Possible role for mast cell-derived cathepsin G in the adverse remodelling of stenotic aortic valves

AIMS

Aortic stenosis (AS) is characterized by extensive remodelling of the valves, including infiltration of inflammatory cells, extracellular matrix degradation, and fibrosis. The molecular mechanisms behind this adverse remodelling have remained obscure. In this article, we study whether cathepsin G, an angiotensin II (Ang II)-forming elastolytic enzyme, contributes to progression of AS.

METHODS AND RESULTS

Stenotic aortic valves (n = 86) and control valves (n = 17) were analysed for cathepsin G, transforming growth factor-beta1 (TGF-beta1), and collagens I and III with RT-PCR and immunohistochemistry. Valvular collagen/elastin ratio was quantified by histochemistry. In stenotic valves, cathepsin G was present in mast cells and showed increased expression (P < 0.001), which correlated positively (P < 0.001) with the expression levels of TGF-beta1 and collagens I and III. TGF-beta1 was also present in mast cell-rich areas and cathepsin G induced losartan-sensitive TGF-beta1 expression in cultured fibroblasts. Collagen/elastin ratio was increased in stenotic valves (P < 0.001) and correlated positively with smoking (P = 0.02). Nicotine in cigarette smoke activated mast cells and induced TGF-beta1 expression in cultured fibroblasts. Fragmented elastin was observed in stenotic valves containing activated cathepsin G-secreting mast cells and in normal valves treated with cathepsin G.

CONCLUSION

In stenotic aortic valves, mast cell-derived cathepsin G may cause adverse valve remodelling and AS progression.

Increased expression of elastolytic cathepsins S, K, and V and their inhibitor cystatin C in stenotic aortic valves

OBJECTIVE

To investigate the possible role of elastolytic cathepsins S, K, and V and their endogenous inhibitor cystatin C in adverse extracellular matrix remodeling of stenotic aortic valves.

METHODS AND RESULTS

Stenotic aortic valves were collected at valve replacement surgery and control valves at cardiac transplantations. The expression of cathepsins S, K, and V and cystatin C was studied by conventional and real-time polymerase chain reaction and by immunohistochemistry. Total cathepsin activity in the aortic valves was quantified by a fluorometric microassay. When compared with control valves, stenotic valves showed increased mRNA expression of cathepsins S, K, and V (P<0.05 for each) and a higher total cathepsin activity (P<0.001). In stenotic valves, cystatin C mRNA was increased (P<0.05), and cystatin C protein was found particularly in areas with infiltrates of inflammatory cells. Both cathepsin S and cystatin C were present in bony areas of the valves, whereas cathepsin V localized to endothelial cells in areas rich of neovascularization. Incubation of thin sections of aortic valves with cathepsins S, K, and V resulted in severe disruption of elastin fibers, and this cathepsin effect could be blocked by adding cystatin C to the incubation system.

CONCLUSIONS

Stenotic aortic valves show increased expression and activity of elastolytic cathepsins S, K, and V. These cathepsins may accelerate the destruction of aortic valvular extracellular matrix, so promoting the progression of aortic stenosis.

MicroRNA-125b and chemokine CCL4 expression are associated with calcific aortic valve disease

Calcific aortic valve disease (CAVD) is a progressive pathological condition with no effective pharmacological therapy. To identify novel molecular pathways as potential targets for pharmacotherapy, we studied microRNA (miRNA) profiles of heavily stenotic aortic valves (AS). One of the most upregulated miRNAs in AS valves compared to control valves was miR-125b (1.4-fold; P < 0.05). To identify CAVD-related changes in gene expression, DNA microarray analysis was performed, including an intermediate fibro(sclero)tic stage of the disease. This revealed changes especially in genes related to inflammation and immune response, including chemokine (C-C motif) ligand 3 (CCL3) and 4 (CCL4). CCL3 mRNA level was increased 3.9-fold (P < 0.05) when AS valves were compared to control valves, and a 2.5-fold increase (P < 0.05) in CCL4 gene expression was observed when fibro(sclero)tic valves were compared to control valves. Both CCL3 and CCL4 localized to macrophages by immunofluorescence. To identify chemokine-miRNA target pairs, data from miRNA target prediction databases were combined with valvular miRNA and mRNA expression profiles. MiR-125b was computationally predicted to target CCL4, as confirmed experimentally in cultured human THP-1 macrophages. Collectively, miR-125b and CCL4 appear to be involved in the progression of CAVD and may offer novel therapeutic and diagnostic strategies related to this disease.

