[Design optimization of endovascular stent by finite element method]

Stent implantation is now the favorable therapy of coronary heart disease, but the restenosis occurring in association with the currently used stents device has become the main obstacle limiting the further development of stent. To change the expanding behavior of endovascular stents by way of design optimization is considered one of the effective approaches for reducing the damage to the intima of blood vessel and thereby decreasing the in-stent restenosis. So in this paper, the finite element method was used to systematically simulate and analyze the influences of different width of ring supporter and the non-symmetrical design of stent on its transitorily expanding behavior. The results show that among the structure parameters, the width of ring supporter of stent influences its expanded pressure remarkably. When designing the endovascular stent, we make its ring supporter unsymmetrical, i. e., we make the width of ring supporter of stent change degressively from its central part to end part. By this means, the dogboning, which normally happens in the expanding process of the balloon/stent system, can be effectively controlled and the acute vascular injuries can be reduced.

Olmesartan, But Not Amlodipine, Improves Endothelium-Dependent Coronary Dilation in Hypertensive Patients

OBJECTIVES

We aimed to compare the effects of the angiotensin II receptor blocker (ARB) olmesartan versus the calcium channel blocker (CCB) amlodipine on coronary endothelial dysfunction in patients with hypertension.

BACKGROUND

Angiotensin II receptor blockers are thought to have greater beneficial effects than CCBs on coronary vasomotion by directly blocking action of angiotensin II.

METHODS

Twenty-six patients with untreated essential hypertension were prospectively assigned to treatment with either olmesartan (27.7 +/- 12.4 mg/day, n = 13) or amlodipine (5.6 +/- 1.5 mg/day, n = 13) for 12 weeks. Changes of corrected myocardial blood flow (DeltaMBF) and coronary vascular resistance (DeltaCVR) from rest to cold pressor were measured by using 15O-water and positron emission tomography before and after treatment. Blood biomarkers including lipids, glucose, insulin, high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-alpha, and superoxide dismutase (SOD) were also measured.

RESULTS

Olmesartan and amlodipine reduced blood pressure (BP) to the same extent (-28.7 +/- 16.2 mm Hg vs. -26.7 +/- 10.8 mm Hg). In the olmesartan group, DeltaMBF tended to be greater (-0.15 +/- 0.19 ml/g/min vs. 0.03 +/- 0.17 ml/g/min, p = 0.09 by 2-way analysis of variance), and DeltaCVR was significantly decreased (7.9 +/- 23.5 mm Hg/[ml/g/min] vs. -16.6 +/- 18.0 mm Hg/[ml/g/min], p < 0.05) after treatment, whereas these parameters did not change in the amlodipine group (DeltaMBF: -0.15 +/- 0.12 ml/g/min vs. -0.12 +/- 0.20 ml/g/min; DeltaCVR: 6.5 +/- 18.2 mm Hg/[ml/g/min] vs. 4.8 +/- 23.4 mm Hg/[ml/g/min]). Serum SOD activity tended to increase (4.74 +/- 4.77 U/ml vs. 5.57 +/- 4.74 U/ml, p = 0.07 by 2-way analysis of variance) only in the olmesartan group.

CONCLUSIONS

Olmesartan, but not amlodipine, improved endothelium-dependent coronary dilation in hypertensive patients independent of BP reduction. These beneficial effects on coronary vasomotion might be via an antioxidant property of ARBs.

A tale of two stents: perioperative management of patients with drug-eluting coronary stents

Drug-eluting stents were introduced into clinical practice to decrease coronary stent restenosis rates. Though remarkably effective in reducing this complication, recent data reveal that drug-eluting stents pose a significant risk for late stent thrombosis, an event strongly correlated with discontinuation of anti-platelet therapy. Because anti-platelet agents are often discontinued perioperatively, patients with DES are at risk for perioperative stent thrombosis and myocardial infarction. Along with a review of the recent literature, we present two cases of patients with drug-eluting stents scheduled for renal transplantation. Two distinct antithrombotic management strategies illustrate the risk of either approach-bleeding and transfusion versus stent thrombosis and myocardial infarction.

