Abnormal Flow Patterns Research Articles

Intraventricular 4D blood flow: adding a fourth dimension to cardiovascular functional analysis by magnetic resonance imaging

Introduction Echocardiography is a standard tool for evaluating the cardiac chambers, valves and great vessels. Recent data shows techniques such as strain analysis display subtle contractile deficits long before ejection fraction (EF) drops, and this has already been linked to poor outcome. 4D colour doppler is a recent technical advancement, however its temporal resolution remains limited so far. Cardiovascular magnetic resonance (CMR) offers similar assessment of myocardial function, vessels and valves, but beyond that also offers unmatched tissue characterization (fibrosis, scar, edema, oxygenation, metabolics). A novel development in this field is 4D flow CMR, which allows for visualization and quantification of multiple parameters like blood flow velocity, direction, pattern, wall shear stress and kinetic energy deposition. Cardiac diseases in early stages may not yet feature a reduced EF but may already display abnormal 4D flow patterns, which may reduce cardiac index and increase ventricular wall stress. In this study we applied CMR-based 4D intraventricular blood flow assessment in participants with normal left ventricular (LV) systolic function. Methods Using a 3T clinical MRI, seven participants underwent a non-contrast exam (one healthy control under 35 years, five controls older than 50 years, one patient with heart failure and preserved EF (HFpEF)). A 4D block of the thoracic cavity was acquired and blood flow patterns in the left ventricle were assessed for direct flow (blood that enters and leaves the ventricle during one heartbeat), residual volume (blood that remains in the LV cavity for at least 2 heartbeats), along with delayed ejection and retained flow (figure). Furthermore, ventricular function and strain by feature tracking were measured. Results While participants had an LVEF of 65±3% and a cardiac index of greater than 3.1±0.4 L/min/m2, there was marked variation in intraventricular 4D blood flow patterns (figure). The patient with heart failure had the largest residual volume and lowest direct flow, whereas the young healthy control had the highest direct flow and lowest residual volume. Residual volume in the older controls ranged in between these two points. Furthermore, a larger direct flow was correlated with greater longitudinal strain (r = -0.886, p = 0.033), while there was a trend of larger residual volume to be associated with poorer global longitudinal strain (r = 0.829, p = 0.058). Discussion In a small cohort, CMR-derived patterns of intraventricular 4D blood flow and ventricular wall strain are associated despite quantitatively normal LVEF. Although acquisition, processing and quantification in 4D flow CMR are still time-consuming, the quantification of 4D blood flow in cardiac chambers and great vessels has the potential to offer a comprehensive evaluation of cardiovascular haemodynamics under normal and pathological conditions. Larger studies are required.

The effects of age at correction of aortic coarctation and recurrent obstruction on adolescent patients: MRI evaluation of wall shear stress and pulse wave velocity

BackgroundCoarctation patients before curative reconstruction are exposed to abnormal flow patterns which potentially could cause wall deterioration. This study evaluated the effect of age at correction on the pulse wave velocity (PWV) and peak wall shear stress (WSS) in adolescent patients with corrected coarctation. Effects of valve morphology and presence of reobstruction were also evaluated.MethodsTwenty-one patients aged 13.7 ± 2.6 years (mean ± standard deviation) were included (bicuspid aortic valve, n = 14; reobstruction, n = 9). Mean age at correction was 1.0 ± 1.8 years. PWV was determined from two high-temporal through-plane phase-contrast magnetic resonance imaging (MRI) acquisitions, for two segments: ascending aorta plus aortic arch and descending aorta. WSS was determined from four-dimensional flow MRI. Peak WSS over five systolic phases was determined for ascending aorta, aortic arch, and descending aorta.ResultsPatients with tricuspid aortic valve showed a significant correlation between the age at correction and descending aorta PWV (rs = 0.80, p = 0.010). Significant differences were found between patients without and with reobstruction for peak WSS in the aortic arch (3.9 ± 1.3 Pa versus 6.5 ± 2.2 Pa, respectively; p = 0.003) and descending aorta (5.0 ± 1.3 Pa versus 6.7 ± 1.1 Pa, respectively; p = 0.005).ConclusionsA prolonged period of abnormal haemodynamic exposure may result in increased aortic wall stiffening. The increased peak WSS as results of a reobstruction possibly promotes different disease progression, which endorse longitudinal follow-up examination of corrected coarctation patients.

