John T. Fallon

Macrophage infiltration in acute coronary syndromes. Implications for plaque rupture.

BackgroundRupture of atherosclerotic plaques is probably the most important mechanism underlying the sudden onset of acute coronary syndromes. Macrophages may release lytic enzymes that degrade the fibrous cap and therefore produce rupture of the atherosclerotic plaque. This study was designed to quantify macrophage content in coronary plaque tissue from patients with stable and unstable coronary syndromes. Methods and ResultsHematoxylin and eosin and immuno-staining with anti-human macrophage monoclonal antibody (PG-M1) were performed. Computerized planimetry was used to analyze 26 atherectomy specimens comprising 524 pieces of tissue from 8 patients with chronic stable angina, 8 patients with unstable angina, and 10 patients with non-Q-wave myo-cardial infarction. Total plaque area was 417±87 mm2× 10−2 in patients with stable angina, 601±157 mm2×10−2 in patients with unstable angina, and 499±87 mm2× 10−2in patients with non-Q-wave myocardial infarction (P=NS). The macrophage-rich area was larger in plaques from patients with unstable angina (61±18 mm2x 102) and non-Q-wave myocardial infarction (87±32 mm2× 10−2) than in plaques from patients with stable angina (14±5 mm2×10−2) (P=.024). The percentage of the total plaque area occupied by macrophages was also larger in patients with unstable angina (13.3 ±5.6%) and non-Q-wave myocardial infarction (14.6±4.6%) than in patients with stable angina (3.14±1%) (P=.018). Macrophagerich sclerotic tissue was largest in patients with non-Q-wave myocardial infarction (67±30 mm2× 1010−2) and unstable angina (55±19 mm2× 10−2) than in patients with stable angina (11.5±4.1 mm2× 10−2) (P=.046). Macrophage-rich atheromatous gruel was also larg-est in patients with non-Q-wave myocardial infarction (15±4 mm2×10−2) than in patients with unstable angina (3.3±1.7 mm2×10−2) or stable angina (2.4±1.2 mm2× 10−2) (P=.026). ConclusionsMacrophage-rich areas are more frequently found in patients with unstable angina and non-Q-wave myocardial infarction. This suggests that macrophages are a marker of unstable atherosclerotic plaques and may play a significant role in the pathophysiology of acute coronary syndromes.

Tissue Factor Modulates the Thrombogenicity of Human Atherosclerotic Plaques

BACKGROUND The thrombogenicity of a disrupted atherosclerotic lesion is dependent on the nature and extent of the plaque components exposed to flowing blood together with local rheology and a variety of systemic factors. We previously reported on the different thrombogenicity of the various types of human atherosclerotic lesions when exposed to flowing blood in a well-characterized perfusion system. This study examines the role of tissue factor in the thrombogenicity of different types of atherosclerotic plaques and their components. METHODS AND RESULTS Fifty human arterial segments (5 foam cell-rich, 9 collagen-rich, and 10 lipid-rich atherosclerotic lesions and 26 normal, nonatherosclerotic segments) were exposed to heparinized blood at high shear rate conditions in the Badimon perfusion chamber. The thrombogenicity of the arterial specimens was assessed by 111In-labeled platelets. After perfusion, specimens were stained for tissue factor by use of an in situ binding assay for factor VIIa. Tissue factor in specimens was semiquantitatively assessed on a scale of 0 to 3. Platelet deposition on the lipid-rich atheromatous core was significantly higher than on all other substrates (P = .0002). The lipid-rich core also exhibited the most intense tissue factor staining (3 +/- 0.1 arbitrary units) compared with other arterial components. Comparison of all specimens showed a positive correlation between quantitative platelet deposition and tissue factor staining score (r = .35, P < .01). CONCLUSIONS Our results show that tissue factor is present in lipid-rich human atherosclerotic plaques and suggest that it is an important determinant of the thrombogenicity of human atherosclerotic lesions after spontaneous or mechanical plaque disruption.

Noninvasive In Vivo Human Coronary Artery Lumen and Wall Imaging Using Black-Blood Magnetic Resonance Imaging

BACKGROUND High-resolution MRI has the potential to noninvasively image the human coronary artery wall and define the degree and nature of coronary artery disease. Coronary artery imaging by MR has been limited by artifacts related to blood flow and motion and by low spatial resolution. METHODS AND RESULTS We used a noninvasive black-blood (BB) MRI (BB-MR) method, free of motion and blood-flow artifacts, for high-resolution (down to 0.46 mm in-plane resolution and 3-mm slice thickness) imaging of the coronary artery lumen and wall. In vivo BB-MR of both normal and atherosclerotic human coronary arteries was performed in 13 subjects: 8 normal subjects and 5 patients with coronary artery disease. The average coronary wall thickness for each cross-sectional image was 0.75+/-0.17 mm (range, 0.55 to 1.0 mm) in the normal subjects. MR images of coronary arteries in patients with >/=40% stenosis as assessed by x-ray angiography showed localized wall thickness of 4.38+/-0.71 mm (range, 3.30 to 5.73 mm). The difference in maximum wall thickness between the normal subjects and patients was statistically significant (P<0.0001). CONCLUSIONS In vivo high-spatial-resolution BB-MR provides a unique new method to noninvasively image and assess the morphological features of human coronary arteries. This may allow the identification of atherosclerotic disease before it is symptomatic. Further studies are necessary to identify the different plaque components and to assess lesions in asymptomatic patients and their outcomes.

