Analysis of myocardial salvage with cardiac magnetic ressonance and angiography depending on the STEMI revascularization pathway in a PPCI centre

Background

Reperfusion networks have permitted improvements in reperfusion delays in primary percutaneous coronary intervention (PPCI)-treated ST elevation myocardial infarction (STEMI). However, the impact on myocardial salvage (MS) of direct transfer to the catheterization laboratory (cath-lab) to minimize system delay remains unknown.

Objective

We sought to quantify the myocardial salvage index (MSI) acutely and to assess adverse remodeling at 6 months in PPCI-treated STEMI according to the mode of patient presentation.

Methods

Between 2005 and 2021 we included 493 patients in a single center registry of first PPCI-treated STEMI who were studied with Late gadolinium enhanced (LGE) cardiac magnetic resonance (CMR) in the acute phase. Among them, 414 (84.0%) underwent a second LGE-CMR at 6 months. Subjects were classified depending on the mode of presentation: those diagnosed out-of-hospital and directly transferred to the cath-lab by the Emergency Medical Services (EMS group, 29.82%); subjects with first medical contact in a PCI-capable hospital (PCI-H group, 41.75%); and patients presenting to a non-PCI-capable center and transferred for PCI (non-PCI-H group, 28.43%). We computed the angiographic area at risk by BARI score, and combined it with the LGE-CMR derived infarct size to compute a validated MSI, expressed as percentage of area at risk. The change in ejection fraction (EF) and indexed left ventricle end-diastolic volume (iLVEDV) from baseline to 6 months was also computed.

Results

The mean age was 58.9±11.9 years, 84.5% were male and 51.4% had anterior STEMI. Total median ischaemic time was (median (interquartile range)) 126 (105–161) min in the EMS group, 201 (145–321) min in the PCI-H group and 300 (173–592) min in the non-PCI-H group (p<0.01). MSI was 45.28±2.6%, 39.63±2.2% and 35.53±2.7% respectively (p=0.034). In a multiple linear regression model adjusting for relevant covariables, including initial TIMI flow, area at risk, Killip class, age, sex, diabetes, number of vessels and presence of collaterals, a 7.50% (95% CI 0.9 to 14.1%) increase in MSI was observed in the EMS group compared to the PCI-H group, and 11.03% (95% CI 3.9 to 18.2%) compared to the non-PCI-H group (p=0.027 and 0.003 respectively). At 6 months, the mean absolute increase in EF was 5.36±0.6% for the EMS group, 4.03±0.5% for the PCI-H group and 3.52±0.6% for the non-PCI-H group (p<0.05 in the adjusted analysis) and the increase in iLVEDV was 2.37±7.3, 5.51±6.6 and 18.30±7.6 mL/m2 respectively (p=0.28).

Conclusions

Patients with out-of-hospital diagnostis of STEMI by the EMS who were directly transferred to the cath-lab showed shorter total ischaemic times, resulting in increased myocardial salvage and a trend towards improved indexes of left ventricular function at 6 months.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Grant from La Maratό de TV3 and grant from Fundaciό La Caixa

Cardiac injury before and after COVID-19. A longitudinal MRI study

Background

Recent MRI-based studies have raised great concern about frequent cardiac involvement even in mild or asymptomatic COVID-19. However, while signs of myocardial injury were found in large proportions of patients after COVID-19, all studies published to date lack baseline imaging and are therefore unable to discriminate between pre-existing and COVID-19-induced injury.

Purpose

In this longitudinal study, we aimed to assess the true cardiac impact of COVID-19 based on pre- and post-COVID-19 late gadolinium enhancement (LGE)-MRI.

Methods

A prospective registry of patients with serial LGE-MRIs was screened for patients with documented SARS-COV-2 infection after cardiac LGE-MRI. Eligible patients then received a post-COVID-19 LGE-MRI using the same scanner and sequence as in the pre-COVID-19 MRI. Inversion recovery prepared T1-weighted gradient echo sequences were acquired in sinus rhythm using ECG gating and a free-breathing 3D navigator, 15–20 minutes after administering an intravenous bolus of 0.2 mmol/kg of gadobutrol. A TI scout sequence was used in order to determine the optimal TI that nullified the left ventricular myocardial signal. The presence of LGE was independently assessed qualitatively by two experienced investigators blinded to patient information. For quantitative analyses a 3D-reconstruction of the left ventricle was performed using ADAS-3D software. LGE was then automatically quantified based on a prespecified signal intensity threshold of ≥3 SD above the mean of a remote non-enhanced myocardial region.

Results

Pre- and post-COVID LGE-MRI from 31 patients with cardiovascular risk factors that had recovered from mild to moderate COVID-19 (23% hospitalised) were analysed. At a median of 5 months post-COVID-19, LGE-lesions indicative of myocardial injury were encountered in 15 out of 31 patients (48%), which is in line with previous reports. However, intraindividual comparison with the pre-COVID-19 MRI reveiled all of these lesions as pre-existing and thus not COVID-19-related. Quantitative analysis detected no increase in the size of individual LGE-lesions, nor in the global left ventricular LGE-extent. There was no difference in any functional or structural parameter between pre- and post-COVID-19 MRI.

Conclusion

This longitudinal study in a cohort of patients considered at high risk of cardiac involvement, did not find any evidence for COVID-19-induced myocardial injury. The complete absence of de novo LGE lesions in this cohort is reassuring and indicates that cardiac sequelae of COVID-19 are rare and certainly not as common as previously suggested.

Funding Acknowledgement

Type of funding sources: None.

[Not Available]

INTRODUCTION

Total knee arthroplasty (TKA) is a surgery that aims to restore function and relieve pain in advanced osteoarthritis. The Educational Workshop (EW) for TKA is given to patients in the pre-surgery period to inform them and facilitating their participation in their health process (empowerment). The aim of this study was developing and validating a self-administered questionnaire to evaluate the acquired knowledge after the EW by the patients who will undergo the TKA procedure.

MATERIAL AND METHODS

It was a longitudinal and prospective observational study with a sample of TKA candidate patients. The phases for the construction and validation of this ad hoc questionnaire were: Phase 1: A panel of experts who agreed on a final questionnaire of 20 items; Phase 2: Pilot test administered to 47 patients; Phase 3: Final test of 11 items administered to 50 patients, before and after the EW; Phase 4: Re-test, after the EW and 2 weeks after, administered to 58 patients.

RESULTS

One hundred and fifty five patients were included. The Cronbach's alpha coefficient for the item's internal consistency of the final questionnaire, 11 items, was 0.78. To reach the criterion validity, in pre-EW the mean number of hits was: 4.92 (SD=1.78) and in post-EW 10.68 (SD=0.55), a difference that had a statistical significance p<.0001, with no overlap in the 95% CI of the mean: 4.46-5.38/10.54-10.82. The test for stability and reliability, re-test, obtained a mean of right answers 10.87 (SD=0.33) and for the re-test of 10.70 (SD=0.59). The correlation of the interclass coefficient for the re-test was 0.99, which corresponds almost to a maximum concordance.

