Prediction of postoperative patient deterioration and unanticipated intensive care unit admission using perioperative factors.

BACKGROUND AND OBJECTIVES: Currently, no evidence-based criteria exist for decision making in the post anesthesia care unit (PACU). This could be valuable for the allocation of postoperative patients to the appropriate level of care and beneficial for patient outcomes such as unanticipated intensive care unit (ICU) admissions. The aim is to assess whether the inclusion of intra- and postoperative factors improves the prediction of postoperative patient deterioration and unanticipated ICU admissions. METHODS: A retrospective observational cohort study was performed between January 2013 and December 2017 in a tertiary Dutch hospital. All patients undergoing surgery in the study period were selected. Cardiothoracic surgeries, obstetric surgeries, catheterization lab procedures, electroconvulsive therapy, day care procedures, intravenous line interventions and patients under the age of 18 years were excluded. The primary outcome was unanticipated ICU admission. RESULTS: An unanticipated ICU admission complicated the recovery of 223 (0.9%) patients. These patients had higher hospital mortality rates (13.9% versus 0.2%, p<0.001). Multivariable analysis resulted in predictors of unanticipated ICU admissions consisting of age, body mass index, general anesthesia in combination with epidural anesthesia, preoperative score, diabetes, administration of vasopressors, erythrocytes, duration of surgery and post anesthesia care unit stay, and vital parameters such as heart rate and oxygen saturation. The receiver operating characteristic curve of this model resulted in an area under the curve of 0.86 (95% CI 0.83-0.88). CONCLUSIONS: The prediction of unanticipated ICU admissions from electronic medical record data improved when the intra- and early postoperative factors were combined with preoperative patient factors. This emphasizes the need for clinical decision support tools in post anesthesia care units with regard to postoperative patient allocation.

On the value of MRI for improved understanding of cuff-based oscillometric measurements.

Blood pressure (BP) is a key parameter in critical care and in cardiovascular disease management. BP is typically measured via cuff-based oscillometry. This method is highly inaccurate in hypo- and hypertensive patients. Improvements are difficult to achieve because oscillometry is not yet fully understood; many assumptions and uncertainties exist in models describing the process by which arterial pulsations become expressed within the cuff signal. As a result, it is also difficult to estimate other parameters via the cuff such as arterial stiffness, cardiac output and pulse wave velocity (PWV)-BP calibration. Many research modalities have been employed to study oscillometry (ultrasound, computer simulations, ex-vivo studies, measurement of PWV, mechanical analysis). However, uncertainties remain; additional investigation modalities are needed. In this study, we explore the extent to which MRI can help investigate oscillometric assumptions. Four healthy volunteers underwent a number of MRI scans of the upper arm during cuff inflation. It is found that MRI provides a novel perspective over oscillometry; the artery, surrounding tissue, veins and the cuff can be simultaneously observed along the entire length of the upper arm. Several existing assumptions are challenged: tissue compression is not isotropic, arterial transmural pressure is not uniform along the length of the cuff and propagation of arterial pulsations through tissue is likely impacted by patient-specific characteristics (vasculature position and tissue composition). Clinical Relevance- The cuff interaction with the vasculature is extremely complex; existing models are oversimplified. MRI is a valuable tool for further development of cuff-based physiological measurements.

Quality Improvement in the Preoperative Evaluation: Accuracy of an Automated Clinical Decision Support System to Calculate CHA2DS2-VASc Scores.

Background and Objectives: Clinical decision support systems are advocated to improve the quality and efficiency in healthcare. However, before implementation, validation of these systems needs to be performed. In this evaluation we tested our hypothesis that a computerized clinical decision support system can calculate the CHA2DS2-VASc score just as well compared to manual calculation, or even better and more efficiently than manual calculation in patients with atrial rhythm disturbances. Materials and Methods: In n = 224 patents, we calculated the total CHA2DS2-VASc score manually and by an automated clinical decision support system. We compared the automated clinical decision support system with manually calculation by physicians. Results: The interclass correlation between the automated clinical decision support system and manual calculation showed was 0.859 (0.611 and 0.931 95%-CI). Bland-Altman plot and linear regression analysis shows us a bias of -0.79 with limit of agreement (95%-CI) between 1.37 and -2.95 of the mean between our 2 measurements. The Cohen's kappa was 0.42. Retrospective analysis showed more human errors than algorithmic errors. Time it took to calculate the CHA2DS2-VASc score was 11 s per patient in the automated clinical decision support system compared to 48 s per patient with the physician. Conclusions: Our automated clinical decision support system is at least as good as manual calculation, may be more accurate and is more time efficient.

