Coronary haemodynamic effects of short-term intravenous administration of gallopamil in patients with stable exertional angina

The effects of short term intravenous administration of gallopamil on coronary haemodynamic variables were studied in 10 patients with stable exertional angina and angiographically confirmed coronary artery disease that affected the proximal portion of the left anterior descending artery. Blood flow in the great cardiac vein was measured by a thermodilution technique, both at rest and during ischaemia induced by atrial pacing, before and after intravenous administration of gallopamil (0.02 mg/kg as a bolus dose given over three minutes, followed by an infusion of 0.0005 mg/kg/min). Gallopamil significantly prolonged the mean (SD) duration of pacing that was tolerated (11 (2.6) vs 14.8 (2.4] min, significantly increased the mean (SD) peak heart rate attained during pacing (142 (15) vs 158 (11) beats/min), and reduced mean (SD) arterial pressure (133 (17) vs 116 (17) mm Hg). There were no changes in mean (SD) blood flow in the great cardiac vein (134.1 (57) vs 112.9 (38) ml/min, mean (SD) anterior regional coronary resistance (1.18 (0.6) vs 1.15 (0.5) mm Hg/ml/min), and mean (SD) anterior regional myocardial oxygen consumption (16.6 (6) vs 13.7 (4) ml/min). These data confirm that gallopamil is an effective antianginal agent and suggest that a reduction of myocardial oxygen demand is the predominant mechanism by which the drug exerts its beneficial effects.

Effects of diltiazem on regional coronary hemodynamics during atrial pacing in patients with stable exertional angina: implications for mechanism of action

To investigate the mechanism of the antianginal action of diltiazem in stress-induced myocardial ischemia, we studied 12 patients with stable exertional angina and disease of the proximal left anterior descending artery by measuring great cardiac vein flow (GVCF) and calculating anterior regional coronary resistance (ARCR) during myocardial ischemia induced by atrial pacing before and after intravenous administration of diltiazem (0.25 mg/kg in a bolus dose followed by continuous infusion of 0.005 mg/kg/min). Diltiazem increased the pacing time to angina from 6.9 +/- 3.5 to 10.7 +/- 4 min (p less than .001). At peak pacing heart rate was increased after diltiazem (from 128 +/- 17 to 145 +/- 17 beats/min, p less than .005), while mean arterial pressure was decreased (from 131 +/- 19 to 113 +/- 17 mm Hg, p less than .025), leaving the double product unaltered. At peak pacing no changes were observed in GCVF (from 115 +/- 46 to 119 +/- 46 ml/min, p = NS), ARCR (from 1.3 +/- 0.4 to 1.1 +/- 0.4 mm Hg/ml/min), or myocardial oxygen consumption of the anterior region (from 14.5 +/- 4.2 to 13.4 +/- 4.7 ml/min). Reduction of myocardial oxygen demand plays a major role in the antianginal action of diltiazem in patients with stress-induced myocardial ischemia.

[Bioavailability of a delayed-action aminophylline preparation]

Absorption of theophylline from one commercial product labelled as aminophylline sustained release was compared to the absorption from an oral solution of aminophylline in a single-dose bioavailability study. Aminomal-R tablets had bioavailability (101.2 +/- 19) statistically indistinguishable from that of the standard but showed significantly slower absorption (peak times of 3.6 +/- 1.1 h vs 1.3 +/- 0.8 h) and lower peak plasma concentrations (16.8 +/- 4.7 mg/l/1 g aminoph. dose vs 21.1 +/- 4.2 mg/l/1 g aminoph. dose). Projections of plasma concentrations upon multiple dosing were made from single dose data: the dosage interval (every 12 h) concentration ratio which reflects both the frequency of dosing and the entry of the drug into and removal from the body was of 1.8 vs 3.1.

Value of Doppler multi-level segmental pressure index in the diagnosis and hemodynamic characterization of totally occlusive aorto-iliac-femoro-popliteal lesions

Four-level lower limb Doppler S.P.I. (upper thigh; above knee; below knee; above ankle) were evaluated in 275 limbs, 110 of which showed totally occlusive lesions at one or more levels of the aorto-iliac-femoro-popliteal axis on angiographic examination, 65 showed stenosis less than 50% (sclerotic controls) and 100 did not undergo arteriographic examination since they apparently had no lesions (healthy controls). Analysis of the results-carried out using the Student's t statistical method-showed a drop in the S.P.I. close to or over 0.30 between two adjacent levels and was indicative of the presence of an occlusion in the intermediate area. This method therefore allowed the presence and the position of an isolated lesion to be detected. In the case of multiple lesions in series, the proximal one is detected with certainty, whereas the more distal ones can be recognized but not their exact position and extension. Multiple lesions in series are more hemodynamically significant than isolated ones, and proximal lesions more than distal ones.

