Quantitative left ventricular systolic function: From chamber to myocardium

Elevated plasma solMER concentrations link ambient PM2.5 and PAHs to myocardial injury and reduced left ventricular systolic function in children

Exposure to fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) is known to be associated with the polarization of pro-inflammatory macrophages and the development of various cardiovascular diseases. The pro-inflammatory polarization of resident cardiac macrophages (cMacs) enhances the cleavage of membrane-bound myeloid-epithelial-reproductive receptor tyrosine kinase (MerTK) and promotes the formation of soluble MerTK (solMER). This process influences the involvement of cMacs in cardiac repair, thus leading to an imbalance in cardiac homeostasis, myocardial injury, and reduced cardiac function. However, the relative impacts of PM2.5 and PAHs on human cMacs have yet to be elucidated. In this study, we aimed to investigate the effects of PM2.5 and PAH exposure on solMER in terms of myocardial injury and left ventricular (LV) systolic function in healthy children. A total of 258 children (aged three to six years) were recruited from Guiyu (an area exposed to e-waste) and Haojiang (a reference area). Mean daily PM2.5 concentration data were collected to calculate the individual chronic daily intake (CDI) of PM2.5. We determined concentrations of solMER and creatine kinase MB (CKMB) in plasma, and hydroxylated PAHs (OH-PAHs) in urine. LV systolic function was evaluated by stroke volume (SV). Higher CDI values and OH-PAH concentrations were detected in the exposed group. Plasma solMER and CKMB were higher in the exposed group and were associated with a reduced SV. Elevated CDI and 1-hydroxynaphthalene (1-OHNa) were associated with a higher solMER. Furthermore, increased solMER concentrations were associated with a lower SV and higher CKMB. CDI and 1-OHNa were positively associated with CKMB and mediated by solMER. In conclusion, exposure to PM2.5 and PAHs may lead to the pro-inflammatory polarization of cMacs and increase the risk of myocardial injury and systolic function impairment in children. Furthermore, the pro-inflammatory polarization of cMacs may mediate cardiotoxicity caused by PM2.5 and PAHs.

Non-invasive pulse arrival time is associated with cardiac index in pediatric heart transplant patients with normal ejection fraction

Objective.Cardiac Index (CI) is a key physiologic parameter to ensure end organ perfusion in the pediatric intensive care unit (PICU). Determination of CI requires invasive cardiac measurements and is not routinely done at the PICU bedside. To date, there is no gold standard non-invasive means to determine CI. This study aims to use a novel non-invasive methodology, based on routine continuous physiologic data, called Pulse Arrival Time (PAT) as a surrogate for CI in patients with normal Ejection Fraction (EF).Approach.Electrocardiogram (ECG) and photoplethysmogram (PPG) signals were collected from beside monitors at a sampling frequency of 250 samples per second. Continuous PAT, derived from the ECG and PPG waveforms was averaged per patient. Pearson's correlation coefficient was calculated between PAT and CI, PAT and heart rate (HR), and PAT and EF.Main Results.Twenty patients underwent right heart cardiac catheterization. The mean age of patients was 11.7 ± 5.4 years old, ranging from 11 months old to 19 years old, the median age was 13.4 years old. HR in this cohort was 93.8 ± 17.0 beats per minute. The average EF was 54.4 ± 9.6%. The average CI was 3.51 ± 0.72 l min-1m-2, with ranging from 2.6 to 4.77 l min-1m-2. The average PAT was 0.31 ± 0.12 s. Pearson correlation analysis showed a positive correlation between PAT and CI (0.57,p< 0.01). Pearson correlation between HR and CI, and correlation between EF and CI was 0.22 (p= 0.35) and 0.03 (p= 0.23) respectively. The correlation between PAT, when indexed by HR (i.e. PAT × HR), and CI minimally improved to 0.58 (p< 0.01).Significance.This pilot study demonstrates that PAT may serve as a valuable surrogate marker for CI at the bedside, as a non-invasive and continuous modality in the PICU. The use of PAT in clinical practice remains to be thoroughly investigated.

Advanced maternal age alters cardiac functional and structural adaptations to pregnancy in rats

A significant number of pregnancies occur at advanced maternal age (>35 yr), which is a risk factor for pregnancy complications. Healthy pregnancies require massive hemodynamic adaptations, including an increased blood volume and cardiac output. There is growing evidence that these cardiovascular adaptations are impaired with age, however, little is known about maternal cardiac function with advanced age. We hypothesized that cardiac adaptations to pregnancy are impaired with advanced maternal age. Younger (4 mo; ∼early reproductive maturity in humans) and aged (9 mo; ∼35 yr in humans) pregnant Sprague-Dawley rats were assessed and compared with age-matched nonpregnant controls. Two-dimensional echocardiographic images were obtained (ultrasound biomicroscopy; under anesthesia) on gestational day 19 (term = 22 days) and compared with age-matched nonpregnant rats (n = 7-9/group). Left ventricular structure and function were assessed using short-axis images and transmitral Doppler signals. During systole, left ventricular anterior wall thickness increased with age in the nonpregnant rats, but there was no age-related difference between the pregnant groups. There were no significant pregnancy-associated differences in left ventricular wall thickness. Calculated left ventricular mass increased with age in nonpregnant rats and increased with pregnancy only in young rats. Compared with young pregnant rats, the aortic ejection time of aged pregnant rats was greater and Tei index was lower. Overall, the greater aortic ejection time and lower Tei index with age in pregnant rats suggest mildly altered cardiac adaptations to pregnancy with advanced maternal age, which may contribute to adverse outcomes in advanced maternal age pregnancies.NEW & NOTEWORTHY We demonstrated that even before the age of reproductive senescence, rats show signs of age-related alterations in cardiac structure that suggests increased cardiac work. Our data also demonstrate, using an in vivo echocardiographic approach, that advanced maternal age in a rat model is associated with altered cardiac function and structure relative to younger pregnant controls.

The Role of LVOT-VTI Measurement in the Evaluation of Systolic Heart Function in Pulmonary ICU Patients

Introduction:

The detection of cardiac systolic dysfunction is very important for well management of pulmonary critical care patients (PCCPs). However, there is a poor correlation between echocardiographic cardiac systolic function (CSF) parameters and it is not easy to obtain these parameters in PCCPs. Therefore, this cross-sectional observational study was planned for the detection of a more easily obtainable echocardiographic CSF parameter that is well correlated with other CSF parameters in PCCPs.