The learning curve for ultrasound-guided peripheral intravenous cannulation in adults: a multicenter study.

AIMS: To lower the threshold for applying ultrasound (US) guidance during peripheral intravenous cannulation, nurses need to be trained and gain experience in using this technique. The primary outcome was to quantify the number of procedures novices require to perform before competency in US-guided peripheral intravenous cannulation was achieved. MATERIALS AND METHODS: A multicenter prospective observational study, divided into two phases after a theoretical training session: a hands-on training session and a supervised life-case training session. The number of US-guided peripheral intravenous cannulations a participant needed to perform in the life-case setting to become competent was the outcome of interest. Cusum analysis was used to determine the learning curve of each individual participant. RESULTS: Forty-nine practitioners participated and performed 1855 procedures. First attempt cannulation success was 73% during the first procedure, but increased to 98% on the fortieth attempt (p<0.001). The overall first attempt success rate during this study was 93%. The cusum learning curve for each practitioner showed that a mean number of 34 procedures was required to achieve competency. Time needed to perform a procedure successfully decreased when more experience was achieved by the practitioner, from 14±3 minutes on first proce-dure to 3±1 minutes during the fortieth procedure (p<0.001). CONCLUSIONS: Competency in US-guided peripheral intravenous cannulation can be gained after following a fixed educational curriculum, resulting in an increased first attempt cannulation success as the number of performed procedures increased.

Validation of Heart Rate Extracted From Wrist-Based Photoplethysmography in the Perioperative Setting: Prospective Observational Study.

BACKGROUND: Measurement of heart rate (HR) through an unobtrusive, wrist-worn optical HR monitor (OHRM) could enable earlier recognition of patient deterioration in low acuity settings and enable timely intervention. OBJECTIVE: The goal of this study was to assess the agreement between the HR extracted from the OHRM and the gold standard 5-lead electrocardiogram (ECG) connected to a patient monitor during surgery and in the recovery period. METHODS: In patients undergoing surgery requiring anesthesia, the HR reported by the patient monitor's ECG module was recorded and stored simultaneously with the photopletysmography (PPG) from the OHRM attached to the patient's wrist. The agreement between the HR reported by the patient's monitor and the HR extracted from the OHRM's PPG signal was assessed using Bland-Altman analysis during the surgical and recovery phase. RESULTS: A total of 271.8 hours of data in 99 patients was recorded simultaneously by the OHRM and patient monitor. The median coverage was 86% (IQR 65%-95%) and did not differ significantly between surgery and recovery (Wilcoxon paired difference test P=.17). Agreement analysis showed the limits of agreement (LoA) of the difference between the OHRM and the ECG HR were within the range of 5 beats per minute (bpm). The mean bias was -0.14 bpm (LoA between -3.08 bpm and 2.79 bpm) and -0.19% (LoA between -5 bpm to 5 bpm) for the PPG- measured HR compared to the ECG-measured HR during surgery; during recovery, it was -0.11 bpm (LoA between -2.79 bpm and 2.59 bpm) and -0.15% (LoA between -3.92% and 3.64%). CONCLUSIONS: This study shows that an OHRM equipped with a PPG sensor can measure HR within the ECG reference standard of -5 bpm to 5 bpm or -10% to 10% in the perioperative setting when the PPG signal is of sufficient quality. This implies that an OHRM can be considered clinically acceptable for HR monitoring in low acuity hospitalized patients.

