Medical Therapy of Stable Angina Pectoris

Nitrates as an integral part of optimal medical therapy and cardiac rehabilitation for stable angina: review of current concepts and therapeutics

The goals of optimal medical therapy in patients with stable angina pectoris are to reduce the risk of cardiovascular mortality and future cardiovascular events, improve exercise capacity, and enhance quality of life. Whereas myocardial revascularization is frequently employed in the management of patients with stable angina, a variety of pharmacologic interventions are recommended as part of optimal medical management. The use of short- and rapidly-acting nitrates (eg, sublingual nitroglycerin spray and tablets) is at the core of the therapeutic armamentarium and should be integrated into optimal medical therapy for stable angina along with exercise therapy. The potential clinical implications from these observations are that prophylactic sublingual nitrates, when combined with cardiac rehabilitation, may allow the patient with angina to exercise to a greater functional capacity than without sublingual nitrates.

Side effects of using nitrates to treat angina

Nitrates are very effective antianginal and anti-ischaemic agents. Provision of a long nitrate-free interval or low plasma nitrate levels prior to the morning dose prevents the loss of clinical efficacy by preventing the development of tolerance. However, side effects during nitrate therapy are common. Headache is the most common side effect of nitrates; often dose-related and reported by up to 82% of patients in placebo-controlled trials. Nearly 10% of patients are unable to tolerate nitrates due to disabling headaches or dizziness. In others, headaches are mild-to-moderate in severity and either resolve or diminish in intensity with continued nitrate therapy. Nitrate-induced hypotension is common, but often asymptomatic. In rare instances, nitrate-induced hypotension is severe and accompanied by marked slowing of the heart rate and syncope. Use of nitrates in patients who experience syncope after administration of nitrates is contraindicated. Nitrates rarely cause coronary steal and myocardial ischaemia. Nitrate rebound may occur and patients may experience nocturnal anginal episodes during intermittent therapy with nitroglycerin patches. Administration of nitrates is contraindicated with concomitant use of phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction, as combination therapy may lead to profound hypotension and even death. There are disturbing observational reports in the literature that continuous, prolonged use of nitrates may lead to increased mortality and recurrent myocardial infarctions. Large, randomised, placebo-controlled studies are needed to confirm or refute these reports; until then, the use of nitrates to treat angina is here to stay.

Current medical management of chronic stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina. The coronary arteries of patients with stable angina also contain many more non-obstructive plaques, which are prone to rupture resulting in acute coronary syndrome (unstable angina, myocardial infarction, sudden ischemic death). Therefore, the medical management must use strategies which not only relieve symptoms and prolong angina free walking but also reduce the incidence of adverse clinical outcomes. Whether any of the approved antianginal drugs, nitrates, beta-blockers, and calcium channel blockers reduce the incidence of adverse clinical outcomes in patients with stable angina has not been studied to date. Published data shows that percutaneous coronary revascularization procedures and coronary bypass surgery are effective in relieving angina but these procedures do not reduce mortality or the incidence of myocardial infarction compared to anti-anginal drug therapy. From the available data, an initial trial of medical treatment with anti-anginal drugs and strategies to reduce adverse clinical outcomes (smoking cessation, daily aspirin, treatment of dyslipidemias and hypertension) is indicated in most patients with stable angina pectoris. The initial choice of drug will depend on the presence or absence of comorbid conditions. Patients who do not respond to medical therapy or do not wish to take anti-anginal drugs and whose life style is limited because of anginal symptoms should be offered percutaneous revascularization procedures with or without stent placement or coronary bypass surgery. New drug-coated stents hold promise but long-term data and large-scale trials assessing the continued long-term improvement in symptoms and reduction of adverse outcomes is needed before offering such devices to all patients with stable angina. Newer medical therapies such as metabolic modulators and sinus rate lowering drugs also hold promise but need further evaluation. Patients who have refractory angina despite optimal medical therapy and are not candidates for revascularization procedures may be candidates for some new techniques of enhanced external Counterpulsation, Spinal Cord Stimulation, sympathectomy or direct transmyocardial revascularization. The usefulness of these techniques, however, needs to be confirmed in large randomized trials.