Left ventricle vortex detection by 3D + t phase contrast MRI: a feasibility study

The motivation to focus on coherent structure detection in cardiovascular systems is two-fold: 1) the ability to reliably detect abnormal inefficient flow patterns from a normal optimal state; and ...

Maternal Venous Hemodynamic Dysfunction in Proteinuric Gestational Hypertension: Evidence and Implications.

This review summarizes current knowledge from experimental and clinical studies on renal function and venous hemodynamics in normal pregnancy, in gestational hypertension (GH) and in two types of preeclampsia: placental or early-onset preeclampsia (EPE) and maternal or late-onset (LPE) preeclampsia, presenting at <34 weeks and ≥34 weeks respectively. In addition, data from maternal venous Doppler studies are summarized, showing evidence for (1) the maternal circulation functioning closer to the upper limits of capacitance than in non-pregnant conditions, with intrinsic risks for volume overload, (2) abnormal venous Doppler measurements obtainable in preeclampsia, more pronounced in EPE than LPE, however not observed in GH, and (3) abnormal venous hemodynamic function installing gradually from first to third trimester within unique pathways of general circulatory deterioration in GH, EPE and LPE. These associations have important clinical implications in terms of screening, diagnosis, prevention and management of gestational hypertensive diseases. They invite for further hypothesis-driven research on the role of retrograde venous congestion in the etiology of preeclampsia-related organ dysfunctions and their absence in GH, and also challenge the generally accepted view of abnormal placentation as the primary cause of preeclampsia. The striking similarity between abnormal maternal venous Doppler flow patterns and those observed at the ductus venosus and other abdominal veins of the intra-uterine growth restricted fetus, also invites to explore the role of venous congestion in the intra-uterine programming of some adult diseases.

Myocardial bridging and endothelial dysfunction – Computational fluid dynamics study

Myocardial bridging (MB) is associated with endothelial dysfunction in patients with angina and non-obstructive coronary artery disease. This study aims to determine if there is a link between abnormal blood flow patterns and endothelial dysfunction in patients with MB. Ten patients with MB in their left anterior descending (LAD) artery were selected, 5 of whom had endothelial dysfunction and 5 had no endothelial dysfunction based on their response to acetylcholine. Similarly, 10 patients without MB in their LAD, 5 of whom had endothelial dysfunction and 5 of whom had no endothelial dysfunction, were studied as a control group. Transient computational fluid dynamics simulations were performed to derive wall shear stress (WSS) over the entire vessel including proximal, middle and distal segments. Patients with MB and endothelial dysfunction had lower WSS in the proximal LAD and greater WSS in the mid-LAD than patients with MB but without endothelial dysfunction. When comparing patients with endothelial dysfunction, those with MB had significantly lower shear stress in the proximal LAD (0.32 ± 0.14 Pa (with MB) vs 0.71 ± 0.38 Pa (without MB), p = 0.01) and greater shear stress in the mid-LAD (2.81 ± 1.20 Pa (with MB) vs 1.66 ± 0.31 Pa (without MB), p = 0.014) than patients without MB. Our findings demonstrated that the presence of MB significantly contributes to low WSS and endothelial dysfunction relationship.

Abnormal flow pattern in Marfan patients is related to aortic geometric features: A 4D flow MRI study

