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To determine the impact of Healing Touch on vital signs, adult intensive care unit patients were recruited from multiple hospital sites. Both pain and agitation improved and there was a significant change in hemodynamics that reflected a calming effect. Healing Touch may be considered a respected addition to symptom management. [ABSTRACT FROM AUTHOR]

Abstract: Sodium-glucose cotransporter 2 inhibitors (SGLT2-i) are a novel class of oral hypoglycemic agents currently used among patients with type 2 diabetes mellitus (T2DM). The effects of SGLT2-i inhibitors on cardiac structure and function are not fully understood. The aim of this study is to evaluate the echocardiographic changing among patients with well-controlled T2DM treated with SGLT2-i in real-world setting. Thirty-five well-controlled T2DM patients (65 ± 9 years, 43.7% male) with preserved left ventricular ejection fraction (LVEF) and 35 age and sex-matched controls were included. T2DM patients underwent clinical and laboratory evaluation; 12-lead surface electrocardiogram; 2-dimensional color Doppler echocardiography at enrolment, before SGLT2-i administration, and at 6 months follow-up after an uninterrupted 10 mg once daily of empagliflozin (n: 21) or dapagliflozin (n: 14). Standard echocardiographic measurements, LV global longitudinal strain (LV-GLS), global wasted work, and global work efficiency were calculated. T2DM patients showed higher E\E' ratio (8.3 ± 2.5 vs. 6.3 ± 0.9; P < 0.0001 ) and lower LV-GLS (15.8 ± 8.1 vs. 22.1 ± 1.4%; P < 0.0001 ) and global myocardial work efficiency (91 ± 4 vs. 94 ± 3%; P: 0.0007 ) compared with age and sex-matched controls. At 6-month follow-up, T2DM patients showed a significant increase in LVEF (58.9 ± 3.2 vs. 62 ± 3.2; P < 0.0001 ), LV-GLS (16.2 ± 2.8 vs. 18.7 ± 2.4%; P = 0.003 ), and global work efficiency (90.3 ± 3.5 vs. 93.3 ± 3.2%; P = 0.0004 ) values; conversely, global wasted work values (161.2 ± 33.6 vs. 112.72 ± 37.3 mm Hg%; P < 0.0001 ) significantly decreased. Well-controlled T2DM patients with preserved LVEF who are treated with a SGLT2-i on top of the guidelines direct medical therapy showed a favorable cardiac remodeling, characterized by the improvement of LV-GLS and myocardial work efficiency., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Dual pathway inhibition (DPI) with low-dose rivaroxaban and aspirin in patients with coronary artery disease (CAD) and/or peripheral artery disease (PAD) reduces the occurrence of cardiovascular (CV) events; however, the underlying mechanisms explaining these latter CV benefits are not clearly understood. Our explorative observational study aimed to evaluate the effect of dual pathway inhibition on plasma inflammation and coagulation markers among real-world patients with CAD and/or PAD. We prospectively included all consecutive patients with an established diagnosis of CAD and/or PAD treated with aspirin 100 mg once daily (OD) and rivaroxaban 2.5 mg twice daily (TD). Clinical evaluation and laboratory analyses, including hemoglobin, renal function (creatinine, urea, and cystatin-C), coagulation markers (INR and aPTT), inflammation markers (IL-6, CRP, lipoprotein-associated phospholipase A2, and copeptin), and growth differentiation factor-15 (GDF-15), were conducted at baseline, before starting treatment, and at 4 and 24 weeks after study drug administration. Fifty-four consecutive patients (mean age 66 ± 7 years; male 83%) who completed the 6-month follow-up were included. At 24-week follow-up, a statistically significant reduction in IL-6 serum levels [4.6 (3.5-6.5) vs. 3.4 (2.4-4.3) pg/mL ; P = 0.0001] and fibrinogen [336 (290-390) vs. 310 (275-364) mg/dL; P = 0.04] was shown; moreover, a significant increase in GDF-15 serum level [1309 (974-1961) vs. 1538 (1286-2913) pg/mL; P = 0.002] was observed. Hemoglobin, renal function, and cardiovascular homeostasis biomarkers remain stable over the time. The anti-Xa activity at both [0.005 (0-0.02) vs. 0.2 (0.1-0.34); P < 0.0001) significantly increased. The dual pathway inhibitions with low-dose rivaroxaban and aspirin in patients with CAD and/or PAD were associated with the reduction of inflammation biomarkers., Competing Interests: The authors report no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Aims: In heart failure (HF), prognostic risk scores focus on all-cause mortality prediction. However, in advanced HF (AdHF) ambulatory patients awaiting heart transplantation (HTx), hospitalizations for acutely decompensated/worsening HF are relevant to clinical decision-making, but unpredicted by common risk functions., Methods: Among consecutive ambulatory patients added to the waitlist for HTx, event discriminators within 2 years from recruitment were assessed prospectively by area under the curve from receiver-operating characteristic curves, and by Cox proportional hazards models. Primary composite end points included the first between all-cause mortality and acutely decompensated/worsening HF requiring hospitalization and specific treatments., Results: In 89 patients, 36 primary composite events were recorded in a 2-year follow-up (40% of the study sample), and associated with nonischemic etiology and nonsinus rhythm, with lower systolic blood pressure (BP), lower plasma sodium and hemoglobin concentrations, and with higher N-terminal pro-brain natriuretic peptide (NT-proBNP), larger left ventricular (LV) dimensions and lower LV ejection fraction, greater proportion of significant mitral regurgitation, lower tricuspid annulus peak systolic excursion (TAPSE), lower percentage of predicted distance at 6-minute walking test (%p6MWT) and lower global symptoms burden by the Kansas City Cardiomyopathy Questionnaire, lower peak oxygen uptake by cardiopulmonary exercise, and higher wedge pressure by right heart catheterization, as compared with those with no events (P < 0.05). Only Metabolic Exercise Cardiac Kidney Index (MECKI) at recruitment was higher with patients reporting events, which predicted composite end points in addition to and independently of NT-proBNP, and lower systolic BP (all P < 0.05). In an alternative risk model, severe mitral regurgitation and lower TAPSE replaced MECKI and BP but not NT-proBNP (all P < 0.01)., Conclusion: Higher NT-pro-BNP, lower systolic BP and higher MECKI may contribute to predicting all-cause death and acutely decompensated/worsening HF among ambulatory patients awaiting HTx, with lower TAPSE and severe mitral regurgitation representing further alternative independent prognosticators., (Copyright © 2022 Italian Federation of Cardiology - I.F.C. All rights reserved.)

