Biomedical subjects
Publications and source records attributed to D Gattullo.
At the beginning of a 10 sec arterial haemorrhage, vascular elasticity induces an increase of mean diastolic coronary resistance. Then, the increase is counteracted by the relaxation of the vascular musculature, which causes a coronary hyperaemia when, after the haemorrhage is arrested, the vascular wall is stretched by a sudden though slight increase of blood pressure.
In five anaesthetized open-chest dogs, aortic blood pressure, cardiac output and coronary flow were recorded. After the barorecptor reflex activity was suppressed by clamping both common carotid arteries and cutting both vagi nerves, aortic blood pressure and mean coronary flow increased. Phasic coronary flow further decreased in systole and increased in diastole, whereas coronary vascular resistance fell only when the suppression of the baroreceptor reflex activity had caused an increase of the heart rate.
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In 10 anaesthetized open chest dogs, blood pressure, electrogram from the left auricular appendage or right atrium, peripheral ECG and cardiac output were recorded. Ventricular tachycardia was produced with aconitine and then suppressed by inducing atrial fibrillation or flutter-fibrillation either with aconitine or with electrical stimulation. After the capture of the ventricles by the supraventricular impulses, a haemodynamic improvement took place. This improvement is attributed to: I) beat to beat changes in the length of the cardiac cycles, whereby intermittent strong beats arise; II) restoration of the normal ventricular activation path and time course; III) the active contribution of properly timed atrial contractions, when present. The improvement was more evident when, after the capture, the ventricular rate was lower than during the ventricular tachycardia, because of a longer period available for the ventricular filling. It is believed that the reduction of the ventricular rate immediately after the capture is due to the suppression of the activity of the ventricular ectopic focus by the concealed conduction of high rate impulses coming from the atria.
In 10 urethan anaesthetized rabbits, VCG of acontine induced VT was studied. At the beginning of VT, both QRS and T loops arise and end regularly at the e point. Then, QRS loop opens and its end moves outside the E point, as a result of changes in ST segment. Later on, when ST segment disappears completely owing to an initial overlapping of the depolarization and repolarization processes, no arrest of the trace is observed between QRS and T loops. Lastly, immediately before the appearance of ventricular fibrillation, a progressive increase of the rate of VT above 400/min produces a fusion between the end of the T and the initial part ofn the next QRS loop. At this stage, no E point can be recognize. The results suggest that the transformation of VT into VF occurs through a delay and an overlapping of the depolarization-repolarization sequence.
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Intravenous injection of 0.125 mg/kg of venom of Bitis Gabonica in the anaesthetized dog produces an immediate but reversible decrease in total peripheral and coronary vascular resistance. Stroke volume show a transient increase followed by an irreversible reduction. A second dose of 0.25 mg/kg produces the same effect on total peripheral and coronary vascular resistance, but furtherly reduces the stroke volume. A third dose of 0.50 mg/kg kills the animal after an extreme reduction of the stroke volume. The progressive decrease of the stroke volume might be due to a failure of the ventricle to relax, whereas its transient increase immediately after the injection depends on the abrupt fall of the total peripheral resistance.
In the open-chest anesthetized dog, multiple arterial haemorrhage induces a reduction of the mean coronary flow, an absote or relative increase of the phasic flow during the early ventricular ejection phase and a decrease during the remaining phases of the cardiac cycle. When blood pressure falls sharply during the haemorrhage, coronary vascular resistance increases, whereas it does not change or decreases when blood pressure falls slowly. Moreover, coronary vascular resistance decreases transiently after the stoppage of the haemorrhage.
The study aimed at evaluating the reliability of a new type of aortic flow probes to be used in conscious dogs and easy to be removed without a second surgical intervention, 48-72 hours after they have been implanted. The probes, which have been made in the Department of Human Physiology of the University of Turin, are light and thin enough to be cronically implanted around the aorta without removing the fat which surrounds the artery, and to be taken away without injuring the tissues. The records obtained 24 and 48 hours after they have been positioned, demonstrate the reliability of the probes. Histological examination of the aorta has not evidenced any tissue reaction.
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