1/12. Mechanisms of coronary microcirculatory dysfunction in patients with aortic stenosis and angiographically normal coronary arteries.BACKGROUND: Development of left ventricular hypertrophy in aortic stenosis (AS) is accompanied by coronary microcirculatory dysfunction, demonstrated by an impaired coronary vasodilator reserve (CVR). However, evidence for regional abnormalities in myocardial blood flow (MBF) and the potential mechanisms is limited. The aims of this study were to quantitatively demonstrate differences in subendocardial and subepicardial microcirculation and to investigate the relative contribution of myocyte hypertrophy, hemodynamic load, severity of AS, and coronary perfusion to impairment in microcirculatory function. methods AND RESULTS: Twenty patients with isolated moderate to severe AS were studied using echocardiography to assess severity of AS, cardiovascular magnetic resonance to measure left ventricular mass (LVM), and PET to quantify resting and hyperemic (dipyridamole 0.56 mg/kg) MBF and CVR in both the subendocardium and subepicardium. In the patients with most severe AS (n=15), the subendocardial to subepicardial MBF ratio decreased from 1.14 /-7 at rest to 0.92 /-7 during hyperemia (P<0.005), and subendocardial CVR (1.43 /-3) was lower than subepicardial CVR (1.78 /-35; P=0.01). Resting total LV blood flow was linearly related to LVM, whereas CVR was not. Increase of total LV blood flow during hyperemia (mean value, 89.6 /-6%; range, 17% to 233%) was linearly related to aortic valve area. The decrease in CVR was related to severity of AS, increase in hemodynamic load, and reduction in diastolic perfusion time, particularly in the subendocardium. CONCLUSIONS: CVR was more severely impaired in the subendocardium in patients with LVH attributable to severe AS. Severity of impairment was related to aortic valve area, hemodynamic load imposed, and diastolic perfusion rather than to LVM.- - - - - - - - - - ranking = 1keywords = coronary, circulation (Clic here for more details about this article) |
2/12. Changes in cerebral hemodynamics assessed by transcranial Doppler ultrasonography in children after head injury.INTRODUCTION: head injury is an important factor in children's morbidity and mortality. Arterial vasospasm and probably resulting from this, delayed ischemic deficit are important sequels of head trauma with detrimental effects on outcome. These problems have already been well studied in adults, but not in children. The noninvasiveness and ease in use of transcranial Doppler ultrasound technique (TCD) make it an ideal tool for the assessment of changes in cerebral circulation not only for the purposes of diagnosis but also for follow-up. patients AND methods: The authors review the present literature and analyze the usefulness of TCD as used in a group of 27 head-injured children aged 3-16 years. GCS/CCS score, CT pictures and neurological status were estimated. TCD examination was performed on the 2nd day after injury and each of the following 5 days or until normalization of flow velocities. blood flow velocity was measured in the middle cerebral artery, the anterior cerebral artery and the extracranial portion of the internal carotid artery. The pulsatility index was also read.RESULTS: A significant correlation was found between changes in blood flow parameters and neurological status. High blood flow velocities seemed to be caused by hyperemia rather than by vasospasm. CONCLUSION: The results confirm that TCD is a useful method in the management of children after head injury.- - - - - - - - - - ranking = 0.04760788987627keywords = circulation (Clic here for more details about this article) |
3/12. Cerebral hyperperfusion after angioplasty and stenting of a totally occluded left subclavian artery: a case report.Cerebral hyperperfusion syndrome is documented after angioplasty of carotid and vertebral artery lesions. The authors report the first instance of cerebral hyperperfusion syndrome in the posterior cerebral circulation after angioplasty and stenting of a totally occluded left subclavian artery.- - - - - - - - - - ranking = 0.04760788987627keywords = circulation (Clic here for more details about this article) |
4/12. Fallacy of thoracic side-branch steal from the internal mammary artery: analysis of left internal mammary artery coronary flow during thoracic side-branch occlusion with pharmacologic and exercise-induced hyperemia.In some patients, myocardial ischemia after coronary artery bypass graft surgery has been attributed to a coronary steal phenomenon through a thoracic side branch originating from the left internal mammary artery (LIMA), even in the absence of subclavian or LIMA stenosis. To demonstrate that coronary flow through the LIMA is unchanged by occlusion of a LIMA side branch, we examined LIMA coronary flow velocity measurements (0.014" Doppler flow wire) in three patients at rest, during adenosine hyperemia, and again during hyperemia induced by left arm exercise before and again after the balloon occlusion of the thoracic side branch. For the three patients, no significant changes in resting or hyperemic flow were noted due to side-branch occlusion. Before side-branch occlusion, pharmacologic intra-arterial (adenosine) coronary flow reserve (hyperemic-to-basal flow velocity ratio) was 2.6, 1.5, and 3.2 and exercise flow reserve was 2.1, 1.3, and 1.2, respectively. After side-branch occlusion, pharmacologic coronary flow reserve was 2.5, 1.8, and 2.7 with exercise flow reserve of 1.8, 1.1, and 1.3, respectively. Under most ordinary circumstances, thoracic side-branch steal does not exist and that side-branch occlusion does not alter LIMA flow at rest or during pharmacologic or exercise-induced hyperemia. These data further suggest that a demonstration of the physiologic value of side-branch occlusion should precede surgical or percutaneous interruption of the thoracic artery in such patients.- - - - - - - - - - ranking = 0.86581100920339keywords = coronary (Clic here for more details about this article) |