Effect of statin treatment on aortic valve and coronary artery calcification

BACKGROUND AND AIM OF THE STUDY

Conflicting data exist regarding statins and the progression of aortic valve disease. Hence, further information is required to determine if statin treatment has a beneficial effect on aortic valve calcification, and whether the inflammatory status of the patient affects aortic valve disease progression. The study aim was to evaluate the concomitant effect of statin treatment on aortic valve and coronary artery calcification and to compare results with the inflammatory status of the patient.

METHODS

Sixty-one patients with moderate to severe aortic stenosis (AS) were enrolled in this single-center, prospective observational study evaluating progression of aortic valve calcification. Patients underwent baseline and one-year echocardiography and electron-beam computed tomography. Blood samples were withdrawn at baseline and at one year for measurement of inflammatory biomarkers.

RESULTS

There was no significant reduction in calcium accumulation in the aortic valve of the statin group compared to the non-statin group, but there was trend towards less progression of calcification for the statin group. A significant inhibition of the coronary artery calcification volume score was observed for the statin group compared to the non-statin group. On echocardiography, statin treatment had no significant impact on aortic valve stenosis. Patients with serum LDL level >130 mg/dl showed less progression of coronary artery calcification when treated with statin drugs. The level of high-sensitivity C-reactive protein (hsCRP) significantly correlated with the progression of calcification for both the aortic valve and coronary arteries.

CONCLUSION

Whilst there was no significant benefit of statin treatment on aortic valve calcification over one year, there was a decreased progression of coronary artery calcification. The baseline level of hsCRP was predictive of progression of both aortic valve and coronary artery calcification, and may identify a high-risk population requiring aggressive control, either with statins or emerging drugs targeted at the inflammatory process of atherosclerosis.

Pharmacogenomics of Renin Angiotensin System Inhibitors in Coronary Artery Disease

Renin Angiotensin System (RAS) inhibitors comprise some of the most commonly used medications in coronary artery disease (CAD) and its related syndromes. Unfortunately, significant inter-patient variability seems likely in response to these agents; of which, the influence of genetic determinants is of interest. This review summarizes the available RAS inhibitor pharmacogenomic studies which have evaluated RAS polymorphisms that either elucidate mechanism via surrogate endpoint measurements, or predict efficacy via clinical outcomes in CAD related syndromes.Regardless of the endpoint, none of the RAS genotypes conclusively predicts efficacy of RAS inhibitors. In fact, the results of the pharmacogenomic studies were often in direct conflict with one another. Varied results appear due to methodological limitations (e.g., inadequate study power, genotyping error, methods of endpoint measurement), study conceptualization (e.g., overestimating the contribution of polymorphism to disease, lack of haplotype approach), and differences between studies (e.g., genotype frequency, study subject characteristics, the specific medication and dose used). Thus investigators should consider the various methodological limitations to improve upon the current approach to RAS inhibitor pharmacogenomic research in the vast CAD population.

Prolonged intravenous eptifibatide infusion for prevention of coronary stent thrombosis

Coronary bare-metal stent thrombosis usually occurs within a week of angioplasty, and may result in myocardial infarction and death. Thrombosis is effectively prevented by antiplatelet therapy with aspirin and clopidogrel. We describe a patient who was unable to ingest oral medication after angioplasty due to gastrointestinal surgery, and was therefore at risk for stent thrombosis. Intravenous eptifibatide was infused for 8 days in order to achieve parenteral platelet inhibition. We suggest a role for long-term intravenous administration of glycoprotein IIb/IIIa inhibitors for prevention of stent thrombosis in patients unable to take oral antiplatelet therapy.

