PROPRANOLOL (INDERAL) IN DISTURBANCES OF CARDIAC RHYTHM

Historical Aspects of the Use of Antiarrhythmic Drugs in Clinical Practice

Heart rhythm disorders are one of the most urgent problems in cardiology. The first reports on the possibility of using drugs in the treatment of cardiac arrhythmias began to appear in the scientific literature from the middle of the 18th century. This pharmacotherapeutic direction has been developed since the second half of the 20th century, when new antiarrhythmic drugs began to be used in clinical practice. The introduction of new drugs and modern methods of treating arrhythmias into clinical practice has significantly improved the prognosis and quality of life of patients. Combination antiarrhythmic therapy, including antiarrhythmic drugs and radiofrequency ablation, seems to be the most promising and successful tactic for treating patients in the future. A historical review of the literature on the clinical use of antiarrhythmic drugs both in past years and at present is presented in the article.

Esmolol versus verapamil in the acute treatment of atrial fibrillation or atrial flutter

The effects of esmolol, an ultrashort-acting beta blocker, and verapamil were compared in controlling ventricular response in 45 patients with atrial fibrillation or atrial flutter, in a randomized, parallel, open-label study. Patients with either new onset (less than 48 hours, n = 31) or old onset (greater than 48 hours, n = 14) of atrial fibrillation or flutter with rapid ventricular rate were stratified to receive esmolol (n = 21) or verapamil (n = 24). Drug efficacy was measured by ventricular rate reduction and conversion to sinus rhythm. The heart rate declined with esmolol from 139 to 100 beats/min (p less than 0.001) and with verapamil from 142 to 97 beats/min (p less than 0.001). Fifty percent of esmolol-treated patients with new onset of arrhythmias converted to sinus rhythm, whereas only 12% of those who received verapamil converted (p less than 0.03). Mild hypotension was observed in both treatment groups. Esmolol compares favorably with verapamil with respect to both efficacy and safety in acutely decreasing ventricular response during atrial fibrillation or flutter. Moreover, conversion to sinus rhythm is significantly more likely with esmolol.

Use of beta-adrenoceptor blocking drugs in hyperthyroidism

There is an increasing use and variety of beta-adrenoceptor blocking agents (beta-blockers) available for the treatment of hyperthyroidism. Recent comparative studies suggest that atenolol (200mg daily), metoprolol (200mg daily); acebutolol (400mg daily), oxprenolol ( 160mg daily), nadolol ( 80mg daily) and timolol (20mg daily) produce a beneficial clinical response equal to that seen with propranolol ( 160mg daily). Most beta-blockers reduce resting heart rate by approximately 25 to 30 beats/min, although a lesser reduction is seen with those possessing intrinsic sympathomimetic activity such as oxprenolol and pindolol. While earlier studies employing large doses of intravenous propranolol concluded that beta-blockade reduced myocardial contractility, more recent non-invasive studies suggest that the predominant cardiac effect is on heart rate. In patients with cardiac failure, beta-blockers may, however, produce a profound fall in cardiac output. Nevertheless, in combination with digoxin they may be useful in controlling the atrial fibrillation of thyrocardiac disease. beta-Blockers improve nervousness and tremor (although to a lesser extent with cardioselective agents) and severe myopathy, and they also reduce the frequency of paralysis in patients with thyrotoxic periodic paralysis. There is often subjective improvement in sweating but usually no major effect on eye signs. Recent studies show a 10% reduction in oxygen consumption/basal metabolic rate with long term oral use of selective or nonselective beta-blockers. In addition, many agents (propranolol, metoprolol, nadolol and sotalol but not acebutolol, atenolol or oxprenolol) reduce circulating tri-iodothyronine (T3) concentration by between 10 and 40%, although the clinical significance of this effect (if any) is not established. beta-Blockers may also have endocrinological effects on gastrin, cyclic AMP, catecholamines and other hormone levels. Given in adequate dosage, propranolol has been shown to control thyrotoxic hypercalcaemia. Minor side effects (nausea, headaches, tiredness, etc.) are quite common but overall beta-blockers are well tolerated by the thyrotoxic patient. The major use of these drugs is in symptomatic control while awaiting definitive diagnosis or treatment. As an adjunct to antithyroid drugs or radioactive iodine, beta-blockers will produce a satisfactory clinical response in the weeks to months before these forms of therapy produce a euthyroid state. beta-Blockers are more convenient than antithyroid drugs in the control of patients receiving therapeutic radioiodine, in that continuous therapy and assessment of biochemical response is possible.(ABSTRACT TRUNCATED AT 400 WORDS)

