Effects of intravenous disopyramide on myocardial function in patients with different degrees of cardiac failure

The effects of intravenous disopyramide phosphate on myocardial function were evaluated by non-invasive indices of cardiac performance (systolic time intervals, STI) in 15 patients with atherosclerotic heart disease and different degrees of cardiac failure. Disopyramide (1.5 mg/Kg) was given intravenously over a period of 5 min. This drug induced in patients in I-II classes of NYHA a significant decrease of LVETc, while PEP, ICT, and PEP/LVET ratio rose significantly. STI were affected much more markedly in patients in III-IV classes of NYHA. Particularly affected were contractility indices (PEP, ICT, PEP/LVET), which were reduced significantly more in patients in III-IV classes as compares to patient in I-II classes. In contrast, LVETc, which correlates to stroke volume and cardiac output, was similarly worsened by the drug in the 2 groups of patients. Therefore, this study shows that disopyramide has relevant depressant effects on myocardial performance, simultaneously reducing stroke volume and contractility, and that the effect on contractility is more marked in patients with severe left ventricular impairment.

Protective effects of propranolol on the exercise-induced reduction of blood flow in arteriopathic patients

The vascular steal phenomenow, that is, the shunting of blood from ischemic to normally perfused areas, is commonly observed during exercise in the affected limbs of patients with peripheral arterial insufficiency. Propranolol was administered to 18 arteriopathic patients before the exercise to ascertain whether the reverse situation can be induced. The results indicate that before propranolol administration, Jantsch's index (used to quantify the plethysmographic waves) decreased from 0.53 +/- 0.05 to 0.33 +/- 0.04 (P less than 0.001) at 1 minute, and to 0.38 +/- 0.04 (P less than 0.001) at 5 minutes after the end of the exercise. When the exercise was repeated after propranolol, Jantsch's index did not change. These findings indicate that propranolol can inhibit exercise-induced vascular steal.

Effect of furosemide on plasma concentration and beta-blockade by propranolol

Although propranolol and furosemide are used together for hypertension, the effects of furosemide on plasma levels and beta-blocking action of propranolol are not known. Ten healthy subjects received propranolol 40 mg orally; the mean plasma propranolol levels in 60, 90, 180, and 300 min were 85 +/- 16, 90 +/- 7, 82 +/- 8, and 58 +/- 8 ng/ml. Propranolol was then given together with furosemide (25 mg orally) and the propranolol blood level was measured. Mean propranolol plasma levels were 106 +/- 11 ng/ml at 60 min, 120 +/- 12 ng/ml at 90 min (p less than 0.01), 102 +/- 8 ng/ml at 180 min (p less than 0.05), and 78 +/- 8 ng/ml at 300 min (p less than 0.01). Six additional subjects were given an infusion of 1 microgram/min isoproterenol increased by 0.5 microgram/min every 2 min until the heart rate rose by 25% after oral administration of furosemide 25 mg. This procedure was repeated after propranolol (40 mg orally) and propranolol with furosemide (25 mg orally). The amount of isoproterenol which raised the heart rate by 25% was 2.6 +/- 0.3 micrograms after furosemide alone and 17.7 +/- 2 micrograms after propranolol (p less than 0.01). After propranolol with furosemide the dose of isoproterenol required to elevate heart rate by 25% was 109 +/- 15 micrograms (p less than 0.001).

Automatic "scanning" by radiofrequency in the long-term electrical treatment of arrhythmias

The use of programmed electrical stimulation in the long term treatment of re-entry tachycardia offers encouraging perspectives. Among the others proposed, the "scanning" system seems to be the most effective. However, an implantable stimulator with these features is not yet available and, thus, a temporary external lead is required. These difficulties have been overcome by utilizing radiofrequency to synchronize and stimulate. An implantable device was therefore designed which is triggered by the patient and automatically searches the interruption zone of the tachycardia by exploring the R-R cycle. The external transmitter, which can produce one or two synchronized impulses, is programmed to scan the R-R cycle with progressive steps of 5 or 10 ms; when tachycardia is interrupted, further stimulation is inhibited. The implanted module connected to an endocavitary lead does not have any power supply and, therefore, is very small. The efficacy of this method has been demonstrated in 4 patients with supraventricular tachycardia (3 with WPW syndrome) resistant to conventional pharmacologic therapy.

