Fully Automated Artificial Intelligence Assessment of Aortic Stenosis by Echocardiography.

BACKGROUND: Aortic stenosis (AS) is a common form of valvular heart disease, present in over 12% of the population age 75 years and above. Transthoracic echocardiography (TTE) is the first line of imaging in the adjudication of AS severity but is time-consuming and requires expert sonographic and interpretation capabilities to yield accurate results. Artificial intelligence (AI) technology has emerged as a useful tool to address these limitations but has not yet been applied in a fully hands-off manner to evaluate AS. Here, we correlate artificial neural network measurements of key hemodynamic AS parameters to experienced human reader assessment. METHODS: Two-dimensional and Doppler echocardiographic images from patients with normal aortic valves and all degrees of AS were analyzed by an artificial neural network (Us2.ai) with no human input to measure key variables in AS assessment. Trained echocardiographers blinded to AI data performed manual measurements of these variables, and correlation analyses were performed. RESULTS: Our cohort included 256 patients with an average age of 67.6 ± 9.5 years. Across all AS severities, AI closely matched human measurement of aortic valve peak velocity (r = 0.97, P < .001), mean pressure gradient (r = 0.94, P < .001), aortic valve area by continuity equation (r = 0.88, P < .001), stroke volume index (r = 0.79, P < .001), left ventricular outflow tract velocity-time integral (r = 0.89, P < .001), aortic valve velocity-time integral (r = 0.96, P < .001), and left ventricular outflow tract diameter (r = 0.76, P < .001). CONCLUSIONS: Artificial neural networks have the capacity to closely mimic human measurement of all relevant parameters in the adjudication of AS severity. Application of this AI technology may minimize interscan variability, improve interpretation and diagnosis of AS, and allow for precise and reproducible identification and management of patients with AS.

Dialysis, COVID-19, Poverty, and Race in Greater Chicago: An Ecological Analysis.

RATIONALE & OBJECTIVE: Persons with end-stage kidney disease receiving in-center maintenance hemodialysis may be at high risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure and severe outcomes with coronavirus disease 2019 (COVID-19). The objective of this study was to examine the correlation of SARS-CoV-2 positivity rate per capita and COVID-19-associated deaths with number of dialysis stations and demographics of residents within zip codes in Cook County, IL. STUDY DESIGN: Ecological analysis. SETTING & PARTICIPANTS: Data for SARS-CoV-2 test results and COVID-19-associated deaths during January 21 to June 15, 2020, among the 5,232,412 residents living within the 163 zip codes in Cook County, IL, were merged with demographic and income data from the US Census Bureau. The total number of positive test results in this population was 84,353 and total number of deaths was 4,007. ASSESSMENTS: Number of dialysis stations and stations per capita within a zip code were calculated. SARS-CoV-2-positive test results per capita were calculated as number of positive test results divided by the zip code population. COVID-19-associated deaths per capita were calculated as COVID-19 deaths among residents for a given zip code divided by the zip code population. ANALYTIC APPROACH: Spearman rank correlation coefficients were calculated to examine the correlation of SARS-CoV-2-positive tests per capita and COVID-19-associated deaths per capita with dialysis stations, demographics, and household poverty. To account for multiple testing, statistical significance was considered as P < 0.005. RESULTS: Among the 163 Cook County zip codes, there were 2,501 dialysis stations. Positive test results per capita were significantly associated with number of dialysis stations (r = 0.25; 95% CI, 0.19 to 0.29; P < 0.005) but not with dialysis stations per capita (r = 0.02; 95% CI, -0.03 to 0.08; P = 0.7). Positive test results per capita also correlated significantly with number of households living in poverty (r = 0.57; 95% CI, 0.53-0.6; P < 0.005) and percentage of residents reporting Black race (r = 0.28; 95% CI, 0.23-0.33; P < 0.005) and Hispanic ethnicity (r = 0.68; 95% CI, 0.65-0.7; P < 0.001;). COVID-19-associated deaths per capita correlated significantly with the percentage of residents reporting Black race (r = 0.24; 95% CI, 0.19-0.29; P < 0.005) and with percentage of households living in poverty (r = 0.34; 95% CI, 0.29-0.38; P < 0.005). The association between the number of COVID-19-associated deaths per capita and total number of dialysis stations (r = 0.20; 95% CI, 0.14-0.25; P = 0.01) did not achieve a priori significance, whereas the association with dialysis stations per capita (r = 0.12; 95% CI, 0.07-0.17; P = 0.01) was not significant. LIMITATIONS: Analysis is at the zip code level and not at the person level. CONCLUSIONS: The number of dialysis stations within a zip code correlates with the SARS-CoV-2 positivity rate per capita in Cook County, IL, and this correlation may be driven by population density and the demographics of the residents. These findings highlight the high risk of SARS-CoV-2 exposure for patients with end-stage kidney disease living in poor urban areas.