Modulation of Pulse Propagation and Blood Flow via Cuff Inflation-New Distal Insights.

In standard critical care practice, cuff sphygmomanometry is widely used for intermittent blood pressure (BP) measurements. However, cuff devices offer ample possibility of modulating blood flow and pulse propagation along the artery. We explore underutilized arrangements of sensors involving cuff devices which could be of use in critical care to reveal additional information on compensatory mechanisms. In our previous work, we analyzed the response of the vasculature to occlusion perturbations by means of observations obtained non-invasively. In this study, our aim is to (1) acquire additional insights by means of invasive measurements and (2) based on these insights, further develop cuff-based measurement strategies. Invasive BP experimental data is collected downstream from the cuff in two patients monitored in the OR. It is found that highly dynamic processes occur in the distal arm during cuff inflation. Mean arterial pressure increases in the distal artery by 20 mmHg, leading to a decrease in pulse transit time by 20 ms. Previous characterizations neglected such distal vasculature effects. A model is developed to reproduce the observed behaviors and to provide a possible explanation of the factors that influence the distal arm mechanisms. We apply the new findings to further develop measurement strategies aimed at acquiring information on pulse arrival time vs. BP calibration, artery compliance, peripheral resistance, artery-vein interaction.

The impact of the catheter to vein ratio on peripheral intravenous cannulation success, a post-hoc analyses.

BACKGROUND: Intravenous cannulation is usually the first procedure performed in modern healthcare, although establishing peripheral intravenous access is challenging in some patients. The impact of the ratio between venous diameter and the size of the inserted catheter (catheter to vein ratio, CVR) on the first attempt success rate can be of added value in clinical. This study tries to give insight into the consideration that must be made when selecting the target vein and the type of catheter, and proved the null hypothesis that an optimal CVR would not be associated with increased first attempt cannulation success. METHODS: This was a post-hoc analyses on adult patients admitted for peripheral intravenous cannulation. Intravenous cannulation was performed according to practice guidelines, by applying the traditional landmark approach. The CVR was calculated afterwards for each individual patient by dividing the external diameter of the inserted catheter by the diameter of the target vein, which was multiplied by 100%. RESULTS: In total, 610 patients were included. The median CVR was 0.39 (0.15) in patients with a successful first attempt, whereas patients with an unsuccessful first attempt had a median CVR of 0.55 (0.20) (P<0.001). The optimal cut-off point of the CVR was 0.41. First attempt cannulation was successful in 92% of patients with a CVR<0.41, whereas as those with a CVR>0.41 had a first attempt success rate of 65% (P<0.001). CONCLUSION: This first introduction of the CVR in relation to cannulation success should be further investigated. Although, measuring the venous diameter or detection of a vein with a specific diameter prior to cannulation may increase first attempt cannulation success.

Comparison of the dilatory effect of three strategies on peripheral veins of the upper extremity in adults.

BACKGROUND: Dilated veins are associated with increased success of peripheral intravenous cannulation, due to their improved visibility and palpability. We compared three strategies to achieve venodilation (tourniquet, electrical stimulation, or a combined strategy) on increase in venous size. METHODS: A total of 54 volunteers participated in this cross-over observational study with healthy adults, measuring venous cross-sectional area and diameter at six different sites of the upper extremity. Measurements were performed with ultrasound after performing any dilation strategy and compared with non-dilated venous size. An increased cross-sectional area of 25 square millimeters was denoted as clinically relevant, which was detected with paired t-test, Wilcoxon signed rank test, or ANOVA. RESULTS: The cephalic vein was the greatest at all sites (t=12.43, df=39, P<0.001 for the cross-sectional area), but the largest increase in venous size was obtained in the basilic vein (t=12.11, df=39, P<0.001 for the cross-sectional area). The largest increase in venous size was obtained after electrical stimulation followed by tourniquet application at all measurement sites. The basilic vein increased by with 44% in cross-sectional area and 21% in diameter, which were 37% and 17% for the cross-sectional area and diameter of the cephalic vein. CONCLUSIONS: In general, the largest sized veins are situated in the upper arm, of which the cephalic vein has the largest cross-sectional area and diameter. The combination of electrical stimulation followed by tourniquet application resulted in the greatest increase in venous size and is therefore considered as the most effective to improve peripheral intravenous cannulation success.

