摘要:

Thromboembolism may be considered as one of the manifestations of the response of blood to injury. Other manifestations of this include hemostasis, increased vessel permeability, and vasculitis; disturbances of the microcirculation may lead to tissue injury and organ dysfunction. The factors that can initiate these changes by stimulation of platelets are exposure of subendothelial tissue (collagen, basement membrane) and intravascular stimuli such as antigen-antibody complexes, viruses, bacteria, and endotoxin. These stimuli have a number of effects on blood; the interaction of the platelets with the above stimuli leads to the release of platelet constituents including ADP; the ADP causes the platelets to adhere to each other; the aggregated platelets cause acceleration of clotting; this and changes in blood flow promote the formation of fibrin around the platelet aggregates. Some of the stimuli such as collagen and antigen-antibody complexes also activate blood coagulation through factor XII; some of the materials released from these platelets affect the vessel wall. The initial platelet mass is transformed to a fibrin mass. There are compounds that inhibit the platelet release reaction, platelet aggregation, and blood coagulation and activate the fibrinolytic mechanism. It appears that by the selective use of these compounds we can improve our management of all aspects of thromboembolic disease related to vascular and intravascular stimuli.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Patients with supravalvular aortic stenosis frequently have higher phasic and mean blood pressures in the innominate artery than in the aorta distal to the stenosis, a finding never fully explained. Theoretically, this phenomenon could result from the impact of a jet upon blood within the innominate artery. Slowing of the jet would convert kinetic into potential energy, thus increasing pressure within the innominate artery. The aorta distal to the innominate artery would receive blood whose kinetic energy had been dissipated and would consequently remain at the same pressure as the aorta proximal to the origin of the innominate artery. This hypothesis was tested in a model simulating supravalvular aortic stenosis. Cinematography showed a jet directed into the innominate artery. Only after this jet was dispersed, did fluid turn backward to flow into the distal portion of the aorta. Observed pressure rises in the innominate artery corresponded closely with values predicted from the estimated kinetic energy of the jet. Dispersion of the jet by replacement of the stenotic orifice with an equally obstructive screen or proximal displacement of the stenosis (simulating valvular aortic stenosis) abolished the pressure difference. The results obtained were thus entirely consistent with the mechanism proposed to explain the elevated innominate artery pressures seen in supravalvular aortic stenosis.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The Coanda effect, the tendency of a jet stream to adhere to a wall, was investigated as an explanation of the unequal pressures in the upper extremities in patients with supravalvular aortic stenosis (SVAS). Of 56 patients with SVAS reviewed, 48 had unequal blood pressures in the upper extremities. The average difference was 18 mm Hg systolic. Although 11 of the 20 patients in the control group (valvular aortic stenosis) had some blood pressure asymmetry, the average difference was 3.5 mm Hg systolic. In valvular aortic stenosis, the velocity of the jet is quickly dissipated beyond the stenotic orifice, preventing any sustained high-velocity stream. However, the smooth, annular narrowing of SVAS creates a “step” between the orifice and the ascending aortic wall which enhances the natural affinity of a jet for a boundary wall and conserves the kinetic energy of the jet stream. In most patients with SVAS, the high-velocity stream is along the right aortic wall, causing disproportionately high pressure in the right arm.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The left ventricular ejection time (LVET) was studied by means of the carotid artery tracing in 512 elderly subjects (205 male and 307 female) who were between 60 and 90 years old (mean age, 70.5 years). A highly significant correlation was found between heart rate (HR) and LVET. The data on these aged subjects were compared and analyzed with the results previously reported concerning young and middle-aged adults. A small but significant increase of LVET with aging, independent of changes in HR and blood pressure, could be demonstrated by multiple regression analysis. A statistically significant difference existed between the sexes. The influence on LVET of parameters other than HR was small.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