CONCLUSIONS

The questionnaire developed in this study is a reliable and easy tool to evaluate the acquired knowledge in the EW for patients who will be TKA operated.

Exploring phenotypes in hypertrophic cardiomyopathy with machine learning data integration. A multicentric, multimodality pilot study

Background

Interpreting patient phenotypes is a challenge when screening for hypertrophic cardiomyopathy (HCM). Machine learning (ML) can potentially help with advanced data integration - combining information contained in whole-cardiac cycle echo deformation and velocity profiles with standard clinical variables. The aim is to apply an ML approach to integrate whole cardiac cycle echo data with clinical variables to explore HCM phenotypes.

Methods

The cohort consisted of 138 participants from two centres: HCM patients (n=91) and relatives (n=47). Echocardiography was performed, whereas magnetic resonance and genetic testing in 48% and 82%, respectively. Whole cardiac cycle echo data (mitral and aortic velocity profiles, and six regional left ventricular (LV) deformation curves) were combined with clinical variables (age, sex, heart rate, e' medial and e' lateral) and used as the ML input. An unsupervised ML algorithm created a representative space where participants were positioned based on integrated data, blinded to disease status. Clustering was used to determine phenogroups and estimate the average characteristics. Data on family history (FHx), genotype, arrhythmias or syncope, implantable cardioverter-defibrillators (ICD), and late gadolinium enhancement (LGE) were used to interpret the phenogroups. As the LA diameter was not available in the dataset, the HCM risk for sudden cardiac death (SCD) was not calculated, however, the Table shows relevant variables to infer clinical risk.

Results

Clustering divided the participants into 6 phenogroups (P1–6) (Figure). Average echo profiles are shown in the Figure, while the clinical data in the Table. P1/2 was defined by symptomatic patients with a high prevalence of positive genotypes, a positive FHx of SCD, and a burden of comorbidities. Echo findings showed pronounced structural/functional remodeling, and P1 was associated with severe septal hypertrophy and outflow tract obstruction. The high prevalence of ICD devices defined P1/2 as high risk groups. In comparison, patients in P3/4 were younger, with milder LV hypertrophy, but still considerable functional impairment. P3 had a higher burden of FHX and a higher prevalence of pathogenic mutations, whereas P4 a higher incidence of hypertension, high heart rate, mitral inflow fusion and findings of LGE. Finally, P5/6 consisted of younger individuals, predominantly HCM relatives, with a mild phenotype and, thus, low inferred risk. As expected, the majority of patients with the genetic variants of undetermined significance were located in P5.

Conclusion

ML can help derive clinically interpretable phenotypes in HCM based on the automated integration of whole cardiac cycle deformation and velocity data with conventional clinical parameters. The derived phenogroups correspond with established risk profiles in HCM. An expanded dataset is needed to enable further exploration of the phenotype-genotype relations and to define prognostic value.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): This work was supported by the Horizon 2020 European Commission Project H2020-MSCA-ITN

Biomechanical demands of percussive techniques in the context of early stone toolmaking

Recent discoveries in archaeology and palaeoanthropology highlight that stone tool knapping could have emerged first within the genera Australopithecus or Kenyanthropus rather than Homo. To explore the implications of this hypothesis determining the physical demands and motor control needed for performing the percussive movements during the oldest stone toolmaking technology (i.e. Lomekwian) would help. We analysed the joint angle patterns and muscle activity of a knapping expert using three stone tool replication techniques: unipolar flaking on the passive hammer (PH), bipolar (BP) flaking on the anvil, and multidirectional and multifacial flaking with free hand (FH). PH presents high levels of activity for Biceps brachii and wrist extensors and flexors. By contrast, BP and FH are characterized by high solicitation of forearm pronation. The synergy analyses depict a high muscular and kinematic coordination. Whereas the muscle pattern is very close between the techniques, the kinematic pattern is more variable, especially for PH. FH displays better muscle coordination and conversely lesser joint angle coordination. These observations suggest that the transition from anvil and hammer to freehand knapping techniques in early hominins would have been made possible by the acquisition of a behavioural repertoire producing an evolutionary advantage that gradually would have been beneficial for stone tool production.

Validation of a deep learning reconstruction framework for 3D delayed myocardial enhancement imaging

Funding Acknowledgements

Type of funding sources: None.

Introduction

Myocardial delayed enhancement (MDE) MRI plays an important role in the identification of several cardiac conditions, both ischemic and non-ischemic (e.g. myocarditis, IDC, amyloidosis). 3D imaging offers increased resolution, full heart coverage and better depiction of complex pathologies, but its image quality is limited by long acquisition times.

Deep learning (DL) models enable advanced reconstruction algorithms that yield regularized images in practical computation times. In this study we evaluate a novel 3D-DL reconstruction to overcome the trade-off between reconstructed quality and acquisition time on MDE data.

Methods

A group of 14 subjects referred for CMR (5 F / 9 M, 59 ± 11 y.o., 78 ± 13 kg) were scanned with a 3D MDE sequence prototype: SPGR with IR preparation, fat & spatial saturation, respiratory navigator, ARC 2x, FOV 40x40cm, ST 1.4-2.4mm, matrix 280²-320², FA 20deg, BW 62.5 kHz, TE 2.1 ± 0.1ms, TI based on a CINE IR scout. All were retrospectively reconstructed using a 3D DL algorithm, trained on a database of over 700 datasets to reconstruct high-quality images with adjustable noise reduction.

The images were compared with standard 3D Cartesian reconstruction by two experienced cardiologists, to identify alterations in morphology or contrast distribution. Noise was estimated using the intensity standard deviation on a blood pool ROI. Feature preservation was estimated using the structural similarity index (SSI).

Results

The new method improved perceived image quality without loss of structural information or resolution (fig 1). Quantitative analysis (fig 2) confirmed these results: The average coefficient of variation in the blood was 0.08 ± 0.02 in the reference and 0.05 ± 0.02 with the new method; Given a target image noise level, DL reconstruction yielded up to 10% better SSI, compared to anisotropic filtering.

The clinical review didn’t reveal diagnostically significant alterations of structure or uptake pattern. A perceived reduction of sharpness was initially reported but individual examination of landmarks (e.g. pulmonary and coronary arteries) confirmed that no relevant features were being lost with the new reconstruction.

Discussion

The 3D MDE images obtained with DL reconstruction improved the trade-off between image noise -estimated by the blood pool intensity deviation- and feature preservation -estimated by SSI-.

Consistent improvement of image quality without morphological alterations of diagnostic relevance indicates that the new method can be considered for clinical practice. The next step in the validation process will require testing the robustness over a large set of cases with heterogeneous acquisition settings.

Conclusion

We presented the preliminary evaluation of a deep learning reconstruction method with 3D myocardial delayed enhancement data. The results show systematic improvement of overall image quality without loss of relevant diagnostic information.

Abstract Figure.

Improving the robustness of MOLLI T1 maps with a dedicated motion correction algorithm

Funding Acknowledgements

Type of funding sources: None.

Introduction

Myocardial T1 mapping constitutes a reliable indicator of heart diseases related to changes of myocardial extracellular content (e.g. oedema, fibrosis) as well as fat, iron and amyloid content.