IntroductionAscending aorta aneurysm and dissection are the most common cardiovascular complications affecting Marfan syndrome patients (MFS). Recent large increase in life expectancy of MFS driven the growing prevalence of descending aorta (DAo) dilation and dissection. Despite local abnormal vortices in the proximal Dao were related to local dilation, their origins have never been explored. We investigated the link between aortic geometrical characteristics and abnormal flow pattern in the thoracic aorta of MFS.MethodsFifty-tree MFS without significant aortic valve disease and forty age-matched healthy volunteers (HV) were prospectively included in 4D flow-MRI study, obtaining flow field and angiography. Spatial distribution of flow (in-plane rotational flow (IRF) and systolic flow reversal ratio (SFRR)) and geometric (diameter, ellipticity and curvature) parameters were investigated.ResultsCompared to HV, MFS presented larger aortic diameters only in the proximal AAo (p < 0.001) and DAo (p = 0.028). Increased ellipticity and a more distal location for the peak of aortic curvature were evident, even in the absence of dilation. Through most of the thoracic aorta, IRF was substantially lower in MFS, while SFRR was larger. Interestingly, non-dilated MFS had decreased IRF in the thoracic aorta compared to HV, although SFRR was not increased. Statistically-significant bivariate relations were found between arch IRF and arch ellipticity (R = −0.34) and proximal DAo peak curvature (R = −0.35). Local diameter was negatively correlated with local IRF (R = −0.3) and positively correlated to local SFRR (R = 0.605).ConclusionsMFS presented altered ellipticity and curvature distribution, which are related to abnormal flow patterns even in the absence of dilation.

Aortic stiffness in aortic stenosis assessed by cardiovascular MRI: a comparison between bicuspid and tricuspid valves

ObjectivesTo compare aortic size and stiffness parameters on MRI between bicuspid aortic valve (BAV) and tricuspid aortic valve (TAV) patients with aortic stenosis (AS).MethodsMRI was performed in 174 patients with asymptomatic moderate-severe AS (mean AVAI 0.57 ± 0.14 cm2/m2) and 23 controls on 3T scanners. Valve morphology was available/analysable in 169 patients: 63 BAV (41 type-I, 22 type-II) and 106 TAV. Aortic cross-sectional areas were measured at the level of the pulmonary artery bifurcation. The ascending and descending aorta (AA, DA) distensibility, and pulse wave velocity (PWV) around the aortic arch were calculated.ResultsThe AA and DA areas were lower in the controls, with no difference in DA distensibility or PWV, but slightly lower AA distensibility than in the patient group. With increasing age, there was a decrease in distensibility and an increase in PWV. After correcting for age, the AA maximum cross-sectional area was higher in bicuspid vs. tricuspid patients (12.97 [11.10, 15.59] vs. 10.06 [8.57, 12.04] cm2, p < 0.001), but there were no significant differences in AA distensibility (p = 0.099), DA distensibility (p = 0.498) or PWV (p = 0.235). Patients with BAV type-II valves demonstrated a significantly higher AA distensibility and lower PWV compared to type-I, despite a trend towards higher AA area.ConclusionsIn patients with significant AS, BAV patients do not have increased aortic stiffness compared to those with TAV despite increased ascending aortic dimensions. Those with type-II BAV have less aortic stiffness despite greater dimensions. These results demonstrate a dissociation between aortic dilatation and stiffness and suggest that altered flow patterns may play a role.Key Points• Both cellular abnormalities secondary to genetic differences and abnormal flow patterns have been implicated in the pathophysiology of aortic dilatation and increased vascular complications associated with bicuspid aortic valves (BAV).• We demonstrate an increased ascending aortic size in patients with BAV and moderate to severe AS compared to TAV and controls, but no difference in aortic stiffness parameters, therefore suggesting a dissociation between dilatation and stiffness.• Sub-group analysis showed greater aortic size but lower stiffness parameters in those with BAV type-II AS compared to BAV type-I.

4-D flow MRI aortic 3-D hemodynamics and wall shear stress remain stable over short-term follow-up in pediatric and young adult patients with bicuspid aortic valve

