Effects of a cardio-selective beta-adrenergic blocker (I.C.I. 50172) at exercise in angina pectoris

Beta1-blocker (practolol) and exercise in patients with chronic obstructive lung disease

Ventilatory and circulatory data from 20 patients suffering from chronic obstructive lung disease have been obtained before, during and after exercise at 600 kpm/min for 5 min on a bicycle ergometer. The patients had been given intravenously practolol, 15 mg, or saline alternatively, using a double-blind cross-over technique. A slight postexercise reduction of FEV1 (8%) was noted after practolol medication as compared to placebo, with an accompanying decrease in PaCO2; PaO2 did not differ substantially. No wheezing or inappropriate dyspnea attributable to the medication was noted in any of the patients. The well known beta1-blocking effects on the circulation were confirmed, with maintained Q and reduced HR, together with a lowered systemic BP during and after exercise. There was a significant positive relationship between the postexercise reduction of FEV1 and the concomitant fall in HR. It is concluded that practolol in doses with near maximal circulatory effects had a slight, but clinically insignificant effect on the ventilatory parameters.

Chest pain at exercise and coronary heart disease

In patients with stable exertional angina the pain reaction during and after exercise has been classified and analyzed with regard to reproducibility, time relationship between pain and ECG reactions with ST-depression. The pain reaction has a good reproducibility - at least as good as the ECG reaction - both within the day and from day to day. The pain usually appears a few minutes after the appearance of ST-depression but there are big individual variations. For any given patient the time relationship between pain - and ECG-reaction is fairly constant but beta-blockers and myocardial infarction may increase the pain threshold in individual cases. To conclude the analysis of the pain reaction adds valuable information to the exercise test both in patients with ischaemic heart disease and in patients with angina-like pain of other causes.

Mechanisms of pain in angina pectoris--a critical review of the adenosine hypothesis

Clinical characteristics: Angina pectoris represents a visceral pain caused by reversible myocardial ischemia. The majority of ischemic attacks are symptomless. When pain is manifested, it appears late during the ischemic event. The pain is complex in its quality and bears little relation to the region of myocardial ischemia. Pain shows a sensitive dependence on initial conditions suggesting a mechanism with deterministic chaotic dynamics for the association between myocardial ischemia and pain. Neurophysiological substrate: Ganglia are present within the heart, particularly in epicardial fat. The blood supply of intrinsic cardiac ganglia arises primarily from branches of the proximal coronary arteries. Both afferent and efferent neurons within the intrinsic cardiac nervous system exist, while the majority of neurons in that location may be local circuit neurons. Integration takes place not only in the intrinsic cardiac nervous system, but also in mediastinal, middle cervical, and stellate ganglia. Cardiac afferent receptors are also connected to cell bodies in dorsal root and nodose ganglia, as well as intrathoracic ganglia. Myocardial regions have no spatial representation in these ganglia. Adenosine, among a number of substances, can modulate the activity generated by cardiac afferent nerve endings and intrinsic cardiac neurons. Such effects appear to be exerted at A1 receptors. Adenosine as a pain messenger: During myocardial ischemia adenosine is released in large quantities into the interstitial space. The endothelium takes up the major amount of adenosine. Thus only small increments of adenosine are detected in the blood-stream. Given as an intravenous bolus to healthy volunteers or to patients with ischemic heart disease and angina pectoris, adenosine provokes angina pectorislike pain, which is similar to habitual angina pectoris with regard to quality and location. Pain is provoked in the absence of ECG signs of ischemia. Patients with asymptomatic myocardial ischemia are less sensitive to adenosine, whereas patients with Syndrome X are more sensitive with respect to adenosine-provoked pain. When adenosine is given intraarterially, including into the coronary arteries, pain is provoked in the corresponding vascular bed. Adenosine-provoked pain and ischemic pain are counteracted by previous administration of the adenosine receptor antagonist theophylline.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects and adverse effects of autonomic blockade in physical exercise