Treatment of stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Factors associated with the use of various medications amongst patients with severe coronary artery disease. SECOR/SBU Project Group

AIM

To describe variations by age, sex, symptom severity and hospital region in the use of various medications amongst patients with stable angina pectoris who are candidates for coronary revascularization.

PATIENTS

Patients (n = 2030) with chronic stable angina pectoris participating in a national survey evaluating the appropriateness of the use of percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG).

METHODS

As part of a national study of the appropriateness of coronary revascularization, data were prospectively collected on patients referred for consideration of coronary revascularization to seven of the eight public Swedish heart centres that performed approximately 92% of all bypass operations in Sweden in 1994.

RESULTS

Amongst all patients 76% were treated with beta blockers, 41% with calcium antagonists and 71% with long-acting nitrates and 70% were treated with at least two of these three drugs. Eighty-two per cent of the patients used aspirin and 14% lipid-lowering drugs. According to logistic regression analysis, with medication as the dependent variable and independent variables of age, sex, angina functional class, findings at exercise test, history of various diseases and region in Sweden where the investigation took place, the most consistent factor explaining the use of various medications was found to be geographical region. A previous history of acute myocardial infarction (AMI) was also associated with the use of all drugs and age was associated with all with the exception of beta blockers. Sex was not an independent factor explaining the use of any of the drugs.

CONCLUSION

In a national survey including patients with stable angina pectoris who are potential candidates for coronary revascularization, the most important predictor for the use of various medications was the geographical region in which the investigation took place.

Achieving sustained improvement in myocardial perfusion: role of isosorbide mononitrate

The efficacy of antianginal agents in the treatment of patients with chronic stable angina has traditionally been evaluated by performance measures, such as the exercise treadmill test (ETT). Although reliable and reproducible, ETT is not a sensitive measure of changes in myocardial ischemia. The effects of antianginal agents on coronary blood flow and myocardial perfusion have been less frequently studied. Angiographic studies have demonstrated that nitrates may operate by preferentially directing blood flow to ischemic regions of the myocardium. These investigations have been limited, however, by the invasive nature of the evaluation. Measurements of regional myocardial perfusion may also be made with noninvasive tests. Both quantitative single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have been employed, but few studies have used these techniques to assess the effects of antianginal drugs (in general) and nitrates (in particular) on changes in reversible myocardial perfusion defects. Studies that have evaluated the direct effects of nitrate treatment on coronary blood flow and myocardial perfusion defects in patients with chronic stable angina are reviewed, and preliminary data from a study of the effects of long-term nitrate treatment on myocardial perfusion are discussed.

Management of patients with chronic stable angina at low risk for serious cardiac events

Successful management of the patient with chronic stable angina requires correct stratification by assessing the risk of future coronary events. Patients at low risk for such events have a relatively good prognosis; revascularization procedures (balloon angioplasty or surgery) offer no benefit over medical management. Such patients should be offered medical therapy as their first option. The goals in management of chronic stable angina are (1) treatment of other conditions that may worsen angina; (2) treatment with aspirin and modification of risk factors for coronary artery disease (CAD) to improve outcome; and (3) effective relief of anginal symptoms. Most patients with stable angina will have CAD. It is well established that treatment with aspirin and modification of risk factors for CAD are beneficial in reducing cardiovascular mortality and morbidity. Blood pressure reduction, lowering of blood cholesterol level, and smoking cessation are interventions of proven value and appear to correct defects (at least partially) in the endothelial function of the coronary blood vessels. Other interventions that are helpful are estrogen replacement treatment in postmenopausal women, and low-dose aspirin therapy-which is recommended for all patients who can tolerate it. For controlling symptoms and improving angina-free walking time, nitrates, beta blockers, and calcium channel antagonists are efficacious as first-line monotherapy for chronic stable angina in this group of patients. Nitrates may be of special use in patients with impaired left ventricular function, overt congestive heart failure, intermittent coronary vasoconstriction, or coronary artery spasm. In patients with concomitant hypertension or supraventricular tachycardia, beta blockers are helpful. Calcium channel antagonists may be useful in patients with chronic obstructive pulmonary disease, peripheral vascular disease, or hypertension. When optimal monotherapy with a given class of drug fails to control symptoms, alternative monotherapy with a different class of agent should be tried before combination therapy. Combination therapy with 2 or 3 agents is not always superior to optimal monotherapy. Patients who fail to respond to adequate medical therapy should be considered for a revascularization procedure.

