[Limitation of ECG for diagnosis of myocardial infarction].
Explore the source record for details and available documents.
Aged↗
Biomedical subjects
N Yoshimoto
Publications and source records attributed to N Yoshimoto.
Effects of a thromboxane A2 synthetase inhibitor on ventricular fibrillation threshold during coronary artery occlusion and reperfusion.
The effects of a new thromboxane A2 synthetase inhibitor (DP-1904) on electrical stability of the heart were tested in anesthetized, open chest dogs. The incidence of spontaneous ventricular arrhythmias, ventricular refractory period and ventricular fibrillation threshold (VFT) during ligation of the left anterior descending coronary artery (LAD) for 180 min and after reperfusion were measured as indices of stability. Ventricular fibrillation and ventricular tachycardia occurred spontaneously after ligation of LAD in 56% of 9 control dogs and 29% of 7 dogs which received intravenous DP-1904 (100 mg) before ligation of LAD (n.s.). In the control group, the ventricular refractory period decreased in the ischemic region; consequently, the difference in refractory period duration between the ischemic and non-ischemic regions (i.e., dispersion) increased 30 min after coronary ligation (7 +/- 9 ms vs 32 +/- 17 ms, p less than 0.05). The dispersion at 30 min after coronary ligation, though, was not affected in the DP-1904 treated group (2 +/- 4 ms vs 10 +/- 9 ms, n.s.). The VFT (determined with pulse trains) decreased from 28 +/- 5 mA to 15 +/- 11 mA (p less than 0.05) 30 min after coronary ligation in the control group, but was not affected (30 +/- 0 mA vs 27 +/- 4 mA) in the DP-1904 group. The plasma concentration of thromboxane B2 decreased after DP-1904 administration (baseline vs 30 min after coronary ligation: 475 +/- 165 pg/ml vs 165 +/- 74 pg/ml, n = 3, p less than 0.05), while the concentration of 6-keto-prostaglandin F1 alpha increased gradually. In conclusion, DP-1904 prevents a decline in electrical stability in the ischemic region of the canine heart during coronary occlusion.
6-Ketoprostaglandin F1 alpha↗
[Study of quantitative measurement of tricuspid regurgitation using Doppler echocardiography].
The volume of tricuspid regurgitation (VTR) was measured using two-dimensional color and continuous wave Doppler echocardiography. The value of VTR showed significant correlations with the maximum area (r = 0.77), the maximum distance (r = 0.73) and the maximum width (r = 0.59) in the regurgitant signal, right ventricular pressure (r = 0.63) and the diameter of right atrium (r = 0.40). When the tricuspid regurgitation was divided into two types in viewpoint of its flow direction-flow directed to center of atrium (A type) and that directed to atrial septum (B type), VTR showed closer correlations with the maximum area (r = 0.90) and the maximum distance (r = 0.87) in A type. But in B type, their relativities were decreased (r = 0.51 and r = 0.40, respectively). The VTR was well related with the severity of tricuspid regurgitation based on the Miyatake's classification. This evidence indicated that the quantitative measurement of tricuspid regurgitant volume using two-dimensional color and continuous wave Doppler echocardiography is more accurate and useful compared with conventional semi-quantitative method.
Adult↗
Effect of 2-nicotinamidethyl nitrate (SG 75) on coronary circulation.