Training bradycardia during autonomic blockade has been studied in rats and humans. The heart rate after autonomic blockade (intrinsic heart rate) is also lowered as a part of the adaptation to training. However, this nonautonomic component of the cardiac adaptation requires a long duration of intense endurance training to appear. This is in contrast to the autonomic component of the training bradycardia. From animal studies we have concluded that even if the training bradycardia is due to an adaptation within the heart itself, the adrenergic nerves are important for the development of a slow intrinsic heart rate. Neither the beta-receptor stimulation nor the degree of the heart rate increase during exercise is the main stimulus for the development of a training-induced bradycardia. Well-trained bicyclists had an intrinsic heart rate 20 beats lower than untrained normal control subjects. The heart rate at rest and the maximal heart rate were also on an average 20 beats lower for the bicyclists. There was no significant difference between propranolol and the beta 1 selective metoprolol in this study regarding their effects on heart rate and on deterioration of the maximal oxygen consumption after blockade. This deterioration was more marked in the well-trained than in the sedentary group. Based upon studies both in normal subjects and patients a careful rating of symptoms including physical exertion, fatigue or pain in the legs, dyspnea and chest pain using a Borg scale is recommended during exercise testing with beta blockade.(ABSTRACT TRUNCATED AT 250 WORDS)

Improvement in exercise capacity and associated changes in hemodynamics and left ventricular function after the addition of metoprolol to nifedipine in patients with stable exertional angina

In 10 men with stable exertional angina, the changes in exercise capacity, hemodynamics, and left ventricular (LV) function were measured after 20 mg sublingual nifedipine (N) and again after adding 100 mg oral metoprolol (M). Nifedipine alone did not significantly improve exercise workloads (+18%) and duration (+21%), but the addition of metoprolol increased both parameters by a further 37 and 32%, respectively (both p less than 0.005 vs. N). After nifedipine the onset of angina was slightly delayed (5.14 +/- 2.41 min placebo (P), 6.00 +/- 2.31 min N, p less than 0.1) and occurred at higher workloads (36 +/- 17 W P, 43 +/- 8 W N, p less than 0.1). After the addition of metoprolol, the onset of angina was delayed substantially more (9.57 +/- 2.22 min, p less than 0.001 vs. P and N) and occurred at much higher workloads (62 +/- 20 W, p less than 0.001 vs. P and N). At rest (R) and during exercise (E), nifedipine decreased systemic vascular resistance (-36% R, -27% E, both p less than 0.001) and mean arterial pressure (-18% R, -21% E, both p less than 0.001), and increased heart rate (+15% R, +11% E, both p less than 0.001), Pulmonary artery wedge pressure on exercise increased less (22 +/- 7 mmHg P, 13 +/- 5 mmHg N, p less than 0.001). After adding metoprolol, the major change was a reduced heart rate (-25% vs. N at R and E, both p less than 0.001), and arterial pressure was unaltered. Pulmonary artery wedge pressure on exercise increased to 18 +/- 5 mmHg (p less than 0.05 vs. N). Exercise LV ejection fraction and volume did not change significantly after adding metoprolol despite marked improvement in angina. In this acute exercise study in patients with stable exertional angina, metoprolol added to nifedipine markedly improved exercise capacity by preventing the increase in heart rate seen with nifedipine. In our patients with relatively normal LV function at rest, the combination was safe and produced no deleterious effects on LV function.

The effect of withdrawal of beta-adrenergic blockade on intermittent claudication

Twenty-eight patients with intermittent claudication were studied before and one month after withdrawal of treatment with beta-adrenergic blocking drugs for hypertension, coronary heart disease or both. Heart rate, blood pressure, ankle/arm systolic blood pressure ratio and ankle pulse volume recording (PVR) at rest and after treadmill exercise were recorded, as well as walking distance, time of recovery from subjective symptoms, restitution time of pressure ratio and PVR. A control group of 14 patients, whose beta-adrenergic blocking drugs were not withdrawn, was also included. The result can be summarized as showing that withdrawal of beta-blockade was not demonstrably advantageous in patients with intermittent claudication. Significant improvement was observed only during the first month of the trial, a change which was independent of withdrawal of beta-blockade. The relief of subjective symptoms after exercise occurred significantly faster after withdrawal of nonselective beta-blockade. Otherwise, there was no difference between nonselective and cardioselective beta-adrenergic blocking drugs.