Effects of propranolol in a case of orthostatic hypotension

In a hypertensive patient with orthostatic hypotension, the changes in several haemodynamic indices with respect to posture were evaluated. In the upright position, systemic blood pressure was reduced as compared with the supine position, and peripheral vasodilation was present, as shown by an increase in Jantsch's index of the impedance plethysmographic tracings. Systolic time intervals remained unchanged with changes in posture. Propranolol 10 mg intravenously brought the response to normal. In fact, after beta-blockade in the standing position the blood pressure remained unchanged and normal peripheral vasoconstriction was observed. Similar results were seen during atrial pacing at a constant heart rate of 130 beats/minute. In this patient, propranolol appears to normalise the response to the posture change, by restoring normal vasoconstriction in the upright position.

Correlation between systolic time intervals and roentgen findings in normal subjects and cardiopathic patients

This study was designed to evaluate the usefulness of non-invasive parameters in the follow-up of cardiopathic patients without valvular cardiac diseases. In 49 patients suffering from heart disease we have studied the changes of radiologic cardiac measurements and systolic time intervals (STI) in the 4 functional classes of the NYHA classification, investigating also the existence of any relationship between these different parameters. Only the patients in the 3rd and the 4th functional classes showed significant changes in STI and radiologic measurements, as compared with the control group. Moreover, significant negative correlations have been observed between relative heart volume and LVET (r = 0.69, P less than 0.001) and LVETc (r = 0.82, P less than 0.001) and positive correlations between relative heart volume and PEP (r = 0.59, P less than 0.01) and PEP/LVET ratio (r = 0.75, P less than 0.001). These results, while confirming the close correlation between STI and cardiac performance, seem to demonstrate that relative heart volumetry is a fairly accurate index of the cardiac conditions in non-valvular heart diseases.

[Permanent atrial paralysis]

A case is described of permanent atrial paralysis in a 68 year old female with diabetes and cirrhosis of the liver. Absence of electrical atrial activity was expected on the standard electrocardiogram, and confirmed by intracavitary electrophysiological investigation which showed the ineffectiveness of stimulation of both the right atrium and the coronary sinus. Recording of the His potentials showed that the resultant rhythm was of supra-ventricular origin. The absence of mechanical atrial activity was confirmed radiographically, on the jugular venogram, on the apexogram, and on the tracings of right atrial and pulmonary capillary pressure. A search was made for muscular or neuromuscular dystrophy which has often been found in association with this arrhythmia, but none was found. There may be an etio-pathological relationship between carbohydrate metabolism and atrial paralysis, as certain authors have suggested.

Relation between cholinergic and histaminergic components in reflex vasodilatation in the dog

Previous studies have shown that phentolamine is able to reverse the reflex vasodilatation produced by transitory baroreceptor stimulation by blocking sympathetic, histaminergic, and cholinergic components. A direct anticholinergic action of phentolamine has never been described; however, since it is known that this drug is capable of inhibiting histamine release during the reflex vasodilatation, it is possible that its ability to block the cholinergic component of the reflex is related to the latter property. Therefore, this study was undertaken in an attempt to identify possible relationships between cholinergic and histaminergic components of the reflex vasodilatation. Accordingly, in mongrel dogs the gracilis muscle was isolated and perfused and then loaded with 14C-labeled histamine. A transitory systemic hypertension was induced by intravenous injection of norepinephrine; this produced a reflex vasodilatation, shown by the fall in perfusion pressure, which was accompanied by an increase of histamine release from the muscle. Vagal block induced by atropine pretreatment reduced the fall in perfusion pressure induced by the systemic hypertension and produced a reduction of histamine release during the vasodilatation. In another group of animals a vasodilatation in the perfused muscle was induced by injection of acetylcholine. This response was accompanied by an increase in histamine release from the gracilis muscle. Alpha-receptor blockade, which has been shown to inhibit histamine release, reduced this acetyl-choline-induced vasodilatation. These results, while confirming the participation of the cholinergic system in the reflex vasodilatation elicited by transitory stimulation of the arterial baroreceptors, seem to demonstrate that this component is mediated almost exclusively by histamine release.