To examine the electrocardiographic response to exercise in an older population, 280 participants in a longitudinal study of cerebrovascular disease were tested. Subjects were randomly selected from the total 50 to 69-year-old population of Birmingham, Alabama. Approximately 60% of the participants reached a heart rate more than 80% of their predicted maximal heart rate.Subjects were divided into three groups on clinical grounds: (I) vascular disease, (II) risk factor(s) only, and (III) normal. Positive tests (at least 0.10 mv of ischemic ST-segment depression) were most frequent in group I (24%), though not significantly different from group II (19%) and group III (12%).Hypercholesterolemia was significantly associated with a positive exercise test only in those subjects with vascular disease. Nonspecific ST-T wave changes on the resting electrocardiogram were associated with a positive test in all subjects, but with only a borderline test in those subjects without vascular disease. No significant associations were noted between abnormal exercise test and either cigarette smoking or hypertension.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The metabolic effects of glucagon on the heart were studied in subjects with and without coronary artery disease. In both groups, a moderate rise in the arterial glucose level occurred with practically unchanged glucose uptake by the myocardium. Myocardial oxygen extraction was also unchanged in both groups of subjects. In individuals with normal coronary arteries, myocardial extraction ratio of lactate was normal before and unchanged after glucagon administration. In patients with significant coronary artery disease, mean extraction ratio of lactate was very low before glucagon and increased markedly following its administration. Seven of 18 patients had production of lactate by the myocardium before glucagon, and this reverted to lactate extraction 5 min after glucagon administration. Left ventricular work index was found to increase more than indices of myocardial contractility and oxygen consumption, and improved aerobic lactate utilization during glucagon action may be partly related to the lower oxygen cost of work performance or improved cardiac efficiency. Arterial serum potassium level decreased in both groups of subjects after glucagon administration, with the appearance of a slightly negative potassium balance across the myocardium. The possible relationship of the cardiac inotropism induced by glucagon to intramyocardial ionic exchanges is discussed.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Seventeen male patients with angina pectoris due to coronary artery disease who had not received long-acting nitrites for at least 1 mo prior to this study were evaluated in a double-blind crossover study to investigate whether the presence of isosorbide dinitrate interfered with the effective response of exercise-induced angina to nitroglycerin administered sublingually. There was no significant difference in the duration of angina following nitroglycerin whether the patients were on no medication, sublingual placebo or sublingual isosorbide dinitrate. There was no significant difference in the blood pressure, heart rate, product of systolic blood pressure and heart rate, or electrocardiographic response after the complete relief of angina following sublingual nitroglycerin whether the patients were on no medication, sublingual placebo, or sublingual isosorbide dinitrate. These results indicate that long-acting nitrites do not cause any clinical impairment of the effective response of angina pectoris to sublingually administered nitroglycerin.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The relationship of the left ventricular end-diastolic pressure (LVEDP) and the pulmonary arterial “wedge” mean pressure (PAWMP) to the pulmonary artery end-diastolic pressure (PAEDP) was investigated by cardiac catheterization in 71 subjects. Pressure records were obtained simultaneously or immediately consecutively. In 15 subjects with normal LV function (LVEDP, 4 to 12 mm Hg) PAEDP was within 3 mm Hg of LVEDP (r = 0.70,P< 0.01) and within 3 mm Hg of PAWMP (r = 0.69,P< 0.01) in every instance.In 56 patients with LV dysfunction (LVEDP, 12 to 55 mm Hg), PAEDP was lower than LVEDP in 42, equal to LVEDP in six, and higher than the LVEDP in eight, who were in atrial fibrillation or had increased pulmonary vascular resistance (PVR). PAEDP correlated closely with PAWMP (r = 0.92,P< 0.001).In 30 patients with LV dysfunction in sinus rhythm, anawave was identified in the PA pressure tracing (PAa) prior to systole which coincided in time and magnitude to the PAWawave and was considered to represent retrograde transmission of the left atrial contraction wave. The PAapressure was within 5 mm Hg of the LVEDP (r = 0.94,P< 0.001) in all except four patients, two of whom had elevated PVR.Thus, in the presence of LV dysfunction and elevated LVEDP, PAEDP correlated well with PAWMP, but failed to represent LVEDP accurately, while PAawave pressure closely reflected LVEDP except when PVR was markedly increased.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

Simultaneously recorded values for mean left atrial pressure (LAMP) and end-diastolic pulmonary arterial pressure (PAEDP) were compared in 28 patients with acute or chronic cardiac disease. Atrial pressure was varied by alterations in blood volume or the administration of inotropic agents. One hundred twenty paired values were divided into three groups according to the pulmonary vascular resistance which was calculated on each occasion. Although LAMP and PAEDP were shown to correlate significantly at all levels of pulmonary vascular resistance, worthwhile estimates of LAMP could only be obtained from PAEDP when the pulmonary vascular resistance was normal.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID

摘要:

The usefulness of nontraumatic methods for measuring the left ventricular isometric contraction period (ICP) in myocardial infarction (MI) has been evaluated. The ICP was measured in 13 normal men and 38 patients admitted to a coronary care unit with chest pain, including 18 with acute MI, 12 with old MI, and nine with chest pain of miscellaneous origin; one of these nine was also included in the group with acute myocardial infarction. ICP was determined by three different methods: (1) time between the onset of systolic wave (A) of apexcardiogram (ACG) and the beginning of upstroke (C) of carotid pulse tracing (CPT); (2) time between A and ejection crest (E) of the ACG; and (3) time between the initial low frequency, low amplitude vibration of the first heart sound, and the C of CPT. Statistically significant differences of ICP between the normal group and the three groups of patients were demonstrated only by method 1. Likewise, acute coronary ligation in seven dogs produced characteristic changes in ICP by method 1, which were associated with a reduction in the left ventricular (LV) stroke volume, LV dp/dt, and the aortic flow velocity. The ICP obtained by method 1 appears to be of value in the bedside evaluation of acute myocardial infarction.

ISSN:0009-7322    

出版商:OVID    

年代:1970

数据来源: OVID