Postinfarction ventricular aneurysms

Ventricular aneurysms are circumscribed, thin-walled fibrous, noncontractile outpouchings of the ventricle. The majority are apically located, true aneurysms of the left ventricle (LV) that occur as a consequence of transmural myocardial infarction (MI). The precursor of aneurysm formation appears to be infarct expansion early after acute MI and occurrence generally relates to infarct size. The presence of underlying hypertension and the use of steroids and nonsteroidal antiinflammatory agents may promote aneurysm formation. The clinical sequelae include congestive heart failure (CHF), thromboembolism, angina pectoris, and ventricular tachyarrhythmias. Late rupture is a particular complication of false aneurysms in which the pericardium is the aneurysm wall. The diagnosis may be suspected by the clinical finding of a diffuse, pansystolic apical thrust, persistent ST-segment elevation on the electrocardiogram, and distortion of the cardiac silhouette on chest x-ray. This can be confirmed using echocardiography, radionuclide ventriculography, and cardiac catheterization. The latter has the additional advantage of being able to delineate the coronary anatomy. Management involves prevention, specific therapy for the various clinical manifestations, and surgery. Therapeutic interventions with thrombolytic agents, aspirin, heparin, and beta blockers that are applied early in the evolution of an MI may limit infarction size, thereby reducing the tendency toward infarct expansion and aneurysm formation. Patients with mild CHF can usually be controlled with the standard combination of angiotensin-converting enzyme inhibitors, diuretics, and digoxin. Thromboembolism is best prevented by anticoagulation with warfarin for at least 3 months after the acute MI. The choice of pharmacotherapy for ventricular tachyarrhythmias should be guided by electrophysiologic studies. The treatment of patients with angina pectoris utilizes conventional therapeutic modalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Ointments and transdermal nitroglycerin patches for stable angina pectoris

Nitroglycerin (NTG) ointment is used for the prophylaxis against angina pectoris, but there are no data to support its effectiveness during long-term therapy. Continuous, once-daily application of isosorbide dinitrate cream produces tolerance with complete loss of efficacy within 1 week. Nitroglycerin patches are very popular and continuous once-daily application is still claimed by some investigators to provide 24 hour antiischemic and antianginal efficacy. This claim is based on data from postmarketing studies in a very large number of patients and placebo-controlled studies in smaller groups of patients from Italy, Yugoslavia, Greece, and Germany. In contrast, studies from the United States, Canada, England, and some centers in Germany have failed to show superiority of patches over placebo during continuous therapy. This controversy was addressed by the NTG cooperative study group, in which a total of 562 patients who were responders to sublingual nitroglycerin were studied. Patients received either placebo or NTG patches delivering low (15-30 mg/24 hr), moderate (45-60 mg/24 hr), or large (75 and 105 mg/24 hr) amounts of NTG. Four hours after the initial application, NTG patches increased exercise duration compared to placebo, but this beneficial effect had disappeared by 24 hours. Furthermore, after 8 weeks of continuous therapy, none of the NTG patches were superior to placebo, whether patients were or were not taking concomitant beta-blockers. Therefore, current opinion is that continuous therapy with NTG patches produces pharmacologic tolerance and is ineffective.(ABSTRACT TRUNCATED AT 250 WORDS)