Materials and Methods:

Total 88 PCCPs were included. Demographic and clinical information and laboratory tests of all patients were recorded. The CSF parameters of the heart were obtained by transthoracic echocardiography with appropriate technique. LVOT-VTI (Left ventricular outflow tract velocity time integral), CO (cardiac output), EPSS (e point septal separation), Left ventricular EF (ejection fraction) and TAPSE (Tricuspid Annular Plane Systolic Excursion) as an indicator of CSF were tried to obtain from all patients. We also calculated sensitivity, specificity, positive and negative predictive values of LVOT-VTI<20 parameters to diagnose heart failure.

Results:

The mean age of the patients was 73±12, 40% were female, 38% were intubated and 52% had COPD. LVOT-VTI, EF, CO, EPSS parameters were obtained in 54(61%), 24(27%), 48(54%), 48(54%) patients, respectively. Decreased LVOT-VTI (<20 cm) was well correlated with decreased EF (<45%) (p=0.001, r=0.77), decreased CO (<5 L/dk) (p=0.03, r=0.64) and decreased TAPSE (<17 mm) (p=0.001, r=0.71). Also, there was good agreement between the EF and LVOTVTI measurements (Kappa:0.78, p:0.001). Sensitivity, specificity, positive and negative predictive values of LVOT-VTI<20 for heart failure were 58, 78, 84, 49, repectively.

Conclusion:

LVOT-VTI is a more easily obtainable and well correlated parameter, which can be used as an indicator of CSF in PCCPs.

Clinical Significances:

The authors believe that LVOT-VTI measurement has good correlation with other echocardiographic systolic function parameters, and its easy measurement in intensive care patients makes it a very useful test for cardiac systolic function evaluation.

Left and Right Ventricular Impairment Shortly After Correction of Tetralogy of Fallot

Surgical repair of Tetralogy of Fallot (ToF) is usually performed in the first months of life with low early postoperative mortality. During long-term follow-up, however, both right (RV) and left ventricular (LV) performances may deteriorate. Tissue Doppler imaging (TDI) and speckle tracking echocardiography (ST) can unmask a diminished RV and LV performance. The objective of the current study was to assess the cardiac performance before and shortly after corrective surgery in ToF patients using conventional, TDI and ST echocardiographic techniques. Thirty-six ToF patients after surgery were included. Transthoracic echocardiography including TDI and ST techniques was performed preoperatively and at hospital discharge after surgery (10 days to 4 weeks after surgery). Median age at surgery was 7.5 months [5.5-10.9]. Regarding the LV systolic function there was a significant decrease in interventricular septum (IVS) S' at discharge as compared to preoperatively (pre IVS S' = 5.4 ± 1.4; post IVS S' = 3.9 ± 1.2; p < 0.001) and in global longitudinal peak strain (GLS) (pre = - 18.3 ± 3.4; post = - 14.2 ± 4.1; p = 0.003); but not in the fractional shortening (FS). Both conventional and TDI parameters showed a decrease in diastolic function at discharge. Tricuspid Annular Plane Systolic Excursion and RV S' were significantly lower before discharge. When assessing the RV diastolic performance, only the TDI demonstrated a RV impairment. There was a negative correlation between age at surgery and postoperative LV GLS (R = - 0.41, p = 0.031). There seems to be an impairment in left and right ventricle performance at discharge after ToF corrective surgery compared to preoperatively. This is better determined with TDI and ST strain imaging than with conventional echocardiography.

The prognostic value of left ventricular systolic function and cardiac biomarkers in pediatric severe sepsis

Echocardiography and cardiac biomarkers, such as cardiac troponin I (cTnI) and N-terminal pro-B-type natriuretic peptide (NT-pro BNP) are useful tools to evaluate cardiac dysfunction. Left ventricular systolic dysfunction (LVSD) is common in pediatric severe sepsis. The aim of this study is to evaluate the prognostic value of LVSD, cTnI, and NT-pro BNP for pediatric severe sepsis.A prospective, single center, observational study was conducted. Severe sepsis children were enrolled in the study from December 2015 to December 2016 in pediatric intensive care unit of Shanghai Children's Medical Center. Recorded general information, transthoracic echocardiography were performed at day 1, 2, 3, 7, and 10, using Simpson to measure left ventricular end-diastolic dimension and left ventricular end-systolic dimension, obtained echocardiography parameters: left ventricular ejection fraction (LVEF), left ventricular fractional shortening, left ventricular end-diastolic volume, left ventricular end- systolic volume, stroke volume, cardiac output. At the same time collecting the blood sample to measure cTnI, NT-pro BNP. The definition of LVSD was LVEF <50%. According to the prognosis of 28 days, children with severe sepsis were divided into survived group and nonsurvived group.Total of 50 pediatric patients who were diagnosed with severe sepsis (including septic shock) were enrolled, the incidence of LVSD was 52%. The 28-day mortality rate of severe sepsis was 34%. Multivariate logistic regression analyses for predictors of death in pediatric severe sepsis revealed that the 28-day mortality of severe sepsis was associated with mechanical ventilation (MV) within the first 6 hours of admission (odds ratio [OR], 0.01; 95% confidence interval [CI], 0.00-0.07) and total MV time (OR, 0.81; 95% CI, 0.68-0.97). The receiver operating characteristic curves LVEF (area under curve = 0.526), cTnI (area under curve = 0.480), and NT-pro BNP (area under curve = 0.624) were used to predict the 28-day mortality in pediatric severe sepsis. Follow-up echocardiography parameters for survived group and nonsurvived group showed no significant changes in LVEF, LVFS, stroke volume index, cardiac index (CI), left ventricular end-diastolic volume index and left ventricular end-systolic volume index at day 1, 2, 3, 7, and 10, except for CI at day 1 and 2. Kaplan-Meier plot of 28-day mortality and LVSD in pediatric severe sepsis showed there were no statistical differences (χ = 0.042, P = .837).LVSD occurs frequently in pediatric with severe sepsis. The 28-day mortality rate of severe sepsis was also high. In this study, none of LVSD, cTnI, and NT-proBNP was associated with the prognosis of pediatric severe sepsis.

