Microvascular Coronary Flow Research Articles

(1060) - Direct Procurement and Perfusion Supplemented with the Senomorphic Agent Ruxolitinib Improves the Microvascular Coronary Flow in Hearts Donated After Circulatory Death in Dependence on Donor Sex and Age

(1060) - Direct Procurement and Perfusion Supplemented with the Senomorphic Agent Ruxolitinib Improves the Microvascular Coronary Flow in Hearts Donated After Circulatory Death in Dependence on Donor Sex and Age

Abstract 12378: Association of Hypertensive Disorders of Pregnancy With Coronary Microvascular Dysfunction 8-10 Years After Delivery

Introduction: Hypertensive disorders of pregnancy ( HDP ) are associated with subsequent adverse cardiac remodeling and cardiovascular disease ( CVD ). The pathophysiologic mechanisms linking HDP to CVD, including the role of myocardial microvascular disease, are understudied. Hypothesis: Individuals with HDP history will have abnormal microvascular coronary flow reserve ( CFR ) 8-10 years after delivery and abnormal CFR will correlate with left ventricular ( LV ) remodeling. Methods: Individuals with pregnancies delivered 2008-2010 underwent burst-replenishment myocardial contrast echocardiography (2017-2020) to quantify myocardial perfusion at rest and during dobutamine stress. Video intensity vs. time data were used to derive β, the rate of rise of video intensity, a correlate for myocardial blood flow. CFR was calculated as the ratio of β at peak stress to β at rest, averaged across LV myocardial regions of interest. Results: We studied 91 individuals (age 38±6, 9.1±0.9 years post-delivery), 19 with a history of HDP). Individuals with abnormal CFR (β ratio <2.0, n=13) had higher pre-pregnancy BMI, baseline heart rate, hemoglobin A1c, and a history of HDP (46.2% vs 16.7%; p =0.026). Association of CFR and HDP was attenuated after adjusting for pre-pregnancy BMI and hemoglobin A1c ( p =0.114). In exploratory subgroup analyses, individuals with both LV remodeling (relative wall thickness>0.42) and HDP had the highest proportion of microvascular dysfunction (41.7% vs. +HDP-LV remodeling 14.3%, -HDP+LV remodeling 7.7%; p =0.0498). Conclusions: Individuals with HDP history may be more likely to have coronary microvascular dysfunction one decade after delivery. Larger studies are needed to determine if microvascular dysfunction may be a mechanism for development of CVD among individuals with HDP.

Assessment of coronary microcirculation alterations in a porcine model of no-reflow using ultrasound localization microscopy: a proof of concept study.

Coronary microvascular obstruction also known as no-reflow phenomenon is a major issue during myocardial infarction that bears important prognostic implications. Alterations of the microvascular network remains however challenging to assess as there is no imaging modality in the clinics that can image directly the coronary microvascular vessels. Ultrasound Localization Microscopy (ULM) imaging was recently introduced to map microvascular flows at high spatial resolution (∼10μm). In this study, we developed an approach to image alterations of the microvascular coronary flow in exvivo perfused swine hearts. A porcine model of myocardial ischemia-reperfusion was used to obtain microvascular coronary alterations and no-reflow. Four female hearts with myocardial infarction in addition to 6 controls were explanted and placed immediately in a dedicated preservation and perfusion box manufactured for ultrasound imaging. Microbubbles (MB) were injected into the vasculature to perform Ultrasound Localization Microscopy (ULM) imaging and a linear ultrasound probe mounted on a motorized device was used to scan the heart on multiple slices. The coronary microvascular anatomy and flow velocity was reconstructed using dedicated ULM algorithms and analyzed quantitatively. We were able to image the coronary microcirculation of exvivo swine hearts at a resolution of tens of microns and measure flow velocities ranging from 10mm/s in arterioles up to more than 200mm/s in epicardial arteries. Under different aortic perfusion pressures, we measured in large arteries of a subset of control hearts an increase of flow velocity from 31±11mm/s at 87mmHg to 47±17mm/s at 132mmHg (N=3 hearts, P<0.05). This increase was compared with a control measurement with a flowmeter in the aorta. We also compared 6 control hearts to 4 hearts in which no-reflow was induced by the occlusion and reperfusion of a coronary artery. Using average MB velocity and average density of MB per unit of surface as two ULM quantitative markers of perfusion, we were able to detect areas of coronary no-reflow in good agreement with a control anatomical pathology analysis of the cardiac tissue. In the no-reflow zone, we measured an average perfusion of 204±305MB/mm2 compared to 3182±1302MB/mm2 in the surrounding re-perfused area. We demonstrated this approach can directly image and quantify coronary microvascular obstruction and no-reflow on large mammal perfused hearts. This is a first step for noninvasive, quantitative and affordable assessment of the coronary microcirculation function and particularly coronary microvascular anatomy in the infarcted heart. This approach has the potential to be extended to other clinical situations characterized by microvascular dysfunction. This study was supported by the French National Research Agency (ANR) under ANR-21-CE19-0002 grant agreement.