[Long-term clinical efficiency of endovascular treatment using Cypher rapamycin-eluting stents in patients with coronary heart disease]

The study was undertaken to analyze the long-term results in patients with coronary heart disease (CHD) one year or more after Cypher stent implantation. It covered 1221 patients. One-, two-, and three- vessel lesions were observed in 693 (56.8%), 344 (28.2%), and 184 (15%) patients, respectively. A total of 1967 Cypher stents were implanted. The results of treatment were analyzed 1 and 2 years after intervention. The efficiency of a procedure was evaluated by the following parameters: the presence or absence of anginal symptoms, the presence and absence of complications (fatal outcome, myocardial infarction). The following morphological parameters: the rate of restenosis and that of late stent thrombosis were also assessed. The results of one- and two-year follow-ups were used to make a multivariate analysis of the clinical and morphological predictors of coronary complications (fatal outcome, myocardial infarction, recurrent angina pectoris) in the late period, as well as the predictors of restenosis and late stent thrombosis. Restenosis following 1 year of Cypher stent implantation is 3.1%. The factors that significantly increase the risk of this complication within the first year are diabetes mellitus and revascularization in the patients operated on. The one-year rate of Cypher stent thromboses is 1.6%. Patients' discontinuation of antiaggregant therapy is the sole factor that significantly increases the rate of their late thromboses in this period. Within the second year of a follow-up, the rate of late Cypher stent thromboses is 1.8%. The risk of this complication is significantly increased by factors, such as a lengthy (more than 3 mm) stented portion, renal failure, and less than 40% left ventricular ejection fraction.

The clinical trial of Women On the Move through Activity and Nutrition (WOMAN) study

The Women On the Move through Activity and Nutrition (WOMAN) study is the first randomized clinical trial of nonpharmacological intervention designed to modify lipoproteins, weight loss and exercise among postmenopausal women using noninvasive measures of atherosclerosis as the primary endpoint. The trial was initially designed to test whether intervention as compared to health education would be more effective in slowing progression of subclinical atherosclerosis among women on hormone therapy (HT), estrogen or estrogen+progestin. It was designed and implemented prior to the results of the Women's Health Initiative (WHI). The trial was since modified to include women who had been on HT but went off after the results of the WHI were reported. Eligible women were between the ages of 52-62, had waist circumference>or=80 cm, low density lipoprotein cholesterol between 100-160 mg% and controlled blood pressure. The intervention is low in total and saturated fat, trans fats, higher in fiber and promotes loss of 7-10% of body weight and includes at least 150 min of physical activity per week. The study has recruited 508 women. The primary endpoints are change in extent of carotid intima-media wall thickness as measured by carotid ultrasound, pulse wave velocity as a measure of vascular stiffness and coronary artery calcium using electron beam computed tomography. Body composition is measured by dual-energy X-ray absorptiometry.

P-wave duration and dispersion in patients with coronary slow flow and its relationship with Thrombolysis in Myocardial Infarction frame count

AIM

P-wave dispersion (PD), and duration has been reported to be associated with inhomogeneous and discontinuous propagation of sinus impulses. The aim of this study was to investigate the PD in patients with coronary slow flow (CSF) phenomenon.

METHODS

Study population included 48 patients with angiographically proven normal coronary arteries and slow coronary flow in all 3 coronary vessels (group I, 36 men; mean age, 54 +/- 9 years) and 32 subjects with angiographically proven normal coronary arteries without associated slow coronary flow (group II, 24 men, mean age, 53 +/- 10 years). Coronary flow rates of all patients and control subjects were documented by Thrombolysis In Myocardial Infarction (TIMI) frame count. All patients in group I had TIMI frame counts greater than 2 SD above those of control subjects (group II). The mean TIMI frame count for each patient and control subject was calculated by adding the TIMI frame counts for each major epicardial coronary artery and then dividing the obtained value into 3. The maximum and minimum P-wave duration (P(max) and P(min)) and PD were measured from the 12-lead surface electrocardiogram. Echocardiographic examination was also performed.

