Systematic review finds risk of bias and applicability concerns for models predicting central line-associated bloodstream infection

OBJECTIVES

To systematically review the risk of bias and applicability of published prediction models for risk of central line-associated bloodstream infection (CLA-BSI) in hospitalized patients.

STUDY DESIGN AND SETTING

Systematic review of literature in PubMed, Embase, Web of Science Core Collection, and Scopus up to July 10, 2023. Two authors independently appraised risk models using CHecklist for critical Appraisal and data extraction for systematic Reviews of prediction Modelling Studies (CHARMS) and assessed their risk of bias and applicability using Prediction model Risk Of Bias ASsessment Tool (PROBAST).

RESULTS

Sixteen studies were included, describing 37 models. When studies presented multiple algorithms, we focused on the model that was selected as the best by the study authors. Eventually we appraised 19 models, among which 15 were regression models and four machine learning models. All models were at a high risk of bias, primarily due to inappropriate proxy outcomes, predictors that are unavailable at prediction time in clinical practice, inadequate sample size, negligence of missing data, lack of model validation, and absence of calibration assessment. 18 out of 19 models had a high concern for applicability, one model had unclear concern for applicability due to incomplete reporting.

CONCLUSION

We did not identify a prediction model of potential clinical use. There is a pressing need to develop an applicable model for CLA-BSI.

The Left Ventricular Pressure-Volume Area and Stroke Work in Porcine Model of Ascending Compared to Descending Thoracic Aorta Stenosis Creating a Chronic Early Vs. Late Left Ventricular Afterload Increase

Objective: Left ventricular hypertrophy in aortic stenosis, arterial hypertension or coarctation of the aorta is risk factor for early development of HF. In chronic late compared to early left ventricular afterload increases resulting from descending thoracic оr ascending aorta stenosis, we assess the left ventricular stroke work, pressure-volume area for О2 demand and effective work on the 4th and 8th weeks. It is suggested that reduced proximal thoracic aortic compliance presents with myocardial ischemia. However, development of adverse left ventricular hypertrophic remodeling and HF in different peak of LV afterload increase is understood poorly. Methods: Fourteen domestic male pigs (28 ± 3 kg) underwent descending thoracic or ascending aortic stenosis through posterior lateral thoracotomy, with cMRI and an invasive left ventricular pressure-volume loops' аrea assessment (Millar 5Fr pig-tailed conductance catheter) on the 4th and 8th weeks. Left ventricular stroke work and pressure-volume area PVA, parameter for LV O2 demand, were assessed in hypertrophic left ventricular remodeling, resulting from different peaks in LV afterload (late vs. early LV afterload) increase and we thus defined early adverse LV hypertrophic remodeling in linear and nonlinear end-systolic pressure-volume regression analysis. For this we used special software. Data was compared with two-way repeated measures ANOVA. Results presented are means ± (SEM) or medians and significance is set at p < 0.05. Results: The left ventricular nonlinear PVA was not different, in LL compared to EL on the 8th week and when using the linear regression analysis. Stroke work was not different. The linear and nonlinear potential energy were not different between LL vs. the EL group. Nonlinear bLVO2 demand was not different, being higher in LL compared to EL in the 8th week. Indexed PVA parameters were not different or changed between the 4th and 8th weeks, when being normalized for body surface-area (m²) or 100 grams of LV mass. Conclusion: The left ventricular potential energy, PVA with effective work and LVO2 demands are not different in hypertrophic LV remodeling in LL vs. EL group at the 8th week. Difference is not present when end-systolic pressure-volume relation is assessed from indexed LV volumes for m² BSA or 100 grams of LV mass. EL is as important as LL in increased LV afterloads based on LV work and mechanical coupling in this hypertensive heart failure model having preserved EF.

Prolonged Asynchronous Left Ventricular Isovolumic Relaxation Constant in Ascending Compared to Descending Thoracic Aortic Stenosis for Chronic Early Left Ventricular Afterload and Late Left Ventricular Afterload Increase