[Influence of administration of pyridoxine on circadian rhythm of plasma ACTH, cortisol prolactin and somatotropin in normal subjects]

The influence of vitamin B6 in a dosage of 300 mg X 2 in 24 hrs, on circadian rhythm of plasmatic ACTH, cortisol, prolactin and somatotropin have been studied in 10 normal women. After vitamin B6 24 hrs pattern of ACTH and cortisol is unchanged; prolactin levels are slightly lower, in a statistically unsignificant proportion the night peak of growth hormone is higher in a statistically significant proportion (p. 0.05). The effect of vitamin B6 is likely to me mediated by dopaminergic receptors at hypothalamic level as previous studies by other Authors appear to prove.

The management of impending myocardial infarction using coronary artery by-pass grafting and an intra-aortic balloon pump

Of 33 patients with impending myocardial infarction 25 were treated using a combination of coronary artery by-pass grafting and intra-aortic balloon pumping. Eight patients were treated with coronary artery by-pass grafting alone. Twenty-two of the 25 patients who were treated with the combined technique made a full recovery. Three patients sustained definite myocardial infarctions and one of these died. Five of the 8 patients treated by grafting alone suffered infarction and of these 3 died. The value of intra-aortic balloon pumping in combination with coronary artery by-pass grafting in the management of impending myocardial infarction is discussed.

The effect of varying tidal volume on the associated phrenic motoneurone output:studies of vagal and chemical feedback

Two groups of dogs were anaesthetised, paralysed and artificially ventilated using a respirator driven by the phrenic motoneurone output, electrically processed to resemble transpulmonary pressure. In one group, blood gases were maintained constant with closed-chest cardiopulmonary bypass; the second group were studied without "bypass". Therefore it was possible to determine the relative contributions of vagal and chemial feedback to the effect of altering the depth of an inspiration on the associated phrenic motoneurone output. Mono-exponential regressions between change of respirator gain and changes in both inspiratory time and peak amplitude of the processed phrenic signal were found for all dogs. The rate of rise of the processed phrenic signal usually changed in the direction of the change in respirator gain, suggesting the presence of vagal positive feedback during eupnoeic breathing. After vagotomy, all responses were absent in the "bypass" group and small in the "non-bypass" group. These experiments quantitate the role of pulmonary vagal afferent discharge, in phase with inspiration, in the regulation of phrenic motoneurone output in a closed-loop situation.

The effect of carbon dioxide in the airways and alveoli on ventilation; a vagal reflex studied in the dog

1. The inhalation of CO(2) produces a tachypnoea only in the presence of intact vagus nerves; the present study was designed to examine the mechanism of this phenomenon in the dog.2. Closed-chest cardiopulmonary bypass was established in dogs weighing 16-24 kg, anaesthetized with chloralose. When the ;bypass' was established pulmonary blood flow ceased, P(A, CO2) was reduced and the respiratory rate slowed. 3-10% CO(2) in O(2) could then be inhaled without change in the level of P(a, CO2) set at the oxygenator.3. The addition of CO(2) in these concentrations to the inspired oxygen resulted in an increase in respiratory frequency, maximal at the first breath and sustained for the 1 min period of exposure. The increase in respiratory frequency was due to a shortening of expiratory duration. Inspiratory duration did not change. The response was absent after vagotomy.4. Inert gases in O(2), given as a control, had no effect on breathing.5. The effect of raising P(a, CO2) (by increasing the concentration of CO(2) in the gas equilibrating the blood in the oxygenator), was primarily to increase tidal volume.6. The ventilatory effect of inspiring CO(2)/O(2) mixtures was shown to be additive to the effect of raising P(a, CO2).7. These experiments show that an afferent vagal reflex originating from the lungs causes tachypnoea, when a dog, on ;bypass', inhales low concentrations of CO(2) in O(2).

Studies of the pulmonary vagal control of central respiratory rhythm in the absence of breathing movements

1. Breuer's hypothesis that the vagus nerves exert a tonic control of respiratory rhythm, in addition to the phasic control, was examined.2. Closed-chest cardiopulmonary bypass was instituted in dogs weighing 20-30 kg anaesthetized with chloralose. Respiratory rhythm was recorded from a phrenic electroneurogram.3. Complete muscular paralysis induced with gallamine triethiodide produced an increase in the duration of inspiration and an increase in the amplitude of the integrated phrenic electroneurogram. There was no consistent effect on expiratory duration. Gallamine produced no effect when given after vagotomy.4. In the paralysed state, an increase in lung volume of 25-100 ml. for 30-60 sec produced a sustained increase in the duration of expiration and a decrease of respiratory rate: there was little effect on inspiratory duration, or the amplitude of the integrated phrenic electroneurogram.5. A decrease in lung volume of the same order of magnitude for the same period produced a sustained decrease in the duration of expiration and an increase of respiratory rate: there was little effect on inspiratory duration or the amplitude of the integrated phrenic electroneurogram.6. The phenomena described in (5) and (6) constitute a high gain respiratory frequency controller. They did not occur after bilateral cervical vagotomy.7. Bilateral cervical vagotomy during complete muscular paralysis produced a further increase in the duration of inspiration and in the amplitude of the integrated phrenic electroneurogram; there was no consistent effect on expiratory duration.8. The results confirmed Breuer's hypothesis and showed that inspiratory duration and expiratory duration are controlled independently.