Children with bicuspid aortic valve (BAV) are at risk for serious complications including aortic valve stenosis and aortic rupture. Most studies investigating biomarkers predictive of BAV complications are focused on adults. To investigate whether hemodynamic parameters change over time in children and young adults with BAV by comparing baseline and follow-up four-dimensional (4-D) flow MRI examinations. We retrospectively included 19 children and young adults with BAV who had serial 4-D flow MRI exams (mean difference in scan dates 1.8±1.0 [range, 0.6-3.4years]). We compared aortic peak blood flow velocity, three-dimensional (3-D) wall shear stress, aortic root and ascending aortic (AAo) z-scores between baseline and follow-up exams. We generated systolic streamlines for all patients and visually compared their baseline and follow-up exams. The only significant difference between baseline and follow-up exams occurred in AAo z-scores (3.12±2.62 vs. 3.59±2.76, P<0.05) indicating growth of the AAo out of proportion to somatic growth. There were no significant changes in either peak velocity or 3-D wall shear stress between baseline and follow-up exams. Ascending aortic peak velocity at baseline correlated with annual change in AAo z-score (r=0.58, P=0.009). Visual assessment revealed abnormal blood flow patterns, which were unique to each patient and remained stable between baseline and follow-up exams. In our pediatric and young adult BAV cohort, hemodynamic markers and systolic blood flow patterns remained stable over short-term follow-up despite significant AAo growth, suggesting minimal acute disease progression. Baseline AAo peak velocity was a predictor of AAo dilation and might help in determining pediatric patients with BAV who are at risk of increased AAo growth.

P6500Intrinsic aortic ellipticity and curvature are related to abnormal flow pattern in Marfan patients: a 4D flow MRI study

P6500Intrinsic aortic ellipticity and curvature are related to abnormal flow pattern in Marfan patients: a 4D flow MRI study

Diagnostic Accuracy of Doppler Ultrasonography in the Antenatal Diagnosis of Abnormal Placental Invasion Secondary to Placenta Praevia

Objective: To determine the diagnostic accuracy of Doppler Ultrasonography in a tertiary care hospital, for the antenatal diagnosis of abnormal placental invasion secondary to placenta praevia, taking operative findings of caesarean section as gold standard.&#x0D; Methods: This is a cross-sectional study carried out in the Department of Radiology, Liaquat National Hospital, Karachi, from 1st August 2013 to 31st July 2014. A total of 591 pregnant women (multipara) having placenta praevia were included in this study. The diagnosis of abnormal placental invasion was made by Doppler USG and compared with operative findings of caesarean section as gold standard. A predesigned pro forma was used to document findings. SPSS version 17 was used for all sta- tistical analysis.&#x0D; Results: Sensitivity, specificity, positive and negative predictive value as well as accuracy of Doppler ultrasonography (USG) in the detection of abnormal placental invasion was found to be 84.8%, 93.9%, 91.8%, 88.5% and 89.95%, respectively.&#x0D; Conclusion: Any persistent placenta praevia, will benefit from antenatal Doppler USG studies to identify abnormal utero-placental vascular flow patterns and these findings clearly aid in the management of this most challenging obstetric complication.

Anomaly of Haughton type D left cervical aortic arch in combination with type B dissection: case report and literature review

BackgroundThe anomaly of cervical aortic arch is a rare phenomenon first described by Reid in 1914 and categorized by Haughton in 1975. The left cervical aortic arch Type D consisting of an ipsilateral descending aorta and coarctation or aneurysmatic formation of the arch demonstrates a complicated form requiring surgical management. Because of its rarity and unspecific symptoms only few cases are documented with the focus on surgical management.Case presentationA 43-year old, asymptomatic woman presented with a mediastinal mass overlapping the aortic arch region in a routine x-ray. For verification, a computed tomography was performed and revealed incidentally a type B dissection originating from an aneurysm of a left cervical arch with a maximum diameter of 6 cm. Because of the huge diameter and the potential risk of rupture, an urgent surgical repair was planned. Surgical access was performed through median sternotomy and an additional left lateral thoracic incision through the fourth intercostal space. Simultaneously to the preparation, partial cardiopulmonary bypass was installed in the left groin. After preparation of the recurrent and phrenic nerve and the supraaortic branches, the descending aorta was clamped. Before the distal anastomosis to a straight graft, we performed a fenestration of the dissection membrane about a length of 5 cm to preserve the perfusion of both lumina. Then, the straight graft was sutured to the proximal part of descending aorta. The left axillary artery originated directly from the aneurysm and was dissected and reimplanted with a separate 8 mm sidegraft to the straight graft between the distal arch and proximal descending aorta. The patient was extubated on first postoperative day and recovered well.ConclusionThe left cervical aortic arch type D is a rare disease, which is prone to aneurysm formation due to abnormal flow patterns and tortuosity of the aorta. The difficulty lays in the identification of the pathology, especially in the physical examination, since a pulsating mass or cervical murmur seem to be the most specific symptoms in the majority of young, female patients. If diagnosed, surgical therapy with resection of the aneurysm and reimplantation of the axillary artery under cardiopulmonary bypass demonstrates the treatment of choice.