Background: In arterial hypertension, left ventricular relaxation is affected early on in relation to a chronic difference in peak left ventricular afterload with early development of HF. Objective: in ascending compares to descending thoracic aortic stenosis, resulting in chronic late and early LV afterload increase, to assess the left ventricular isovolumic relaxation pressure decay constant through regression analysis, a parameter of left ventricular relaxation on the 4th and 8th week period from invasive left ventricular pressure measurements. Methods: fourteen pigs underwent posterolateral thoracotomy for ascending aortic stenosis, resulting in chronic early left ventricular afterload increase (EL = 6], or descending thoracic aortic stenosis creating chronic late systolic left ventricular load (LL = 8]. Exponential regression with nonzero asymptote for τ assessment, with linear and nonlinear regression were performed on isovolumic relaxation pressure decay from the left ventricular invasive pressure measurements on 4th and 8th week. Two-way repeated measurement ANOVA, post-hoc Tukey test and linear regression were performed for statistical analysis. Results presented are mean ± SEM or median (quartiles], with significance is at p < 0.05. Results: The ascending aortic stenosis associated with prolonged biexponential asynchronous τ, compared to the descending thoracic aorta stenosis, resulted in data that were different at the 8^th week in presence of respirations (interaction p < 0.05]. Monoexponential and linear τ were not different in either respiration being preserved or suspended transitionally and in preload reduction. Preload sensitive response of τ was found in ascending compared to descending thoracic aortic banding that reduced in EL and in LL it increased with load reduction (p < 0.05]. These results indicated that τ is not different in and between LV afterloading conditions in a chronic setting, although it indicates that myocardial ischemia is present and that it is greater in ascending aortic banding, compared to descending thoracic aorta banding at the 8th week. Conclusion: In different sequence of the left ventricular afterload, ventricular relaxation is affected early on, having in EL compared to LL prolonged biexponential asynchronous left ventricular relaxation constant, thus indicating the development left ventricular myocardial ischemia and different elastic recoil in an invasive left ventricular hemodynamic assessment.

Assessment of left ventricular function in horses with aortic regurgitation by 2D speckle tracking

Background

Aortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis.

Results

Radial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 ± 24.3%, SC 19.3 ± 3.2%) but not in horses with severe AR (SR 65.5 ± 26.2%, SC 16.3 ± 3.5%), compared to control horses (SR 54.5 ± 18.0%, SC 16.8 ± 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 ± 4.1 cm) and severe AR (DL 32.4 ± 6.1 cm) compared to control horses (DL 25.7 ± 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 ± 0.18/s) compared to controls (1.13 ± 0.13/s).

Conclusions

2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.

Experimental validation of the prestretch-strain relationship as a non-invasive index of left ventricular myocardial contractility

Background

The slope of the relationship between segmental PreS and total systolic shortening (S) has been proposed as a non-invasive index of left ventricular contractility. The aim of this study was to correlate this novel parameter to invasive gold standard measurements of contractility and to investigate how it is influenced by afterload.

Methods

In domestic pigs, afterload was increased by either balloon inflation in the aorta or by administration of phenylephrine while contractility was increased by dobutamine infusion. During all interventions, left ventricular pressure-volume measurements and trans-diaphragmatic two-dimensional echocardiographic images were acquired. The PreS-S slope was constructed from 18 segmental strain curves obtained by speckle tracking analysis and compared to the slope of the end systolic PV relationship (E_max) and the pre-load recruitable stroke work (PRSW).

Results

Sixteen datasets of increased contractility and afterload were analyzed. During dobutamine infusion, the LV volumes decreased (p<0.05) while ejection fraction increased (p<0.05). Emax, PRSW and the slope of the intra-ventricular PreS-S relation increased significantly during dobutamine infusion. Afterload increase led to increase in systolic blood pressure (105±16mmHg vs. 138±25mmHg; p<0.01) and decrease of LV stroke volume and ejection fraction (p<0.01). The PreS-S slope was not influenced by loading conditions in concordance with the PRSW findings. The absolute values of the PreS-S slope did not correlate with Emax or PRSW. However, the change of the PreS-S slope in relation with different interventions demonstrated good correlation with changes in PRSW or Emax, (r = 0.66, p<0.05 and r = 0.69, p<0.05).

Conclusions

The slope of the PreS-S relationship is sensitive to changes in inotropy and is less load-dependent than conventional non-invasive parameters of left ventricular function. The magnitude of the change of this slope correlates well with changes in invasive contractility measurements making it an attractive parameter to assess contractile reserve or contractile changes during longitudinal follow-up of patients.

P1609Adverse left ventricular remodeling in descending thoracic vs ascending aorta banding in novel porcin model. cMRI study

Background

Based on differences in the timing of left ventricular (LV) peak systolic pressure, distinction between early from late LV systolic loading is made. Reduced ascending aortic compliance results with chronic early LV systolic loading. Chronic late LV systolic loading associates with end-systolic wave refection's and developing earlier heart failure. The LV remodeling in chronic late vs early systolic loading has not been studied previously in a porcine model.

Objective

To develop novel porcin model and to study the LV hypertrophic remodeling in chronic late vs early LV systolic loading, during thoracic aorta banding.

Methods

Domestic male pigs (28±3.4kg, n=14) underwent thoracic aorta banding. Ascending aorta banding (PB, n=6) induced chronic early LV systolic loading. Descending thoracic aorta banding (DB n=8) provoked chronic late LV systolic loading. 3T cMRI with T1 mapping was performed at baseline, 4 and 8 weeks. Hemodynamic measurements were obtained using 5Fr Millar P-V catheter in LabChart, after 4 and 8 weeks. ANOVA two-way for repeated measurements was performed (R studio 3.5.1). Leven and Shapiro-Wilk normality testing was done. Analysis of variance of aligned rank transformed data was performed. Linear regression showed correlation between relevant parameters.