Maternal treatment with a placental-targeted antioxidant (MitoQ) impacts offspring cardiovascular function in a rat model of prenatal hypoxia

Intrauterine growth restriction, a common consequence of prenatal hypoxia, is a leading cause of fetal morbidity and mortality with a significant impact on population health. Hypoxia may increase placental oxidative stress and lead to an abnormal release of placental-derived factors, which are emerging as potential contributors to developmental programming. Nanoparticle-linked drugs are emerging as a novel method to deliver therapeutics targeted to the placenta and avoid risking direct exposure to the fetus. We hypothesize that placental treatment with antioxidant MitoQ loaded onto nanoparticles (nMitoQ) will prevent the development of cardiovascular disease in offspring exposed to prenatal hypoxia. Pregnant rats were intravenously injected with saline or nMitoQ (125 μM) on gestational day (GD) 15 and exposed to either normoxia (21% O₂) or hypoxia (11% O₂) from GD15-21 (term: 22 days). In one set of animals, rats were euthanized on GD 21 to assess fetal body weight, placental weight and placental oxidative stress. In another set of animals, dams were allowed to give birth under normal atmospheric conditions (term: GD 22) and male and female offspring were assessed at 7 and 13 months of age for in vivo cardiac function (echocardiography) and vascular function (wire myography, mesenteric artery). Hypoxia increased oxidative stress in placentas of male and female fetuses, which was prevented by nMitoQ. 7-month-old male and female offspring exposed to prenatal hypoxia demonstrated cardiac diastolic dysfunction, of which nMitoQ improved only in 7-month-old female offspring. Vascular sensitivity to methacholine was reduced in 13-month-old female offspring exposed to prenatal hypoxia, while nMitoQ treatment improved vasorelaxation in both control and hypoxia exposed female offspring. Male 13-month-old offspring exposed to hypoxia showed an age-related decrease in vascular sensitivity to phenylephrine, which was prevented by nMitoQ. In summary, placental-targeted MitoQ treatment in utero has beneficial sex- and age-dependent effects on adult offspring cardiovascular function.

Myocardial strain/stress changes identified by echocardiography may reveal early sepsis-induced myocardial dysfunction

Objective

To perform early assessment of sepsis-induced myocardial dysfunction (SIMD) using strain/stress echocardiography.

Methods

A canine model of SIMD was established using intravenous injection of lipopolysaccharide (LPS, 2 mg/kg). Thirteen dogs were included, comprising an LPS-treated SIMD group (n = 7) and saline control group (n = 6). SIMD was assessed at various time-points using cardiac measurements including haemodynamics and echocardiography.

Results

Systolic and radial ventricular wall stress and circular ventricular wall stress (WSsc) were significantly lower in the sepsis group versus the control group at all time-points. Logistic regression analysis revealed an inverse correlation between stress rate of the front-posterior and bottom wall and left ventricle systolic wall strength. In contrast, a positive correlation was found between the mean velocity of circumferential fibre shortening (mVCF) or heart rate-adjusted mVCF (RVCF) and WSsc. Using regression equations, predicted values for mVCF and RVCF in animals with sepsis were significantly higher than measured values at 4- 5- and 6-h time-points.

Conclusions

These findings will further the understanding of pathophysiological alterations in SIMD at the early stage of sepsis, and suggest that strain rate may reflect the nature of myocardial contractility.

Detection of Acute Changes in Left Ventricular Function by Myocardial Deformation Analysis after Excessive Alcohol Ingestion

BACKGROUND

The effects of acute excessive alcohol ingestion on echocardiographic parameters of left ventricular (LV) function are unclear.

METHODS

One hundred ninety-nine healthy subjects (44 ± 5 years, 71% male) were prospectively examined within 6 hours after excessive alcohol ingestion as well as after 4 weeks with strict alcohol abstinence. Echocardiography was performed at baseline and follow-up for conventional parameters (left ventricular ejection fraction [LVEF], transmitral E and A Doppler flow velocities, E/A ratio, tissue Doppler velocity lateral and septal (é), E/é ratio, deceleration time of E, and isovolumic relaxation time) and myocardial deformation data (such as global radial and global and layer-specific circumferential [endo and epi global CS] and longitudinal [endo and epi global LS] strain). Multivariate regression was used to assess the impact of independent variables on echocardiographic parameters.

RESULTS

Alcohol levels were 1.2 ± 0.3 g/L at the time of drinking cessation. After alcohol ingestion endo CS (30% ± 2% vs 37% ± 3%, P = .008) and endo LS (27% ± 4% vs 33% ± 3%, P = .002) were significantly lower at baseline versus follow-up. Blood pressure, LVEF and heart rate, and other echocardiographic parameters did not differ between the two examinations. Alcohol levels were modestly, negatively associated with change in endo CS and endo LS (r = -0.54, 95% CI, -0.63 to -0.43, P < .001; and r = -0.26, 95% CI, -0.39 to -0.14; P < .003, respectively). Alcohol levels were the strongest predictor for endo CS (β = -4.84; 95% CI, -6.31 to -3.37) and endo LS (β = -2.50; 95% CI, -4.32 to -0.68).

CONCLUSIONS

Acute alcohol ingestion effects endocardial CS and LS, suggesting an acute and transient toxic effect on myocardial deformation, an effect that remains undetected by conventional echocardiographic parameters. The current findings may help clinicians to gain more understanding into the mechanism of developing an alcohol cardiomyopathy and to detect early persistent alcohol-induced myocardial disturbances for an effective therapy in time to prevent harm.

S100A8 and S100A9 Are Associated with Doxorubicin-Induced Cardiotoxicity in the Heart of Diabetic Mice

