Right ventricular mechanics and its association with symptoms in transcatheter aortic valve replacement candidates: a three-dimensional echocardiography study

 

Aortic valve stenosis is one of the most prevalent valvular disease with significant clinical burden. While it is initially a disorder of the left ventricle (LV), long-term effects of the disease also affect the right ventricle (RV) as well. Nevertheless, data are scarce regarding the changes of RV mechanics and their association with symptomatic status of the patients. 3D echocardiography allows a more detailed assessment of the RV, which may unveil distinct changes of its morphology and function in this clinical setting.

Accordingly, our aim was to examine LV and RV mechanics in TAVR candidate patients with severe aortic stenosis using three-dimensional (3D) echocardiography.

Seventy patients (51% male, age: 80±6 years) were enrolled. Detailed medical history and symptomatic status were obtained. Beyond conventional transthoracic echocardiographic protocol, 3D loops were also acquired. We measured 3D LV and RV end-diastolic volume indexed to body surface area (EDVi), ejection fraction (EF) and global longitudinal (GLS) using dedicated software. Furthermore, we have determined 3D RV global longitudinal (RV GLS) and circumferential strain (RV GCS) using the ReVISION method.

LV EF (r=0.28, p<0.05) and LV GLS (r=−0.26, p<0.05) significantly correlated with age, while RV EF (r=0.21, p=0.11), RV GLS (r=−0.17, p=0.19) and RV GCS (r=−0.07, p=0.61) did not show association with it. 41% (n=29) of the patient population mentioned angina or had syncope. Patients with these symptoms had comparable LV EDVi (73±23 vs. 69±25 mL/m2, p=0.47), LV EF (47±15 vs. 51±10%, p=0.14) and LV GLS (−13.6±4.8 vs. −14.8±2.6%, p=0.25) to those who did not mention these complaints. On the other hand, patients with angina or syncope in their medical history had significantly lower RV EDVi (58±13 vs. 70±23 mL/m2, p<0.05), while having significantly higher RV EF (46±10 vs. 52±7%, p<0.05). Moreover, symptomatic patients had significantly lower RV GCS (−15.7±5.6 vs. −19.6±5.3%, p<0.01), while RV GLS did not differ (−15.8±4.8 vs. −17.4±4.1%, p=0.17).

Patients with severe aortic stenosis have marked changes in not only the LV, but the RV mechanics as well. While the symptomatic status does not seem to be associated with LV morphology and function, patients with angina or syncope had distinct changes in RV size and the contraction pattern of the chamber.

Funding Acknowledgement

Type of funding sources: None.

Hypoattenuated leaflet thickening is associated with silent brain injury

Background

The association between hypoattenuated leaflet thickening (HALT) following transcatheter aortic valve implantation (TAVI) and stroke remains contradictory. Whether HALT carries an increased risk of subclinical brain injury (SBI) has not been investigated.

Purpose

We investigated whether HALT is associated with SBI on MRI. Furthermore, we assessed whether post-TAVR SBI impacts the patients' cognition and outcome.

Methods

153 patients undergoing TAVR were prospectively enrolled. Brain MRI was performed shortly post-TAVR and 6 months (6M) later to assess the occurrence of acute silent cerebral ischaemic lesions (SCIL) and chronic white matter hyperintensities (WMH). HALT was screened by cardiac CT angiography 6M post-TAVR. Neurocognitive evaluation was performed before, shortly after and 6M following TAVR.

Results

At 6M, 115 patients had diagnostic CTA and 10 had HALT. HALT status, baseline and follow-up MRIs were available in 91 cases. At 6M, new SCIL was evident in 16%, new WMH in 66%. New WMH was more frequent (100% vs 62%; p=0.047) with higher median volume (319 vs 50 mm3; p=0.039) among HALT-patients. In uni- and multivariate analysis, HALT was associated with new WMH volume (beta: 0.72; 95% CI: 0.2–1.39; p=0.009).

The patients' cognitive trajectory from pre-TAVR to 6M showed significant association with the 6M SCIL volume (beta: −4.69; 95% CI: −9.13 to −027; p=0.038), but was not related to the presence or volume of new WMH. During a 3.1-year follow-up neither HALT, nor the related WMH burden was related with increased mortality (HALT HR: 0.86, 95% CI: 0,202–3,687; p=0.84; new WMH HR: 1.09; 95% CI: 0,701–1,680; p=0.71).

