Effects of propranolol on exercise tolerance in angina pectoris

Transregulation of the alpha2-adrenergic signal transduction pathway by chronic beta-blockade: a novel mechanism for decreased platelet aggregation in patients

Platelets play a pivotal role in the pathophysiology of acute coronary syndromes. Chronic beta-blockade has been shown to improve the long-term clinical outcome in coronary heart disease. Because platelets play a central role in thrombus formation, the aim of the present study was to investigate if chronic beta-blockade may transregulate the expression of alpha2-adrenergic receptors on human platelets and via this mechanism may modulate platelet activation. The densities of alpha2-adrenergic receptors of platelets were determined in healthy volunteers under chronic beta-blockade and as alpha2-adrenergic receptor-mediated function in catecholamine-induced platelet aggregation was determined. Chronic beta-blockade induced a time-dependent reduction of alpha2-adrenergic receptors. This reduction was accompanied by a decrease of the alpha-subunit of Gi proteins as demonstrated by Western blot analysis. This transregulation at both the receptor level and the G-protein level resulted in an almost complete loss of the alpha2-adrenergic receptor-mediated inhibition of adenylyl cyclase. The impairment of the alpha2-adrenergic receptor system correlated with a reduction of the catecholamine-induced activation and aggregation of human platelets. The functional transregulation of alpha2-adrenergic receptors by chronic beta-blockade in platelets and the consequent impairment of platelet activation may contribute to the therapeutic success of beta-blocker therapy.

Bioavailability of propranolol following oral and transdermal administration in rabbits

The systemic bioavailability of propranolol was evaluated following oral and transdermal administration in rabbits. Using a four-way crossover study, the bioavailability of propranolol following oral administration was determined to be 12.3 +/- 5.9%, indicating that propranolol is subject to extensive hepatic first-pass metabolism in rabbits. Transdermal delivery of propranolol, via an adhesive delivery device, resulted in a bioavailability of 74.8 +/- 10.1%, indicating that the transdermal delivery of propranolol can significantly increase systemic bioavailability over oral administration. Skin irritation studies indicated that neither propranolol nor the adhesive used in the device caused any appreciable skin irritation.

Comparison of the antianginal efficacy of four calcium antagonists and propranolol in stable angina pectoris

The antianginal effects of propranolol 160 mg/day, diltiazem 240 mg/day, nicardipine 80 mg/day, nifedipine 40 to 80 mg/day and verapamil 320 mg/day were compared in 12 patients with chronic stable angina pectoris using a symptom-limited exercise test. Compared to placebo propranolol and calcium antagonists similarly reduced (p less than 0.001) the frequency of antianginal attacks and nitroglycerin consumption, and increased exercise tolerance and time to greater than or equal to 1 mm S-T segment depression. After propranolol the pressure-rate product at submaximal and maximal exercise was significantly decreased. The calcium antagonists produced a significant reduction in the submaximal pressure-rate product, but no significant change in the peak pressure-rate product. Maximum ST depression was significantly lower after propranolol and was unchanged after the calcium antagonists. None of the drugs caused significant adverse effects. The results indicate that in patients with stable effort angina pectoris, diltiazem, nicardipine, nifedipine and verapamil were as effective as propranolol in improving exercise tolerance and time to ischaemia, and they did not alter the peak pressure-rate product. Different antianginal mechanisms may be operative for the various calcium antagonists.

Effectiveness of bevantolol in the treatment of angina--a placebo-controlled study

The antianginal efficacy and safety of bevantolol was compared with placebo in 107 patients with angina pectoris of effort. The median frequency of angina attacks in these patients was 6 per week. Following a 6-week placebo-baseline phase, the patients were randomly assigned to groups receiving either 150 or 300 mg/day bevantolol (75 or 150 mg b.i.d.) or placebo for 6 weeks of double-blind treatment. During exercise tolerance testing at 2 hours postdose, the higher dose of bevantolol produced a marked increase in total work performed. Double product (HR X Systolic BP) at maximum common work load decreased significantly (p less than 0.001) in both bevantolol groups compared with the placebo group. In patients receiving 300 mg/day bevantolol, the proportion who stopped exercising because of angina or S-T depression decreased from 97% to 65%; the frequency of angina attacks decreased by one-half or more in 77% of those with 3 or more attacks per week; and 90% had an improvement in capacity to perform usual daily and occupational activities. A significant therapeutic effect was still present 12 hours postdose. Bevantolol was safe; fewer adverse reactions occurred in either drug group than in the placebo group. Bevantolol appeared to be an effective, well-tolerated drug in the management of angina pectoris.