Differential flow improvements after valve replacements in bicuspid aortic valve disease: a cardiovascular magnetic resonance assessment

BackgroundAbnormal aortic flow patterns in bicuspid aortic valve disease (BAV) may be partly responsible for the associated aortic dilation. Aortic valve replacement (AVR) may normalize flow patterns and potentially slow the concomitant aortic dilation. We therefore sought to examine differences in flow patterns post AVR.MethodsNinety participants underwent 4D flow cardiovascular magnetic resonance: 30 BAV patients with prior AVR (11 mechanical, 10 bioprosthetic, 9 Ross procedure), 30 BAV patients with a native aortic valve and 30 healthy subjects.ResultsThe majority of subjects with mechanical AVR or Ross showed normal flow pattern (73% and 67% respectively) with near normal rotational flow values (7.2 ± 3.9 and 10.6 ± 10.5 mm2/ms respectively vs 3.8 ± 3.1 mm2/s for healthy subjects; both p > 0.05); and reduced in-plane wall shear stress (0.19 ± 0.13 N/m2 for mechanical AVR vs. 0.40 ± 0.28 N/m2 for native BAV, p < 0.05). In contrast, all subjects with a bioprosthetic AVR had abnormal flow patterns (mainly marked right-handed helical flow), with comparable rotational flow values to native BAV (20.7 ± 8.8 mm2/ms and 26.6 ± 16.6 mm2/ms respectively, p > 0.05), and a similar pattern for wall shear stress. Data before and after AVR (n = 16) supported these findings: mechanical AVR showed a significant reduction in rotational flow (30.4 ± 16.3 → 7.3 ± 4.1 mm2/ms; p < 0.05) and in-plane wall shear stress (0.47 ± 0.20 → 0.20 ± 0.13 N/m2; p < 0.05), whereas these parameters remained similar in the bioprosthetic AVR group.ConclusionsAbnormal flow patterns in BAV disease tend to normalize after mechanical AVR or Ross procedure, in contrast to the remnant abnormal flow pattern after bioprosthetic AVR. This may in part explain different aortic growth rates post AVR in BAV observed in the literature, but requires confirmation in a prospective study.

The Predictor Role of the Aqueduct Cerebrospinal Fluid Flow on Endoscopic Third Ventriculostomy: Explication on Assumption Physical Model.

To evaluate the cerebrospinal fluid (CSF) flow dynamics in the aqueductus sylvii of patients with obstructive hydrocephalus who underwent endoscopic third ventriculostomy (ETV) and to predict ventriculostomy patency via aqueduct flow measurements. Twenty-four patients with obstructive hydrocephalus caused by primary aqueduct stenosis who underwent ETV were included in the study. All the patients underwent conventional and cine magnetic resonance imaging before and after treatment. The flow of CSF in the aqueduct of Sylvius and prepontine cistern was assessed, and the diameter of the third ventricle was also measured. Increase in the aqueduct flow velocity after a successful ETV was supported by the assumption physical model that highlights a possible mechanism that explains the clinical findings. The flow pattern and velocity in the prepontine cistern and aqueduct were normal in 17 out of 24 patients who responded to ETV clinically. However, seven patients who did not respond to ETV had an abnormal flow pattern in both the prepontine cistern and aqueduct. The flow pattern in the aqueduct was normalised and velocity was increased compared with those of preoperative values after a successful ETV. The flow of CSF in the prepontine cistern is routinely used for ventriculostomy patency assessment. In addition, aqueduct measurements may be useful in predicting ventriculostomy patency. The physical model provides valuable insights on a possible mechanism that affected the experimental data.