Conclusions

6M post-TAVR, HALT was linked with greater WMH burden, but did not carry an increased risk of cognitive decline or mortality over a 3.1-year follow-up.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): János Bolyai Scholarship of the Hungarian Academy of Sciences

Fibrin to von Willebrand factor ratio in arterial thrombi is associated with plasma levels of inflammatory biomarkers and local abundance of extracellular DNA

INTRODUCTION

The composition of thrombi determines their structure, mechanical stability, susceptibility to lysis, and consequently, the clinical outcome in coronary artery disease (CAD), acute ischemic stroke (AIS), and peripheral artery disease (PAD). Fibrin forms the primary matrix of thrombi intertwined with DNA, derived from neutrophil extracellular traps (NETs), and von Willebrand factor (VWF) bridging DNA and platelets. Here we examined the relative content of fibrin, DNA and VWF in thrombi and analyzed their interrelations and quantitative associations with systemic biomarkers of inflammation and clinical characteristics of the patients.

PATIENTS, METHODS

Thrombi extracted from AIS (n = 17), CAD (n = 18) or PAD (n = 19) patients were processed for scanning electron microscopy, (immune)stained for fibrin, VWF and extracellular DNA. Fibrin fiber diameter, cellular components, fibrin/DNA and fibrin/VWF ratios were measured.

RESULTS

Patients' age presented as a strong explanatory factor for a linear decline trend of the VWF content relative to fibrin in thrombi from CAD (adjusted-R² = 0.43) and male AIS (adjusted-R² = 0.66) patients. In a subgroup of CAD and PAD patients with dyslipidemia and high (above 80%) prevalence of atherothrombosis a significant correlation was observed between the VWF and DNA content in thrombi (adjusted-R² = 0.40), whereas a 3.7-fold lower linear regression coefficient was seen in AIS patients, in whom the fraction of thrombi of atherosclerotic origin was 57%. Independently of anatomical location, in patients with atherosclerosis the VWF in thrombi correlated with the plasma C-reactive protein levels.

CONCLUSIONS

The observed interrelations between thrombus constituents and systemic inflammatory biomarkers suggest an intricate interplay along the VWF/NET/fibrin axis in arterial thrombosis.

The impact of left atrial strain parameters on systolic and diastolic improvement following TAVI

Introduction

Transcatheter aortic valve implantation (TAVI) can improve left ventricular (LV) mechanics and has been shown to improve long term survival. Data on the prognostic value of left atrial (LA) strain following TAVI are scarce. LA strain – a surrogate of LV filling pressure - can aid the early detection of diastolic dysfunction and correlates with the extent of fibrosis in atrial remodelling.

Purpose

In this multimodality study, we aimed to evaluate the prognostic value of LA function measured before hospital discharge following TAVI and to further elucidate its association with LV and LA reverse remodelling.

Methods

In this prospective single center study, we investigated 90 patients (mean age 78.5 years, 46.7% female) with severe, symptomatic aortic stenosis (AS) who underwent transthoracic echocardiography immediately after TAVI and 6 months later. LA and LV global longitudinal strain parameters were obtained by speckle tracking echocardiography. CT angiography (CTA) was performed for pre-TAVI planning and repeated at 6 months follow-up. LV mass values were derived from the serial CTA images. We defined LV reverse remodelling as reduction of myocardial mass quantified on CTA and as an improvement of LV global longitudinal strain (GLS). LA reverse remodelling was assessed based on the peak reservoir strain values (LAGS). The association of LA and LV global strain parameters, LA stiffness, systolic and diastolic functional parameters and LV mass based reverse remodelling were analysed using Pearson correlation coefficient and linear regression models.

Results

The mean LAGS and LVGLS values were 17.7% and 15.3% at discharge and 20.2% and 16.6% at follow-up, respectively (p=0.024, p<0.001). LA and LV strain values improved in 60.6% and 74.5% of all patients. Reduced LAGS (<20%) was found in 66.7% of all patients at baseline. LA strain at discharge correlated significantly with diastolic parameters (E wave, E/e', LAVI, all p<0.05). Atrial reverse remodelling based on LAGS change correlated with LVGLS change (p<0.01, standardized β=0.53) and LAGS at discharge (p=0.012, standardized β=−0.30).

