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Biomedical subjects

B Reimers

Publications and source records attributed to B Reimers.

45 records · Page 3Linked to original sources
PubMed1997

First experience with imaging core wires.

This study is the first assessment of feasibility and clinical usefulness of an imaging wire. The device used is a 0.018" flexible cable mounting a 30 MHz piezoelectric crystal at the end. The only possible application of the wire in its current configuration is the assessment of balloon expansion with over-the-wire balloon catheters. In this study, 17 lesions were examined in 14 patients. Despite careful removal of the air, no image could be obtained with the balloon deflated or through the shaft of conventional balloon catheters. When the balloon was inflated to 1-4 atm the circular echo-free cross-section of the balloon became visible, surrounded by the dense line of the balloon membrane and by the vessel wall. By examining the stent area at different balloon pressures, it was possible to determine the stent recoil between maximal balloon expansion and lowest balloon pressure allowing a readable ultrasound image. These encouraging preliminary observations confirm the feasibility of the use of an ultrasound guidewire for monitoring balloon expansion during stent implantation. After high pressure inflation, a moderate reduction of the stent lumen was observed during deflation, compatible with the small recoil predicted for the stainless-steel mesh stent used.

Angioplasty, Balloon, Coronary↗
PubMed1996

Percutaneous transluminal coronary angioplasty in refractory unstable angina pectoris: are new devices useful?

This study was undertaken to assess if the introduction of new angioplasty devices (autoperfusion balloon catheters, stent and atherectomy) could ameliorate early and late results of prompt percutaneous transluminal coronary angioplasty (PTCA) in patients with refractory unstable angina. From January 1993 to June 1995, 59 of 278 patients (14 female, 45 male; mean age: 61 +/- 10 years; range: 38-78) admitted to our Coronary Care Unit with the diagnosis of unstable angina had more than one episode of chest pain at rest with dynamic electrocardiographic ST-T changes and without signs of cardiac necrosis while on medical therapy including oxygen, aspirin, heparin, nitroglycerin and either a beta-blocker or a calcium-antagonist. Coronary angiography was performed within 48 h from the last ischemic attack and a culprilesion technically suitable for PTCA was identified. PTCA was performed in 73 lesions. Elective stent implantation was considered for 16 type B or C lesions in 14 patients. The procedure was initially successful in 52/59 patients (88%), uncomplicated unsuccessful in 4/59 (7%) and complicated in 3/59 (5%). Elective stent insertions were all successful (16/16, 100%). All successfully treated patients were followed up for a mean of 12 +/- 7 months (range: 6-27): 2/52 patients (3.8%) suffered from non-transmural myocardial infarction, 14/52 (26.9%) had a recurrence of angina and 2/52 (3.8%), asymptomatic, had a positive stress test. We conclude that prompt PTCA in refractory unstable angina using 1990s 'state of the art' equipment compares favorably to previous study and that stent delivery might become the elective treatment of complex lesions in this subset of patients.

Aged↗
PubMed1996

Subacute stent thrombosis and the anticoagulation controversy: changes in drug therapy, operator technique, and the impact of intravascular ultrasound.

Clinical trials have shown that stents are superior to other catheter-based coronary interventions in terms of reduced complications and improved long-term efficacy. With utilization of high-pressure balloon inflation and intravascular ultrasound (IVUS) guidance, stent implantation can now be performed safely without anticoagulation (i.e., with lower rates of stent thrombosis and vascular complications). In 2 recent prospective clinical trials, stent thrombosis occurred in 3.5% of cases despite anticoagulant therapy, which resulted in an average of 7% vascular and bleeding complications. Initial use of IVUS during traditional stent deployment showed that 80% of stents were underexpanded and led to the hypothesis that stent thrombosis might be decreased as a result of optimal stent placement under IVUS guidance without the need for anticoagulation. In a prospective clinical trial to test this hypothesis, three factors were found to reduce stent thrombosis: full stent expansion, complete apposition to the vessel wall, and full lesion coverage. Predictors of thrombotic risk in this era of high-pressure stent deployment without anticoagulation include low ejection fraction, residual dissections, slow flow, multiple stents per lesion, and smaller postprocedure stent luminal diameter. To optimize stent expansion, stent dilation should be performed using a mean inflation pressure of 18 atm with a noncompliant or minimally compliant balloon sized to the vessel being treated (B/V ratio = 1.1). Controversy still remains about the best poststent antiplatelet regimen, and results of a recent trial should indicate whether heparin coating provides additional protection from stent thrombosis.

Anticoagulants↗
PubMed1996

Three-dimensional intracoronary ultrasound imaging. Methodology and clinical relevance for the assessment of coronary arteries and bypass grafts.

Three-dimensional (3-D) reconstruction of intracoronary ultrasound (ICUS) images has an increasing application as the applicability of systems of on-line analysis provides a superior guidance by coupling the advantages of a high-resolution cross-sectional imaging with an overview of stenosis and reference segments. Detection of the external contour of the vessel which is a prerequisite for measurements of coronary plaques is currently not provided by the algorithms for automated on-line analysis. Thus, off-line reconstruction is required for studies aiming at the assessment of progression/regression of atherosclerosis and of mechanisms of interventions or restenosis. Various 3-D reconstruction methods with specific advantages and limitations are able to meet the different requirements concerning applicability, quality of visualization, and accuracy of quantification. The use of 3-D ICUS in the assessment of cardiac transplant recipients permits a more reliable and accurate quantification of intimal hyperplasia as seen in cardiac allograft arteriopathy. In patients undergoing bypass surgery it may influence the therapeutic decision, since it allows to determine the longitudinal extent of calcification and frequently discovers atherosclerosis in angiographically normal segments. Vessel stenoses both of native coronary arteries and bypass grafts can be studied by 3-D ICUS and additional information can be obtained during catheter based interventions. Despite some remaining technical limitation 3-D reconstruction of ICUS images has the potential of becoming a practical tool to simplify the interpretation and quantification of ICUS images.

