Extent, determinants and clinical importance of pressure recovery in patients with aortic valve stenosis

AIMS

In experimental studies the recovery of pressure distal to stenotic valve orifices has been well described. We evaluated the extent, determinants, and clinical importance of pressure recovery in patients with aortic valve stenosis.

METHODS AND RESULTS

The study was performed in 37 patients with aortic valve stenosis, in whom cardiac catheterization was performed and left ventricular and aortic pressures were determined using a high-fidelity multi-tip micromanometer catheter. To register the pressure waveforms accurately the catheter was positioned so that the proximal micromanometer was in the left ventricle, the second at the site of minimal pressure in the vena contracta, and the third (the most distal) in the ascending aorta 16 cm further downstream. The amount of pressure recovery within the ascending aorta was up to 44% of the maximal pressure drop. The index pressure recovery was directly correlated to the Gorlin-derived aortic valve area (r=0.80) and indirectly correlated to the ratio of aortic valve area and the cross-sectional area of the ascending aorta.

CONCLUSIONS

This clinical study confirmed experimental data, that index pressure recovery is dependent on the ratio of the effective valve area and the cross-sectional area of the ascending aorta. Pressure recovery may need to be considered in patients with mild to moderate aortic stenosis and with a small cross-sectional area of the ascending aorta.

[The ultrasonic measurement of the endothelial function of the brachial artery in suspected coronary heart disease]

BACKGROUND AND OBJECTIVE

A positive correlation between the presence of coronary artery disease (CAD) and peripheral endothelial dysfunction (ED) of the brachial artery has been shown in several studies. Aim of the present study was to evaluate whether the non-invasive determination of ED could also be used as a screening test in patients suspected of having CAD.

PATIENTS AND METHODS

122 patients were included. 112 had an exercise-ECG before hospital admission. Preceding coronary angiography, FMD% was measured by high-resolution ultrasound (13 Mhz). Longitudinal scans of the brachial artery were done at rest, during reactive hyperemia and after the sublingual administration of nitroglycerin.

RESULTS

In 101 of the 122 patients the presence of CAD was diagnosed by angiography, whereas 21 patients had normal coronary arteries. The extent of the vasodilation (FMD%) was found to be largely independent of the resting vessel diameters (FMD%/vessel diameter at rest: r = -0.32767 p = 0.0002). FMD% was significantly higher in patient without CAD than in the CAD group (7.01 +/- 3.5% vs. 3.73 +/- 4.11%, p < 0.001). Comparison of sensitivity and specificity to predict the presence of CAD between FMD% [sensitivity 71.3%, specificity 81%] and exercise-ECG [sensitivity 82.4%, specificity 57.1%] gave similar results. No correlation was found between the degree of the impairment of FMD% and the severely of CAD.

CONCLUSION

The determination of peripheral ED was found to be a sensitive and specific measure for predicting the presence of CAD in our cohort. Since this approach is non-invasive, non-radioactive and cost-effective it warrants further evaluation of its role as an additional screening test in patients clinically suspected of having CAD.

Occurrence of a saccular pseudoaneurysm formation two weeks after perforation of the left anterior descending coronary artery during balloon angioplasty in acute myocardial infarction

We describe the occurrence of a localized saccular pseudoaneurysm in a 69-year-old patient 2 weeks after perforation of the left anterior descending coronary artery during balloon angioplasty in acute myocardial infarction. The therapy of perforations requires prolonged balloon inflations, perfusion balloons, covered stents, or surgery. Coronary peudoaneurysm formations are rare; their therapy requires covered stents or surgery. Cathet. Cardiovasc. Intervent. 47:341-346, 1999.

Clinical significance of thrombocytopenia during a non-ST-elevation acute coronary syndrome. The platelet glycoprotein IIb/IIIa in unstable angina: receptor suppression using integrilin therapy (PURSUIT) trial experience

BACKGROUND

The significance of thrombocytopenia in patients experiencing an acute coronary syndrome (ACS) has not been examined systematically. We evaluated this condition in a large non-ST-elevation ACS clinical trial, with particular interest paid to its correlation with clinical outcomes.

METHODS AND RESULTS

Patients presenting without persistent ST elevation during an ACS were randomized to receive a double-blind infusion of the platelet glycoprotein (GP) IIb/IIIa inhibitor eptifibatide or placebo in addition to other standard therapies including heparin and aspirin. The primary end point was death/nonfatal myocardial infarction (MI) at 30 days, whereas bleeding and stroke were the main safety outcomes. Thrombocytopenia (nadir platelet count <100x10(9)/L or <50% of baseline) occurred in 7.0% of enrolled patients. The time to onset was a median of 4 days in both treatment arms. Patients with thrombocytopenia were older, weighed less, were more likely nonwhite, and had more cardiac risk factors. These patients experienced significantly more bleeding events: they were more than twice as likely to experience moderate/severe bleeding after adjustment for confounders. Univariably, ischemic events (stroke, MI, and death) occurred significantly (P<0.001) more frequently in patients with thrombocytopenia; multivariable regression modeling preserved this association with death/nonfatal MI at 30 days. Neither the use of heparin or eptifibatide was found to independently increase thrombocytopenic risk.

CONCLUSIONS

Although causality between thrombocytopenia and adverse clinical events could not be established definitively, thrombocytopenia was highly correlated with both bleeding and ischemic events, and the presence of this condition identified a more-at-risk patient population.

Local drug delivery: impact of pressure, substance characteristics, and stenting on drug transfer into the arterial wall

Injection parameters for local drug delivery are frequently determined by studies with marker substances. However, the pharmacologic properties of the actual drug may influence delivery efficiency and lead to different results. Aim of this study was to assess the delivery capacities of two device-drug combinations in order to verify this approach for further in vivo studies. Tritiated (3H) preparations (5 ml) of the hydrophylic low-molecular-weight heparin reviparin and the lipophilic taxane paclitaxel were injected into the left anterior descending artery of freshly explanted porcine hearts with the Infusasleeve II catheter system. A balloon support pressure of 6 atm and infusion pressures of 40, 60, 80, or 100 psi were used. In three additional groups, reviparin was injected following stent implantation and paclitaxel was injected prior to or following stent implantation. Arteries along with surrounding myocardium were harvested. The artery was carefully dissected, and artery and myocardium were separately homogenized, and activity was measured. Of the totally delivered activity, 0.09%+/-0.03% (40 psi) to 0.17%+/-0.13% (100 psi) of reviparin and 2.03%+/-0.67% (60 psi) to 2.68%+/-1.57% (100 psi) of paclitaxel were found in the vessel wall. The results for different injection pressures were not significantly different for either drug. The percentage activity delivered to the vessel wall was substantially larger in the paclitaxel group as compared to reviparin delivery (P < 0.01 at 60, 80, and 100 psi). The mean concentration of reviparin in the artery was 20 to 33 times higher than in the myocardium. For paclitaxel the factors were 110 to 243. Stent implantation prior to or following local delivery did not result in a different delivery efficiency. The results demonstrate that the characteristics of the delivered drug contribute largely to the delivery efficiency. Using identical injection parameters, drug concentrations in the arterial wall were significantly higher for the lipophilic paclitaxel as compared to the hydrophilic reviparin. Stenting of the artery did not influence delivery efficiency.

[Risk of invasive diagnosis with retrograde catheterization of the left ventricle in patients with acquired aortic valve stenosis]

In patients with aortic valve stenosis, the determination of the transstenotic pressure gradient is usually performed by cardiac catheterization with retrograde passage of the aortic valve. The aim of this study was to determine retrospectively the risk of the invasive examination with retrograde catheterization of the left ventricle and predictors for an increased risk. From 1984 to 1995, 457 patients (63 +/- 11 years) with aortic stenosis were investigated in the Medizinische Klinik Tübingen. In 435 patients (95.2%), the retrograde catheterization of the left ventricle was successful; in 19 cases a transseptal left heart catheterization was performed, and in 3 patients an invasive determination of the pressure gradient was not assessed. Complications occurred in 39 patients (8.5%). 5 patients died due to the catherization procedure (mortality rate 1.1%), 2 of them as a consequence of perforation of the left ventricle, one patient of heart failure, one of myocardial infarction, and another of fulminant pulmonary embolism. Four procedures (0.9%) were complicated by cerebral embolism, in 3 patients a pericard tamponade occurred, and in one case caused by transseptal punction of the interatrial septum. The most complications were peripheral vascular problems in 19 patients (4.2%). Predictors for increased risk dur to retrograde catheterization were age > 70 years (p = 0.008) and aortic valve area < or = 0.7 cm2 (p = 0.02). patients with a doppler echocardiographic instantaneous pressure gradient > or = 70 mm Hg were more likely to sustain a complication (p = 0.04). The retrograde catheterization of a stenotic aortic valve was successful in most cases. In approximately 2% of patients, complications occurred which can be attributed directly to retrograde catheterization and with significant higher frequency in patients over 70 years and with severe stenosis. Especially in these cases, invasive determination of the gradient should not be performed if reliable doppler echocardiographic information is available.