Abstract: No data on the add-on sacubitril/valsartan (S/V) therapy among cardiac resynchronization therapy with a defibrillator (CRT-D) nonresponder patients are currently available in literature. We conducted a prospective observational study including 190 CRT-D nonresponder patients with symptomatic heart failure with reduced ejection fraction despite the optimal medical therapy from at least 1 year. The primary endpoint was the rate of additional responders (left ventricular end-systolic volume reduction >15%) at 12 months from the introduction of S/V therapy. At the end of the 12 months follow-up, 37 patients (19.5%) were deemed as "additional responders" to the combination use of CRT + S/V therapy. The only clinical predictor of additional response was a lower left ventricular ejection fraction [OR 0.881 (0.815-0.953), P = 0.002] at baseline. At 12 months follow-up, there were significant improvements in heart failure (HF) symptoms and functional status [New York Heart Association 2 (2-3) vs. 1 (1-2), P < 0.001; physical activity duration/day: 10 (8-12) vs. 13 (10-18) hours, P < 0.001]. Compared with the 12 months preceding S/V introduction, there were significant reductions in the rate of HF rehospitalization (35.5% vs. 19.5%, P < 0.001), in atrial tachycardia/atrial fibrillation burden [6.0 (5.0-8.0) % vs. 0 (0-2.0) %, P < 0.001] and in the proportions of patients experiencing ventricular arrhythmias (21.6% vs. 6.3%; P < 0.001). Our results indicate that S/V add-on therapy in CRT-D nonresponder patients is associated with 19.5% of additional responders, a reduction in HF symptoms and rehospitalizations, AF burden, and ventricular arrhythmias., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Non-invasive cardiovascular imaging owns a pivotal role in the preoperative assessment of patients for transcatheter aortic valve implantation (TAVI), providing a wide range of crucial information to select the patients who will benefit the most and have the procedure done safely. Although advanced cardiac imaging with cardiac computed tomography is routinely used for a detailed anatomic assessment before TAVI, echocardiography remains the first imaging modality to assess aortic stenosis severity and to provide essential functional information. This document results from the collaboration between the Italian Society of Cardiology (SIC) and the Italian Society of Medical and Interventional Radiology (SIRM), aiming to produce an updated consensus statement about the pre-procedural imaging assessment in patient for TAVI. The writing committee is composed of radiologists and cardiologists, experts in the field of cardiac imaging and structural heart diseases. Part 1 of the document, after a brief overview of the clinical indication and basic technical aspects of TAVI, will focus on the role of echocardiography in TAVI pre-procedural planning., (Copyright © 2022 Italian Federation of Cardiology - I.F.C. All rights reserved.)

Abstract: Many antitumoral drugs have been linked to takotsubo cardiomyopathy, with no clear pathogenetic mechanisms. Data about this condition are lacking in literature. The aim of this meta-summary is to summarize the characteristics of patients with antitumoral drug-induced takotsubo cardiomyopathy, described in case reports available in literature. We searched for published case reports in PubMed, Google Scholar, EMBASE, and Scopus from 2009 about stress cardiomyopathy and antiblastic drugs. We selected 41 case reports. All cases underwent chemotherapy/immunotherapy for different types of cancer. The median age was 58 years, and 61% of them were women. The most common comorbidities were hypertension (12.2%) and dyslipidemia (4.9%), but most of the population had no cardiological clinical history. Takotsubo cardiomyopathy is associated to the 5-fluorouracil (36.5%), capecitabine (9.7%), trastuzumab (9.7%), and immune check point inhibitor (9.7%) treatment. The median time of onset was 2 days (1-150). Cardiogenic shock was the first manifestation in 11 patients (26.8%). Left ventricle ejection fraction recovery was showed in 33 patients (89%) with mean ejection fraction 57.7 ± 7%, after a median of 30-day (4-300) follow-up. Patients with cancer experienced takotsubo cardiomyopathy within few days from the beginning of therapy, and the most of them normalized the heart function in few weeks. Cardiogenic shock showed high prevalence in this setting of patients. Larger studies are needed to better understand the pathological mechanisms of antiblastic drug-induced stress cardiomyopathy, to find risk factors associated and preventive strategies for limit this type of cardiotoxicities., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Coronavirus disease 2019 (COVID-19) outbreak is a public health emergency of international concerns because of a highly pathogenic human coronavirus (HCoV), actually named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite much emerging data about the epidemiological association between cardiovascular diseases and COVID-19, little is still known about atrial fibrillation and its optimal management in this clinical contest. The aim of our review is to describe the pharmacological interactions between cardiovascular drugs more commonly used in atrial fibrillation management and experimental COVID-19 therapies, based on EU and US summaries of product characteristics.

Direct oral anticoagulants (DOACs) are considered a first-line therapy for long-term stroke prevention in patients with nonvalvular atrial fibrillation (AF) and high thromboembolic risk. The potential role of DOACs in cardiac interventional procedures is a pressing clinical question, considering the increasing number of procedures and the growing prevalence of patients in DOAC therapy. The aim of this review is to provide an update on available evidence about the clinical performance of DOACs in AF patients undergoing different interventional procedures (AF cardioversion and ablation, and percutaneous coronary and structural heart disease interventions) and to explore the possible role of DOACs as an alternative therapeutic strategy in cardiac interventional procedures among non-AF patients.

Atrial fibrillation is the most common arrhythmia in clinical practice, and age is one of the strongest predictors/risk factors for ischemic stroke in patients with atrial fibrillation. Elderly patients, in particular patients aged 80 years and older, are at higher risk of both ischemic and bleeding events compared with younger patients. Vitamin K antagonists (VKAs) reduce the risk of ischemic stroke, especially in the elderly, but increase the bleeding risk. In addition, frequent international normalized ratio monitoring is needed to ensure the optimal level of anticoagulation. Furthermore, VKAs have multiple drug and food interactions. Direct oral anticoagulants (DOACs) have recently emerged as alternatives to VKAs and are gradually increasing their popularity mainly because of their fewer drug and food interactions and ease of use. Their effectiveness and safety have been well-established in the general population, but the benefit in the very elderly (≥80 years old) is still unclear. Data about the safety and the effectiveness of DOACs in patients older than 75 years are available in literature, but the evidences of the use of DOACs in patients aged 80 years and older are lacking. This review aims to give light to the differences, in terms of benefits and safety, of the DOACs in this subset of patients.

: The introduction of percutaneous treatment of severe aortic stenosis with transcatheter aortic valve implantation (TAVI) remains one of the greatest achievements of interventional cardiology. In fact, TAVI emerged as a better option than either medical therapy or balloon aortic valvuloplasty for patients who cannot undergo surgical aortic valve replacement (SAVR) or are at high surgical risk. Recently, increased operator experience and improved device systems have led to a worldwide trend toward the extension of TAVI to low-risk or intermediate-risk patients. In this expert opinion paper, we first discuss the basic pathophysiology of aortic stenosis in different settings then the key results of recent clinical investigations on TAVI in intermediate-risk aortic stenosis patients are summarized. Particular emphasis is placed on the results of the nordic aortic valve intervention, placement of aortic transcatheter valves (PARTNER) 2 and Surgical Replacement and Transcatheter Aortic Valve Implantation Randomized trials. The PARTNER 2 was the first large randomized trial that evaluated the outcome of TAVI in patients at intermediate risk. The PARTNER 2 data demonstrated that TAVI is a feasible and reasonable alternative to surgery in intermediate-risk patients (Society of Thoracic Surgeons 4-8%), especially if they are elderly or frail. There was a significant interaction between TAVI approach and mortality, with transfemoral TAVI showing superiority over SAVR. Moreover, we examine the complementary results of the recently concluded Surgical Replacement and Transcatheter Aortic Valve Implantation trial. This prospective randomized trial demonstrated that TAVI is comparable with surgery (primary end point 12.6% in the TAVI group vs. 14.0% in the SAVR group) in severe aortic stenosis patients deemed to be at intermediate risk. We review the most relevant clinical evidence deriving from nonrandomized studies and meta-analyses. Altogether, clinical outcome available data suggest that TAVI with a newer generation device might be the preferred treatment option in this patient subgroup. Finally, the differences between the latest European and American Guidelines on TAVI were reported and discussed. The conclusion of this expert opinion article is that TAVI, if feasible, is the treatment of choice in patients with prohibitive or high surgical risk and may lead to similar or lower early and midterm mortality rates compared with SAVR in intermediate-risk patients with severe aortic stenosis.