Beta-adrenoceptor blockade and anaesthesia for thyroidectomy

The administration of beta-adrenoceptor blocking drugs in the pre-operative preparation and operative management of thyrotoxic patients undergoing subtotal thyroidectomy is reviewed. Particular reference is made to some of the recent advances and it is emphasised that there has been a considerable reduction in the incidence of problems following judicious use of these drugs. The choice of anaesthetic technique employed for thyroidectomy is less important than the degree of control of thyrotoxicosis by the beta-adrenoceptor blocking drug. Propranolol has proved safe and effective for the majority of patients. The longer acting agent nadolol is easier to administer, particularly in the peri-operative period. Patients are rendered less thyrotoxic and safety thereby enhanced by adding potassium iodide for 10 days preoperatively. The combination of nadolol and potassium iodide offers real advantages in the preparation of the thyrotoxic patient for surgery.

Potential organ- or tumor-imaging agents XIX: radioiodinated antiarrhythmic drugs as potential myocardial imaging agents

Iodinated and radioiodinated analogs of propranolol and N,N-dimethylpropranolol were synthesized wherein an iodophenyl moiety replaced the naphthalene ring of the parent drug. These new compounds were evaluated not only for their beta-adrenergic blocking and antiarrhythmic activities but also for their ability to accumulate selectively in myocardial tissue. Like propranol, the iodinated analogs displayed comparable beta-blocking and antiarrhythmic activity, and the order of potency was ortho- > meta- > para-iodophenyl. Quaternization of propranolol and the iodinated analogs eliminated the beta-adrenergic blocking activity but retained the antiarrhythmic property of the secondary amine precursors. Among the quaternary salts, the antiarrhythmic potency was meta- > ortho- > para-iodophenyl. Tissue distribution of the radioiodinated derivatives revealed that only the quaternary derivatives were selectively accumulated in myocardial tissue. These results demonstrate that an iodophenyl ring can substitute for th naphthalene ring in propranolol and its quaternary salt without significant alteration of pharmacological properties. The radioiodinated quaternary derivatives may be useful pharmacological tools in experiments aimed at relating antiarrhythmic activity to myocardial uptake.

Inefficacy of digitalis in the control of heart rate in patients with chronic atrial fibrillation: beneficial effect of an added beta adrenergic blocking agent

The role of digoxin and the new beta adrenergic blocking agent, timolol, in controlling heart rate at rest and during exercise was investigated in 28 patients with chronic atrial fibrillation. Digoxin failed to prevent excessively rapid heart rates during mild to moderate exercise. Increasing digoxin blood levels from a mean of 0.6 to 1.8 ng/ml had no effect on heart rate either at rest or during exercise. The addition of timolol, 20 to 30 mg/day, resulted in a satisfactory and significant attenuation of the rapid heart rates both at rest and during exercise. Heart rates at rest were 91 and 98 beats/min in the patients with low and high digoxin dosage and rose to 135 and 139 beats/min, respectively, during exercise. Timolol reduced the heart rate to 67 at rest and to 92 beats/min during exercise. The effect of beta adrenergic blockade at rest was less pronounced in patients whose initial heart rates were below 90 beats/min. Digoxin alone may not suffice to control excessive heart rate in patients with chronic atrial fibrillation. The additional beta adrenergic blockade actually normalizes the heart rate response in these patients.