RESULTS

There was no statistically significant difference between the 2 groups with respect to age, sex, hypertension, diabetes mellitus, hyperlipidemia, and cigarette smoking (P > .05). P-wave dispersion and P(max) of patients with CSF were found to be significantly higher than those of control subjects (39.4 +/- 17 vs 21.2 +/- 10 milliseconds and 121.6 +/- 17.1 vs 104.3 +/- 10.4 milliseconds, respectively; P < .0001). Moreover, we found a significant positive correlation between both P(max) and PD with mean TIMI frame count (r = 0.836 and r = 0.806, respectively; P < .0001).

CONCLUSIONS

P-wave dispersion and P-wave duration both were found to be greater in patients with CSF than in controls.

Duale antiaggregatorische Therapie nach Implantation von Koronarstents

Dual antiplatelet-aggregation treatment with aspirin and clopidogrel after coronary stent implantation is nowadays standard peri-interventional practice, although its use is not yet licensed for this indication in many European countries. Clopidogrel administration is initiated before PCI with a loading dose of 300 mg when given at least 6 hours before PCI, otherwise 600 mg. The required duration of combined (aspirin + clopidogrel) antiplatelet-aggregation treatment after coronary stent implantation depends on the type of stent and the pre-existing disease. After bare-metal stent implantation dual antiplatelet medication is needed for at least 3-4 weeks, after drug-eluting stent implantation 6 months, after coronary brachytherapy 12 months, and 9 months after an acute coronary syndrome. These time intervals should also be respected before any elective surgical intervention. Early operations, because postponement is impossible, should be performed under antiplatelet-aggregation treatment after assessment of bleeding risk in the individual case. Premature termination of this treatment carries an increased risk of serious cardiovascular events, especially stent thrombosis and myocardial infarction. Prolonged antiplatelet-aggregation treatment is of benefit especially in patients with a high risk of serious cardiovascular events. Patients with an indication for long-term anticoagulation may require, during the period of highest risk of stent thrombosis after stent implantation, administration of combined aspirin, clopidogrel and anticoagulants with an INR target value in the lower therapeutic range. The increased risk of bleeding must be weighed up against the potential benefit.

Five-year results of a randomized, single-center study of tacrolimus vs microemulsion cyclosporine in heart transplant patients

BACKGROUND

Previous multicenter, randomized trials, lacking standardized post-transplant protocols, have compared tacrolimus (Tac) and cyclosporine (CyA, Sandimmune) and demonstrated similar outcomes with some different adverse effects. The microemulsion form of CyA (mCyA, Neoral) has replaced Sandimmune CyA as the more widely utilized CyA formulation. This is the first 5-year follow-up study of a large, single-center trial (n = 67) under a standardized post-transplant protocol comparing Tac and mCyA.

METHODS

Sixty-seven heart transplant patients were randomized to Tac (n = 33) or mCyA (n = 34), both in combination with corticosteroids and azathioprine without cytolytic induction. Five-year end-points included survival, Grade > or = 3A or treated rejection, angiographic cardiac allograft vasculopathy (CAV; any lesion > or = 30% stenosis), renal dysfunction (creatinine > or = 2.0 mg/dl), use of two or more anti-hypertensive medications, percent diabetic and lipid levels.

RESULTS

Five-year survival, freedom from Grade > or = 3A or any treated rejection and angiographic CAV, mean cholesterol level and percent diabetic were similar between the two groups. The Tac group had a significantly lower 5-year mean triglyceride level (Tac 97 +/- 34 vs mCyA 175 +/- 103 mg/dl, p = 0.011) and average serum creatinine level (Tac 1.2 +/- 0.5 mg/dl vs mCyA 1.5 +/- 0.4 mg/dl, p = 0.044). There was a trend toward fewer patients requiring two or more anti-hypertensive drugs in the Tac group (Tac 33% vs mCyA 59%, p = 0.065).

CONCLUSIONS

Tac and mCyA appear to be comparable with regard to 5-year survival, freedom from rejection and CAV. However, compared with mCyA, Tac appears to reduce the adverse effect profile for hypertriglyceridemia and renal dysfunction and the need for hypertensive medications.