Coronary Flow Assessment Using 3-Dimensional Ultrafast Ultrasound Localization Microscopy

BackgroundDirect assessment of the coronary microcirculation has long been hampered by the limited spatial and temporal resolutions of cardiac imaging modalities. ObjectivesThe purpose of this study was to demonstrate 3-dimensional (3D) coronary ultrasound localization microscopy (CorULM) of the whole heart beyond the acoustic diffraction limit (<20 μm resolution) at ultrafast frame rate (>1000 images/s). MethodsCorULM was performed in isolated beating rat hearts (N = 6) with ultrasound contrast agents (Sonovue, Bracco), using an ultrasonic matrix transducer connected to a high channel–count ultrafast electronics. We assessed the 3D coronary microvascular anatomy, flow velocity, and flow rate of beating hearts under normal conditions, during vasodilator adenosine infusion, and during coronary occlusion. The coronary vasculature was compared with micro-computed tomography performed on the fixed heart. In vivo transthoracic CorULM was eventually assessed on anaesthetized rats (N = 3). ResultsCorULM enables the 3D visualization of the coronary vasculature in beating hearts at a scale down to microvascular structures (<20 μm resolution). Absolute flow velocity estimates range from 10 mm/s in tiny arterioles up to more than 300 mm/s in large arteries. Fitting to a power law, the flow rate–radius relationship provides an exponent of 2.61 (r2 = 0.96; P < 0.001), which is consistent with theoretical predictions and experimental validations of scaling laws in vascular trees. A 2-fold increase of the microvascular coronary flow rate is found in response to adenosine, which is in good agreement with the overall perfusion flow rate measured in the aorta (control measurement) that increased from 8.80 ± 1.03 mL/min to 16.54 ± 2.35 mL/min (P < 0.001). The feasibility of CorULM was demonstrated in vivo for N = 3 rats. ConclusionsCorULM provides unprecedented insights into the anatomy and function of coronary arteries at the microvasculature level in beating hearts. This new technology is highly translational and has the potential to become a major tool for the clinical investigation of the coronary microcirculation.

A computational analysis of atrial fibrillation effects on coronary perfusion across the different myocardial layers

Patients with atrial fibrillation (AF) may present ischemic chest pain in the absence of classical obstructive coronary disease. Among the possible causes, the direct hemodynamic effect exerted by the irregular arrhythmia has not been studied in detail. We performed a computational fluid dynamics analysis by means of a 1D-0D multiscale model of the entire human cardiovascular system, enriched by a detailed mathematical modeling of the coronary arteries and their downstream distal microcirculatory districts (subepicardial, midwall and subendocardial layers). Three mean ventricular rates were simulated (75, 100, 125 bpm) in both sinus rhythm (SR) and atrial fibrillation, and an inter-layer and inter-frequency analysis was conducted focusing on the ratio between mean beat-to-beat blood flow in AF compared to SR. Our results show that AF exerts direct hemodynamic consequences on the coronary microcirculation, causing a reduction in microvascular coronary flow particularly at higher ventricular rates; the most prominent reduction was seen in the subendocardial layers perfused by left coronary arteries (left anterior descending and left circumflex arteries).