T1-mapping techniques rely on fitting a model to a series of MRI measurements. Alignment between these measurements is required for accurate T1 estimation. This is limited by triggering accuracy and patient motion. Image registration is often applied to improve the alignment. In the case of MOLLI series, registration is compromised by contrast variation between the images.

We present the validation of a new registration method, designed to account for the contrast properties of MOLLI data.

Methods

A cohort of 186 patients referred for a CMR was included in this study (115 M / 71 F; weight 75 ± 15 Kg; age 55 ± 16). Scans on a 3.0T MR included a MOLLI sequence with target parameters: 2D bSSFP, 160x148, pFOV 0.8-1.0, 1.4x1.4mm², ST 8mm, TE 1.4ms, TR 3.0ms, FA 35deg, NEX 1, BW 100kHz, 2x ASSET, 5(3)3.

Cartesian 2D reconstruction followed by motion correction was applied retrospectively. A new correction algorithm was implemented, based on a similarity criterion that accounted for T1 relaxation: It consisted of an iterative approach alternating polarity estimation, T1 fitting, relaxation simulation and frame registration. The coefficient of determination (R²) was used as a quality measure. A representative subset of the results was reviewed by two experienced cardiologists.

Results

All reconstructions (totalling 1133 2D MOLLI series) yielded qualitatively correct T1 maps. Results with the new method were compared to conventional motion correction and no correction.

The number of pixels with R²&gt;0.95 was 85%±9% with standard motion correction and 90%±7% with the new dedicated method. In terms of improvement w.r.t. uncorrected data, the standard method yielded +3%±8% and the new one +9%±8%. Motion correction caused noticeable performance degradation in 12% of cases with the standard method, compared to 0.2% with the proposed method.

The relative performance of the different methods can be appreciated in Figure 3.

Discussion

Despite T1 mapping techniques constituting a reliable diagnostic tool in cardiac imaging, they remain sensitive to patient motion and triggering inaccuracies, making them vulnerable to arrhythmia episodes.

Improving the similarity criterion by accounting for T1 relaxation significantly decreased the incidence of misregistration and subsequent T1 inaccuracies. Using the R² of the voxel-wise T1 fit as a surrogate of alignment allowed to confirm the increased robustness of the new, dedicated motion correction method for MOLLI series.

Conclusion

We have demonstrated a new reconstruction pipeline with built-in registration, optimized for MOLLI T1-mapping. Using a large database of clinical data, the new method has been shown to improve the robustness to motion of cardiac T1 mapping.

Abstract Figure.

Aetiology-discriminative multimodality imaging of hypertrophic cardiomyopathy: deformation patterns relate to synchrotron-based assessment of microstructural tissue remodelling

Funding Acknowledgements

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Horizon 2020 European Commission Project H2020-MSCA-ITN-2016 (764738) and the Clinical Research in Cardiology grant from the Spanish Cardiac Society.

Background

The aetiology of left ventricular hypertrophy (LVH) is a relevant clinical challenge with consequences for patient management. Phenotypes resulting from hypertensive remodelling and sarcomere mutation often overlap. Synchrotron X-ray phase-contrast imaging (X-PCI) is a technique that can provide 3-dimensional detailed information on myocardial micro-structure non-destructively. The aim is to relate macrostructural/functional, non-invasive, imaging phenotypes of hypertrophic cardiomyopathy (HCM) to the underlying myocardial microstructure assessed with X-PCI.

Methods

Myocardial tissue samples were obtained from three patients (P1-3) with obstructive myocardial hypertrophy undergoing septal myectomy. Medical history and the 5-year HCM risk scores were evaluated. The patients were imaged with magnetic resonance imaging and echocardiography prior to procedure. Myocardial structure was assessed with wall thickness, late gadolinium enhancement (LGE), whereas function with speckle-tracking deformation (STE) and tissue Doppler imaging (TDI). Myectomy tissue was imaged with X-PCI in the TOMCAT beamline, using a multiscale propagation-based protocol combining a low-resolution (LR) and a high-resolution (HR) setup (5.8 and 0.7 um pixel size, respectively).

Results

The clinical and imaging data are shown in Fig 1. On initial assessment, wall thickness, LGE distribution, global longitudinal strain and septal TDI demonstrated a similar macrostructural and functional phenotype of P1 and P2, whereas P3 stood out with more severe hypertrophy, scarring and dysfunction. Additional regional deformation analysis with STE revealed reduced deformation in the basal and mid septum in P1, paired with a hypertensive pattern of post-systolic shortening (PSS) (yellow arrows). In comparison, in P2 and P3, deformation was more heterogeneous regionally, with regions of almost complete absence of deformation (orange arrows). Upon further exploration with TDI, areas with abnormal deformation were identified on the transition from basal to mid septum in both P2 and P3, whereas deformation was normal, but reduced in P1, and paired with PSS. LR X-PCI defined regions of interest to scan with HR (yellow frame), where HR revealed extensive interstitial fibrosis (orange arrow) with normal myocyte size and organisation in P1, compatible with severe hypertensive remodelling. However, in P2 and P3, patches of fibrosis (yellow arrow) paired with enlarged myocytes organized in visible disarray, considerably more prominent in P3, were both compatible with sarcomere-mutation HCM.

Conclusion

The results demonstrate multiscale phenotyping of HCM - relating micro- and macrostructural findings to function, and integrating multimodality data. In-depth regional deformation analysis, validated by synchrotron-based microstructural analysis, showed potential to identify distinct imaging phenotypes in HCM, distinguishing between overlapping presentations in different aetiologies.

Abstract Figure 1

T1 mapping of the remote non-infarct myocardium for predicting adverse left ventricular remodeling following STEMI

Background

Adverse Left Ventricular (LV) remodeling (ALVR) following ST-segment Elevation Myocardial Infarction (STEMI) is the result of numerous mechanical, neurohormonal, micro and macrovascular factors, and remains a major clinical problem. Cardiac Magnetic Resonance (CMR) is a multimodality technique that provides comprehensive functional and tissue characterization of infarcted and non-infarcted myocardium. Whether changes in the extracellular matrix in the remote myocardium in patients following a STEMI are associated with adverse LV remodeling has been a topic of debate.

Aim

We explored the additive value of native T1 variation (ΔnT1) and derived-extracellular volume (ECV) fraction in the remote non-infarcted myocardium as predictors of adverse LV remodeling following STEMI.

Methods

A total of 99 subjects (83% male) with their first mechanically reperfused STEMI underwent CMR within 2 weeks and at 6 months, including T1 mapping prior and 15 to 20 minutes following a bolus of gadolinium (0.2 mmol/kg), with a MOLLI sequence. ECV and nT1 values were computed by averaging co-registered ROIs in three distinct segments in the remote non-infarcted myocardium.

Results

Baseline nT1 but not ECV correlated with infarct size (r=0.349, P&lt;0.001 and r=0.162, P=0.096 respectively). In addition, ΔnT1 but not ΔECV correlated with an increase in LV end-diastolic volume index (LVEDVi) (r=0.268, P&lt;0.01 and r=0.113, P=0.285).