Reduction of restenosis by vessel size adapted percutaneous transluminal coronary angioplasty using intravascular ultrasound

Restenosis following percutaneous transluminal coronary angioplasty (PTCA) remains a serious problem in interventional cardiology. Recent trials using stent implantation have proposed a reduction in restenosis, presumably due to a higher initial luminal gain. This study was conducted to evaluate if the short- and long-term results following conventional PTCA may be favorable, if balloon dilation was performed according to measurements gained by intravascular ultrasound (IVUS) (vessel size adapted PTCA). The use of intracoronary stents might be omitted if comparable long-term results could be achieved by this modified technique of balloon angioplasty. This unicenter and nonrandomized pilot trial was initiated in January 1995 with 252 patients who had 271 lesions. IVUS was performed before and after intervention to determine the external elastic membrane (EEM) diameter at the lesion site. The balloon catheter was sized according to the EEM diameter measured by IVUS (EEM 10%). The mean balloon diameter was 4.1 +/- 0.5 mm, the dilation time 130 +/- 60 seconds with a balloon pressure of 7.0 +/- 2.0 atm. Clinical acute and 1-year long-term follow-up were obtained for all patients and follow-up angiography in 71% of patients. Acute events occurred postinterventionally in 5 patients (2%). The cumulative event rate during long-term follow-up was 14%. The angiographic restenosis rate (diameter stenosis >50%) after 1 year was 19%. Vessel size adapted PTCA using IVUS led to favorable acute and long-term results with a low restenosis rate and a low 1-year clinical event rate. Despite dissections that occur frequently using large balloon sizes, an increased rate of major complications did not occur, indicating a safe procedure and substantiating the philosophy of "therapeutic dissections." The results need to be verified in a randomized trial.

Paraoxonase 192 Gln/Arg gene polymorphism, coronary artery disease, and myocardial infarction in type 2 diabetes

Paraoxonase is an HDL-associated enzyme implicated in the pathogenesis of atherosclerosis by protecting lipoproteins against peroxidation. Its biallelic gene polymorphism at codon 192 (glutamine/arginine) has been associated with coronary artery disease (CAD). To further evaluate the role of this paraoxonase gene polymorphism for CAD in type 2 diabetes, we determined the paraoxonase genotype in 288 type 2 diabetic patients (170 with and 118 without angiographically documented CAD). The paraoxonase 192 Gln/Arg genotype was assessed using polymerase chain reaction followed by AlwI digestion. The frequency of the Gln allele was 0.656 in the CAD patients and 0.746 in the controls (chi2 = 5.36, P = 0.02). Compared with the Gln/Gln genotypes, the age-adjusted odds ratio for CAD was 1.78 (95% CI 1.08-2.96, P = 0.02) in subjects carrying at least one Arg allele. In the multivariate analysis, this association was even stronger after correction for the possible confounders age, sex, smoking history, and hypertension. Among current and former smokers, the odds ratio (OR) for having CAD among patients with at least one Arg allele was 3.58 (1.45-9.53, P < 0.01). The paraoxonase Arg allele was not associated with the history of myocardial infarction (OR 1.20 [0.73-1.99, NS]), but was with the extent of CAD (OR for three-vessel disease 1.92 [1.15-3.27, P = 0.01]). Our data indicate that the 192 Arg allele of the human paraoxonase gene is a risk factor for CAD but not myocardial infarction in type 2 diabetic patients, a risk factor further modified by cigarette smoking. This risk could possibly be explained by a reduced ability of the paraoxonase Arg isoform to protect lipoproteins against peroxidation.

Frequency and efficacy of glycoprotein IIb/IIIa therapy for treatment of threatened or acute vessel closure in 1332 patients undergoing percutaneous transluminal coronary angioplasty

BACKGROUND

Glycoprotein (GP) IIb/IIIa antagonists are potent inhibitors of thrombocyte aggregation and thrombus formation. Several large-scale randomized studies for prevention of thrombotic complications have shown their potential to reduce these complications in patients undergoing percutaneous transluminal coronary angioplasty (PTCA). It was the purpose of this observational trial to assess the frequency and efficacy of primary GP IIb/IIIa antagonist therapy as a bailout procedure for the prevention of threatened or abrupt vessel closure in patients after conventional balloon angioplasty.

METHODS AND RESULTS

From January 1995 to December 1996, PTCA was performed in 1332 consecutive patients with coronary artery disease. Overall, threatened or abrupt vessel closure was observed in 63 (4.7%) patients of the patient population. In these patients, abciximab was administered (0.25 mg/kg body weight intravenous bolus, followed by a 12-hour infusion at 10 mg/min). Repeat PTCA was performed shortly after the administration of the abciximab bolus to achieve an optimal flow at the time of active GP IIb/IIIa therapy. One day after intervention, early follow-up angiography was performed. Follow-up after 1 year included the clinical status of all patients and, if possible, control angiography. Overall, the preintervention minimum lumen diameter (MLD) measured 0.74 +/- 0.27 mm and the diameter stenosis was 75% +/- 24%. The postintervention MLD increased to 2.60 +/- 0.55 mm, and the diameter stenosis decreased to 24% +/- 22%. At 24-hour angiographic follow-up, the MLD decreased to 2.47 +/- 0.49 mm and the diameter stenosis increased to 28% +/- 24%, correspondingly. The thrombus score decreased from 2.8 +/- 1.5 before abciximab treatment to 0.88 +/- 0.81 after abciximab treatment, and Thrombolysis In Myocardial Infarction flow grade increased from 2.1 +/- 1.1 to 2.9 +/- 0.3. In-hospital events occurred in 2 patients. Both patients had to undergo emergency coronary artery bypass grafting (1 of these patients died). During long-term follow-up, there were 10 clinical events (1 death, 3 repeat PTCA, and 6 coronary artery bypass graft operations for restenosis at the target lesion site). The cumulative event rate after 1 year (including acute and follow-up events) for both the total group and for the target vessel was 19%.

CONCLUSIONS

The results of this study demonstrate that GP IIb/IIIa antagonists are able to prevent vessel occlusion after PTCA complicated by subsequent threatened or abrupt vessel closure. In these situations, GP IIb/IIIa antagonists provide effective treatment for the reduction of thrombus at the target lesion site, which constitutes a second key element for threatened or abrupt vessel occlusion.

Comparison of peripheral endothelial dysfunction and intimal media thickness in patients with suspected coronary artery disease

OBJECTIVE

Flow associated dilatation (FAD%) and intimal media thickness are established markers of early atherosclerosis. This study aimed to compare the ability of the non-invasive measurements FAD% and intimal media thickness to predict coronary artery disease.

METHODS

FAD% and intimal media thickness were determined using high resolution ultrasound in 122 patients with clinically suspected coronary artery disease before coronary angiography. Results are given as mean (SD).

RESULTS

Patients with coronary artery disease had reduced FAD% compared with those with angiographically normal coronary vessels (3.7 (4.1) v 7.0 (3.5)%, p < 0.001), whereas intimal media thickness tended to be increased in patients with coronary artery disease (0.58 (0.35) v 0.47 (0.11)mm, p = 0.054). There was a negative correlation between FAD% and intimal media thickness (R = -0.317, p = 0.0004). Receiver operating characteristic analysis showed that FAD% < or = 4.5% predicted coronary artery disease with a sensitivity of 0.71 (95% confidence interval 0.61 to 0.80) and a specificity of 0.81 (0.58 to 0.95). In contrast, intimal media thickness showed a positive correlation with the extent of coronary artery disease (number of vessels with a lesion > or = 50%) (R = 0.324, p = 0.0003), without a clear cut off point.

CONCLUSIONS

In patients with clinically suspected coronary artery disease, FAD% discriminates between the presence or absence of coronary artery disease, whereas intimal media thickness is associated more with the extent of coronary artery disease.

Antiproliferative stent coatings: Taxol and related compounds

The implantation of stents can prevent vessels from post interventional elastic recoil and appears to limit adverse remodelling. In order to inhibit in-stent restenosis, an additional release of antiproliferative agents from the stent itself might lead to a synergistic reduction of lumen renarrowing. Paclitaxel (Taxol) is a microtubule-stabilizing agent with potent antiproliferative activity. Unlike other antimitotic agents of the colchicine type, it shifts the microtubule equilibrium towards assembly, leading to reduced proliferation, migration and signal transduction. Moreover, important biological processes, such as the activation of some protein kinases, are associated with microtubule depolymerization and are therefore inhibited by paclitaxel. Several experimental in vitro and in vivo studies using local paclitaxel delivery to inhibit proliferation and lumen renarrowing have been performed already--with very encouraging results.

Incidence, outcome and prediction of early clinical events following percutaneous transluminal coronary angioplasty. A comparison between treatment with reviparin and unfractionated heparin/placebo (results of a substudy of the REDUCE trial)

BACKGROUND

Unfractionated heparin and its low molecular weight fragments possess antithrombotic properties, properties that are routinely exploited in coronary angioplasty (PTCA).

OBJECTIVES

In the setting of the REDUCE trial, a randomized, double-blind, multicentre trial, the occurrence of acute or early clinical events was compared in patients treated with either unfractionated heparin/placebo or low molecular weight heparin (reviparin).