Novel approach for quantification of endoplasmic reticulum Ca2+ transport.

The type 2a sarco-/endoplasmic reticulum Ca2+-ATPase (SERCA2a) plays a key role in Ca2+ regulation in the heart. However, available techniques to study SERCA function are either cell destructive or lack sensitivity. The goal of this study was to develop an approach to selectively measure SERCA2a function in the cellular environment. The genetically encoded Ca2+ sensor R-CEPIA1er was used to measure the concentration of Ca2+ in the lumen of the endoplasmic reticulum (ER) ([Ca2+]ER) in HEK293 cells expressing human SERCA2a. Coexpression of the ER Ca2+ release channel ryanodine receptor (RyR2) created a Ca2+ release/reuptake system that mimicked aspects of cardiac myocyte Ca2+ handling. SERCA2a function was quantified from the rate of [Ca2+]ER refilling after ER Ca2+ depletion; then, ER Ca2+ leak was measured after SERCA inhibition. ER Ca2+ uptake and leak were analyzed as a function of [Ca2+]ER to determine maximum ER Ca2+ uptake rate and maximum ER Ca2+ load. The sensitivity of this assay was validated by analyzing effects of SERCA inhibitors, [ATP]/[ADP], oxidative stress, phospholamban, and a loss-of-function SERCA2a mutation. In addition, the feasibility of using R-CEPIA1er to study SERCA2a in a native system was evaluated by using in vivo gene delivery to express R-CEPIA1er in mouse hearts. After ventricular myocyte isolation, the same methodology used in HEK293 cells was applied to study endogenous SERCA2a. In conclusion, this new approach can be used as a sensitive screening tool to study the effect of different drugs, posttranslational modifications, and mutations on SERCA function. NEW & NOTEWORTHY The aim of this study was to develop a sensitive approach to selectively measure sarco-/endoplasmic reticulum Ca2+-ATPase (SERCA) function in the cellular environment. The newly developed Ca2+ sensor R-CEPIA1er was used to successfully analyze Ca2+ uptake mediated by recombinant and native cardiac SERCA. These results demonstrate that this new approach can be used as a powerful tool to study new mechanisms of Ca2+ pump regulation.

Redistribution of SERCA calcium pump conformers during intracellular calcium signaling.

The conformational changes of a calcium transport ATPase were investigated with molecular dynamics (MD) simulations as well as fluorescence resonance energy transfer (FRET) measurements to determine the significance of a discrete structural element for regulation of the conformational dynamics of the transport cycle. Previous MD simulations indicated that a loop in the cytosolic domain of the SERCA calcium transporter facilitates an open-to-closed structural transition. To investigate the significance of this structural element, we performed additional MD simulations and new biophysical measurements of SERCA structure and function. Rationally designed in silico mutations of three acidic residues of the loop decreased SERCA domain-domain contacts and increased domain-domain separation distances. Principal component analysis of MD simulations suggested decreased sampling of compact conformations upon N-loop mutagenesis. Deficits in headpiece structural dynamics were also detected by measuring intramolecular FRET of a Cer-YFP-SERCA construct (2-color SERCA). Compared with WT, the mutated 2-color SERCA shows a partial FRET response to calcium, whereas retaining full responsiveness to the inhibitor thapsigargin. Functional measurements showed that the mutated transporter still hydrolyzes ATP and transports calcium, but that maximal enzyme activity is reduced while maintaining similar calcium affinity. In live cells, calcium elevations resulted in concomitant FRET changes as the population of WT 2-color SERCA molecules redistributed among intermediates of the transport cycle. Our results provide novel insights on how the population of SERCA pumps responds to dynamic changes in intracellular calcium.

Effects of Increased Arterial Stiffness on Atherosclerotic Plaque Amounts.