ALVR, defined as Δ&gt;20% inLVEDVi, occurred in 21 cases, despite optimal medical therapy. Subjects with ALVR showed greater ΔnT1 (13.2±44.1 vs −5.2±30.2 ms, P&lt;0.05) but no significant differences in ΔECV (1.27±2.77 vs 0.72±2.45%, P=0.401). Also, subjects with ALVR were more likely hypertensive (67 vs 33%, P&lt;0.05), had more segments with microvascular obstruction (2.1±2.2 vs 0.8±1.7, P&lt;0.01) and lower baseline EF (39.8±8.8 vs 44.6±9.6%, P&lt;0.05). Infarct size was not significantly larger in ALVR subjects (20.7±13.4 vs 17.5±13.0% LV mass, P=0.322). A multivariate analysis including all these factors, showed the extent of microvascular obstruction (ExpoB: 1.35 [1.05–1.73], P=0.019) and remote ΔnT1 (ExpoB: 1.02 [1.00–1.03], P=0.026) to be the independent predictors of ALVR.

Conclusions

The nT1 variation in remote non-infarcted myocardium and the extent of microvascular obstruction are superior to ECV changes and infarct size in predicting ALVR following STEMI.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Fundaciό La Maratό TV3 2015 30 31 32. Fondos FEDER

P1016Correlation between cardiac magnetic resonance-late gadolinium enhancement and electro-anatomical map for right atrium

Funding Acknowledgements

none

Background

 Electroanatomical map (EAM) detects areas of low voltage as a surrogated marker of fibrosis areas, being the reference technique for its detection. Cardiac magnetic resonance with Late Gadolinium enhancement (CMR-LGE) allows non-invasive detection of atrial fibrotic areas. CMR-LGE studies have focused on the left atrium since now.

Purpose

We need to validate this test to extend its use to the right atrium (RA), since it is involved in the arrhythmogenic substrate of several arrhythmias, and probably also in atrial fibrillation (AF).

Methods

 Prospective observational study. Fifteen patients undergoing a first AF ablation procedure were included. All patients had a pre-procedural LGE-CMR performed. The blood pool-normalized intensity signal (image intensity ratio-IIR) was calculated for the right atrial wall, and values projected in a shell. IIR values validated for the left atrium were used to identify dense and intermediate fibrosis, and healthy tissue (&gt;1.32, 1.2-1.32, &lt;1.2, respectively). During the procedure but before ablation, a point-by-point high density EA bipolar voltage map of RA was obtained with a multipolar catheter. Standard voltage thresholds of 0,1 mV and 0,5 mV were used to characterize fibrotic and healthy tissue in EAM. For each RA, the EAM was projected into the IIR shell, and the correlation between bipolar voltage and normalized IIR values for each shell point was quantified. Then, we also obtained its concordance (categorical variables) according to the label automatically assigned by EAM/CMR with the pre-set thresholds: healthy tissue/ intermediate fibrosis/dense fibrosis.

Results

 A total of 8,830 points were obtained, mean per patient 588 (± 509) points. A global weak negative correlation was found between the EA bipolar voltage map (EAM) and IIR (CMR) (r= -0.16, p &lt; 0.0001)(figure). LGE-CMR identified more healthy tissue than EAM (81.0% vs 60.6% respectively), then CMR underestimated the fibrotic tissue in RA. Finally, we analyzed the concordance and we obtained that the degree of accuracy between both measurements was 55.7%.

Conclusion

 There was an inverse correlation between the bipolar voltage EAM and IIR (CMR) of low grade but with statistical significance. CMR underestimated fibrotic tissue in RA with respect to its identification by EAM.

Abstract Figure. Correlation between bipolar voltage-IIR

P575Usefulness of late gadolinium enhancement cardiac magnetic resonance to predict appropriate therapies in implantable cardioverter defibrillator patients in primary prevention

Funding Acknowledgements

No funding acknowledgements

OnBehalf

VT and sudden cardiac death

Background

  The scar and the amount of border zone measured by late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) has been proposed as an independent predictor of ventricular arrhythmias in patients with ischemic and non-ischemic cardiomyopathy. However, at the present time, the guidelines are based only on the ejection fraction to recommend an implantable cardioverter defibrillator (ICD) in primary prevention, and only a minority of these patients receive appropriate therapies. So, prevention needs to be improved.

Purpose

To identify predictors of appropriate therapies in patients with a primary prevention ICD using cardiac magnetic resonance imaging and a dedicated software (ADAS-3D) to characterize the scar.

Methods

All consecutive patients who underwent a LGE-MR prior to ICD implantation in primary prevention were prospectively included.  Clinical and cardiac imaging characteristics were collected. The myocardium was segmented with ADAS-3D software in 10 layers (from endocardium to epicardium). The scar, border zone, core and conducting channels were automatically measured in grams by the software.

Results

Since 2008 to 2017, 206 patients were included. Mean age was 67 +/- 28 years, 80% men, mean ejection fraction 26%+/-9, 52% with ischemic cardiomyopathy and 48% non-ischemic. The primary endpoint was appropriate therapies and/or sudden cardiac death (SCD). Median follow-up was 46,33 months.  46 patients (22%) reached the primary endpoint. Greater scar mass  (36,05 grams vs 21,5 grams; HR 1.04; 95% CI (1.03-1-05), p &lt;0.001), core mass (9,8 grams vs 5,6 grams; HR 1.06; 95% CI (1.04-1-09), p &lt;0.001),  border zone mass (26,2 grams vs 15,9 grams; HR 1.05; 95% CI (1.04-1-09), p &lt;0.001) and channel mass (3,0  grams vs 1,6 grams; HR 1.15 95% CI (1.06-1.25), p &lt;0.001) were associated with appropriate therapies and SCD.  A border zone mass &gt;5.3 grams was independently associated with the primary endpoint (HR: 4.77; 95% CI (1.15-19.73), p = 0.03).

Conclusions

 The amount of border zone, core and channel mass measured by LGE-MR and ADAS software are independent predictors of appropriate therapies and SCD in patients with ICD in primary prevention.

Abstract Figure. Scar characterization

P1129Bipolar voltage cut-off validation in electroanatomical voltage mapping to identify scar and conduction channels in ventricular tachycardia ablation: need for new cut-off in NICM

Background/Introduction

Substrate-guided techniques have changed the approach and results of ventricular tachycardia (VT) ablation and electroanatomical voltage mapping (EAVM) constitutes a diagnostic and therapeutic cornerstone in this field. In current practice normal myocardium is typically characterized by bipolar voltage &gt; 1.5 mV, dense scar &lt; 0.5 mV, and border zone (BZ) tissue by the range between 0.5 to 1.5 mV. Of note, evidence for these cut-off values has been derived in humans from small observational studies and in animals. Furthermore, some studies suggest that only the 60% of not transmural endocardial scars and the 35% of not endocardial scars are detected without any adjustment of these values. New voltage cut-off values are needed.

Purpose

The purpose of this study is to adjust voltage cut off in order to establish the threshold that more accurately define the pathological substrate in VT ablation. Additionally, predictors of usefulness of current thresholds are analyzed.