Results

Hemodynamic measurements are presented as means±se and means±sd for cMRI, for significant p<0.05. After 8 weeks of thoracic aorta banding, the timing of peak systolic LV pressure was prolonged in DB (PB 159±6 msec; DB 329±16 msec; p<0.01), correlating with LV dPdtmax (p=0.017, r=−0.8), Ea (p=0.04, r=0.73), LVEF (p=0.035, r=−0.74) and native T1 (p=0.01, r=−0.83) in DB. Tau was not different (p=0.8), correlated with the timing of peak LV pressure in DB (p=0.015, r=0.81). The gradients were not different (PB 25±5mmHg; DB 16±1mmHg; p=0.88) and LV systolic pressure (p=0.61). The isovolumic contraction phase was prolonged in DB (PB 34±4msec; DB 56±4msec, p<0.01). LV mass index increased (p=0.013) and was not different between the groups (PB 95±14g/m2; DB 89±12g/m2; p=0.89). RWT was different within (p<0.01) and between the groups (p=0.02),correlating with LVEFas dPdtmax (p=0.013, r=−0.82), whilst with dPdtmin (p=0.018, r=0.8) in DB. There was an interaction for site of aortic constriction and LV remodeling (RWT 0.067±0.08 in PB; 0.45±0.04 in DB, p=0.004; posterior LV wall thickness (PWT) p=0.012). RWT correlated with native T1 in PB (p=0.04) and DB (p<0.01, r=−0.8).

Des. aorta banding in late LV loadining

Conclusion

The LV hypertrophic remodeling, defined by RWT, PWT and hemodynamic correlates is different between chronic late and early LV systolic loading, in this novel porcine model. The timing of peak LV afterload associates with increased LV afterload and adverse LV remodeling in presence of chronic late LV systolic loading, in the porcin model of descending thoracic aorta banding. Increased RWT ratio associates with adverse LV remodeling in the porcine model of descending thoracic aortic constriction.

P606High intermodality variability in ejection fraction measured by echocardiography, cardiac magnetic resonance and single photon emission computed tomography in chronic coronary artery disease patients

Background

Clinical treatment strategies are often based on measurement of left ventricular ejection fraction (LVEF). There is limited evidence about variations in LVEF when measured by different imaging modalities.

Purpose

To investigate the intermodality variability of LVEF measured by two-dimensional echocardiography (2DE), three-dimensional echocardiography (3DE), cardiac magnetic resonance (CMR), and single photon emission computed tomography (SPECT) in patients with chronic coronary artery disease (CAD).

Methods

Patients from a multicenter study (DOPPLER-CIP – Determining optimal noninvasive parameters for the prediction of left ventricular remodeling in chronic ischemic patients) with chronic CAD were included. LVEF was measured by CMR and at least one additional modality. In each modality, LVEF was measured by a core laboratory independently of the other modalities. Measurements of LVEF by CMR were compared to 2DE, 3DE and SPECT using correlation and Bland-Altman plots.

Results

A total of 343 patients were included. Mean age was 63.9±8.3 years and 253 (74%) were males. Mean LVEF by CMR was 61.8±11.6%. Correlations between CMR LVEF and other modalities were moderate for 2DE and 3DE, and good for SPECT (Figure A-C). CMR had significantly greater correlation to SPECT, compared to 2DE and 3DE. Bland-Altman plots indicated relatively wide limits of agreement between all modalities, ranging from 31% to 42% (Figure, D-F). Mean absolute difference of LVEF between CMR and other modalities were 8.5% for 2DE, 9.0% for 3DE, and 8.3% for SPECT. The percentage of measurements that fell within a range of 5% difference compared to CMR LVEF was 41% for 2DE, 34% for 3DE and 37% for SPECT (all p>0.05).

Conclusions

In a multicenter study with chronic CAD patients, LVEF assessed by CMR had better correlation to SPECT, compared to 2DE and 3DE. However, there was considerable variability among all three modalities that were compared to CMR. Awareness of these variations are important in clinical management.

Standardised mortality ratios as a user-friendly performance metric and trigger for quality improvement in a Flemish hospital network: multicentre retrospective study

OBJECTIVE

To illustrate the development and use of standardised mortality rates (SMRs) as a trigger for quality improvement in a network of 27 hospitals.

DESIGN

This research was a retrospective observational study. The primary outcome was in-hospital mortality. SMRs were calculated for All Patient Refined-Diagnosis-Related Groups (APR-DRGs) that reflect 80% of the Flemish hospital network mortality. Hospital mortality was modelled using logistic regression. The metrics were communicated to the member hospitals using a custom-made R-Shiny web application showing results at the level of the hospital, patient groups and individual patients. Experiences with the metric and strategies for improvement were shared in chief medical officer meetings organised by the Flemish hospital network.

