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B J Rensing

Publications and source records attributed to B J Rensing.

50 records · Page 3Linked to original sources
PubMed1991

Do stents interfere with the densitometric assessment of a coronary artery lesion?

This in vitro study was designed to assess the contribution of three currently investigated coronary stents to the densitometric measurement of a known stenosis contained within two different sized plexiglass phantoms. These studies were performed at two concentrations of the contrast agent iopamidol (50 and 100%). The calculated minimal luminal cross-sectional area values in the control phantom ranged from 0-18% higher than the theoretical values. Insertion of a stainless steel stent (Wallstent, Schneider, Zürich or Palmaz-Schatz, Johnson and Johnson, Warren, NJ) resulted in further minor increases (less than or equal to 8% in the calculated minimal luminal cross-sectional area, except in the smaller phantom filled with 50% contrast medium. The Wiktor (tantalum) stent (Medtronic, Minneapolis, MN) had the largest impact of the three stents depending on the concentration of iopamidol (100% contrast medium: 9-13% values above control; 50% contrast medium; 23-56% higher). We conclude that although densitometry may overestimate the minimal luminal cross-sectional area in stented vessels, this effect is usually minor with stainless steel stents. However, tantalum-containing stents may result in serious overestimation of lesion area, particularly if contrast is diluted or the vessel is not well filled.

Coronary Angiography↗
PubMed1991

Comparative angiographic quantitative analysis of the immediate efficacy of coronary atherectomy with balloon angioplasty, stenting, and rotational ablation.

Interventional cardiology has branched in two directions: devices that primarily dilate coronary stenoses and those that debulk coronary tissue. Presently the optimum coronary intervention has not been found. While patients are awaiting randomized trials, a comparison based on matched quantitative coronary analysis may be useful to evaluate results of new interventional techniques. Therefore we compared 51 patients undergoing atherectomy with individually matched patients who were undergoing balloon angioplasty and stenting. The lesions were matched according to location of stenosis and reference diameter. Atherectomy and stenting resulted in larger gains in minimal luminal diameter compared with conventional balloon angioplasty. The minimal luminal diameter was increased from 1.2 +/- 0.4 mm to 2.6 +/- 0.4 mm in the atherectomy group and from 1.2 +/- 0.3 mm to 1.9 +/- 0.4 mm in the angioplasty group (p less than 0.00001). Atherectomy and stenting resulted in similar gains in minimum luminal diameter (1.4 mm vs 1.3 mm, p = NS). In addition, atherectomy and stenting appear to be more effective in resisting elastic recoil because of tissue removal and an intrinsic dilating effect, respectively. In matched populations directional atherectomy and stenting appear to be more effective intracoronary interventional devices than balloon angioplasty based on the immediate results. However, atherectomy is limited in smaller coronary vessels because of its larger size.

Angioplasty, Laser↗
PubMed1991

Acute complications of percutaneous transluminal coronary angioplasty for total occlusion.

The incidence of major complications after percutaneous coronary angioplasty (PTCA) of a totally occluded artery was assessed retrospectively. A total of 1649 PTCA procedures were analyzed. After exclusion of procedures for acute myocardial infarction or total occlusion that resulted from restenosis, 90 patients were selected. Forty-four patients (49%) had stable angina and 46 (51%) had unstable angina. The estimated duration of occlusion was 87 +/- 78 days in patients with stable angina, as compared with 10 +/- 8 days in patients with unstable angina (p less than 0.001). Abrupt vessel closure during PTCA occurred only in patients with unstable angina (0% versus 17%, p less than 0.05). The major complication rate was 2.5% in the stable angina group, and 20% in unstable angina group (p less than 0.01). This rate was also significantly higher than the complication rate of 8% observed in 442 procedures that were performed during the same period in patients with the unstable angina and nonocclusive stenosis (p less than 0.01). Patients with unstable angina who undergo PTCA of a totally occluded artery represent a subset of high risk for major complications.

Acute Disease↗
PubMed1991

Regional differences in elastic recoil after percutaneous transluminal coronary angioplasty: a quantitative angiographic study.

The immediate result of percutaneous transluminal coronary angioplasty is influenced by both plastic and elastic changes of the vessel wall. To evaluate the amount of elastic recoil after coronary balloon angioplasty, the minimal luminal cross-sectional area of the largest balloon used at highest inflation pressure was compared with the minimal luminal vessel cross-sectional area directly after final balloon deflation in 607 lesions (526 patients). Elastic recoil was defined as the difference between balloon cross-sectional area and minimal luminal cross-sectional area of the dilated coronary segment immediately after balloon withdrawal. A videodensitometric analysis technique was used to avoid geometric assumptions on stenosis morphology directly after angioplasty. Mean balloon cross-sectional area was 5.3 +/- 1.6 mm2 and minimal luminal cross-sectional area after angioplasty was 2.8 +/- 1.4 mm2. Reference areas before and after angioplasty did not differ (6.0 +/- 2.6 and 6.2 +/- 2.6 mm2, respectively). Univariate analysis revealed that asymmetric lesions, lesions located in less angulated parts of the artery and lesions with a low plaque content showed more elastic recoil. Lesions located in distal parts of the coronary tree were also associated with more elastic recoil probably related to relative balloon oversizing in these distal lesions.