Clinical Decision Support System-Assisted Pharmacy Intervention Reduces Feeding Tube-Related Medication Errors in Hospitalized Patients: A Focus on Medication Suitable for Feeding-Tube Administration.

BACKGROUND: Administering medication through an enteral feeding tube (FT) is a frequent cause of errors resulting in increased morbidity and cost. Studies on interventions to prevent these errors in hospitalized patients, however, are limited. OBJECTIVE: The objective was to study the effect of a clinical decision support system (CDSS)-assisted pharmacy intervention on the incidence of FT-related medication errors (FTRMEs) in hospitalized patients. METHODS: A pre-post intervention study was conducted between October 2014 and May 2015 in Catharina Hospital, the Netherlands. Patients who were admitted to the wards of bowel and liver disease, oncology, or neurology; using oral medication; and had an enteral FT were included. Preintervention patients were given care as usual. The intervention consisted of implementing a CDSS-assisted pharmacy check while also implementing standard operating procedures and educating personnel. An FTRME was defined as the administration of inappropriate medication through an enteral FT. The incidence was expressed as the number of FTRMEs per medication administration. Multivariate Poisson regression was used to calculate the incidence ratio (IR) comparing both phases. RESULTS: Eighty-one patients were included, 38 during preintervention and 43 during the intervention phase. Incidence of FTRMEs in the preintervention phase was 0.15 (95% CI, 0.07-0.23) vs 0.02 (95% CI, 0.00-0.04) in the intervention phase, resulting in an adjusted IR of 0.13 (95% CI, 0.10-0.18). DISCUSSION: Incidence of FTRMEs, as well as the IR, is comparable to previous studies. CONCLUSION: The intervention resulted in a substantial reduction in the incidence of FTRMEs.

Identify Facilitators and Challenges in Computerized Checklist Implementation.

Safety checklists have been considered as a promising tool for improving patient safety for decades. Computerized checklists have better performance compared with paper-based checklists, though there are barriers to their adoption. Given previous literature, it is still unclear what assists implementations and their challenges. To address this issue, this paper summarizes the implementation of two successful computerized checklist implementations in two countries for two different clinical scenarios and analyzes their facilitators and challenges.

Clinical use of electrical stimulation with the Veinplicity® device and its effect on the first attempt success rate of peripheral intravenous cannulation: A non-randomized clinical trial.

BACKGROUND: Peripheral intravenous cannulation is one of the most frequently performed medical procedures. Venodilation, which can be achieved with different techniques, is an important factor for first attempt success. The objective of this study was to compare the first attempt success rates upon peripheral intravenous cannulation after applying a tourniquet, with venous dilation by electrical stimulation using the Veinplicity® device, or a combination of both techniques, in participants at moderate risk of a difficult peripheral intravenous access. METHODS: This non-randomized clinical trial was carried out in adult patients divided into three parallel study groups, consisting of cannulation with a tourniquet (control group), cannulation after electrical stimulation without using a tourniquet (intervention group 1), and cannulation after applying electrical stimulation followed by the application of a tourniquet on the selected upper extremity (intervention group 2). The primary outcome was the first attempt success rate of peripheral intravenous catheter placement. RESULTS: In all, 141 participants were included in this study, with an overall success rate of 86%. Success rates of 78%, 88%, and 92% were observed in the control group, intervention group 1, and intervention group 2, respectively (p = 0.25, χ2 = 2.771, df = 2). A higher first attempt success rate was detected in participants in intervention group 2, when compared to the control group (p = 0.04, χ2 = 4.63, df = 1). CONCLUSION: Increase in first attempt success was clinically relevant when electrical stimulation with the Veinplicity® device was combined with the application of a tourniquet in participants at moderate risk of a difficult peripheral intravenous access.