Do uroflowmetry and post - void residual urine tests necessary in children with primary nocturnal enuresis?

ABSTRACTObjectives:To examine the benefits of repetitive uroflowmetry and post void residual urine (PVR) tests in children with primary nocturnal enuresis (PNE).Material and methods:Children aged ≥6 years with PNE who visited our clinics for management of enuresis were included for study. Patients were requested to complete a questionnaire including baseline characteristics and Dysfunctional Voiding Symptom Score (DVSS), 2-day bladder diary, and Rome III criteria for constipation. Two uroflowmetry and PVR tests were requested. Children with congenital or neurogenic genitourinary tract disorders were excluded. All children underwent urotherapy and desmopressin combined with anticholinergics or laxatives if indicated. The definition of abnormal flow patterns (≥1 abnormal), elevated PVR (≥1 abnormal), small maximal voided volume (MVV), nocturnal polyuria (NP) and response to treatment complied with the ICCS standardization document. Kaplan-Meier survival analysis and Cox proportional-hazards regression tests were used to evaluate the predictors of response.Results:In total, 100 children aged 8.5±2.3 years were enrolled for study (M: F=66:34) with 7.3±7.4 months of follow-up. Poor correlation was observed between DVSS/small MVV and PVR (p>0.05). Univariate analysis revealed that elevated PVR is associated with significantly less hazard of complete response to medical treatment (HR: 0.52, p=0.03), while not significantly associated with abnormal flow patterns, NP, constipation or small MVV. Multivariate analysis revealed that only elevated PVR (HR 0.30, 95% CI 0.12-0.80) and NP (HR 2.8, 95% CI 1.10-7.28) were significant predictors for complete response.Conclusions:In managing pediatric enuresis, elevated PVR is a significant predictor for lower chance of complete response to treatment whether they had high DVSS or not.

Pelvic floor electromyography and urine flow patterns in children with vesicoureteral reflux and lower urinary tract symptoms.

ABSTRACTObjective:To determine the different urine flow patterns and active pelvic floor electromyography (EMG) during voiding in children with vesicoureteral reflux (VUR) as well as presenting the prevalence of lower urinary tract symptoms in these patients. Materials and Methods: We retrospectively reviewed the charts of children diagnosed with VUR after toilet training from Sep 2013 to Jan 2016. 225 anatomically and neurologically normal children were included. The reflux was diagnosed with voiding cystourethrography. The study was comprised an interview by means of a symptom questionnaire, a voiding diary, uroflowmetry with EMG and kidney and bladder ultrasounds. Urine flow patterns were classified as bell shape, staccato, interrupted, tower and plateau based on the current International Children's Continence Society guidelines.Results:Of 225 children with VUR (175 girls, 50 boys), underwent uroflowmetry + EMG, 151 (67.1%) had an abnormal urine flow pattern. An active pelvic floor EMG during voiding was confirmed in 113 (50.2%) children. The flow patterns were staccato in 76 (33.7 %), interrupted in 41 (18.2%), Plateau in 26 (11.5%), tower in 12 (5.3%) and a bell shape or normal pattern in 70 (31.5%). Urinary tract infection, enuresis and constipation respectively, were more frequent symptoms in these patients.Conclusions:Bladder/bowel dysfunction is common in patients with VUR that increases the risk of breakthrough urinary tract infections in children receiving antibiotic prophylaxis and reduces the success rate for endoscopic injection therapy. Therefore investigation of voiding dysfunction with primary assessment tools can be used prior to treating VUR.

Energetics of Blood Flow in Cardiovascular Disease: Concept and Clinical Implications of Adverse Energetics in Patients With a Fontan Circulation.