The effect of a new chemical agent, SG 75, on coronary blood flow of anesthetized dogs has been examined. Intravenous administrations of this agent in a dose of 10 microgram/Kg or over caused a significant increase in blood flow of non-constricted coronary artery. Percent increases in flow were 40 (10 microgram/Kg), 95 (50 microgram/Kg), 145 (100 microgram/Kg), and 195 (250 microgram/Kg). The increases were significantly larger than those caused by the same doses of diltiazem, verapamil, nitroglycerin, isosolbide dinitrate, and papaverine. The durations of the increase in flow were 12 (10 microgram/Kg), 23 (50 microgram/Kg), 28 (100 microgram/Kg), and 46 min (250 microgram/Kg), and they were longer than those caused by diltiazem and verapamil. A slight reduction in left ventricular tension and an increase in aortic blood flow were also observed following the administrations of SG 75 in a dose of over 50 microgram/Kg. A decrease in heart rate was produced with a dose of over 500 microgram/Kg. However, PQ interval of electrocardiogram became shorter. Intravenous administrations of SG 75 in doses of 50 and 150 microgram/Kg caused an increase in blood flow of the constricted coronary artery, while nitroglycerin (10 and 30 microgram/Kg) and nifedipine (1 and 3 microgram/Kg) reduced it. The results indicate that SG 75 is a potent and long-acting coronary vasodilating agent and it causes an increase in blood flow of constricted as well as non-constricted coronary artery.
Animals↗
Prostaglandin E2 and epinephrine participate in cyclical reduction of coronary blood pressure and flow.
The effects of the agents that inhibited synthesis of prostaglandins (PGs) and thromboxanes (TXs) on cyclical reduction of blood flow in partially constricted coronary artery of anesthetized dog were examined. The cyclical reduction of coronary blood flow was eliminated by intravenous injections of aspirin that inhibited synthesis of endoperoxides, of benzydamine that inhibited synthesis of endoperoxides and TX A2, and of phenylbutazone that inhibited synthesis of PG E2, but was not of reduced glutathione that inhibited synthesis of TX A2 and accelerated synthesis of PG E2. In the preparations in which cyclical reduction of blood flow did not occur spontaneously, intracoronary injection of PG E2, but not of PG F2a, induced the cyclical reduction. The cyclical reduction was also induced by intravenous injections of epinephrine and reduced glutathione that accelerated synthesis of PG E2. The results indicate participation of PG E2 in the cyclical reduction of coronary blood flow.
Animals↗
Electrographic changes associated with cyclical reduction of coronary blood flow.
Electrographic changes associated with cyclical reduction of blood flow in partially constricted one or two coronary arteries of anesthetized dogs were examined. In the preparations with single vessel constriction, cyclical ST elevation occurred along with cyclical reduction of coronary blood flow below 25% of the control value. The ST elevation was associated with reciprocal ST depression in the contralateral ventricular surface. In the preparations with double vessel constriction, cyclical reduction of flow frequently occurred in both vessels. The reduction of flow in one vessel occurred not synchronously with that in another vessel in the majority of preparations. The reduction of flow in both vessels was associated with ST elevation in the corresponding areas of the left ventricle. Premature ventricular contractions frequently occurred at the beginning of or immediately after disappearance of ST elevation, or when ST elevation persisted for more than 10 min. Ventricular fibrillation frequently occurred in the preparations with double vessel constriction.
Angina Pectoris↗
Effects of anti-anginal agents on cyclical reductions of coronary blood flow.
The effects of coronary vasodilating agents and alpha- and beta-adrenergic blocking agents on cyclical reductions of blood flow in the partially constricted coronary artery of anesthetized dogs were examined. Intravenous injections of nitroglycerin (50 microgram/Kg), SG 75 (150 microgram/Kg), papaverine (1 mg/Kg), and nicotinic acid (10 mg/Kg) eliminated both cyclical reductions of flow and ST elevation (group 1). Nifedipine (10 microgram/Kg), verapamil (500 microgram/Kg), diltiazem (500 microgram/Kg), and propranolol (500 microgram/Kg) suppressed ST elevation, but they could not eliminate cyclical reductions of flow (group 2). Dipyridamole (1 mg/Kg) and phenotolamine (500 microgram/Kg) augmented both ST elevation and cyclical reductions of flow (group 3). The results indicate that ST elevation due to cyclical reductions of coronary blood flow was eliminated by spasmolytic actions of group 1 on coronary artery, was suppressed by negative chronotropic and/or inotropic actions of group 2, and was augmented by peripheral actions of group 3.
Adrenergic alpha-Antagonists↗
[Variant angina pectoris].
