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Biomedical subjects

I De Scheerder

Publications and source records attributed to I De Scheerder.

At least 19 recordsLinked to original sources
PubMed2000

Long-term follow-up after coronary stenting and intravascular red laser therapy.

A high restenosis rate remains a limiting factor for coronary angioplasty and stenting. Recently, use of intravascular red light therapy (IRLT) has been shown to be effective in different animal models and in humans in reducing the restenosis rate. Sixty-eight patients were treated with IRLT in conjunction with coronary stenting procedures. Mean age was 64 +/- 9 years. Treated lesions were type A (11), type B (42), and type C (18) with a mean lesion length of 16.5 +/- 2.4 mm. Reference vessel diameter and minimal lumen diameter (MLD) before therapy were 2.90 +/- 0.15 and 1.12 +/- 0.36 mm, respectively. After stenting and laser irradiation, MLD was 2.76 +/- 0.39 mm. No procedural complications or in-hospital adverse events occurred. All patients were followed up as depicted in the protocol. Sixty-one patients underwent angiographic restudy, which revealed restenosis in 9 patients (14.7%). Observed restenosis rate by artery size was > 3 mm (n = 21, 0%), 2.5 to 3.0 mm (n = 28, 14.2%), and <2.5 mm (n = 12, 41.6%). We conclude that IRLT is safe and feasible and reduces the expected restenosis rate in patients after coronary stenting in arteries of >2.5 mm.

Aged↗
PubMed2000

A novel platinum-iridium, potentially gamma radioactive stent: evaluation in a porcine model.

In-stent restenosis (ISR) is a major problem within stented arteries. Surface treatment of stents with platinum and gold were found to have the maximum charge with least neointima formation (NF). This study was designed to evaluate platinum (maximum electrical charge) as a material to make stents to reduce NF. Iridium was added to make an alloy suitable for stent manufacture, with the potential to make the stent radioactive. We implanted the novel platinum-iridium (PI) stent in 10 porcine coronaries and compared to the Palmaz-Schatz (PS) stent implanted in 8 coronary arteries. Six weeks after implantation, angiography of the stented vessel was performed before sacrifice. The coronaries were perfusion-fixed and stained, and vessel parameters were analyzed by computer-aided histomorphometry. The thrombus formation and the inflammatory response was less in the PI stent (0.04 +/- 0.1 vs. 0.24 +/- 0.2, P = 0.005; and 1.1 +/- 0.5 vs. 2.4 +/- 0.3, P < 0.001). The NF from PI-stented arteries was smaller in size than the PS controls (1.9 +/- 0.6 mm(2) vs. 2.4 +/- 0.4 mm(2), P = 0.06). However, PI stents presented with higher recoil than the PS stent (16% vs. 5%, P < 0.001). Platinum-iridium is a highly biocompatible material with high performance, low inflammatory response with small NF. This stent does not lead to thrombus formation and has the potential (due to the presence of iridium) to be irradiated to form a gamma radioactive stent. Cathet. Cardiovasc. Intervent. 51:364-368, 2000.

Animals↗
PubMed2000

M cells and transmural heterogeneity of action potential configuration in myocytes from the left ventricular wall of the pig heart.