LAGS correlated with the extent of morphological LV remodelling based on LV mass reduction (p=0.002, coeff: 0.36). Elevated LA stiffness at discharge (upper tercile) leads to substantially lower LAGS at 6 months versus patients with lower LA stiffness value (1. and 2. tercile): 16.4±10.0 vs 21.9±9.8, p=0.042.

Conclusion

Patients with reduced LAGS immediately after TAVI showed a larger extent of LV reverse remodelling during follow up. On the other hand, increased LA stiffness at discharge was consistent with irreversible LA damage as demonstrated by a lack of improvement in LA function.

Funding Acknowledgement

Type of funding sources: None.

Left atrial appendage size is a marker of atrial fibrillation recurrence after radiofrequency catheter ablation in patients with persistent atrial fibrillation

Background

Catheter ablation is an established therapy for rhythm control in patients with drug-refractory atrial fibrillation (AF), however, recurrence is frequent particularly in persistent AF. There are no consistently confirmed predictors of AF recurrence after catheter ablation. The left atrial appendage (LAA) potentially plays an important role in AF recurrence, although the exact mechanism and pathophysiology are still unclear.

Purpose

We aimed to study whether LAA volume (LAAV) and function influence the long-term recurrence of AF after point-by-point radiofrequency catheter ablation, depending on AF type.

Methods

AF patients who underwent point-by-point radiofrequency catheter ablation after preprocedural cardiac computed tomography (CT) and transthoracic and transesophageal echocardiography (TEE) were included in this retrospective analysis. LAAV and LAA orifice area were measured by CT and LAA flow velocity assessed by TEE and was used as a surrogate marker of LAA function. Uni- and multivariable Cox proportional hazard regression models were performed to determine the predictors of AF recurrence.

Results

In total, 561 AF patients (61.9±10.2 years, 34.9% females) were included in the study. Recurrence of AF was detected in 40.8% of the cases (34.6% in patients with paroxysmal and 53.5% in those with persistent AF) with a median recurrence-free time of 22.7 [9.3–43.1] months. Patients with AF recurrence had significantly higher body surface area-indexed left atrial volume (iLAV), LAAV and LAA orifice area, as compared to those without recurrence. Moreover, patients with persistent AF had significantly higher iLAV, LAAV, LAA orifice area and lower LAA flow velocity, than those with paroxysmal AF. After adjustment for the main cardiovascular risk factors and comorbidities left ventricular ejection fraction (LVEF) <50% (HR=2.17; 95% CI=1.38–3.43; p<0.001) and LAAV (HR=1.06; 95% CI=1.01–1.12; p=0.029) were independently associated with AF recurrence in persistent AF, while no independent predictors could be identified in paroxysmal AF.

Conclusions

The current study demonstrates that beyond left ventricular systolic dysfunction, LAA enlargement is associated with higher rate of AF recurrence after catheter ablation in persistent AF, but not in patients with paroxysmal AF. Our results suggest that preprocedural assessment of LVEF and LAAV might contribute to optimal patient selection and aid to improve long-term results of ablation procedures in patients with persistent AF.

Funding Acknowledgement

Type of funding sources: None.

Quantification of hypo-attenuated leaflet thickening after transcatheter aortic valve implantation: clinical relevance of hypo-attenuated leaflet thickening volume

AIMS

Our aim was to establish an objective, quantitative methodology for volumetric hypo-attenuated leaflet thickening (HALT) diagnosis and evaluate its clinical significance.

METHODS AND RESULTS

We prospectively enrolled 144 patients who underwent transcatheter aortic valve implantation (TAVI) between 2011 and 2016. At inclusion, cardiac computed tomography angiography (CTA), transthoracic echocardiography, and brain magnetic resonance imaging (MRI) were performed. We quantified HALT on CTA datasets by segmenting the inner volume of TAVI frame at the level of leaflets and extracted voxels between a threshold of -200 to 200 HU based on prior recommendation. The median HALT volume was 72 [inter-quartile range (IQR): 1-154] mm3 (intra- and inter-reader agreement: intra-class correlation coefficient = 0.92 and 0.94, respectively) and 79% (n = 87/111) of the patients had HALT >0 mm3. In multivariate linear regression, oral anti-coagulation (β: -0.32; 95% CI: -0.62 to -0.01; P = 0.004) and history of myocardial infarction (β: 0.32; 95% CI: 0.01-0.63; P = 0.043) were associated with HALT quantity. Log-transformed HALT volume was associated with elevated (>13 mmHg) aortic mean gradient (AMG, OR: 12.85; 95% CI: 1.96-152.93; P = 0.021) and moderate-to-severe valvular degeneration (AMG ≥ 20 mmHg or ΔAMG ≥ 10 mmHg; OR: 10.56; 95% CI: 1.44-148.71; P = 0.046) but did not predict ischaemic brain lesions on MRI or all-cause death after a median follow-up of 29 (IQR: 11-29) months (all P > 0.05).

