Chronic stable angina pectoris

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.

Intensity of antianginal therapy in patients referred for coronary angiography: a comparison of fee-for-service and health maintenance organization therapeutic strategies

BACKGROUND

No formal criteria have been developed to guide medical therapy for angina prior to revascularization, and no comparisons have been made between health maintenance organization (HMO) and fee-for-service (FFS) hospitals with respect to angina treatment.

HYPOTHESIS

Using a literature-based measure of medical intensity, we tested the hypothesis that there is no difference in anginal medical therapeutic intensity between HMO and FFS systems.

METHODS

For each antianginal drug, we developed a model from which an intensity score between 0 and 100 could be calculated. Average and maximal daily doses of drug were fit to a sigmoid curve such that they represented scores of 50 and 99, respectively. Overall intensity scores were obtained by weighted and unweighted averaging of three scores from nitrates, calcium-channel blockers, and beta blockers. This model was applied to 199 patients undergoing angiography at an FFS and an HMO hospital.

RESULTS

HMO patients were taking more classes of antianginal drug (1.9 vs. 1.0, p < 0.001). Overall unweighted (17.7 vs. 11.7, p = 0.02) and weighted (27.3 vs. 16.9, p = 0.003) intensity scores for both HMO and FFS patients were low. HMO intensity scores for the use of beta blockers were greater than FFS scores (19.2 vs. 9.6, p = 0.002). The intensity scores for the use of nitrates and calcium blockers were similar.

CONCLUSIONS

Models for the measurement of anginal medical therapy intensity can provide important information regarding medical therapy prior to revascularization. The overall intensity of medical therapy was low in both health care systems. These findings have important implications for patient management, guideline development, and national healthcare policy.

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.

Does withdrawal of antihypertensive medication increase the risk of cardiovascular events? Trial of Nonpharmacologic Interventions in the Elderly (TONE) Cooperative Research Group

The Fifth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure recommends that attempts to discontinue antihypertensive drug therapy be considered after blood pressure (BP) has been controlled for 1 year. However, discontinuation of drug therapy could unmask underlying conditions and precipitate clinical cardiovascular events. The Trial of Nonpharmacologic Interventions in the Elderly (TONE) was a clinical trial of the efficacy of weight loss and/or sodium reduction in controlling BP after withdrawal of drug therapy in patients with a BP< 145/85 mm Hg on 1 antihypertensive medication. Of 975 participants, 886 entered the drug withdrawal phase of the trial and 774 were successfully withdrawn from their medications. Thirty-three events (stroke, transient ischemic attack, myocardial infarction, arrhythmia, congestive heart failure, angina, other) occurred between randomization and the onset of drug withdrawal (median time 3.6 months), 57 events occurred either during or after drug withdrawal (14.0 months), and 36 events occurred after resumption of antihypertensive therapy (15.9 months). Event rates per 100 person-years were 5.5, 5.5, and 6.8 for the 3 time periods (p=0.84) in the nonoverweight group and 7.2, 5.2, and 5.6 (p=0.08) in the overweight group. The study shows that antihypertensive medication can be safely withdrawn in older persons without clinical evidence of cardiovascular disease who do not have diastolic pressure > or = 150/90 mm Hg at withdrawal, providing that good BP control can be maintained with nonpharmacologic therapy.

Role of endothelial dysfunction in coronary artery disease

The vascular endothelium plays an essential role in regulating blood flow and other functions of the coronary arteries. Under normal conditions, the endothelium releases a number of factors that regulate arterial vasomotion. One of these factors, endothelial-derived relaxing factor (EDRF), is a vasorelaxant that is identical to, or closely related to, nitric oxide (NO). Endothelial function may be compromised in coronary artery disease (CAD) or in the presence of risk factors for CAD. In this setting, EDRF-NO activity is inhibited, which may lead to vasoconstriction, platelet aggregation, vasospasm, and thrombosis. The relation between endothelial function, arterial vasomotion, and myocardial ischemia is discussed, with particular emphasis on the role of EDRF-NO, and the therapeutic interventions that may be useful in treating the clinical consequences of endothelial dysfunction.

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.