Cardiomyopathy is a clinical problem that occurs in the hearts of type 2 diabetic patients as well as cancer patients undergoing doxorubicin chemotherapy. The number of diabetic cancer patients is increasing but surprisingly the cardiac damaging effects of doxorubicin, a commonly used chemotherapeutic drug, on diabetic hearts have not been well-examined. As the signaling mechanisms of the doxorubicin-induced cardiomyopathy in type 2 diabetic heart are largely unknown, this study examined the molecular signaling pathways that are responsible for the doxorubicin-induced cardiotoxicity in type 2 diabetic hearts. Male 14- to 18-week-old db/db mice were used as the type 2 diabetic model, and age-matched non-diabetic db/+ mice served as controls. The db/+ non-diabetic and db/db diabetic mice were randomly assigned to the following groups: db/+CON, db/+DOX-5d, db/+DOX-7d, db/dbCON, db/dbDOX-5d, and db/dbDOX-7d. Mice assigned to doxorubicin (DOX) group were exposed to an intraperitoneal (i.p.) injection of DOX at a dose of 15 mg/kg to induce cardiomyopathy. Mice in control (CON) groups were i.p. injected with the same volume of saline instead of DOX. Mice were euthanized by overdose of ketamine and xylazine 5 or 7 days after the DOX injection. Microarray analysis was adopted to examine the changes of the whole transcriptional profile in response to doxorubicin exposure in diabetic hearts. Ventricular fractional shortening was examined as an indicator of cardiac function by transthoracic echocardiography. The presence of diabetic cardiomyopathy in db/db mice was evident by the reduction of fractional shortening. There was a further impairment of cardiac contractile function 7 days after the DOX administration in db/db diabetic mice. According to our microarray analysis, we identified a panel of regulatory genes associated with cardiac remodeling, inflammatory response, oxidative stress, and metabolism in the DOX-induced cardiac injury in diabetic heart. The microarray results of selected genes were confirmed by real time PCR. Notably, S100A8 and S100A9 were found to have a unique specific expression pattern that was coincident with the DOX-induced cardiomyopathy in diabetic hearts. Correspondingly, NF-κB expression in diabetic hearts was increased together with the elevation of S100A8/9 and activation of p38 MAPK signaling after DOX administration, which induced cardiac inflammation as demonstrated by the elevation of cardiac IL-6 level. These findings provide novel pre-clinical information for revealing the S100A8/A9-associated molecular signaling pathways that mediate the doxorubicin-induced cardiotoxicity in diabetic hearts.

Protective effects of desacyl ghrelin on diabetic cardiomyopathy

AIM

Diabetic cardiomyopathy is a specific complication of type 2 diabetes mellitus, which causes progressive cardiac dysfunction. Desacyl ghrelin has been preliminarily demonstrated to have beneficial effects on cardiovascular system and glucose metabolism, which are both related to diabetic cardiomyopathy. The aim of this study was to investigate the protective effects of desacyl ghrelin on cardiac dysfunction, cardiac fibrosis, and cellular autophagy in a type 2 diabetic mouse model.

MATERIALS AND METHODS

Fourteen- to eighteen-week-old db/db diabetic and db/+ non-diabetic mice were intraperitoneally treated with desacyl ghrelin at a dosage of 100 μg/kg for ten consecutive days. Ventricular fractional shortening was examined as an indicator of cardiac function by transthoracic echocardiography.

RESULTS

The presence of diabetic cardiomyopathy was evident by the reduction in fractional shortening shown in our examined db/db mice. Intriguingly, this reduction in fractional shortening was not observed in the hearts of db/db mice treated with desacyl ghrelin. Cardiac fibrosis (indicated by excessive collagen deposition, decreased by Adiponectin and Mmp13 expression, and up-regulated by Mmp8 expression) and impairment of autophagic signalling (indicated by decreases in Foxo3 and LC3 II-to-LC3 I ratio) were shown in the hearts of diabetic mice. All these cellular and molecular alterations were alleviated by desacyl ghrelin treatment. The key cardiac pro-survival cellular signals including AMPK, Akt, ERK1/2, and GSK3α/β were impaired in the diabetic hearts, but the administration of desacyl ghrelin attenuated these signalling impairments.

CONCLUSIONS

These results collectively demonstrate that desacyl ghrelin protects the heart against cardiac dysfunction in type 2 diabetic mice by inhibiting excessive collagen deposition and enhancing cardiac autophagic signalling via the pro-survival cellular AMPK/ERK1/2 signalling pathways.

Prognosis of left ventricular systolic dysfunction in septic shock patients

INTRODUCTION

The prognosis of myocardial dysfunction in critically ill patients with sepsis and its association with mortality is controversial. We aim to determine the significance of left ventricular systolic dysfunction in septic shock patients and their associated outcome.

MATERIALS AND METHODS

A prospective, single center, observational study was carried out at an intensive care unit of a tertiary care hospital. A total of 66 patients diagnosed with septic shock were enrolled in the study from September 2010 to June 2012. The 2D echocardiography was performed for all the patients. Ejection fraction <50% was the diagnosing parameter for the patients with systolic dysfunction in septic shock. Acute Physiology and Chronic Health Evaluation III (APACHE III) score was calculated.

RESULTS

The mean age of patients were found to be 53.71 ± 16.76 years. The mortality rate was found to be 48.48% and among them 43.75% patients had ejection fraction <50%. Non-survivors exhibited significantly lower mean blood pressure (74.19 ± 10.28 versus 80.59 ± 11.31; p = 0.008), lower ejection fraction (52.59 ± 16.37 versus 62.56 ± 8.31; p = 0.029) and higher APACHE III score (89.34 ± 15.41 versus 70.65 ± 13.27; p <0.001). The receiver operating characteristic curves APACHE III score (area under curve = 0.830) and ejection fraction (area under curve = 0.656) were used to predict the mortality in septic patients.

CONCLUSION

Low ejection fraction, a marker to measure left ventricular systolic dysfunction is a predictor of mortality in septic shock patients. However, more research is needed to confirm the findings.

Correlation of left ventricular systolic dysfunction determined by low ejection fraction and 30-day mortality in patients with severe sepsis and septic shock: a systematic review and meta-analysis

INTRODUCTION

The prognostic implications of myocardial dysfunction in patients with sepsis and its association with mortality are controversial. Several tools have been proposed to evaluate cardiac function in these patients, but their usefulness beyond guiding therapy is unclear. We review the value of echocardiographic estimate of left ventricular ejection fraction (LVEF) in the setting of severe sepsis and/or septic shock and its correlation with 30-day mortality.

METHODS

We conducted a systematic review and meta-analysis to evaluate the prognostic functionality of newly diagnosed LV systolic dysfunction by transthoracic echocardiography on critical ill patients admitted to the intensive care unit with severe sepsis or septic shock.

RESULTS

A search of EMBASE and PubMed, Ovide MEDLINE, and Cochrane CENTRAL medical databases yielded 7 studies meeting inclusion criteria reporting on a total of 585 patients. The pooled sensitivity of depressed LVEF for mortality was 52% (95% confidence interval [CI], 29%-73%), and pooled specificity was 63% (95% CI, 53%-71%). Summary receiver operating characteristic curve showed an area under the curve of 0.62 (95% CI, 0.58-0.67). The overall mortality diagnostic odd ratio for septic patients with LV systolic dysfunction was 1.92 (95% CI, 1.27-2.899). Statistical heterogeneity of studies was moderate.