The Modified A-DIVA Scale as a Predictive Tool for Prospective Identification of Adult Patients at Risk of a Difficult Intravenous Access: A Multicenter Validation Study.

Peripheral intravenous cannulation is the most common invasive hospital procedure but is associated with a high failure rate. This study aimed to improve the A-DIVA scale (Adult Difficult Intra Venous Access Scale) by external validation, to predict the likelihood of difficult intravenous access in adults. This multicenter study was carried out throughout five hospitals in the Netherlands. Adult participants were included, regardless of their indication for intravenous access, demographics, and medical history. The main outcome variable was defined as failed peripheral intravenous cannulation on the first attempt. A total of 3587 participants was included in this study. The first attempt success rate was 81%. Finally, five variables were included in the prediction model: a history of difficult intravenous cannulation, a difficult intravenous access as expected by the practitioner, the inability to detect a dilated vein by palpating and/or visualizing the extremity, and a diameter of the selected vein less than 3 millimeters. Based on a participant's individual score on the A-DIVA scale, they were classified into either a low, moderate, or high-risk group. A higher score on the A-DIVA scale indicates a higher risk of difficult intravenous access. The five-variable additive A-DIVA scale is a reliable and generalizable predictive scale to identify patients at risk of difficult intravenous access.

Barriers to ultrasound guidance for central venous access: a survey among Dutch intensivists and anaesthesiologists.

Accumulating evidence shows that ultrasound (US) guidance improves effectiveness and safety of central venous catheter (CVC) placement. Several international guidelines therefore recommend the use of US for placement of CVCs. However, surveys show that the landmark-based technique is still widely used, while the percentage of physicians using US is increasing less than expected. The goal of this study was to investigate current practice for central venous catheterization in anaesthesiology and intensive care in the Netherlands, identify barriers for further implementation of US guidance and to evaluate whether personality traits are associated with the choice of technique. We conducted a web-based national survey, distributed among members of the Dutch societies of anaesthesiology (NVA) and intensive care (NVIC). The survey contained questions regarding physician and hospital characteristics, frequency of US use and reasons for use or non-use, as well as the NEO-FFI-3, a validated, translated questionnaire to characterize personality traits according to the 'Big Five' concept. Response rate was 22% (506/2291), of which 400 had also the personality questionnaire complete. Ultrasound guidance was used always or almost always in 68%; barriers for US use were working in a non-academic non-teaching hospital, providing cardiac anaesthesia and more years of physician experience. Reasons for not using US were perceived lack of benefit, increased procedure time, lack of US equipment and fear of loss of landmark technique skills. 13% of respondents had never experienced a complication during CVC placement, and 67% knew of a complication occurring the past year at their department. Ultrasound was thought not to be able to prevent the complication in half of these cases. Of the personality traits, only neuroticism and extraversion showed a minor positive association with US guidance. A majority of anaesthesiologists and intensivists uses US guidance for CVC placement, but a significant proportion of physicians still prefers the landmark technique. Most arguments from respondents against US guidance can be challenged. Personality traits most likely do not play a major role in the acceptance of US guidance for central venous catheterization. A potential intervention to increase US use could be formalizing local hospital policies mandating compliance with US guidance. Future research can perhaps focus on cognitive biases that currently limit more widespread use of US guidance.

Robust and semantic needle detection in 3D ultrasound using orthogonal-plane convolutional neural networks.