Propranolol-induced changes in ventricular isomyosin composition in the rat

The ventricular isomyosin composition in the rat is characterized by three isoenzymes, V1, V2, and V3, with high, intermediate, and low Ca++-activated ATPase activity, speed of muscle shortening, and contractile economy. In this study, we examined the effects of propranolol on ventricular isomyosin composition in the rat. Eight 4-week-old male Wistar rats were treated from 4 to 12 weeks of age with daily 10 mg/kg subcutaneous doses of propranolol; four control rats were given subcutaneous distilled water. At the end of the treatment period, the efficacy of beta blockade was confirmed by isoproterenol test in some rats from each group. After the rats were killed left ventricular myosin from both control and propranolol-treated animals was purified and tested for Ca++-activated ATPase activity. Ventricular isomyosin composition was studied by gel electrophoresis in non-denaturing conditions. Heart rate was significantly lower in the propranolol group, while no differences in blood pressure, body weight, or ventricular weight were found between the two groups. Lower Ca++-activated ATPase activity values and a higher expression of myosin isoenzymes V2 and V3 were found in propranolol-treated rats. Possible links between the observed shift in ventricular isomyosin composition and the well-known modifications in myocardial contractility and oxygen consumption occurring after chronic propranolol administration remain to be established.

Oral labetalol in the management of stable angina pectoris in normotensive patients

The efficacy of labetalol, an alpha and beta receptor antagonist, was evaluated in 12 normotensive patients with stable angina pectoris in a single blind dose ranging study. After a two week period of placebo treatment, labetalol was given in doses of 100, 150, 200, and 300 mg twice daily, each for two weeks. Frequency of angina attacks decreased from 9.4 (SEM 2.3)/week in the control period to 7.3 (2.8), 5.2 (2.6), 3.8 (1.8), and 3.3 (1.9)/week in the four successive treatment periods. In the same periods the number of glyceryl trinitrate tablets consumed decreased from 7.0 (2.6)/week to 5.8 (3.3), 3.9 (2.9), 2.7 (1.8), and 2.6 (2.1)/week. Maximal symptom limited treadmill exercise tests were performed three and 12 hours after dosage at each dose. Exercise tolerance (expressed as seconds of the Bruce protocol) increased from 266 (44) with placebo to 306 (44), 369 (50), 396 (48), and 413 (51) in the four treatment periods. This improvement was accompanied by a significant blunting of the heart rate and blood pressure responses to exercise. Trough point exercise tolerance did not differ significantly from that at three hours after dosage. Thus labetalol is effective as an antianginal agent at doses of 150-300 mg twice daily and is well tolerated by the normotensive patient with angina.

Antianginal efficacy and improved exercise performance with timolol. Twice-daily beta blockade in ischemic heart disease

Antianginal efficacy and improved exercise performance with timolol, a new beta-adrenergic blocking agent, was assessed in 23 patients with chronic stable angina pectoris in an 11-week double-blind, placebo-controlled study. Twenty-two of the 23 subjects completed the open-label phase of this investigation (weeks 0 to 6) while receiving 10 to 30 mg of timolol twice daily to optimize exercise capacity. Weekly anginal episodes and nitroglycerin consumption declined from 8.9 +/- 9.1 episodes/week and 8.1 +/- 10.6 tablets/week, respectively, with placebo to 2.7 +/- 5.2 episodes/week and 2.6 +/- 6.0 tablets/week with optimal timolol dose (p less than 0.05). Resting heart rate (HR) and systolic blood pressure (SBP) also decreased from 75.2 +/- 14.0 beats/min and 139.1 +/- 15.7 mm Hg with placebo to 55.1 +/- 8.9 beats/min and 130.5 +/- 15.9 mm Hg with timolol (p less than 0.05). Peak exercise HR, peak exercise SBP, and peak exercise double product (HR X SBP) were significantly (p less than 0.05) reduced when evaluated 12 to 13 hours after administration of timolol compared with placebo (101.5 +/- 21.1 beats/min verus 193.3 +/- 96.2 beats/min, 161.5 +/- 26.7 mm Hg versus 175.6 + 20.8 mm Hg, and 16.6 +/- 5.1 X 10(-3) versus 21.7 +/- 5.4 X 10(-3), respectively). Exercise duration was prolonged from 263.3 +/- 90.2 seconds to 330.3 +/- 73.9 seconds (p less than 0.05), while time to onset of 1 mm S-T segment depression was delayed in 15 patients from 231.8 +/- 86.4 seconds to 298.7 +/- 68.4 seconds (p less than 0.05). During the double-blind phase (weeks 7 to 10), 8 subjects received timolol and 11 patients received placebo. Nitroglycerin consumption at weeks 8 and 10 and anginal frequency at week 8 were unchanged compared with initial placebo treatment. Resting HR, peak exercise HR, and peak exercise double product were significantly attenuated at weeks 8 and 10 in timolol patients compared with their initial placebo exposure. However, these variables were unchanged in placebo subjects compared with their initial placebo therapy. Exercise duration was again prolonged at week 8 in timolol subjects compared with initial placebo results (315.1 +/- 61.2 seconds versus 261.3 +/- 68.8 seconds, p less than 0.05), but not at week 10. Placebo patients demonstrated no difference at week 8 or 10 in exercise performance compared with initial placebo treatment. Timolol twice daily, therefore, is potentially useful in some patients with angina pectoris. Other patients may, however, require a shorter dose interval for optimal angina control and maximal improvement in exercise capacity.