METHODS AND RESULTS

Six hundred and twelve patients with native coronary artery obstructions randomized between unfractionated heparin/placebo and reviparin, were analysed. Baseline characteristics were similar in both groups. Using the intention-to-treat analysis, major acute or early events (myocardial infarction, re-PTCA, bypass surgery, death) occurred in 42 patients (7%), 29 in the control group and 13 in the treatment group (P=0.027). In order to develop a predictive model for the risk of early events following coronary balloon angioplasty, clinical as well as pre-PTCA and procedural characteristics were analysed. Thrombi at the treated lesion site (P=0.02), dissection (P<0.001), lesion type B2 and C according to the NHLBI classification (P<0.001), diameter stenosis >50% post-PTCA (P<0.001), and length of stenosis >20mm (P=0.005) were significantly associated with the occurrence of acute events. By multiple logistic regression analysis, in which these variables and the treatment regimen were entered, dissection (P=0.042), diameter stenosis >50% (P<0.028) and lesion type B2 and C (P=0.017) were found to be independently predictive of early adverse events. Bleeding complications were similar in the two treatment groups.

CONCLUSIONS

Reviparin, given in a very early stage of vascular injury, compares favourably with unfractionated heparin/placebo, by reducing abrupt closure and acute-phase adverse outcome following PTCA. With respect to the evaluated risk factors for acute events, the positive effect of reviparin on early adverse outcome after PTCA may be due to improved antithrombotic properties as compared to unfractionated heparin.

Local and systemic delivery of low molecular weight heparin following PTCA: acute results and 6-month follow-up of the initial clinical experience with the porous balloon (PILOT-study). Preliminary Investigation of Local Therapy Using Porous PTCA Balloons

The purpose of this study was to assess safety and feasibility of intracoronary delivery of reviparin using a porous balloon following percutaneous transluminal coronary angioplasty. The 2.7 mm porous balloon used in this study had 35 holes arranged in a spiral pattern. Eighteen patients (male n = 10, female n = 8, age 63 +/- 9 years) undergoing successful PTCA in coronary arteries with a vessel diameter of 2.5 to 3.0 mm determined by online QCA (LAD = 11, RCX = 3, RCA = 4) were included. They received a bolus of 7,000 anti-Xa-IU reviparin followed by local delivery of 1,500 anti-Xa-IU in 4 ml with an injection pressure of 2 atm. The patients received additionally 10500 anti-Xa-units intravenously during the following 24 hours and a daily dose of 7000 anti-Xa-units reviparin subcutaneously for the following 28 days. Angiograms were obtained before and after PTCA, directly after local delivery, at 24 hours postintervention and after 6 months. The primary success rate was 100%. Quantitative coronary angiography showed a minimum luminal diameter of 0.42 +/- 0.14 mm before PTCA, 1.87 +/- 0.45 after PTCA, 1.67 +/- 0.43 after LDD, 1.63 +/- 0.46 after 24 hours, and 1.06 +/- 0.6 after 6 months. Angiographic follow-up was obtained in all patients. No major complications occurred during the 6-month follow-up period. The angiographic restenosis rate was 28% (5/18) at follow-up. This study demonstrates safety and feasibility of local intracoronary delivery of reviparin with a porous balloon following PTCA even in smaller diameter coronary arteries.

Local and systemic delivery of low molecular weight heparin stimulates the reendothelialization after balloon angioplasty

OBJECTIVE

Recent investigations revealed the importance of endothelial cell integrity and function in the pathogenesis of restenosis after angioplasty. Agents which stimulate reendothelialization may prevent restenosis after interventional procedures. The results of in vitro studies suggested that heparin and low molecular weight heparin administration may enhance the recovery of the endothelium. In this study the extent of endothelial denudation and the occurrence and time course of endothelial regeneration after experimental balloon angioplasty followed by subcutaneous or local delivery of low molecular weight heparin was investigated.

METHODS

A total of 102 rabbits were included in the study. An atheromatous plaque was induced by electrical stimulation in the right carotid artery of the animals. All animals underwent balloon angioplasty. Thirty-two rabbits received no further medical treatment. Twenty-five rabbits received subcutaneous low molecular weight heparin reviparin (400 anti-Xa-units/day) during the following 7 days. In 25 animals the dilated arterial segments were treated locally with reviparin (1500 anti-Xa-units/4 ml, 2 atm) using a porous balloon (2.5 mm, 35 holes, diameter 75 microns). Twenty animals served as control group without intervention. The vessels were excised 3, 7, 14, 28 and 56 days following intervention. Sections were stained with an antibody against von Willebrand factor and PECAM 1 to confirm the endothelial origin of the lining cells. After bromodeoxyuridine labeling, the extent of proliferation was determined by using a monoclonal antibody. In addition, morphometric analysis of the intimal and medial area was performed.

RESULTS

Three days after balloon angioplasty histomorphological analysis showed a reduction of about 60% of the preinterventional endothelial cell number in all three groups. Already one week after intervention there was a significantly higher number of endothelial cells in both groups of low molecular weight heparin treated animals compared to the untreated group (s.c. group 144 +/- 33, local group 142 +/- 32 versus untreated 79 +/- 17 endothelial cells, p < or = 0.05). This significant difference was maintained during the following four weeks and demonstrated a 2-fold increase in endothelial proliferation in the heparin treated animals compared with the untreated group. In addition, immunohistological examination showed a significant decrease in smooth muscle cell proliferation in the s.c. and local reviparin treated animals and a subsequent reduction of intimal thickening.

CONCLUSION

Local delivery of low molecular weight heparin promotes reendothelialization and contributes to the inhibition of smooth muscle cell proliferation.

Lesion morphology assessed by pre-interventional intravascular ultrasound does not predict the incidence of severe coronary artery dissections

AIMS

Coronary artery dissections are common findings following percutaneous transluminal coronary angioplasty and occur with an incidence of approximately 20% to 40%. The purpose of this study was to evaluate the impact of intravascular ultrasound for the prediction of severe dissections by pre-interventional analysis of lesion morphology and plaque composition.

METHODS AND RESULTS

Pre- and post-interventional intravascular ultrasound was performed in 197 patients with 205 lesions. Using intravascular ultrasound criteria, 24 lesions were classified as soft (hypo- or iso-echogenic), 73 as intermediate (hyper-echogenic) and 108 as calcified (calcific arc > 90 degree of the vessel circumference). Additionally, calcium localization was defined as subendothelial, central or deep. The incidence of dissections was 37.5% in patients with soft lesions, 24.7% in patients with intermediate and 36.1% in patients with calcified lesions. In calcified lesions, the occurrence of severe dissections was not dependent on the localization of calcium deposits. The procedural parameters were similar in all patients. The minimal inflation pressure, however, was significantly higher in calcified lesions (P < 0.01).

CONCLUSION

Assessment of lesion morphology by intravascular ultrasound cannot predict the occurrence of severe dissections following percutaneous transluminal coronary angioplasty. Furthermore, despite significantly higher inflation pressures in heavily calcified lesions, the incidence of dissections was found to be comparable in all lesions.

Dynamic regulation of beta-adrenergic receptors by endothelin-1 in smooth-muscle cells

Elevated endothelin-1 (ET-1) levels are found in atherosclerosis, myocardial ischemia, and heart failure, and are correlated with increased mortality rates. Contrary to expectations, elevations of endogenous ET-1 levels in transgenic mice are not associated with increases in arterial blood pressure or with vasospasm, although these effects can be observed after i.v. ET-1 administration. The aim of this study was to determine the regulatory effects of ET-1 on the expression of vasodilator beta-adrenergic receptors and their ability to activate adenylyl cyclase. Smooth-muscle cells were incubated with ET-1 (10(-7) mol/L) for 3 days. The density of ET-1 or beta-adrenergic receptor binding sites was determined using a radioligand binding procedure. Adenylyl cyclase activity was measured to assess any functional changes in the beta-adrenergic receptor density. ET-1 incubation reduced ET-1 binding sites by 70%. In contrast, the beta-adrenergic receptor density increased from 354 +/- 35 to 538 +/- 50 fmol/mg protein (p < 0.01; n = 7) after 3 days. ET-1 increased beta-adrenergic receptors dose-dependently. Incubation with ET-1 for different periods of time showed an initial decrease of 30% after 6 h of ET-1 incubation. However, after 24 h ET-1 induced an increase of beta-adrenergic receptors, reaching a maximal amount after 48 h. An increased stimulation of beta-adrenergic receptor-activated adenylyl cyclase was observed after 3-day ET-1 incubation compared to controls. These data demonstrate that chronic ET receptor activation by ET-1 results in a functionally significant increase in beta-adrenergic receptor density and adenylyl cyclase activity.

Downregulation of beta-adrenergic receptors by low density lipoproteins and its prevention by beta-adrenergic receptor antagonists

OBJECTIVE

Vasodilation by beta-adrenergic receptors of smooth muscle cells appears to be impaired early after the onset of hypercholesteremia. The aim of this study was to analyze the modulation of beta-adrenergic receptor density and adenylyl cyclase activity in the presence of moderately elevated concentrations of LDL. The effects of beta 1- and beta 2-adrenergic receptor antagonists on LDL-induced receptor changes were studied.