Hemodynamic response to exercise after propranolol in patients with mitral stenosis

Hemodynamic response to exercise before and 10 minutes after propranolol (5 mg intravenously) was studied in 10 young patients with pure mitral stenosis who had normal sinus rhythm and no cardiac failure. After propranolol the mean heart rate and cardiac index at rest were lower than during the control state (respectively, 95 +/- 4 versus 82 +/- 3 beats/min, P less than 0.005; 3.4 +/- 0.2 versus 2.8 +/- 0.1 liters/min per m2, P less than 0.025). As a result, the mean pulmonary wedge pressure and mean mitral valve gradient at rest were lower (respectively, 22 +/- 2 versus 18 +/- 2 mm Hg, P less than 0.005; 24 +/- 2 versus 17 +/- 2 mm Hg, P less than 0.001). During exercise after propranolol the values of pulmonary wedge pressure and mitral valve gradient were lower than control values during exercise (respectively, 39 +/- 3 versus 30 +/- 2 mm Hg, P less than 0.005; 44 +/- 3 versus 32 +/- 3 mm Hg, P less than 0.005), again because of the lower heart rate and cardiac index (130 +/- 6 versus 104 +/- 6 beats/min, P less than 0.001; 4.6 +/- 3 versus 3.7 +/- 2 liters/min per m2, P less than 0.01). Left ventricular end-diastolic pressure and stroke index showed no significant changes. Thus, propranolol may benefit patients with pure mitral stenosis with sinus rhythm and no cardiac failure whose symptoms occur during those reversible conditions characterized by an increase in heart rate or cardiac output, or both.

Effective treatment of supraventricular arrhythmias with acebutolol

To evaluate the antiarrhythmic efficacy of the new beta adrenergic blocking agent acebutolol, 15 monitored patients with supraventricular arrhythmias received, in double-blind fashion, an intravenous infusion of either acebutolol or saline solution after a control period. Patients treated with saline solution demonstrated no change (P greater than 0.05) in heart rate or arterial blood pressure or conversion to sinus rhythm. After administration of acebutolol, significant (P less than 0.05) reductions in heart rate were noted at 5 minutes. Peak reduction occurred at 10 to 30 minutes and correlated with maximal acebutolol plasma concentrations, antiarrhythmic activity persisted for 24 hours. Mild reductions in systolic blood pressure were observed in the majority of patients. Two patients with atrial fibrillation and one with multifocal atrial tachycardia had conversion to sinus rhythm. Frequent premature atrial complexes noted in one patient were greatly suppressed after administration of the drug. In the nine patients with clinical evidence of chronic obstructive lung disease acebutolol was well tolerated. Adverse reactions were limited to transient dyspnea in one patient with prior heart failure and a decrease in systolic blood pressure to less than 90 mm Hg in three patients who remained asymptomatic. In the patients studied, acebutolol was an effective agent for the treatment of supraventricular arrhythmias and appeared to be of special value in those with chronic obstructive lung disease.

Clinical electrophysiological effects of propranolol on normal sinus node function

In 35 patients aged 18 to 69 years (mean 48) with clinical, electrocardiographic, or electrophysiological evidence of normal sinus node function, the effect of intravenous propranolol (0.1 mg/kg) was assessed on 3 indices of sinus node function. The drug significantly prolonged sinus node cycle length (12%), slightly prolonged the corrected sinus node recovery time (15%), and slightly but insignificantly lengthened sinuatrial conduction time. Propranolol may be administered safely in patients with normal sinus node function without the fear of producing severe sinus bradycardia, sinuatrial block, sinuatrial pauses, or prolonged sinus asystole, after spontaneous or stimulation-induced conversion of a tachycardia.

A study of the effectiveness of propranolol in menopausal hot flushes

A prospective, double-blind, randomized comparison of propranolol, 40 mg three times daily, and matching placebo showed propranolol to be no more effective than placebo in controlling hot flushes in a group of 25 perimenopausal women. Other menopausal symptoms, such as insomnia and palpitations, were equally unaffected. However, a very close correlation was found between the daily atmospheric temperature and the number of flushes occurring in the group.