SETTING

27 Belgian hospitals.

PARTICIPANTS

1 198 717 hospital admissions for registration years 2009-2016.

RESULTS

Patient gender, age, comorbidity as well as admission source and type were important predictors of mortality. Altogether the SMR models had a C-statistic of 88%, indicating good discriminatory capability. Seven out of ten APR-DRGs with the highest percentage of hospitals statistically significantly deviating from the benchmark involved malignancy. The custom-built web application and the trusted environment of the Flemish hospital network created an interoperable strategy to get to work with SMR findings. Use of the web application increased over time, with peaks before and after key discussion meetings within the Flemish hospital network. A concomitant reduction in crude mortality for the selected APR-DRGs from 6.7% in 2009 to 5.9% in 2016 was observed.

CONCLUSIONS

This study reported on the phased approach for introducing SMR reporting to trigger quality improvement. Prerequisites for the successful use of quality metrics in hospital benchmarks are a collaborative approach based on trust among the participants and a reporting platform that allows stakeholders to interpret and analyse the results at multiple levels.

Cardiac Troponin T Concentrations, Reversible Myocardial Ischemia, and Indices of Left Ventricular Remodeling in Patients with Suspected Stable Angina Pectoris: a DOPPLER-CIP Substudy

BACKGROUND

Cardiac troponin T concentrations measured with high-sensitivity assays (hs-cTnT) provide important prognostic information for patients with stable coronary artery disease (CAD). However, whether hs-cTnT concentrations mainly reflect left ventricular (LV) remodeling or recurrent myocardial ischemia in this population is not known.

METHODS

We measured hs-cTnT concentrations in 619 subjects with suspected stable CAD in a prospectively designed multicenter study. We identified associations with indices of LV remodeling, as assessed by cardiac MRI and echocardiography, and evidence of myocardial ischemia diagnosed by single positron emission computed tomography.

RESULTS

Median hs-cTnT concentration was 7.8 ng/L (interquartile range, 4.8–11.6 ng/L), and 111 patients (18%) had hs-cTnT concentrations above the upper reference limit (&gt;14 ng/L). Patients with hs-cTnT &gt;14 ng/L had increased LV mass (144 ± 40 g vs 116 ± 34 g; P &lt; 0.001) and volume (179 ± 80 mL vs 158 ± 44 mL; P = 0.006), lower LV ejection fraction (LVEF) (59 ± 14 vs 62 ± 11; P = 0.006) and global longitudinal strain (14.1 ± 3.4% vs 16.9 ± 3.2%; P &lt; 0.001), and more reversible perfusion defects (P = 0.001) and reversible wall motion abnormalities (P = 0.008). Age (P = 0.009), estimated glomerular filtration rate (P = 0.01), LV mass (P = 0.003), LVEF (P = 0.03), and evidence of reversible myocardial ischemia (P = 0.004 for perfusion defects and P = 0.02 for LV wall motion) were all associated with increasing hs-cTnT concentrations in multivariate analysis. We found analogous results when using the revised US upper reference limit of 19 ng/L.

CONCLUSIONS

hs-cTnT concentrations reflect both LV mass and reversible myocardial ischemia in patients with suspected stable CAD.

Detection of subclinical left ventricular dysfunction by tissue Doppler imaging in horses with aortic regurgitation

BACKGROUND

Aortic regurgitation (AR) can have an important clinical impact and in some cases leads to left ventricular (LV) failure. Tissue Doppler imaging (TDI) is an echocardiographic technique that has been used in horses to detect LV dysfunction.

OBJECTIVES

To examine whether TDI detects changes in radial myocardial wall motion in horses with AR compared with control horses.

STUDY DESIGN

Case-control study.

METHODS

Echocardiography was performed in 30 healthy Warmblood horses and 34 Warmblood horses with AR, subdivided in groups with mild, moderate or severe AR. TDI measurements were performed on six segments of the short-axis images of the LV myocardial wall. Myocardial wall motion was evaluated by measuring velocity and deformation during isovolumetric contraction, systole, early and late diastole. Timing of different events was also measured.

RESULTS

In most segments, a significantly higher systolic myocardial velocity was found in horses with AR compared with controls. Horses with AR also had higher late diastolic velocity, although the difference was not significant in all segments. TDI measurement of timing intervals demonstrated less difference between groups.

MAIN LIMITATIONS

There was a significant difference in age between the control group and horses with AR, which may confound the results. The assessment of AR severity was based on subjective criteria as there is no gold standard.

CONCLUSIONS

TDI showed significant differences in radial systolic and late diastolic myocardial velocity in horses with AR. This could indicate an altered LV function in these horses, but further research is needed to investigate the prognostic value of these measurements.