METHODS AND RESULTS

Media explants of porcine coronary arteries were incubated with moderately elevated LDL concentrations (0.7-3.9 mmol/l). The density of beta-adrenergic receptors was determined in plasma membranes using the radioligand [125I]iodocyanopinodolol. LDL (3.9 mmol/l) resulted in a decrease of beta-adrenergic receptor density (control 137 +/- 5 vs. 89 +/- 7 fmol/mg protein, P < 0.01). After removal of LDL and cultivation for an additional 3 days beta-adrenergic receptors increased to 129 +/- 5 fmol/mg. In the presence of the beta 1- or beta 2-adrenergic receptor antagonists the LDL-mediated decrease was inhibited. Addition of metoprolol after 3 days of LDL incubation caused a restoration of receptor density. The basal, isoproterenol- and forskolin-stimulated adenylyl cyclase activities were increased after LDL incubation by 180, 110 or 80%, respectively.

CONCLUSION

Moderately elevated LDL levels decreased beta-adrenergic receptor density while adenylyl cyclase activity was simultaneously increased. beta 1- or beta 2-adrenergic receptor antagonists prevented this receptor decrease and might preserve the beta-adrenergic receptor density in the presence of moderately elevated LDL levels.

Accuracy of computer-based quantification of aortic valve stenosis

In patients with aortic valve stenosis, the quantification of stenosis is usually performed using fluid-filled catheters and a computerized calculation program. The aim of this study was to determine the accuracy of this technique in comparison to the manual planimetry of the area between the curves of a simultaneous registration, using a multitip micromanometer catheter. The study was performed in 19 patients, in whom left and right heart catheterization was warranted. Systolic left ventricular and aortic peak pressures were significantly overestimated using a fluid-filled catheter (206 +/- 35 vs. 199 +/- 37 mm Hg, P = 0.0003, and 148 +/- 18 vs. 143 +/- 21 mm Hg, P = 0.0052). However, peak-to-peak pressure gradients were identical comparing both techniques (58 +/- 31 vs. 56 +/- 32 mm Hg, r = 0.983). The mean pressure gradients and aortic valve areas based on simultaneous measurements of left ventricular and aortic pressures by micromanometer catheters were identical to the values determined by a computer-based program using fluid-filled catheters (54 +/- 21 vs. 52 +/- 21 mm Hg, r = 0.923, P < 0.05, and 0.75 +/- 0.25 vs. 0.77 +/- 0.25 cm2, r = 0.935). Thus, the conventional use of fluid-filled catheters and of a computerized calculation of aortic valve area is valid for quantification of aortic stenosis in patients with sinus rhythm and without significant aortic regurgitation.

[Advantages in using intravascular ultrasound in percutaneous transluminal coronary angiography]

Recent randomized clinical trials reported a reduction of restenosis using intracoronary stents and suggested that this restenosis reduction is a result of the higher immediate luminal gain in comparison to conventional percutaneous transluminal coronary angioplasty (PTCA). The hypothesis of this study is based on the assumption that IVUS guided PTCA leads to equivalent long term PTCA results as compared to PTCA and the additional placement of a stent. Thus, the purpose of this non-randomized single center study was to evaluate (1) the safety and efficacy and (2) the long term outcome of vessel size adapted PTCA in patients with native coronary lesions. From April 1995 to March 1996 the morphological dimensions of the target lesions were determined in 107 patients with 108 lesions by intravascular ultrasound prior to conventional balloon angioplasty. Quantitative parameters of the vascular dimensions were assessed on-line and the diameter of the balloon catheter was adapted to the external elastic membrane (EEM) at the lesion site minus 10%. Using this strategy, mean balloon diameter was 4.1 +/- 0.5 mm. Acute and one year clinical follow-up results were obtained in all 107 patients. Angiographic success was defined as a final percent diameter stenosis of < 30%. The following criteria determined by postinterventional IVUS were also used to define a successful PTCA: luminal CSA gain of > 30% with an angiographically patent flow (TIMI 3). Acute events occurred in two patients (one death and one successful acute surgical revascularisation). During one year follow-up, 11 patients had a clinical event including death, Q-wave MI, surgical revascularisation, and repeat PTCA. In 83 patients (78%), control angiography was performed and revealed an angiographic restenosis rate of 21% using the NHLBI criterion of a diameter stenosis > 50%

CONCLUSION

The use of balloon diameters following these measurements is safe in the acute setting with a low number of in hospital events and effective in reducing clinical events as well as angiographic restenosis rates during one year follow-up. These promising results warrant verification in larger scale randomized trials.

Insertion/deletion polymorphism of the angiotensin I-converting enzyme gene is associated with coronary artery plaque calcification as assessed by intravascular ultrasound

OBJECTIVES

We evaluated the influence of the insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene on coronary plaque morphology and calcification in patients with angiographically documented coronary artery disease (CAD).

BACKGROUND

The ACE I/D polymorphism has been associated with an increased risk of myocardial infarction in patients with the DD genotype but not with the presence of native CAD.

METHODS

We studied 146 patients undergoing percutaneous transluminal coronary angioplasty for stable angina pectoris by means of preinterventional intravascular ultrasound (IVUS). Qualitative and quantitative criteria were used to classify the target lesions as poorly or highly echoreflective or as calcified. Genomic deoxyribonucleic acid was analyzed by polymerase chain reaction (PCR) to identify the I/D polymorphism, with a second insertion-specific PCR in DD genotypes to prevent mistyping.

RESULTS

The ACE genotype groups (DD 46, ID 68, II 32) were well matched for the basic characteristics. Patients with the DD genotype had significantly more calcified lesions (DD 80%, ID 57%, II 66%; unadjusted odds ratio [OR] 2.88, 95% confidence interval [CI] 1.30 to 6.92, p = 0.008) and more calcifications >180 degrees of the vessel circumference (DD 22%, ID 10%, II 6%; OR 2.80, 95% CI 1.05 to 7.63, p = 0.03). The prevalence of myocardial infarction was not significantly associated with coronary calcification (OR 1.44, 95% CI 0.72 to 2.88, p = 0.31).

CONCLUSIONS

Patients with CAD and the ACE DD genotype have a significantly higher incidence and greater extent of coronary lesion calcification, as determined by IVUS. This finding indicates that the ACE I/D gene polymorphism is related to the development or progression of atherosclerotic plaque calcification.

Acute and one year follow-up results after vessel size adapted PTCA using intracoronary ultrasound

AIMS

Recent randomized clinical trials have reported a reduction in restenosis with intracoronary stents and have suggested that this restenosis reduction is a result of the higher immediate luminal gain, in comparison to conventional percutaneous transluminal coronary angioplasty (PTCA). The hypothesis of this study is based on the assumption that PTCA results may be optimized by determining vessel dimensions before intervention, using intravascular ultrasound. This may lead to long-term PTCA results equivalent to PTCA and the additional placement of a stent. The purpose of this prospective non-randomized single-centre study was to evaluate (1) the safety and efficacy and (2) the long-term outcome of vessel-size adapted PTCA in patients with native coronary artery obstructions.

METHODS AND RESULTS

From January 1995 to December 1995 the morphological dimensions of target lesions were determined in 144 patients with 152 lesions by intravascular ultrasound prior to conventional balloon angioplasty. Quantitative assessment of the vascular dimensions were assessed on-line and the diameter of the balloon catheter was adapted to the external elastic membrane diameter at the lesion site. Using this strategy, mean balloon diameter was 4.0 +/- 0.5 mm and mean pressure for complete balloon expansion was 7 +/- 2 atmospheres. Acute and one year follow-up results were obtained in all 144 patients. Acute events occurred in two patients (one death and one acute surgical revascularization). During one year follow-up, 16 patients (12%) had a clinical event including one cardiac death, two transmural myocardial infarctions, 10 repeat PTCAs within the target lesion and three elective coronary artery bypass grafts (CABG). In 75% (n:112) control angiography was performed and revealed an angiographic restenosis rate of 21% using the NHLBI criteria of a diameter stenosis > 50%.

CONCLUSION

Intravascular ultrasound provides an accurate and precise description of vascular dimensions at the site of the stenotic lesion. The use of balloon diameters following these measurements appears to be (1) safe in the acute setting with a low number of in hospital events and (2) gives a low restenosis rate and number of clinical events at one year follow-up. These promising results warrant verification in larger-scale randomized trials.

[The influence of coronary artery dissection on long-term outcome after percutaneous transluminal coronary angioplasty]

The influence of a coronary dissection on long-term outcome after PTCA has been controversely discussed in the past. Whereas diverse experimental studies have shown a positive relation between dissection and the incidence of restenosis, clinical trials could not document an influence of dissection on long-term outcome. However, most of the trials did not distinguish between the different morphologic configuration of the vascular dissection. Thus, the aim of the present study was to determine the influence of dissections on restenosis in regard to their amount and morphologic configuration. The prognostic importance of the National Heart, Lung, and Blood Institute classification on dissection as well as the importance of an additional classification of angiographic complications after PTCA were investigated to determine possible pathophysiologic mechanisms of the restenosis process. The study included 141 consecutive patients with 143 stable dissections after PTCA. A follow-up study was performed 13 months in mean after successful PTCA, which included clinical, symptomatic, and functional aspects of patients. In this patient population, type C dissections (Dorros et al.) showed a relevantly increased risk of a clinical adverse event (41.0%), whereas patients with a type A dissection had only a small risk of an adverse event (10.0%) over the investigation period. Type B dissections revealed an intermediate risk (18.0%), and type D dissections showed a risk of 33.3% of an adverse event, which was lower than that observed for type C dissections. The AC-classification of the postinterventional coronary morphology was a stronger predictor of an adverse outcome after PTCA (p = 0.0003) than was the Dorros-classification (p = 0.0056).