CONCLUSION

The presence of new LV systolic dysfunction associated with sepsis and defined as low LVEF is neither a sensitive nor a specific predictor of mortality. These findings are limited because of the heterogeneity and underpower of the studies. Further research into this method is warranted.

Inflammation and echocardiographic parameters of ventricular hypertrophy in a cohort with preserved cardiac function

OBJECTIVE

To investigate the association between inflammation and selective echocardiographic parameters (EP) characteristic for ventricular hypertrophy in cross-sectional and longitudinal population-based analyses.

METHODS

Baseline (711 men, 659 women: 45-83 years) and 4-year follow-up data (622 men, 540 women) of the prospective, population-based CARdio-vascular disease, Living and Ageing in Halle (CARLA)study after exclusion of participants with cardiacvascular diseases were analysed. Inflammation parameters: soluble tumour necrosis factor receptor 1 (sTNF-R1), high-sensitivity C reactive protein (hsCRP) and interleukin 6 (IL-6). EPs: left ventricular mass (LVM), left atrial systolic dimension (LADS), interventricular septum diameter (IVSD), posterior wall dimension (PWD), left ventricular diastolic diameter (LVDD), ejection fraction according to Teichholz (EF). For the longitudinal analyses baseline to follow-up differences were considered. Effect sizes were determined by using multiple linear regression and mixed models. Missing values were replaced by means of multiple imputations.

RESULTS

Men had higher sTNF-R1 levels; means of hsCRP and IL-6 were similar in men and women. In multiple regression models, sTNF-R1 was associated with LADS (1.4 mm/1000 pg/mL sTNF-R1, 95% CI 0.6 to 2.1) in men. Respecting confounder hsCRP was associated with LVM (5.2 g/10 mg/L hsCRP, 95% CI 1.6 to 8.8), IVSD (0.2 mm/10 mg/L hsCRP, 95% CI 0 to 0.3) and PWD (0.2 mm/10 mg/L hsCRP, 95% CI 0.1 to 0.3) in women, while there were no relevant effects in analysis of IL-6 in both sexes. The baseline to follow-up change in EPs was not relevantly associated with sTNF-R1, hsCRP or IL-6.

CONCLUSIONS

STNF-R1, hsCRP and IL-6 were inadequate predictors for structural changes of the heart at follow-up, while weak cross-sectional associations are restricted to certain EPs and depend on sex.

Image quality influences the assessment of left ventricular function: an intraoperative comparison of five 2-dimensional echocardiographic methods with real-time 3-dimensional echocardiography as a reference

OBJECTIVES

Transesophageal echocardiography has become a standard tool for evaluating left ventricular function during cardiac surgery. However, the image quality varies widely between patients and examinations. The aim of this study was to investigate the influence of the image quality on 5 commonly used 2-dimensional methods.

METHODS

Transesophageal real-time 3-dimensional echocardiography (3DE) served as a reference. Left ventricular function was evaluated in 63 patients with sufficient real-time 3DE image quality. The image quality was rated using the ratio of the visualized border divided by the total endocardial border. These ratings were used to generate groups of poor (0%-40%), fair (41%-70%), and good (71%-100%) image quality. The ejection fraction (EF), end-diastolic volume, and end-systolic volume were analyzed by the Simpson method of disks (biplane and monoplane), eyeball method, Teichholz method, and speckle-tracking method. Furthermore, the fractional area change was determined. Each correlation with real-time 3DE was evaluated.

RESULTS

Correlations of the EF and volumes, respectively, as determined by long-axis view methods increased with improving image quality: the Simpson biplane method was found to be the most accurate method, with good image quality for the EF (r = 0.946) and volumes (end-diastolic volume, r = 0.962; end-systolic volume, r = 0.989). Correlations of the EF and fractional area change by short-axis view methods decreased with improving image quality, with the Teichholz EF found to be most accurate with poor (r = 0.928) in contrast to good (r = 0.699) image quality.

CONCLUSIONS

With good image quality, the Simpson biplane method is the most accurate 2-dimensional method for assessing the left ventricular EF. Short-axis view methods, especially the Teichholz method yield better correlations with poor image quality. The eyeball method was unaffected by image quality.

Desacyl ghrelin prevents doxorubicin-induced myocardial fibrosis and apoptosis via the GHSR-independent pathway

Doxorubicin is an effective chemotherapeutic agent used to treat malignancies, but it causes cardiomyopathy. Preliminary evidence suggests that desacyl ghrelin might have protective effects on doxorubicin cardiotoxicity. This study examined the cellular effects of desacyl ghrelin on myocardial fibrosis and apoptosis in a doxorubicin cardiomyopathy experimental model. Adult C57BL/6 mice received an intraperitoneal injection of doxorubicin to induce cardiomyopathy, followed by 4-day treatment of saline (control) or desacyl ghrelin with or without [d-Lys3]-GHRP-6 (a growth hormone secretagogue receptor or GHSR1a antagonist). Ventricular structural and functional parameters were evaluated by transthoracic echocardiography. Molecular and cellular measurements were performed in ventricular muscle to examine myocardial fibrosis and apoptosis. Cardiac dysfunction was induced by doxorubicin, as indicated by significant decreases in ventricular fractional shortening and ejection fraction. This doxorubicin-induced cardiac dysfunction was prevented by the treatment of desacyl ghrelin no matter with or without the presence of [d-Lys3]-GHRP-6. Doxorubicin induced fibrosis (accumulated collagen deposition and increased CTGF), activated apoptosis (increased TUNEL index, apoptotic DNA fragmentation, and caspase-3 activity and decreased Bcl-2/Bax ratio), and suppressed phosphorylation status of prosurvival signals (ERK1/2 and Akt) in ventricular muscles. All these molecular and cellular alterations induced by doxorubicin were not found in the animals treated with desacyl ghrelin. Notably, the changes in the major markers of apoptosis, fibrosis, and Akt phosphorylation were found to be similar in the animals following the treatment of desacyl ghrelin with and without GHSR antagonist [d-Lys3]-GHRP-6. These findings demonstrate clearly that desacyl ghrelin protects the cardiomyocytes against the doxorubicin-induced cardiomyopathy by preventing the activation of cardiac fibrosis and apoptosis, and the effects are probably mediated through GHSR-independent mechanism.