108 Atrial fibrillation effects on coronary perfusion across the different myocardial layers: a computational analysis

Abstract Aims Atrial fibrillation (AF) patients may present ischaemic chest pain in the absence of classical obstructive coronary disease. Among the possible causes, the direct haemodynamic effect exerted by the irregular arrhythmia has not been studied in detail. Methods and results A computational fluid dynamics analysis was performed by means of a 1D-0D multiscale model of the entire human cardiovascular system, characterized by a detailed mathematical modelling of the coronary arteries and their downstream distal microcirculatory districts (subepicardial, midwall, and subendocardial layers). Three mean ventricular rates were simulated in both sinus rhythm (SR) and AF: 75, 100, 125 b.p.m. We conducted inter-layer and inter-frequency analysis of the ratio between mean beat-to-beat blood flow in AF compared to SR (Q¯AP/Q¯SR Inter-layer analysis showed that, for each simulated ventricular rate, Q¯AP/Q¯SR progressively decreased from the epicardial to the endocardial layer in the distal left coronary artery districts (P-values &amp;lt; 0.001 for both left anterior descending artery—LAD, and left circumflex artery—LCx), while this was not the case for the distal right coronary artery (RCA) district. Inter-frequency analysis showed that, focusing on each myocardial layer, Q¯AP/Q¯SR progressively worsened as the ventricular rates increased in all investigated microcirculatory districts (LAD, LCx, and RCA) (P-values &amp;lt; 0.001 for all layer-specific comparisons). Conclusions AF exerts direct haemodynamic consequences on the coronary microcirculation, causing a reduction in microvascular coronary flow particularly at higher ventricular rates; the most prominent reduction was seen in the subendocardial layers perfused by left coronary arteries (LAD and LCx).

Assessment of Myocardial Perfusion by Angiographic Methods in Tortuous Coronary Arteries.

The relationship between coronary tortuosity (CorT) and tissue-level myocardial perfusion is not clear. We investigated tissue perfusion in myocardial territories supplied by tortuous coronary arteries. Among patients who had undergone coronary angiography, patients with reported CorT, those with ≥1 coronary artery were included in the study group (100 patients). The control group included patients with normal coronary arteries (100 patients). Thrombolysis In Myocardial Infarction frame count (TFC) and myocardial blush grade (MBG) were calculated for each coronary artery. Mean TFC was significantly higher in tortuous right coronary artery (RCA), left anterior descending (LAD) artery, and circumflex (Cx) artery compared to their non-tortuous counterparts (28.81 ± 6.463 vs 21.94 ± 3.328, P = .009; 43.28 ± 5.698 vs 36.17 ± 3.875, P = .006; 29.35 ± 4.111 vs 23.821 ± 2.639; P < .001, respectively). Mean MBG was also significantly lower in tortuous RCA, LAD, and Cx, compared to their normal counterparts (2.78 ± 0.417 vs 2.98 ± 0.155, P < .001; 2.74 ± 0.483 vs 2.97 ± 0.164, P < .001; 2.92 ± 0.277 vs 2.99 ± 0.110, P < .001, respectively). For each tortuous coronary artery, TFC was similar for every MBG category. Tortuous coronary arteries have higher TFC and lower MBG, suggesting impaired epicardial and microvascular coronary flow, when compared to normal coronary arteries.

The Woman's Heart: Insights into New Potential Targeted Therapy.

Cardiovascular disease is an increasingly common cause of death in women. There is as yet no consensus on the analysis of cardiovascular risk factors with regard to the specific, personalised treatment of pre- and post-menopausal women. Clinically significant cardioprotective and antiremodelling effects have been observed in animal and human studies exploring chronic inhibition of phosphodiesterase type 5 (PDE5). The relationship between the heart, estrogens and PDE5 inhibitors (PDE5is) remains unclear. Experimental data suggest potential beneficial effects on cardiac geometry, function, endothelial function and microvascular coronary flow in women. It was recently postulated that the efficacy of PDE5is is estrogen-dependent in female heart disease. A registered randomised, placebo-controlled study, RECOGITO (NCT01803828), aimed at identifying the genderspecific efficacy of long-term PDE5 inhibition in diabetic cardiomyopathy, is currently recruiting patients. Estrogen receptor modulation could be a new promising approach to heart protection via PDE5is. PDE5is could be indicated as a gender-oriented strategy in modulated cardiac dysfunction and remodelling and in cardiac risk factors for selected cardiovascular diseases.

Coronary Flow Parameters Assessed by Transesophageal Echocardiography in Patients with Coronary Artery Ectasia Baseline Measurements and the Effects of Intravenous Verapamil