Comparative studies on the pharmacological actions of antiarrhythmic drugs in isolated rate papillary muscle

1. The effects of ajmaline, cocaine, phenytoin, lignocaine, procainamide, propranolol, quinidine and trimetazidine on the contractility and the refractory period of isolated rat papillary muscles were compared. 2. At the higher concentrations used, all drugs suppressed the contractile tension of the rat papillary muscles. 3. The effects of these drugs on the refractory period were compared at concentrations at which the contractile tension was suppressed by 30% of the control. At this point, lignocaine, procainamide, ajmaline and quinidine prolonged the refractory period more than two-fold while the effects of propranolol and phenytoin were slight, cocaine and trimetazidine had little or no effect.

Antiarrhythmic properties of 5-(3-tert-butylamino-2-hydroxy)propoxy-3,4-dihydrocarbostyril hydrochloride (OPC-1085), a newly synthesized, potent beta-adrenoreceptor antagonist

1. The antiarrhythmic properties of 5-(3-tert-butylamino-2-hydroxy)propoxy-3,4-dihydrocarbostyril hydrochloride (opc-1085) were compared with those of propranolol and pindolol using various kinds of preparations for experimental arrhythmia in dogs. 2. Although OPC-1085 was the most potent drug to antagonize adrenaline-induced arrhythmia in animals anaesthetized with either pentobarbitone sodium or halothane, it was scarcely effective on ouabain-induced arrhythmia in pentobarbitone sodium anaesthetized animals. 3. When these compounds were administered intravenously to conscious dogs 24 h after two-stage ligation of the anterior descending artery, ectopic ventricular beats of coronary ligation-induced arrhythmia were reduced while regular sinus beats were simultaneously increased. 4. OPC-1085 was very effective on aconitine-induced arrhythmia in dogs anaesthetized with pentobarbitone sodium. The effective dose was similar to that of propranolol but about fifteen times less than that of pindolol. 5. It is concluded that different potencies among these beta-adrenoreceptor antagonists against various kinds of experimental arrhythmias cannot be simply deduced from any one of the following properties; beta-adrenoreceptor antagonism, intrinsic myocardial stimulation, local anaesthetic and so-called quinidine-like effects.

Sclerosing peritonitis due to practolol: a report on 9 cases and their surgical management

Nine patients with an unusual and serious intraabdominal complication of the beta-adrenergic blocking agent practolol seen since 1973 are reported. The striking and bizarre peritoneal changes induced by the drug have distinctive features that are not shown by other forms of peritoneal disease. The cases presented with small bowel obstruction, usually chronic in type and often associated with profound weight loss and an abdominal mass. Characteristic radiological features were present. The abnormalities at laparotomy were impressive, with a gross proliferation of the visceral peritoneum which formed a dense white cocoon which encased, constricted and markedly shortened the small bowel, usually from the duodenojejunal flexure to the ileocaecal valve. The obstruction was relieved by mobilizing the small bowel from the ensheathing tissue. Restoration of alimentary function after surgery was delayed but the long term result was satisfactory with full relief of symptoms and the absence of recurrent obstruction during the follow-up period. This complication may arise after treatment with the drug has been stopped, and although long term oral therapy has been discontinued, further cases will almost certainly present for some time to come.

Whither thyrotoxicosis?

For 30 years the thyrotoxic patient has been subjected to a plurality of treatments by surgery, radio-iodine and long term anti-thyroid drugs. These therapies have been accepted as complementary to the needs of the individual patient, without regard for long term results or the economic situation as it affects both patient and hospital services. In the context of surgical treatment which is now available, it is suggested that the advantages of operation over other therapies presage a reversion to surgery as the treatment of choice.