The options for antithrombotic therapy have recently been expanded, facilitating optimal tailored treatment. Dual antiplatelet therapy with aspirin and an approved adenosine diphosphate P2Y12 receptor antagonist is recommended for the management of patients with acute coronary syndromes (ACS). However, there are a number of controversies: which P2Y12 inhibitor to choose; how long should antiplatelet therapy be used so as to prevent thrombotic events and minimize bleeding risks; whether to use drug-eluting (DES) or bare-metal stents (BMS) and how to manage the individual variability in response to clopidogrel. Clopidogrel in combination with aspirin has been the standard dual antiplatelet regimen for ACS. The new, more potent P2Y12 inhibitors, prasugrel and ticagrelor, have shown improved antithrombotic effects compared with clopidogrel in patients with ACS (with or without ST-segment elevation myocardial infarction) in landmark trials, even if they were associated with an increased risk of major bleeding. Different pharmacogenetic and pharmacodynamic characteristics may explain, in part, the different pharmacologic and clinical responses to these antiplatelet agents. Importantly, both clopidogrel and prasugrel are prodrugs, i.e., they need to be converted in vivo into active metabolites that selectively and irreversibly bind the P2Y12 receptor. Unlike clopidogrel, however, common functional cytochrome P450 genetic variants do not affect prasugrel active metabolite levels or inhibition of platelet aggregation. In contrast, ticagrelor is not a prodrug (i.e., does not require hepatic metabolism to exert its antiplatelet effect) and represents the first oral P2Y12 receptor antagonist that is reversibly bound. Similar to prasugrel, ticagrelor achieves greater and more rapid inhibition of platelet function than clopidogrel. Evidence suggests that the new P2Y12 antagonists may offer improved antithrombotic effects compared with clopidogrel in selected patients for the optimal management of ACS in clinical practice.

With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they have been shown increasingly to affect several aspects of the pathogenesis of obesity-related diseases. Until relatively recently, the role of adipose tissue itself in the development of obesity and its consequences was considered to be a passive one. It is now clear that, in addition to storing energy in the form of triglycerides, adipocytes also secrete a large variety of proteins, including cytokines, chemokines and hormone-like factors. This production of proatherogenic chemokines by adipose tissue is of particular interest, since their local secretion, for example by perivascular adipose depots, may provide a novel mechanistic link between obesity and associated vascular complications.

Background: Tissue factor (TF) is the main initiator of coagulation in vivo. Recently, however, a role for TF as a cell receptor involved in signal transduction has been suggested. The aim of the present study was to assess whether activated factor VII (FVIIa) binding to TF could induce smooth muscle cell (SMC) proliferation and to clarify the possible intracellular mechanism(s) responsible for this proliferation., Methods and Results: Cell proliferation was induced by FVIIa in a dose-dependent manner, as assessed by [3H]thymidine incorporation and direct cell counting, whereas no response was observed with active site-inhibited FVIIa (FVIIai), which is identical to FVIIa but is devoid of enzymatic activity. Similarly, no proliferation was observed when binding of FVIIa to TF was prevented by the monoclonal anti-TF antibody AP-1. Activation of the p44/42 mitogen-activated protein (MAP) kinase (extracellular signal-regulated kinases 1 and 2 [ERK 1/2]) pathway on binding of FVIIa to TF was demonstrated by transient ERK phosphorylation in Western blots and by suppression of proliferation with the specific MEK (MAP kinase/ERK kinase) inhibitor UO126. ERK phosphorylation was not observed with FVIIai or when cells were pretreated with AP-1., Conclusions: These data indicate a specific effect by which binding of FVIIa to TF on the surface of SMCs induces proliferation via a coagulation-independent mechanism and possibly indicate a new link between coagulation, inflammation, and atherosclerosis.

Background: Tissue factor pathway inhibitor (TFPI) is the endogenous inhibitor of the extrinsic coagulation pathway; however, its involvement during thrombus formation in patients with acute coronary syndromes (ACS) is still unknown., Methods and Results: Transcardiac (aorta/coronary sinus) free and total TFPI (free + lipoprotein-bound form) levels, as well as TFPI/factor Xa (FXa) complex levels, were measured in plasma samples obtained from patients with acute myocardial infarction undergoing primary PTCA and patients with unstable angina undergoing urgent PTCA. Patients with stable angina undergoing elective PTCA served as controls. In addition, prothrombin fragment 1+2 and fibrinopeptide A plasma levels were measured. Samples were collected at baseline, after PTCA, and after stent deployment. In patients with ACS, both total and free TFPI plasma levels in the coronary sinus were significantly lower than the corresponding levels measured in the aorta at any time point of the study; conversely, a significant increase in TFPI/FXa complex plasma levels was observed in the coronary sinus as compared with the aorta. In contrast, in patients with stable angina, no differences were observed in TFPI and TFPI/FXa levels at baseline in the coronary sinus as compared with the aorta., Conclusions: TFPI is involved in the process of thrombus formation in vivo in patients with ACS, which suggests a potential role for TFPI in modulating coronary thrombosis.

Objective: Tissue factor (TF) is normally expressed at low levels in the media of blood vessels, but it is readily induced after vessel injury. It is not known whether vascular damage per se or thrombus formation is responsible for this phenomenon., Methods and Results: Cyclic flow variations (CFVs), attributable to recurrent thrombus formation, were induced in stenotic rabbit carotid arteries with endothelial injury. CFVs were observed for 30 minutes and 2, 4, and 8 hours in different groups of animals. Another group of rabbits pretreated with hirudin before inducing arterial damage to inhibit thrombus formation was observed for 8 hours. Arterial sections were immunostained for TF. Undamaged arteries served as controls. In additional rabbits, in situ hybridization experiments were performed. No TF expression was observed in the media of control vessels, whereas a progressive increase in TF mRNA and protein expression was observed in carotid arteries as CFVs progressed. No increase in TF expression was observed in animals pretreated with hirudin. In vitro experiments demonstrated that TF mRNA is induced in smooth muscle cells stimulated with activated platelets as well as with some platelet-derived mediators., Conclusions: This phenomenon may contribute to sustain intravascular thrombus formation after the initial thrombogenic stimulus.