Background and rationale: Coronary artery ectasia (defined as luminal dilatation 1.5 to 2 times the adjacent healthy coronary artery or the diameter of the corresponding coronary artery in the control group in case of diffuse ectasia) is an uncommon disorder, usually associated with underlying myocardial ischemia. Micro-circulatory dysfunction has been demonstrated as one possible mechanism to explain ischemia in this disorder. Calcium antagonists have been proven to relieve microvascular spasm. Aim of the study: To test the hypothesis that relieving microvascular spasm in patients with coronary artery ectasia, through intravenous administration of verapamil, may result in improvement of microvascular coronary flow as reflected by coronary flow parameters assessed by transesophageal echocardiography (TEE). Patients and methods: Thirty patients with angiographically documented coronary artery ectasia of the left anterior descending artery were prospectively enrolled in the current study. Ten patients with normal coronary arteries were included as controls. All forty patients underwent TEE using pulsed wave Doppler (PWD) to measure peak systolic and diastolic velocities (m/sec); systolic, diastolic and total velocity time integrals (cm); and the systolic, diastolic and total coronary blood flow (cm³/min) in the proximal LAD before and after intravenous injection of verapamil (0.1 mg/kg). Results: Resting systolic, diastolic, and total coronary blood flow (cm³/min) were significantly higher in patients with ectasia compared to normal subjects (60.83 ± 27.7 cm³/min versus 25.31 ± 9.01 cm³/min, p<0.001; 126.89 ± 49.22 cm³/min versus 53.15 ± 18.30 cm³/min, p<0.001; and 188.02 ± 70.36 cm³/min versus 78.46 ± 25.97 cm³/min, p<0.001). There was a trend, not reaching statistical significance, towards higher basal peak velocities in normal subjects compared to patients with ectasia. In patients with coronary artery ectasia, intravenous injection of verapamil resulted in an increase in all observed coronary flow parameters including: peak systolic velocity (m/sec) from 0.19 ± 0.05 to 0.21 ± 0.04, p=<0.05, peak diastolic velocity (m/sec) from 0.39 ± 0.11 to 0.48 ± 0.15, p=<0.001, systolic velocity time integral (cm) from 3.0 ± 1.05 to 3.38 ± 0.78, p=<0.05, diastolic velocity time integral (cm) from 6.22 ± 1.97 to 8.42 ± 2.09, p=<0.001; total velocity time integral (cm) from 9.22 ± 2.73 to 11.8 ± 2.64, p=<0.001, systolic coronary blood flow (cm³/min) from 60.83 ± 27.7 to 69.0 ± 22.7, p=<0.05, diastolic coronary blood flow (cm³/min) from 126.89 ± 49.22 to 173.01 ± 62.4 p=<0.001, and total coronary blood flow (cm³/min) from 188.02 ± 70.36 to 242.0 ± 81.82, p=<0.001. Conclusion: Intravenous administration of verapamil resulted in statistically significant improvement of coronary flow parameters in patients with coronary artery ectasia. Further studies are needed to confirm whether continued treatment with verapamil translates to symptomatic improvement in the clinical setting.

SAVEME (Myocardial Salvage After Rescue Angioplasty: Evaluation by Magnetic Resonance) Study: Rationale and Study Design

ABSTRACT Introduction Atherosclerotic disease accounts for one-third of deaths annually, as it often leads to complications such as ST-elevation myocardial infarction (STEMI). Rescue percutaneous coronary intervention (PCI) is indicated in case of thrombolytic therapy failure administered in this scenario. However, the benefits regarding mortality rate reduction and the amount of myocardium that is actually salvaged are not well established. The development of new tools, including cardiac magnetic resonance imaging, to identify the myocardium at risk and the infarcted area has increased diagnostic accuracy. Differently from the context of primary PCI, little is known about the association between epicardial and microvascular coronary flow following rescue PCI and the salvaged myocardial area. The aim of this study is to evaluate whether there is an association between coronary flow and the salvaged myocardial area identified by magnetic resonance imaging. Methods This will be a prospective, open, single-center, intervention study. A total of 72 patients with STEMI who underwent rescue PCI after documented failure of the fibrinolytic therapy, and were transferred to our institution, will be selected, observing a pharmacoinvasive strategy. Conclusions At the end of this study, the authors expect to contribute to the knowledge about coronary flow and its association with the amount of salvaged cardiac muscle after rescue PCI. This type of information that can help to understand which cases can benefit the most from rescue PCI.

Microvascular Coronary Flow Comparison in Acute Myocardial Infarction Angioplasty treated with a mesh covered stent (MGUARD Stent) versus Bare Metal Stent