Exercise physiology with a left ventricular assist device: Analysis of heart-pump interaction with a computational simulator

Patients with a Ventricular Assist Device (VAD) are hemodynamically stable but show an impaired exercise capacity. Aim of this work is to identify and to describe the limiting factors of exercise physiology with a VAD. We searched for data concerning exercise in heart failure condition and after VAD implantation from the literature. Data were analyzed by using a cardiorespiratory simulator that worked as a collector of inputs coming from different papers. As a preliminary step the simulator was used to reproduce the evolution of hemodynamics from rest to peak exercise (ergometer cycling) in heart failure condition. Results evidence an increase of cardiac output of +2.8 l/min and a heart rate increase to 67% of the expected value. Then, we simulated the effect of a continuous-flow VAD at both rest and exercise. Total cardiac output increases of +3.0 l/min (+0.9 l/min due to the VAD and +2.1 l/min to the native ventricle). Since the left ventricle works in a non-linear portion of the diastolic stiffness line, we observed a consistent increase of pulmonary capillary wedge pressure (from 14 to 20 mmHg) for a relatively small increase of end-diastolic volume (from 182 to 189 cm³). We finally increased VAD speed during exercise to the maximum possible value and we observed a reduction of wedge pressure (-4.5 mmHg), a slight improvement of cardiac output (8.0 l/min) and a complete unloading of the native ventricle. The VAD can assure a proper hemodynamics at rest, but provides an insufficient unloading of the left ventricle and does not prevent wedge pressure from rising during exercise. Neither the VAD provides major benefits during exercise in terms of total cardiac output, which increases to a similar extend to an unassisted heart failure condition. VAD speed modulation can contribute to better unload the ventricle but the maximal flow reachable with the current devices is below the cardiac output observed in a healthy heart.

Determinants of the effects of physical training and of the complications requiring resuscitation during exercise in patients with cardiovascular disease

BACKGROUND

Benefits of cardiac rehabilitation with exercise therapy are well-established, although individual reactions are heterogeneous. The identification of determinants of training effects is useful from a prognostic point of view, but data regarding this are scarce. Furthermore, limited data exist on the determinants of complications during exercise in cardiac patients. This study aimed to investigate the determinants (1) of training effects in cardiac rehabilitation and (2) of complications requiring resuscitation during exercise activities at the hospital and during continued exercise at a sports club for cardiac patients.

DESIGN

Clinical association study.

METHODS

Determinants of changes in peak oxygen uptake (VO2) after 3 months of cardiac rehabilitation were determined by multiple regression analysis (n=1909). Determinants of events requiring resuscitation (n=21) were assessed by logistic regression analysis.

RESULTS

Improvements in peak VO2 and exercise duration averaged 26%. Eighteen per cent of the variance in absolute improvements of peak VO2 was explained, with age and training characteristics as the strongest determinants. Twenty-one per cent of the variation in relative improvements was explained, with baseline exercise performance and training characteristics being the strongest determinants. The intake of anti-arrhythmics (odds ratio=5.5; P<0.001) and the presence of ST-segment depression (> or =1 mm) at baseline exercise testing (odds ratio=1.6; P<0.001) were predictive for serious complications. The occurrence of events requiring resuscitation was higher at the sports club (1/16,533 versus 1/29,214 patient-hours).

CONCLUSIONS

Age, baseline exercise performance and training characteristics were predictive for training effects in cardiac rehabilitation. Anti-arrhythmics and ST-segment depression at baseline exercise testing were predictive for complications.

Determining optimal noninvasive parameters for the prediction of left ventricular remodeling in chronic ischemic patients

OBJECTIVES

DOPPLER-CIP aims to determine the optimal noninvasive parameters (myocardial function, perfusion, ventricular blood flow, cell integrity) and methodology (ergometry, echocardiography, scintigraphy, MRI) in a given ischemic substrate that best predicts the impact of an intervention (or the lack thereof) on adverse morphological ventricular remodeling and functional recovery. Moreover, the relative predictive value of each of these parameters, in respect to the cost of extracting this information in order to enable optimization of cost-effectiveness for improved health care, will be determined by this project.

DESIGN

DOPPLER-CIP is a multi-center registry study. All patients with ischemic heart disease included in this study undergo at least two noninvasive stress imaging examinations at baseline. The presence/or absence of left ventricular (LV) remodeling will be assessed after a follow-up of 2 years, during which all cardiac events will be registered.

RESULTS

676 patients were included. Currently, baseline data analysis is almost finished and the follow-up is ongoing.

CONCLUSIONS

After completion, DOPPLER-CIP will provide evidence-based guidelines toward the most effective use of cardiac imaging in the chronically ischemic heart disease patient. The study will generate information, knowledge, and insight into the new imaging methodologies and into the pathophysiology of chronic ischemic heart disease.