Aged↗
PubMed1991

Prevention of restenosis after percutaneous transluminal coronary angioplasty with thromboxane A2-receptor blockade. A randomized, double-blind, placebo-controlled trial. Coronary Artery Restenosis Prevention on Repeated Thromboxane-Antagonism Study (CARPORT).

BACKGROUND: GR32191B is a novel thromboxane A2-receptor antagonist with potent antiagregational and antivasoconstrictive properties. We have conducted a randomized, double-blind placebo-controlled trial to study its usefulness in restenosis prevention. METHODS AND RESULTS: Patients received either GR32191B (80 mg orally before angioplasty and 80 mg/day orally for 6 months) or 250 mg i.v. aspirin before angioplasty and placebo for 6 months. Coronary angiograms before angioplasty, after angioplasty, and at 6-month follow-up were quantitatively analyzed. Angioplasty was attempted in 697 patients. For efficacy analysis, quantitative angiography at follow-up was available in 522 compliant patients (261 in each group). Baseline clinical and angiographic parameters did not differ between the two treatment groups. The mean difference in coronary diameter between postangioplasty and follow-up angiogram (primary end point) was -0.31 +/- 0.54 mm in the control group and -0.31 +/- 0.55 mm in the GR32191B group. Clinical events during 6-month follow-up, analyzed on intention-to-treat basis, were ranked according to the highest category on a scale ranging from death (control, six; GR32191B, four) to nonfatal infarction (control, 22; GR32191B, 18), bypass grafting (control, 19; GR32191B, 22) and repeat angioplasty (control, 52; GR32191B, 48). No significant difference in ranking was detected. Six months after angioplasty, 75% of patients in the GR32191B group and 72% of patients in the control group were symptom free. CONCLUSIONS: Long-term thromboxane A2-receptor blockade with GR32191B does not prevent restenosis and does not favorably influence the clinical course after angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1990

Quantitative angiographic assessment of elastic recoil after percutaneous transluminal coronary angioplasty.

Little is known about the elastic behavior of the coronary vessel wall directly after percutaneous transluminal coronary angioplasty (PTCA). Minimal luminal cross-sectional areas of 151 successfully dilated lesions were studied in 136 patients during balloon inflation and directly after withdrawal of the balloon. The circumvent geometric assumptions about the shape of the stenosis after PTCA, a videodensitometric analysis technique was used for the assessment of vascular cross-sectional areas. Elastic recoil was defined as the difference between balloon cross-sectional area of the largest balloon used at the highest pressure and minimal luminal cross-sectional area after PTCA. Mean balloon cross-sectional area was 5.2 +/- 1.6 mm2 with a mean minimal cross-sectional area of 2.8 +/- 1.4 mm2 immediately after inflation. Oversizing of the balloon (balloon artery ratio greater than 1) led to more recoil (0.8 +/- 0.3 vs 0.6 +/- 0.3 mm, p less than 0.001), suggestive of an elastic phenomenon. A difference in recoil of the 3 main coronary branches was observed: left anterior descending artery 2.7 +/- 1.3 mm2, circumflex artery 2.3 +/- 1.2 mm2 and right coronary artery 1.9 +/- 1.5 mm2 (p less than 0.025). The difference was still statistically significant if adjusted for reference area. Thus, nearly 50% of the theoretically achievable cross-sectional area (i.e., balloon cross-sectional area) is lost shortly after balloon deflation.

Absorptiometry, Photon↗
PubMed1990

[Directional coronary atherectomy; initial Dutch experiences with a new percutaneous revascularization procedure].

Acute complications and restenosis in the first few months after a successful procedure remain the two major limitations of coronary balloon angioplasty. New devices have been developed in order to avoid these limitations. We tested the directional atherectomy catheter clinically and compared the immediate quantitatively analysed results with two other recently developed devices and conventional balloon angioplasty. A gain in luminal diameter of 1.7 mm after atherectomy was observed in 7 patients. This is far more than could be accomplished by balloon angioplasty, stenting and rotablation. Furthermore, the size of the device in relation to the size of the obstructed vessel suggests that a Dotter effect is partly responsible for the gain in luminal diameter. Whether this large gain can prevent restenosis remains to be confirmed. Preliminary literature data suggest that this is not the case.

Adult↗
PubMed1989

Diagnostic merits of exercise testing in females.