OBJECTIVE: Heterogeneity of action potential configuration in the left ventricle (LV), and the contribution of M cells to it, has been observed in the human heart and is important for arrhythmogenesis. Whether the pig heart has similar properties remains a controversial but important issue as the pig heart is currently under study for use in xenotransplantation. METHODS: Single myocytes were enzymatically isolated from the epicardium (EPI, ncells = 29), midmyocardium (MID, ncells = 38), and endocardium (ENDO, ncells = 13) of the free LV wall (npigs = 26, 14-22 weeks old, 55-80 kg), and studied at different stimulation rates during whole-cell recording (normal Tyrode's solution, K(+)-aspartate-based pipette solution, 50 microM K5fluo-3 as [Ca2+]i indicator, 37 degrees C). Standard six-lead ECGs were recorded from anesthetized pigs. RESULTS: The action potential duration (APD) was not significantly different at 0.25 Hz vs. 2 Hz for the majority of cells in all three layers. However, a subpopulation of cells behaved like M cells and had a very steep frequency response (APD90 at 0.25 Hz 538 +/- 30 ms, vs. 337 +/- 9 ms at 2 Hz, P < 0.05, n = 22). These cells were found predominantly in the MID layer (34% of cells), but also (24%) in EPI. M cells had a more pronounced spike-and-dome configuration, with a significantly larger phase 1 magnitude and plateau voltage. The frequency response of these parameters was different from the other cell types. [Ca2+]i transients tended to be larger in M cells. For the in vivo ECG of anesthetized pigs, the QT time was close to the APD90 of M cells, and J waves were seen in 7/12 recordings. CONCLUSIONS: In young adult pigs, M cells can be identified by a steep frequency response of the APD and by a spike-and-dome configuration. These cells are mostly, but not exclusively, found in the midmyocardium, and could contribute to the ECG characteristics. Their properties may however be different from those of other species, including humans.

Action Potentials↗
PubMed2000

Coronary radiation therapy with liquid rhenium-186: a first clinical experience.

BACKGROUND: Coronary radiation therapy (CRT) is a new, attractive approach for the treatment and prevention of restenosis after percutaneous coronary interventions (PCI). The RadioCath device consists of a standard balloon dilatation catheter that can be charged with a solution of sodium 186Re perrhenate, a predominant beta emitter. The safety and performance of this new device was evaluated in a pilot trial. METHODS AND RESULTS: Thirty-three patients with a de novo lesion in a native coronary artery were treated with the RadioCath device after successful angioplasty. The average dwell time to deliver a dose of 20 Gy at 0.5 mm into the vessel wall was 418+/-64 seconds. The treatment was well tolerated by most of the patients. In 79%, only one inflation cycle was required to deliver the prescribed dose. There were two procedural device-related complications (5.9%) and three minor procedural related in-hospital complications (9%). CONCLUSIONS: CRT using a balloon catheter device, charged with a sodium 186Re perrhenate solution, seems feasible and safe. Clinical and angiographic 6-month follow-up data are pending.

Angioplasty, Balloon, Coronary↗
PubMed2000

Evaluation of the biocompatibility of two new diamond-like stent coatings (Dylyn) in a porcine coronary stent model.

UNLABELLED: Hydrogenated diamond-like carbon films (DLC, a-C:H), deposited using plasma-assisted or ion beam-assisted techniques, offer great potential as self-lubricating coatings in many tribological applications. Additionally, studies on biocompatibility have shown that DLC is an inert, impervious hydrocarbon with properties suitable for use in the biomedical field. One particular class of modified DLC coatings are diamond-like nanocomposite coatings (DLN or Dylyn , Bekaert, Kortrijk, Belgium), which offer promising solutions for many industrial applications. In this study, the biocompatibility of two diamond-like stent coatings are evaluated in a porcine coronary stent model. METHODS: Either coated or non-coated stents were randomly implanted in two coronary arteries of 20 pigs so that each group contained 13 stented arteries. Pigs underwent a control angiogram at 6 weeks and were then sacrificed. Quantitative coronary analysis before, immediately after stent implantation, and at 6 weeks was performed using the semi-automated Polytron 1000 system (Siemens, Erlangen, Germany). Morphometry was performed using a computerized morphometric program. Angiographic analysis showed similar baseline selected arteries and post-stenting diameters. At 6-week follow-up, there was no significant difference in minimal stent diameter. Histopathology revealed a similar injury score in the 3 groups. Inflammation was significantly increased in the DLN-DLC coating group. Thrombus formation was significantly decreased in both coated stent groups. Neointimal hyperplasia was decreased in both coated stent groups; however, the difference with the non-coated stents was not statistically significant. Area stenosis was lower in the DLN-coated stent group than in the control group (41 +/- 17% vs. 54 +/- 15%; p = 0.06). CONCLUSION: The results indicate that the diamond-like nanocomposite stent coatings are compatible, resulting in decreased thrombogenicity and decreased neointimal hyperplasia. Covering this coating with another diamond-like carbon film (DLC) resulted in an increased inflammatory reaction and no additional advantage compared to the single-layer diamond-like nanocomposite coating.