Consistent regional heterogeneity of passive diastolic stretch and systolic deformation in the healthy heart: age-related changes in left ventricle contractility

The consistency of the normal spatial distribution of segmental passive stretch (PreS) and systolic strain (SS) within the left ventricle was investigated and a recently proposed echocardiographic estimate of left ventricular (LV) contractility was used to detect contractility changes with age. Hereto, in 54 healthy subjects, segmental PreS and SS were measured on tissue Doppler images of six left ventricle walls. For each subject, a linear regression line was estimated through the segmental PreS and SS values. The slopes and intercepts of this PreS-SS relationship did not differ between age groups, suggesting no changes in LV contractility with age. Moreover, a consistent regional distribution of PreS was observed, with the highest values measured in the septum, resulting in a similar distribution of SS as a direct consequence of the Frank-Starling mechanism.

The slope of the segmental stretch-strain relationship as a noninvasive index of LV inotropy

OBJECTIVES

The aim of this study was to test the hypothesis that the noninvasively constructed slope of the relationship between left ventricular (LV) regional systolic strain and stretch during atrial contraction represents LV inotropic state.

BACKGROUND

LV systolic response to a changing preload depends on its inotropic state. Changing the preload has allowed constructing the slope of the end-systolic pressure-volume relationship that is used as an invasive measurement of LV inotropy. We assumed that the slope of the relationship between regional systolic LV strain (total_S) and stretch during atrial contraction (preS) depends on the LV inotropic state as well and can thus be used as a LV inotropy index.

METHODS

Strain curves (tissue Doppler) were extracted from 27 healthy individuals to determine the normal stretch-strain relationship at rest, during a low-dose dobutamine (LD) challenge and during passive leg-lift (LL). The method was also applied in 7 patients with breast cancer before and after chemotherapy with anthracyclines.

RESULTS

PreS and total_S correlated closely in all subjects (r = 0.82). Total_S values increased (p < 0.05) with LD (-20.44 ± 3.89% vs. -24.24 ± 5.55%) and LL (-19.65 ± 3.77% vs. -24.05 ± 3.67%), whereas preS increased only with LL (5.96 ± 1.72% vs. 8.61 ± 2.18%), but not with LD (6.83 ± 2.34% vs. 7.29 ± 2.24%). No changes of total_S or preS were observed after the exposure to chemotherapy (-21.23 ± 2.93% vs. -21.49 ± 2.89% and 8.11 ± 1.03% vs. 8.59 ± 1.73%, respectively). The slope of stretch-strain relationship got steeper with LD (-1.47 ± 0.36 vs. -2.34 ± 0.36, p < 0.05), declined after the chemotherapy (-1.68 ± 0.15 to -0.86 ± 0.23, p < 0.05) and did not change with LL (-1.39 ± 0.57 vs. -1.51 ± 0.38, p = NS).

CONCLUSIONS

The slope of the regional stretch-strain relationship can be regarded as a noninvasive index of myocardial inotropic state. It gets steeper with increasing inotropy, does not change with preload induced changes of LV systolic function, and flattens after the exposure to a cardiotoxic drug.

Assessment of strain and strain rate by two-dimensional speckle tracking in mice: comparison with tissue Doppler echocardiography and conductance catheter measurements

AIMS

This study was designed in order to compare the strain and strain rate deformation parameters assessed by speckle tracking imaging (STI) with those of tissue Doppler imaging (TDI) and conductance catheter measurements in chronic murine models of left ventricular (LV) dysfunction.

METHODS AND RESULTS

Twenty-four male C57BL/6J mice were assigned to wild-type (n = 8), myocardial infarction (n = 8) and transaortic constriction (n = 8) groups. Echocardiographic and conductance measurements were simultaneously performed at rest and during dobutamine infusion (5 µg/kg/min) in all animals 10 weeks post-surgery. The LV circumferential strain (Scirc) and the strain rate (SRcirc) were derived from grey scale and tissue Doppler data at frame rates of 224 and 375 Hz, respectively. Scirc and SRcirc by TDI/STI correlated well with the preload recruitable stroke work (PRSW) (r = -0.64 and -0.71 for TDI; r = -0.46 and -0.50 for STI, P < 0.05). Both modalities showed a good agreement with respect to Scirc and SRcirc (r = 0.60 and r = 0.63, P < 0.05). During stress, however, TDI-estimated Scirc and SRcirc values were predominantly higher than those measured by STI (P < 0.05). The similarity of Scirc and SRcirc measurements with respect to the STI/TDI data was examined by the Bland-Altman analysis.

CONCLUSION

In mice, the STI- and TDI-derived strain and strain rate deformation parameters relate closely to intrinsic myocardial function. At low heart rate-to-frame rate ratios (HR/FR), both STI and TDI are equally acceptable for assessing the LV function non-invasively in these animals. At HR/FR (e.g. dobutamine challenge), however, these methods cannot be used interchangeably as STI underestimates S and SR at high values.

Morphological and Functional Adaptation of the Maternal Heart During Pregnancy

Background—

Pregnancy provides a unique model to study the adaptation of the heart in a physiological situation of transient load changes. The aim of this study was to assess the performance of the left ventricle (LV) in normal, uncomplicated pregnancies while considering the actual LV load and shape.