Vascular endothelial growth factor-secreting mast cells and myofibroblasts: a novel self-perpetuating angiogenic pathway in aortic valve stenosis

OBJECTIVE

To examine the proangiogenic potential of myofibroblasts and mast cells, 2 types of cells present in human aortic valves.

METHODS AND RESULTS

Aortic valve stenosis is an active atheroinflammatory disease, characterized by the accumulation of inflammatory cells and the neovascularization of the valves. A total of 85 stenotic valves and 20 control valves were obtained during valve replacement surgery. The results of immunohistochemistry analysis revealed stenotic aortic valves that contained 3 types of neovessels: small microvessels, medium microvessels, and organized arterioles. The distribution density of the neovessels was significantly higher in stenotic valves than in control valves (P<0.001) and correlated positively with valvular calcification gradus (r=0.26, P=0.02) and mast cell density (r=0.38, P<0.001). In the neovascularized areas of stenotic aortic valves, mast cells contained vascular endothelial growth factor and were degranulated, indicating their activation. The stimulation of cultured myofibroblasts derived from aortic valves with a mast cell-preconditioned medium, hypoxic culture conditions, or tobacco smoke all induced vascular endothelial growth factor secretion in the myofibroblasts. Finally, mast cell tryptase was able to degrade the antiangiogenic molecule endostatin in vitro.

CONCLUSIONS

Mast cells and myofibroblasts may accelerate the progression of aortic valve stenosis by altering the balance between angiogenic and antiangiogenic factors in the valves, thus promoting valvular neovascularization.

Cardiac magnetic resonance in giant cell myocarditis: a matched comparison with cardiac sarcoidosis

AIMS

Giant cell myocarditis (GCM) is an inflammatory cardiomyopathy akin to cardiac sarcoidosis (CS). We decided to study the findings of GCM on cardiac magnetic resonance (CMR) imaging and to compare GCM with CS.

METHODS AND RESULTS

CMR studies of 18 GCM patients were analyzed and compared with 18 CS controls matched for age, sex, left ventricular (LV) ejection fraction and presenting cardiac manifestations. The analysts were blinded to clinical data. On admission, the duration of symptoms (median) was 0.2 months in GCM vs. 2.4 months in CS (P = 0.002), cardiac troponin T was elevated (>50 ng/L) in 16/17 patients with GCM and in 2/16 with CS (P < 0.001), their respective median plasma B-type natriuretic propeptides measuring 4488 ng/L and 1223 ng/L (P = 0.011). On CMR imaging, LV diastolic volume was smaller in GCM (177 ± 32 mL vs. 211 ± 58 mL, P = 0.014) without other volumetric or wall thickness measurements differing between the groups. Every GCM patient had multifocal late gadolinium enhancement (LGE) in a distribution indistinguishable from CS both longitudinally, circumferentially, and radially across the LV segments. LGE mass averaged 17.4 ± 6.3% of LV mass in GCM vs 25.0 ± 13.4% in CS (P = 0.037). Involvement of insertion points extending across the septum into the right ventricular wall, the "hook sign" of CS, was present in 53% of GCM and 50% of CS.

CONCLUSION

In GCM, CMR findings are qualitatively indistinguishable from CS despite myocardial inflammation being clinically more acute and injurious. When matched for LV dysfunction and presenting features, LV size and LGE mass are smaller in GCM.

Peak flow measurements in patients with severe aortic stenosis: a prospective comparative study between cardiovascular magnetic resonance 2D and 4D flow and transthoracic echocardiography

BACKGROUND

Aortic valve stenosis (AS) is the most prevalent valvular disease in the developed countries. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) is an emerging imaging technique, which has been suggested to improve the evaluation of AS severity compared to two-dimensional (2D) flow and transthoracic echocardiography (TTE). We investigated the reliability of CMR 2D flow and 4D flow techniques in measuring aortic transvalvular peak systolic flow in patients with severe AS.