Animals↗
PubMed1999

Abnormal postsystolic thickening in acutely ischemic myocardium during coronary angioplasty: a velocity, strain, and strain rate doppler myocardial imaging study.

We report a case in which the combination of gray scale imaging of wall thickness changes allied to color DMI regional velocity, strain, and strain rate data identified the development and regression of diastolic thickening in the acute ischemic segment during a right coronary artery percutaneous transluminal coronary angioplasty (PTCA). We also discuss the possible mechanisms and potential clinical implications of this finding.

Aged↗
PubMed1999

Assessment of coronary angiograms prior to and after treatment with abciximab, and the outcome of angioplasty in refractory unstable angina patients. Angiographic results from the CAPTURE trial.

BACKGROUND: The CAPTURE study (c 7E3 A nti P latelet T herapy in U nstable Re fractory angina) was designed to assess outcome in patients with refractory angina undergoing angioplasty, receiving either abciximab or placebo. METHODS: One thousand two hundred and sixty-five patients with refractory unstable angina, defined as recurrent myocardial ischaemia despite medical treatment including heparin and nitrates were enrolled. After angiography, patients received an infusion of abciximab or placebo over 18-24 h preceding angioplasty, continuing until 1 h after the procedure. In 1197 patients undergoing angioplasty the angiographic committee centrally reviewed the baseline as well as the procedural angiograms. Coronary flow and lesion characteristics were assessed in the baseline angiogram as well as before intervention. Angiographic outcome, reason for failure as well as complications were assessed after angioplasty. RESULTS: At 30 days follow-up, patients receiving abciximab (n=595) compared with placebo (n=602) had a 30% reduction in the composite primary end-point death, myocardial infarction or urgent (re)intervention: 10.8% vs 15.4% (P=0.017). Baseline demographics were identical in the angiogram available group compared with the total study group. At 30 days, the non-angiogram available patients showed a higher incidence of events compared to those in whom the angiogram was reviewed: 19.4 vs 13.1% (P=ns). Lesion characteristics and coronary flow were not different at baseline between the placebo and abciximab groups. A primary end-point was reached in 9.6% of both placebo and abciximab patients with type A or B(1)lesions, in 17.0% vs 12.0% with type B(2)lesions, and in 19.1% vs 11.5% with type >B(2)or C lesions. Sixty-one percent of placebo and abciximab patients had TIMI 3 flow at baseline angiography. Pre-angioplasty TIMI 3 flow was observed in 69% and 72% respectively. The thrombus was resolved between the angiograms in 22% and 43% respectively, in the placebo and abciximab groups (P=0. 033). Angiographic success of the procedure was achieved in 88% and 94% in the placebo and abciximab patients, respectively (P<0.001). Stents were implanted in the ischaemia-related artery in 56 and 60 patients, respectively. However, failure of the stent procedure was more frequent in the placebo group than in the abciximab group, nine vs no patients (P=0.003). CONCLUSION: More frequent thrombus resolution was observed and a higher angiographic success rate was achieved in patients treated with abciximab before and during angioplasty compared with placebo. Patients with complex lesions as the underlying pathology reached fewer end-points if treated with abciximab before and during angioplasty.

Abciximab↗
PubMed1997

Ex vivo experiment on radiofrequency liver ablation with saline infusion through a screw-tip cannulated electrode.

PURPOSE: To investigate whether radiofrequency (RF) therapy with hypertonic saline infusion through a hollow screw-tip electrode can cause a lesion size suitable for liver tumor ablation. MATERIALS AND METHODS: RF tissue ablation of 180 sites was performed by using a hollow screw-tip electrode in 40 freshly excised swine livers. Under both power and temperature control modes, the ablation effects with and without various regimes of 5% hypertonic saline (1 ml/min) prior to and/or during the procedure were compared by measuring the size of lesions at dissection and confirmed by T1 and T2 weighted magnetic resonance (MR) imaging. RESULTS: The maximal lesion diameter of 5.5 cm was reached at 30 W with saline infusion 1 min prior to and during 12 min of ablation. The smaller sizes (P < 0.01) between 0.3 and 2.5 cm in diameter were met with noninfusion or preinfusion-only groups. The RF ablation lesions appeared as hyper- and hypointense areas on T1 and T2 MR images, respectively. CONCLUSIONS: RF ablation in combination with present hollow screw-tip electrode and saline infusion allows for necrotic development of suitable size for liver tumor ablation. Such ablated lesions can be visualized with MR imaging.