Ventricular performance after surgery for a congenital heart defect as assessed using advanced echocardiography: from doppler flow to 3D echocardiography and speckle-tracking strain imaging

A varying degree of impairment of ventricular performance is observed over the long-term after surgery for a congenital heart defect (CHD). Impaired ventricular performance has been shown to be of prognostic value for increased risk of cardiovascular events in adult CHD patients. This emphasizes the importance of delineating the timing and cause of this postoperative impairment. Impairment of ventricular performance could develop over time as a consequence of residua, sequelae and complications of the CHD or surgical procedure. Yet, impaired ventricular performance has also been observed immediately after surgery and can persist and/or worsen over time. This postoperative impairment of ventricular performance is the focus of this review. This article provides an overview of echocardiographic techniques currently used to assess ventricular performance. Furthermore, we review current literature describing ventricular performance, as assessed using echocardiography, after correction of a CHD. In general, a decrease in ventricular performance is observed directly after surgery for CHD’s. Subsequent follow-up of ventricular performance is characterized by a varying degree of postoperative recovery. A consistent observation is the persistent impairment of right-ventricular performance after repair in several different subgroups of CHD patients ranging from ventricular septal defect repair to surgery for Tetralogy of Fallot.

[Echocardiography in emergency admissions. Recognition of cardiac low-output failure]

Detection of acute cardiac dysfunction and differential diagnosis of low cardiac output syndrome is challenging for emergency physicians. For the critical ill patient it is essential to rapidly identify the underlying disease to initiate the correct therapy and optimize patient outcome. Echocardiography is the diagnostic tool of choice for the evaluation of low cardiac output states. In the setting of the emergency department the use of focused echocardiography instead of detailed echocardiographic studies of cardiologists is appropriate and should be provided for emergency care. The differentiation in preserved versus reduced left ventricular ejection fraction as a first assessment is helpful, particularly for physicians not well trained in echocardiography. The structured and focused approach to evaluate or exclude differential diagnoses of cardiac dysfunction is the key for optimal management of acute and critically ill patients with low cardiac output.

Mitral annular plane systolic excursion (MAPSE) in shock: a valuable echocardiographic parameter in intensive care patients

BACKGROUND

Assessing left ventricular (LV) dysfunction by echocardiography in ICU patients is common. The aim of this study was to investigate mitral annular plane systolic excursion (MAPSE) in critically ill patients with shock and its relation to LV systolic and diastolic function, myocardial injury and to outcome.

METHODS

In a prospective, observational, cohort study we enrolled 50 patients with SIRS and shock despite fluid resuscitation. Transthoracic echocardiography (TTE) measuring LV function was performed within 12 hours after admission and daily for a 7-day observation period. TTE and laboratory measurements were related to 28-day mortality.

RESULTS

MAPSE on day 1 correlated significantly with LV ejection fraction (LVEF), tissue Doppler indices of LV diastolic function (é, E/é) and high-sensitive troponin T (hsTNT) (p< 0.001, p= 0.039, p= 0.009, p= 0.003 respectively) whereas LVEF did not correlate significantly with any marker of LV diastolic function or myocardial injury. Compared to survivors, non-survivors had a significantly lower MAPSE (8 [IQR 7.5-11] versus 11 [IQR 8.9-13] mm; p= 0.028). Other univariate predictors were age (p=0.033), hsTNT (p=0.014) and Sequential Organ Failure Assessment (SOFA) scores (p=0.007). By multivariate analysis MAPSE (OR 0.6 (95% CI 0.5- 0.9), p= 0.015) and SOFA score (OR 1.6 (95% CI 1.1- 2.3), p= 0.018) were identified as independent predictors of mortality. Daily measurements showed that MAPSE, as sole echocardiographic marker, was significantly lower in most days in non-survivors (p<0.05 at day 1-2, 4-6).

CONCLUSIONS

MAPSE seemed to reflect LV systolic and diastolic function as well as myocardial injury in critically ill patients with shock. The combination of MAPSE and SOFA added to the predictive value for 28-day mortality.

Assessment of left ventricular size and function during cardiac surgery. An intraoperative evaluation of six two-dimensional echocardiographic methods with real time three-dimensional echocardiography as a reference

Transesophageal echocardiography is recommended to monitor left ventricular (LV) size and function in various operations. Generally, two-dimensional (2D) methods are applied intraoperatively. The aim of this study was to compare the accuracy and feasibility of 6 commonly used 2D methods to assess LV function during surgery. LV function in 120 consecutive patients was evaluated. Real time three-dimensional transesophageal echocardiograpy (3DTEE) served as reference. End-diastolic and end-systolic volumes and ejection fraction (EF) were analyzed with Simpson's method of discs (monoplane [MP] and biplane [BP]), eyeball method, Teichholz' method, and speckle tracking (ST) methods. Furthermore, fractional area change (FAC) and peak systolic pressure rise (dP/dt) were determined. Each 2D method was evaluated regarding correlation and agreement with 3DE, intra- and interobserver variability and the time required for evaluation. Simpson BP showed the strongest correlation and best agreement with 3DE for EF (limits of agreement 3.7 ± 11.6%) and volumes. Simpson MP showed similar agreement with 3DE compared to ST (2.8 ± 14.5% vs. 2.0 ± 15.3% and 3.8 ± 14.4% vs. 1.9 ± 15.6%, respectively). Both the eyeball method and Teichholz' method showed wide limits of agreement (-1.5 ± 18.2% and 5.2 ± 22.1%, respectively). DP/dt did not correlate with 3DE. FAC and ST FAC showed similar agreement. Application of 3DE (429 ± 108 seconds) took the longest time, and the eyeball method took the shortest time (8 ± 5 seconds) for analysis. Simpson BP is the most accurate intraoperative 2D method to evaluate LV function, followed by long-axis MP evaluations. Short-axis views were less accurate but may be suited for monitoring. We do not recommend using dP/dt.