Finite element analysis and stent design: Reduction of dogboning

In Western countries, cardiovascular disease is the most common cause of death, often related to atherosclerosis. This paper offers a brief introduction into some aspects of this disease and its treatment, where the use of stents is gaining increasing importance. Stents are supporting - mostly metal - tubular mesh structures which are opened in an obstructed artery in order to reopen it, and to offer radial strength to prevent elastic recoil of the dilated vessel. In addition to a variety of experimental tests to study the behavior of (new) stent designs, advanced numerical models (e.g. Finite Element Models) may offer interesting insights in the mechanical behavior of stents and will undoubtedly influence the design of future generation stents. A brief literature review on numerical studies dealing with the mechanical behavior of stents is presented. Subsequently, the finite element method is exploited to investigate and compare different designs of a "first generation" Palmaz Schatz stent in order to reduce the dogboning (i.e. ends of stent open first during expansion) to a minimum. Our computational models (Abaqus ) are described in terms of geometry, constitutive material models, numerical aspects and output quantities. Altering the original symmetric stent design to asymmetric designs decreased the dogboning from 27.24% to less than 10% for the vast majority of the studied asymmetric designs. For one particular configuration, the dogboning effect vanished completely. For this reason, taking asymmetry into account in the design of stents seems very promising, at least from the perspective of dogboning. However, as the dogboning only takes into account the radii (R) at the central and distal part of the stent, nothing can be concluded concerning the uniformity of the complete stent expansion. The mean value (Rm) and the root mean square (R(RMS)) of radii (differences) of the stent at the end of the loading phase (P = 0.7 N/mm2) are much better parameters to give a clear indication of the uniformity of the expanded stent's shape. Although the model is suitable to study basic aspects of stent deployment, further research is necessary, especially accounting for newer generation stent geometries and more realistic balloon-stent interaction.

Meta-analysis of MTHFR 677C->T polymorphism and coronary heart disease: does totality of evidence support causal role for homocysteine and preventive potential of folate?

OBJECTIVES

To investigate the association between the MTHFR 677C-->T polymorphism and coronary heart disease, assessing small study bias and heterogeneity between studies.

DATA SOURCES

Medline and Embase citation searches between January 2001 and August 2004; no language restrictions.

STUDY SELECTION

Case-control and prospective studies of association between MTHFR 677C-->T variant and myocardial infarction, coronary artery occlusion, or both; 80 studies were included.

DATA EXTRACTION

Data on genotype frequency and mean homocysteine concentrations by genotype were extracted. Odds ratios were calculated for TT genotype versus CC genotype. Heterogeneity was explored, with stratification by geographical region of the study samples, and meta-regression by difference in mean serum homocysteine concentrations (CC minus TT genotypes) was carried out.

RESULTS

26,000 cases and 31,183 controls were included. An overall random effects odds ratio of 1.14 (95% confidence intervals 1.05 to 1.24) was found for TT versus CC genotype. There was strong evidence of heterogeneity (P < 0.001, I2 = 38.4%), which largely disappeared after stratification by geographical region. Odds ratios in Europe, Australia, and North America attenuated towards the null, unlike those in the Middle East and Asia.

CONCLUSIONS

No strong evidence exists to support an association of the MTHFR 677 C-->T polymorphism and coronary heart disease in Europe, North America, or Australia. Geographical variability may be due to higher folate intake in North America and Europe or to publication bias. The conclusion drawn from previous meta-analyses that folic acid, through lowering homocysteine, has a role in prevention of cardiovascular disease is in some doubt.

Non-invasive evaluation of coronary calcium

With the increasing diffusion of 4-row,16-row and 64-row multislice computed tomography scanners, widespread coronary calcium scoring has become possible in Europe. This relatively easy-to-perform test has a high sensitivity and low specificity for the detection of significant coronary artery stenosis, and may have an important role in the risk stratification for future coronary artery events in selected groups of patients, such as those immediately at risk. This study reviews the techniques available for coronary calcium scoring (electron beam tomography and multislice computed tomography) with their respective protocols, as well as their advantages and disadvantages. The methods for interpreting the results, the potential indications and the clinical applications of the techniques are also described.