Ischemic pain relief in patients with acute myocardial infarction by intravenous atenolol

Pain relief in acute myocardial infarction (AMI) by the beta-adrenoceptor antagonist, atenolol, was demonstrated by three separate studies. First, 18 patients were randomized to double-blind intravenous atenolol (5 mg) or saline immediately after admission, followed by oral atenolol (50 mg) or placebo 10 minutes later. In patients receiving atenolol, pain relief coincided with reduction in heart rate (HR), systolic blood pressure (SBP), and HR X SBP product (p less than 0.05); however, pain and these parameters were unchanged by placebo. The degree of pain relief was related to the reduction in cardiac work achieved (r = 0.725; p less than 0.001). A second open study involving 22 patients receiving intravenous atenolol (5 to 15 mg) early after AMI showed ischemic pain relief in 17 patients. They achieved a more significant reduction in HR X SBP product than those whose pain remained unchanged (p = 0.004). Finally, a retrospective study of 163 patients randomized to either atenolol or no beta blockade early after AMI revealed that patients receiving atenolol needed less opiate analgesia after admission (p less than 0.001). The safety of this therapy was illustrated by a decreased incidence of left heart failure and atrial fibrillation and no tendency to second- and third-degree heart block.

Exacerbation of vasotonic angina pectoris by propranolol

Using a double-blind protocol, we investigated the use of propranolol in patients with coronary artery spasm as assessed by subjective and objective variables. Both low-dose (40 mg every 6 hours) and high-dose (160 mg every 6 hours) propranolol were administered. At both doses, the duration of angina attacks was significantly prolonged but the frequency was not. We conclude that propranolol at doses up to 160 mg every 6 hours as single therapy is frequently detrimental in angina pectoris due to coronary artery spasm and should not be used as the sole treatment of this disorder.

The combination of nifedipine and propranolol in the management of patients with angina pectoris

1 A double-blind cross over study was carried out to assess the effects of the combination of nifedipine and propranolol in 25 patients with chronic stable angina pectoris at beta-adrenoceptor blockade. 2 Efficacy was judged objectively by a standardized exercise protocol using a bicycle ergometer and subjectively by patient assessment of anginal attack rate. 3 The combination of nifedipine and propranolol was shown to be effective with an increase in exercise time to angina and an increase in physical work capacity expressed in terms of calculated maximal oxygen uptake (VO2 max). There was an associated reduction in anginal attack rate. 4 The synergistic effect was even more pronounced after reduction in propranolol dosage to 50% of the beta-adrenoceptor blocking dose, reflecting the myocardial depressant effects of beta-adrenoceptor blocking drugs in these patients with coronary heart disease, some of whom had poor left ventricular function.

Reduction of enzyme levels by propranolol after acute myocardial infarction

The effect of propranolol (0.1 mg/kg intravenously followed by 320 mg given over 27 hour orally) on serum levels of creatine kinase enzyme was studied in a randomized trial involving 95 patients seen within 12 hours of onset of symptoms of uncomplicated myocardial infarction. In 15 patients who were treated with propranolol within 4 hours of onset, and who eventually developed pathological Q waves, peak measured enzyme levels were 27% (P less than 0.0125) lower than in 19 control patients who were also seen within 4 hours of the onset but had no specific treatment. Total calculated enzyme appearance was also lower in the treated patients (reduced 25%, P less than 0.05) as was the calculated rate of the appearance (33%, P less than 0.005). No significant difference was found for treated compared with control patients entering the trial more than 4 hours after the onset of chest pain. This evidence suggests that propranolol may reduce the size of uncomplicated infarctions if it is given intravenously within 4 hours of the onset.