Visualization and quantification of the adverse effects of distorted blood flow are important emerging fields in cardiology. Abnormal blood flow patterns can be seen in various cardiovascular diseases and are associated with increased energy loss. These adverse energetics can be measured and quantified using 3-dimensional blood flow data, derived from computational fluid dynamics and 4-dimensional flow magnetic resonance imaging, and provide new, promising hemodynamic markers. In patients with palliated single-ventricular heart defects, the Fontan circulation passively directs systemic venous return to the pulmonary circulation in the absence of a functional subpulmonary ventricle. Therefore, the Fontan circulation is highly dependent on favorable flow and energetics, and minimal energy loss is of great importance. A focus on reducing energy loss led to the introduction of the total cavopulmonary connection (TCPC) as an alternative to the classical Fontan connection. Subsequently, many studies have investigated energy loss in the TCPC, and energy-saving geometric factors have been implemented in clinical care. Great advances have been made in computational fluid dynamics modeling and can now be done in 3-dimensional patient-specific models with increasingly accurate boundary conditions. Furthermore, the implementation of 4-dimensional flow magnetic resonance imaging is promising and can be of complementary value to these models. Recently, correlations between energy loss in the TCPC and cardiac parameters and exercise intolerance have been reported. Furthermore, efficiency of blood flow through the TCPC is highly variable, and inefficient blood flow is of clinical importance by reducing cardiac output and increasing central venous pressure, thereby increasing the risk of experiencing the well-known Fontan complications. Energy loss in the TCPC will be an important new hemodynamic parameter in addition to other well-known risk factors such as pulmonary vascular resistance and can possibly be improved by patient-specific surgical design. This article describes the theoretical background of mechanical energy of blood flow in the cardiovascular system and the methods of calculating energy loss, and it gives an overview of geometric factors associated with energy efficiency in the TCPC and its implications on clinical outcome. Furthermore, the role of 4-dimensional flow magnetic resonance imaging and areas of future research are discussed.

Feasibility of Computational Fluid Dynamics for Evaluating the Intraventricular Hemodynamics in Single Right Ventricle Based on Echocardiographic Images.

This study introduced a combined computational fluid dynamics (CFD) and echocardiography methodology to simulate blood flow in the single right ventricle (SRV) and normal ventricles to study the intraventricular flow. Derived from echocardiographic image loops, CFD-based three-dimensional (3D) flow models of normal subject's left ventricle (LV) and right ventricle (RV) and SRV with and without heart failure at three characteristic diastolic statuses were reconstructed. The CFD derived morphological and functional measurements in normal ventricles and the SRV were validated with echocardiography. The vortex in the normal ventricles and the SRV were studied. The morphological and functional measurements derived from CFD modeling and echocardiography were comparable, and both methods demonstrated the larger volume and higher spherical index in the SRV, in particular the SRV with heart failure. All the vortices in the SRV were smaller than those in the normal control subject's LV and RV, notably with heart failure. Unlike normal LV and RV, no vortex ring was observed in the SRV. Echocardiography-based CFD demonstrated the feasibility of quantifying ventricular morphology and function; in addition, CFD can detect the abnormal flow pattern (smaller or obliterated vortices) in the SRV when compared with normal ventricles.

Duplex Sonography of Vertebral Arteries for Evaluation of Patients with Acute Vertigo

We evaluated the role of vertebral artery extracranial color-coded duplex sonography (VAECCS) in predicting vertebrobasilar stroke in consecutive patients presenting to the emergency department with vertigo of suspected ischemic origin. The final diagnosis was established by a panel of experts consisting of an emergency physician, a neurologist, and an otoneurologist. Vertebrobasilar stroke was diagnosed when an acute brain ischemic lesion congruent with symptoms was detected by neuroimaging during the index visit or a stroke was diagnosed within a 3-mo period after emergency department presentation. Among 126 patients, 28 (22%) were diagnosed with vertebrobasilar stroke. Fifteen (75%) of 20 patients with abnormal VAECCS results and 13 (12%) of 106 with normal VAECCS results had a final diagnosis of vertebrobasilar stroke. The sensitivity and specificity of VAECCS were 53.6% and 94.9%, respectively. Detecting an abnormal flow pattern at VAECCS significantly increased the risk of vertebrobasilar stroke (odds ratio = 21.5). The flow patterns most frequently related to vertebrobasilar stroke were absence of flow and high resistance pattern velocity (odds ratio = 9.3 and 22.7, respectively). VAECCS predicts vertebrobasilar stroke and could be a useful bedside screening tool in patients with vertigo.