Animals↗
PubMed1997

Experimental study of thrombogenicity and foreign body reaction induced by heparin-coated coronary stents.

BACKGROUND: Results of recent randomized clinical trials have revealed a significant reduction in angiographic restenosis rate when adjunctive stenting was performed after conventional coronary balloon angioplasty. The thrombogenicity of metal stents, however, remains a concern. In the present study, we compare the thrombogenicity of heparin-coated coronary stents with that of bare metallic coronary stents. METHODS AND RESULTS: Thrombogenicity of metallic coronary stents (four heparin-coated and eight bare stents) was studied in a rat arteriovenous shunt model with the use of 125I-labeled fibrinogen and 51Cr-labeled platelets. Total clot weight after 30-minute follow-up was significantly lower in the heparin-coated stents compared with the bare stents (8.1 +/- 3.7 versus 25.8 +/- 4.6 mg; P < .001). Relative 125I and 51Cr activities in the stents were significantly higher in the bare stents than in the heparin-coated stents (125I, 1.03 +/- 0.43 versus 0.18 +/- 0.04, P = .003; 51Cr, 17.5 +/- 6.8 versus 4.4 +/- 1.0, P = .004). Subsequently, heparin-coated and bare stents were randomly implanted in the right coronary artery of 20 domestic pigs. Angiographic parameters were similar between both groups at baseline and after 6-week follow-up. Morphometry also did not show a significant difference in lumen area (bare, 1.03 +/- 0.83 mm2; heparin-coated, 1.12 +/- 0.73 mm2; P = NS) or neointimal hyperplasia (bare, 1.01 +/- 0.81 mm2; heparin-coated, 1.21 +/- 0.57 mm2; P = NS). CONCLUSIONS: Heparin coating of metallic coronary stents decreases their thrombogenicity but does not improve late vessel patency and neointimal hyperplasia at follow-up in a porcine coronary model.

Animals↗
PubMed1995

The safety of intracoronary ultrasound. A multicenter survey of 2207 examinations.

BACKGROUND: Intracoronary ultrasound (ICUS) is increasingly used in clinical practice to study the natural history of coronary artery disease and to assess the effects of intracoronary, catheter-based interventions. However, the risk associated with the procedure is not well documented. METHODS AND RESULTS: ICUS studies performed in 28 centers were retrospectively included; these centers agreed to contribute to the study among a total of 60 centers initially invited. Among the 2207 ICUS studies, 505 (23%) were performed in heart transplant recipients and 1702 (77%) in nontransplant patients. Indication for ICUS was diagnostic imaging in 915 (41%), drug testing in 244 (11%), and guidance for intracoronary interventions in 1048 patients (47%). There were no complications in 2034 patients (92.2%). In 87 patients (3.9%), complications occurred but were judged to be "not related" to ICUS by the operator. In 63 patients (2.9%), spasm occurred during ICUS imaging. In 9 patients (0.4%), complications other than spasm were judged to have a "certain relation" to ICUS, including acute procedural events in 6 (3 acute occlusion, 1 embolism, 1 dissection, and 1 thrombus) and major events in 3 patients (2 occlusion and 1 dissection; all resulting in myocardial infarction). In 14 patients (0.6%), complications with "uncertain relation" to ICUS were recorded, including acute procedural events in 9 (5 acute occlusion, 3 dissection, and 1 arrhythmia) and major events in 5 patients (2 myocardial infarction and 3 emergency coronary artery bypass surgery). The incidence of acute procedural or major complications judged to be associated with ICUS (uncertain relation or certain relation to ICUS) was compared in different patient groups. The complication rate was higher in patients with unstable angina or acute myocardial infarction (2.1% events) as compared with patients with stable angina pectoris and asymptomatic patients (0.8% and 0.4%, respectively; chi 2 = 10.9, P < .01). These complications were also more frequent in patients undergoing interventions (1.9%) as compared with transplant and nontransplant patients undergoing diagnostic ICUS imaging (0% and 0.6%, respectively; chi 2 = 13.5, P < .001). Adverse events were few, and no association was detected between these events and the size or type of ICUS catheter used. CONCLUSIONS: ICUS is associated with (but not necessarily the direct cause of) a minor acute clinical risk. Vessel spasm is the most frequent event occurring during ICUS. Other complications predominantly occur in patients with acute coronary syndromes and during guidance for intervention.