Algorithms↗
PubMed1995

[Rotational atherectomy and PTCA in complex coronary lesions (B2 and C): the immediate and long-term results].

BACKGROUND: Percutaneous transluminal coronary angioplasty (PTCA) in complex coronary lesions (type B2 and C of the modified AHA/ACC classification) presents a lower primary success rate and higher risk of dissection than type A and B1 lesions. An alternative approach to this lesions is coronary rotational ablation (Rotablator, Heart Technology) with complementary PTCA using low inflation pressures ("facilitated angioplasty"). MATERIALS AND METHODS: Twenty-six type B2 and C lesions in 24 patients (pts) (8 female, 16 male, age 37-80 years) were treated with coronary rotational ablation and complementary PTCA between January 1993 and December 1994 (4.7% of all interventional coronary procedures performed in this period in our laboratory). Eleven pts had stable effort angina and 13 pts had unstable, class IB, IIB, and IIC, angina. The treated vessel was the LAD in 15 cases, CX in 5, RCA in 5, and an intermediate branch in one case. Coronary rotational ablation was proposed because of the presence of two or more risk factors for uneffective or complicated PTCA: eccentricity, calcified lesions, bifurcation stenosis, lesion length > 10 mm, severe stenosis (90-99%), ostial location and bend location (45-60 degrees). No lesion showed coronary thrombus, considered as absolute contraindication to coronary rotational ablation. We used small burrs (burr/artery ratio < 0.75), and complementary PTCA was performed using low inflation pressure (< 8 atm) and long balloons for long lesions (> 10 mm) in order to minimize the risk of dissection. RESULTS: Coronary rotational ablation was successfully performed in all but two cases (24/26; 92.3%), with a reduction of the stenosis from 88 +/- 9% to 45 +/- 10% (range 30-60%). In two pts (7.7%) the procedure was complicated by acute occlusion: both pts underwent effective salvage PTCA with 30% residual stenosis. Small type A and B dissections occurred in 4/26 cases (15.4%). All but one lesions complicated by acute occlusion or dissection following coronary rotational ablation were not or only slightly calcified. Complementary PTCA was performed in all but two pts who already presented 30% residual stenosis after rotational ablation. A further reduction of stenosis to 20 +/- 9% (range 5-30%) was achieved. After complementary PTCA four pts (15.4%) developed type A and B dissections; in one of these a Palmaz-Schatz stent was implanted, whereas the remaining three pts presented a residual stenosis below 30% and no further procedures were undertaken. Overall success rate of rotational atherectomy plus salvage or complementary PTCA or stenting was 100%, and no major complications (Q-wave myocardial infarction, emergency bypass surgery or death) occurred. Three pts showed delayed coronary run-off (slow reflow) after rotational ablation, and two of these released a small amount of cardiac specific enzymes (CK MB) without ECG changes and wall motion alteration on echocardiographic examination. Clinical restenosis, defined as recurrent angina and/or positive exercise stress test, developed in 45.8% (11 pts); in all these pts restenosis was angiographically evidenced (75-99%). CONCLUSIONS: Our experience suggests that coronary rotational ablation along with complementary PTCA using low inflation pressure and long balloons is safe and effective in type B2 and C lesions if calcifications are present; however, restenosis rate remains high.

Adult↗
PubMed1995

[Analysis of risk factors in a group of patients referred for heart transplantation for refractory heart failure: multivariate analysis].

BACKGROUND: In the absence of evident clinical controindication heart transplantation can be performed in patients with critical degree of cardiac failure. The choice of adequate candidates for transplantation is frequently based on clinical severness but also influenced by factors as body size, blood group and so on. METHODS: To identify the presence of prognostic factors for patients with high risk of death, clinical, hemodynamic and therapeutic features of 70 patients (mean age 44.8 +/- 13.8) with critical cardiac failure (64 patients in IV class N.Y.H.A.) have been reviewed. Most of them were affected by dilated or ischemic cardiomyopathy. RESULTS: All patients were admitted to Cardiac Intensive Care Unit, 13 patients received transplantation, 24 were discharged and 33 died. Univariate analysis evidenced, that in the group of patients who died, sepsis (p = 0.0003), renal (p = 0.04) and liver function impairment (P = 0.007) occurred significantly more frequent. The differentiated use of catecholamines (P = 0.0007) and of vasodilators (P = 0.007), the need of mechanical ventilation (P = 0.0001) and the need of hemodialysis (P = 0.02) resulted significantly higher in the group of dead patients where mean arterial pressure (p = 0.01) and mean systemic resistances (P = 0.04) resulted significantly lower. With multivariate analysis were identified following independent risk factors of death: male sex, infections, mechanical ventilation, differentiated use of vasodilators, mean arterial pressure and mean pressure in pulmonary artery. CONCLUSIONS: As predictive risk factors of death in patients with critical cardiac failure and awaiting transplantation resulted: sex, the presence of infection, mechanical ventilation and differentiated use of vasodilators whereas hemodynamic parameters did not result of important predictive value.

Adult↗