Exercise training increases basal tone in arterioles distal to chronic coronary occlusion

Endurance exercise training increases basal active tone in coronary arteries and enhances myogenic tone in coronary arterioles of control animals. Paradoxically, exercise training has also been shown to augment nitric oxide production and nitric oxide-mediated relaxation in coronary arterioles. The purpose of the present study was to examine the effect of exercise training on basal active tone of arterioles (approximately 150 microm ID) isolated from the collateral-dependent region of hearts exposed to chronic coronary occlusion. Ameroid occluders were surgically placed around the proximal left circumflex coronary artery of miniature swine. Arterioles were isolated from both the collateral-dependent and nonoccluded myocardial regions of sedentary (pen confined) and exercise-trained (treadmill run; 14 wk) pigs. Coronary tone was studied in isolated arterioles using microvessel myographs and standard isometric techniques. Exposure to nominally Ca2+-free external solution reduced resting tension in all arterioles; decreases were most profound (P < 0.05) in arterioles from the collateral-dependent region of exercise-trained animals. Furthermore, nitric oxide synthase (NOS) inhibition (N(omega)-nitro-L-arginine methyl ester; 100 microM) unmasked markedly increased nitric oxide-sensitive tone in arterioles from the collateral-dependent region of exercise-trained swine. Blockade of K+ channels revealed significantly enhanced K+ channel contribution to basal tone in collateral-dependent arterioles of exercise-trained pigs. Protein content of endothelial NOS (eNOS) and phosphorylated eNOS (pS1179), determined by immunoblot, was elevated in arterioles from exercise-trained animals with the greatest effect in collateral-dependent vasculature. Taken together, we demonstrate the interaction of opposing exercise training-enhanced arteriolar basal active tone, nitric oxide production, and K+ channel activity in chronic coronary occlusion, potentially enhancing the capacity to regulate blood flow to collateral-dependent myocardium.

Peroxisome proliferator-activated receptor gamma; Its role in atherosclerosis and restenosis

Cellular proliferation and migration are fundamental processes that contribute to the injury response in major blood vessels. The resultant pathologies are atherosclerosis and restenosis. As we begin to understand the cellular changes associated with vascular injury, it is critical to determine whether the inhibition of growth and movement of cells in the vasculature could serve as a novel therapeutic strategy to prevent atherosclerosis and restenosis.

Long-Term Changes in Coronary Artery Aneurysms in Patients With Kawasaki Disease-Comparison of Therapeutic Regimens-

BACKGROUND

There are few studies of the therapeutic regimens for the prevention of stenotic transformation of aneurysms in Kawasaki disease (KD). The aim of this study was to assess the prophylactic effect of combined therapy in the acute stage and convalescent- to chronic-stage against the formation of stenotic lesions.

METHODS AND RESULTS

In 85 patients, 103 giant aneurysms (ANl), 46 medium-sized aneurysms (ANm), and 13 small aneurysms (ANs) were analyzed. With respect to therapy in the acute stage, no localized stenosis of ANl in the left coronary artery was noted in patients who received high-dose gamma globulin therapy (G). For ANm, the group (G) showed a significantly higher regression rate than the aspirin group and steroids group. Furthermore, no coronary artery occlusion/recanalization of ANl occurred with the prophylactic regimen of aspirin and warfarin {aw}. Prophylaxis {aw} and the prophylactic regimen of aspirin alone {a} significantly lowered the incidence compared with either the prophylactic regimen of warfarin {w} or no prophylaxis {n}. However, no significant differences were noted between prophylaxis {w} and {n}.

CONCLUSIONS

High-dose gamma globulin therapy in the acute stage of KD is the first choice for the prevention of stenotic transformation. Prophylaxis {aw} is recommended for ANl.