Reduction by cobra venom factor of myocardial necrosis after coronary artery occlusion

Components of the complement system are known to play an important role in the cytolytic process and in chemotaxis of leukocytes. Cobra venom factor specifically cleaves C3 activity via activation of the alternative (properdin) complement pathway. It does not act directly on C3. If C3 is involved in tissue necrosis after ischemic injury, cobra venom factor might reduce tissue damage after acute coronary occlusion. Accordingly, in 14 control dogs occlusion of the left anterior descending artery was carried out for 24 h. Epicardial electrograms were recorded 15 min after occlusion, and 24 h later transmural specimens for creatine phosphokinase activity (CPK) and for histological analysis were obtained from the same sites. In another 14 experimental dogs, 20 U/kg cobra venom factor was given intravenously 30 min after occlusion. Serum complement levels fell within 2-4 h to <20% of normal. In the control dogs, the relationship between ST-segment elevation and CPK activity 24 h later was: log CPK = -0.06 ST + 1.48 (n = 111 specimens, 14 dogs, r = 0.77). In the experimental dogs, log CPK = -0.024 ST + 1.46 (n = 111 specimens, 14 dogs, r = 0.60), showing significantly different slopes (P < 0.001), i.e., less CPK depression for any level of ST-segment elevation. Histologically, 69 of 71 sites (97%) with ST-segment elevation exceeding 2 mV in the control dogs showed signs of necrosis 24 h later, whereas in the experimental group only 43 of 79 sites (54%) with abnormal ST-segment elevations showed signs of necrosis (P < 0.0005). At the same time, it was shown that the administration of cobra venom factor did not alter cardiac performance, collateral blood flow to the ischemic myocardium or the clotting system, but infiltration of polymorphonuclear leukocytes into the myocardium was decreased. It is concluded that cobra venom factor, by reducing the amount of C3 and C5 substrate available for chemotactic factor generation, or other as yet undefined mechanisms, protects the ischemic myocardium from undergoing necrosis, as judged by histology and local CPK activity. Hence, a new approach to limiting the extent of myocardial infarcts after experimental coronary occlusion, based upon inhibition of complement-dependent inflammatory processes, is demonstrated.

Studies on the mechanism of reflex vasodilatation. The cholinergic component in the baroreceptorial reflex in the dog

This study was designed to investigate whether the cholinergic system is involved in the genesis of the reflex vasodilatation which follows the systemic hypertension induced by fast intravenous injection of norepinephrine in the dog. Accordingly, in 7 dogs the gracilis muscle was isolated and perfused and the reflex evoked. The analysis of the integrated areas of vasodilatation after atropine pretreatment showed a significant decrease of the reflex response in the perfused circulation. In fact, the mean value of the integrated areas of vasodilatation which was 66 +/- 8 mm Hg/min in the control condition, was reduced to 45 +/- 4 mm Hg/min after administration of atropine in the gracilis artery; meanwhile the integrated areas of systemic hypertension did not show any change. Phentolamine intra-arterial administration completely abolished the reflex. These results suggest the existence of a cholinergic component in the reflex vasodilatation induced by transitory baroreceptorial stimulation.

"Reverse coronary steal" induced by coronary vasoconstriction following coronary artery occlusion in dogs

The phenomenon of "coronary steal," i.e., the shunting of blood from ischemic to normally perfused areas of myocardium, has been described as an effect of the administration of several vasodilating agents. This study was performed to ascertain whether the reverse situation can be induced, i.e., whether vasoconstriction of the vessels supplying the nonischemic zone could increase the collateral flow to the ischemic area. In 16 open chest dogs, 15 and 30 min after occlusion of the left anterior descending coronary artery, epicardial electrograms were recorded and regional myocardial blood flow (RMBF) was measured with radiolabeled microspheres. Methoxamine was infused intravenously between 17 and 30 min, the mean arterial pressure being kept constant. The results indicate that while the coronary arterial flow to the normal myocardium fell from 90.6 +/- 4.3 to 77.7 +/- 3.2 ml/min/100 g (P less than 0.01), the collateral blood flow to the ischemic area increased from 21.4 +/- 3.5 to 41.0 +/- 4.2 ml/min/100 g (P less than 0.01), and thereby reduced acute myocardial ischemic injury. This favorable redistribution of blood flow might be considered a "reverse coronary steal."