Synergistic effects of prenatal hypoxia and postnatal high-fat diet in the development of cardiovascular pathology in young rats

We have previously shown that adult offspring exposed to a prenatal hypoxic insult leading to intrauterine growth restriction (IUGR) are more susceptible to cardiovascular pathologies. Our objectives were to evaluate the interaction between hypoxia-induced IUGR and postnatal diet in the early development of cardiovascular pathologies. Furthermore, we sought to determine whether the postnatal administration of resveratrol could prevent the development of cardiovascular disorders associated with hypoxia-induced IUGR. On day 15 of pregnancy, Sprague-Dawley rats were randomly assigned to hypoxia (11.5% oxygen), to induce IUGR, or normal oxygen (control) groups. For study A, male offspring (3 wk of age) were randomly assigned a low-fat (LF, <10% fat) or a high-fat (HF, 45% fat) diet. For study B, offspring were randomized to either HF or HF+resveratrol diets. After 9 wk, cardiac and vascular functions were evaluated. Prenatal hypoxia and HF diet were associated with an increased myocardial susceptibility to ischemia. Blood pressure, in vivo cardiac function, and ex vivo vascular function were not different among experimental groups; however, hypoxia-induced IUGR offspring had lower resting heart rates. Our results suggest that prenatal insults can enhance the susceptibility to a second hit such as myocardial ischemia, and that this phenomenon is exacerbated, in the early stages of life by nutritional stressors such as a HF diet. Supplementing HF diets with resveratrol improved cardiac tolerance to ischemia in offspring born IUGR but not in controls. Thus we conclude that the additive effect of prenatal (hypoxia-induced IUGR) and postnatal (HF diet) factors can lead to the earlier development of cardiovascular pathology in rats, and postnatal resveratrol supplementation prevented the deleterious cardiovascular effects of HF diet in offspring exposed to prenatal hypoxia.

The prognostic value of left ventricular systolic function measured by tissue Doppler imaging in septic shock

INTRODUCTION

Left ventricular (LV) dysfunction is common in septic shock. Its association with the clinical outcome is still controversial. Tissue Doppler imaging (TDI) is a useful tool to quantify LV function; however, little knowledge is available about the prognostic value of these TDI variables in septic shock. Therefore, we performed this prospective study to determine the role of TDI variables in septic shock.

METHODS

Patients with septic shock in a medical intensive care unit were studied with transthoracic echocardiography with TDI within 24 hours after the onset of septic shock. Baseline clinical, laboratory, and echocardiographic variables were prospectively collected. Independent predictors of 90-day mortality were analyzed with the Cox regression model.

RESULTS

During a 20-month period, 61 patients were enrolled in the study. The 90-day mortality rate was 39%; the mean APACHE IV score was 84 (68 to 97). Compared with survivors, nonsurvivors exhibited significantly higher peak systolic velocity measured at the mitral annulus (Sa) (11.0 (9.1 to 12.5) versus 7.8 (5.5 to 9.0) cm/sec; P < 0.0001), lower PaO2/FiO2 (123 (83 to 187) versus 186 (142 to 269) mm Hg; P = 0.002], higher heart rate (120 (90 to 140) versus 103 (90 to 114) beats/min; P = 0.004], and a higher dose of norepinephrine (0.6 (0.2 to 1.0) versus 0.3 (0.2 to 0.5) μg/kg/min; P = 0.007]. In the multivariate analysis, Sa > 9 cm/sec (hazard ratio (HR), 5.559; 95% confidence interval (CI), 2.160 to 14.305; P < 0.0001), dose of norepinephrine (HR, 1.964; 95% CI, 1.338 to 2.883; P = 0.001), and PaO2/FiO2 (HR, 0.992; 95% CI, 0.984 to 0.999; P = 0.031) remain independent predictors of 90-day mortality in septic-shock patients.

CONCLUSIONS

Our study demonstrated that LV systolic function as determined by TDI, in particular, Sa, might be associated with mortality in patients with septic shock.

Assessment of left ventricular systolic function by velocity vector imaging

OBJECTIVES

To study the usefulness of a novel echocardiographic technique, velocity vector imaging (VVI) in the measurement of left ventricular ejection fraction (LVEF).

BACKGROUND

Ejection fraction measured by echocardiography forms the cornerstone in the assessment of LV systolic function. Errors in measurement of EF by routine two-dimensional echocardiography (2D ECHO) limit its utility. The VVI is a new technology which uses speckle tracking and other algorithms to track the endocardial border. This may help in more accurate assessment of EF.

METHODS

Global and regional LVEF was measured in 49 patients using VVI, 2D ECHO and radionuclide-gated single photon emission computed tomography (SPECT). Results were categorised as normal, mild, moderate, or severe LV systolic dysfunction based on American Society of ECHO classification. The results were analysed by appropriate statistical tests for correlations.

RESULTS

The mean EF was 35 ± 12.08% by VVI, 54.2 ± 19.51% by SPECT (P< 0.001 vs VVI) and 50.3 ± 8.92% by 2D ECHO (P < 0.001 vs VVI). There was weak linear positive correlation between EF measured by VVI and the other modalities (Pearson's correlation coefficient 0.577 for SPECT and 0.573 for 2D; P=0.01). The VVI systematically underestimated the EF compared to SPECT. Greater number of patients had moderate or severe LV systolic dysfunction by VVI (37; 74.5%) than by SPECT (17; 34.7%; P=0.037). We derived a correction factor to calculate SPECT EF from VVI EF as follows: EF (SPECT) = EF (VVI) × 0.9 + 21 or approximately VVI (EF) + 20.

CONCLUSION

Measurement of EF by VVI is feasible. The VVI underestimated the EF when compared to nuclear-gated SPECT in this study. The accuracy of this technology and the need for a correction factor needs to be assessed in future studies.

[Evaluation of contractility and postloading in the intensive care unit]

Cardiovascular failure is a common disorder in critical care medicine. When admitted to the ICU, patients with hemodynamic deterioration should be examined rapidly to correctly assess the main determinants of cardiovascular function (preload, afterload and contractility). This review examines the assessment of contractility and afterload involving the combined use of several hemodynamic monitors, which allows different approaches to the same problem, with a view to improving the efficiency of management and treatment in critically ill patients.

[Role of echocardiography in the hemodynamic monitorization of critical patients]

The use of echocardiography in intensive care units in shock patients allows us to measure various hemodynamic variables in an accurate and a non-invasive manner. By using echocardiography not only as a diagnostic technique but also as a tool for continuous hemodynamic monitorization, the intensivist can evaluate various aspects of shock states, such as cardiac output and fluid responsiveness, myocardial contractility, intracavitary pressures, heart-lung interaction and biventricular interdependence. However, to date there has been little guidance orienting echocardiographic hemodynamic parameters in the intensive care unit, and intensivists are usually not familiar with this tool. In this review, we describe some of the most important hemodynamic parameters that can be obtained at the patient bedside with transthoracic echocardiography in critically ill patients.