Inhibition of Intimal Thickening After Balloon Angioplasty in Porcine Coronary Arteries by Targeting Regulators of the Cell Cycle

BACKGROUND Although percutaneous transluminal coronary angioplasty (PTCA) is a highly effective procedure to reduce the severity of stenotic coronary atherosclerotic disease, its long-term success is significantly limited by the high rate of restenosis. Several cellular and molecular mechanisms have been implicated in the development of restenosis post-PTCA, including vascular smooth muscle cell (VSMC) activation, migration, and proliferation. Recently, our group demonstrated that rapamycin, an immunosuppressant agent with antiproliferative properties, inhibits both rat and human VSMC proliferation and migration in vitro. In the present study, we investigated (1) whether rapamycin administration could reduce neointimal thickening in a porcine model of restenosis post-PTCA and (2) the mechanism by which rapamycin inhibits VSMCs in vivo. METHODS AND RESULTS PTCA was performed on a porcine model at a balloon/vessel ratio of 1.7+/-0.2. Coronary arteries were analyzed for neointimal formation 4 weeks after PTCA. Intramuscular administration of rapamycin started 3 days before PTCA at a dose of 0.5 mg/kg and continued for 14 days at a dose of 0.25 mg/kg. Cyclin-dependent kinase inhibitor (CDKI) p27(kip1) protein levels and pRb phosphorylation within the vessel wall were determined by immunoblot analysis. PTCA in the control group was associated with the development of significant luminal stenosis 4 weeks after the coronary intervention. Luminal narrowing was a consequence of significant neointimal formation in the injured areas. Rapamycin administration was associated with a significant inhibition in coronary stenosis (63+/-3.4% versus 36+/-4.5%; P<0.001), resulting in a concomitant increase in luminal area (1.74+/-0.1 mm2 versus 3. 3+/-0.4 mm2; P<0.001) after PTCA. Inhibition of proliferation was associated with markedly increased concentrations of the p27(kip1) levels and inhibition of pRb phosphorylation within the vessel wall. CONCLUSIONS Rapamycin administration significantly reduced the arterial proliferative response after PTCA in the pig by increasing the level of the CDKI p27(kip1) and inhibition of the pRb phosphorylation within the vessel wall. Therefore, pharmacological interventions that elevate CDKI in the vessel wall and target cyclin-dependent kinase activity may have a therapeutic role in the treatment of restenosis after angioplasty in humans.

Active myocarditis in the spectrum of acute dilated cardiomyopathies: clinical features, histologic correlates, and clinical outcome

We studied the clinical features and course (average follow-up time, 18 months) of 27 patients with acute dilated cardiomyopathy (symptoms for less than 6 months) who were referred for endomyocardial biopsy. Almost 40 per cent of the patients subsequently had a rise in left ventricular ejection fraction (on average, from 0.21 to 0.41) and substantial improvement in heart failure; the remainder died or had chronic dilated cardiomyopathy. Biopsy revealed myocarditis in 18 patients, and this finding was especially common (89 per cent) in patients who had been ill for less than four weeks. But the biopsy specimen was negative in four patients whose clinical features and later course were diagnostic of myocarditis. Nine patients received immunosuppressive drugs, and four improved--a rate that did not differ from the rate of spontaneous improvement. Neither the histologic features of the biopsy specimen nor the clinical features at presentation were clearly correlated with subsequent improvement, whether or not immunosuppressive drugs were given. We conclude that many cases of unexplained dilated cardiomyopathy result from myocarditis. Definitive histologic confirmation depends on the duration of illness. The efficacy of immunosuppressive treatment must still be established.

Morphology after Transluminal Angioplasty in Human Beings

PERCUTANEOUS transluminal angioplasty is frequently used in selected patients to decrease stenoses in atherosclerotic peripheral arteries,1 , 2 renal arteries,3 4 5 6 and coronary arteries.7 8 9 Th...

Evaluation of a QRS scoring system for estimating myocardial infarct size

This study correlated the location and size of posterolateral myocardial infarcts (MIs) measured anatomically with that estimated by quantitative criteria derived from the standard 12-lead ECG. Twenty patients were studied who had autopsy-proved, single, posterolateral MIs and no confounding factors of ventricular hypertrophy or bundle branch block in their ECG. Left ventricular anatomic MI size ranged from 1 to 46%. No patient had a greater than or equal to 0.04-second Q wave in any electrocardiographic lead and only 55% had a 0.03-second Q wave. A 29-point, simplified QRS scoring system consisting of 37 weighted criteria was applied to the ECG. Points were scored by the ECG in 85% of the patients (range 1 to 8 points). MI was indicated by a wide variety of QRS criteria; 19 of the 37 criteria from 8 different electrocardiographic leads were met. The correlation coefficient between MI size measured anatomically and that estimated by the QRS score was 0.72. Each point represented approximately 4% MI of the left ventricular wall.