Histamine mediation in muscular vasodilatation induced by beta adrenoceptor stimulation in dogs

This study was designed to investigate the possibility of a histamine mediation in muscular vasodilation induced by beta adrenoceptor stimulation. Accordingly, in seven dogs the effects of isoproterenol administration on the release of 14C-histamine from the perfused gracilis muscle were studied. Beta adrenoceptors stimulation induced a vasodilatation, as shown by a decrease in perfusion pressure(-43 +/- 12 mm Hg); simultaneously, a significant increase of the radioactivity measured in the venous blood effluent from the gracilis muscle was observed. Both these events were blocked by propranolol. In the other five dogs, chlorpheniramine was able to reduce the vasodilatation induced by the injection in the gracilis muscle of isoproterenol. Under control conditions, isoproterenol induced a fall in perfusion pressure of 44 +/- 5 mm Hg while, after chlorpheniramine, perfusion pressure decreased by only 24 +/- 4 mm Hg. The results of this study seem to confirm the possibility of a histamine mediation in isoproterenol-induced vasodilatation. However, further investigation is needed in order to identify the exact role of histamine in the geneis of this phenomenon.

Reduction of blood flow following ischemia in arteriopathic patients: reversion of the phenomenon induced by propranolol

In most arteriopathic patients, the release of a transitory ischemia in the affected limb reduces blood flow, instead of increasing it as in normal subjects. In this study the effects of propranolol administration on this paradoxical response have been investigated. After rheographic tracings were recorded in 14 arteriopathic patients in the basal condition and in the postischemic period, 10 mg of propranolol was administered IV and the protocol was then repeated. The blood flow in the affected area, measured as Jantsch's index of the rheographic tracings, was 0.63 +/- 0.04 in the basal condition and was reduced to 0.51 +/- 0.05 (P less than 0.001) in the postischemic period. When the ischemia was repeated after propranolol administration, Jantsch's index rose from 0.57 +/- 0.04 to 0.85 +/- 0.09 (P less than 0.01). The reversion of the paradoxical response to the ischemia induced by propranolol administration suggests that the beta-adrenergic blockade can increase blood flow to the ischemic area, probably through a constrictive action on arterovenous connections.

Favorable effects of hyaluronidase on electrocardiographic evidence of necrosis in patients with acute myocardial infarction

To evaluate hyaluronidase's effect in reducing post-infarction myocardial necrosis, we randomized 91 patients with anterior infarction to control (45) or to hyaluronidase-treatment (46) groups. A 35-lead precordial electrocardiogram was recorded on admission and seven days later. Hyaluronidase was administered intravenously after the first electrocardiogram and every six hours for 48 hours. QRS-complex changes were analyzed to assess the drug's effect. Precordial sites with ST-segment elevation (larger than or equal to 0.15 mV) on the initial electrocardiogram that retained an R wave were considered vulnerable for the development of electrocardiographic signs of necrosis. The sum of R-wave voltages of vulnerable sites fell more in the control group than in the hyaluronidase group (70.9 +/- 3.6 per cent [+/- 1 S.E.M.] vs 54.2 +/- 5.0 per cent P less than 0.01). Q waves appeared in 59.3 +/- 4.9 per cent of the vulnerable sites in control versus 46.4 +/- 4.9 per cent in hyaluronidase-treated patients (P less than 0.05). Thus, hyaluronidase reduced the frequency of electrocardiographic signs of myocardial necrosis.

Comparison between the effects of nitroprusside and nitroglycerin on ischemic injury during acute myocardial infarction

This clinical and experimental investigation was designed to delineate and compare the relative effects of sodium nitroprusside (NP) and nitroglycerin (TNG) on electrocardiographic ischemic injury following acute myocardial infarction in patients and following coronary artery occlusion in dogs. Accordingly, in ten patients with anterior acute myocardial infarction and ST-segment elevation stable for 60 min, the effects of NP (average 95 mug/min i.v.) and TNG (average 0.48 mg sublingually) were studied. The hemodynamic actions of NP and TNG were directionally similar. However, NP increased average ST-segment elevation (ST) by 2.0 +/- 0.2 mm, while TNG reduced ST by 1.4 +/- 0.4 mm. In order to clarify this disparity, coronary artery occlusions were carried out in 14 open-chest dogs. During control, NP and TNG time periods, epicardial electrograms were recorded and regional myocardial blood flow (RMBF) determined by the microsphere technique. Nitropruside increased ST-segment elevation from 4.6 +/- 0.6 to 5.7 +/- 0.6 mV (P less than 0.05) and reduced RMBF from 35 +/- 3 to 27 +/- 2 ml/min/100 g (P less than 0.01) in the ischemic zones. In contrast, TNG reduced ST-segment elevation from 4.9 +/- 0.7 to 3.0 +/- 0.7 mV (P less than 0.05), while increasing RMBF TO 43 +/0 4 ml/min/100 G (P less than 0.05) and the endo/epicardial ratio from 0.57 +/- 0.06 to 0.69 +/- 0.07 (P less than 0.01). Although TNG and NP exhibit similar hemodynamic effects, TNG reduced electrocardiographic ischemic injury, at least in part, by increasing perfusion of the ischemic areas and redistributing it favorably, while NP increased electrocardiographic ischemic injury, at least in part, by reducing perfusion. Therefore, TNG seems preferable to NP for reducing preload and afterload in patients during the early phase of acute myocardial infarction.