The surgical management of thyrotoxicosis

Preparation of selected thyrotoxic patients for partial thyroidectomy can be safely and quickly achieved using propranolol, the duration of preoperative therapy and the number of out-patient attendances being reduced by over 50 per cent. No problems have been encountered during preparation or intra-operatively in patients pretreated with propranolol when compared with patients pretreated with conventional preparations. The commonest form of morbidity following destructive therapy for thyrotoxicosis is hypothyroidism. In surgically treated patients hypothyroidism can be defined within 1 year of operation. The factors influencing postoperative hypothyroidism are discussed.

Adrenergic influences on the distal Purkinje system of the canine heart

The purpose of these experiments was to examine the effects of norepinephrine and propranolol on distal Purkinje fibers of the canine heart. Previous studies have indicated that action potential duration is normally greatest in distal Purkinje fibers 3-4 mm from the Purkinje-muscle junction. In such preparations, premature beats initiated either proximal or distal to the area of maximal action potential duration may propagate with delay or block. Our experiments were performed on the right bundle branch and the distal Purkinje fibers of dog hearts and used standard microelectrode techniques. Premature beats with a coupling interval comparable to the duration of action potentials at the area of maximal duration were conducted with delay. Earlier beats were confined to fibers proximal to the area of maximal action potential duration. Norepinephrine (1 x 10 -5 M ) increased action potential duration in some fibers, consistently prolonged the functional refractory period of distal Purkinje fibers, and produced a marked delay in the propagation of early premature beats. Propranolol (0.25-1.0 mg/liter) shortened action potential duration, shortened the functional refractory period of distal fibers, and reduced or abolished conduction delay and block of early premature beats. These observations suggest that the unique properties of the Purkinje-muscle junction may contribute to the genesis of arrhythmias and that this region is an important site of action of propranolol. The action of propranolol on the Purkinje-muscle junction was dose dependent.

Comparison of propranolol and LB 46 (prinodolol) on hyperthyroid tachycardia

LB 46 (prinodolol) a β-adrenergic receptor blocking drug which is more potent than propranolol in euthyroid subjects, is less effective in inhibiting hyperthyroid tachycardia. This is probably due to its intrinsic sympathomimetic activity.

Effects of (plus or minus)-propranolol, (plus or minus)-,(plus)-, and (minus)-alprenolol on unanaesthetized dogs with ventricular arrhythmias resulting from coronary artery ligation

1. The effects of (+/-)-propranolol, (+/-)-, (+)- and (-)-alprenolol were studied in unanaesthetized dogs with ventricular arrhythmias produced by ligation of the left coronary artery. The responses were compared with those of similar control dogs which were given only isotonic saline.2. The ventricular arrhythmias were abolished by cumulative doses of 3.5 mg/kg of (+/-)-alprenolol, 7.5 mg/kg of (-)-alprenolol and (+/-)-propranolol and by 15.5 mg/kg of (+)-alprenolol.3. At the time of maximum antiarrhythmic activity none of the drugs produced significant alterations in mean arterial pressure or atrial rate.4. Cumulative doses of 7.5 mg/kg and 15.5 mg/kg of the four drugs resulted in some instances of lip licking, emesis and/or head tremors while 31.5 mg/kg was invariably lethal.5. Since the beta-adrenoceptor blocking activity of (-)-alprenolol is 100 times greater than that of (+)-alprenolol, suppression of these ventricular arrhythmias was apparently unrelated to antagonism of sympathetic influences.6. Alprenolol and propranolol have myocardial depressant properties apart from their effects on beta-adrenoceptors which could account for the anti-arrhythmic activity observed.

The effects of propranolol on cardiac conduction

The effects of propranolol, 0.1 mg/kg given intravenously, on atrioventricular (A-V) conduction and intraventricular (IV) conduction were studied in eight patients. Atrial pacing was used to control the heart rate. His bundle electrograms were recorded, and the interval from the pacing impulse to the His bundle electrogram (P-H interval) was used as a measure of A-V conduction and the interval from the His bundle electrogram to the S wave (H-S interval) was used as a measure of intraventricular conduction. Propranolol significantly prolonged the P-H interval in every patient at all paced heart rates, and it had no effect on the H-S interval. In two patients propranolol prolonged the effective refractory period of the atrioventricular conducting tissue.

