Recently, there has been considerable interest in new tiered network cellular architectures, which would likely use many more cell sites than found today. Two major challenges will be i) providing ...backhaul to all of these cells and ii) finding efficient techniques to leverage higher frequency bands for mobile access and backhaul. This paper proposes the use of outdoor millimeter wave communications for backhaul networking between cells and mobile access within a cell. To overcome the outdoor impairments found in millimeter wave propagation, this paper studies beamforming using large arrays. However, such systems will require narrow beams, increasing sensitivity to movement caused by pole sway and other environmental concerns. To overcome this, we propose an efficient beam alignment technique using adaptive subspace sampling and hierarchical beam codebooks. A wind sway analysis is presented to establish a notion of beam coherence time. This highlights a previously unexplored tradeoff between array size and wind-induced movement. Generally, it is not possible to use larger arrays without risking a corresponding performance loss from wind-induced beam misalignment. The performance of the proposed alignment technique is analyzed and compared with other search and alignment methods. The results show significant performance improvement with reduced search time.
Three‐dimensional echocardiography (3DE) has emerged in recent decades from a conceptual, research tool to an important, useful imaging technique that can informatively impact daily clinical ...practice. However, its adoption into the modern‐day echo laboratory requires the acknowledgment of its value, coupled with proper leadership, education, and resources to implement and integrate its use with conventional echo techniques. 3DE integration involves important updates regarding equipment and patient selection, assimilation of 3D protocols into current clinical routine, laboratory workflow adaptation, storage, and reporting. This review will provide a practical blueprint and key points of how to integrate 3DE into today's echo laboratory, necessary resources to implement 3D workflow, logistical challenges that remain, and future directions to further improve assimilation of this relevant echo technique into the laboratory.
Pulmonary hypertension (PH) is defined as resting mean pulmonary arterial pressure (mPAP) ≥25 millimeters of mercury (mmHg) via right heart (RH) catheterization (RHC), where increased afterload in ...the pulmonary arterial vasculature leads to alterations in RH structure and function. Mortality rates have remained high despite therapy, however non-invasive imaging holds the potential to expedite diagnosis and lead to earlier initiation of treatment, with the hope of improving prognosis. While historically the right ventricle (RV) had been considered a passive chamber with minimal role in the overall function of the heart, in recent years in the evaluation of PH and RH failure the anatomical and functional assessment of the RV has received increased attention regarding its performance and its relationship to other structures in the RH-pulmonary circulation. Today, the RV is the key determinant of patient survival. This review provides an overview and summary of non-invasive imaging methods to assess RV structure, function, flow, and tissue characterization in the setting of imaging's contribution to the diagnostic, severity stratification, prognostic risk, response of treatment management, and disease surveillance implications of PH's impact on RH dysfunction and clinical RH failure.
The prevalence of coronary artery disease (CAD) in patients with peripheral arterial disease (PAD) varies widely in published reports. This is likely due at least in part to significant differences ...in how PAD and CAD were both defined and diagnosed. In this report, the investigators describe 78 patients with PAD who underwent preoperative coronary angiography before elective peripheral revascularization and provide a review of published case series. Among the patients included, the number with concomitant CAD varied from 55% in those with lower-extremity stenoses to as high as 80% in those with carotid artery disease. The number of coronary arteries narrowed by ≥50% was 1 in 28%, 2 in 24%, and 3 in 19%; 28% did not have any angiographic evidence of CAD. The review of published research resulted in the identification of 19 case series in which a total of 3,969 patients underwent preoperative coronary angiography before elective PAD surgery; in the 2,687 who were described according to the location of the PAD, 55% had ≥1 epicardial coronary artery with ≥70% diameter narrowing. The highest prevalence of concomitant CAD was in patients with severe carotid artery disease (64%). In conclusion, despite sharing similar risk factors, the prevalence of obstructive CAD in patients with PAD ranges widely and appears to differ across PAD locations. Thus, the decision to perform coronary angiography should be based on indications independent of the planned PAD surgery.
Cranio-lenticulo-sutural dysplasia (CLSD) is an autosomal recessive syndrome characterized by late-closing fontanels, sutural cataracts, facial dysmorphisms and skeletal defects mapped to chromosome ...14q13-q21 (ref. 1). Here we show, using a positional cloning approach, that an F382L amino acid substitution in SEC23A segregates with this syndrome. SEC23A is an essential component of the COPII-coated vesicles that transport secretory proteins from the endoplasmic reticulum to the Golgi complex. Electron microscopy and immunofluorescence show that there is gross dilatation of the endoplasmic reticulum in fibroblasts from individuals affected with CLSD. These cells also exhibit cytoplasmic mislocalization of SEC31. Cell-free vesicle budding assays show that the F382L substitution results in loss of SEC23A function. A phenotype reminiscent of CLSD is observed in zebrafish embryos injected with sec23a-blocking morpholinos. Our observations suggest that disrupted endoplasmic reticulum export of the secretory proteins required for normal morphogenesis accounts for CLSD.
Accurate assessment of aortic valve (AV) stenosis (AS) on transthoracic echocardiogram is crucial for appropriate clinical management. However, discordance between aortic valve area (AVA) and Doppler ...can complicate the diagnosis of severe AS in low-gradient (LG) AS phenotypes.
