Chronic Stable Angina
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Angina pectoris, the most common clinical manifestation of coronary artery disease (CAD), results from an imbalance between myocardial O2 supply and demand, most often due to atherosclerotic coronary artery obstruction. Other major conditions that upset this balance and result in angina include aortic valve disease (Chap. 114), hypertrophic cardiomyopathy (Chap. 115), and coronary artery spasm (see below).
Angina is typically associated with exertion or emotional upset; relieved quickly by rest or nitroglycerin (Chap. 31). Major risk factors are cigarette smoking, hypertension, hypercholesterolemia (↑LDL; ↓HDL), diabetes, obesity, and family history of CAD before age 55.
Often normal; arterial bruits or retinal vascular abnormalities suggest generalized atherosclerosis; S4 is common. During acute anginal episode, other signs may appear: e.g., an S4, diaphoresis, rales, and a transient murmur of mitral regurgitation due to papillary muscle ischemia.
May be normal between anginal episodes or show old infarction (Chap. 111). During angina, ST- and T-wave abnormalities typically appear (ST-segment depression reflects subendocardial ischemia; ST-segment elevation may reflect acute infarction or transient coronary artery spasm). Ventricular arrhythmias frequently accompany acute ischemia.
Enhances diagnosis of CAD (Fig. 121-1). Exercise is performed on treadmill or bicycle until target heart rate is achieved or pt becomes symptomatic (chest pain, light-headedness, hypotension, marked dyspnea, ventricular tachycardia) or develops diagnostic ST-segment changes. Useful information includes duration of exercise achieved; peak heart rate and bp; depth, morphology, and persistence of ST-segment depression; and whether and at which level of exercise pain, hypotension, or ventricular arrhythmias develop. Exercise testing with radionuclide, echocardiographic, or magnetic resonance imaging increases sensitivity and specificity and is particularly useful if baseline ECG abnormalities prevent interpretation of test. Note: Exercise testing should not be performed in pts with acute MI, unstable angina, or severe aortic stenosis. If the pt is unable to exercise, pharmacologic stress with IV dipyridamole, adenosine, regadenoson, or dobutamine can be performed in conjunction with radionuclide or echocardiographic imaging. (Table 121-1). Pts with LBBB on baseline ECG should be referred for adenosine or dipyridamole radionuclide imaging, which is most specific for diagnosis of CAD in this setting.
The prognostic utility of coronary calcium detection (by electron-beam or multidetector CT) in the diagnosis and management of CAD has not yet been fully defined.
|Pt able to exercise|
|If baseline ST-T on ECG is normal||Standard exercise test (treadmill, bicycle, or arm ergometry)|
|If baseline ST-T impairs test interpretation (e.g., LVH with strain, digoxin)|
Standard exercise test (above) combined with either
Perfusion scintigraphy (thallium-201, 99mTc-sestamibi) or
|Pt not able to exercise (regardless of baseline ST-T abnormality)||Pharmacologic stress test (IV dobutamine, dipyridamole, or adenosine) combined with imaging:|
|Perfusion scintigraphy [thallium 201, 99mTc-sestamibi, or PET (rubidium-82 or N-13 ammonia)] or|
|LBBB on baseline ECG||Adenosine (or dipyridamole) 99mTc-sestamibi or PET scintigraphy|
Some pts do not experience chest pain during ischemic episodes with exertion (“silent ischemia”) but are identified by transient ST-T-wave abnormalities during stress (see below).
The definitive test for assessing severity of CAD; major indications are (1) angina refractory to medical therapy, (2) markedly positive exercise test (≥2-mm ST-segment depression, onset of ischemia at low workload, or ventricular tachycardia or hypotension with exercise) suggestive of left main or three-vessel disease, (3) recurrent angina or positive exercise test after MI, (4) to assess for coronary artery spasm, and (5) to evaluate pts with perplexing chest pain in whom noninvasive tests are not diagnostic.
The role of newer noninvasive coronary imaging techniques (CT and MR angiography) continues to be defined.