Methods and Results—

Serial echocardiographic examinations were performed in 51 women in each pregnancy trimester and 3 to 6 months after delivery. Data from 10 nulliparous, age-matched women were used as the control. Conventional parameters of LV function (ejection fraction) as well as myocardial deformation (strain) were interpreted, taking into consideration maternal hemodynamics and LV shape. Cardiac output increased during pregnancy because of a higher stroke volume in early pregnancy and a late increase in heart rate, whereas total vascular resistance decreased. Progressive development of eccentric hypertrophy was observed, which subsequently recovered postpartum. Sphericity index decreased from the first to the third trimester (1.92±0.17 versus 1.71±0.17) and returned postpartum to values comparable to the control. Although higher LV stroke work was noted toward the third trimester (5.9±1.1 versus 5.3±1.0 Newton meter, P <0.001), ejection fraction showed no significant changes. LV strain decreased significantly in late pregnancy (−19.5±2% to −17.6±1.6%, P <0.001) and returned to baseline values after delivery (−19.5±2%).

Conclusions—

Pregnancy is a physiological process associated with increased cardiac performance and progressive LV remodeling. These changes are not directly reflected by parameters traditionally considered to describe systolic function, such as ejection fraction and longitudinal deformation. While ejection fraction was insensitive to the functional changes, the transient decrease in longitudinal deformation becomes only plausible when considering the changes in LV geometry.

The relative value of strain and strain rate for defining intrinsic myocardial function

It is well accepted that strain and strain rate deformation parameters are not only a measure of intrinsic myocardial contractility but are also influenced by changes in cardiac load and structure. To date, no information is available on the relative importance of these confounders. This study was designed to investigate how strain and strain rate, measured by Doppler echocardiography, relate to the individual factors that determine cardiac performance. Echocardiographic and conductance measurements were simultaneously performed in mice in which individual determinants of cardiac performance were mechanically and/or pharmacologically modulated. A multivariable analysis was performed with radial and circumferential strains and peak systolic radial and circumferential strain rates as dependent parameters and preload recruitable stroke work (PRSW), arterial elastance ( Ea), end-diastolic pressure, and left ventricular myocardial volume (LVMV) as independent factors representing myocardial contractility, afterload, preload, and myocardial volume, respectively. Radial strain was most influenced by Ea (β = −0.58, R2 = 0.34), whereas circumferential strain was strongly associated with Ea and moderately with LVMV (β = 0.79 and −0.52, respectively, R2 = 0.54). Radial strain rate was related to both PRSW and LVMV ( β = 0.79 and −0.62, respectively, R2 = 0.50), whereas circumferential strain rate showed a prominent correlation only with PRSW (β = −0.61, R2 = 0.51). In conclusion, strain (both radial and circumferential) is not a good surrogate measure of intrinsic myocardial contractility unless the strong confounding influence of afterload is considered. Strain rate is a more robust measure of contractility that is less influenced by changes in cardiac load and structure. Thus, peak systolic strain rate is the more relevant parameter to assess myocardial contractile function noninvasively.

Hospital quality management: the perspective of a Belgian academic medical center

In this article, we explain why from our perspective as the largest academic medical center in the country, we consider it to be part of our mission to contribute to the elaboration of a value-based health care organization system. We describe our hospital quality management system and how we think that this can deliver added value by introducing lean principles in the care process. We also reflect on the importance of hospital accreditation and external benchmarking in the continuous quality improvement culture within the hospital.

Assessment of apical rocking: a new, integrative approach for selection of candidates for cardiac resynchronization therapy

AIMS

Current attempts of improving patient selection in cardiac resynchronization therapy (CRT) are mainly based on echocardiographic timing of myocardial velocity peaks. Regional myocardial function is neglected. Apical transverse motion (ATM) is a new parameter to quantify apical rocking as an integrative surrogate of both temporal and functional inhomogeneities within the left ventricle. In this study, we tested the predictive value of apical rocking for response to CRT.

METHODS AND RESULTS

Sixty-nine patients eligible for CRT were assessed by echocardiography before and 11 ± 5 months after pacemaker implantation. Response was defined as left ventricular (LV) end-systolic volume decrease >15%. Rocking was quantified (ATM) and visually assessed by four blinded readers. Predictive value for CRT response of both assessments was compared with conventional dyssynchrony parameters. ATM in the four-chamber view plane differentiated best between responders and non-responders (2.2 ± 1.5 vs. 0.06 ± 1.9 mm, P< 0.0001). Quantified ATM predicted reverse remodelling with a sensitivity, specificity, and accuracy of 75, 96, and 83% whereas visual rocking assessment resulted in 89, 75, and 83%, respectively. The accuracy of conventional parameters was significantly lower.