Left Atrial 4D Blood Flow Dynamics and Hemostasis following Electrical Cardioversion of Atrial Fibrillation.

Background: Electrical cardioversion in patients with atrial fibrillation is followed by a transiently impaired atrial mechanical function, termed atrial stunning. During atrial stunning, a retained risk of left atrial thrombus formation exists, which may be attributed to abnormal left atrial blood flow patterns. 4D Flow cardiovascular magnetic resonance (CMR) enables blood flow assessment from the entire three-dimensional atrial volume throughout the cardiac cycle. We sought to investigate left atrial 4D blood flow patterns and hemostasis during left atrial stunning and after left atrial mechanical function was restored.Methods: 4D Flow and morphological CMR data as well as blood samples were collected in fourteen patients at two time-points: 2–3 h (Time-1) and 4 weeks (Time-2) following cardioversion. The volume of blood stasis and duration of blood stasis were calculated. In addition, hemostasis markers were analyzed.Results: From Time-1 to Time-2: Heart rate decreased (61 ± 7 vs. 56 ± 8 bpm, p = 0.01); Maximum change in left atrial volume increased (8 ± 4 vs. 22 ± 15%, p = 0.009); The duration of stasis (68 ± 11 vs. 57 ± 8%, p = 0.002) and the volume of stasis (14 ± 9 vs. 9 ± 7%, p = 0.04) decreased; Thrombin-antithrombin complex (TAT) decreased (5.2 ± 3.3 vs. 3.3 ± 2.2 μg/L, p = 0.008). A significant correlation was found between TAT and the volume of stasis (r2 = 0.69, p < 0.001) at Time-1 and between TAT and the duration of stasis (r2 = 0.34, p = 0.04) at Time-2.Conclusion: In this longitudinal study, left atrial multidimensional blood flow was altered and blood stasis was elevated during left atrial stunning compared to the restored left atrial mechanical function. The coagulability of blood was also elevated during atrial stunning. The association between blood stasis and hypercoagulability proposes that assessment of left atrial 4D flow can add to the pathophysiological understanding of thrombus formation during atrial fibrillation related atrial stunning.

Three‐Dimensional Power Doppler Evaluation of Cerebral Vascular Blood Flow: A Novel Tool in the Assessment of Fetal Growth Restriction

To determine whether fetuses with fetal growth restriction (FGR) are more likely to have abnormal cerebral vascular flow patterns compared to fetuses who are appropriate for gestational age (AGA) when quantified by using 3-dimensional (3D) power Doppler ultrasound. We conducted a prospective cohort study of singleton gestations presenting for growth ultrasound examination between 24 and 36 weeks' gestation. Patients with FGR (estimated fetal weight < 10th percentile) were enrolled and matched 1:1 for gestational age (±7 days) with AGA fetuses. A standardized 3D power Doppler image of the middle cerebral artery territory was obtained from each patient. The vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) were calculated by the Virtual Organ computer-aided analysis technique (GE Healthcare, Milwaukee, WI). These indices were compared between FGR and AGA fetuses and correlated with 2-dimensional Doppler parameters. Neonatal outcomes were also compared with respect to the 3D parameters. Of 306 patients, there were 151 cases of FGR. There was no difference in the VI (6.0 versus 5.7; P = .65) or VFI (2.0 versus 1.8; P = .31) between the groups; however, the FI was significantly higher in FGR fetuses compared to AGA controls (33.9 versus 32.3; P = .009). There was a weak, but significant, negative correlation between the FI and both the middle cerebral artery pulsatility index (r = -0.34; P < .001) and cerebroplacental ratio (r = -0.29; P < .001). Within the FGR group, there was no difference in any of the 3D vascular indices with regard to neonatal outcomes. Three-dimensional power Doppler measurement of cerebral blood flow, but not the vascularization pattern, is significantly altered in FGR. This measurement may play a future role in distinguishing pathologic FGR from constitutionally small growth.