METHODS

We prospectively recruited 90 patients referred for aortic valve replacement due to severe AS (73.3 ± 11.3 years, aortic valve area 0.7 ± 0.1 cm2, and 54/36 tricuspid/bicuspid), and 10 non-valvular disease controls. All the patients underwent echocardiography and 2D flow and 4D flow CMR. Peak flow velocity measurements were compared using Wilcoxon signed rank sum test and Bland-Altman analysis.

RESULTS

4D flow underestimated peak flow velocity in the AS group when compared with TTE (bias - 1.1 m/s, limits of agreement ± 1.4 m/s) and 2D flow (bias - 1.2 m/s, limits of agreement ± 1.6 m/s). The differences between values obtained by TTE (median 4.3 m/s, range 2.7-6.1 m/s) and 2D flow (median 4.5 m/s, range 2.9-6.5 m/s) compared to 4D flow (median 3.1 m/s, range 1.7-5.1 m/s) were significant (p < 0.001). The difference between 2D flow and TTE were insignificant (bias 0.07 m/s, limits of agreement ± 1.5 m/s). In non-valvular disease controls, peak flow velocity was measured higher by 4D flow than 2D flow (1.4 m/s, 1.1-1.7 m/s and 1.3 m/s, 1.1-1.5 m/s, respectively; bias 0.2 m/s, limits of agreement ± 0.16 m/s).

CONCLUSIONS

CMR 4D flow significantly underestimates systolic peak flow velocity in patients with severe AS. 2D flow, in turn, estimated the AS velocity accurately, with measured peak flow velocities comparable to TTE.

Inter- and Intra-Observer Variability and the Effect of Experience in Cine-MRI for Adhesion Detection

Cine-MRI for adhesion detection is a promising novel modality that can help the large group of patients developing pain after abdominal surgery. Few studies into its diagnostic accuracy are available, and none address observer variability. This retrospective study explores the inter- and intra-observer variability, diagnostic accuracy, and the effect of experience. A total of 15 observers with a variety of experience reviewed 61 sagittal cine-MRI slices, placing box annotations with a confidence score at locations suspect for adhesions. Five observers reviewed the slices again one year later. Inter- and intra-observer variability are quantified using Fleiss’ (inter) and Cohen’s (intra) κ and percentage agreement. Diagnostic accuracy is quantified with receiver operating characteristic (ROC) analysis based on a consensus standard. Inter-observer Fleiss’ κ values range from 0.04 to 0.34, showing poor to fair agreement. High general and cine-MRI experience led to significantly (p < 0.001) better agreement among observers. The intra-observer results show Cohen’s κ values between 0.37 and 0.53 for all observers, except one with a low κ of −0.11. Group AUC scores lie between 0.66 and 0.72, with individual observers reaching 0.78. This study confirms that cine-MRI can diagnose adhesions, with respect to a radiologist consensus panel and shows that experience improves reading cine-MRI. Observers without specific experience adapt to this modality quickly after a short online tutorial. Observer agreement is fair at best and area under the receiver operating characteristic curve (AUC) scores leave room for improvement. Consistently interpreting this novel modality needs further research, for instance, by developing reporting guidelines or artificial intelligence-based methods.

Cardiac magnetic resonance -detected myocardial injury is not associated with long-term symptoms in patients hospitalized due to COVID-19

BACKGROUND

Long-term symptoms are frequent after coronavirus disease 2019 (COVID-19). We studied the prevalence of post-acute myocardial scar on cardiac magnetic resonance imaging (CMR) in patients hospitalized due to COVID-19 and its association with long-term symptoms.

MATERIALS AND METHODS

In this prospective observational single-center study, 95 formerly hospitalized COVID-19 patients underwent CMR imaging at the median of 9 months after acute COVID-19. In addition, 43 control subjects were imaged. Myocardial scar characteristic of myocardial infarction or myocarditis were noted from late gadolinium enhancement images (LGE). Patient symptoms were screened using a questionnaire. Data are presented as mean ± standard deviation or median (interquartile range).

