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Martijn S Dirksen

Publications and source records attributed to Martijn S Dirksen.

13 recordsLinked to original sources
PubMed2005

Cardiac multidetector-row computed tomography in patients with unstable angina.

Ideally, information on coronary artery stenosis and left ventricular (LV) function is obtained in patients who have unstable angina to allow optimal risk stratification. The value of multidetector-row computed tomography (MDCT) was evaluated for a simultaneous assessment of coronary artery disease and global/regional LV function using a single acquisition. Twenty-five patients who had unstable angina underwent a single multidetector-row computed tomographic acquisition using a 4-slice multidetector-row computed tomographic system. Based on retrospective electrocardiographic gating, images and cine movies were reconstructed, which allowed 2 independent observers to analyze the 9 major coronary artery segments and global/regional LV function. Conventional angiography (with quantitative analysis) and echocardiography served as standards of reference, which were performed </=2 +/- 2.7 days and </=3 hours, respectively, after multidetector-row computed tomographic investigations. Sensitivity, specificity, positive and negative predictive values, and correlations were calculated. Of 225 coronary artery segments, 182 (81%) were assessable by MDCT. Significant (>/=50%) coronary artery stenosis was detected with sensitivities, specificities, and positive and negative predictive values of 95%, 91%, 85%, and 97% for observer 1 and 89%, 87%, 79%, and 94% for observer 2, respectively; the interobserver kappa value was 0.73. MDCT showed excellent agreement with echocardiography for regional wall motion (90%; kappa = 0.88) and LV ejection fraction (correlation 0.95%, mean difference 0.7 +/- 3.9). Thus, MDCT can simultaneously assess coronary artery disease and LV function in patients who have unstable angina. High accuracies in excluding significant coronary artery disease and in confirming normal LV function were observed, suggesting potential clinical use for screening of patients who present with symptoms of unstable angina.

Angina, Unstable↗
PubMed2005

Multislice computed tomography versus intracardiac echocardiography to evaluate the pulmonary veins before radiofrequency catheter ablation of atrial fibrillation: a head-to-head comparison.

OBJECTIVES: The purpose of this study was to perform a head-to-head comparison between multislice computed tomography (MSCT) and intracardiac echocardiography (ICE). BACKGROUND: Different imaging techniques have been used to visualize the pulmonary veins (PV) before radiofrequency ablation of atrial fibrillation. METHODS: The PV and their atrial insertion were evaluated in 42 patients (35 men, 49 +/- 9 years) admitted for ablation of PV ostia. Ostia were measured in two directions (anterior-posterior and superior-inferior) with MSCT. Two-dimensional (2-D) measurements of PV ostia were performed with ICE. Results were compared, considering MSCT as the gold standard. Venous ostium indexes were calculated by dividing MSCT measurements in the anterior-posterior direction and the superior-inferior direction. RESULTS: Common ostia of left PV were observed in 33 (79%) patients with MSCT and 31 (74%) patients with ICE. Common ostia of right PV were observed in 13 (31%) and 16 (38%) patients, respectively. Additional PV were observed in 13 (31%) patients with MSCT and in 7 (17%) patients with ICE. Ostial diameters by MSCT in the anterior-posterior direction were similar to 2-D measurements by ICE. By contrast, diameters by MSCT in the superior-inferior direction were significantly larger than 2-D diameters measured with ICE. Venous ostium indexes were 0.77 +/- 0.18 and 0.90 +/- 0.15 (p < 0.01) for left and right PV respectively, indicating an oval shape of particularly left PV ostia. CONCLUSIONS: Variation in PV anatomy is frequently observed with both techniques. The sensitivity for detection of additional branches is higher for MSCT. Results of measurements of PV ostia suggest an underestimation of ostial size by ICE. Three-dimensional imaging techniques, such as MSCT, are required to demonstrate an oval shape of PV ostia.

Adult↗
PubMed2005

Atrial fibrillation: multi-detector row CT of pulmonary vein anatomy prior to radiofrequency catheter ablation--initial experience.