CONCLUSION

Through systematic analysis of asymptomatic patients with TAVI, an objective and reproducible methodology was feasible for volumetric measurement of HALT. Anti-coagulation might have a protective effect against HALT. Ischaemic brain lesions and all-cause death were not associated with HALT; nevertheless, it might deteriorate prosthesis function due to its association with elevated AMG.

CLINICAL TRIAL REGISTRATION

http//:www.ClinicalTrials.gov; NCT02826200.

Subclinical leaflet thrombosis is associated with impaired reverse remodelling after transcatheter aortic valve implantation

AIMS

Cardiac CT is increasingly applied for planning and follow-up of transcatheter aortic valve implantation (TAVI). However, there are no data available on reverse remodelling after TAVI assessed by CT. Therefore, we aimed to evaluate the predictors and the prognostic value of left ventricular (LV) reverse remodelling following TAVI using CT angiography.

METHODS AND RESULTS

We investigated 117 patients with severe, symptomatic aortic stenosis (AS) who underwent CT scanning before and after TAVI procedure with a mean follow-up time of 2.6 years after TAVI. We found a significant reduction in LV mass (LVM) and LVM indexed to body surface area comparing pre- vs. post-TAVI images: 180.5 ± 53.0 vs. 137.1 ± 44.8 g and 99.7 ± 25.4 vs. 75.4 ± 19.9 g/m2, respectively, both P < 0.001. Subclinical leaflet thrombosis (SLT) was detected in 25.6% (30/117) patients. More than 20% reduction in LVM was defined as reverse remodelling and was detected in 62.4% (73/117) of the patients. SLT, change in mean pressure gradient on echocardiography and prior myocardial infarction was independently associated with LV reverse remodelling after adjusting for age, gender, and traditional risk factors (hypertension, body mass index, diabetes mellitus, and hyperlipidaemia): OR = 0.27, P = 0.022 for SLT and OR = 0.22, P = 0.006 for prior myocardial infarction, OR = 1.51, P = 0.004 for 10 mmHg change in mean pressure gradient. Reverse remodelling was independently associated with favourable outcomes (HR = 0.23; P = 0.019).

CONCLUSION

TAVI resulted in a significant LVM regression on CT. The presence of SLT showed an inverse association with LV reverse remodelling and thus it may hinder the beneficial LV structural changes. Reverse remodelling was associated with improved long-term prognosis.

P1831 Predictors and clinical consequences of silent ischaemic brain lesions following transcatheter aortic valve implantation

Funding Acknowledgements

This study was supported by the János Bolyai Scholarship of the Hungarian Academy of Sciences

Background

A number of studies aimed to identify the predictors of periprocedural cerebral embolizations related to transcatheter aortic valve implantation (TAVI). Much less investigated is the prevalence and determinants of subacute ischaemic brain lesions that develop following TAVI.

Purpose

We sought to identify predictors of subacute clinically silent ischaemic brain lesions in patients following TAVI.

Methods

Patients were included from the Rule out Transcatheter Aortic Valve Thrombosis with Post Implantation Computed Tomography (RETORIC) prospective trial. Echocardiography and brain MRI were performed after TAVI procedure, before hospital discharge. Cardiac CT was performed 6 months later to identify subclinical leaflet thrombosis (HALT), as well as repeat brain MRI, to identify any silent ischaemic lesions that appeared since the intervention. The cognitive trajectory of patients was assessed using the Addenbrookes cognitive test (ACE), performed shortly after TAVI and at 6-month follow-up (FU). All-cause mortality data was retrieved from the National Mortality Database.