Distal embolization of thrombus/platelet aggregates decreases myocardial reperfusion during primary percutaneous coronary intervention (PCI), and is associated with worse immediate and long-term prognosis of patients with ST-elevation myocardial infarction (STEMI). Assess the efficacy of a mesh covered stent (MGuard™ stent, MGS) in preventing distal embolization and microvascular reperfusion impairment during primary PCI, compared with a bare metal stent (BMS). Forty patients with STEMI referred for primary PCI were randomized for stenting the culprit lesion with the MGS (n = 20) or a BMS (n = 20). Blinded experts performed off-line measurements of angiographic epicardial and microvascular reperfusion criteria: TIMI flow grade, myocardial blush, corrected TIMI frame count (cTFC). At baseline clinical, angiographic and procedural variables were not different between groups. Post PCI TIMI flow grade was similar in both groups. We observed better myocardial Blush grade in group MGS compared to BMS (median value 3.0 vs 2.5, 2p = 0.006) and cTFC (mean cTFC: MGS 19.65 ± 4.07 vs BMS 27.35 ± 7.15, 2p < 0.001, cTFC mean difference MGS-BMS: 7.7, CI 95%: 3.94 to 11.46). MGS stent group had a higher percentage of successful angioplasty (cTFC ≤ 23: MGS 85% vs BMS 30%, 2p < 0.001). We had two cases of acute stent thrombosis (one for each group) at 30days follow up, but no clinical events at 6 months follow up. In this exploratory study, MGS significantly improved microvascular reperfusion criteria compared with a BMS in primary PCI. However its safety and impact on clinical outcomes should be verified in larger randomized clinical trials.

Microvascular coronary flow comparison in acute myocardial infarction angioplasty treated with a mesh-covered stent versus bare metal stent

Microvascular coronary flow comparison in acute myocardial infarction angioplasty treated with a mesh-covered stent versus bare metal stent

The non-invasive documentation of coronary microcirculation impairment: role of transthoracic echocardiography

Transthoracic Doppler echocardiographic-derived coronary flow reserve is an useful hemodynamic index to assess dysfunction of coronary microcirculation. Isolated coronary microvascular abnormalities are overt by reduced coronary flow reserve despite normal epicardial coronary arteries. These abnormalities may occur in several diseases (arterial hypertension, diabetes mellitus, hypercholesterolemia, syndrome X, aortic valve disease, hypertrophic cardiomyopathy and idiopathic dilated cardiomyopathy). The prognostic role of impaired microvascular coronary flow reserve has been shown unfavourable especially in hypertrophic or idiopathic dilated cardiomyopathies. Coronary flow reserve reduction may be reversible, for instance after regression of left ventricular hypertrophy subsequent to valve replacement in patients with aortic stenosis, after anti-hypertensive treatment or using cholesterol lowering drugs. Coronary flow reserve may increase by 30% or more after pharmacological therapy and achieve normal level >3.0. In contrast to other non invasive tools as positron emission tomography, very expensive and associated with radiation exposure, transthoracic Doppler-derived coronary flow reserve is equally non invasive but cheaper, very accessible and prone to a reliable exploration of coronary microvascular territories, otherwise not detectable by invasive coronary angiography, able to visualize only large epicardial arteries.

Expression of Endomyocardial Nitric Oxide Synthase and Coronary Endothelial Function in Human Cardiac Allografts

Background Inducible nitric oxide synthase (iNOS) is expressed and is functionally active in the presence of transplant arteriosclerosis. However, the early involvement of iNOS in alterations of microvascular endothelial function in the absence of preexisting lesions remains unclear; this information would be of prognostic value. We studied the course of iNOS mRNA expression, transcardiac nitric oxide production, and their potential association with microvascular coronary endothelial dysfunction in human cardiac allografts. Methods and Results A total of 42 patients were studied at 1, 6, and 12 months after heart transplantation. Microvascular coronary flow velocity reserve (CFVR) was tested in an endothelium-dependent (acetylcholine) and -independent manner (adenosine) using a Doppler flow wire. Endomyocardial iNOS expression was determined by reverse transcription polymerase chain reaction. iNOS protein and nitrotyrosine levels were detected by immunohistochemistry. Transcardiac plasma nitrite/nitrate (NOx) levels were measured by the Griess reaction. CFVR was impaired in 26.1% of patients (n=11) at 1 month and in 31% of patients (n=13) at 12 months after heart transplantation. Patients who developed impaired CFVR in the first year showed a significant increase in iNOS gene expression. Patients with impairment of CFVR 1 month after heart transplantation had higher levels of iNOS mRNA than patients with a normal CFVR. Patients with an initial impairment of CFVR who did not improve over time presented with significantly higher iNOS mRNA levels. iNOS protein and nitrotyrosine were expressed in the endomyocardial vessels of patients with impaired CFVR. Transcardiac NOx release was higher in patients with impaired CFVR. Conclusions In human cardiac allografts, microvascular endothelial dysfunction is associated with an enhanced endomyocardial iNOS mRNA expression and higher transcardiac NOx production and is accompanied by the expression of nitrotyrosine protein, suggesting peroxynitrite plays a role in the disease process. The data from the present study suggest an important role for the iNOS/nitric oxide pathway in the regulation of microvascular function in the absence of preexisting atherosclerotic lesions.