Coronary Composition and Macrophage Infiltration in Atherectomy Specimens From Patients With Diabetes Mellitus

BackgroundLipid-rich, inflamed atherosclerotic lesions are associated with plaque rupture and thrombosis, which are the most important causes of death in patients with diabetes mellitus. This study was designed to quantify lipid composition and macrophage infiltration in the coronary lesions of patients with diabetes mellitus. Methods and ResultsA total of 47 coronary atherectomy specimens from patients with diabetes mellitus were examined and compared with 48 atherectomy specimens from patients without diabetes. Plaque composition was characterized by trichrome staining. Macrophage infiltration was characterized by immunostaining. Clinical and demographic data were similar in both groups. The percentage of total area occupied by lipid-rich atheroma was larger in specimens from patients with diabetes (7±2%) than in specimens from patients without diabetes (2±1%;P =0.01), and the percentage of total area occupied by macrophages was larger in specimens from patients with diabetes (22±3%) than in specimens from patients without diabetes (12±1%;P =0.003). The incidence of thrombus was also higher in specimens from patients with diabetes than in specimens from patients without diabetes (62% versus 40%;P =0.04). Plaque composition, macrophage infiltration, and thrombus were similar in lesions from diabetic patients treated with insulin compared with lesions from patients treated with sulfonylureas or diet. ConclusionsCoronary tissue from patients with diabetes exhibits a larger content of lipid-rich atheroma, macrophage infiltration, and subsequent thrombosis than tissue from patients without diabetes. These differences suggest an increased vulnerability for coronary thrombosis in patients with diabetes mellitus.

A Phase 1/2 Clinical Trial of Enzyme Replacement in Fabry Disease: Pharmacokinetic, Substrate Clearance, and Safety Studies

Fabry disease results from deficient alpha-galactosidase A (alpha-Gal A) activity and the pathologic accumulation of the globotriaosylceramide (GL-3) and related glycosphingolipids, primarily in vascular endothelial lysosomes. Treatment is currently palliative, and affected patients generally die in their 40s or 50s. Preclinical studies of recombinant human alpha-Gal A (r-halphaGalA) infusions in knockout mice demonstrated reduction of GL-3 in tissues and plasma, providing rationale for a phase 1/2 clinical trial. Here, we report a single-center, open-label, dose-ranging study of r-halphaGalA treatment in 15 patients, each of whom received five infusions at one of five dose regimens. Intravenously administered r-halphaGalA was cleared from the circulation in a dose-dependent manner, via both saturable and non-saturable pathways. Rapid and marked reductions in plasma and tissue GL-3 were observed biochemically, histologically, and/or ultrastructurally. Clearance of plasma GL-3 was dose-dependent. In patients with pre- and posttreatment biopsies, mean GL-3 content decreased 84% in liver (n=13), was markedly reduced in kidney in four of five patients, and after five doses was modestly lowered in the endomyocardium of four of seven patients. GL-3 deposits were cleared to near normal or were markedly reduced in the vascular endothelium of liver, skin, heart, and kidney, on the basis of light- and electron-microscopic evaluation. In addition, patients reported less pain, increased ability to sweat, and improved quality-of-life measures. Infusions were well tolerated; four patients experienced mild-to-moderate reactions, suggestive of hypersensitivity, that were managed conservatively. Of 15 patients, 8 (53%) developed IgG antibodies to r-halphaGalA; however, the antibodies were not neutralizing, as indicated by unchanged pharmacokinetic values for infusions 1 and 5. This study provides the basis for a phase 3 trial of enzyme-replacement therapy for Fabry disease.

Macrophages, Smooth Muscle Cells, and Tissue Factor in Unstable Angina Implications for Cell-Mediated Thrombogenicity in Acute Coronary Syndromes

Background Macrophage expression of tissue factor may be responsible for coronary thrombogenicity in patients with plaque rupture. In patients without plaque rupture, smooth muscle cells may be the thrombogenic substrate. This study was designed to identify the cellular correlations of tissue factor in patients with unstable angina. Methods and Results Tissue from 50 coronary specimens (1560 pieces) from patients with unstable angina and 15 specimens from patients with stable angina were analyzed. Total and segmental areas (in square millimeters) were identified with trichrome staining. Macrophages, smooth muscle cells, and tissue factor were identified by immunostaining. Tissue factor content was larger in unstable angina (42±3%) than in stable angina (18±4%) ( P =.0001). Macrophage content was also larger in unstable angina (16±2%) than in stable angina (5±2%) ( P =.002). The percentage of tissue factor located in cellular areas was larger in coronary samples from patients with unstable angina (67±8%) than in samples from patients with stable angina (40±5%) ( P =.00007). Multiple linear stepwise regression analysis showed that coronary tissue factor content correlated significantly ( r =.83, P r =.98, P Conclusions Tissue factor content is increased in unstable angina and correlates with areas of macrophages and smooth muscle cells, suggesting a cell-mediated thrombogenicity in patients with acute coronary syndromes.