Results

79 consecutive patients were included in the present analysis. 28% had known history of atrial fibrillation (AF). 33% of the cohort was treated with oral anticoagulant, of these 56% with single and 25% with dual antiplatelet therapy (DAPT). The mean CHA2DS2VASC score was 4. From discharge to the 6-month FU, 20 patients (25%) developed new silent ischaemic brain lesions on MRI. Clinically manifest stroke did not occur. On the 6-month CT, HALT was identified in 6 patients (8%). Clinical and imaging parameters, including age, body mass index, hypertension, dyslipidaemia, diabetes, smoking, statin-, OAC- and DAPT therapy, history of AF, history of stroke, echocardiographic metrics of left ventricular (ejection fraction, stroke volume index) and atrial (left atrial strain) function as well as HALT were analysed for association with ischaemic brain lesions. Of the above, only HALT showed significant association (OR:6,58; p = 0.04) with silent brain embolizations. The cognitive trajectory from discharge till 6-month FU did not differ between patients with or without ischaemic focuses (ΔACEscore: 1.0 vs. 0.1; p = NS). Over a median FU of 553 (IQR 453 – 665) days, 8 patients died; 2 with and 6 without ischaemic lesions. Kaplan-Meyer analysis showed no difference in outcome between the two groups (p = 0.68)

Conclusion

Subclinical leaflet thrombosis was identified as a significant predictor of subacute silent ischaemic brain lesions after TAVI. These lesions did not affect the overall cognitive performance or outcome of the patients.

P3381Quantification of hypo-attenuated leaflet thickening after transcatheter aortic valve implantation - clinical relevance of HALT volume

Background

Hypo-attenuated leaflet thickening (HALT) is a recently recognized phenomenon following transcatheter aortic valve implantation (TAVI) and there is no consensus over the standardized assessment of HALT and its clinical relevance is poorly understood. We sought to determine the predictors and clinical significance of HALT volume.

Methods

Patients, who previously underwent TAVI between 2011 and 2016 were prospectively enrolled in the RETORIC (Rule out Transcatheter Aortic Valve Thrombosis with Post Implantation Computed Tomography) study, a single-center observational study. At inclusion cardiac computed tomography angiography (CTA), transthoracic echocardiography (TTE) and brain magnetic resonance imaging (MRI) was performed. HALT was volumetrically quantified on cardiac CTA images by segmenting the inner volume of the TAVI frame at the level of the leaflets and applying a threshold of −200 to 200 Hounsfield units. We evaluated the clinical predictors of HALT volume, and its association with ischemic brain MRI lesions (recent and chronic large vessel ischemic focuses, microbleed/microembolization, white matter or small vessel disease) and all-cause mortality.

Results

In total, we analyzed 111 patients with CoreValve bioprosthesis (56.7% female, mean age 80.3±7.4 years). A median of 19 [IQR: 11–29] months passed between TAVI procedure and enrollment. The mean HALT volume was 111.0±163.4 mm3. Current malignant disease, prosthesis implantation depth measured on CTA images acquired at inclusion, and aortic mean gradient and aortic valve area evaluated on TTE images at inclusion predicted HALT volume by univariate analysis (all p<0.05). After multivariate adjustment, aortic mean gradient remained a significant predictor of HALT volume (beta-coefficient: 11.5, 95% CI: 5.0–18.0; p<0.001). HALT volume was not associated with ischemic brain MRI lesions (all p>0.05) and did not predict all-cause mortality (median follow-up: 20 months [IQR: 18–23]; HR: 1.0; 95% CI: 1.0–1.0; p=0.15).

Volumetric quantification of HALT.

Conclusion

Aortic mean gradient was the only predictor independently associated with HALT volume. Our results suggest that TAVI valve function is negatively affected by HALT volume, however, we found no association of HALT volume with cerebrovascular ischemic lesions or increased risk for all-cause mortality.

Neutrophil extracellular traps in thrombi retrieved during interventional treatment of ischemic arterial diseases

INTRODUCTION

The ultrastructure and cellular composition of thrombi has a profound effect on the outcome of acute ischemic stroke (AIS), coronary (CAD) and peripheral artery disease (PAD). Activated neutrophils release a web-like structure composed mainly of DNA and citrullinated histones, called neutrophil extracellular traps (NET) that modify the stability and lysability of fibrin. Here, we investigated the NET-related structural features of thrombi retrieved from different arterial localizations and their interrelations with routinely available clinical data.

PATIENTS AND METHODS

Thrombi extracted from AIS (n = 78), CAD (n = 66) or PAD (n = 64) patients were processed for scanning electron microscopy, (immune)stained for fibrin, citrullinated histone H3 (cH3) and extracellular DNA. Fibrin fiber diameter, cellular components, DNA and cH3 were measured and analyzed in relation to clinical parameters.