Coronary flow reserve and nitric oxide synthases after cardiac transplantation in humans

Coronary endothelial dysfunction may precede morphological changes in both the epicardial conduit and microvascular resistance vessels in heart transplant recipients. Since the development of transplant atherosclerosis is the major limiting factor for long-term survival, the identification of early mediators of vasomotor dysfunction may be of therapeutic interest. We therefore investigated the potential relationship between the expression of nitric oxide synthases (NOS) and coronary endothelial function in human cardiac transplant recipients over time. Forty-two human cardiac transplant recipients were studied at 1 and 12 months after heart transplantation (HTx). The microvascular coronary flow velocity reserve (CFVR) was tested for endothelium-dependent (acetylcholine) and -independent (adenosine) stimuli by intravascular Doppler flow-wire. Epicardial diameter changes were evaluated by quantitative coronary angiography. Endomyocardial inducible (iNOS) and endothelial constitutive nitric oxide synthase were determined by RT-PCR. Nitric oxide production (nitrite and nitrate (NOx)) and TNF-alpha were measured in plasma samples from the aorta and coronary sinus. CFVR was impaired in 26.1% (n=11) of patients at 1 month and in 31% (n=13) 12 months after HTx. iNOS-mRNA levels were significantly higher in patients with impaired endothelium-dependent CFVR. In addition, only in these patients were TNF-alpha levels higher and these correlated with plasma NOx levels at 1 and 12 months post-HTx (1 month: r=0.81, P=0.001; 12 months: r=0.62, P=0.04). Coronary microcirculatory dysfunction in response to acetylcholine is present in nearly 30% of patients during the first year following transplantation. These patients present with higher iNOS-mRNA expression and TNF-alpha plasma levels. Selective modulation of the TNF-alpha/iNOS-pathway may be of therapeutic value to improve coronary endothelial dysfunction in cardiac transplant recipients.

An association between microvascular endothelial dysfunction, transcardiac nitric oxide production and pro-inflammatory cytokines after heart transplantation in humans

Abstract Endothelial dysfunction anticipates the development of transplant coronary artery disease (TxCAD) observed more than 1 year after transplantation (HTx). We investigated whether in patients early after HTx myocardial inducible and constitutive nitric oxide synthases (iNOS; cNOS) are expressed and cardiac nitric oxide production occurs. Moreover, a possible relationship to alterations in endothelium dependent and independent vasomotor function was assessed. Forty-two transplant recipients were studied 37 ± 5 days after HTx. Microvascular coronary flow velocity reserve (CFVR) was tested endothelium dependent (acetylcholine; 30 μg/min × 5 min/i.c.) and independent (adenosine; 160 μg/min × 5 min/i.c.) by Doppler flow wire. Flow velocity increase by a factor greater than 2 was considered normal. Quantitative coronary angiography was used to assess epicardial vasomotor function in response to the same stimuli. Myocardial iNOS and cNOS gene expression were detected by semiquantitative reversed transcriptase polymerase chain reaction. Plasma nitrite levels (μM) were measured by spectrophotometry. Cytokines (TNF-a, IL-6; pg/ml) were measured by enzyme linked immunosorbent assay. In 26.1% of patients (n = 11; group A) an impaired endothelium dependent CFVR (1.65 ± 0.23 increase) was observed; in 73.9 % (n = 31, group B) a normal endothelium dependent CFVR (3.0 ± 0.7 increase; P = 0.003) was observed. Myocardial iNOS and cNOS gene expression did not differ between the two groups. Transcardiac cytokine production was noted in 58.8% of patients for IL-6 and in 53.3% for TNF-α. Coronary sinus (CS) levels of TNF-α, IL-6 and nitrite were higher in group A. A significant increase in nitrite production was found only in patients with impaired endothelium dependent CFVR (aorta: 43.9 ± 3.7 vs CS: 52.8 ± 5.6, P = 0.05), suggesting transcardiac nitric oxide production. In addition, CS nitrite levels correlated with CS TNF-a levels in patients with impaired CFVR (r = 0.44, P = 0.003). Microvascular endothelium dependent CFVR is impaired in 26% of patients early after HTx. Activation of cytokines and the NO pathway seem to be involved in this vasomotor dysfunction The association between cardiac nitric oxide production and TNF-a in this group indicates a chronic high immunologic process, which may represent an early and important target for therapy and prevention of TxCAD.

