Nocturnal angina pectoris. Comparison between angina with ST segment elevation and depression documented by continuous orthogonal ECG recording

In 30 patients with nocturnal angina, the night-time ECGs were continuously recorded, and the time and duration of attack, cyclic character of attacks, the relation of chest pain to ischemic ECG changes and arrhythmias during attack were compared between 18 cases with ST elevation and 12 cases with ST depression during attack. In cases with ST elevation, 1) attacks occurred between 2:00 and 8:00 a.m., being most frequent between 4:00 and 5:00 a.m. 2) the duration of attack measured from the duration of ischemic ECG changes was less than 5 min in 88% of the attacks, 3) the attack often recurred with intervals less than 30 min and ECG changes were often unaccompanied bt chest pain, 4) the attack was complicated with various kinds of arrhythmias. These features were in marked contrast to the cases with ST depression, in which attacks were evenly distributed over the night-time, of longer duration, sporadic in occurrence and far less complicated with arrhythmias. These data suggest that the difference of mechanisms causing attacks between both groups.

Angiographic changes in the coronary artery associated with cyclical reductions of coronary blood pressure

Morphological changes associated with cyclical reductions of blood pressure in the partially constricted coronary artery of anesthetized dogs have been examined. In the constricted coronary segments, smooth and diffuse spasm, rosary-like spasm, a localized narrowing indicating a platelet aggregate or thrombus, and no obvious change were observed during the pressure reductions in 3, 5, 2 and 5 of 15 trials of 12 preparations, respectively. In the distal segments of the same preparations, segmental spasm and diffuse spasm were observed during the pressure reductions in 8 and one trials, respectively. The changes in the constricted and distal segments appeared simultaneously or independently. The change which indicates obstruction of the distal segments with platelet aggregates or thrombi was observed in none. The results indicate that spasm, but not platelet aggregates or thrombi, in the constricted segments and/or distal segments plays the major role in the cyclical reductions of blood pressure in the partially constricted coronary artery.

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.

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.

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.

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.

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.

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.

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.

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.