Acute effects of low doses of ethanol on left and right ventricular function in young healthy subjects

BACKGROUND

Moderate-to-high blood concentrations of ethanol acutely impair conventional echocardiographic measures of left ventricular (LV) performance, but the effects of low concentrations are unclear. This study explored the acute effects of low blood concentrations of ethanol on sensitive and load-independent indices of LV and right ventricular (RV) function.

METHODS

This is a crossover experimental study conducted in 64 young healthy volunteers. Participants were asked to drink a light dose of Italian red wine equivalent to 0.5 mg/kg of ethanol, and an equal volume of fruit juice in separate experiments. The following measurements were taken at baseline and 60 minutes after the challenges: tissue Doppler mitral annulus systolic velocity (S') and excursion (MAPSE), early diastolic velocity (E'), its ratio to late diastolic velocity (E'/A'), and the ratio of mitral-to-myocardial early diastolic velocities (E/E'); and tricuspid annulus systolic velocity (tricuspid S') and amplitude (TAPSE), early diastolic velocity (tricuspid E'), and its ratio to late diastolic velocity (tricuspid E'/A').

RESULTS

Blood ethanol concentration after wine intake was 0.48 ± 0.06 g/l. Compared with the control challenge, ethanol yielded a decrease in all measures of LV function (S', -9.7%; E', -11.2%; E'/A', -13.4%; MAPSE, -8.8%; p < 0.05 for all). Among indices of RV function, increases in tricuspid E'/A' ratio and TAPSE were observed (+24.5% and +9.0%, respectively; p < 0.05 for both).

CONCLUSIONS

Low blood concentrations of ethanol acutely impair LV function and increase some indices of RV function in young healthy individuals.

Echocardiographic evaluation during weaning from mechanical ventilation

INTRODUCTION

Echocardiographic, electrocardiographic and other cardiorespiratory variables can change during weaning from mechanical ventilation.

OBJECTIVES

To analyze changes in cardiac function, using Doppler echocardiogram, in critical patients during weaning from mechanical ventilation, using two different weaning methods: pressure support ventilation and T-tube; and comparing patient subgroups: success vs. failure in weaning.

METHODS

Randomized crossover clinical trial including patients under mechanical ventilation for more than 48 h and considered ready for weaning. Cardiorespiratory variables, oxygenation, electrocardiogram and Doppler echocardiogram findings were analyzed at baseline and after 30 min in pressure support ventilation and T-tube. Pressure support ventilation vs. T-tube and weaning success vs. failure were compared using ANOVA and Student's t-test. The level of significance was p<0.05.

RESULTS

Twenty-four adult patients were evaluated. Seven patients failed at the first weaning attempt. No echocardiographic or electrocardiographic differences were observed between pressure support ventilation and T-tube. Weaning failure patients presented increases in left atrium, intraventricular septum thickness, posterior wall thickness and diameter of left ventricle and shorter isovolumetric relaxation time. Successfully weaned patients had higher levels of oxygenation.

CONCLUSION

No differences were observed between Doppler echocardiographic variables and electrocardiographic and other cardiorespiratory variables during pressure support ventilation and T-tube. However cardiac structures were smaller, isovolumetric relaxation time was larger, and oxygenation level was greater in successfully weaned patients.

Echocardiography for hemodynamic evaluation in the intensive care unit

The use of echocardiography in the intensive care unit for patients in shock allows the accurate measurement of several hemodynamic variables in a noninvasive way. By using echocardiography as a hemodynamic monitoring tool, the clinician can evaluate several aspects of shock states, such as cardiac output and fluid responsiveness, myocardial contractility, intracavitary pressures, and biventricular interactions. However, to date, there have been few guidelines suggesting an objective hemodynamic-based examination in the intensive care unit, and most intensivists are usually not familiar with this tool. In this review, we describe some of the most important hemodynamic parameters that can be obtained at the bedside with transthoracic echocardiography.

Dynamic response of liquid-filled catheter systems for measurement of blood pressure: precision of measurements and reliability of the Pressure Recording Analytical Method with different disposable systems

PURPOSE

We aimed to compare the effects of a blood pressure transducer system specifically manufactured to limit underdamping artifacts with those of a standard system on hemodynamic parameter estimation and accuracy.

MATERIALS AND METHODS

Forty-three consecutive patients undergoing vascular surgery at the University of Florence, Italy, were included. Arterial blood pressure signal was simultaneously registered with 2 MostCare monitors, connected to the artery either by a standard transducer or a specific transducer manufactured to avoid underdamping artifacts (Resonance Over-Shoot Eliminator [R.O.S.E.]; Becton Dickinson, Becton Drive, NJ). Patients were divided into 2 groups: absence (C group) or presence (R group) of underdamping/resonance artifacts of blood pressure signal. Systolic blood pressure, cardiac index, maximal pressure/time ratio (dP/dt(MAX)), and cardiac cycle efficiency were recorded every 30 seconds for 30 minutes. A total of 2675 measurements were performed with 34.9% incidence of underdamping/resonance artifacts.

RESULTS

All hemodynamic parameters showed clinically acceptable differences in the C group; in contrast, the results differed greatly in the R group between standard and R.O.S.E. transducer (systolic blood pressure bias, 16.7 mm Hg; cardiac index bias, 0.24 L min(-1) m(-2); dP/dt(MAX) bias, 0.92 mm Hg/ms; cardiac cycle efficiency bias, 0.018 units).

CONCLUSIONS

Underdamping/resonance artifacts frequently affect blood pressure measurement in operating rooms and intensive care units and cause severe overestimation of systolic blood pressure and incorrect estimation of hemodynamic parameters when the pulse contour method is used.

Quantitative analysis of left ventricular function as a tool in clinical research. Theoretical basis and methodology

The usefulness the left ventricular ejection fraction as a surrogate endpoint in clinical trials has been confirmed by numerous studies. However, if this approach is to be applied successfully, images must be acquired in a rigorously controlled manner, and it is advisable to use measurement units that have been specifically developed for quantitative analysis of the imaging parameters obtained with current imaging techniques. This review summarizes what is now known about the left ventricular ejection fraction and left ventricular volumes, discusses the importance of measurement units in image analysis, and describes the different imaging techniques available. Finally, there is a discussion of how to select the best imaging technique for specific clinical applications.