RESULTS

The presence of any LGE was higher in COVID-19 patients (66% vs. 37%, p<0.01) as was the presence of LGE suggestive of previous myocarditis (29% vs. 9%, p = 0.01). The prevalence of ischemic scar was comparable (8% vs. 2%, p = 0.13). Only two COVID-19 patients (7%) had myocarditis scar combined with left ventricular dysfunction (EF <50%). Myocardial edema was not detected in any participant. The need for intensive care unit (ICU) treatment during initial hospitalization was comparable in patients with and without myocarditis scar (47% vs. 67%, p = 0.44). Dyspnea, chest pain, and arrhythmias were prevalent in COVID-19 patients at follow-up (64%, 31%, and 41%, respectively) but not associated with myocarditis scar on CMR.

CONCLUSIONS

Myocardial scar suggestive of possible previous myocarditis was detected in almost one-third of hospital-treated COVID-19 patients. It was not associated with the need for ICU treatment, greater symptomatic burden, or ventricular dysfunction at 9 months follow-up. Thus, post-acute myocarditis scar on COVID-19 patients seems to be a subclinical imaging finding and does not commonly require further clinical evaluation.

Impact of Atrial Fibrillation on the Symptoms and Echocardiographic Evaluation of Patients With Aortic Stenosis

Atrial fibrillation (AF) is common in patients with aortic stenosis (AS) and complicates the assessment of AS severity. The overlapping of symptoms in these 2 conditions may postpone valve replacement. This study aimed to evaluate the effect of AF on the severity assessment of AS and its impact on symptoms and quality of life (QoL). Patients with severe AS were prospectively recruited. Echocardiography, symptom questionnaires, and RAND-36 QoL assessment were performed preoperatively and 3 months postoperatively. The aortic valve calcium score (AVC) was measured using computed tomography. Of the 279 patients, 74 (26.5%) had AF. Patients with AF had lower mean gradients and 45.9% had a low-gradient phenotype, with a mean gradient <40 mm Hg, compared with 22.4% of those without AF (p <0.001). The AVC measurements revealed severe valve calcification equally in patients with or without AF (85.7% vs 87.7%, p = 0.78). Patients with AF were more symptomatic at baseline, with 50.0% versus 27.3% in New York Heart Association class III or higher (p <0.001), and after intervention. Patients with AF had more residual dyspnea (27.3% vs 12.0%, p = 0.007) and exercise intolerance (36.4% vs 17.0%, p = 0.002). The QoL improved significantly in both groups but was worse at baseline in patients with AF and remained impaired after intervention. In conclusion, low-gradient AS phenotype is overrepresented in patients with AF, but they have equally severe stenosis determined using AVC, despite the lower gradients. Patients with AF have more symptoms and worse QoL, but they improve significantly after intervention. In patients with AF, multimodality imaging is important in the assessment of AS severity.

Magnetic Resonance Imaging in the Assessment of the Risk of Sudden Death in Cardiac Sarcoidosis: What Is Extensive or Significant Late Gadolinium Enhancement?

BACKGROUND

Cardiac sarcoidosis involves a significant but difficult-to-define risk of sudden cardiac death (SCD). Current guidelines recommend consideration of an implantable cardioverter defibrillator for patients with extensive or significant myocardial late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging. However, extensive/significant LGE is not defined.

METHODS

A nationwide cardiac sarcoidosis registry was screened for patients entered before 2020 with cardiac magnetic resonance imaging done before or <3 months after diagnosis. Available studies were re-analyzed for LGE mass as a percentage of left ventricular (LV) mass and the number of LGE-positive LV segments in a 17-segment model. The occurrence of fatal or aborted SCD and ventricular tachycardia (VT) prompting therapy was recorded until the end of 2020 and subjected to cumulative incidence analyses, including competing events (LV assist device implantations, heart transplantations, and fatalities other than SCD). The predictors of SCD/VT were assessed using Fine and Gray modeling and time-dependent receiver operating characteristic analysis.