Background: Tissue factor pathway inhibitor (TFPI) is the sole known inhibitor of the extrinsic coagulation pathway of physiological importance; however, its role in modulating thrombosis in vivo is still unclear., Methods and Results: Intravascular thrombosis was initiated by placing an external constrictor around endothelially injured rabbit carotid arteries (n=10). Carotid blood flow velocity was measured by a Doppler flow probe. After placement of the constrictor, cyclic flow reductions (CFRs), due to recurrent thrombosis, developed at the site of stenosis. Transstenotic TFPI plasma activity was measured in blood samples before induction of CFRs and after 30, 60, and 180 minutes of CFRs. TFPI plasma activity distal to the site of thrombosis was significantly lower than the corresponding proximal values at 30, 60, and 180 minutes of CFRs. In addition, a progressive decrease in TFPI plasma activity was observed in both the proximal and the distal samples, indicating consumption of TFPI during thrombus formation. In 10 additional rabbits, CFRs were abolished by administration of aspirin (10 mg/kg). In the animals in which aspirin abolished CFRs, endogenous TFPI was depleted by a bolus of a polyclonal antibody against rabbit TFPI, and the effects on restoration of CFRs were monitored. In 5 of 6 animals in which aspirin abolished CFRs, depletion of endogenous TFPI activity caused full restoration of CFRs., Conclusions: The data of the present study support the involvement of endogenous TFPI in the process of thrombus formation in vivo and its active role in modulating arterial thrombosis.

The extrinsic coagulation pathway is activated when circulating factor VII (FVII) gains access to tissue factor (TF) exposed as a consequence of vascular injury. Increasing evidence indicates that this TF-dependent activation of the coagulation plays an important role in the pathophysiology of intravascular thrombus formation. In the present study, we tested the effects of recombinant human, active site-blocked activated FVII (FVIIai) in a rabbit model of carotid artery thrombosis. Cyclic flow variations (CFVs), due to recurrent thrombus formation, were obtained in stenotic rabbit carotid arteries with endothelial injury. Carotid blood flow velocity was measured by a Doppler flow probe. After 30 minutes of CFVs, the animals received FVIIai (100 microg x kg(-1) x min(-1) intracarotid infusion for 10 minutes, n=9). If CFVs were abolished, animals were followed for 30 additional minutes, after which recombinant human activated FVII (FVIIa) was infused into the carotid artery (100 microg x kg(-1) x min(-1) for 10 minutes) to determine whether FVIIai could be displaced from TF by FVIIa, thus restoring CFVs. To establish the duration of action of FVIIai, an additional group of animals received FVIIai at the same dose as above, and after CFVs were inhibited, they were followed until CFVs were restored or for up to 6 hours. To determine whether CFVs could be restored by epinephrine after their abolition with FVIIai, increasing doses of epinephrine were administered to a third group of 6 animals. FVIIai abolished CFVs in 8 of 9 rabbits (P<.01). This effect was reversible, as FVIIa administration restored CFVs in all animals. Prothrombin times and activated partial thromboplastin times did not change significantly throughout the study. One single 10-minute infusion exerted complete antithrombotic effects for at least 6 hours, despite the fact that at this time point, plasma FVIIai levels were well below threshold concentrations. Epinephrine restored CFVs in 3 of 6 animals in which CFVs were inhibited by FVIIai. FVIIai exerts potent antithrombotic effects in this model; these effects were prolonged even after FVIIai was almost completely cleared from the circulation, probably as a result of the tight binding of FVIIai to TF. Thus, FVIIai might represent an antithrombotic substance of potential interest.

Background: Tissue factor (TF)-dependent activation of the coagulation is important in the pathophysiology of intravascular thrombus formation. We tested the effects of a monoclonal antibody against TF (AP-1) on lysis time induced by tissue-type plasminogen activator (TPA) and on reocclusion rate in a rabbit model of carotid artery thrombosis., Methods and Results: Intravascular thrombosis was obtained by placing an external constrictor around carotid arteries with endothelial injury. Carotid blood flow velocity ws measured continuously with a Doppler flow probe. Thirty minutes after thrombus formation, the rabbits received either AP-1 (0.15 mg/kg IV, n=8) or placebo (n=8). All rabbits also received TPA (80 microg/kg bolus plus 8 microg x kg(-1) x min(-1) infusion for up to 90 minutes or until reperfusion was achieved) and heparin (200 U/kg IV as a bolus). At reperfusion, TPA was discontinued, and the rabbits were followed for an additional 90 minutes. AP-1 shortened lysis time from 44+/-8 minutes (mean+/-SEM) in control rabbits to 26+/-7 minutes in AP-1 rabbits (P<.01). Reocclusion occurred in all control rabbits in 10+/-3 minutes, whereas it occurred in only two of eight AP-1 treated rabbits in 72 and 55 minutes (P<.01). No changes in prothrombin time and ex vivo platelet aggregation in response to various agonists were observed after AP-1 administration, indicating the absence of systemic effects by this antibody., Conclusions: TF exposure and activation of the extrinsic coagulation pathway play an important role in prolonging lysis time and mediating reocclusion after thrombolysis in this model. AP-1, a monoclonal antibody against TF, might be suitable as adjunctive therapy to TPA.

Background: Nitric oxide (NO), an endothelium-derived relaxing factor, plays an important role in regulating platelet activation. We evaluated the effect of NO in a canine model of intracoronary thrombosis, thrombolysis, and reocclusion., Methods and Results: Before thrombosis was induced, 34 anesthetized dogs were treated with a continuous intracoronary infusion of saline (n = 8); NG-nitro-L-arginine (L-NNA, n = 8), an inhibitor of NO synthetase; L-arginine (n = 7), the precursor for NO; or sodium nitroprusside (SNP, n = 11), an NO donor. Ten minutes after the infusion was begun, an electric current of 150 microA was applied to the endothelium of coronary arteries to induce thrombosis. Occlusive thrombi developed in all dogs in the saline group (38 +/- 4 minutes) and the L-NNA group (30 +/- 6 minutes), in 6 of 7 dogs in the L-arginine group (81 +/- 18 minutes), and in 6 of 11 dogs in the SNP group (102 +/- 21 minutes) (P < .01). The time to thrombus was prolonged by L-arginine (P < .05) and SNP (P < .01). After 3 hours of thrombus formation in coronary arteries, tissue plasminogen activator and heparin were administered intravenously. Thrombi were lysed in 4 (of 8) dogs in the saline group (71 +/- 8 minutes), in 4 (of 8) dogs in the L-NNA group (72 +/- 8 minutes), in 4 (of 6) dogs in the L-arginine group (50 +/- 14 minutes), and in 4 (of 6) dogs in the SNP group (49 +/- 11 minutes) (P > .05). After thrombolysis, coronary artery reocclusion developed in all reperfused dogs in the saline group (30 +/- 8 minutes) and in the L-NNA group (48 +/- 12 minutes), in 3 (of 4) reperfused dogs in the L-arginine group (123 +/- 26 minutes), and in 3 (of 4) reperfused dogs in the SNP group (128 +/- 19 minutes) (P < .01). The ex vivo platelet aggregation induced by collagen was inhibited after in vivo treatment with L-arginine or SNP., Conclusions: Increasing NO production or giving an NO donor may inhibit platelet aggregation and delay intracoronary thrombus formation and reocclusion after thrombolysis.

