ABCs of Prescribing Antianginal Therapy in Chronic Stable Angina
Chronic stable angina is a common condition in older patients. Although lifestyle modifications such as weight loss, smoking cessation, and risk factor control remain fundamental components of the management strategy, pharmacological agents are necessary to prevent and control anginal symptoms. Sublingual nitroglycerin (either as tablets or a spray) is the most effective agent to terminate an episode of anginal pain. Anginal frequency and exercise tolerance are improved with beta-adrenergic blockers, calcium channel blockers, and long-acting nitrate preparations. A strategy for the optimal use of these agents both alone and in combination is discussed.
Key words: angina pectoris, nitrates, beta-blockers, calcium channel blockers.
Chronic stable angina is usually the consequence of atherosclerotic narrowing of the coronary arteries. The arterial narrowing results in a reduced ability for coronary blood flow to increase when the metabolic demands of the heart are greater, such as when the patient exerts. It is the imbalance between an inadequate blood supply for myocardial oxygen needs that causes myocardial ischemia. Myocardial ischemia can provoke the symptoms of angina pectoris or occur without symptoms (silent ischemia). In addition, myocardial ischemia can cause atypical symptoms that are not immediately recognized as being due to coronary heart disease.1 The older patient with chronic ischemic heart disease may develop typical symptoms of angina pectoris, such as retrosternal chest pain provoked by exertion (with radiation to the jaw or arms) and relief from both rest and the use of sublingual nitroglycerin. Yet many older patients with myocardial ischemia do not develop chest discomfort as their principal symptom but instead complain of dyspnea. If pressed, they will admit to having a mild chest discomfort in association with the dyspnea. The absence of anginal chest pain in older patients with myocardial ischemia has been attributed to their limited exertional capacity.
The goals of treatment of the older patient with angina are to relieve symptoms, reduce the risk of fatal and non-fatal myocardial infarction, and identify high-risk patients who may have a better outcome with coronary revascularization. Drug therapy to reduce the frequency of anginal pain is a small, albeit important, part of the initial management of the patient with angina (Table 1).2
The older patient with stable angina pectoris should have a risk assessment to identify high-risk individuals who may benefit from coronary artery revascularization by either percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) at an early stage. A full medical history and physical examination are necessary to identify high-risk individuals as well as factors that may have aggravated or provoked the onset of angina.
Lifestyle modification (such as cessation of cigarette smoking and weight loss) and recognition of predisposing factors (such as anemia, aortic stenosis, or uncontrolled atrial fibrillation) may eliminate the need for antianginal medications. Furthermore, it is important to initiate risk factor modification (such as blood pressure control and cholesterol lowering medication) and other measures (such as acetylsalicylic acid [ASA]3,4 and angiotensin-converting enzyme [ACE] inhibition) that have proven benefit in the prevention of fatal and nonfatal myocardial infarction and stroke.
Antianginal therapy aims to increase the threshold where the imbalance between myocardial oxygen demands exceeds the supply (Figure 1). Medications such as nitroglycerin favourably restore the balance by reducing oxygen demands as a consequence of venodilatation and the resulting reduction of left ventricular volume. A smaller heart has lesser energy demands. Vasodilating the larger coronary arteries, and