David W.M. Muller

A pilot study of ex vivo gene therapy for homozygous familial hypercholesterolaemia

The outcome of the first pilot study of liver-directed gene therapy is reported here. Five patients with homozygous familial hypercholesterolaemia (FH) ranging in age from 7 to 41 years were enrolled; each patient tolerated the procedure well without significant complications. Transgene expression was detected in a limited number of hepatocytes of liver tissue harvested four months after gene transfer from all five patients. Significant and prolonged reductions in low density lipoprotein (LDL) cholesterol were demonstrated in three of five patients; in vivo LDL catabolism was increased 53% following gene therapy in a receptor negative patient, who realized a reduction in serum LDL equal to ∼150 mg dl−1. This study demonstrates the feasibility of engrafting limited numbers of retrovirus-transduced hepatocytes without morbidity and achieving persistent gene expression lasting at least four months after gene therapy. The variable metabolic responses observed following low-level genetic reconstitution in the five patients studied precludes a broader application of liver-directed gene therapy without modifications that consistently effect substantially greater gene transfer.

Sirolimus in De Novo Heart Transplant Recipients Reduces Acute Rejection and Prevents Coronary Artery Disease at 2 Years A Randomized Clinical Trial

Background—Sirolimus reduces acute rejection in renal transplant recipients and prevents vasculopathy in nonhuman primates and in-stent restenosis in humans. Its effects on rejection and transplant vasculopathy in human heart transplant recipients are unknown. Methods and Results—In a randomized, open-label study, sirolimus was compared with azathioprine in combination with cyclosporine and steroids administered from the time of cardiac transplantation. We report 6-month rejection rates (primary end point), 12-month safety and efficacy data, and 6- and 24-month graft vasculopathy data in 136 cardiac allograft recipients randomly assigned (2:1) to sirolimus (n=92) or azathioprine (n=44). At 6 months, the proportion of patients with grade 3a or greater acute rejection was 32.4% for sirolimus 3 mg/d (P=0.027), 32.8% for sirolimus 5 mg/d (P=0.013), and 56.8% for azathioprine. Patient survival at 12 months was comparable among groups. Intracoronary ultrasound at 6 weeks, 6 months, and 2 years demonstrated highly significant progression of transplant vasculopathy in azathioprine-treated patients. At 6 months, a highly significant absence of progression in intimal plus medial proliferation and significant protection against luminal encroachment was evident in sirolimus-treated patients, and these effects were sustained at 2 years. Conclusions—Sirolimus use from the time of transplantation approximately halved the number of patients experiencing acute rejection. The measurable development of transplant vasculopathy at 6 months and 2 years in patients receiving azathioprine was not observed in patients receiving sirolimus.

Experimental models of coronary artery restenosis

The study of potentially effective drug therapies and mechanical devices for the prevention of restenosis after percutaneous coronary revascularization has relied heavily on the use of experimental animal models. To date, greater than 50 experimental studies have been reported and have suggested that at least nine different classes of pharmacologic agents inhibit the intimal proliferative response to arterial injury. However, no pharmacologic intervention has yet been shown to reproducibly reduce the incidence of restenosis after coronary balloon angioplasty in humans. To identify the reasons for the apparent nonspecificity of the animal models and to determine which model should most reliably predict the efficacy of individual therapies in humans, the distinguishing characteristics of the experimental models were compared. Particular attention was paid to the size and morphologic structure of the treated artery, the susceptibility of the species to spontaneous and diet-induced arterial disease, the nature of the stimulus to intimal proliferation and several practical and logistic considerations. Finally, the reported efficacies of specific drug therapies in the respective animal models and in humans were compared. This review suggests that significant interspecies and occasionally intraspecies differences do exist among the respective animal models, particularly in the extent and composition of the neointimal thickening.(ABSTRACT TRUNCATED AT 250 WORDS)