CONCLUSION

The grade of a coronary dissection was highly, positively related to an ischemic event after PTCA using both the Dorros and the AC-classification (p = 0.0056/p = 0.0003). In regard to the special association of the AC-class with the amount of vascular injury, we conclude that the amount and configuration of coronary dissection correlates with the long-term outcome after PTCA.

Smooth excimer laser coronary angioplasty (SELCA) and conventional excimer laser angioplasty: Comparison of vascular injury and smooth muscle cell proliferation

Although the excimer laser, which utilizes 'non-thermal ablation effects', has achieved encouraging results in early clinical trials, the long-term results have failed to show any advantage over conventional percutaneous transluminal coronary angioplasty (PTCA).A new system, Smooth Excimer Laser Coronary Angioplasty (SELCA), has been developed to reduce the tissue damage in the vessel wall caused by shock waves and vapour bubbles.SELCA (wavelength 308 nm, pulse duration 115 ns, repetition rate 150 Hz and energy density 50 mJ mm(-2)) lowers the amount of shock wave formation and pressure peak amplitude in the surrounding tissue by about eight times when compared to the conventional 308 nm excimer laser (ELCA). In this preclinical evaluation, this new system was compared to ELCA. Fifty New Zealand White rabbits were stimulated by repeated weak DC impulses for a period of 28 days in order to form an atherosclerotic plaque in the right carotid artery. The vessels were excised 3, 7,14 and 28 days after laser irradiation for immunohistochemical analysis.SELCA and ELCA laser treatment lead to a decrease in maximal intimal wall thickness 3 days after intervention (control: 177+/-4 microm; SELCA: 131+/-22microm; ELCA: 120 +/-33microm). In the period between 3 and 28 days, a moderate increase in intimal wall thickness was observed after SELCA treatment compared to a significant increase after ELCA (28 days after intervention: SELCA: 157+/-22microm; ELCA: 274 +/-28microm). Bromodeoxyuridine (BrdU) was applied 18 and 12 h before excision of the vessels in order to determine the percent of cells undergoing DNA synthesis. The percent of BrdU labelled SMC in the intima (control: 13 +/- 2 cells mm(-2)) increased in both groups after 3 days (SELCA: 248 +/- 107 cells mm(-2); ELCA: 162 +/- 41 cells mm(-2)) and 7 days (SELCA: 162+/- 55 cells mm(-2); ELCA: 279 +/- 119 cells mm(-2)).The present results demonstrate that vascular wall injury and increase in intimal wall thickness following SELCA are reduced in comparison to the results achieved with the conventional technique. Further trials are necessary to assess whether these improvements will lead to more favourable long-term results after excimer laser angioplasty.

Growth factor expression of human arterial smooth muscle cells and endothelial cells in a transfilter coculture system

By releasing growth factors, vascular cells can modulate proliferation and migration of neighboring cells in the arterial wall. Previous histological studies in transfilter cocultures, a culture model aimed to simulate vessel wall architecture, indicated that human arterial endothelial cells (haEC) can influence human arterial smooth muscle cell (haSMC) growth significantly. The aim of this study was to investigate the expression and secretion of various growth factors in order to better define the functional interactions between haEC and haSMC. Protein levels of platelet-derived-growth factor-AB (PDGF-AB), transforming-growth factor-beta1 (TGF-beta1), and tumor-necrosis factor-alpha (TNF-alpha) in mono- and cocultures were determined by ELISA 6, 12, 24, 48, 72 h after serum reduction. Highest PDGF-AB levels were found in monocultures with proliferative haEC, showing a peak after 24 h. In cocultures of haEC and haSMC, PDGF-AB levels were significantly lower. In contrast, neither proliferative, nor confluent haSMC released PDGF-AB significantly. Highest TGF-beta1 concentrations were detected in cocultures, followed by monocultures of haSMC and monocultures of haEC. In all cultures, TGF-beta1 levels increased in parallel with cultivation time and cell numbers, showing a maximum after 72 h. TNF-alpha could not be detected in any culture. Northern blots demonstrated a strong expression of PDGF-B chain-mRNA in haEC, but not in haSMC. PDGF-A chain and TGF-beta1-mRNA were expressed by haSMC and haEC. Addition of PDGF-AB to haSMC resulted in a potent growth stimulation, whereas TGF-beta1 and TNF-alpha exerted only moderate, divergent effects on haSMC. Histological observations in transfilter cocultures demonstrated that proliferative haEC induce the formation of fibromuscular plaques. These results suggest that proliferative haEC act as potent growth stimulators for haSMC, predominantly by PDGF-AB or -BB release.

[Low molecular weight heparin, reviparin, after PTCA: results of a randomized double-blind, standard heparin and placebo controlled multicenter study (REDUCE Study]

BACKGROUND

Unfractionated heparin and its low molecular fragments possess antiproliferative effects and have been shown to reduce neointimal smooth muscle cell migration and proliferation in response to vascular injury in experimental studies.

OBJECTIVES

The specific objective of the REDUCE trial was to evaluate the effect of a low molecular weight heparin on the incidence and occurrence of restenosis in patients undergoing percutaneous transluminal coronary angioplasty.

METHODS

The REDUCE trial is an international prospective, randomized, double-blind, multicenter study. Twenty-six centers in Europe and Canada enrolled 625 patients with single lesion coronary artery obstructions suitable for PTCA. Three hundred and six patients received reviparin as a 7000 U bolus before PTCA followed by 10,500 U as an infusion over 24 hours and then twice a day 3500 U s.c. application for 28 days. The 306 patients in the control group received a bolus of 10,000 U unfractionated heparin followed by an infusion of 24,000 U over 24 hours. These patients then received 28 days of s.c. placebo injections. The primary endpoints were efficacy (defined as a reduction in the incidence of major adverse events, i.e., death, myocardial infarction, need for reintervention or bypass surgery), absolute loss of minimal luminal diameter, and incidence of restenosis during the observation period of 30 weeks after PTCA.

RESULTS

Using the intention-to-treat analysis for all patients, 102 patients (33.3%) of the reviparin group and 98 patients (32%) of the control group have reached a primary clinical endpoint (relative risk = 0.98; 95% confidence limit, 0.88-1.09; p = 0.707). Likewise, no difference in late loss of minimal luminal diameter was evident for either group. Acute events within 24 hrs occurred in 3.9% of the reviparin group and in 8.2% of the control group (relative risk = 0.49; 95% confidence limit, 0.26-0.92; p = 0.027) during or immediately after the initial procedure. In the control group, 8 major bleedings occurred, and in the reviparin group, 7 major bleeding complications were observed within 35 days after PTCA.

CONCLUSIONS

Reviparin use during and after coronary angioplasty did not reduce the occurrence of major clinical events or the incidence of angiographic restenosis over 30 weeks.

Paclitaxel inhibits arterial smooth muscle cell proliferation and migration in vitro and in vivo using local drug delivery

BACKGROUND

The antineoplastic compound paclitaxel (Taxol) causes an increased assembly of extraordinarily stable microtubules. The present study was designed to characterize the effects of paclitaxel on proliferation and migration of human arterial smooth muscle cells (haSMCs) in vitro and on neointima formation in an in vivo experimental rabbit model.

METHODS AND RESULTS

Both monocultures of haSMCs and cocultures with human arterial endothelial cells (haECs) were used. Cell growth after 4, 8, and 14 days was determined in the absence or presence of platelet-derived growth factor-AB (PDGF-AB), basic fibroblast growth factor (bFGF), or thrombin. Nonstop paclitaxel exposure, as well as single-dose applications of paclitaxel for 24 hours or even 20 minutes (0.1 to 10.0 micromol/L), caused a complete and prolonged inhibition of haSMC growth up to day 14, with an IC50 of 2.0 nmol/L. Mitogens or cocultures with stimulating haECs did not significantly attenuate paclitaxel-induced effects. Immunohistochemistry showed characteristic cytoskeletal changes predominantly in the microtubule network. Additionally, in 20 male New Zealand White rabbits, intimal plaques were produced by electrical stimulation. In 10 animals, paclitaxel was locally applied by use of microporous balloons. Histologically, the intima wall area, wall thickness, and degree of stenosis were reduced significantly in paclitaxel-treated animals compared with controls.

CONCLUSIONS

Our data show that paclitaxel inhibits haSMC proliferation and migration in a dose-dependent manner in monocultures and cocultures even in the presence of mitogens. Furthermore, paclitaxel prevents neointima formation in rabbits after balloon angioplasty. The long-lasting effect after just several minutes' exposure time makes this lipophilic substance a promising candidate for local antiproliferative therapy of restenosis.

Local drug delivery with porous balloons in the rabbit: assessment of vascular injury for an improvement of application parameters

OBJECTIVES

Sufficient intramural drug concentrations with the use of porous balloon catheters can be achieved with additional vascular trauma only. However, effective delivery of a potent drug even in deeper layers of the vessel wall might outweigh these traumatic side effects. Given the porous balloon catheter, the parameters of injection pressure and applied fluid volume will influence the interventional result.