RESULTS

DNA was least present in AIS thrombi showing a 2.5-fold lower DNA/fibrin ratio than PAD, whereas cH3 antigen was unvaryingly present at all locations. The NET content of thrombi correlated parabolically with systemic inflammatory markers and positively with patients' age. The median platelet content was lower in PAD (2.2%) than in either AIS (3.9%) or CAD (3.1%) and thrombi from smokers contained less platelets than non-smokers. Fibrin fibers were significantly thicker in male patients with CAD (median fiber diameter 76.3 nm) compared to AIS (64.1 nm) or PAD (62.1 nm) and their diameter correlated parabolically with systemic inflammatory markers.

CONCLUSIONS

The observed NET-related variations in thrombus structure shed light on novel determinants of thrombus stability that eventually affect both the spontaneous progress and therapeutic outcome of ischemic arterial diseases.

Left atrial rather than left ventricular impaired mechanics are associated with the pro-fibrotic ST2 marker and outcomes in heart failure with preserved ejection fraction

AIMS

Left ventricular (LV) mechanics have been extensively investigated in heart failure with preserved ejection fraction (HFpEF) overshadowing for a long time the potential role of left atrium (LA) in that setting. Soluble suppression of tumorigenicity-2 receptor (ST2) is a novel biomarker of pro-fibrotic burden in HF. We hypothesized that due to the thinner LA wall, the fibrotic myocardial changes in HFpEF as indicated by elevated ST2 levels might more readily be reflected by impairments in the LA rather than the LV performance.

METHODS AND RESULTS

In 86 patients with HFpEF, enrolled in the Karolinska Rennes (KaRen) biomarker prospective substudy, global LA strain (GL-LS) along with other echocardiographic as well as haemodynamic parameters and ST2 levels were measured. ST2 levels were inversely associated with LA-GS (r = -0.30, P = 0.009), but not with LA size, LV geometry, systolic or diastolic LV function (P > 0.05 for all). Furthermore, symptom severity correlated with ST2 and LA-GS, but not with LV structural or functional indices. Finally, during a median 18-month follow-up, LA-GS independently predicted the composite endpoint of HF hospitalization and all-cause mortality, even after adjustment for potential clinical and cardiac mechanical confounders, including LV global longitudinal strain and filling pressures (odds ratio: 4.15; confidence interval: 1.2-14, P = 0.023).

CONCLUSIONS

Reduced LA-GS but not LV functional systolic and diastolic parameters were associated with the pro-fibrotic ST2 marker, HF symptoms and outcome in HFpEF.

IP3 signalling regulates exogenous RNAi in Caenorhabditis elegans

RNA interference (RNAi) is a widespread and widely exploited phenomenon. Here, we show that changing inositol 1,4,5-trisphosphate (IP3) signalling alters RNAi sensitivity in Caenorhabditis elegans. Reducing IP3 signalling enhances sensitivity to RNAi in a broad range of genes and tissues. Conversely up-regulating IP3 signalling decreases sensitivity. Tissue-specific rescue experiments suggest IP3 functions in the intestine. We also exploit IP3 signalling mutants to further enhance the sensitivity of RNAi hypersensitive strains. These results demonstrate that conserved cell signalling pathways can modify RNAi responses, implying that RNAi responses may be influenced by an animal's physiology or environment.

The pulmonary capillary wedge pressure accurately reflects both normal and elevated left atrial pressure

BACKGROUND

Pulmonary capillary wedge pressure (PCWP) is routinely used as an indirect measure of the left atrial pressure (LAP), although the accuracy of this estimate, especially under pathological hemodynamic conditions, remains controversial.

OBJECTIVES

The aim of this prospective study was to investigate the reliability of PCWP for the evaluation of LAP under different hemodynamic conditions.

METHODS

Simultaneous left and right heart catheterization data of 117 patients with pure mitral stenosis, obtained before and immediately after percutaneous mitral comissurotomy, were analyzed.

RESULTS

A strong correlation and agreement between PCWP and LAP measurements was demonstrated (correlation coefficient = 0.97, mean bias ± CI, 0.3 ± -3.7 to 4.2 mm Hg). Comparison of measurements performed within a 5-minute interval and those performed simultaneously revealed that simultaneous pressure acquisition yielded better agreement between the 2 methods (bias ± CI, 1.82 ± 1.98 mm Hg). In contrast to previous observations, the discrepancy between the 2 measures did not increase with elevated PCWP. Multiple regression analysis failed to identify hemodynamic confounders of the discrepancy between the 2 pressures. The ability of PCWP to distinguish between normal and elevated LAP (cutoff set at 12 and 15 mm Hg, respectively), as tested by receiver operating characteristics analysis, demonstrated a remarkably high diagnostic accuracy (area under the curve: 0.989 and 0.996, respectively).