PURPOSE: During needle interventions, successful automated detection of the needle immediately after insertion is necessary to allow the physician identify and correct any misalignment of the needle and the target at early stages, which reduces needle passes and improves health outcomes. METHODS: We present a novel approach to localize partially inserted needles in 3D ultrasound volume with high precision using convolutional neural networks. We propose two methods based on patch classification and semantic segmentation of the needle from orthogonal 2D cross-sections extracted from the volume. For patch classification, each voxel is classified from locally extracted raw data of three orthogonal planes centered on it. We propose a bootstrap resampling approach to enhance the training in our highly imbalanced data. For semantic segmentation, parts of a needle are detected in cross-sections perpendicular to the lateral and elevational axes. We propose to exploit the structural information in the data with a novel thick-slice processing approach for efficient modeling of the context. RESULTS: Our introduced methods successfully detect 17 and 22 G needles with a single trained network, showing a robust generalized approach. Extensive ex-vivo evaluations on datasets of chicken breast and porcine leg show 80 and 84% F1-scores, respectively. Furthermore, very short needles are detected with tip localization errors of less than 0.7 mm for lengths of only 5 and 10 mm at 0.2 and 0.36 mm voxel sizes, respectively. CONCLUSION: Our method is able to accurately detect even very short needles, ensuring that the needle and its tip are maximally visible in the visualized plane during the entire intervention, thereby eliminating the need for advanced bi-manual coordination of the needle and transducer.

Pressure gradient vs. flow relationships to characterize the physiology of a severely stenotic aortic valve before and after transcatheter valve implantation.

Aims: Echocardiography and tomographic imaging have documented dynamic changes in aortic stenosis (AS) geometry and severity during both the cardiac cycle and stress-induced increases in cardiac output. However, corresponding pressure gradient vs. flow relationships have not been described. Methods and results: We recruited 16 routine transcatheter aortic valve implantations (TAVI's) for graded dobutamine infusions both before and after implantation; 0.014″ pressure wires in the aorta and left ventricle (LV) continuously measured the transvalvular pressure gradient (ΔP) while a pulmonary artery catheter regularly assessed cardiac output by thermodilution. Before TAVI, ΔP did not display a consistent relationship with transvalvular flow (Q). Neither linear resistor (median R2 0.16) nor quadratic orifice (median R2 < 0.01) models at rest predicted stress observations; the severely stenotic valve behaved like a combination. The unitless ratio of aortic to left ventricular pressures during systolic ejection under stress conditions correlated best with post-TAVI flow improvement. After TAVI, a highly linear relationship (median R2 0.96) indicated a valid valve resistance. Conclusion: Pressure loss vs. flow curves offer a fundamental fluid dynamic synthesis for describing aortic valve pathophysiology. Severe AS does not consistently behave like an orifice (as suggested by Gorlin) or a resistor, whereas TAVI devices behave like a pure resistor. During peak dobutamine, the ratio of aortic to left ventricular pressures during systolic ejection provides a 'fractional flow reserve' of the aortic valve that closely approximates the complex, changing fluid dynamics. Because resting assessment cannot reliably predict stress haemodynamics, 'valvular fractional flow' warrants study to explain exertional symptoms in patients with only moderate AS at rest.

Aligning Event Logs to Task-Time Matrix Clinical Pathways in BPMN for Variance Analysis.

Clinical pathways (CPs) are popular healthcare management tools to standardize care and ensure quality. Analyzing CP compliance levels and variances is known to be useful for training and CP redesign purposes. Flexible semantics of the business process model and notation (BPMN) language has been shown to be useful for the modeling and analysis of complex protocols. However, in practical cases one may want to exploit that CPs often have the form of task-time matrices. This paper presents a new method parsing complex BPMN models and aligning traces to the models heuristically. A case study on variance analysis is undertaken, where a CP from the practice and two large sets of patients data from an electronic medical record (EMR) database are used. The results demonstrate that automated variance analysis between BPMN task-time models and real-life EMR data are feasible, whereas that was not the case for the existing analysis techniques. We also provide meaningful insights for further improvement.

A meta-model for computer executable dynamic clinical safety checklists.