[Coronary heart disease and bypass surgery: a clinical cardiologist's view (author's transl)]

The main goal of bypass surgery (BPS) is improvement of angina pectoris (AP), of performance of LV function, and of the prognosis of AP. Recently reported statistics indicate a significant improvement of the prognosis after BPS, especially in double or triple vessel disease. The main indication remains severe AP with significantly impaired performance, but prognostic aspects can also affect the decision of BPS. The area of regional ischemia should be determined by means of angiography during stress, and regional flow should be measured (scintigraphy etc.) to allow a more accurate definition of critical narrowings.

Exercise stress testing in evaluation of aortocoronary bypass surgery. Report of 123 patients

Graded exercise treadmill tests (ET) were performed on 123 patients who had undergone aortocoronary bypass surgery. All had angina preoperatively (preop) and 77% were in Class III or IV for angina. Postoperatively (postop), 68% were free of angina. Eighty-three patients had ST-segment changes of 0.1 mV or greater during stress preop (positive), 38 of which (46%) converted to electrocardiographically negative postop. Among the 30 patients (36%) remaining positive during stress postop, 19 (63%) were angina free despite ST-segment depression during stress. Among the 17 patients with negative ET preop, there were no conversions to positive postop. Twenty-three patients had undetermined ET preop; 13 remained undetermined postop, 4 were positive and 6 were negative. Patients experiencing a perioperative myocardial infarction more frequently had a negative postop ET. Among 27 selected patients undergoing postop angiography, there was good correlation between relief of symptoms and successful myocardial revascularization.

This study demonstrates that dramatic improvement in angina after aortocoronary bypass surgery can be objectively substantiated in most patients. Subjective symptoms of angina are frequently absent during myocardial ischemia postop, emphasizing the importance of exercise testing in objective evaluation of surgical results.

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.

Medical management of angina pectoris

The successful medical management of a patient with angina pectoris requires careful attention to many factors including omission of smoking, control of hypertension, and weight reduction for the obese person. Newer knowledge of the importance of the product of the systolic blood pressure and the pulse rate in determining the threshold of angina affords a more meaningful approach to therapy. Each individual must be educated regarding the factors that aggravate and precipitate his distress so that these can be minimized, or prophylactic nitrite therapy can be appropriately applied. Emotional stress is of equal importance to effort in the production of angina. The mainstay stay of treatment is nitroglycerin and sublingual nitrites combined with beta-blocking drugs. Each drug or combination must be properly readjusted for the individual to assure optimum benefit. Digitalis, diuretics, antiarrhythmic drugs, antihypertensive agents, and radioiodine may be useful in selected cases.

Clinical, electrocardiographic, and haemodynamic effects of long-term use of propranolol in Prinzmetal's variant angina pectoris

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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.

Effects of propranolol on response to exercise in hypertrophic obstructive cardiomyopathy

The circulatory, respiratory, and metabolic responses to steady state submaximal exercise have been studied in four women and two men with hypertrophic obstructive cardiomyopathy, before treatment, after intravenous, and after three months of oral propranolol. The physical working capacity was significantly lower than in normal subjects, and the response to exercise was characterized by a tachycardia, low cardiac output and stroke volume, and high ventilation and blood lactate concentration. After propranolol there was a significant reduction in heart rate, but changes in most other measurements were slight and there was no improvement in effort tolerance though angina was relieved in the two patients in whom it was present. The possible causes of breathlessness and effort intolerance in hypertrophic obstructive cardiomyopathy are discussed in relation to known effects of propranolol. It is concluded that further trial of propranolol and other beta-adrenergic blocking agents is warranted.

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.