CONCLUSIONS

Although the described limits of agreement may not allow the interchangeability of PCWP and LAP, especially at lower pressure ranges, our data support the clinical use of PCWP as a robust and accurate estimate of LAP.

Phospholipase C-epsilon regulates epidermal morphogenesis in Caenorhabditis elegans

Migration of cells within epithelial sheets is an important feature of embryogenesis and other biological processes. Previous work has demonstrated a role for inositol 1,4,5-trisphosphate (IP₃)-mediated calcium signalling in the rearrangement of epidermal cells (also known as hypodermal cells) during embryonic morphogenesis in Caenorhabditis elegans. However the mechanism by which IP₃ production is stimulated is unknown. IP₃ is produced by the action of phospholipase C (PLC). We therefore surveyed the PLC family of C. elegans using RNAi and mutant strains, and found that depletion of PLC-1/PLC-ε produced substantial embryonic lethality. We used the epithelial cell marker ajm-1::gfp to follow the behaviour of epidermal cells and found that 96% of the arrested embryos have morphogenetic defects. These defects include defective ventral enclosure and aberrant dorsal intercalation. Using time-lapse confocal microscopy we show that the migration of the ventral epidermal cells, especially of the leading cells, is slower and often fails in plc-1(tm753) embryos. As a consequence plc-1 loss of function results in ruptured embryos with a Gex phenotype (gut on exterior) and lumpy larvae. Thus PLC-1 is involved in the regulation of morphogenesis. Genetic studies using gain- and loss-of-function alleles of itr-1, the gene encoding the IP₃ receptor in C. elegans, demonstrate that PLC-1 acts through ITR-1. Using RNAi and double mutants to deplete the other PLCs in a plc-1 background, we show that PLC-3/PLC-γ and EGL-8/PLC-β can compensate for reduced PLC-1 activity. Our work places PLC-ε into a pathway controlling epidermal cell migration, thus establishing a novel role for PLC-ε.

Morphogenesis is a fundamental part of development which underlies the ability of animals, including humans, to define the shape of their tissues and organs and thus enable their proper function. To understand morphogenesis we need to understand the signalling networks that regulate coordinated changes in cell morphology, movement and adhesion. We know that in C. elegans intracellular signalling through the messenger inositol 1,4,5-trisphosphate (IP₃) is required for the proper completion of the morphogenetic processes. However the mechanism by which this signal is produced remains unclear. In this work we define the mechanism responsible for IP₃ production in C. elegans. We use a combination of genetic and morphological analysis to show that phospholipase C-epsilon (PLC-ε) is the molecule responsible for IP₃ production. In worms with disrupted PLC-ε the embryonic epidermal cells fail to migrate properly so that morphogenesis fails. PLC-ε was only discovered relatively recently and interacts directly with a wide range of signalling pathways, including others that are known to regulate important cellular properties during morphogenesis such as small GTPases. Therefore we establish a potential link between IP₃ signalling and other pathways that are known to be involved in cell movements. This is an important advance in defining the network of interactions that regulate epithelial cell movements in morphogenesis.

Chaperone-mediated coupling of endoplasmic reticulum and mitochondrial Ca2+ channels

The voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane mediates metabolic flow, Ca(2+), and cell death signaling between the endoplasmic reticulum (ER) and mitochondrial networks. We demonstrate that VDAC1 is physically linked to the endoplasmic reticulum Ca(2+)-release channel inositol 1,4,5-trisphosphate receptor (IP(3)R) through the molecular chaperone glucose-regulated protein 75 (grp75). Functional interaction between the channels was shown by the recombinant expression of the ligand-binding domain of the IP(3)R on the ER or mitochondrial surface, which directly enhanced Ca(2+) accumulation in mitochondria. Knockdown of grp75 abolished the stimulatory effect, highlighting chaperone-mediated conformational coupling between the IP(3)R and the mitochondrial Ca(2+) uptake machinery. Because organelle Ca(2+) homeostasis influences fundamentally cellular functions and death signaling, the central location of grp75 may represent an important control point of cell fate and pathogenesis.