METHODS

We tested a 2.5-mm porous balloon (35 75-micron pores) in the right carotid artery of New Zealand rabbits and used injection pressures of 1, 2, and 5 atm and fluid volumes of 2 and 4 ml of low-molecular-weight heparin solution in combination with the different parameters (n = 5 animals/group). In 50 rabbits, an intimal fibromuscular plaque was induced by using the electrostimulation model. Balloon dilatation and then application of the porous balloon was performed in 30 animals, 10 animals were only electrostimulated, and 10 animals served as a control group with balloon dilatation only. The vessels were excised 7 d after intervention, stained, and analyzed histomorpologically. Anti-Xa assays revealed the extent of systemically escaped drug, and serial cuts allowed for exact determination of vessel wall injuries.

RESULTS

Effective local drug delivery could not be achieved with an injection pressure of less than 2 atm. Specific pressure-driven effects such as jet injuries could be identified. When the pressure was high enough for disruptive drug delivery (> or = 2 atm), fluid volumes of 4 ml led to loose elastic membranes and local thickening within the media.

CONCLUSIONS

Sufficient intramural drug distribution using porous balloon catheters can be achieved with low injection pressures. Different fluid volumes strongly determine the extent of additional vascular injury.

Efficacy of low-molecular-weight heparin delivery with the Dispatch catheter following balloon angioplasty in the rabbit iliac artery

Local drug delivery can be achieved with active injection systems or passive contact of a compound with the arterial wall. The Dispatch catheter allows for passive diffusion of drugs from drug compartments while preserving blood flow through the central conduit. The aim of this study was to investigate whether a reduction in neointima formation can be achieved by local delivery of a limited amount of a highly concentrated solution of the low-molecular-weight heparin Reviparin. In 16 New Zealand white rabbits, successful balloon dilatation was performed in both iliac arteries, followed by local delivery of 4 ml Reviparin (1,000 IU/ml). The arteries were harvested at 7, 28, or 56 d following the procedure. The intimal cell layers increased substantially between 7 and 28 d following balloon dilatation with or without local drug delivery. The medial cell layers showed only a little increase. Proliferation of smooth muscle cells reached an early peak after 7 d, with a significantly higher proliferation index following local delivery. The maximum amount of macrophages in the intima and media was detected after 28 d. The lumen area decreased with time and was 0.6 +/- 0.7 mm2 in the local delivery group at 56 d compared with 0.5 +/- 0.5 mm2 in the control group. In conclusion, local delivery of Reviparin with the Dispatch catheter is safe and feasible. However, the infusion of highly concentrated low-molecular-weight heparin over a short period of time did not result in a reduction of neointima formation and restenosis following balloon dilatation in the rabbit iliac artery.

Time course of smooth muscle cell proliferation after local drug delivery of low-molecular-weight heparin using a porous balloon catheter

It has been reported previously that systemic application of low molecular weight heparin (LMWH) suppresses smooth muscle cell (SMC) proliferation after balloon angioplasty in experimental studies. However, the high concentration of heparin required for a beneficial effect may cause severe bleeding complications. The ideal situation to overcome the systemic side effects would be to administer LMWH locally and deep into the arterial wall, which became possible by the development of porous balloon catheters. The in vivo feasibility of local delivery of LMWH using the porous balloon has been assessed by delivering tritium-marked LMWH into rabbit carotid arteries. The efficacy of the system was investigated by using a second injury animal model. After development of an intimal plaque by electrical stimulation, 61 rabbits were treated with the porous balloon after balloon angioplasty. In 23 rabbits, local drug delivery was accomplished with a porous balloon catheter (35 holes, hole diameter 75 microns, 2.5 mm catheter diameter). LMWH was locally administered with 4 ml (solution 375 anti-Xa-units/ml) and 2 atm. To study the extent of restenosis and morphological changes, these animals were killed 3, 7, 14, 28, or 56 d after intervention. After staining (hematoxylin, van Gieson, BrdU, RAM 11, alpha-actin) procedures to quantify SMC proliferation, intimal macrophages and morphological analysis were performed. Porous balloon treatment led to an increase in intimal SMC proliferation rate in the early stage after intervention. However, during the following time period, a significant decrease of the proliferation rate as compared with the animals treated with balloon angioplasty alone could be observed, which resulted in an only moderate increase of the intimal layer after local drug delivery compared with balloon angioplasty alone.

Low molecular weight heparin (reviparin) in percutaneous transluminal coronary angioplasty. Results of a randomized, double-blind, unfractionated heparin and placebo-controlled, multicenter trial (REDUCE trial). Reduction of Restenosis After PTCA, Early Administration of Reviparin in a Double-Blind Unfractionated Heparin and Placebo-Controlled Evaluation

OBJECTIVES

The specific objective of the REDUCE trial was to evaluate the effect of low molecular weight heparin on the incidence and occurrence of restenosis in patients undergoing percutaneous transluminal coronary angioplasty (PTCA).

BACKGROUND

Unfractionated heparin and its low molecular weight fragments possess antiproliferative effects and have been shown to reduce neointimal smooth muscle cell migration and proliferation in response to vascular injury in experimental studies.

METHODS

The REDUCE trial is an international prospective, randomized, double-blind, multicenter study. Twenty-six centers in Europe and Canada enrolled 625 patients with single-lesion coronary artery obstructions suitable for PTCA. Three hundred six patients received reviparin as a 7,000-U bolus before PTCA, followed by 10,500 U as an infusion over 24 h and then twice-daily 3,500-U subcutaneous application for 28 days. The 306 patients in the control group received a bolus of 10,000 U of unfractionated heparin followed by an infusion of 24,000 U over 24 h. These patients then underwent 28 days of subcutaneous placebo injections. The primary end points were efficacy (defined as a reduction in the incidence of major adverse events [i.e., death, myocardial infarction, need for reintervention or bypass surgery]), absolute loss of minimal lumen diameter and incidence of restenosis during the observation period of 30 weeks after PTCA.

RESULTS

Using the intention to treat analysis for all patients, 102 (33.3%) in the reviparin group and 98 (32%) in the control group have reached a primary clinical end point (relative risk [RR] 1.04, 95% confidence interval [CI] 0.83 to 1.31, p = 0.707). Likewise, no difference in late loss of minimal lumen diameter was evident for both groups. Acute events within 24 h occurred in 12 patients (3.9%) in the reviparin group and 25 (8.2%) in the control group (RR 0.49, 95% CI 0.26 to 0.92, p = 0.027) during or immediately after the initial procedure. In the control group, eight major bleeding complications occurred, and in the reviparin group, seven were observed within 35 days after PTCA.

CONCLUSIONS

Reviparin use during and after coronary angioplasty did not reduce the occurrence of major clinical events or the incidence of angiographic restenosis over 30 weeks.

Exercise Doppler echocardiography in conjunction with right heart catheterization for the assessment of mitral stenosis

RATIONALE

A new diagnostic approach is reported, which combines Doppler echocardiography and a thermodilution technique for the calculation of mitral valve area at rest and during exercise. This method was applied to determine the magnitude of mitral valve reserve (= exercise-induced increase of mitral valve are) and to assess the hemodynamic relevance of mitral stenosis.

METHODS

69 patients with mitral stenosis were included in this study. A Swan-Ganz catheter was used to measure exercise hemodynamics and transvalvular flow by a thermodilution technique. The mean transmitral flow velocity vmean was determined by continuous wave Doppler. Measurements were performed simultaneously at rest and during stepwise bicycle ergometry. Effective mitral valve area was calculated according to the continuity equation method (MVACE = Flow/vmean).

RESULTS

A significant exercise-induced increase of mitral valve area was found in the total group (rest-->25 W: 1.1 +/- 0.3-->1.3 +/- 0.4 cm2, p < 0.001). Two subgroups were defined according to the presence or absence of mitral valve reserve: delta MVA > and = 20%: group A (n = 30); delta MVA < 20%: group B (n = 39). Both groups did not differ with regard to mitral valve area at rest. However, the increase of cardiac output and stroke volume was significantly higher in group A than in group B. An effective mitral valve area at 25 W of less than 1.2 cm2 had an 80% sensitivity and an 83% specificity to detect a severe mitral stenosis.

CONCLUSIONS

Because the presence and extent of mitral valve reserve cannot be predicted under resting conditions measurements under flow-increasing interventions are necessary. Our data demonstrate that exercise Doppler in conjunction with right-sided cardiac catheterization is most useful to determine mitral valve reserve and to assess the hemodynamic relevance of mitral stenosis.

Porous balloon delivery of low molecular weight heparin in the dog coronary artery

The aim of this experimental study was to assess the safety of local delivery of low molecular weight heparin via a porous balloon in the canine coronary artery. In 16 mongrel dogs, percutaneous transluminal coronary angioplasty was performed. In addition, eight of the dogs were given 4 ml Clivarin (1500 IU) delivered locally into the coronary artery immediately after dilatation. The animals were killed after 3 or 14 days. In the animals with local administration, the results of histopathology after 3 days showed the findings to be heterogeneous with marked disruption of the internal elastic lamina in all animals, and varying degrees of medial haemorrhage, medial necrosis, perivascular haemorrhage and signs of myocardial necrosis. Similar changes, but of lesser severity, were present in the animals treated with balloon dilatation only. After 14 days, the severity of vascular and perivascular alterations (medial haemorrhage, perivascular haemorrhage, thrombus formation) was significantly lower in the local delivery group (P < 0.05), but disruption of the internal elastic lamina, as a marker of the initial trauma, was present in all the animals. The presence of residual intracoronary thrombus was only seen in the PTCA group without local delivery.