Tissue factor (TF) is a transmembrane protein that binds factor VII/VIIa, thus activating the extrinsic blood coagulation pathway. Since this pathway appears to be involved in the formation of intravascular thrombi, the anti-rabbit TF monoclonal antibody, AP-1, was produced and tested as an antithrombotic agent in a rabbit model of recurrent intravascular thrombosis. In this model, a plastic constrictor is positioned around the injured rabbit carotid arteries, and flow is monitored with a Doppler flow probe. This produces cyclic flow variation (CFV) in the carotid artery, which is caused by recurrent formation and dislodgment of thrombi at the site of the stenosis. After monitoring CFV pattern for 30 minutes, AP-1 was infused intravenously into nine rabbits at doses of 0.05 to 1.5 mg/kg body weight, and a control monoclonal antibody that does not react with rabbit TF was infused into four additional rabbits. In all rabbits receiving AP-1, CFV was abolished, and a steady normal blood flow was restored, indicating that thrombus formation had been blocked by AP-1. By contrast, in all rabbits that received the control monoclonal antibody, CFV continued unaltered. There was no change in the partial thromboplastin time and ex vivo platelet aggregation to several different agonists after infusion of AP-1, indicating an absence of systemic effects on the coagulation process. We conclude that activation of the extrinsic coagulation pathway has a key role in triggering intravascular thrombosis and that an anti-TF monoclonal antibody is an effective antithrombotic agent that could have therapeutic potential for humans.

Background: Platelet activating factor (PAF) is a phospholipid released upon stimulation by a variety of cells and has been implicated in several pathophysiological events such as asthma and inflammatory diseases. However, although the ability to aggregate platelets in vitro was the first biological activity ascribed to PAF, its role in contributing to the in vivo formation of arterial thrombi has not been thoroughly clarified., Methods and Results: Intravascular platelet aggregation was initiated in two different animal models of arterial stenosis and endothelial injury. An external constrictor was positioned around rabbit carotid arteries and canine coronary arteries. After placement of the constrictor, a typical pattern of flow developed in the stenotic vessels. This pattern of flow, characterized by progressive reductions of carotid or coronary blood flow followed by spontaneous or induced restorations of flow (cyclic flow variations, CFVs), is related to recurrent platelet aggregation at the site of the stenosis followed by dislodgment of the thrombus. After observing CFVs for 30 minutes, BN52021 (up to 1.2 mg/kg), a potent and selective PAF antagonist, was given intravenously to rabbits (n = 12) and dogs (n = 10). BN52021 completely inhibited CFVs in 10 of 12 rabbits, whereas it was relatively ineffective in abolishing CFVs in dogs (only 2 of 10 animals inhibited). This different effect of BN52021 was not explained by too small a dose of the drug to achieve a complete blockade of PAF receptors in dogs, since ex vivo platelet aggregation was completely inhibited in both rabbits and dogs in response to exogenous PAF at concentrations up to 10(-5) mol/L. In a second group of 10 dogs, the hypothesis that PAF may become an important mediator of CFVs in dogs only several hours after endothelial injury was tested. After 30 minutes of baseline CFVs, these animals received a bolus of BN52021 up to 1.2 mg/kg. After this treatment, CFVs were completely abolished in 2 of 10 animals. The remaining 8 dogs were followed for an additional 8-hour period, at the end of which a second bolus of BN52021 was given. At this time, BN52021 was effective, as CFVs were abolished in 6 of 8 animals. These effects of BN52021 at 8 hours were not the consequence of a cumulative dose of the compound, since ex vivo platelet aggregation in response to PAF returned to baseline values immediately before administering the second dose. To identify possible sources of PAF other than aggregating platelets at the site of arterial stenosis, dogs in a third group were killed after 30 minutes (n = 7) and after 8 hours (n = 8) of CFVs. Histological sections of the stenotic coronary artery showed a marked leukocyte infiltration in these arterial segments after 8 hours of CFVs, whereas sections from dogs killed after 30 minutes showed only moderate or no infiltration., Conclusions: These data demonstrate that PAF plays an important role as a mediator of platelet aggregation in vivo in rabbits and dogs. In the canine model, PAF appears to become more important after leukocyte infiltration of the arterial wall, as it may contribute to initiating enough platelet activation to lead to cyclic flow variations at sites of arterial stenosis and endothelial injury. Data from the present study suggest that PAF antagonists may be used as antiplatelet agents.

It has been shown that endothelium-derived relaxing factor (EDRF) may inhibit platelet aggregation in vitro through activation of platelet-soluble guanylate cyclase. To assess whether EDRF may also affect platelet function in vivo, intravascular platelet aggregation was initiated by placing an external constrictor around endothelially injured rabbit carotid arteries. Carotid blood flow velocity was measured continuously by a Doppler flow probe placed proximal to the constrictor. After placement of the constrictor, cyclic flow reductions (CFRs), due to recurrent platelet aggregation, developed at the site of the stenosis. After CFRs were observed for 30 minutes, a solution of authentic nitric oxide (NO, n = 10) was infused into the carotid artery via a small catheter placed proximally to the stenosis. Before infusion of NO, CFR frequency averaged 18.3 +/- 2.9 cycles per hour, and CFR severity (lowest carotid blood flow as percentage of baseline values) was 6 +/- 1%. NO completely inhibited CFRs in all animals, as shown by the normal and constant pattern of carotid blood flow (CFR frequency, 0 cycles per hour, p < 0.001; carotid blood flow, 92 +/- 5%, p = NS versus baseline). These effects were transient; CFRs were restored spontaneously within 10 minutes after cessation of NO infusion. After CFRs returned, S-nitroso-cysteine (S-NO-cys), a proposed form of EDRF, was infused into the carotid artery. S-NO-cys also abolished CFRs in all animals but at a significantly lower dose than NO (0.3 +/- 0.1 versus 12 +/- 4 nmol/min). The role of endogenously released EDRF in modulating in vivo platelet function was then tested in additional experiments. In 10 animals, endogenous release of EDRF was stimulated by infusing acetylcholine into the aortic root during CFRs. Infusion of acetylcholine was also associated with a complete inhibition of CFRs, similar to that observed during exogenous infusion of NO or S-NO-cys. These antithrombotic effects of acetylcholine were completely lost when EDRF synthesis was prevented by administration of the L-arginine analogue NG-monomethyl L-arginine (L-NMMA). Furthermore, in six additional rabbits the basal release of EDRF was blocked by L-NMMA after CFRs had been previously abolished with aspirin or the combination of aspirin and ketanserin, a serotonin S2 receptor antagonist. L-NMMA caused restoration of CFRs in all animals, indicating that even the basal release of EDRF is important in modulating platelet reactivity in vivo. Taken together, the data of the present study demonstrate that endogenous EDRF might importantly contribute to the modulation of platelet function in vivo.

