymphocyte ratio, platelet-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII) were calculated for the patients. The average age of patients was 50.3 ± 8.4, with a male ratio of 55.1%. Compared to the NCF group, patients in the CSFP group had higher levels of hyperlipidemia, glucose, triglyceride, NLR, PLR, SII, and PIV, while their high-density lipoprotein cholesterol (HDL-C), was lower (p < 0.05). Logistic regression analysis demonstrated that HDL-C, glucose, triglyceride, and PIV were independent predictor factors for CSFP (p < 0.05). PIV is a strong and independent predictor factor for CSFP and superior in predicting CSFP compared to other inflammatory markers.

Smartphone-based particle tracking velocimetry for the in vitro assessment of coronary flows.

The present study adopts a smartphone-based approach for the experimental characterization of coronary flows. Technically, Particle Tracking Velocimetry (PTV) measurements were performed using a smartphone camera and a low-power continuous wave laser in realistic healthy and stenosed phantoms of left anterior descending artery with inflow Reynolds numbers approximately ranging from 20 to 200. A Lagrangian-Eulerian mapping was performed to convert Lagrangian PTV velocity data to a Eulerian grid. Eulerian velocity and vorticity data obtained from smartphone-based PTV measurements were compared with Particle Image Velocimetry (PIV) measurements performed with a smartphone-based setup and with a conventional setup based on a high-power double-pulsed laser and a CMOS camera. Smartphone-based PTV and PIV velocity flow fields substantially agreed with conventional PIV measurements, with the former characterized by lower average percentage differences than the latter. Discrepancies emerged at high flow regimes, especially at the stenosis throat, due to particle image blur generated by smartphone camera shutter speed and image acquisition frequency. In conclusion, the present findings demonstrate the feasibility of PTV measurements using a smartphone camera and a low-power light source for the in vitro characterization of cardiovascular flows for research, industrial and educational purposes, with advantages in terms of costs, safety and usability.

Computational fluid-structure interaction analysis of the end-to-side radio-cephalic arteriovenous fistula.

BACKGROUND AND OBJECTIVE: In the current work, we present a descriptive fluid-structure interaction computational study of the end-to-side radio-cephalic arteriovenous fistula. This allows us to account for the different thicknesses and elastic properties of the radial artery and cephalic vein. METHODS: The core of the work consists in simulating different arteriovenous fistula configurations obtained by virtually varying the anastomosis angle, i.e. the angle between the end of the cephalic vein and the side of the radial artery. Since the aim of the work is to understand the blood dynamics in the very first days after the surgical intervention, the radial artery is considered stiffer and thicker than the cephalic vein. RESULTS: Our results demonstrate that both the diameter of the cephalic vein and the anastomosis angle play a crucial role to obtain a blood dynamics without re-circulation regions that could prevent fistula failure. CONCLUSIONS: When an anastomosis angle close to the perpendicular direction with respect to the radial artery is combined with a large diameter of the cephalic vein, the recirculation regions and the low Wall Shear Stress (WSS) zones are reduced. Conversely, from a structural point of view, a low anastomosis angle with a large diameter of the cephalic vein reduces the mechanical stress acting on the vessel walls.

Transit time flow measurement in off-pump surgery: is it a functional index of the biological graft integrity?

OBJECTIVE: Transit-time flow measurement (TTFM) represents a valid tool in the assessment of the quality of the anastomosis during coronary artery bypass graft (CABG). Nevertheless, a high variability limits its standardized use, lacking univocally accepted cut-off flow values. Our study analyzes TTFM data collected from a study population that underwent off-pump CABG (OP-CABG), with the aim to differentiate into subgroups according to the presence of diabetes mellitus. PATIENTS AND METHODS: Patients referred to the Cardiovascular Unit of S. Michele Hospital (Caserta, Italy) for coronary artery disease (CAD) and underwent OP-CABG between January 2015 and December 2019 were enrolled, and intraoperative TTFMs data were recruited and evaluated. Mean graft flow (MGF) and pulsatility index (PI) values were collected and analyzed. RESULTS: The study population was composed of 342 patients who underwent OP-CABG with TTFM data regarding 824 grafts. Diabetic patients shared a higher cardiovascular risk profile. The TTFM assessment showed better results for the use of the arterial grafts in diabetic patients, especially for those insulin-dependent; conversely, venous grafts showed worse data with lower MGF and higher PI values. In particular, the anastomoses of the saphenous vein graft with marginal obtuse (MO) coronary artery showed worse MGF results in the insulin-dependent rather than normoglycemic subgroup (28.66 vs. 38.44, p=0.003). CONCLUSIONS: Diabetic patients, especially in the insulin-dependent subgroups, have demonstrated lower MGF and higher PI values collected from venous anastomoses with, conversely, inverse results from the arterial one. These results might be correlated to an altered biological adaptability caused by the effects of the diabetic endocrine disorder.

Numerical investigation of LDL nanoparticle collision in coronary artery grafts with porous wall and different implantation angles and two state of inlet velocity.