Methods

EAVM were created with CARTO3 System and Sensor-Force catheter (Navistar Smart-Touch and Pentaray). We delineated the conducting channels by analyzing the late potentials activation. Based on these channels we looked for the best cut-off values to detect these channels. We describe the baseline characteristics, the best cut-off values for border zone and scar core in our series and we analyzed the accuracy of the current established values to detect the arrhythmogenic VT substrate

Results

We investigated 51 patients (74,5% males; 41,2% ischemic cardiomyopathy, mean LVEF 38,6% +/-13,6) with sustained monomorphic VT submitted to ablation during 2016 and 2017. The range of the voltage adjustment was from 0,01-1 mV for core area and 0,2-6mV as maximum, with an average of 0,31-1,42mV. Using currently accepted bipolar voltage cut-off &lt;0.5 mV the core scar was correctly identified in 80,4% of patients: 90,4% in ischemic and 73,3% in NICM. Regarding BZ, using classical cut off (0.5-1.5mV) only 56,9 % of the cases were well identified: interestingly, accuracy was worse in NICM (46,6%) than in ischemic patients (71,4%) (p = 0,07).

Conclusions EAVM is very important to detect scar and channels in VT ablation, but several elements can affect it and recently the traditional voltage values have been questioned. Our study suggests how the threshold as currently applied in daily practice could be acceptable to detect the core scar area, but it has to be reconsidered in NICM, especially regarding the border zone. An evident trend (p = 0,07) suggests a better accuracy of current values to define VT substrate in ischemic patients than in NICM.

Abstract Figure. Channel Identification

474 Isolated pulmonary endocarditis

INTRODUCTION

Isolated pulmonary endocarditis is a rare entity, especially in patients without predisposing factors, being its current incidence less than 1% of the total cases of infectious endocarditis. This is due to the lower right heart pressures and a decrease of intravenous drug-consum, being most of the cases nowadays, related to congenital right-heart diseases or pacemakers and defibrillators implants.

CLINICAL CASE

A 35 year-old man, tobacco smoker and intravenous cocaine consumer since he was 25, was admitted to our Emergency Department for fever up to 40ºC, cough and dyspnea started three days before admission. In the anamnesis he refereed intravenous consum of cocaine and sharing of syringes the last week. On physical examination he was tachycardic and signs of heart right failure were present such as jugular ingurgitation and peripheral edema. No murmurs were heard. No respiratory failure was detected at any time. Blood test analysis showed high levels of protein C reactive and leukocytosis. Blood cultures were positive for S. aureus (OXA-S) in the first 24h. Chest X-ray (image 1) showed a necrotizing bilateral pneumonia that was confirmed with the presence of cavitated images in the pulmonary CT (image 2). Antibiotic treatment was started with daptomicine + cloxaciline. With the suspicion of right endocarditis a transthoracic echocardiography was performed, showing the presence of a big vegetation (4x1cm) on the pulmonary valve that caused moderate pulmonary insufficiency (images 3, 4). Neither tricuspid nor left side valves were involved. Biventricular function was conserved and hyperdynamic. Endocarditis diagnosis was definitive and due to the presence of multiple right embolisms and the big size of the vegetation, the patient underwent cardiac surgery. Intra-surgical finding demonstrated a big vegetation of almost 5 cm (image 5) depending of the posterior pulmonary valve that was removed; the posterior valve needed to be repaired. Posterior clinical evolution was correct without complications, completing 17 days of i.v. antibiotics (cloxaciline) before discharge.

CONCLUSIONS

Right endocarditis is a rapidly progressive disease due to the fact that staphylococcus are the most frequent microorganisms involved. Valvular destruction and secondary embolic phenomena are the rule. Tricuspid valve is involved most of the times being the isolated pulmonary valve affection very uncommon.

Abstract 474 Figure. CT, Echo and surgical images

P3695Predicting adverse outcomes after TAVI procedure - a comparison of two CoreValve generations using real-life outcomes and patient-specific computer simulations

Background and aim

Post-procedure conduction abnormalities (CA) and paravalvular aortic regurgitation (PAR) continue to strain TAVI outcomes. Computer simulations, based on patient-specific anatomy, valve properties, and implantation position, have been validated for prediction of these complications. The new-generation CoreValve Evolut PRO has been shown to have lower levels of PAR and CA than previous generations. The aim was to compare clinical outcomes after Evolut Pro implantation in real-life with outcomes of virtual deployment of the same size, implantation depth adjusted CoreValve Evolut R.

Methods

Patients undergoing Evolut Pro implantation at a single centre were included into the study. Postoperative Doppler echocardiography was assessed to define PAR, the pre- and postoperative 12-lead ECGs for CA, and the postoperative angiograms to measure implantation depth based on annular plane distance from the non-coronary and left coronary aortic valve cusps. Preoperative multislice computed tomography was used to generate patient-specific models of the native aortic root. Implantation of the Evolut R valve and corresponding aortic root deformation was simulated using computational mechanics, whereas blood flow and level of PAR were predicted using computational fluid dynamics. Prediction of CA – new onset left bundle branch block or atrioventricular block type II or III -was based on calculations of contact pressure in a patient-specific region of the aortic root containing the AV conduction system (ROI). Outcomes were predicted in three implantation depth positions - high, medium, low – where the position closest to the real-life implantation depth was chosen for outcome comparisons.

Results

Study diagram is shown in Figure 1. Thirty-three patients (57% female, mean age 82±6 years old) underwent a TAVI intervention with an Evolut PRO valve. Evolut PRO implantation depths were, in general, closest to the lowest modeled Evolut R depth. Comparison demonstrated similar overall incidence of moderate-to-severe PAR. The Evolut R simulation predicted 18 patients without PAR and 2 with PAR. With the Evolute PRO, 1 of the 18 not predicted developed significant PAR, and 1 of the 2 predicted did not develop PAR. CA were notably higher with the Evolut R simulation, where CA were present in 9 out of 12 patients, as compared to the observed 5 out of 12 with the Evolut PRO.

Figure 1

Conclusion

Single-centre outcomes after Evolut Pro implantation in real-life showed a similar overall incidence of moderate-to-severe PAR and a lower incidence of conduction abnormalities as compared to the same size, implantation depth adjusted, patient-specific Evolut R modeled outcomes. As inferred from the results, computer simulations may have high clinical utility in supporting clinical decisions regarding valve choice in TAVI procedures.

Acknowledgement/Funding

Horizon 2020 European Commission Project H2020-MSCA-ITN-2016 (764738)

Clinique de la pédopornographie sur Internet

Résumé non reçu.

Ablation of frequent premature ventricular complex in an athlete

Premature ventricular complex are common findings in the exam of many athletes. There is no extensive scientific evidence in the management of this situation particularly when associated with borderline contractile function of the left ventricle. In this case report, we present a 35-year-old asymptomatic healthy athlete with high incidence (over 10,000 beats in 24 h) of premature ventricular complex and left ventricular dilatation with dysfunction, which persisted after a resting period of 6 months without training. We performed radiofrequency ablation of the premature ventricular complex focus. After 1-year follow-up, he was asymptomatic without arrhythmia and the left ventricle normalized its size and function as shown by echocardiogram and cardiac magnetic resonance.

