Vascular Thrombosis in Severe COVID-19 Requiring Extracorporeal Membrane Oxygenation: A Multicenter Study

OBJECTIVES

Coronavirus disease 2019 has been reported to be a prothrombotic condition; however, multicenter data comparing this with other viral pneumonias in those requiring extracorporeal membrane oxygenation are lacking. We conducted a multicenter study using whole-body CT to examine the prevalence, severity, and nature of vascular complications in coronavirus disease 2019 in comparison with patients with other viral pneumonias.

DESIGN

We analyzed whole-body CT scans for the presence of vascular thrombosis (defined as pulmonary artery thrombus, venous thrombus, systemic arterial thrombus, or end-organ infarct). The severity, distribution, and morphology of pulmonary artery thrombus were characterized. Competing risk cumulative incidence analysis was used to compare survival with discharge.

SETTING

Three centers of the English national extracorporeal membrane oxygenation service.

PATIENTS

Consecutive patients admitted with either coronavirus disease 2019 or noncoronavirus disease 2019 viral pneumonia admitted from January 2019.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One-hundred thirty-six patients (45.2 ± 10.6 yr old, 39/146 [27%] female) requiring extracorporeal membrane oxygenation support underwent whole-body CT scans at admission. Of these, 86 had coronavirus disease 2019 pneumonia, and 50 had noncoronavirus disease 2019 viral pneumonia. Vascular thrombosis was seen more often in patients with coronavirus disease 2019 (odds ratio, 12.9 [95% CI 4.5-36.8]). In those with coronavirus disease 2019, 57 (73%) demonstrated pulmonary artery thrombus or pulmonary perfusion defects. Eighty-two percent of thrombus exhibited emboli-like morphology. The location of pulmonary artery thrombus and parenchymal perfusion defects was only concordant in 30% of cases. The risk of mortality was higher in those with coronavirus disease 2019 compared with noncoronavirus disease 2019 pneumonia (χ2 = 3.94; p = 0.047). Mortality was no different in coronavirus disease 2019 patients with or without vascular thrombosis (χ2 = 0.44; p = 0.51).

CONCLUSIONS

In patients who received extracorporeal membrane oxygenation, coronavirus disease 2019 is associated with a higher prevalence of vascular thrombosis compared with noncoronavirus disease viral pneumonias. The pattern of pulmonary vascular changes suggests concurrent embolic disease and small vessel disease. Despite this, vascular thrombosis was not linked to poorer short-term prognosis in those with coronavirus disease 2019.

Paravalvular leakage in transcatheter mitral valve replacement: Bringing simulation theory one step closer to reality

Transcatheter mitral valve replacement (TMVR) has emerged as a promising technique for the treatment of these patients with severe mitral valve disease and high or prohibitive surgical risk. Early experience with TMVR has shown a high rate of technical success and promising reductions in the severity of mitral regurgitation sustained out to 1 year post procedure. Despite this, procedural complications remain high, with the most common and significant of these being valve embolization, left ventricualr outflow tract (LVOT) obstruction and paravalvular leakage (PVL). It is this currently unanswered question that Morris et al. start to address in this issue of the Journal. They use the same annular segmentation and valve simulation as already proposed to predict LVOT obstruction, but use it to focus instead on examining the residual gap left between the base of the simulated transcatheter valve and the mitral leaflets or surgical prosthesis.

Enzyme Binding Selectivity Prediction: α-Thrombin vs Trypsin Inhibition

In the present work we explore the possibility of an in-depth computational analysis of available experimental X-ray structures in the specific case of a series of alpha-thrombin and trypsin complexes with their respective inhibitors for the development of a novel scoring function based on molecular electrostatic potential computed at the contact surface in the enzyme-inhibitor molecular complex. We subsequently employ the chemometrical approach to determine which are the interactions in the large volume of data that determine the resulting experimental binding constant between ligand and receptor. The results of the model evaluated with molecules in the independent validation set show that a reasonable average error of 1.30 log units of the difference between experimental and calculated binding constants was achieved in the system thrombin-trypsin, which is comparable with those of methods from the literature. Furthermore, by a careful preparation of the Kohonen top layer in the artificial neural network approach that is normally perceived as a "black box device", we have been able to follow the implications of the structure of the inhibitor-enzyme complex for the inhibitor's binding constant. The method appears to be suitable for evaluation of selectivity in structurally similar enzymatic systems, which is currently an important problem in drug design.

Inhibitors of cysteine proteinases from potato

Potato tubers contain considerable amounts of inhibitors of cysteine proteinases. The majority of inhibitory activity is due to low-molecular mass inhibitors differing in isoelectric points. Three of them were obtained in homogenous form, namely PCPIs (potato cysteine proteinase inhibitors) 6.6 (Mr 25,000), 8.3 and 9.4 (both Mr 22,000). They all appeared to be single-chain proteins. The amino-acid composition and the N-terminal amino-acid sequences show that at least two of them are homologous proteins, but so far no homology to the inhibitors of the cystatin super-family or to any other sequenced potato proteins is apparent. PCPIs inhibit papain and human cathepsins B, H, and L. The inhibitors interact with enzymes in apparently equimolar fashion, the interaction is of the tight binding type with Ki values ranging from 10(-6)M to 10(-11)M.

Amino acid sequences of the human kidney cathepsins H and L

The complete amino acid sequences of human kidney cathepsin H (EC 3.4.22.16) and human kidney cathepsin L (EC 3.4.22.15) were determined. Cathepsin H contains 230 residues and has an Mr of 25116. The sequence was obtained by sequencing the light, heavy and mini chain and the peptides produced by cyanogen bromide cleavage of the single-chain form of the enzyme. The glycosylated mini chain is a proteolytic fragment of the propeptide of cathepsin H. Human cathepsin L has 217 amino acid residues and an Mr of 23720. Its amino acid sequence was deduced from N-terminal sequences of the heavy and light chains and from the sequences of cyanogen bromide fragments of the heavy chain. The fragments were aligned by comparison with known sequences of cathepsins H and L from other species. Cathepsins H and L exhibit a high degree of sequence homology to cathepsin B (EC 3.4.22.1) and other cysteine proteinases of the papain superfamily.

Human plasma kininogens are identical with alpha-cysteine proteinase inhibitors. Evidence from immunological, enzymological and sequence data

Human high- and low-Mr kininogens were shown to be potent inhibitors of cysteine proteinases such as cathepsin L and papain (Ki = 17-48 pM). A strong immunological cross-reaction between the kininogens and low-Mr alpha-cysteine proteinase inhibitor from human plasma was found. Comparison of partial amino acid sequences from high- and low-Mr kininogen and low-Mr alpha-cysteine proteinase inhibitor demonstrated sequence identity for all segments analyzed. These findings suggest that the kininogens and the alpha-cysteine proteinase inhibitors from human plasma are identical proteins.