BACKGROUND: Safety checklist is a type of cognitive tool enforcing short term memory of medical workers with the purpose of reducing medical errors caused by overlook and ignorance. To facilitate the daily use of safety checklists, computerized systems embedded in the clinical workflow and adapted to patient-context are increasingly developed. However, the current hard-coded approach of implementing checklists in these systems increase the cognitive efforts of clinical experts and coding efforts for informaticists. This is due to the lack of a formal representation format that is both understandable by clinical experts and executable by computer programs. METHODS: We developed a dynamic checklist meta-model with a three-step approach. Dynamic checklist modeling requirements were extracted by performing a domain analysis. Then, existing modeling approaches and tools were investigated with the purpose of reusing these languages. Finally, the meta-model was developed by eliciting domain concepts and their hierarchies. The feasibility of using the meta-model was validated by two case studies. The meta-model was mapped to specific modeling languages according to the requirements of hospitals. RESULTS: Using the proposed meta-model, a comprehensive coronary artery bypass graft peri-operative checklist set and a percutaneous coronary intervention peri-operative checklist set have been developed in a Dutch hospital and a Chinese hospital, respectively. The result shows that it is feasible to use the meta-model to facilitate the modeling and execution of dynamic checklists. CONCLUSIONS: We proposed a novel meta-model for the dynamic checklist with the purpose of facilitating creating dynamic checklists. The meta-model is a framework of reusing existing modeling languages and tools to model dynamic checklists. The feasibility of using the meta-model is validated by implementing a use case in the system.

Noninvasive pulmonary transit time: A new parameter for general cardiac performance.

INTRODUCTION: Pulmonary transit time (PTT) assessed with contrast-enhanced ultrasound (CEUS) is a novel tool to evaluate cardiac function. PTT represents the time for a bolus of contrast to pass from the right to the left ventricle, measured according to the indicator dilution principles using CEUS. We investigated the hypothesis that PTT is a measure of general cardiac performance in patient populations eligible for cardiac resynchronization therapy (CRT). METHODS: The study population consisted of heart failure patients referred for CRT with NYHA class II-IV, left ventricular ejection fraction (LVEF)≤35% and QRS≥120 ms. CEUS, ECG, and blood were analyzed, and participants completed a quality of life questionnaire at baseline and 3 months after CRT implantation. Normalized PTT (nPTT) was calculated to compensate for the heart rate. Correlations were assessed with Pearson's or Spearman's coefficients and stratified for rhythm and NYHA class. RESULTS: The study population consisted of 94 patients (67 men) with a mean age of 70±8.9 years. (n)PTT was significantly correlated with left ventricular parameters (rs =-.487, P<.001), right ventricular parameters (r=-.282, P=.004), N-terminal pro-B-type natriuretic peptide (NT-proBNP) (rs =.475, P<.001), and quality of life (rs =.364, P<.001). Stronger significant correlations were found in patients in sinus rhythm. CONCLUSION: CEUS-derived PTT and nPTT correlate to a fair degree with measures of systolic and diastolic function, NT-pro-BNP, and quality of life. As CEUS-derived PTT can be obtained easily, noninvasively and at the bedside, it is a promising future measure of general cardiac performance.

Medical Instrument Detection in 3-Dimensional Ultrasound Data Volumes.

Ultrasound-guided medical interventions are broadly applied in diagnostics and therapy, e.g., regional anesthesia or ablation. A guided intervention using 2-D ultrasound is challenging due to the poor instrument visibility, limited field of view, and the multi-fold coordination of the medical instrument and ultrasound plane. Recent 3-D ultrasound transducers can improve the quality of the image-guided intervention if an automated detection of the needle is used. In this paper, we present a novel method for detecting medical instruments in 3-D ultrasound data that is solely based on image processing techniques and validated on various ex vivo and in vivo data sets. In the proposed procedure, the physician is placing the 3-D transducer at the desired position, and the image processing will automatically detect the best instrument view, so that the physician can entirely focus on the intervention. Our method is based on the classification of instrument voxels using volumetric structure directions and robust approximation of the primary tool axis. A novel normalization method is proposed for the shape and intensity consistency of instruments to improve the detection. Moreover, a novel 3-D Gabor wavelet transformation is introduced and optimally designed for revealing the instrument voxels in the volume, while remaining generic to several medical instruments and transducer types. Experiments on diverse data sets, including in vivo data from patients, show that for a given transducer and an instrument type, high detection accuracies are achieved with position errors smaller than the instrument diameter in the 0.5-1.5-mm range on average.