Sudden death due to cerebral malaria: a case report

Malaria is generally diagnosed ante-mortem. Few post-mortem cases have been described in the literature. Post-mortem cases may present as sudden and unexpected deaths of young individuals rising suspicious of unnatural death, and may therefore be investigated by medical examiners. We present the case of a 24-year-old man who died a few days after returning from a trip to Mali (Africa). Death was attributed to cerebral malaria after a thorough post-mortem investigation. The pathological aspects underlying the fatal outcome are discussed.

Proximal Femoral Nail Antirotation versus Gamma3 nail for intramedullary nailing of unstable trochanteric fractures. A randomised comparative study

The purpose of this study was to compare the clinical results and the complication rates of a new generation of two intramedullary fixation devices: Proximal Femoral Nail Antirotation® (PFNA) and Gamma3®. We conducted a prospective randomised multicentre trial of 61 patients who underwent a PFNA fixation treatment (31 patients) or a Gamma3 nail (30 patients). We documented the fixation failure complications as well as data of the surgical procedure, the clinical and functional outcomes (the EuroQoL5 questionnaire, the Katz index score, the Short Form 36 (SF-36), and the Harris Hip Score) and the plain radiographic parameters at 3,6 and 12 months follow up. The PFNA and Gamma3 fixation devices were similar in terms of complication rates. The risk for experiencing a postoperative complication after Gamma3 nailing was 40% versus 45% after PFNA fixation. At the 6-month and 1-year follow-up evaluations, there were no significant differences in terms of range of motion, clinical scores and radiological outcomes.

Characteristics of French users of child pornography: description of a cohort subjected to forensic evaluation

Child pornography is a form of sexual exploitation of children. The virtual aspect of this offence appears to be encouraged by the internet. It is important to know the profiles of the people downloading these images. The aim of our study was to identify the characteristics of people who are drawn to child pornography. Our study was based on psychiatric assessments carried out at the request of the law courts. The feeling of loneliness and poor social integration are evoked by a lot of users of child pornography. Generally, they have no criminal record.

[Evaluation of the results of the treatment of Vancouver B1 periprosthetic fractures and proposed indications for the use of cortical allograft as part of the fixation]

Currently there is limited information on the indications for the use of cortical allograft for the treatment of periprosthetic fractures on a stable stem. The purpose of this study was to retrospectively evaluate the treatment and the results obtained in this type of fractures and propose a series of criteria for the use of cortical allograft. Between 2003 and 2008 a total of 31 periprosthetic femur fractures were treated at our institution. Twelve of them were classified as B1: 6 were treated with a Dall-Miles (Stryker) system plate and 6 with the same plate supplemented with a structural cortical allograft over the medial cortex of the femur (DM and DM-Allo groups, respectively). An evaluation of the clinical and radiologic results was performed in the latest follow-up available. A patient in the DM-Allo group had rupture of a screw and 10 degrees varization; the fracture healed despite this and the patient had a satisfactory clinical course. The Oxford Hip Score was 9 points lower in the DM group compared with the DM-Allo group, and the EQ-5D health scale was 0.10 better for the DM group. The DM-Allo group had a longer hospital stay and more transfusion-related requirements. We think that the patients with clinical or radiologic criteria of osteoporotic bone may benefit from the use of a cortical allograft to favor healing and increase the bone stock. However, those advantages should be weighed considering the higher risk of surgical-related morbidity associated with the surgical insult.

Abscisic acid is involved in the wound-induced expression of the proteinase inhibitor II gene in potato and tomato

Plants respond to wounding or pathogen attack by a variety of biochemical reactions, involving in some instances gene activation in tissues far apart from the actual site of wounding or pathogen invasion. One of the best analyzed examples for such a systemic reaction is the wound-induced expression of proteinase inhibitor genes in tomato and potato leaves. Local wounding of potato or tomato plants results in the accumulation of proteinase inhibitors I and II throughout the aerial part of the plant. In contrast to wild-type plants, abscisic acid-deficient mutants of potato (droopy) and tomato (sit) show a drastically reduced induction of these genes in response to plant wounding. High levels of proteinase inhibitor II gene expression are obtained in mutant and wild-type plants upon exogenous application of abscisic acid. Measurements of the endogenous abscisic acid levels in wild-type plants show that wounding results in increased levels of this phytohormone in wounded and nonwounded systemically induced leaves. Thus these results show that the plant hormone abscisic acid is involved in the wound-induced activation of the proteinase inhibitor II gene. Furthermore, they are compatible with a model assuming this hormone to be the actual mediator of the systemic wound response.

[Spinal tuberculosis: early surgical treatment combined with medical treatment]

BACKGROUND

Spinal tuberculosis can produce kyphosis with neurologicaldeficit, despite antibiotic treatment. When there is no response to medical treatment, the recommended procedure is debridementand interbody fusion with bone autograft. The biological characteristicsof Mycobacterium tuberculosis do not prevent osteosynthesisof the infected bone from being performed.

PATIENTS AND METHOD

Five patients with spinal tuberculosis and neurological deficitunderwent debridement, interbody fusion and anterior osteosynthesisin addition to medical treatment. In order to ensure stability, posterior fusion was also performed in three patients. All 5 patientsdisplayed weakness and paralysis of their lower extremities, two patients suffered an L4 radiculopathy, one developed paraparesiaand one was excluded due to a short follow-up. Mean value of vertebralkyphosis was 22,8 degrees and mean follow-up was 3,1 years.

RESULTS

No patient had septic loosening or progression of the disease. Correction of kyphosis was 104,5% postoperatively and 80,5% atthe end of follow-up. All patients, apart from one with an L4radiculopathy, exhibited neurological recovery.

CONCLUSIONS

Anterior instrumentation allows spinal decompression, septic focusdebridement, deformity correction and autologous bone grafting. In severe kyphotic flattening, it is advisable to associate alimited posterior arthrodesis. When pathological fractures appearor there is no response to antibiotic treatment, the combinationof medical and surgical treatment improves patients' outcome.

Gibberellins signal nuclear import of PHOR1, a photoperiod-responsive protein with homology to Drosophila armadillo

S. tuberosum ssp. andigena potato plants require short days (SD) for tuberization. We have isolated PHOR1 (photoperiod-responsive 1), which shows upregulated expression in induced leaves (SD). PHOR1 encodes an arm repeat protein with homology to the Drosophila segment polarity protein armadillo. Antisense inhibition of PHOR1 produces a semidwarf phenotype similar to that of GA-deficient plants, and the antisense lines show reduced GA responsiveness combined with a higher endogenous GA content than wild-type plants. Feedback regulation of GA biosynthetic genes is also altered in these lines. Conversely, transgenic lines overexpressing PHOR1 show an enhanced response to GA. GA application induces rapid migration of PHOR1-GFP protein to the nucleus. Thus, PHOR1 appears to be a general component of GA signaling pathways that relocalizes to the nucleus in the presence of GA.