CONCLUSIONS

In this safety study, both groups showed pronounced alterations in the vessel wall 3 days following percutaneous transluminal coronary angioplasty. This changed 14 days following percutaneous transluminal coronary angioplasty when intramural injection of Clivarin resulted in a marked decrease of residual thrombus and medial as well as perivascular haemorrhage. Although the additional vessel trauma by the drug delivery technique did not result in increased complications, a careful approach with this potentially harmful procedure is essential.

Comparison of passive and active perfusion catheters: an in vitro study in a pulsatile coronary flow model

Perfusion balloon catheters are designed to provide continuous transcatheter blood flow and thereby reduce myocardial ischemia during coronary angioplasty. To compare the transcatheter flow rates of active and passive (auto-) perfusion catheters, a well-controlled experimental study was performed in a circulation model that duplicates the phasic, predominantly diastolic flow pattern of the left coronary artery. Mean diastolic coronary driving pressure varied between 20 and 100 mm Hg. For the autoperfusion catheters, a strong relationship between transcatheter flow and diastolic coronary driving pressure was found. For example, a coronary driving pressure of 80 mm Hg provided a coronary flow of 30 ml/min (RX-Perfusion [RP], ACS), 28 ml/min (Speedflow [SF], Schneider), 20 ml/min (Lifestream [LS], ACS), and 19 ml/min (Flowtrack [FT], ACS). Reduction of driving pressure to 40 mm Hg decreased the absolute transcatheter flow, which was now 16 ml/min (RP), 13 ml/min (SF), and 10 ml/min (LS and FT). The relative catheter flow (the ratio of absolute flow to baseline coronary flow rate without a catheter in place), was independent of actual coronary driving pressure and ranged between 21% +/- 1% (RP) and 14% +/- 1% (FT and LS). For the active perfusion system (Coreflo, Leocor, a maximal transcatheter flow of 82 ml/min was found. Using this active perfusion system, the relative catheter flow increased with decreasing coronary driving pressure:80 --> 40 mm Hg: 56% --> 107%. For all catheters, the distal perfusion decreased between 30% (3.0 mm RP) and 50% (3.0 mm LS) by a 0.014-inch guidewire placed through the inner channel of the catheter. Because of the strong relationship between coronary driving pressure and transcatheter flow, the residual flow through all autoperfusion catheters becomes critical (<20 ml/min), when the coronary driving pressure drops below 50 mm Hg. By contrast, active perfusion systems are independent of the actual coronary driving pressure and are therefore advantageous for prolonged dilation in patients with low aortic pressure.

Induction of cell-rich and lipid-rich plaques in a transfilter coculture system with human vascular cells

Cell-to-cell interactions are mainly involved in the control of the proliferation, migration, differentiation and function of different cell types in a wide range of tissues. In the arterial vessel wall, human arterial endothelial cells (haEC) and smooth muscle cells (haSMC) coexist in close contact with each other. In atherogenesis, haSMC can migrate from the media to the subintimal space to form fibromuscular and atheromatous plaques. In the present study, a transfilter coculture system is described, in which the interface between haSMC and confluent or proliferative haEC can be studied in detail. Cells were cocultured on the opposite sides of a porous filter which separates both cell types like the internal elastic lamina in vivo. In cocultures containing proliferative haEC, haSMC growth was significantly stimulated (33.4 +/- 5.7 cells/section, p < 0.05) compared to haSMC monocultures (22.9 +/- 2.5 cells/section) and cocultures containing confluent haEC (15.6 +/- 2.9 cells/section). If confluent haEC were injured mechanically, haSMC growth increased highly significantly (71.3 +/- 16.8 cells/section, p < 0.001). Thus, cell-rich proliferates containing 5-7 layers of haSMC embedded in extracellular matrix were formed after 14 days. On the other hand, after haSMC migration to the endothelial side had occurred, the addition of LDL and monocytes to cocultures with arterial media explants and haEC resulted in the formation of lipid-rich, low-cellular structures. After 28 days, characteristic in vitro plaque growth was induced; the plaque contained a lipid core with predominantly necrotic cells, extracellular lipid accumulations, atypically shaped lipid-loaded haSMC and macrophages, similar to in vivo foam cells, as well as an increased amount of extracellular matrix (collagen I, III and IV). These areas were surrounded by typical fibromuscular caps consisting of smooth muscle alpha-actin-positive haSMC. Finally, the formation of capillaries by haEC could also be observed within these structures.

-Diagnostic shunt oximetry of atrial septal defect in adulthood-

There are several circumstances in which data obtained at catheterization should alert the cardiologist to look for a shunt that had not been suspected previously. Aim of the study was to explore the most sensitive parameter which is easily practicable and which gives strong evidence for an atrial septal defect (ASD). Moreover, a simplified method for quantifying left-to-right shunts was analyzed. In 84 patients (58 with an atrial septal defect and 26 patients without shunt) a complete oxygen saturation status was determined. The oxymetrically determined relation between pulmonary bloodflow QP and systemic bloodflow QS was 1.31 to 5.60 in patients with ASD and 0.75 to 1.19 in patients without shunt. The analysis of sensitivity and specificity was determined to define the marginal value which gives suspicion of an ASD. The best values for sensitivity and specificity was found for PA O2-SVC O2 = 7.4% (sens. = 98.3%, spec.= 96.2%), PA O2 -IVC O2 = 2.0% (sens./spec.= 100%), PA O2 - MV O2 = 5.0% (sens./spec.= 100%) and PA O2 = 78.4% (sens./spec. = 97.5%). The correlation between the modified ratio QP/QS and various differences in O2-saturation with the shunt size was examined. A high correlation was found for the modified QP/QS with SVC O2 instead of MV O2 (r = 0.98), PA O2-SVC O2 (r = 0.77) and PA O2 - MV O2 (r = 0.74) with QP/QS, respectively.

CONCLUSION

The results demonstrate that an O2-saturation >78% in the pulmonary artery is highly suspicious for the diagnosis of an ASD. With the modified ratio QP/QS = (ART O2-SVC O2)/(PV O2-PA O2) a high sensitive and specific modus of quantifying shunts can be reached. Determination of oxygen saturation from the V. cava interior is therefore not useful.

Occurrence and magnitude of pressure waves during Er:YAG laser ablation of atherosclerotic tissue: comparison to XeCl excimer laser ablation

BACKGROUND AND OBJECTIVE

Since excimer laser ablation has not shown advantages in comparison to conventional balloon angioplasty, the search for other laser light sources came up with the Er:YAG laser, operating at a wavelength of 2.94 microns.

STUDY DESIGN/MATERIALS AND METHODS

Normal and atherosclerotic human vessel segments were irradiated in vitro, using pulsed Er:YAG laser systems. The laser beam was either focused onto the tissue in air or delivered via a fibre system onto the tissue being immersed in saline. Needle-type hydrophones were used for pressure pulse detection.

RESULTS

Er:YAG laser irradiation results in effective tissue ablation of normal and calcified atherosclerotic vessel segments. In comparison to excimer lasers, ablation rates can be increased by a factor of 5 to 10 at least. Er:YAG laser ablation is also associated with a generation of pressure waves. On calcified plaque, the acoustic signals differ significantly from those on normal tissue. Histological tissue analysis reveals small zones of discoloration and tissue fissures that are found 100-200 microns lateral to the crater edge, depending on the energy density used.

CONCLUSION

Er:YAG lasers generate pressure waves that are comparable to excimer laser ablation. Er:YAG lasers, however, show a markedly improved ablation efficiency, which may favour these systems as effectively cutting, less traumatic tools for removal of atherosclerotic plaque.

Low molecular weight heparin in prevention of restenosis after PTCA

Late restenosis occurring after successful PTCA continues to represent a major problem limiting the clinical efficacy of the procedure. It has been shown that smooth muscle cell proliferation plays a major role in this accelerated atherosclerotic process. In vitro and in vivo experiments with the low molecular weight heparin reviparin showed a pronounced inhibitory effect by this compound on smooth muscle cell proliferation. To evaluate the safety of reviparin and the incidence of angiographic restenosis in humans, a study of increasing dosages was conducted in 41 patients. Repeat coronary angiography was performed 3 months after angioplasty. Restenosis occurred in 5 of 37 evaluable patients with initially successful PTCA. No major bleeding complication was documented for any patient in this first pilot trial. A randomized, double-blind, multicentre trial is being carried out to define the real impact of this compound in reducing restenosis in patients who undergo successful balloon angioplasty.

Perforation of a side branch of the right coronary artery during selective coronary angiography using 5 French Judkins catheters

In this case report the first known case of a perforation of a side branch of the right coronary artery during diagnostic coronary angiography using 5 French Judkins catheters is described which occurred by selective intubation. Although catheter placement was controlled by contrast test injection the catheter occasionally intubated the conus artery super selectively just prior to the diagnostic injection. Thus, perforation of small side branches may be encountered especially by the use of 5 French Judkins catheters.