The diagnostic accuracy of conventional exercise electrocardiography was compared with exercise algorithms specifically aimed at application in females, with R wave and heart rate adjusted ST-segment changes, and with discriminant analysis. A symptom-limited bicycle exercise test was performed by 189 females without previous infarction with a normal electrocardiogram (ECG) at rest. Frank lead ECG was computer processed. ST-segment amplitudes in lead X were superior to measurements in lead Y, but their sensitivity amounted only to 50% at a specificity of 90%. Correction for R wave amplitude marginally increased sensitivity. It was confirmed that leads with inferiorly directed vectors such as standard leads II, III, aVF or Frank lead Y should not be used for diagnostic purposes in females. Exercise-induced increases in R-wave amplitude of at least 0.1 mV occurred in only 8% of females with coronary disease. Previously described discriminant function using attained heart rate, ST-segment depression and a sex-dependent ST segment correction factor yielded a sensitivity of 60% at a specificity of 90%. Sensitivities of heart rate adjusted ST-segment changes and of a previously proposed discriminant function were greater than 70% at a specificity of 90%. It is concluded that the diagnostic yield of exercise testing in females can be improved by use of more sophisticated electrocardiographic and exercise variables.

Coronary Disease↗
PubMed1989

A comparison of methods of analysing exercise tests for diagnosis of coronary artery disease.

The diagnostic accuracy of the following methods of analysing exercise tests were evaluated: (a) the cumulative area of ST segment depression during exercise normalised for workload and heart rate (exercise score); (b) discriminant analysis of electrocardiographic exercise variables, workload, and symptoms; and (c) ST segment amplitude changes during exercise adjusted for heart rate. Three hundred and forty five men without a history of myocardial infarction were studied. One hundred and twenty three were apparently healthy. Less than half (170) had coronary artery disease. All had a normal electrocardiogram at rest. A Frank lead electrocardiogram was computer processed during symptom limited bicycle ergometry. The accuracy of the exercise score (a) was low (sensitivity 67%, specificity 90%). Discriminant analysis (b) and ST segment amplitude changes adjusted for heart rate (c) had excellent diagnostic characteristics (sensitivity 80%, specificity 90%), which were little affected by concomitant use of beta blockers. Both methods seem well suited for diagnostic application in clinical practice.

Adult↗
PubMedDate not supplied

Intravenous coronary angiography using electron beam computed tomography.

Intravenous coronary angiography with electron beam computed tomography (EBCT) allows for the noninvasive visualisation of coronary arteries. With dedicated computer hardware and software, three-dimensional renderings of the coronary arteries, veins, and other cardiac structures can be constructed from the individual transaxial tomograms. Interest in this technique is growing, and recently a number of clinical studies have been published comparing EBCT coronary angiography with conventional cine-coronary angiography. In this article, image acquisition, postprocessing techniques, and the results of recently published clinical studies are discussed. EBCT coronary angiography is a promising imaging technique of coronary arteries. Currently, it is a reasonably robust technique for the visualization and assessment of the left main and left anterior descending coronary artery. However, at the moment a relatively high proportion of the right and circumflex coronary angiograms are noninterpretable. Improvements in image acquisition and postprocessing techniques are expected to improve visualization and diagnostic accuracy of the technique.

Beta Particles↗
PubMedDate not supplied

Basic principles of magnetic resonance imaging.

Magnetic resonance imaging (MRI) is a noninvasive imaging technique that is becoming more and more important in clinical cardiology. Physicians must understand the basic principles of MRI before reliable use in practice is possible. Therefore, we will give an introduction to basic MRI principles necessary to understand the difficulties of cardiac MRI. First the generation of a signal by the combination of a strong magnetic field, radiofrequency pulses, and temporary changes in the magnetic field is explained. Then, the processes of localization of different points in an image, resolution, and signal-to-noise ratio are highlighted. Finally, the influence of tissue characteristics such as T1 and T2 on the contrast of an image are discussed.

Cardiovascular Diseases↗
PubMedDate not supplied

Magnetic resonance imaging of the coronary arteries: techniques and results.

Recently a new noninvasive imaging technique, magnetic resonance imaging (MRI) has been developed that has the potential to assess the coronary arteries. MRI of the coronary arteries is a challenging task because of the motion of the vessels during cardiac contraction and the motion of the heart with respiration. Several two-dimensional and three-dimensional acquisition techniques have been developed to overcome these problems. In this article we will describe different conventional MR techniques such as spin-echo and gradient-echo imaging. Also, we will describe new developments in MRI as ultrafast breathhold techniques using echo planar imaging or targeted volume scanning. Other new developments are respiratory gating techniques with or without respiratory motion correction. Finally, we will review the results of these techniques in the detection of coronary artery bypass graft patency, coronary artery stenosis, and the evaluation of coronary artery anomalies.

Coronary Artery Disease↗