Background: Experimental studies on the effects of alpha 2-adrenoceptors on regional coronary blood flow in normal and ischemic myocardium are highly controversial. A beneficial effect on regional ischemic myocardium has been demonstrated in different animal preparations with either alpha 2-adrenoceptor blockade or stimulation. Animal studies also demonstrated that postsynaptic alpha 2-adrenoceptors mediate vasoconstriction in coronary and femoral vascular beds. The aims of the study were 1) to investigate the effects of regional alpha 2-adrenoceptor stimulation on regional coronary blood flow in subjects with angiographically normal coronary arteries, 2) to assess the effect of alpha 2-adrenoceptor blockade on coronary circulation in control subjects, and 3) to examine the influence of atherosclerosis on coronary blood flow response to alpha 2-adrenoceptor blockade., Methods and Results: The effect of regional administration of BHT 933 (a selective alpha 2-adrenoceptor agonist) was studied in eight subjects with angiographically normal coronary arteries. The coronary blood flow velocity was measured using a subselective intracoronary 3F Doppler catheter and coronary diameter by quantitative coronary angiography. BHT 933 induced a reduction in coronary artery diameter from 2.5 +/- 0.6 mm to 1.8 +/- 0.4 mm (p less than 0.05) as well as in coronary blood flow velocity (from 6.4 +/- 0.9 cm/sec to 4.6 +/- 1.9 cm/sec, p less than 0.01). In some subjects, ST segment abnormalities occurred. In patients with angiographically normal coronary arteries (n = 6), the regional infusion of a selective alpha 2-adrenoceptor blocking agent after beta-blockade did not change coronary diameter or coronary blood flow velocity. In contrast, in patients with significant coronary stenoses (n = 6), regional infusion of an alpha 2-adrenoceptor blocking agent reduced regional coronary artery diameter (from 2.3 +/- 0.5 mm to 2.1 +/- 0.6 mm, p less than 0.01) as well as coronary blood flow velocity (from 5.8 +/- 0.8 cm/sec to 3.7 +/- 0.6 cm/sec, p less than 0.05); in addition, alpha 2-adrenoceptor blockade significantly increased coronary sinus plasma norepinephrine levels (from 300 +/- 144 pg/ml to 429 +/- 207 pg/ml, p less than 0.01)., Conclusions: The selective in vivo stimulation of alpha 2-adrenoceptors produces a reduction in coronary blood flow and diameter in humans with angiographically normal coronary arteries. alpha 2-Adrenergic blockade does not change coronary blood flow in subjects with angiographically normal coronary arteries (suggesting no resting alpha 2-adrenergic vasoconstrictor tone), whereas in patients with coronary artery stenosis, regional coronary blood flow decreases after alpha 2-receptor blockade. Finally, our data also suggest that alpha 2-adrenoceptors participate in the modulation of sympathetic neuronal norepinephrine release in the human heart.

Background: This study was designed to test the hypothesis that endogenously produced nitric oxide protects against platelet aggregation and cyclic flow variations in stenosed and endothelium-injured arteries of mongrel dogs., Methods and Results: NG-Monomethyl-L-arginine (L-NMMA), an inhibitor of nitric oxide formation, was administered at 5 mg/kg to 15 dogs after the left anterior descending coronary artery was mechanically injured and narrowed by external constrictors and to nine dogs before endothelial injury of the femoral artery and after injury and moderate arterial constriction. Treatment with L-NMMA resulted in cyclic flow variations (as detected by external Doppler flow probes) in the left anterior descending artery of seven of 15 dogs and in the femoral artery of four of nine dogs after endothelial injury. L-Arginine, the precursor for nitric oxide synthesis, was administered at 60 mg/kg and abolished cyclic flow variations in each of the 11 dogs. D-Arginine did not change the L-NMMA-induced cyclic flow variations. Saline infusion did not induce or change cyclic flow variations in any of the animals. Acetylcholine (1, 10, and 100 micrograms/min; n = 9) was administered in the femoral artery of nine additional dogs before and after endothelial injury in moderately stenosed femoral arteries. Acetylcholine did not induce cyclic flow variations in any animal; however, it did increase the severity of cyclic flow variations that developed in severely stenosed arteries. The diameter of the femoral artery was measured by intravascular ultrasound imaging. L-NMMA caused vasoconstriction of normal arteries, but no change was detected in endothelium-injured arteries. In contrast, L-arginine caused vasodilation of normal arteries, but, again, no change was noted in endothelium-injured arteries. Acetylcholine dilated normal femoral arteries but constricted arteries with endothelial injury. In both in vitro and ex vivo platelet studies, L-NMMA enhanced platelet aggregation, whereas L-arginine significantly reduced platelet aggregation. D-Arginine and acetylcholine showed no effect on platelet aggregation., Conclusions: Promotion of nitric oxide production decreases platelet aggregation and may eliminate cyclic flow variations, whereas a reduction in nitric oxide formation enhances platelet aggregation and may induce cyclic flow variations. Acetylcholine causes vasoconstriction at the femoral arterial site of endothelial injury and may increase the severity of cyclic flow variations.

Percutaneous transluminal coronary angioplasty (PTCA) and early coronary thrombolysis are now widely used to treat selected patients with atherosclerotic coronary artery disease and acute myocardial infarction, respectively. However, the efficacy of these procedures may be limited by the occurrence of thrombotic complications. Restenosis of the dilated vessel, which occurs in about 30% of the patients, is considered the Achilles' heel of PTCA. Experimental and clinical data suggest that restenosis after PTCA may be mediated by platelet attachment at the site of balloon dilation, with a consequent release of platelet-derived mitogen factors able to stimulate intimal hyperplasia. Similarly, a thrombotic reocclusion of the infarct-related coronary artery may significantly reduce the potential benefits of early thrombolysis. This reocclusion occurs in up to 30-35% of the patients successfully reperfused after suspension of the thrombolytic agent, despite the concomitant use of heparin. Increasing evidence indicates that intracoronary platelet activation and aggregation play a major role in the pathophysiology of reocclusion. First, it has been demonstrated that a marked increase in thromboxane A2 production occurs at the moment of reperfusion in patients with acute myocardial infarction undergoing successful thrombolysis. Second, in experimental models of coronary thrombosis, reocclusion after thrombolysis can be prevented or markedly delayed by antiplatelet interventions, such as administration of a monoclonal antibody against the platelet glycoprotein (GP) IIb and IIIa--the putative fibrinogen receptor on platelet membrane whose exposure seems to be an obligatory step for platelet aggregation to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

The goal of the present study was to demonstrate that intracoronary platelet deposition may trigger intense vasoconstriction of large epicardial coronary arteries in vivo and that this is largely mediated by thromboxane A2 and serotonin released by activated platelets. Cyclic flow variations (progressive declines in blood flow followed by sudden restorations of flow) due to recurrent intracoronary platelet activation and thrombus formation were induced by damaging the endothelium and placing a cylindrical constrictor on the left anterior descending coronary artery (LAD) in open-chest, anesthetized dogs. Coronary diameters were measured in vivo by means of ultrasonic crystals sutured on the LAD immediately distal to the constrictor (LAD1) and 1 cm below (LAD2) and on the circumflex coronary artery (Cx). Coronary artery diastolic diameters were measured continuously before and during cyclic flow variations and after they were abolished by administration of LY53857, a serotonin-receptor antagonist (group 1, n = 7), or SQ29548, a thromboxane-receptor antagonist (group 2, n = 7). During cyclic flow variations, at the nadir of coronary flow, LAD1 (a site of maximal platelet accumulation) cross-sectional area decreased by 52 +/- 10% and 38 +/- 6% in group 1 and 2 animals, respectively (p less than 0.001 compared with values recorded during a brief LAD occlusion obtained by a suture snare), whereas LAD2 (a site of minimal or no platelet accumulation) cross-sectional area did not differ from that recorded during the brief LAD occlusion. SQ29548 abolished cyclic flow variations in seven of seven dogs and LY53857 in six of seven, but they affected the increased coronary vasoconstriction differently: LAD1 cross-sectional area increased by 32 +/- 6% of the control value in SQ29548-treated animals, whereas it returned to baseline dimension values in the LY53857-treated group as these interventions also abolished the cyclic flow variations. We conclude that a marked coronary vasoconstriction may be triggered by local platelet deposition and that thromboxane A2 and serotonin are mediators of this vasoconstriction.