Explore the source record for details and available documents.
Angina Pectoris↗
Cyclical reduction in blood flow of partially constricted coronary artery in dogs. II. An arteriographic study.
Mechanisms for cyclical reduction in peripheral blood pressure and flow of partially constricted coronary artery of anesthetized dogs has been examined. In 64 of 97 preparations, cyclical reduction in coronary blood pressure and flow developed 3 to 32 min after the beginning of constriction. Period duration of the cyclical reduction ranged from 1 to 32 min. The cyclical reduction was frequently associated with elevation of the ST segment of surface electrocardiogram, systolic bulge of the left ventricle and excitation of afferent cardiac sympathetic nerve fibers. In the preparations in which cyclical reduction was not produced by constriction, a brief stretching of the constricted portion provoked the cyclical reduction. Segmental or diffuse narrowing of the constricted coronary artery which occurred during the reduction in pressure and flow was demonstrated by selective arteriography. Also, segmental spasm in the constricted coronary artery was demonstrated by photography. No obvious difference in the constricted of the artery was observed histologically between the preparations in which cyclical reduction developed and those in which cyclical reduction was not produced. The results indicate participation of vasospasm in the cyclical reduction of blood pressure and flow in partially constricted coronary artery.
Action Potentials↗
Instantaneous assessments of left ventricular dimensions by ultrasonic analogue conversion system. I. An experimental study.
A new time-to-voltage analogue converter of ultrasound echo was made. The converter samples the echoes from the septal endocardium and the endocardium of the posterior wall of the left ventricle. The converter also enables automatic calculates left ventricular minor axis, volume, and work. In fixed human hearts, the left ventricular minor axis and volume calculated by the converter were close to the actual ones. In anesthetized dogs, left ventricular minor axis, volume, ejection fraction and stroke work calculated by the converter were close to those calculated by cineventriculography. The results indicate applicability of the ultrasonic analogue converter for instantaneous assessments of left ventricular dimensions and function.
Analog-Digital Conversion↗
Cyclic fluctuations in coronary blood pressure and flow induced by coronary artery constriction.
Slow cyclic fluctuations were frequently observed in blood pressure of the distal portion of the partially constricted coronary artery of anesthetized dogs. Lowering the mean peripheral coronary blood pressure below 50% of the control value was required for initiation of fluctuations. Each fluctuation in pressure was composed of 2 phases; the phase of rise and phase of fall. Almost invariably, the phase of rise and phase of fall were accompanied by increase and decrease in coronary blood flow, respectively. When the mean peripheral coronary blood pressure fell below 20% of the control value during the phase of fall, systolic bulge and elevation of the ST segment of surface ventriculra electrocardiogram occurred. Period duration of each fluctuation ranged from 30 sec to 14 min. The cyclic fluctuations in pressure, flow, electrocardiogram and left ventricular wall motion were eliminated by nitroglycerin, but were not affected by phentolamine, propranolol, atropine, cervical vagotomy, and stellectomy.
Animals↗
Excitation of afferent cardiac sympathetic nerve fibers induced by vagal stimulation.
The effect of vagal stimulation on activity of afferent sympathetic nerve fibers from the dog's left ventricle has been examined. During partial constriction of the coronary artery, a brief electrical stimulation of the cervical vagus nerves resulted in a decrease in blood flow of the constricted artery, systolic bulge of the left ventricle, elevation of the ST segment of electrocardiogram and excitation of the afferent nerve fibers, which continued for up to 15 min. These changes were not produced without coronary artery constriction. Intravenous injection of phentolamine eliminated the decrease in blood flow, and suppressed systolic bulge, elevation of the ST segment and excitation of afferent fibers. Propranolol could not eliminate the decrease in blood flow while suppressed the other changes. Atropine eliminated all of these changes. The results indicate participation of adrenergic alpha-receptors in sustained decrease of coronary blood flow and excitation of afferent cardiac sympathetic nerve fibers which can be produced by a brief vagal excitation.
Action Potentials↗