Increased arterial stiffness is associated with atherosclerosis in humans, but there have been limited animal studies investigating the relationship between these factors. We bred elastin wildtype (Eln+/+) and heterozygous (Eln+/-) mice to apolipoprotein E wildtype (Apoe+/+) and knockout (Apoe-/-) mice and fed them normal diet (ND) or Western diet (WD) for 12 weeks. Eln+/- mice have increased arterial stiffness. Apoe-/- mice develop atherosclerosis on ND that is accelerated by WD. It has been reported that Apoe-/- mice have increased arterial stiffness and that the increased stiffness may play a role in atherosclerotic plaque progression. We found that Eln+/+Apoe-/- arterial stiffness is similar to Eln+/+Apoe+/+ mice at physiologic pressures, suggesting that changes in stiffness do not play a role in atherosclerotic plaque progression in Apoe-/- mice. We found that Eln+/-Apoe-/- mice have increased structural arterial stiffness compared to Eln+/+Apoe-/- mice, but they only have increased amounts of ascending aortic plaque on ND, not WD. The results suggest a change in atherosclerosis progression but not end stage disease in Eln+/-Apoe-/- mice due to increased arterial stiffness. Possible contributing factors include increased blood pressure and changes in circulating levels of interleukin-6 (IL6) and transforming growth factor beta 1 (TGF-ß1) that are also associated with Eln+/- genotype.

Hypertension and decreased aortic compliance due to reduced elastin amounts do not increase atherosclerotic plaque accumulation in Ldlr-/- mice.

BACKGROUND AND AIMS: High blood pressure and reduced aortic compliance are associated with increased atherosclerotic plaque accumulation in humans. Animal studies support these associations, but additional factors, such as fragmented elastic fibers, are present in most previous animal studies. Elastin heterozygous (Eln+/-) mice have high blood pressure and reduced aortic compliance, with no evidence of elastic fiber fragmentation and represent an appropriate model to directly investigate the effects of these factors on atherosclerosis. METHODS AND RESULTS: Eln+/- and Eln+/+ mice were crossed with low density lipoprotein receptor knockout (Ldlr-/-) and wild-type (Ldlr+/+) mice and fed normal or Western diet (WD) for 16 weeks. We hypothesized that on WD, Eln+/-Ldlr-/- mice with high blood pressure and reduced aortic compliance would have increased atherosclerotic plaque accumulation compared to Eln+/+Ldlr-/- mice. We measured serum cholesterol and cytokine levels, blood pressure, aortic compliance, and plaque accumulation. Contrary to our hypothesis, we found that on WD, Eln+/-Ldlr-/- mice do not have increased plaque accumulation compared to Eln+/+Ldlr-/- mice. At the aortic root, there are no significant differences in plaque area between Eln+/-Ldlr-/- and Eln+/+Ldlr-/- mice on WD (p = 0.89), while in the ascending aorta, Eln+/-Ldlr-/- mice on WD have 29% less normalized plaque area than Eln+/+Ldlr-/- mice on WD (p = 0.009). CONCLUSION: Using an atherogenic mouse model, we conclude that increased blood pressure and reduced aortic compliance are not direct causes of increased aortic plaque accumulation. We propose that additional insults, such as fragmentation of elastic fibers, are necessary to alter plaque accumulation.

Mechanical factors direct mouse aortic remodelling during early maturation.

Numerous diseases have been linked to genetic mutations that lead to reduced amounts or disorganization of arterial elastic fibres. Previous work has shown that mice with reduced amounts of elastin (Eln+/-) are able to live a normal lifespan through cardiovascular adaptations, including changes in haemodynamic stresses, arterial geometry and arterial wall mechanics. It is not known if the timeline and presence of these adaptations are consistent in other mouse models of elastic fibre disease, such as those caused by the absence of fibulin-5 expression (Fbln5-/-). Adult Fbln5-/- mice have disorganized elastic fibres, decreased arterial compliance and high blood pressure. We examined mechanical behaviour of the aorta in Fbln5-/- mice through early maturation when the elastic fibres are being assembled. We found that the physiologic circumferential stretch, stress and modulus of Fbln5-/- aorta are maintained near wild-type levels. Constitutive modelling suggests that elastin contributions to the total stress are decreased, whereas collagen contributions are increased. Understanding how collagen fibre structure and mechanics compensate for defective elastic fibres to meet the mechanical requirements of the maturing aorta may help to better understand arterial remodelling in human elastinopathies.