An association between microvascular endothelial dysfunction, transcardiac nitric oxide production and pro-inflammatory cytokines after heart transplantation in humans.

Endothelial dysfunction anticipates the development of transplant coronary artery disease (TxCAD) observed more than 1 year after transplantation (HTx). We investigated whether in patients early after HTx myocardial inducible and constitutive nitric oxide synthases (iNOS; cNOS) are expressed and cardiac nitric oxide production occurs. Moreover, a possible relationship to alterations in endothelium dependent and independent vasomotor function was assessed. Forty-two transplant recipients were studied 37 +/- 5 days after HTx. Microvascular coronary flow velocity reserve (CFVR) was tested endothelium dependent (acetylcholine; 30 microg/min x 5 min/i.c.) and independent (adenosine; 160 microg/min x 5 min/i.c.) by Doppler flow wire. Flow velocity increase by a factor greater than 2 was considered normal. Quantitative coronary angiography was used to assess epicardial vasomotor function in response to the same stimuli. Myocardial iNOS and cNOS gene expression were detected by semiquantitative reversed transcriptase polymerase chain reaction. Plasma nitrite levels (microM) were measured by spectrophotometry. Cytokines (TNF-alpha, IL-6; pg/ml) were measured by enzyme linked immunosorbent assay. In 26.1% of patients (n = 11; group A) an impaired endothelium dependent CFVR (1.65 +/- 0.23 increase) was observed; in 73.9% (n = 31, group B) a normal endothelium dependent CFVR (3.0 +/- 0.7 increase; P = 0.003) was observed. Myocardial iNOS and cNOS gene expression did not differ between the two groups. Transcardiac cytokine production was noted in 58.8% of patients for IL-6 and in 53.3% for TNF-alpha. Coronary sinus (CS) levels of TNF-alpha, IL-6 and nitrite were higher in group A. A significant increase in nitrite production was found only in patients with impaired endothelium dependent CFVR (aorta: 43.9 +/- 3.7 vs CS: 52.8 +/- 5.6, P = 0.05), suggesting transcardiac nitric oxide production. In addition, CS nitrite levels correlated with CS TNF-alpha levels in patients with impaired CFVR (r = 0.44, P = 0.003). Microvascular endothelium dependent CFVR is impaired in 26% of patients early after HTx. Activation of cytokines and the NO pathway seem to be involved in this vasomotor dysfunction The association between cardiac nitric oxide production and TNF-alpha in this group indicates a chronic high immunologic process, which may represent an early and important target for therapy and prevention of TxCAD.

Microvascular flow vectors in normal and hypertrophic myocardium as determined by the method of colored microspheres

Sequential in vivo infusion of two differently colored microsphere suspensions into the left atrium of normal and hypertrophic rat myocardium revealed that certain coronary capillaries contained microsphere aggregates of both colors. A capillary flow vector was established based on the sequence of colors embolized within each aggregate. Critical examination of flow vectors among neighboring capillaries enabled the characterization of capillary flow direction. Results indicated a predominance in concurrent flow direction, which decreased significantly ( P < 0.001) with capillaries further removed from an individual reference capillary. The percentage of concurrent flow was also flound to be significantly lower in subendocardium ( P < 0.001) than in midmyocardium. Cardiac hypertrophy was not a contributing factor to the above findings. This study provides previously unattainable data regarding transmural capillary flow direction and suggests regional adaptations in coronary microvascular flow.

Single bolus administration of recombinant tissue plasminogen activator: effects on infarct related vessel patency, microvascular perfusion, and microvascular reocclusion in a canine model of thrombotic occlusion/reperfusion