Short and long-acting oral nitrates for stable angina pectoris

Nitroglycerin (NTG) spray and sublingual tablets rapidly relieve an established attack of angina, and their infrequent use is not associated with the development of tolerance. Although, following a suitable nitrate-free interval, the first dose of oral, long-acting nitrates produces significant hemodynamic effects, increases angina free walking, and decreases exercise-induced ischemia, during continued long-term therapy tolerance limits their usefulness. Appropriate dosing regimens of controlled-release formulations of isosorbide dinitrate (ISDN) and controlled-release NTG during long-term therapy have not been established. Use of immediate-release formulation of 15-120 mg of ISDN in a qid regimen lead to a marked reduction in the size and duration of antianginal effects compared to the initial dose. Asymmetric tid therapy with 30 mg of ISDN (7 a.m., 1 p.m., and 6 p.m.) is also associated with the development of partial tolerance and appears to provide antianginal prophylaxis for only a period of 6 hours each day. Asymmetric bid therapy with ISDN at 7 a.m. and noon may give sustained effect but is supported by only a single, small study that did not examine effectiveness after the noon dose in long-term use. Isosorbide-5-mononitrate (IS-5-MN) has been the subject of more recent studies than other nitrates because of attempts to bring a number of products into the U.S. market. IS-5-MN in qid, tid, and standard bid (8 a.m. and 8 p.m.) dosing regimens produce tolerance. Asymmetric regimens of immediate-release IS-5-MN (10 and 20 mg) given bid (once in the morning and again 7 hours later) decrease the development of tolerance compared to symmetric regimens and produce an increased exercise duration after each dose of the day; the 20 mg bid dosing is more effective. Similarly, once-daily 120 and 240 mg controlled-release IS-5-MN does not produce tolerance and gives a sustained increase in daytime exercise duration. Both asymmetric bid immediate-release and once-daily controlled-release IS-5-MN preparations do not produce deterioration in exercise performance prior to the administration of the medication in the morning (i.e., no zero-hour effect). Further studies are needed to establish useful dosing regimens for ISDN, for controlled-release ISDN, and for controlled-release nitroglycerin. None of the dosing regimens of any oral, long-acting nitrate (including IS-5-MN) provide 24 hour antianginal and antiischemic effects.(ABSTRACT TRUNCATED AT 400 WORDS)

Concomitant use of nitrates, calcium channel blockers, and beta blockers for optimal antianginal therapy

Despite the introduction of new mechanical techniques for revascularization, pharmacologic therapy continues to be the mainstay of antianginal therapy. The conventional antianginal medications, which include nitrates, beta blockers, and calcium channel blockers, act to correct the imbalance between myocardial supply and demand by increasing coronary blood flow, reducing myocardial oxygen requirements, or both. All three are appropriate for the management of angina caused by a fixed coronary obstruction, but nitrates and calcium channel blockers, which not only reduce demand but also increase supply, are preferred in cases of angina believed to involve a significant increase in vasomotor tone. Because of the different yet complementary mechanisms of action of the three classes of anti-ischemic drugs, use of these agents in combination is a rational approach to the treatment of angina unresponsive to monotherapy. Such combinations have been shown to enhance the therapeutic response achieved with single-agent therapy. In addition, the pharmacologic action of one of the components of the combination regimen may serve to offset side effects typically associated with the other.

Developing guidelines for local use: algorithms for cost-efficient outpatient management of cardiovascular disorders in a VA Medical Center

Local use of practice guidelines requires paying close attention to the concerns of the patient within the framework of society, to the professional and educational needs of the provider, and to the realities of cost. One Veterans Affairs facility took the challenge of balancing these factors and developed their own algorithms for three cardiovascular disorders.

Role of nitrates in angina pectoris

Nitrates are used extensively for the treatment of angina pectoris. However, continuous therapy with either oral nitrates or nitroglycerin patches leads to rapid development of tolerance, with loss or diminution of antianginal and anti-ischemic effects. The only practical way to avoid the development of tolerance is to use intermittent daily therapy with nitrates. Nitroglycerin patches applied for 10-12 hours during the day increase exercise duration for 8-12 hours, but a rebound increase in anginal attacks during the nitrate-free interval may occur. Oral isosorbide-5-mononitrate, 20 mg twice a day, with the first dose administered in the morning and the second dose 7 hours later, increases exercise duration for at least 12 hours without the development of tolerance to either the morning or afternoon dose. This dosing regimen has been shown not to produce a rebound phenomenon during the periods of low nitrate levels at night and early hours of the morning. Isosorbide dinitrate (30 mg) prescribed at 7 AM and 1 PM does not produce tolerance to the 7 AM dose, but effects of the afternoon dose have not been evaluated. Recent data suggest that isosorbide dinitrate given 3 or 4 times daily produces tolerance and this dosing schedule is inadequate for antianginal prophylaxis. It should be recognized that intermittent oral or patch therapy with nitrates during the day leaves the patient unprotected at night and early hours of the morning. If this is of concern, additional therapy with another class of antianginal agent, preferably a long-acting beta blocker or a long-acting calcium antagonist should be instituted.