We reviewed 220 consecutive patients with suspected severe AS and AVA ≤1.0 cm2 on transthoracic echocardiogram who were evaluated for transcatheter AV replacement (TAVR) within a large health system from 2015 to 2019. We compared AV calcium score and aorto-mitral angle (AMA) on 3-chamber views from ECG-gated cardiovascular CT among patients with high-gradient (HG) AS (N = 19), paradoxical low-flow low-gradient (PLFLG) AS (N = 24) and normal-flow low-gradient (NFLG) AS (N = 14).
All groups had comparable age, comorbidities, and AV calcium scores. Compared to patients with HG AS (mean AMA 120 ± 10°), those with PLFLG AS (104 ± 12°; p < 0.001) and NFLG AS (106 ± 13°; p = 0.008) had narrower mean AMA values on cardiovascular CT.
LG AS patients have significantly narrower AMA than HG AS patients on cardiovascular CT. Due to difficulty obtaining parallel Doppler alignment, narrower AMA may contribute to AVA-Doppler discordance on echocardiogram. These findings emphasize the need for additional information in the setting of LG AS.
Panel A shows AMATTE, AMACCT, and AVCS comparisons between HG and LG AS groups. Boxplots depict median and interquartile range. Panel B shows examples of measured AMATTE and AMACCT among HG AS, Paradoxical LG AS, and Normal Flow LG AS. AMA = Aorto-Mitral Angle. AVCS = Aortic Valve Calcium Score. AS = Aortic Stenosis. HG = High Gradient. LG = Low Gradient. TTE = Transthoracic Echocardiogram. CCT = Cardiovascular Computed Tomography. Display omitted
•Accurate assessment of aortic stenosis (AS) severity is crucial for intervention timing.•Low-gradient aortic stenosis patients have narrower aorto-mitral angle on cardiovascular computed tomography.•Smaller angle may result in discordant Doppler data and AS severity underestimation.•For smaller angles, alternative parameters beyond Doppler echocardiography should be sought.
Most trials comparing percutaneous coronary intervention (PCI) with coronary-artery bypass grafting (CABG) have not made use of second-generation drug-eluting stents.
We conducted a randomized ...noninferiority trial at 27 centers in East Asia. We planned to randomly assign 1776 patients with multivessel coronary artery disease to PCI with everolimus-eluting stents or to CABG. The primary end point was a composite of death, myocardial infarction, or target-vessel revascularization at 2 years after randomization. Event rates during longer-term follow-up were also compared between groups.
After the enrollment of 880 patients (438 patients randomly assigned to the PCI group and 442 randomly assigned to the CABG group), the study was terminated early owing to slow enrollment. At 2 years, the primary end point had occurred in 11.0% of the patients in the PCI group and in 7.9% of those in the CABG group (absolute risk difference, 3.1 percentage points; 95% confidence interval CI, -0.8 to 6.9; P=0.32 for noninferiority). At longer-term follow-up (median, 4.6 years), the primary end point had occurred in 15.3% of the patients in the PCI group and in 10.6% of those in the CABG group (hazard ratio, 1.47; 95% CI, 1.01 to 2.13; P=0.04). No significant differences were seen between the two groups in the occurrence of a composite safety end point of death, myocardial infarction, or stroke. However, the rates of any repeat revascularization and spontaneous myocardial infarction were significantly higher after PCI than after CABG.
Among patients with multivessel coronary artery disease, the rate of major adverse cardiovascular events was higher among those who had undergone PCI with the use of everolimus-eluting stents than among those who had undergone CABG. (Funded by CardioVascular Research Foundation and others; BEST ClinicalTrials.gov number, NCT00997828.).
Prior studies on ascending thoracic aortic aneurysm (ATAA) growth rates have reported approximately 1 mm of growth per year but these studies are based on referral-based study populations which are ...biased towards the highest risk patients who may not represent the true natural history of aortic aneurysm disease. We aimed to characterize the growth rate of ATAAs in a non-referral-based population, using a large institutional database of computed tomography (CT) scans.
We queried the 21,325 CT scans performed at our institution between 2013 and 2016 on patients ages 50-85 years old for radiologic diagnosis of aortic aneurysm or dilatation. 560 patients were identified to have aortic dilatation > 4 cm, of which 207 had follow-up scan intervals > 6 months. This comprised our non-referral-based study population. Linearized annual aneurysm growth rates were calculated by dividing the change in aortic size by the time interval between CT scans.
The median time interval between scans was 2.7 years (interquartile range IQR 1.5-4.2) for the 207 patients included in the study. The median initial aneurysm size was 4.3 cm (IQR 4.1-4.5). 38.2% (n = 79) of patients did not experience aortic dilatation. The median growth rate was 0.13 mm/year (IQR - 0.24 to 0.49). Of patients in the top quartile of growth rates, 26.9% of patients were female whereas 12.9% of patients were female in the bottom three quartiles of growth rates.
While some patients' ATAAs may grow at previously published rates of around 1 mm/year, this is not the predominant pattern in a non-referral-based population and may over-estimate the overall growth rate of ATAAs.
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