CONCLUSION

Apical rocking is a new marker to assess LV dyssynchrony and predict CRT response. It is superior to conventional parameters. Even its simple visual assessment may be sufficiently accurate in the clinical setting.

Effect of endurance training on blood pressure regulation, biomarkers and the heart in subjects at a higher age

We reported previously that two otherwise identical training programs at lower (LI) and higher intensity (HI) similarly reduced resting systolic blood pressure (BP) by approximately 4-6 mmHg. Here, we determined the effects of both programs on BP-regulating mechanisms, on biomarkers of systemic inflammation and prothrombotic state and on the heart. In this cross-over study (3 × 10 weeks), healthy participants exercised three times 1 h/week at, respectively, 33% and 66% of the heart rate (HR) reserve, in a random order, with a sedentary period in between. Measurements, performed at baseline and at the end of each period, involved blood sampling, HR variability, systolic BP variability (SBPV) and cardiac magnetic resonance imaging. Thirty-nine participants (18 men; mean age 59 years) completed the study. Responses were not different between both programs (P>0.05). Pooled data from LI and HI showed a reduction in HR (-4.3 ± 8.1%) and an increase in stroke volume (+11 ± 23.1%). No significant effect was seen on SBPV, plasma renin activity, basal nitric oxide and left ventricular mass. Our results suggest that the BP reduction observed appears to be due to a decrease in systemic vascular resistance; training intensity does not significantly affect the results on mechanisms, biomarkers and the heart.

Apical transverse motion as surrogate parameter to determine regional left ventricular function inhomogeneities: a new, integrative approach to left ventricular asynchrony assessment

AIMS

Left ventricular (LV) asynchrony assessment is mostly based on delays between regional myocardial velocity peaks. Regional function is barely considered. We propose apical transverse motion (ATM) as a new parameter integrating both temporal and functional information, which was tested in different conduction delays.

METHODS AND RESULTS

We examined 67 patients, 11 patients with post-infarct ischaemic left bundle branch blocks (iLBBB) and 25 patients with non-ischaemic left bundle branch block (nLBBB), 12 patients with right bundle branch block (RBBB), and 19 normal healthy volunteers (NORM). Longitudinal colour tissue Doppler data were used to calculate the total transverse apex motion (ATM), the transverse motion in the four-chamber view plane alone (ATM(4CV)) as well as regional myocardial deformation and conventional LV asynchrony parameters. Median ATM was 1.8 mm in NORM, 1.5 mm in RBBB (P = 0.999), 2.4 mm in iLBBB (P = 0.183), and 4.3 mm in nLBBB (P < 0.001 vs. NORM and RSB). ATM(4CV) behaved similarly, showed a good correlation with regional deformation data, and distinguished well between NORM and LBBB (AUC = 0.87).

CONCLUSION

Apical transverse motion is a new and simple parameter integrating information on both regional and temporal function inhomogeneities of the LV. It has a potential role in assessing LV asynchrony in the clinical context.

Strain rate imaging detects early cardiac effects of pegylated liposomal Doxorubicin as adjuvant therapy in elderly patients with breast cancer

OBJECTIVE

Cardiac toxicity remains an important side effect of anthracyclines. New drug formulations (eg, pegylated liposomal doxorubicin [PL-DOX]) seem to be a successful strategy for reducing it. Changes in cardiac function induced by early chemotherapy, however, are subtle and difficult to quantitate by conventional imaging methods. Doppler myocardial imaging-based velocity, strain, and strain rate measurements have been shown to sensitively quantify abnormalities in cardiac function in other settings.

DESIGN

We evaluated the feasibility and sensitivity of strain rate imaging compared with conventional echocardiography in detecting cardiac effects of PL-DOX therapy in elderly patients with cancer. In a pilot study, we examined 16 elderly women (age 69.8 +/- 3.1 years) with breast cancer receiving 6 cycles of PL-DOX. Conventional and Doppler myocardial imaging echocardiography were obtained at baseline and after 3 and 6 cycles of treatment. Segmental peak systolic longitudinal and radial velocity, strain, and strain rate were measured.

RESULTS

Left ventricular dimensions, ejection fraction, and systolic myocardial velocity did not change throughout the follow-up. In contrast, a significant reduction in longitudinal and radial strain and strain rate was found after 6 cycles (longitudinal strain -18.8% +/- 2.8% vs -22.7% +/- 2.8%, P < .001 vs baseline and P = .001 vs after 3 cycles; radial strain 32.3% +/- 8.1% vs 50.1% +/- 11.6%, P < .001 vs baseline). Changes in radial function appeared earlier and were more pronounced than in longitudinal direction.

CONCLUSION

In contrast with conventional echocardiography and myocardial velocity measurements, myocardial deformation parameters allowed detecting subtle changes in longitudinal and radial left ventricular function after 6 cycles of PL-DOX. We suggest that Doppler-based myocardial deformation imaging should be used for cardiac function monitoring during chemotherapy.