A rapeseed-specific gene, acetyl-CoA carboxylase, can be used as a reference for qualitative and real-time quantitative PCR detection of transgenes from mixed food samples

Polymerase chain reaction (PCR) methods are very useful techniques for the detection and quantification of genetically modified organisms (GMOs) in food samples. These methods rely on the amplification of transgenic sequences and quantification of the transgenic DNA by comparison to an amplified reference gene. Reported here is the development of specific primers for the rapeseed (Brassica napus) BnACCg8 gene and PCR cycling conditions suitable for the use of this sequence as an endogenous reference gene in both qualitative and quantitative PCR assays. Both methods were assayed with 20 different rapeseed varieties, and identical amplification products were obtained with all of them. No amplification products were observed when DNA samples from other Brassica species, Arabidopsis thaliana, maize, and soybean were used as templates, which demonstrates that this system is specific for rapeseed. In real-time quantitative PCR analysis, the detection limit was as low as 1.25 pg of DNA, which indicates that this method is suitable for use in processed food samples which contain very low copies of target DNA.

[Phage typing of Salmonella enteritidis isolated from clinical, food, and poultry samples in Chile]

Since 1994 an extensive epidemic of infections with Salmonella enteritidis (S. enteritidis) has affected Chile. In order to understand the diversity of infective sources, the possible origin of the epidemic, and the epidemiological relationships between clinical, food, and poultry isolates, we carried out phage typing of three groups of samples: 1) 310 S. enteritidis clinical samples collected between 1975 and 1996, 2) 47 food isolates obtained during S. enteritidis outbreaks, and 3) 27 strains isolated in surveillance studies of poultry-raising establishments. With the clinical samples, a total of 13 phage types were identified, 2 isolates could not be typed, and 1 was considered atypical. The phage types that were identified most frequently were 1 (56.8%) and 4 (31.3%), trailed by type 8 (4.8%) and type 28 (1.9%). Over time and in different regions of the country there were major changes in the distribution of the phage types. In the first years of collection the only phage types registered were 8 and 28, which disappeared around 1980 and then began reappearing sporadically in 1996. With the gradual S. enteritidis expansion that started in 1988, in the central and southern areas of the country phage type 4 began to appear; that type had not been found before in Chile. In 1991 in the northern area of the country phage type 1 began to predominate; it was another type that had not been reported before in Chile. In the food isolates the only phage types identified were 1 and 4, which were also the most common in the poultry isolates. Phage typing of S. enteritidis has proved to be useful in guiding the epidemiological analysis of the infections caused by this pathogen.

[Detection of Salmonella enteritidis in samples of poultry products for human consumption in the Chilean metropolitan area]

BACKGROUND

Salmonella enteritidis (SE) is a frequent cause of diarrhea, and is transmitted mainly by SE contaminated eggs or poultry meat. The frequency of SE contaminated eggs or chicken meat and the risk for acquiring this pathogen is unknown in Chile.

AIM

To measure SE contamination in eggs poultry meat and entrails offered in retail markets in the Metropolitan Area during two consecutive years (1998-1999).

MATERIAL AND METHODS

Samples were placed in sterile bags and transported to the laboratory before 4 hours at 4 degrees C. Microbiologic detection was done using a standard procedure and an immunodetection assay.

RESULTS

SE was found in one of 1081 egg samples (0.09%). The contaminated sample was offered in a supermarket under their own commercial name. Six percent of 1154 poultry meat samples were contaminated by SE and 2.3% by other Salmonella serotypes. Entrails had even higher rates with 10.2% of 370 samples harboring SE and 2.7% other serotypes. Total Salmonella sp. isolates and SE isolates declined during 1999. Nine SE phagotypes were identified, predominating types 4 and 7.

CONCLUSIONS

Eggs and other avian products are contaminated by different SE phagotypes and other Salmonella serotypes, implicating a risk for the consumers (Rev Méd Chile 2000; 128: 1075-83).

Regulation of transcript levels of a potato gibberellin 20-oxidase gene by light and phytochrome B

Up to three gibberellin (GA) 20-oxidase genes have now been cloned from several species including Arabidopsis, bean (Phaseolus vulgaris), and potato (Solanum tuberosum). In each case the GA 20-oxidase genes exhibit different patterns of tissue expression. We have performed extensive northern analysis on one of the potato GA 20-oxidase genes (StGA20ox1), which is the only one that shows significant transcript levels in leaves. We show that levels of StGA20ox1 transcript are elevated in transgenic antisense plants that have reduced levels of phytochrome B (PHYB) compared with wild-type plants, implicating PHYB in the control of GA biosynthesis. We show that StGA20ox1 transcript levels vary in leaves of different age throughout the plant and cycle throughout the day, furthermore they are up-regulated by light and down-regulated in the dark. The degree of the response to the light-on signal is similar in potato plants deficient in phytochrome A or PHYB and wild-type plants. The induction of StGA20ox1 by blue light raises the possibility that a blue light receptor may be involved in the control of this gene by light.

Changes in GA 20-oxidase gene expression strongly affect stem length, tuber induction and tuber yield of potato plants

Gene StGA20ox1 encoding potato GA 20-oxidase is expressed to relatively high levels in leaves and regulated by daylength. To investigate whether this gene is involved in photoperiodic regulation of tuber formation, we have obtained transgenic potato plants expressing sense and antisense copies of the StGA20ox1 cDNA. Over-expression of this cDNA resulted in taller plants that required a longer duration of a short day photoperiod (SD) to tuberize. Tubers from these plants had a decreased time of dormancy and developed sprouts with elongated internodes. Plants expressing antisense copies of the StGA20ox1 cDNA had shorter stems, a decreased length of the internodes and tuberized earlier than control plants, showing increased tuber yields. Antisense inhibition of this gene had no visible effect on the time of dormancy of the tubers, although at the end of dormancy these formed sprouts with shortened internodes. Decreased levels of endogenous GA20 and GA1 were detected in the apex and first leaves of the antisense lines. These results demonstrate the involvement of the GA 20-oxidase activity encoded by StGA20ox1 in the control of stem elongation and in tuber induction but not in tuber dormancy, indicating that the latter may be regulated by another member of the gene family.

Leaf C40.4: a carotenoid-associated protein involved in the modulation of photosynthetic efficiency?

Comparative analysis by differential RNA display (DDRT-PCR) of the expression patterns of potato plants induced and non-induced to tuberize, led to the isolation of a cDNA clone, C40.4, that is strongly upregulated in the leaves of tuberizing plants. Leaf expression of this transcript was shown to be light-dependent, with increased levels of mRNA and protein being detected during the light hours. Sequence analysis revealed near complete identity to potato CDSP34, a thylakoid protein induced by drought stress, and strong homology to the carotenoid-associated proteins fibrillin, ChrB and PAP from pepper fruit, and CHRC from cucumber flowers. By using an antibody against pepper fibrillin, we were able to demonstrate a chloroplastic location of the C40.4 protein in association with the thylakoid membranes. Two-dimensional analysis of thylakoid pigment-protein complexes showed a specific association of the protein with the photosystem II (PSII) multi-subunit complex. Antisense plants with reduced levels of accumulation of C40.4 showed a stunted growth and decreased tuber yield and exhibited reduced values of non-photochemical quenching of chlorophyll a fluorescence. Altogether, these results indicate a preferential association of the C40.4 protein with the light harvesting complex of photosystem II (LHCII) antenna pigment complexes, and suggest a functional role of this protein in photosynthesis, by modulating photosynthetic efficiency and dissipation of excess absorbed light energy within the antenna complex.