5/12. Optimizing revascularization strategies in patients with multivessel coronary disease: impact of intracoronary pressure measurements.OBJECTIVES: In patients with multivessel coronary disease, the functional significance of each lesion is often unclear, and preinterventional stress tests may be inconclusive. In this setting, intracoronary pressure measurements may be helpful to define the optimal revascularization strategy. methods: Twenty-five consecutive patients (aged 64 /- 11 years) with multivessel disease, inconclusive stress tests or not performed stress tests, and an angiographically intermediate coronary artery stenosis in at least 1 major vessel underwent intracoronary pressure measurements. Myocardial fractional flow reserve was measured for the intermediate lesions under the condition of maximum hyperemia induced by intravenous adenosine (140 microg x kg(-1) x min(-1). Revascularization strategies based on angiographic information alone were compared with treatment strategies based on fractional flow reserve results. RESULTS: The original recommendation of the revascularization procedure of choice (bypass operation or angioplasty) was changed in 9 patients (36%) on the basis of the results of fractional flow reserve measurements. In 6 more patients, pressure measurements led to a change in the recommended number of anastomoses to be aimed for during the operation. Within diffusely diseased vessels, fractional flow reserve provided an exact segmental resolution of pathologic vessel resistance for optimal graft placement. Significant left main disease was confirmed in 3 of 6 patients and was detected in 3 angiographically unsuspected cases. CONCLUSIONS: In patients with multivessel disease, coronary pressure-derived fractional flow reserve is a valuable tool to guide clinical decision making and support cardiologists and cardiovascular surgeons in the composition of optimal revascularization strategies.- - - - - - - - - - ranking = 1.1255543119644keywords = coronary (Clic here for more details about this article) |
6/12. Relationship between coronary blood flow and perfusion pressure during reactive hyperemia: a case report in an awake unanesthetized woman with normal coronary arteries.The linear relationship between coronary blood flow and mean arterial pressure during reactive hyperemia is presented for the first time in an awake unanesthetized woman with normal coronary arteries during systemic hypotension induced by pharmacologic vasodilation. This case demonstrates the critical dependence of coronary flow reserve on simultaneous perfusion pressure.- - - - - - - - - - ranking = 0.95239211012373keywords = coronary (Clic here for more details about this article) |
7/12. Quantitative fluorimetric effects of leeching on a replanted ear.leeching is used to relieve venous congestion in microscopically replanted tissues. A quantitative description of the effects of leech application on tissue perfusion has not been reported. We report a case of an ear replantation in which venous congestion was consistently improved with leeching. In four instances, quantitative fluorimetry, which indicated impaired circulation and prompted leech application, showed restoration of normal circulation patterns following leech application. The fluorometric studies suggested that arterial inflow improved and venous congestion was relieved.- - - - - - - - - - ranking = 0.09521577975254keywords = circulation (Clic here for more details about this article) |
8/12. thallium-201 uptake in variant angina: probable demonstration of myocardial reactive hyperemia in man.Myocardial thallium scintigraphy was performed in four subjects with variant angina and in one subject with isolated, fixed coronary obstruction. Three subjects with variant angina had short episodes of ischemic ST-segment elevation that lasted 20--100 seconds. thallium scintigrams demonstrated excess uptake in regions judged to be ischemic by angiographic and electrocardiographic criteria. Two subjects, one with variant angina and the other with a fixed coronary lesion, had prolonged episodes of ischemia that lasted 390--900 seconds. Both had reduced thallium uptake in the ischemic regions. We conclude that myocardial reactive hyperemia is the cause of excess thallium uptake in patients with variant angina who have short episodes of myocardial ischemia.- - - - - - - - - - ranking = 0.17316220184068keywords = coronary (Clic here for more details about this article) |
9/12. pulmonary edema following relief of acute upper airway obstruction.Five children, aged one to five years, with severe upper airway obstruction, three of whom had epiglottitis and two of whom had laryngotracheobronchitis, developed acute pulmonary edema after the obstruction had been relieved by placement of an artificial airway. Although major physiologic changes, such as hypoxemia and massive sympathetic discharge, play a significant role in the development of acute pulmonary edema, we have postulated a possible etiological cause for the development of pulmonary edema in these children which involves a series of physiologic events. The generation of very high transpulmonary pressure gradients during inspiration is opposed by a decreased venous return due to the obstruction during exhalation. Airway pressures then fall abruptly with the insertion of the artifial airway, resulting in a sudden increase in venous return to the central circulation and marked increase in the intravascular hydrostatic pressures. The final result of this series of events is the development of pulmonary hyperemia and edema. The prevention of this situation must begin the moment the airway is inserted and involves the application of moderate amounts of continuous positive pressure to the airway, thus allowing time for circulatory adaption to take place.- - - - - - - - - - ranking = 0.04760788987627keywords = circulation (Clic here for more details about this article) |
10/12. Quantitative demonstration of dipyridamole-induced coronary steal and alteration by angioplasty in man: analysis by simultaneous, continuous dual Doppler spectral flow velocity.In the course of studying the effects of coronary angioplasty on branch vessel flow using two Doppler flow velocity guidewires, we quantitated simultaneous blood flow responses proximal and distal to a stenosis. The alterations of flow documented a horizontal epicardial steal induced during dipyridamole hyperemia, hyperemic flow reversal by intravenous aminophylline, and subsequent normalization of distal hyperemia after endoluminal enlargement by successful angioplasty. The quantitative physiology of the patient described here confirms one postulated mechanism of abnormal myocardial perfusion stress scintigraphy. Continuous dual flowire spectral coronary flow determinations appear to be a valuable method in verifying postulated mechanisms of various pharmacologic and mechanical stimuli influencing coronary blood flow in patients with atherosclerotic coronary artery disease.- - - - - - - - - - ranking = 0.69264880736271keywords = coronary (Clic here for more details about this article) |
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