Adult↗
PubMed1995

In vivo comparison of different quantitative edge detection systems used for measuring coronary arterial diameters.

Three different systems for quantitative coronary analysis [Cardiovascular Measurement System (CMS); Polytron 1000; Angiographic Workstation (AWOS)] were compared in 109 patients before and after coronary angioplasty and at follow-up coronary angiography. Correlation coefficients were low and 95% limits of agreement were wide. In general, CMS exhibited a tendency to yield lower values for very small diameters and higher values for larger vessels. The acute gain in minimal luminal diameter was considerably smaller when assessed by AWOS as compared to Polytron (0.52 vs. 0.71 mm, P < .0001) and to CMS (0.52 vs. 0.75 mm, P < .0001). Long-term gain was much larger when assessed by Polytron as compared to AWOS (18.8 vs. 11.5%, P < .001) and it was almost double for CMS as compared to AWOS (20.7 vs. 11.5%, P < .0001). In conclusion, in the individual patient very different results can be obtained when different QCA systems are used, and systematic differences between the systems are encountered.

Algorithms↗
PubMed1995

Limited value of exercise testing in the detection of silent restenosis after successful coronary angioplasty.

We studied the diagnostic value of exercise electrocardiographic (ECG) testing in 191 patients who were completely asymptomatic 6 months after a successful percutaneous transluminal coronary angioplasty procedure. With > 70%- and > 50%-diameter stenosis at follow-up as restenosis criteria, the sensitivities of exercise ECG testing were 29% and 21%; the specificities 89% and 91%; the positive predictive values 20% and 52%; the negative predictive values 93% and 70%; the accuracies 83% and 68%; and the risk ratios 2.8 and 1.7, for prevalences of 9% and 33%, respectively. There were no significant differences in the diagnostic value of exercise ECG testing between men and women, patients receiving or not receiving beta-blocking agents, and the presence or absence of pathologic Q waves. Significant differences in systolic blood pressure and the rate-pressure product at peak exercise were found between patients with and without restenosis. For individual patients, however, no practical conclusions can be drawn from these values. In conclusion, the diagnostic value of exercise ECG testing for silent restenosis is low, and supplementation with other techniques seems to be warranted.

Adult↗
PubMed1994

The impact of balloon material and lesion characteristics on the incidence of angiographic and clinical complications of coronary angioplasty.

To assess the importance of balloon material used for percutaneous transluminal coronary angioplasty (PTCA), we compared the complication rates observed with low complaint plastomer (PM 300), intermediately compliant polyethylene (PE 600), and highly compliant polyolefin copolymer (POC) balloons. In a total of 1,650 procedures, one of these balloon materials was used to dilate 2,040 lesions. The dissection rate tended to be slightly lower with the use of more compliant balloon material. The total clinical complication rate (death, emergency coronary surgery, myocardial infarction, need for bail-out stenting or for prolonged heparin treatment, abrupt out-of-laboratory vessel closure) was 8.1%, 7.4%, and 4.2% in the procedures exclusively performed with PM 300 (N = 653), PE 600 (N = 543) and POC (N = 454) balloons, respectively (P = 0.03). In multivariate analysis, the use of less compliant balloon material emerged as an independent correlate of clinical complications (P = 0.007). However, the predictive power of the lesion complexity (B2, C versus A, B1) was four times stronger. In contrast to current concerns, the use of compliant balloon material seems at least as safe as the use of less compliant material.