PURPOSE: To evaluate multi-detector row computed tomographic (CT) depiction of pulmonary veins to provide a road map for radiofrequency catheter ablation. MATERIALS AND METHODS: For patients, institutional review board (IRB) approval was not required, and consent was obtained for treatment. Control subjects were part of an IRB-approved research protocol at the institution, in which they had consented to participate. Multi-detector row CT was performed in 23 patients (17 men, six women; mean age, 48 years +/- 11 [standard deviation]) with atrial fibrillation who were admitted for isolation of pulmonary veins by means of radiofrequency catheter ablation. Pulmonary vein anatomy was evaluated, and diameters of pulmonary vein ostia were measured. To determine the shape of ostia, a venous ostium index was calculated for all veins by dividing anterior-posterior measurements by superior-inferior measurements. Results were compared with those in a control group of 11 patients (eight men, three women; mean age, 56 years +/- 11) without atrial fibrillation. Images were evaluated by two observers in consensus. RESULTS: Pulmonary veins additional to the four main veins were found in seven (30%) of 23 patients. Common ostia of left and right pulmonary veins were detected in 19 (83%) and nine (39%) patients, respectively. Early branching occurred more often with right than with left veins (19 [83%] vs three [13%] cases, P <.05) in both patients and control subjects. Anterior-posterior diameter of ostia was 12.8 mm +/- 3.3 for left veins, 16.2 mm +/- 3.8 for right veins, and 18.8 mm +/- 7.7 and 28.7 mm +/- 5.1 for left and right common ostia, respectively. Ostia of right pulmonary veins were more round than were ostia of left pulmonary veins (venous ostium index in patients, 0.91 +/- 0.21 vs 0.75 +/- 0.17, P <.05; in control subjects, 0.93 +/- 0.12 vs 0.82 +/- 0.17, P <.05). The CT data were used to determine ablation strategy and guide catheters during radiofrequency ablation. CONCLUSION: Multi-detector row CT provides a valuable road map for pulmonary vein anatomy prior to radiofrequency catheter ablation. Variations in number and insertion of pulmonary veins were observed in a considerable number of patients and control subjects.

Adult↗
PubMed2004

Long-term survival in a case of unoperated single ventricle.

We report the MR appearance of single double-inlet left ventricle in a 57-year-old woman who did not undergo surgical intervention. The case shows the rare occurrence of spontaneous palliation that allows a good quality of life with good functional capacity without surgical correction in this complex congenital cardiac anomaly. Only 10 cases of unoperated single ventricles in patients older than 50 years have been reported so far. This is the first report focused on the value of MRI findings for the comprehensive evaluation of these patients.

Female↗
PubMed2004

Coronary stent imaging with multidetector row computed tomography.

Multidetector row Computed Tomography (MDCT) is developing rapidly as a potential non-invasive imaging method for the direct visualization of coronary arteries in patients presenting with suspected coronary artery disease. Recent technical improvements have led to improved spatial and temporal resolution and may even allow evaluation of coronary stents, which has remained difficult due to the small diameter and radio-opaque material. We describe two cases, a 65- and a 72-year old patient. Both patients had previously undergone percutaneous transluminal coronary angioplasty in combination with stent placement and were re-admitted to our hospital with recurrent angina. MDCT was performed prior to or after coronary angiography in order to assess stent patency non-invasively.

Aged↗
PubMed2003

Toward comparability of coronary magnetic resonance angiography: proposal for a standardized quantitative assessment.

A method is proposed for the quantitative assessment of coronary magnetic resonance angiography (MRA) acquisitions. The method is based on four parameters: signal-to-noise ratio (SNR); contrast-to-noise ratio (CNR); vessel length; and vessel-edge definition. A pig model (n=7) was used to illustrate the proposed quantitative analysis method. Three-dimensional gradient-echo coronary MRA was performed with and without exogenous contrast enhancement using a gadolinium-based blood-pool contrast agent (Vistarem, Guerbet, Aulnay-Sous-Bois, France). The acquired images could be well differentiated based on the four parameters. The SNR was calculated as 9.0+/-1.4 vs 10.4+/-2.1, the CNR as 6.2+/-0.8 vs 8.2+/-0.9, the vessel length as 48.2+/-11.6 vs 86.5+/-13.8 mm, and the vessel-edge definition as 4.9+/-1.5 vs 7.7+/-3.4. Different coronary MRA techniques can be evaluated objectively with the combined use of SNR, CNR, vessel length, and vessel-edge parameters.