Hemodynamic effects of nitroglycerin, propranolol, and their combination in coronary heart disease

The hemodynamic effects of 10 mg of propranolol given intravenously (iv) were studied in 10 patients (group I) with coronary heart disease (CHD). These results were compared with the hemodynamic effects in a similar group of the nine (CHD) patients (group II) who were studied after administration of 0.6 mg of nitroglycerin and then after receiving 10 mg of propranolol iv with a second 0.6-mg dose of nitroglycerin. Measurements were obtained at rest and during exercise: before treatment, after nitroglycerin alone, after propranolol alone, and after nitroglycerin-propranolol in combination. Pretreatment exercise showed a 125% increase in mean pulmonary artery pressure (PAP) to 43 mm Hg and a 163% increase in left ventricular end-diastolic pressure (LVEDP) to 29 mm Hg. Nitroglycerin decreased PAP (–45%) and LVEDP (–66%); as did nitroglycerin-propranolol: PAP (–33%) and LVEDP (–38%). Nitroglycerin reduced tension-time index (TTI) –21%, and increased cardiac index (CI) +17%, heart rate (HR) +10%, left ventricular work index (LVWI) +11%, and left ventricular dp/dt (LV dp/dt) +22%. By contrast, nitroglycerin-propranolol reduced LVWI –14%, LV dp/dt –30%, TTI – 15%, and HR – 13% but did not significantly alter CI from pretreatment.

Propranolol increased PAP to 40 mm Hg, did not change LVEDP at 29 mm Hg and decreased stroke index (SI) 16%. Nitroglycerin-propranolol diminished PA and LVED pressure and increased SI 14%. Effects of propranolol alone and of nitroglycerin-propranolol on HR, TTI, and LV dp/dt were not significantly different.

Nitroglycerin-propranolol appears to have important advantages over nitroglycerin or propranolol alone. A reduction in HR, TTI, and LV dp/dt, determinants of myocardial oxygen consumption, concurrent with improved left ventricular function, demonstrates a beneficial synergistic hemodynamic action for nitroglycerin combined with propranolol.

Effects of propranolol and isosorbide dinitrate on exercise performance and adrenergic acitivity in patients with angina pectoris

Twelve patients with angina pectoris were evaluated in a single blind crossover study with respect to objective changes in exercise performance on the treadmill and subjective, clinical improvement on oral administration of propranolol, isosorbide dinitrate (ISD), and a combination of propranolol and ISD. Combined objective and subjective evaluations showed that nine of 12 patients improved on propranolol, seven of 10 on ISD, and all 10 on the combination of drugs. The differences in objective improvement between the various drug regimens were not significant. However, subjectively all patients on the combination of drugs improved markedly. The patients on propranolol or the combination had a decrease in pressure-rate index of about 30% both at rest and during exercise, while these values did not change on ISD. A significant reduction in exercise-induced S-T depression was observed with propranolol alone and in combination with ISD at grade 3+ pain. Adrenergic activity, estimated from plasma and urinary catecholamines, appeared to be increased in these patients before drug treatment and was not altered during treatment. It is concluded that propranolol, ISD, and the combination of these drugs all improve exercise performance in patients with angina. Although the combination of drugs could not be shown to produce a greater increase in exercise performance than either drug alone, the combination effected a greater overall clinical improvement.

Effects of beta-adrenergic blockade (propranolol) on left ventricular hemodynamics and the electrocardiogram during exercise-induced angina pectoris

The effects of intravenous propranolol were studied in nine patients with ischemic heart disease during cardiac catheterization. Values were obtained at rest and during exercise before and after propranolol. A work load known to produce angina and significant ST depression was selected. Pressures were monitored during exercise and correlated with electrocardiographic changes and appearance of angina. At rest and exercise, propranolol caused a decrease in heart rate, cardiac output, mean systolic ejection rate, stroke volume, left ventricular systolic pressure, first derivative, and work. Left ventricular end-diastolic pressure did not significantly change. Angina, which developed in all nine patients during control exercise, did not appear in four after propranolol, while ECG abnormalities were less marked in all cases. Comparison of exercise responses following propranolol in angina-free patients (four) with those developing angina (five) disclosed a more pronounced negative inotropism in the angina-free group. It is concluded that propranolol is beneficial in angina. Improvement derives primarily from suppression of positive chronotropic and inotropic responses, which are major determinants of myocardial oxygen consumption.

Clinical evaluation of verapamil in angina pectoris

A controlled double-blind study of verapamil in 16 anginal patients used two dose levels-40 mg. t.d.s. and 120 mg. t.d.s.-and was compared with propranolol 100 mg. t.d.s. At the higher dosage verapamil produced a significant improvement in frequency of angina, trinitrin consumption, and exercise tolerance, and had a favourable and significant effect on the amount and duration of ischaemic S-T depression occurring in the electrocardiogram during exercise. In the lower dose verapamil produced significant subjective improvement but no objective benefit in the electrocardiogram. No significant differences were found between the favourable results with the higher dosage of verapamil and propranolol.The action of verapamil is not fully understood, but its favourable effects in angina may be due to a direct action on the myocardium, possibly with accompanying coronary vasodilatation.