Aged↗
PubMed1994

Intravascular ultrasound versus angiography for measurement of luminal diameters in normal and diseased coronary arteries.

Quantitation of coronary luminal diameter with a 20 MHz mechanically rotating intravascular ultrasound (IVUS) catheter was compared with orthogonal-view cineangiography by use of a semiautomated edge-detection algorithm in 48 patients undergoing coronary angioplasty. Quantitative comparison of 196 matched segments was attempted, but in only 174 (88.8%) was a direct comparison of the two techniques possible. In angiographically normal coronary arteries (46 segments) the correlation between the values obtained by quantitative coronary angiography (QCA) and those achieved by IVUS was excellent (r = 0.92, p < 0.0001). For mild stenoses (80 segments) the correlation coefficient was only fair (r = 0.467, p < 0.001). After percutaneous transluminal coronary angioplasty the correlation coefficient between IVUS and QCA data (48 segments) was very weak (r = 0.282, p < 0.05). In conclusion, coronary IVUS is feasible and safe and even for a limited range of coronary arterial narrowing, significant correlations between IVUS and QCA measurements of minimal lumen diameter were found. They were excellent in normal coronary arteries, moderate in mildly diseased arteries, and weak after balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1994

Angiotensin-converting enzyme inhibition with fosinopril sodium in the prevention of restenosis after coronary angioplasty.

BACKGROUND: Several angiotensin-converting enzyme inhibitors have antiproliferative effects in a rat model after carotid artery balloon injury. METHODS AND RESULTS: We conducted a randomized, double-blind, placebo-controlled trial to assess the effect of fosinopril, a novel angiotensin-converting enzyme inhibitor, in restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA). Patients received fosinopril or matched placebo 10 mg at least 18 hours before PTCA, 20 mg at least 4 hours before PTCA, and 40 mg daily for 6 months. In addition, all patients received aspirin. Coronary angiograms before PTCA and immediately after PTCA as well as at 6-month follow-up were quantitatively analyzed. A total of 509 patients were recruited. The final per-protocol population consisted of 153 fosinopril-treated and 151 placebo-treated patients. Restenosis rates according to the National Heart, Lung, and Blood Institute criterion 4 (loss of > or = 50% of the initial gain [primary end point]) were 45.7% and 40.7% in the fosinopril and control groups, respectively (not significant). The respective mean differences in minimal coronary luminal diameter between post-PTCA and follow-up angiograms were -0.59 +/- 0.71 mm and -0.51 +/- 0.67 mm (not significant). Clinical events during the 6-month follow-up period, analyzed on an on-treatment basis, were ranked according to the most serious event. The respective numbers in the fosinopril and the control groups were for death, 0 and 0; myocardial infarction, 0 and 0; coronary artery bypass graft surgery, 1 and 3; repeat PTCA, 35 and 35; recurrent signs of ischemia necessitating early repeat coronary angiography and managed medically, 6 and 7; and none of the above, 111 and 106. All these differences were significant. CONCLUSIONS: Administration of fosinopril in a dose of 40 mg daily during 6 months after PTCA does not prevent restenosis and has no effect on overall clinical outcome.

Angioplasty, Balloon, Coronary↗
PubMed1994

Role of intravascular ultrasound in coronary artery disease: a new gold standard? An overview.

Although selective contrast coronary arteriography has been the gold standard approach for coronary imaging since more than 30 years, new coronary imaging techniques are currently under development. Intravascular ultrasound (IVUS) is perhaps the most promising of these additional techniques. IVUS makes use of miniaturised crystals incorporated at catheter tips and provides real time, cross-sectional and longitudinal, high resolution images of the arterial wall with three-dimensional reconstruction capabilities (Pandian, 1989; Coy et al., 1991; Liebsen & Klein, 1992). Different devices have been constructed. Actually two types are being used: mechanical (hand-rotated or motor-driven) systems and phased array systems using high-frequency (20-30 MHz) transducers (Bom et al., 1989). Coronary ultrasound imaging performed during catheterization is feasible and safe as demonstrated in several studies examining normal and pathologic coronary arteries (De Scheerder et al., in press).

Coronary Disease↗