RESULTS

Altogether, 305 patients (66% women, median age 51) with clinically manifest, definite (45%) or probable cardiac sarcoidosis (55%) were analyzed. On follow-up (median, 4.0 years), 21 SCDs, 60 VTs, and 14 competing events were noted. Both LGE mass and the number of LGE segments predicted the composite of SCD/VT (P<0.001), with receiver operating characteristic analyses identifying LGE mass ≥9.9% and ≥6 LGE segments as discriminative thresholds. At presentation, 70 patients were free of class I and class IIa implantable cardioverter defibrillator indications unrelated to LGE. Their 5-year rate of SCD/VT was 6.3% (0.0-14.8%) with LGE mass <9.9% versus 21.5% (6.5-36.6%) with higher LGE mass, and 6.9% (0.0-16.3%) with <6 LGE segments versus 20.5% (5.9-35.2%) with ≥6 segments.

CONCLUSIONS

In cardiac sarcoidosis, myocardial LGE making up ≥9.9% of LV mass or affecting ≥6 LV segments may suggest prognostically significant LV involvement and a high risk of SCD. However, prospective validation of the thresholds is needed.

Testing process for artificial intelligence applications in radiology practice

Artificial intelligence (AI) applications are becoming increasingly common in radiology. However, ensuring reliable operation and expected clinical benefits remains a challenge. A systematic testing process aims to facilitate clinical deployment by confirming software applicability to local patient populations, practises, adherence to regulatory and safety requirements, and compatibility with existing systems. In this work, we present our testing process developed based on practical experience. First, a survey and pre-evaluation is conducted, where information requests are sent for potential products, and the specifications are evaluated against predetermined requirements. In the second phase, data collection, testing, and analysis are conducted. In the retrospective stage, the application undergoes testing with a pre selected dataset and is evaluated against specified key performance indicators (KPIs). In the prospective stage, the application is integrated into the clinical workflow and evaluated with additional process-specific KPIs. In the final phase, the results are evaluated in terms of safety, effectiveness, productivity, and integration. The final report summarises the results and includes a procurement/deployment or rejection recommendation. The process allows termination at any phase if the application fails to meet essential criteria. In addition, we present practical remarks from our experiences in AI testing and provide forms to guide and document the testing process. The established AI testing process facilitates a systematic evaluation and documentation of new technologies ensuring that each application undergoes equal and sufficient validation. Testing with local data is crucial for identifying biases and pitfalls of AI algorithms to improve the quality and safety, ultimately benefiting patient care.

Safe Deferral of Coronary Computed Tomography Angiography for Patients With a Low Pretest Probability of Coronary Artery Disease in 2019 European Society of Cardiology Guidelines

BACKGROUND

Coronary computed tomography angiography is increasingly used as the first-line test for suspected coronary artery disease. Its overuse in a low pretest probability (PTP) population may lead to low diagnostic yield without change in patient management. We evaluated the clinical consequences of the updated 2019 European Society of Cardiology (ESC) chronic coronary syndromes guidelines' PTP estimation and whether imaging could be safely deferred in patients with a low PTP.

METHODS AND RESULTS

This retrospective cohort included all 1753 consecutive patients who underwent coronary computed tomography angiography for suspected coronary artery disease at Helsinki University Hospital between 2009 and 2017. PTP was calculated according to the 2013 and 2019 ESC guidelines. The overall mortality, cardiac deaths, myocardial infarctions, and hospitalizations for unstable angina were acquired from national registry data for 1 to 10 years of follow-up (median, 4 years). Updated 2019 ESC guidelines classified 72% of the patients as having low PTP, whose imaging could have been deferred. The revascularization rate (4.7%) and annual cardiac mortality (0.4%) were low in the 857 patients reclassified from the recommendation to test, according to the 2013 ESC guideline, to deferral of coronary computed tomography angiography, according to the new 2019 guideline.

CONCLUSIONS

The updated 2019 ESC guideline PTP score aids clinicians in safely preventing the overuse of cardiac imaging in patients deemed at low PTP of coronary artery disease. Diagnostic yield, revascularization rate, and cardiac mortality are low in patients with low pretest risk.