The appreciation of prosthetic heart valves

According to its definition, prosthesis-patient mismatch is present when the cardiac output of the patient is too large for the opening of a prosthetic valve. This causes symptoms similar to native aortic stenosis, which can lead to heart failure and mortality. To classify patients with PPM, a cut-off value of indexed effective orifice area is used in clinical practice.This thesis evaluates the underlying assumptions of using indexed effective orifice area as a parameter of valve performance. As these assumptions are inaccurate, the current definition of prosthesis-patient mismatch is unsuitable to diagnose patients with too small prosthetic valves after aortic valve replacement.LUMC / Geneeskund

Concomitant aortic root enlargement is perhaps safe, but is it also effective?

Thoracic Surger

A bigger picture for valve charts

Thoracic Surger

The clinical implications of body surface area as a poor proxy for cardiac output

Background Prosthesis-patient mismatch (PPM), routinely used to characterize the degree of hemodynamic obstruction caused by a prosthetic heart valve, is associated with adverse patient outcomes after aortic valve replacement (AVR). In the common definition of PPM, the opening area of the valve is related to the patients' cardiac output, by indexing effective orifice area (EOA) with body surface area (BSA). The aim of this study is to assess the implications of using BSA as a proxy for cardiac output. Methods 744 patients with normal LV function underwent echocardiographic assessment after surgical AVR. To validate the use of BSA as a proxy for cardiac output, the relation between these variables was analyzed. The effects of BSA on the classification of PPM (EOAi = 20 mmHg and/or Doppler velocity index < 0.35) were estimated. Results There was a weak correlation between BSA and cardiac output (r: 0.29, 95% CI: 0.22;0.35), and cardiac output was not proportional to BSA (Cardiac output = 1.5 x BSA +1.9). As a result, the increased risk of patients with a large BSA to be labelled with PPM (OR: 5.2, 95% CI: 2.5,11 per m(2) BSA), was not reflected by a significantly higher risk of hemodynamic obstruction (OR: 1.5, 95% CI: 0.5,4.9 per m(2) BSA). Conclusions The current definition of PPM results in a systematic overestimation of hemodynamic obstruction in patients with a larger BSA, and we recommend cautious use in this subgroup.Thoracic Surger

The fallacy of indexed effective orifice area charts to predict prosthesis-patient mismatch alter prosthesis implantation

Aims Indexed effective orifice area (EOAi) charts are used to determine the likelihood of prosthesis-patient mismatch (PPM) after aortic valve replacement (AVR). The aim of this study is to validate whether these EOAi charts, based on echocardiographic normal reference values, can accurately predict PPM.Methods and results In the PERIcardial SurGical AOrtic Valve ReplacemeNt (PERIGON) Pivotal Trial, 986 patients with aortic valve stenosis/regurgitation underwent AVR with an Avalus valve. Patients were randomly split (50:50) into training and test sets. The mean measured EOAs for each valve size from the training set were used to create an Avalus EOAi chart. This chart was subsequently used to predict PPM in the test set and measures of diagnostic accuracy (sensitivity, specificity, and negative and positive predictive value) were assessed. PPM was defined by an EOAi <= 0.85 cm(2)/m(2) and severe PPM was defined as EOAi <= 0.65 cm(2)/m(2). The reference values obtained from the training set ranged from 1.27 cm(2) for size 19 mm up to 1.81 cm(2) for size 27 mm. The test set had an incidence of 66% of PPM and 24% of severe PPM. The EOAi chart inaccurately predicted PPM in 30% of patients and severe PPM in 22% of patients. For the prediction of PPM, the sensitivity was 87% and the specificity 37%. For the prediction of severe PPM, the sensitivity was 13% and the specificity 98%.Conclusion use of echocardiographic normal reference values for EOAi charts to predict PPM is unreliable due to the large proportion of misclassifications.Thoracic Surger

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees

Is Older Age Truly a Predictor of SVD?

Thoracic Surger

The Ratio Fallacy of Prosthesis-Patient Mismatch

Thoracic Surger

An in vitro comparison of internally versus externally mounted leaflets in surgical aortic bioprostheses

OBJECTIVES: To improve haemodynamic performance, design modifications of prosthetic valves have been proposed with each new generation of valves. These different designs also impact the amount of mechanical wear, because mechanical stresses are distributed differently. Because long-term evidence for new prosthetic valves is lacking, this in vitro study compared hydrodynamic performance and durability among 3 currently available bioprosthetic valves with internally (IMLV) or externally mounted leaflets (EMLV).METHODS: Prostheses of the internally mounted Medtronic Avalus and Carpentier-Edwards Perimount Magna Ease valves were compared to prostheses of the externally mounted Abbott Trifecta valve. For each labelled size (e.g. 19, 21 and 23) of the 3 types, 3 valves underwent accelerated wear testing for up to 600 million cycles, corresponding to similar to 15 years of simulated wear. The valves underwent hydrodynamic testing and visual inspection.RESULTS: EMLV had the largest effective orifice area and lowest pressure gradient for each labelled size at baseline and 600 million cycles; the effective orifice area and the pressure gradient were equivalent for the 2 types of IMLV. Five of 9 EMLVs had at least 1 hole or tear in the leaflet tissue around the stent posts, which resulted in severe regurgitation at 500 million cycles in 2 cases. All IMLVs were intact at 600 million cycles with minimal tissue wear.CONCLUSIONS: EMLV showed superior hydrodynamic performance but inferior mechanical durability compared to IMLV after 600 million cycles of testing. The primary failures were because of significant mechanical abrasion in the commissural region, which may warrant close monitoring of EMLV during long-term follow-up.Thoracic Surger

Minimally Invasive Aortic Valve Replacement in Contemporary Practice: Clinical and Hemodynamic Performance from a Prospective Multicenter Trial

Background The advent of transcatheter aortic valve replacement (AVR) has led to an increased emphasis on reducing the invasiveness of surgical procedures. The aim of this study was to evaluate clinical outcomes and hemodynamic performance achieved with minimally invasive aortic valve replacement (MI-AVR) as compared with conventional AVR. Methods Patients who underwent surgical AVR with the Avalus bioprosthesis, as part of a prospective multicenter non-randomized trial, were included in this analysis. Surgical approach was left to the discretion of the surgeons. Patient characteristics and clinical outcomes were compared between MI-AVR and conventional AVR groups in the entire cohort ( n = 1077) and in an isolated AVR subcohort ( n = 528). Propensity score adjustment was performed to estimate the effect of MI-AVR on adverse events. Results Patients treated with MI-AVR were younger, had lower STS scores, and underwent concomitant procedures less often. Valve size implanted was comparable between the groups. MI-AVR was associated with longer procedural times in the isolated AVR subcohort. Postprocedural hemodynamic performance was comparable. There were no significant differences between MI-AVR and conventional AVR in early and 3-year all-cause mortality, thromboembolism, reintervention, or a composite of those endpoints within either the entire cohort or the isolated AVR subcohort. After propensity score adjustment, there remained no association between MI-AVR and the composite endpoint (hazard ratio: 0.86, 95% confidence interval: 0.47-1.55, p = 0.61). Conclusions Three-year outcomes after MI-AVR with the Avalus bioprosthetic valve were comparable to conventional AVR. These results provide important insights into the overall ability to reduce the invasiveness of AVR without compromising outcomes.Thoracic Surger