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Biomedical subjects

Hendrikus H M Korsten

Publications and source records attributed to Hendrikus H M Korsten.

6 recordsLinked to original sources
PubMed2006

Relation of isovolumic times after cardiac resynchronization therapy to improvement in exercise capacity.

Isovolumic times (IVTs) comprise a determinant of exercise capacity in cardiomyopathy. We postulated that an increase in exercise capacity after cardiac resynchronization therapy (CRT) might be related to a more efficient cardiac cycle due to decreasing IVTs and increased filling times. According to standard selection criteria, a CRT device was implanted in 52 patients (37 men; 69 +/- 8 years) with a QRS duration of 174 +/- 30 ms. The etiology was ischemic in 22 and idiopathic in 30 patients. A 6-minute walking test (MWT) and echocardiographic Doppler were performed before and 3 and 6 months after CRT. Timing cycles were obtained with echocardiographic Doppler. An improvement in MWT by >15% (responders) after 6 months of CRT was observed in 46% of patients. The MWT was moderately correlated with baseline time intervals (IVT r = -0.44, filling time r = 0.52), but not to baseline left ventricular ejection fraction (r = -0.06). However, change in the MWT after 3 and 6 months was best related to changes in IVT (r = -0.66 and -0.68, respectively). Receiver-operating characteristic curve analysis of baseline IVT showed that an IVT >29% predicted exercise response with a positive predictive value of 89% and a negative predictive value of 77%. In conclusion, improvement in exercise tolerance after CRT is associated with a decrease in prolonged IVT. Baseline IVT might be used as an adjunctive parameter for selecting symptomatic responders to CRT.

Aged↗
PubMed2006

Quantification in echocardiography.

Until recently, more than 2200 Swan Ganz catheters were used annually in the operating rooms (OR) and intensive care unit (ICU) of the Catharina Hospital in Eindhoven, The Netherlands. After cardiologists who were specialists in echocardiography (ECHO) trained anesthesiologists in ECHO, the need for these catheters in cardiac and noncardiac surgery was reduced. Initially intended as a local teaching project, an ECHO teaching compact disk (CD) was produced during the training and distributed later worldwide, thanks to a positive review in a major anesthesiology publication. By reducing the number of Swan Ganz catheters, the hospital could finance and acquire two echocardiography machines for the OR and ICU. The availability of these machines resulted in a further reduction of the number of Swan Ganz catheters. However, the need for quantification (eg, measurements of cardiac output) remained. During the creation of the ECHO teaching CD, the idea was born to apply indicator-dilution principles on injected echo contrast. This study was performed in cooperation with the Signal Processing Department of the Eindhoven University of Technology. Advanced signal processing and modelling were used to develop algorithms to enable quantification of intrapulmonary blood volume, ejection-fraction, and flow from the transesophageal echocardiography approach. These quantitative measurements, which can be performed on an outpatient basis, may become a real asset in cardiology, anesthesiology, and intensive care.

Algorithms↗
PubMed2005

Cardiac image segmentation for contrast agent videodensitometry.

Indicator dilution techniques are widely used in the intensive care unit and operating room for cardiac parameter measurements. However, the invasiveness of current techniques represents a limitation for their clinical use. The development of stable ultrasound contrast agents allows new applications of the indicator dilution method. Ultrasound contrast agent dilutions permit an echographic noninvasive measurement of cardiac output, ejection fraction, and blood volumes. The indicator dilution curves are measured by videodensitometry of specific regions of interest and processed for the cardiac parameter assessment. Therefore, the major indicator dilution imaging issue is the detection of proper contrast videodensitometry regions that maximize the signal-to-noise ratio of the measured indicator dilution curves. This paper presents an automatic contour detection algorithm for indicator dilution videodensitometry. The algorithm consists of a radial filter combined with an outlier correction. It maximizes the region of interest by excluding cardiac structures that act as interference to the videodensitometric analysis. It is fast, projection independent, and allows the simultaneous detection of multiple contours in real time. The system is compared to manual contour definition on both echographic and magnetic resonance images.

Algorithms↗
PubMed2005

Identification of ultrasound contrast agent dilution systems for ejection fraction measurements.

Left ventricular ejection fraction is an important cardiac-efficiency measure. Standard estimations are based on geometric analysis and modeling; they require time and experienced cardiologists. Alternative methods make use of indicator dilutions, but they are invasive due to the need for catheterization. This study presents a new minimally invasive indicator dilution technique for ejection fraction quantification. It is based on a peripheral injection of an ultrasound contrast agent bolus. Left atrium and left ventricle acoustic intensities are recorded versus time by transthoracic echocardiography. The measured curves are corrected for attenuation distortion and processed by an adaptive Wiener deconvolution algorithm for the estimation of the left ventricle impulse response, which is interpolated by a monocompartment exponential model for the ejection fraction assessment. This technique measures forward ejection fraction, which excludes regurgitant volumes. The feasibility of the method was tested on a group of 20 patients with left ventricular ejection fractions going from 10% to 70%. The results are promising and show a 0.93 correlation coefficient with echographic bi-plane ejection fraction measurements. A more extensive validation as well as an investigation on the method applicability for valve insufficiency and right ventricular ejection fraction quantification will be an object of future study.

Algorithms↗
PubMed2004

Approaches for creating computer-interpretable guidelines that facilitate decision support.

During the last decade, studies have shown the benefits of using clinical guidelines in the practice of medicine. Although the importance of these guidelines is widely recognized, health care organizations typically pay more attention to guideline development than to guideline implementation for routine use in daily care. However, studies have shown that clinicians are often not familiar with written guidelines and do not apply them appropriately during the actual care process. Implementing guidelines in computer-based decision support systems promises to improve the acceptance and application of guidelines in daily practice because the actions and observations of health care workers are monitored and advice is generated whenever a guideline is not followed. Such implementations are increasingly applied in diverse areas such as policy development, utilization management, education, clinical trials, and workflow facilitation. Many parties are developing computer-based guidelines as well as decision support systems that incorporate these guidelines. This paper reviews generic approaches for developing and implementing computer-based guidelines that facilitate decision support. It addresses guideline representation, acquisition, verification and execution aspects. The paper describes five approaches (the Arden Syntax, GuideLine Interchange Format (GLIF), PROforma, Asbru and EON), after the approaches are compared and discussed.

Artificial Intelligence↗