IL-8 Is an Angiogenic Factor in Human Coronary Atherectomy Tissue

BACKGROUND Interleukin-8 (IL-8), a CXC chemokine that induces the migration and proliferation of endothelial cells and smooth muscle cells, is a potent angiogenic factor that may play a role in atherosclerosis. Previously, IL-8 has been reported in atherosclerotic lesions and circulating macrophages from patients with atherosclerosis. Therefore, we sought to determine whether IL-8 plays a role in mediating angiogenic activity in atherosclerosis. METHODS AND RESULTS Homogenates from 16 patients undergoing directional coronary atherectomy (DCA) and control samples from the internal mammary artery (IMA) of 7 patients undergoing bypass graft surgery were assessed for IL-8 content by specific ELISA, immunohistochemistry, and in situ hybridization for IL-8 mRNA. The contribution of IL-8 to net angiogenic activity was assessed using the rat cornea micropocket assay and cultured cells. IL-8 expression was significantly elevated in DCA samples compared with IMA samples (1.71+/-0.6 versus 0.05+/-0.03 ng/mg of total protein; P<0.01). Positive immunolocalization of IL-8 was found exclusively in DCA tissue sections, and it correlated with the presence of factor VIII-related antigen. In situ reverse transcriptase polymerase chain reaction revealed the expression of IL-8 mRNA in DCA tissue. Corneal neovascular response, defined by ingrowth of capillary sprouts toward the implant, was markedly positive with DCA pellets, but no constitutive vessel ingrowth was seen with IMA specimens. Neutralizing IL-8 attenuated both the in vivo corneal neovascular response and the in vitro proliferation of cultured cells. CONCLUSIONS The results suggest that, in human coronary atherosclerosis, IL-8 is an important mediator of angiogenesis and may contribute to plaque formation via its angiogenic properties.

Thrombosis of a flexible coil coronary stent: frequency, predictors and clinical outcome.

OBJECTIVES The aim of this study was to evaluate the predictors and clinical sequelae of stent thrombosis. BACKGROUND Although coronary artery stenting is being increasingly applied, the major unique complication of stent thrombosis is not well characterized. METHODS We studied 145 patients who underwent coronary artery stenting with the Gianturco-Roubin flexible coil design for abrupt vessel closure or to prevent restenosis. There were 17 stented vessel closures (11.7%), 7 as a result of acute (< 24 h) and 10 of subacute (days 1 to 21) thrombosis. RESULTS In seven patients successful coronary recanalization was achieved with thrombolytic agents and balloon angioplasty. Creatine kinase was significantly elevated in 13 patients, with a Q wave myocardial infarction in 11 and emergency coronary artery bypass grafting in 8. Comparisons (multivariate analysis) with a control cohort (n = 33) of patients without thrombosis matched for age, gender and vessel stented revealed lesion eccentricity (p = 0.003), unstable angina (p = 0.048) and indication for stent implantation (abrupt closure versus restenosis) (p = 0.002), as predictors of thrombotic occlusion of stented vessels. Subtherapeutic anticoagulation (activated partial thromboplastin time < 2 times control value, prothrombin time < 1.4 control value) occurred at least once during the hospital stay in all 10 patients with subacute thrombosis and in 20 of 33 control patients (p = 0.047). In 2 patients with subacute thrombosis and 11 control subjects, subtherapeutic anticoagulation was necessitated by bleeding. CONCLUSIONS Early thrombosis after coronary stenting was relatively common (> 10%), occurring predominantly in eccentric lesions and in patients with unstable angina pectoris. This complication is associated with significant adverse clinical outcomes and may be reduced by more intensive anticoagulation yet, in a delicate balance, can be precipitated by inadequate heparin therapy.