Feedback control and diurnal regulation of gibberellin 20-oxidase transcript levels in potato

Tuber formation in potato (Solanum tuberosum) is promoted by short photoperiods and is inhibited by gibberellins (GAs). Endogenous levels of GA1 were shown to decrease in stolons and leaves of potato plants induced to tuberize, which suggests that photoperiodic regulation of GA biosynthesis may play a role in tuber induction. We report the isolation of three potato cDNA clones (StGA20ox1-3) encoding GA 20-oxidase, a key regulatory enzyme in the GA-biosynthetic pathway. Using northern analysis, we detected a differential pattern of tissue-specific expression of the mRNAs corresponding to these clones. StGA20ox mRNAs were also very abundant in leaves of the potato ga1 mutant, which is blocked in the 13-hydroxylation step, and were strongly down-regulated by gibberellic acid, suggesting a feedback regulation of these genes. In plants grown in short-day (inductive) conditions, levels of the StGA20ox transcripts in leaves fluctuated during a 24-h period, with a peak of accumulation observed about 4 h after the lights were turned off. Interruption of the night with a 30-min "night break" of light (noninductive conditions) did not have a marked effect on the levels of accumulation of the three GA 20-oxidase mRNAs during the day, but it induced a second peak of expression of StGA20ox1 and StGA20ox3 transcripts late in the night. This observation, together with the finding that StGA20ox1 mRNA is expressed at high levels in leaves, suggests that night-break induction of this gene might play a role in the control of tuberization by regulating endogenous levels of GAs in response to daylength conditions.

Characterization of the wound-induced metallocarboxypeptidase inhibitor from potato. cDNA sequence, induction of gene expression, subcellular immunolocalization and potential roles of the C-terminal propeptide

A partial cDNA clone for the potato wound-inducible metallocarboxypeptidase inhibitor (PCI) was isolated from a cDNA library constructed from mRNA of abscisic acid (ABA)-treated potato leaves. The full 5' region of the cDNA was obtained through a RACE-PCR protocol. PCI mRNA encodes a precursor polypeptide which comprises a 29 residue N-terminal signal peptide, a 27 residue N-terminal pro-region, the 39 residue mature PCI protein, and a 7 residue C-terminal extension. Northern blot analysis demonstrates that the PCI gene is transcriptionally activated by wounding, and wound signaling can be induced by ABA and jasmonic acid. Subcellular localization of the protein was investigated by immunocytochemistry and electron microscopy, showing that PCI accumulates within the vacuole. A partial PCI precursor form, comprising the mature protein and the C-terminal extension, has been expressed in Escherichia coli and characterized. Its inability to inhibit carboxypeptidases, and stability to carboxypeptidase digestion, suggest that the C-terminal pro-domain may have, besides a probable vacuolar sorting function, a role in modulation of the inhibitory activity of PCI.

Highly heterogeneous families of Ty1/copia retrotransposons in the Lycopersicon chilense genome

We have used the degenerated oligonucleotide primers-PCR (DOP-PCR) technique to determine the presence of Ty1/copia-related retrotransposons in the wild species of tomato, Lycopersicon chilense. Using degenerated oligonucleotides corresponding to highly conserved domains in the Ty1/copia retrotransposons, fragments of roughly 300 bp were obtained by PCR amplification. These were cloned in a plasmid vector and the nucleotide sequence determined for 20 clones, 19 of which showed sequence homology to retrotransposon-related sequences. Comparison of the deduced amino-acid sequence of these clones with those reported for other retrotransposons has allowed their classification into four distinct families: TLC1-TLC4. The level of amino-acid sequence similarity between these elements extends from 66.7% (between TLC1 and TLC2) to 42.6% (between TLC2 and TLC3). Altogether, the four families comprise about 0.17% of the L. chilense genome. RT-PCR analysis shows that the four TLC families are transcriptionally active, suggesting a mechanism for the generation of the observed diversity between the L. chilense retrotransposons.

Expression of the Arabidopsis abi1-1 mutant allele inhibits proteinase inhibitor wound-induction in tomato

Abscisic acid (ABA) is an essential component in the wound signalling cascade. Increased levels of endogenous ABA were observed after wounding and shown to be a requisite for wound-induced expression of the proteinase inhibitor II genes. We have taken advantage of the dominant character of the Arabidopsis abi1-1 mutation, to investigate whether ABl1 has a function in ABA signalling in response to wounding. Transgenic tomato plants carrying copies of either the wild-type ABI1 or the mutant abi1-1 alleles were obtained and assayed for wound-induction of the pin2 or LAP genes. While normal levels of gene induction were observed in the transgenic ABI1 plants, the abi1-1 transformants displayed a severe wilty phenotype and reduced seed dormancy. Expression of the abi1-1 dominant mutation blocked accumulation of the drought-induced TAS14 and LE25 mRNAs in response to ABA, as well as ABA- and wound-induced expression of the defense-associated pin2 and LAP transcripts. MeJA-induction of the pin2 and LAP mRNAs, on the contrary, was not affected in the abi1-1 transformants. These results indicate that abi1-1 inhibits wound-induced expression of the pin2 and LAP transcripts by blocking ABA-induction of these genes. This implicates ABI1 in wound-signalling and suggests that a common early ABA signalling pathway may function in the responses to wounding and water stress.

Phytochrome B affects the levels of a graft-transmissible signal involved in tuberization

Grafting experiments between phytochrome B antisense and wild-type potato (Solanum tuberosum L. subsp. andigena [line 7540]) plants provide evidence that phytochrome B is involved in the production of a graft-transmissible inhibitor of tuberization, the level of which is reduced in the antisense plants, allowing them to tuberize in noninducing photoperiods.

A -308 deletion of the tomato LAP promoters is able to direct flower-specific and MeJA-induced expression in transgenic plants

Tomato and potato leucine aminopeptidase (LAP) mRNAs are induced in response to mechanical wounding and the wound signal molecules, ABA and jasmonic acid. Here, we report the isolation of two LAP genes, LAP17.1A and LAP17.2, from tomato. Functional analysis in transgenic tomato and potato plants show that fusions of the corresponding 5' non-coding regions to the gusA gene are constitutively expressed in flowers and induced in leaves upon wounding or by treatment with methyl jasmonate (MeJA). Comparison of the 5' non-coding regions of the two genes revealed a region from -317 to -3 relative to the ATG, which is strongly conserved in both promoters. This 0.3 kb proximal promoter fragment is sufficient to direct flower-specific and MeJA-inducible GUS activity in transgenic potato plants, and thus contains a MeJA-responsive element that mediates induction by MeJA. Dimeric TGACG motifs or G-box elements similar to those found in other MeJA-inducible genes are not observed in this region, which suggests that a different DNA sequence is involved in MeJA induction of the LAP genes.