This study aimed to reduce the risk of graft occlusion by evaluating the two-phase flow of blood and LDL nanoparticles in coronary artery grafts. The study considered blood as an incompressible Newtonian fluid, with the addition of LDL nanoparticles, and the artery wall as a porous medium. Two scenarios were compared, with constant inlet velocity (CIV) and other with pulsatile inlet velocity (PIV), with LDL nanoparticles experiencing drag, wall-induced lift, and induced Saffman lift forces, or drag force only. The study also evaluated the concentration polarization of LDLs (CP of LDLs) near the walls, by considering the artery wall with and without permeation. To model LDL nanoparticles, the study randomly injected 100, 500, and 1000 nanoparticles in three release states at each time step, using different geometries. Numerical simulations were performed using COMSOL software, and the results were presented as relative collision of nanoparticles to the walls in tables, diagrams, and shear stress contours. The study found that a graft implantation angle of 15° had the most desirable conditions compared to larger angles, in terms of nanoparticle collision with surfaces and occlusion. The nanoparticle release modes behaved similarly in terms of collision with the surfaces. A difference was observed between CIV and PIV. Saffman lift and wall-induced lift forces having no effect, possibly due to the assumption of a porous artery wall and perpendicular outlet flow. In case of permeable artery walls, relative collision of particles with the graft wall was larger, suggesting the effect of CP of LDLs.

Evaluating the accuracy of cerebrovascular computational fluid dynamics modeling through time-resolved experimental validation.

Accurate modeling of cerebral hemodynamics is crucial for better understanding the hemodynamics of stroke, for which computational fluid dynamics (CFD) modeling is a viable tool to obtain information. However, a comprehensive study on the accuracy of cerebrovascular CFD models including both transient arterial pressures and flows does not exist. This study systematically assessed the accuracy of different outlet boundary conditions (BCs) comparing CFD modeling and an in-vitro experiment. The experimental setup consisted of an anatomical cerebrovascular phantom and high-resolution flow and pressure data acquisition. The CFD model of the same cerebrovascular geometry comprised five sets of stationary and transient BCs including established techniques and a novel BC, the phase modulation approach. The experiment produced physiological hemodynamics consistent with reported clinical results for total cerebral blood flow, inlet pressure, flow distribution, and flow pulsatility indices (PI). The in-silico model instead yielded time-dependent deviations between 19-66% for flows and 6-26% for pressures. For cerebrovascular CFD modeling, it is recommended to avoid stationary outlet pressure BCs, which caused the highest deviations. The Windkessel and the phase modulation BCs provided realistic flow PI values and cerebrovascular pressures, respectively. However, this study shows that the accuracy of current cerebrovascular CFD models is limited.

Cerebrovascular carbon dioxide reactivity is intact in chronic kidney disease.

Chronic kidney disease (CKD) is characterized by an elevated risk for cerebrovascular disease including stroke. One mechanism that may contribute to this heightened risk is an impairment in cerebrovascular carbon dioxide reactivity (CVR). We compared CVR between CKD patients stages III-IV and controls (CON) without CKD but matched for hypertension and diabetes status. CVR was measured via 5% CO2 inhalation followed by voluntary hyperventilation in 14 CKD and 11 CON participants while mean arterial pressure, end-tidal carbon dioxide, and middle cerebral artery blood velocity (MCAv) were measured continuously. CVR was quantified as the linear relationship between etCO2 and MCAv. We observed no difference in CVR between groups. Hypercapnic CVR: CKD = 1.2 ± 0.9 cm/s/mm Hg, CON = 1.3 ± 0.8 cm/s/mm Hg, hypocapnic CVR: CKD = 1.3 ± 0.9 cm/s/mm Hg, CON = 1.5 ± 0.7 cm/s/mm Hg, integrated CVR: CKD = 1.5 ± 1.1 cm/s/mm Hg, CON = 1.7 ± 0.8 cm/s/mm Hg, p ≥ 0.48. Unexpectedly, CVR was inversely related to estimated glomerular filtration rate in CKD (R2 = 0.37, p = 0.02). We report that CVR remains intact in CKD and is inversely related to eGFR. These findings suggest that other mechanisms beyond CVR contribute to the elevated stroke risk observed in CKD.

Transient time flow measurement in arterial grafts.

Coronary artery bypass grafting (CABG) is one of the foundations of treatment for coronary artery disease. While it has improved substantially since its inception more than 50 years ago, including a rising use of multiple arterial grafting, intraoperative quality assessment is yet to be disseminated as an integral part of the procedure. Herein we review the fundamentals of intraoperative quality assessment in CABG using transient time flow measurement (TTFM) with a focus on its use in arterial grafting.

Safety and efficacy of the second-generation cryoballoon for left atrial appendage electrical isolation in canines.