In four dogs during His bundle pacing, propranolol (4 mg/kg iv) had no effect on intraventricular conduction as measured from the His bundle pacing spike to S wave (H-S interval). In two dogs with prolonged H-S intervals secondary to toxic doses of digitalis and procainamide, propranolol had no effect on IV conduction. It is concluded that propranolol prolongs A-V conduction and has no effect on IV conduction when administered to patients in clinically effective dosages. Propranolol's effects on cardiac conduction can be explained on the basis of its capacity to produce beta-adrenergic blockade.

Effect of propranolol on exercise tolerance of patients with atrial fibrillation

Six patients with atrial fibrillation who were taking digitalis were exercised before and after 30 mg. of propranolol twice daily. Though there was a lower pulse rate at rest and on exercise in all patients, three suffered deterioration of exercise tolerance. It is concluded that propranolol does not improve the exercise tolerance of patients with atrial fibrillation whose resting ventricular rate is controlled with digitalis.

An adrenergic neuron blocking action of propranolol in isolated tissues

Propranolol was tested for adrenergic neuron blocking activity in three isolated sympathetically-innervated smooth muscle preparations; the rat vas deferens, rabbit ileum and rabbit ear artery. In each preparation propranolol impaired the responses to sympathetic stimulation without reducing the responses to added noradrenaline. This blocking action of propranolol resembled that of guanethidine in time of onset and persistence of blocking activity but, unlike blocking by guanethidine, was not reversed by (+)-amphetamine. Desipramine and noradrenaline also failed to reverse the blocking action of propranolol. In the rat vas deferens preparation lignocaine had a weaker and more transient sympathetic blocking action than propranolol. It is suggested that the sympathetic blocking action of propranolol may contribute to its antihypertensive effect in man.

Schizophrenia-like psychosis in thyroid crisis

Very few cases of thyrotoxic psychoses have been reported during the last twenty years. Recent authoritative reviews on the management of thyrotoxicosis and its complications (Ingbar, 1966; Trotter, 1967) scarcely mention psychotic reactions. It seems that such conditions have become increasingly rare since the advent of modern anti-thyroid treatment. The present report attempts to summarize what is known about these disorders, and describes the clinical features, treatment and subsequent course of a schizophrenia-like psychosis which developed during thyroid crisis.

Clinical use of I.C.I. 50172 as an antidysrhythmic agent in heart failure

I.C.I. 50172 was used to slow the ventricular rate when conventional treatment had failed in 19 patients. All were either in congestive cardiac failure or in the immediate postoperative period following valve replacement. The ventricular rate was controlled in seven out of eight patients with atrial fibrillation, in six out of nine patients with supraventricular tachycardia, and in two patients with sinus rhythm. Important side-effects were not seen.

Effects of propranolol on the transmembrane potentials of ventricular muscle and Purkinje fibers of the dog

Papillary muscle-false tendon tissue preparations isolated from dog hearts were perfused with Tyrode's solution containing propranolol in concentrations ranging from 0.1 to 20.0 mg/liter. Transmembrane action potentials of both ventricular muscle fibers and Purkinje fibers were recorded. With sufficient concentration of drug, the velocity of the upstroke and the overshoot of both fiber types decreased. The curve relating upstroke velocity to level of membrane potential for Purkinje fibers was displaced to the right and down. The ability of both ventricular muscle fibers and Purkinje fibers to respond to rapid frequencies of stimulation was decreased. Repolarization of Purkinje fibers was accelerated by propranolol, but repolarization of ventricular muscle fibers was unaffected. Duration of the effective refractory period of Purkinje fibers decreased; that of ventricular muscle fibers was unchanged. Graded responses and decremental impulse conduction in Purkinje fibers were abolished in the presence of propranolol. Low doses of propranolol which caused no change in the transmembrane potential completely blocked the increase in Purkinje diastolic depolarization normally induced by epinephrine. The possible mechanisms by which propranolol might exert its antiarrhythmic actions on ventricular arrhythmias were discussed.