[Fatal outcome of a congenital aneurysm of the right sinus valsalvae ruptured into the right atrium]

In a 24-year-old female patient with sudden collapse an acute tricuspid insufficiency was presumed by echocardiography after the exclusion of pulmonary embolism. Aortography, however, revealed an aneurysm of the right sinus of Valsalva which had ruptured into the right atrium. Despite emergency surgery the patient died in protracted cardiac shock. Biopsy and autopsy showed pathognomonic findings of a congenital aneurysm (medial degeneration, reduction of elastic lamellae). Aneurysms of the sinuses of Valsalva are mainly caused by a rare connatal defect of the aortic wall; the right aortic sinus is involved most frequently, the sudden rupture uncovers the lesion. The characteristics of the reported case are compared with the literature under special consideration of etiology and pathologic anatomy of this unusual entity.

Prolonged proliferative response of smooth muscle cells after experimental intravascular stenting

The purpose of this experimental in vivo study was to determine the time course of smooth muscle cell proliferation early and late after intravascular stenting compared to conventional balloon angioplasty in normal vessels. A balloon expandable 2.0 mm tantalum Strecker stent was placed in the right carotid artery of 33 male New Zealand White rabbits after they had been fed a 0.5% cholesterol diet for 28 days. In addition, balloon angioplasty was performed in 27 of the animals; 19 contralateral vessels served as controls without treatment. The vessels were excised at 7, 14, 28, 42 or 90 days after treatment. During the final 18 h before the rabbits were killed, bromodeoxyuridine (BrdU) was applied and proliferating cells were detected by using a monoclonal antibody against BrdU. In histological cross sections the proportion of cells undergoing DNA synthesis was determined. Analysis was performed separately in the intimal and medial layers. Additionally, the area adjacent to the stent wire was compared with the intermediate area. Smooth muscle cells were identified by alpha-actin staining. Intimal wall thickness increased from 23 +/- 28 microns (control group without intervention) to 323 +/- 84 microns within 42 days after stenting (P < 0.01), and to 81 +/- 82 microns at day 42 after balloon angioplasty (P < 0.05). However, between 42 and 90 days following stent implantation a significant (P < 0.05) decrease in neointimal thickness was observed (90 days: 215 +/- 15 microns).(ABSTRACT TRUNCATED AT 250 WORDS)

Double-blind comparison of the acute effects of two relevant doses of oral nicorandil on central hemodynamics, left ventricular function, and myocardial contractility

Nicorandil is a nicotinamide derivative with potent vasodilator properties. Oral and sublingual administration of this compound in patients with coronary artery disease resulted in a predominant reduction of afterload and a small decrease in left ventricular preload. The effects of nicorandil in different doses on contractile left ventricular (LV) function, however, are not well defined. The aim of the present study was to assess the effects of nicorandil on hemodynamics, left ventricular volume and function, as well as the LV contractility index dP/dt measured by Millar-tip manometers. A total of 16 patients with coronary artery disease were included in this study. After diagnostic coronary angiography and ventriculography, the patients randomly received either 10 or 20 mg of oral nicorandil. The hemodynamic parameters, cardiac output, and LV end-diastolic and systolic pressures were determined after 15, 30, and 60 minutes, and a second angiogram was performed 60 minutes after administration. The predominant effect was a decrease in the mean aortic pressure with a concomitant decrease in the peripheral arterial resistance. Clinically relevant changes in aortic pressure, systemic vascular resistance, and rate-pressure product, however, were documented only after oral administration of 20 mg nicorandil, as opposed to minimal changes in the 10 mg group. LV volume and cardiac output were not changed significantly. LV contractility remained unchanged during the observation period. The hemodynamic profile of this compound is dose-dependent afterload reduction without a change in contractility. Because there was no concomitant increase in heart rate, calculated oxygen consumption was reduced, especially in the higher dose group.

Comparison of valvular resistance, stroke work loss, and Gorlin valve area for quantification of aortic stenosis. An in vitro study in a pulsatile aortic flow model

BACKGROUND

Valvular resistance and stroke work loss have been proposed as alternative measures of stenotic valvular lesions that may be less flow dependent and, thus, superior over valve area calculations for the quantification of aortic stenosis. The present in vitro study was designed to compare the impacts of valvular resistance, stroke work loss, and Gorlin valve area as hemodynamic indexes of aortic stenosis.

METHODS AND RESULTS

In a pulsatile aortic flow model, rigid stenotic orifices in varying sizes (0.5, 1.0, 1.5 and 2.0 cm2) and geometry were studied under different hemodynamic conditions. Ventricular and aortic pressures were measured to determine the mean systolic ventricular pressure (LVSPm) and the transstenotic pressure gradient (delta Pm). Transvalvular flow (Fm) was assessed with an electromagnetic flowmeter. Valvular resistance [VR = 1333.(delta Pm/Fm)] and stroke work loss [SWL = 100.(delta Pm/LVSPm)] were calculated and compared with aortic valve area [AVA = Fm/(50 square root of delta Pm)]. The measurements were performed for a large range of transvalvular flows. At low-flow states, flow augmentation (100-->200 mL/s) increased calculated valvular resistance between 21% (2.0 cm2 orifice) and 66% (0.5-cm2 orifice). Stroke work loss demonstrated an increase from 43% (2.0 cm2) to 100% (1.0 cm2). In contrast, Gorlin valve area revealed only a moderate change from 29% (2.0 cm2) to 5% (0.5 cm2). At physiological flow rates, increase in transvalvular flow (200-->300 mL/s) did not alter calculated Gorlin valve area, whereas valvular resistance and stroke work loss demonstrated a continuing increase. Our experimental results were adopted to interpret the results of three clinical studies in aortic stenosis. The flow-dependent increase of Gorlin valve area, which was found in the cited clinical studies, can be elucidated as true further opening of the stenotic valve but not as a calculation error due to the Gorlin formula.

CONCLUSIONS

Within the physiological range of flow, calculated aortic valve area was less dependent on hemodynamic conditions than were valvular resistance and stroke work loss, which varied as a function of flow. Thus, for the assessment of the severity of aortic stenosis, the Gorlin valve area is superior over valvular resistance and stroke work loss, which must be indexed for flow to adequately quantify the hemodynamic severity of the obstruction.

Intracoronary ultrasound following excimer-laser angioplasty. An in-vitro study in human coronary arteries

To study the ablation effects induced by excimer laser coronary angioplasty (ELCA), we examined 41 segments of nine isolated coronary arteries. An electronic intracoronary ultrasound device (ICUS: 20 MHz, 3.5F, Endosonics) was positioned coaxially within the vessel. Angioplasty was performed using a 1.7 mm ELCA catheter (Spectranetics) which was placed in the lumen and directed vertically onto the intimal surface of the vessel (fluence: 10-50 mJ.mm-2). The laser catheter was removed after each lasing cycle to allow the stepwise evaluation of the morphological effects of ELCA and to avoid reaching the adventitia. Ultrasound images were compared with the corresponding histological specimens. In all cases, the ablation site could be correctly identified by ICUS. No penetration of the adventitia was seen at histology. Ablation depth was 0.31 +/- 0.18 mm as determined by histology and 0.34 +/- 0.18 mm as determined by ultrasound; the diameter of the crater was 0.63 +/- 0.21 mm, and 0.75 +/- 0.16 mm, respectively, and wall thickness was 0.68 +/- 0.18 mm, and 0.83 +/- 0.20 mm, respectively. A statistical relationship between ultrasonic and histology measurements was only found, however, for assessment of wall thickness (r = 0.71).

CONCLUSIONS

The identification of small ablation effects by ICUS was possible with great accuracy and ELCA could be performed without penetration of the adventitial layers. However, exact quantification of the crater dimensions was not possible due to limitations of the axial and lateral resolution. Thus, for the guidance of ELCA by ICUS a further improvement in the resolution capabilities of ICUS devices is mandatory.

Effect of chronic nicotine delivery on the proliferation rate of endothelial and smooth muscle cells in experimentally induced vascular wall plaques

To study the effect of nicotine, cholesterol feeding, and their combination on endothelial and smooth muscle cells in vascular wall plaques an experimental method was established which allows the immunohistochemical detection and quantification of the fractions of endothelial and smooth muscle cells in DNA synthesis under the effect of these stimuli. For this purpose standardized fibromuscular plaques were produced by electrostimulation in the common carotid arteries of rabbits. The animals received either nicotine via implanted osmotic minipumps or a cholesterol diet or both. Plaque size was determined at the end of the experiments after 7 or 14 days as well as the fraction of endothelial and smooth muscle cells in DNA synthesis during exposure to bromodeoxyuridine (BrdU). The BrdU labeling index of endothelial cells clearly increased under chronic nicotine administration for either 7 days or 14 days compared to controls. The combination of nicotine and cholesterol diet led to a more significant increase. In contrast, the BrdU labeling index of smooth muscle cells was not increased under nicotine delivery. The combination of nicotine and cholesterol, however, led to a significant increase of the BrdU labeling index of smooth muscle cells in the plaques compared to cholesterol feeding. Measurement of the plaque size revealed no difference between controls and nicotine-treated animals after 14 days of nicotine delivery, whereas the combination of cholesterol and nicotine produced increased plaque formation compared to a group of animals which received a cholesterol diet alone.