The cholinergic component in the reflex vasodilatation elicited by stimulation of the depressor nerves in the rabbit

1 The effects of the stimulation of the cephalic endings of the depressor nerve on the resistance in the perfused hindlimb were studied in the rabbit. 2 The vasodilatation thus elicited in the perfused hindlimb was reduced either by administration of guanethidine or by sympathectomy and abolished by subsequent treatment with atropine. 3 These data confirm the existence of two components in the genesis of the reflex vasodilatation: a passive component, due to the inhibition of sympathetic discharge, and an active component which in the rabbit is cholinergic in nature.

Participation of beta receptors in reflex vasodilatation in the dog

The effects of propranolol, given by direct intraarterial injection, on the reflex vasodilatation induced in the atropinized isolated gracilis muscle by rapid intravenous administration of norepinephrine, were studied in dogs. In these studies, both atropine and atropine plus propranolol did not significantly alter the maximum fall in vascular resistance in the perfused gracilis muscle following intravenous norepinephrine; however, if the reflex responses were evaluated as integrated areas of vasodilatation, atropine attenuated the vasodilatation and the administration of propranolol further attenuated the reflex. In fact, the value of the integrated areas of vasodilatation was 52.8 +/- 9 mmHg/min in the basal state, 39 +/- 6 mmHg/min after administration of atropine, and 24 +/- 7 mmHg/min after propranolol, whereas the integrated areas of the systemic hypertension did not show any modification. These results prompt us to conclude that the adrenergic beta receptors participate in the reflex vasodilatation, although the mechanism of their action needs further elucidation.

Studies on the hemodynamic changes induced by electrical stimulation of the vagosympathetic trunks in the dog

The effects of electrostimulation of the cephalic endings of the vago-sympathetic trunks on the systemic and perfusion pressure of the hind limb of the dog depend upon frequency, intensity and duration of the stimulus. The electrostimulation performed with stimuli of high frequency, low intensity and moderately long duration (rectangular waves of 1.5 V, 0.7 msec, 100 Hz) consistently elicited systemic hypertension and vasoconstriction. This response was completely abolished by pretreatment with guanethidine or hexamethonium. On the other hand, electrostimulation with stimuli of low frequency, high intensity and long duration (5 V, 1 msec, 10 Hz) produced systemic hypotension and vasodilatation in the perfused hind limb. These effects were completely blocked by atropine or hexamethonium, while guanethidine was unable to induce any modification. These findings suggest that electrostimulation of vagosympathetic trunks can evoke different hemodynamic responses depending upon the characteristics of the stimulus. The occurrence of a vasodilatation specifically blocked by atropine demonstrates that a purely cholinergic mechanism underlies such a reflex response.

Studies on the nature of the vasodilator fibers running in the lumbar sympathetic chain of the dog

These experiments were performed to further elucidate the nature of the vasodilator fibers running in the sympathetic chain in the dog. The electrostimulation of the lumbar sympathetic trunk caused vasoconstriction in the perfused hind limb which inverted to vasodilatation after guanethidine was administered. This vasodilator response is mediated by cholinergic fibers since it was completely abolished by atropine. The observation, furthermore, that hexamethonium completely nullified both vasodilator and vasoconstrictor responses to the electrostimulation of the sympathetic chain indicates that both vasoconstrictor and vasodilator fibers, which are activated during the stimulation of the sympathetic chain, are preganglionic in nature.