Human recombinant tissue-type plasminogen activator (rt-PA) has been shown to be an effective and safe agent for coronary thrombolysis in patients with acute myocardial infarction. However, thrombolysis is associated with a high rate of acute reocclusion after discontinuation of rt-PA. The goals of the present study were to assess whether reocclusion after thrombolysis is caused by intracoronary platelet aggregation and to determine the role of thromboxane A2 (TxA2) and serotonin (5HT) in mediating this phenomenon. Accordingly, coronary thrombosis was induced in anesthetized, open-chest dogs by insertion of a copper coil into the left anterior descending coronary artery (LAD). LAD blood flow was monitored throughout the experiment by means of a Doppler flow probe placed proximally to the coil. Thrombolysis was achieved with rt-PA (0.05 mg/kg bolus + micrograms/kg/min infusion) in 23 +/- 3 min. rt-PA was then discontinued and each animal received a bolus of heparin (150 U/kg) every hour. Reperfusion was followed by repeated cycles of gradual occlusions followed by spontaneous restorations of blood flow (cyclic flow variations, CFVs) before a persistent occlusion recurred. In control dogs (n = 6), heparin alone did not prevent CFVs and reocclusion time was 25 +/- 4 min. Administration of an intravenous bolus of 0.2 +/- 0.06 mg/kg SQ29548, a TxA2/prostaglandin H2-receptor antagonist, and an intravenous bolus of 0.2 +/- 0.04 mg/kg ketanserin, a 5HT2-receptor antagonist, completely abolished CFVs in six of six dogs and reocclusion time was greater than 158 +/- 14 min (p less than .01).(ABSTRACT TRUNCATED AT 250 WORDS)

It has recently been demonstrated that acute hypercholesterolemia per se, independently of its atherogenic effect, increases the extent of myocardial injury in rabbits undergoing coronary artery occlusion-reperfusion. Estimation of myocardial blood flow after reperfusion indicated that this deleterious effect was due to a vascular obstruction that limited the efficacy of reperfusion. The goal of this study was to evaluate the role played by platelets in contributing to the occurrence of this deleterious effect. Accordingly, New Zealand White rabbits were fed a standard laboratory chow diet (plasma cholesterol 67 +/- 12 mg/dl) or a 2% cholesterol-enriched diet for 3 days (plasma cholesterol 329 +/- 70 mg/dl). In a first series of experiments autologous platelets were labeled with 111In-oxine. After labeling, platelets were reinjected in the same animal and 30 min later coronary artery occlusion (CAO) was induced. CAO was maintained for 30 min followed by 5.5 hr of reperfusion. The animals were then killed, their hearts were excised, and each left ventricle was divided into ischemic and normally perfused samples. Myocardial samples were then counted in a gamma counter. Platelet accumulation ratio, i.e., 111In activity in the ischemic myocardium per gram of tissue divided by 111In activity in the normal myocardium per gram of tissue, was calculated. The ratio was 2.4 +/- 0.2 (mean +/- SEM) in controls (n = 7) and 10.3 +/- 1.0 in the cholesterol-fed group (n = 6, p less than .001), indicating that a marked accumulation of platelets occurs in the ischemic myocardium of hypercholesterolemic rabbits. To evaluate the importance of this phenomenon, another series of experiments was performed.(ABSTRACT TRUNCATED AT 250 WORDS)

We have reported previously that thromboxane A2 (TXA2) and serotonin (5-HT, 5-hydroxytryptamine) are important mediators of cyclic flow variations (CFVs) in a canine model of coronary artery stenosis and endothelial injury. The present study tested the hypothesis that a TXA2 receptor antagonist is more effective in reducing intracoronary platelet deposition at sites of endothelial injury and severe stenosis than a 5-HT2 receptor antagonist. CFVs developed after placing a plastic constrictor around the left anterior descending coronary artery (LAD) in 51 of 56 dogs. Autologous platelets labeled with 111In were injected in 48 animals. Ten control dogs (group 1A) were killed after CFVs were observed for 1 hour at the nadir of coronary blood flow. Five dogs (group 1B) did not develop CFVs after placement of the constrictor. CFVs were abolished with SQ 28668 (2.75 +/- 0.36 mg/kg, group 2) and SQ 29548 (0.45 +/- 0.1 mg/kg, group 3), two different TXA2 and PGH2 receptor antagonists, in eight of 10 and six of seven dogs, respectively. In eight of 10 dogs (group 4), CFVs were abolished with ketanserin (0.66 +/- 0.12 mg/kg), a 5-HT2 receptor antagonist. In group 2, 3, and 4 dogs, the respective drugs were given so that the minimal dose required to abolished CFVs was administered. In six of six dogs (group 5), a higher dose of ketanserin (i.e., 1.5 mg/kg) was used to abolish CFVs. At death, intracoronary platelet deposition was evaluated by calculating the LAD platelet accumulation ratio (111In activity in the LAD/111In activity in the circumflex coronary artery) in 43 dogs and, in 22 dogs, by microscopic examination of the LAD. A marked LAD platelet accumulation ratio was found in group 1A dogs at the stenotic site and in segments immediately distal to it. The LAD platelet accumulation ratio was significantly reduced by both the low and the high doses of ketanserin compared with group 1A dogs (p less than 0.001). However, the two TXA2 receptor antagonists further reduced the LAD platelet accumulation ratio compared with ketanserin-treated animals (p less than 0.01). Microscopic examination confirmed these findings. We conclude that SQ 28668 and SQ 29548, two different TXA2 receptor antagonists, reduce residual intracoronary platelet deposition associated with CFVs in this canine model more effectively than ketanserin, a 5-HT2 receptor antagonist.

Impairment of left ventricular function is a major consequence of acute myocardial infarction. Several interventions have been proposed to reduce the extent of myocardial tissue undergoing necrosis after cornoracy artery occlusion. Therapy for patients with acute myocardial infarction has long relied on interventions aimed at reducing oxygen consumption, such as administration of beta-blockers and nitrates. However, despite clinical evidence that these interventions can reduce mortality or prevent left ventricular dilatation, no clear benefit has been observed on left ventricular function. Over the past few years, treatment of acute myocardial infarction has radically changed. Availability of several thrombolytic agents has made reperfusion of ischemic myocardium a routine procedure. Early reperfusion has been shown to be the most powerful intervention to reduce infarct size and minimize left ventricular dysfunction in experimental preparations. Several clinical trials have also demonstrated that patients with acute myocardial infarction may greatly benefit from early thrombolysis, as this procedure is associated with improvement of global and regional left ventricular function and reduction in mortality. However, in spite of its obvious advantages, reperfusion might result in a paradoxical tissue damage that may blunt the net beneficial effect of restoring perfusion of ischemic myocardium. Reperfusion-mediated myocardial injury has been shown to occur in several experimental preparations and it has been proposed that generation of toxic oxygen metabolites at the moment of reflow is responsible for the occurrence of this phenomenon. Indeed, administration of free radical scavengers may significantly reduce the extent of reperfusion injury and improve contractile recovery in experimental preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