Selection of Patients with Acute Myocardial Infarction for Thrombolytic Therapy

PURPOSE To critically review the current recommendations regarding the eligibility of patients with myocardial infarction for thrombolytic therapy. DATA IDENTIFICATION Relevant studies published from January 1980 to January 1990 were identified through a computerized search of the English-language literature using MEDLINE and by a manual search of the bibliographies of all identified articles. STUDY SELECTION All randomized, controlled trials of intravenous thrombolysis in acute myocardial infarction and unstable angina were reviewed. Smaller, observational studies and previous review articles were included when relevant to the discussion. DATA EXTRACTION Key data were extracted from each article, including the proportions of patients eligible for thrombolysis, the reasons for exclusion from thrombolytic therapy, and the clinical outcomes of patients treated and of those excluded from treatment. The validity of certain exclusion criteria was examined using subgroup analysis from the large, randomized mortality trials of intravenous thrombolysis and observations from smaller, nonrandomized studies. RESULTS OF DATA SYNTHESIS To date, relatively few patients with myocardial infarction have been considered eligible for fibrinolytic therapy. In this group, both early and late mortality have been significantly reduced. Patients excluded from thrombolysis, however, continue to have a high early mortality. The data suggest that the potential benefits of this treatment might be extended to selected high-risk subgroups. In particular, the risk-benefit ratio may favor the inclusion of otherwise healthy elderly patients; certain patients presenting more than 6 hours after the onset of symptoms; and patients with a history of controlled systolic hypertension or brief, nontraumatic cardiopulmonary resuscitation. The data do not support the use of fibrinolytic therapy as primary treatment in patients with unstable angina or suspected myocardial infarction in the absence of confirmatory electrocardiographic changes. CONCLUSIONS The full potential of thrombolytic therapy to alter the natural history of acute myocardial infarction can only be realized through the continued evaluation of selection criteria and the identification and treatment of the greatest possible number of eligible patients.

Multivessel coronary artery disease: A key predictor of short-term prognosis after reperfusion therapy for acute myocardial infarction

Results of recent studies have suggested that routine cardiac catheterization may be unnecessary after reperfusion therapy for acute myocardial infarction. Therefore to better define the short-term prognostic value of early coronary angiography, and specifically the prognostic significance of multivessel coronary artery disease, the angiographic findings of 855 patients consecutively enrolled in five phases of the TAMI study were correlated with their in-hospital outcome. All patients received intravenous thrombolytic therapy (tissue plasminogen activator, urokinase, or both agents) and underwent cardiac catheterization within 90 minutes of the initiation of therapy. Multivessel disease, defined as the presence of greater than or equal to 75% luminal diameter stenosis in two or more major epicardial arteries, was documented in 236 patients. When compared with the group of patients without multivessel disease, this group had a higher prevalence of coronary risk factors and more frequently had a history of antecedent ischemic chest pain. Although the severity of the infarct zone dysfunction was similar in the two groups (-2.77 +/- 1.00 vs -2.50 +/- 1.09 SD/chord, p = NS), global left ventricular ejection fraction was lower in the group with multivessel disease (48.6 +/- 12.4% vs 51.8 +/- 10.6%, p less than 0.01). This was associated with a significant difference in the function of the noninfarct zone. Whereas this region was hyperkinetic in the group with minimal or single-vessel disease, it was hypocontractile or dyskinetic in those with multivessel disease (+0.66 +/- 1.53 vs -0.52 +/- 1.73 SD/chord, p = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Strategies for Treating Arterial Restenosis Using Polymeric Controlled Release Implants

Coronary artery obstruction is currently being treated with a number of invasive approaches involving catheter based angioplasty procedures. These have included most recently balloon angioplasty combined with expansion of obstructed coronary arteries using balloon expandable stainless steel stents. However, angioplasty itself, especially with stenting, leads to an accelerated reobstruction process, known as restenosis. Research reported in this paper has investigated an approach to preventing restenosis using controlled release drug-polymer implants for local inhibition of the pathophysiologic events of restenosis. Model therapeutic compounds were chosen including aspirin, as an antiplatelet agent, hirulog, as an antithrombin, and colchicine as an antiproliferative. Controlled release polymer matrices were successfully formulated and characterized. Retention of anticoagulant activity for the peptide, hirulog, was demonstrated in vitro. These polymers are suitable for investigations in periadventitial implants and animal models of restenosis. Eventually, controlled release strategies for preventing restenosis will involve integrating of ideal agents including gene therapy, with stents and related devices in order to develop a drug delivery systems approach.