Animals↗
PubMed2003

Improved MR coronary angiography with use of a new rapid clearance blood pool contrast agent in pigs.

PURPOSE: To evaluate in an animal model the potential for clinical use of a new rapid clearance blood pool contrast agent to improve free-breathing and breath-hold magnetic resonance (MR) coronary angiography. MATERIALS AND METHODS: Free-breathing and breath-hold MR coronary angiography were performed in a pig model (n = 9) (a) without use of a contrast agent; (b) with P792 (Guerbet Research, Aulnay Sous Bois, France), a monodisperse monogadolinated macromolecular compound that acts as a blood pool contrast agent with rapid clearance properties; and (c) with an extravascular gadolinium-based contrast agent. This resulted in six imaging options, which were compared in terms of contrast-to-noise ratio (CNR), signal-to-noise ratio, and vessel length measurements by using the Student t test. RESULTS: Use of P792 improved CNR and visible vessel length significantly with both MR respiratory motion correction approaches, as compared with nonenhanced MR imaging (P <.05). CNR was improved by 76% (from 5.0 to 8.6) with the free-breathing approach and by 34% (from 6.2 to 8.2) with the breath-hold approach. Visible vessel length was increased by 27% (from 79.7 to 99.2 mm) with the free-breathing approach and by 90% (from 48.2 to 86.5 mm) with the breath-hold approach. The P792-enhanced free-breathing approach allowed more distal visualization of the coronary arteries than did the P792-enhanced breath-hold approach (P <.05). Use of the extravascular contrast agent did not improve image quality significantly when compared with that of nonenhanced MR images. CONCLUSION: Use of P792 improves coronary artery MR imaging in conjunction with free-breathing and breath-hold approaches.

Animals↗
PubMed2003

Three-dimensional navigator coronary MRA with the aid of a blood pool agent in pigs: improved image quality with inclusion of the contrast agent first-pass.

PURPOSE: To evaluate the effect of including the first-pass of a blood pool agent (BPA) on the image quality of three-dimensional navigator coronary MRA. MATERIALS AND METHODS: A pig model was used to perform: 1) T1 simulation of the BPA, based on actual blood samples, and 2) BPA-enhanced three-dimensional navigator coronary MRA, with or without inclusion of the first-pass of the BPA. The acquisitions with inclusion of the first-pass were timed with the use of a test bolus. The acquisitions without first-pass were started one minute after bolus injection (steady-state). A gradient echo acquisition technique with centric k-space sampling was applied. Comparison of both acquisitions was based on determination of contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and vessel length. RESULTS: T1 simulation shows a distinct T1 reduction during first-pass (to a level below 50 msec), increasing to 190 msec during steady-state. Images obtained with first-pass inclusion showed improved CNR (8.6 +/- 1.7 vs. 4.5 +/- 1.8), SNR (11.9 +/- 1.6 vs. 7.4 +/- 2.0), and vessel length (99.2 +/- 10.9 mm vs. 60.5 +/- 21.8 mm) as compared to the acquisitions during steady-state only (all: P< 0.05). CONCLUSION: The image quality of three-dimensional navigator coronary MRA combined with a gadolinium BPA in pigs is improved when starting the image acquisition during first-pass of the bolus.

Animals↗
PubMed2003

Coronary magnetic resonance angiography: technical developments and clinical applications.

Magnetic resonance angiography (MRA) is a promising method for noninvasive coronary artery imaging. The interesting features of coronary MRA are its non-invasive nature, the absence of ionizing radiation, and the possibility of imaging the coronary arteries without exogenous contrast. Moreover, three-dimensional volume information and tomographic image planes in any direction can be obtained. The current review presents an overview of the recent technical developments of coronary MRA and the potential clinical applications. New MR techniques, such as parallel image acquisition, spiral imaging, steady-state free precession and the introduction of blood pool contrast agents may result in more efficient data acquisition. After implementation of these fast techniques, coronary MRA may be integrated in a comprehensive cardiac exam.

Coronary Artery Disease↗