AIMS: Left atrial appendage electrical isolation (LAAEI) has demonstrated a significant enhancement in the success rate of atrial fibrillation (AF) ablation. Nevertheless, concerns persist about the safety of LAAEI, particularly regarding alterations in left atrial appendage (LAA) flow velocity and the potential risks of thrombus. This study aimed to assess the efficacy and safety of LAAEI, investigating changes in LAA flow velocity in canines. METHODS AND RESULTS: The study comprised a total of 10 canines. The LAAEI procedure used by a 23 mm cryoballoon of the second generation was conducted at least 180 s. Intracardiac ultrasonography (ICE) was employed to quantify the velocity flow of the LAA both prior to and following LAAEI. Following a 3-month period, subsequent evaluations were performed to assess the LAA velocity flow and the potential reconnection. Histopathological examination was conducted. Left atrial appendage electrical isolation was effectively accomplished in all canines, resulting in a 100% acute success rate (10/10). The flow velocity in the LAA showed a notable reduction during LAAEI as compared with the values before the ablation procedure (53.12 ± 5.89 vs. 42.01 ± 9.22 cm/s, P = 0.007). After the follow-up, reconnection was observed in four canines, leading to a success rate of LAAEI of 60% (6/10). The flow velocity in the LAA was consistently lower (53.12 ± 5.89 vs. 44.33 ± 10.49 cm/s, P = 0.006), and no blood clot development was observed. The histopathological study indicated that there was consistent and complete injury to the LAA, affecting all layers of its wall. The injured tissue was subsequently replaced by fibrous tissue. CONCLUSION: The feasibility of using cryoballoon ablation for LAAEI was confirmed in canines, leading to a significant reduction of LAA flow velocity after ablation. Some restoration of LAA flow velocity after ablation may be linked to the passive movement of the LAA and potential reconnecting. However, this conclusion is limited to animal study; more clinical data are needed to further illustrate the safety and accessibility of LAAEI in humans.

Lesion Eccentricity Plays a Key Role in Determining the Pressure Gradient of Serial Stenotic Lesions: Results from a Computational Hemodynamics Study.

PURPOSE: In arterial disease, the presence of two or more serial stenotic lesions is common. For mild lesions, it is difficult to predict whether their combined effect is hemodynamically significant. This study assessed the hemodynamic significance of idealized serial stenotic lesions by simulating their hemodynamic interaction in a computational flow model. MATERIALS AND METHODS: Flow was simulated with SimVascular software in 34 serial lesions, using moderate (15 mL/s) and high (30 mL/s) flow rates. Combinations of one concentric and two eccentric lesions, all 50% area reduction, were designed with variations in interstenotic distance and in relative direction of eccentricity. Fluid and fluid-structure simulations were performed to quantify the combined pressure gradient. RESULTS: At a moderate flow rate, the combined pressure gradient of two lesions ranged from 3.8 to 7.7 mmHg, which increased to a range of 12.5-24.3 mmHg for a high flow rate. Eccentricity caused an up to two-fold increase in pressure gradient relative to concentric lesions. At a high flow rate, the combined pressure gradient for serial eccentric lesions often exceeded the sum of the individual lesions. The relative direction of eccentricity altered the pressure gradient by 15-25%. The impact of flow pulsatility and wall deformability was minor. CONCLUSION: This flow simulation study revealed that lesion eccentricity is an adverse factor in the hemodynamic significance of isolated stenotic lesions and in serial stenotic lesions. Two 50% lesions that are individually non-significant can combine more often than thought to hemodynamic significance in hyperemic conditions.

Relationship between effective blood flow rate and clinical outcomes in maintenance hemodialysis patients: a single-center study.

The association between blood flow rate (BFR) and clinical outcomes in patients undergoing maintenance hemodialysis (MHD) is inconclusive. This retrospective study included 175 patients undergoing MHD treatment between July 2015 and March 2022, divided into two groups based on time-averaged effective blood flow rate (eBFR) median value. We investigated arteriovenous fistula (AVF) outcomes and the association of eBFR with all-cause mortality and new major adverse cardiovascular events (MACE). Mean ± SD and median time-averaged eBFR values were 276 ± 24 and 275 mL/min, respectively. After adjusting for relevant factors including age, sex, vintage, diabetes, CVD, receiving hemodiafiltration (HDF) treatment and spKt/V, Cox models indicated a low time-averaged eBFR (≤ 275 ml/min) was associated with increased risks of all-cause mortality (hazard ratio [HR] 14.18; 95% confidence interval [CI], 3.14-64.1) and new MACE (HR 3.76; 95% CI, 1.91-7.40) in MHD patients. Continuous Cox models demonstrated each 20 ml/min increase in eBFR linked to a 63% decrease in the risk of all-cause mortality (HR: 0.37, 95% CI: 0.23-0.59) and a 38% decrease in the occurrence of new MACE (HR: 0.62, 95% CI: 0.46-0.84). There was no significant difference in AVF outcomes between the two groups. Our study noted higher eBFR (>275 mL/min) is associated with lower risks of both all-cause mortality and new MACE compared with low eBFR (≤275 mL/min). Increased eBFR is not associated with a higher risk of AVF failure.