The aim was to evaluate the thrombolytic efficacy of recombinant double chain tissue plasminogen activator (Duteplase, t-PA) given as a single intravenous bolus versus an infusion in a canine model of coronary arterial occlusion/reperfusion. Coronary arterial thrombi were induced by a copper coil (placed under fluoroscopic control) in the left anterior descending coronary artery of anaesthetised dogs. Following 90 min thrombotic occlusion, animals were randomly assigned to one of two treatment groups: group 1 = t-PA infused intravenously at 0.6 x 10(6) IU.kg-1.h-1, or group 2 = t-PA (0.6 x 10(6) IU.kg-1) by intravenous bolus over 6 min. Both groups received concurrent heparin (six 1000 IU boluses, + 100 IU.kg-1.h-1) throughout t-PA administration and the 2 h reperfusion period. 16 beagle dogs of either sex were used, weight 9.2-20.3 kg. Radiolabelled microspheres were injected to assess microvascular coronary flow at various time points throughout the experimental period. Infarct related vessel patency (IRVP) was assessed arteriographically every 5 min. Infarct size was assessed histochemically at the end of the reperfusion period. IRVP was achieved within 42.9 (SEM 7.4) min and 43.1(7.0) min for infusion and bolus groups respectively; 60 min patency rates were 88% for both groups. t-PA restored full microvascular flow to ischaemic subendocardial and subepicardial regions in both groups compared to initial preocclusion regional blood flow. Extent of reactive hyperaemia was greater in infusion than bolus treatment animals: infusion group 1.18(0.15) v bolus group 0.72(0.14) ml.min-1.g-1 (subepicardial). Degree of microvascular reocclusion at 120 min reperfusion was similar for both groups despite aggressive anticoagulation throughout: infusion group 0.33(0.08) v bolus group 0.42(0.11) ml.min-1.g-1 (subendocardial). Areas of the myocardium at risk (R), absolute infarct size (I), and infarct risk ratio (I/R) were similar for both groups: R = 33.9(1.5) v 30.9(1.9)%; I = 15.9(3.1) v 13.3(3.1)%; I/R = 46.3(8.4) 42.1(9.2)%. Degree of systemic fibrinogenolysis was similar for both groups: infusion 1.65(0.40) to 0.67(0.07) g.litre-1 v bolus 1.68(0.15) to 0.96(0.12) g.litre-1. Single bolus administration of t-PA showed equivalent efficacy to infusion dosing in respect of IRVP, microvascular reperfusion, and microvascular reocclusion. As a result the degree of tissue necrosis (I/R ratio) was no different when comparing the two dosing regimens. Similar degrees of systemic fibrinogenolysis were observed for both treatment groups.

Enhanced myocardial salvage by maintenance of microvascular patency following initial thrombolysis with recombinant tissue plasminogen activator

The aim was to examine the value of a subthrombolytic maintenance infusion of recombinant double chain tissue plasminogen activator (BW t-PA, Duteplase) in preserving microvascular coronary flow following initial thrombolysis. Coronary arterial thrombi were induced by a copper coil (placed under fluoroscopic control) in the canine left anterior descending coronary artery. Complete vessel occlusion occurred within 10-15 min of coil placement. Following 90 min of thrombotic occlusion, animals received one of three treatments: group 1, vehicle 0.9% saline; group 2, t-PA 1.0 X 10(6) IU.kg-1.h-1 for 1 h; group 3, t-PA 1.0 X 10(6) IU.kg-1.h-1 for 1 h followed by 0.12 X 10(6) IU.kg-1.h-1 throughout the 2 h reperfusion period. Radiolabelled microspheres were administered to assess microvascular coronary flow at various time points throughout the experimental period. Experimental subjects were beagle dogs of either sex (n = 30), weight 8.9-14.3 kg. Main vessel patency (assessed fluoroscopically) was achieved within 40.0(SEM 4.0) min and 37.0(3.1) min for group 2 and group 3 animals respectively. Group 1 animals did not reperfuse. Full microvascular coronary flow was achieved following the lytic infusion of t-PA. However, microvascular flow to the ischaemic zone was significantly reduced at the end of the 2 h reperfusion phase in group 2 animals despite "aggressive" anticoagulation with heparin throughout the reperfusion period: subendocardial flow decreased from 0.74(0.14) to 0.24(0.08) ml.min-1.g-1; subepicardial flow decreased from 0.82(0.13) to 0.36(0.09) ml.min-1.g-1, p less than 0.05. Microvascular coronary flow to the ischaemic zone was better preserved following the maintenance infusion of t-PA given throughout the reperfusion phase: subendocardial flow decreased from 0.95(0.07) to 0.50(0.10) ml.min-1.g-1; subepicardial flow decreased from 0.73(0.04) to 0.52(0.08) ml.min-1.g-1. Thrombolytic reperfusion led to salvage of the ischaemic myocardium, with infarct/risk ratio decreasing from 75.0(10.0)% in group 1 to 46.3(11.0)% in group 2, p less than 0.05. Further salvage of the ischaemic myocardium followed a lytic plus maintenance infusion of t-PA, with infarct/risk ratio decreasing to 35.5(6.7)% but this did not reach statistical significance. t-PA consistently achieved main vessel reperfusion within 40 min (mean) of instituting therapy in our model, leading to marked salvage of ischaemic myocardium. The data also suggest that maintenance infusion of t-PA helps preserve microvascular coronary flow throughout reperfusion and tends to reduce infarct size further.