Comparison of once and twice daily sotalol in exercise-induced angina pectoris

The efficacy of chronic oral treatment with a total daily dose of 320 mg sotalol, given as a single or as two divided doses, was compared with placebo in a double-blind cross-over study of 12 patients with angina pectoris. Sotalol given once or twice daily significantly reduced heart rate and systolic and diastolic blood pressures at rest. The exercise heart rates were significantly decreased in both treatment groups. After sotalol 320 mg once daily, there was a greater reduction in the maximum exercise heart rate 2 h after taking the last tablet than after sotalol 160 mg b.i.d. The systolic blood pressure at the highest comparable work-load was significantly and equally reduced by sotalol both once and twice daily. Total work (watts X minutes in both sotalol treatment groups was significantly increased compared to placebo. There was no difference between the two sotalol dosage regimens. The peak plasma levels were higher after the once daily treatment, but the trough levels were similar for both regimens. No serious side effects were observed.

Exercise testing for detection of myocardial ischemia in patients with abnormal electrocardiograms at rest

This review consists of two parts: (1) discussion of the electrophysiologic mechanisms that are believed to produce ventricular repolarization changes during the electrocardiographic stress test, and (2) clinical assessment of the electrocardiographic changes with stress in patients with an abnormal electrocardiogram at rest. In the first part, the mechanisms of S-T segment elevation, S-T segment depression, T wave changes and linked S-T and T wave changes are reviewed. In the second part, all electrocardiographic abnormalities at rest are grouped into four categories: (1) changes that mask the manifestations of ischemia, (2) changes that stimulate or exaggerate the manifestations of ischemia, (3) changes that have no important effect on the manifestations of ischemia, and (4) changes that reproduce the patterns of acute myocardial infarction after an apparent healing. The reported studies of electrocardiographic stress testing in patients who have abnormal electrocardiogram at rest are summarized.

Hemodynamic effects of two cardioselective beta-adrenoceptive antagonists, metoprolol and H 87/07, in coronary insufficiency

Nineteen patients with ischemic heart disease were randomized into two groups and received either metoprolol or H 87/07. Heart catheterization was performed, and the groups were studied at rest and during exercise--before and after intravenous drug administration. During work metoprolol gave a statistically significant reduction in left ventricular work (expressed as pressure-rate product) of about 20%, mainly depending on a reduction in heart rate. Cardiac output decreased by 21%. Stroke volume was almost unchanged. The abnormal increase in left ventricular filling pressure during work was slightly, but not significantly, reduced by the drug. For H 87/07 no significant changes were found in the corresponding variables. This seems, however, to depend on an inadequate dosage, since not even the heart rate during work was significantly reduced. In conclusion, in the doses used metoprolol has been shown to be a potent beta-adrenoceptive antagonist in contrast to H 87/07.

Cardiovascular and respiratory effects of the beta-adrenoceptive antagonist sotalol: studies in health, angina pectoris and obstructive lung disease

The cardiovascular and respiratory actions of the adrenergic beta adrenoceptive drug sotalol have been studied in an open, short term trial. Fifteen patients with angina performed standardized orthostatic and exercise tests before and after injection of 20 mg sotalol intravenously. Although there was a significant reduction of heart rate and blood pressure at the time of appearance of angina pectoris and ST-segment depression, there was only a slight and statistically insignificant increase in work before the appearance of angina pectoris, and ischaemic changes in the ECG disappeared more rapidly after work. In a different group of patients suffering from obstructive lung disease, sotalol 10 mg intravenously produced a significant increase in airway resistance. It has no such effect on normal subjects.

Assessment of selective beta-adrenoceptor blockade in man

1. Selective antagonism of the cardiac beta(1)-adrenoceptors has been studied in normal human volunteers.2. Practolol and UK 6558 produced greater antagonism of the chronotropic and inotropic responses to i.v. isoprenaline than of the vasodilator response to either i.v. or intra-arterial isoprenaline. A third drug, M&B 17,803A, produced non-selective beta-adrenoceptor blockade in 2 of 3 subjects studied.3. Practolol, UK 6558 and M&B 17,803A, produced an attenuation of the responses to Valsalva's manoeuvre.4. A substantial reduction in blood pressure was seen in 3 of 4 normotensive subjects given UK 6558.