Quantitative Doppler tissue imaging for assessment of regional myocardial velocities during transient ischemia and reperfusion

Doppler tissue imaging (DTI) is a new noninvasive imaging modality that directly interrogates myocardial velocity with high temporal and spatial resolution. This study was designed to test the hypothesis that quantitative DTI provides unique information regarding regional myocardial systolic and diastolic function during acute ischemic events. Myocardial velocities were quantified during the acute ischemic and reperfusion phases of 13 elective percutaneous coronary angioplasty procedures in 12 patients. In myocardium subtended by angioplasty vessels, peak velocities decreased during occlusive balloon inflation (from 21.2 +/- 9.8 to -0.6 +/- 4.0 mm/sec in systole [p < 0.001] and from 21.7 +/- 9.2 to -0.6 +/- 3.9 mm/sec in diastole [p < 0.001]). During early reperfusion, velocities exceeded those observed at baseline (p = 0.003). In regions remote from the treated artery, peak myocardial velocities increased in the absence of significant stenosis but remained unchanged or decreased in the presence of significant stenosis of the associated vessel. We conclude that (1) myocardial velocities rapidly decrease during acute ischemia and show a rebound increase after reperfusion, and (2) in regions remote from ischemia, velocities display distinct patterns on the basis of the presence or absence of obstructive coronary disease in the associated vessel. Quantitative DTI is a useful tool for the assessment of myocardial velocity and may provide new insights into myocardial systolic and diastolic function.

Noninvasive quantification of regional myocardial flow reserve in patients with coronary atherosclerosis using nitrogen-13 ammonia positron emission tomography. Determination of extent of altered vascular reactivity.

OBJECTIVES The aim of this study was to evaluate patients with coronary artery disease to 1) determine the relation between flow reserve measured by nitrogen-13 (N-13) ammonia kinetic modeling and stenosis severity assessed by quantitative angiography, and 2) examine whether flow reserve is impaired in regions supplied by vessels without significant angiographic disease. BACKGROUND With the advent of new therapeutic approaches for coronary disease, an accurate noninvasive approach for absolute quantification of flow and flow reserve is needed to evaluate functional severity and extent of atherosclerosis. Nitrogen-13 ammonia kinetic modeling may permit such evaluation. METHODS Twenty-seven subjects were classified into three groups: group 1 = 5 young volunteers: group 2 = 7 middle-aged volunteers; and group 3 = 15 patients with coronary artery disease. Dynamic N-13 ammonia positron emission tomographic imaging was performed at rest and during adenosine infusion. A three-compartment model was fit to regional N-13 ammonia kinetic data to determine myocardial flow. Group 3 patients underwent quantitative coronary angiography. RESULTS The regional blood flow results in patients with coronary disease were classified into four subgroups: no significant detectable disease and mild (50% to 69.9% area stenosis), moderate (70% to 94.9% area stenosis) or severe (95% to 100% area stenosis) coronary disease. Flow reserve was 2.95 +/- 0.65; 2.09 +/- 0.47; 2.02 +/- 0.51; 1.3 +/- 0.32, respectively (p < or = 0.01 except mild vs. moderate). Flow reserve was correlated with percent area stenosis (r = -0.56) and minimal lumen diameter (r = 0.75). In volunteers (groups 1 and 2), flow reserves were greater than in segments without detectable disease in group 3 patients (4.10 +/- 0.71 and 3.79 +/- 0.42, respectively, vs. 2.88 +/- 0.56, p < or = 0.02). CONCLUSIONS The functional severity of coronary disease measured by N-13 ammonia positron emission tomography varied for a given stenosis but was significantly related to angiographic severity. Among patients with coronary disease, myocardial regions without significant angiographic stenoses displayed reduced flow reserve than did regions in control subjects, indicating that vascular reactivity was more diffusely impaired in group 3 than was suggested by angiography. Noninvasive quantification of myocardial flow reserve using dynamic N-13 ammonia positron emission tomography yields important functional data that permit definition of the extent of disease even when disease is not apparent by angiography.