The goal of this study was to determine the effects of acute hypercholesterolemia on the evolution of myocardial infarction in a preparation of coronary occlusion-reperfusion. New Zealand white rabbits were fed a 2% cholesterol-enriched diet for 3 days (plasma cholesterol 329 +/- 70 mg/dl), or maintained on the control diet (plasma cholesterol 67 +/- 12 mg/dl). Temporary (30 min) coronary artery occlusion was performed in open-chest rabbits with a suture snare. The snare was released to permit reperfusion. When the animals were killed 5.5 hr later, left ventricles were cut into 3 mm slices. Infarct size was determined by planimetry of tetrazolium-stained slices while the area at risk of infarction (hypoperfused zone) was determined by planimetry of the "cold spots" on autoradiograms of the slices that contained 99m Tc-labeled microspheres that had been injected 1 min after occlusion. Infarct size, expressed as percent of the hypoperfused zone, was 42.8 +/- 1.3% (n = 10) in the control group and was increased by approximately 100% in cholesterol-fed animals to 83.7 +/- 2.0% (n = 10, p less than .001). To test the hypothesis that vascular obstruction (no reflow) might account for the larger infarct size, thioflavin S was injected immediately before the animals were killed to demarcate perfused myocardium in three additional groups of animals: standard chow-fed rabbits (n = 5), cholesterol-fed rabbits (n = 5), and standard chow-fed rabbits that, in addition, received an infusion of isoproterenol (0.1 microgram/kg/min, n = 6), an intervention believed to increase infarct size through a mechanism not dependent on the no-reflow phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic changes of the thrombus after its formation due to platelet activation may affect the speed of thrombolysis. In the present study, we wanted to evaluate the role played by thromboxane A2 (TXA2) and serotonin (5HT) in mediating platelet activation during lysis of intracoronary thrombi with human recombinant tissue-type plasminogen activator (t-PA). Coronary thrombi were induced in 26 anesthetized, open-chest dogs by inserting a copper coil into the left anterior descending coronary artery (LAD). LAD blood flow was monitored throughout the experiment by means of a Doppler flow probe placed proximally to the coil. Presence of the thrombus was documented for 30 minutes. The dogs were then assigned to one of four groups as follows: group 1 dogs (n = 8), serving as controls, received a bolus of heparin (200 units/kg) and a bolus of t-PA (80 micrograms/kg) followed by a continuous infusion (8 micrograms/kg/min) for up to 90 minutes or until reperfusion was achieved; group 2 dogs (n = 10) received, immediately before heparin and t-PA, an intravenous bolus of SQ29548 (SQ) (0.4 mg/kg, a selective TXA2-receptor antagonist) and LY53857 (LY) (0.2 mg/kg, a selective serotonin S2-receptor antagonist); group 3 dogs (n = 7) received, before heparin and t-PA, an intravenous bolus of SQ alone (0.4 mg/kg); and group 4 dogs (n = 7) received, before heparin and t-PA, an intravenous bolus of LY alone (0.2 mg/kg). After thrombolysis, all dogs were monitored for 90 minutes or until a persistent reocclusion occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

We have speculated previously that the abrupt conversion from chronic stable to unstable angina and the continuum to acute myocardial infarction may result from myocardial ischemia caused by progressive platelet aggregation and dynamic vasoconstriction themselves caused by local increases in thromboxane and serotonin at sites of coronary artery stenosis and endothelial injury. Platelet aggregation and dynamic coronary artery vasoconstriction probably result from the local accumulation of thromboxane and serotonin and also relative decreases in the local concentrations of endothelially derived vasodilators and inhibitors of platelet aggregation, such as endothelium-derived relaxing factor (EDRF) and prostacyclin. With severe reductions in coronary blood flow caused by these mechanisms, platelet aggregates may increase, and an occlusive thrombus composed of platelets and white and red blood cells in a fibrin mesh may develop. When coronary arteries are occluded or narrowed for a sufficient period of time by these mechanisms, myocardial necrosis, electrical instability, or sudden death may occur. We believe that unstable angina and acute myocardial infarction are a continuum in relation to the process of coronary artery thrombosis and vasoconstriction. When the period of platelet aggregation or dynamic vasoconstriction at sites of endothelial injury and coronary artery stenosis is brief, unstable angina or non-Q wave infarction may occur. However, when the coronary artery obstruction by these mechanisms is prolonged for several hours, Q wave myocardial infarction results. Chronic endothelial injury and coronary artery stenosis are probably associated with the accumulation of platelets, white and red blood cells, and a fibrin mesh at the site of stenosis and endothelial injury.

Atrial natriuretic factor (ANF) release is known to be regulated by distension of the atrial wall; other factors affecting ANF secretion have not yet been defined. In order to evaluate the effects of the reflex activation of the sympathetic nervous system on ANF plasma levels, in 11 patients with essential hypertension progressive deactivation of carotid baroreceptors was induced by 4-min graded increases in external neck tissue pressure. Carotid sinus hypotension induced progressive increases in blood pressure (BP), heart rate (HR) and forearm vascular resistance (FVR), while plasma renin activity and catecholamine concentrations did not change significantly. Despite the lack of changes in right atrial pressure during this manoeuvre, plasma ANF levels showed a progressive and significant reduction, which was correlated with the increase in FVR. Although a contribution by other factors cannot be ruled out, our data suggest that the reflex activation of sympathetic nervous system is associated with reduced ANF release, independent of changes in atrial pressure.

We have reported previously that thromboxane A2/prostaglandin (PG)H2 and serotonin independently mediate the occurrence of cyclic flow variations (CFVs) in a canine preparation of severe coronary artery narrowing. This may be due to an effect of these substances on platelets and/or the vascular wall. We tested the hypothesis that there is a cooperative effect between thromboxane A2/PGH2 and serotonin receptor stimulation in the development of CFVs in this animal preparation. After placement of a hard plastic cylindrical constrictor around the left anterior descending coronary artery, CFVs develop and are characterized by repetitive cycles of declines in coronary blood flow and abrupt increases in flow. In a control group of dogs, CFV frequency (cycles/hour) and severity (lowest coronary blood flow just before its restoration) did not change significantly over a 3 hr interval. In a second group of dogs, CFVs were established after constrictor placement, abolished with the serotonin (5HT2) receptor antagonist ketanserin, and reestablished by the continuous infusion of serotonin into the left atrium. Serotonin-induced CFVs were then abolished with a thromboxane A2/PGH2 receptor antagonist, SQ29,548, or a thromboxane synthetase inhibitor, dazoxiben (UK37,248). The relative specificity of the respective antagonists, SQ29,548 and ketanserin, was determined in canine platelets and rat aortic vascular strips. No significant cross-reactivity between ketanserin and SQ29,548 was found. Thus, the data obtained in these studies demonstrate a cooperative interaction between thromboxane A2/PGH2 and serotonin S2 receptors that contributes to the development of CFVs in this experimental preparation.