Effects of a new cardioselective beta-adrenergic blocker (tolamolol) on exercise tolerance in patients with angina pectoris

The effect of oral and intravenous tolamolol on exercise tolerance was assessed in 11 patients with angina pectoris. Patients were selected on the basis of an absence of placebo response and the reliable reproducibility of anginal pain and electrocardiographic changes with exercise on a constant load Schönander-Elema bicycle ergometer. The effect of tolamolol on exercise time and heart rate was compared with that of propranolol. Tolamolol was shown to increase exercise tolerance and the effect was comparable to that of propranolol. Tolamolol did not produce a significant increase in airways resistance nor were any untoward side effects noted.

Comparative study of six -adrenoceptive antagonists on airway resistance and heart rate in the guinea-pig

1. The effects of six beta-adrenoceptive antagonists [(+/-)-propranolol, (+)-propranolol, (+/-)-sotalol, (+/-)-practolol, (+/-)-pindolol and (+/-)-procinolol] were studied on airway resistance and heart rate in guinea-pigs and dose-response curves constructed.2. All beta-adrenoceptive antagonists decreased heart rate and increased airway resistance. A significant correlation was found between the increase in airway resistance and the degree of bradycardia induced by all drugs except practolol. The orders of activity of the six drugs in inducing significant variations of the two parameters were respectively, for airway resistance: (+/-)-procinolol>(+/-)-pindolol>(+/-)-propranolol>(+/-)-sotalol>(+)-propranolol>(+/-)-practolol, and for heart rate: (+/-)-pindolol>(+/-)-procinolol>(+/-)-propranolol>(+/-)-sotalol>(+)-propranolol>(+/-)-practolol.3. (+/-)-Sotalol, (+/-)-pindolol and (+/-)-procinolol-induced changes in airway resistance and heart rate reached plateau values, which were not modified by increasing the dose. Since sotalol and procinolol have only very weak partial agonist and cardiac depressant properties, it appears that these changes can mainly be accounted for by the suppression of sympathetic tone. It is probable that this is also the case with pindolol.4. On the other hand, (+/-)-propranolol and (+)-propranolol induced dose-related changes in airway resistance and heart rate. Thus, a direct and non-specific effect of both drugs on the bronchial muscle, similar to that observed on the heart appears to be implicated, together with sympathetic tone suppression in these variations.5. (+/-)-Practolol-induced effects on airway resistance and heart rate were different from those observed with the five other beta-adrenoceptive antagonists.

Clinical evaluation of practolol, a new cardioselective beta-blocking agent in angina pectoris

In a controlled double-blind study practolol, a new cardioselective beta-blocking drug, was given to 15 patients with angina pectoris, and compared with propranolol 80 mg. q.d.s. The dose of practolol ranged from 200 to 600 mg.b.d. and was decided by initial open titration in individual patients. Though practolol did not influence the incidence of angina or glyceryl trinitrate consumption, it increased the duration of exercise possible in exercise tests and reduced the amount of ischaemic S-T depression in the radiocardiogram during exercise. Propranolol reduced the incidence of angina and, in the exercise tests, increased the amount and duration of exercise but did not affect the degree of S-T depression. Unlike propranolol, practolol did not produce any adverse effects on bronchial smooth muscle. Hence it is concluded that practolol is an effective drug in treating angina, and in the dosage used is of potential value in patients with asthmatic bronchitis and angina. It should, however, be used cautiously in anginal patients with heart failure.

Mechanism of action of beta-adrenergic receptor blocking agents in angina pectoris: comparison of action of propranolol with dexpropranolol and practolol

The effect on exercise tolerance of racemic propranolol has been assessed in eight angina pectoris patients and compared with that of dexpropranolol (the dextro isomer of propranolol), practolol (I.C.I. 50172), and saline. Dexpropranolol has the same local anaesthetic action as propranolol with negligible beta-adrenergic receptor blocking activity, while practolol is a cardio-selective beta-adrenergic blocking agent which does not have local anaesthetic activity.Saline and dexpropranolol had no significant effect on exercise time; racemic propranolol and practolol improved exercise tolerance in six subjects, the response to the two drugs being very similar in individual patients. It was concluded that the beneficial effect of propranolol in angina pectoris results from its action as a beta-adrenergic receptor blocking agent and is not due to its local anaesthetic, or quinidine-like, activity.