Patients with unstable angina should be hospitalized immediately for both therapy and diagnosis. Therefore, a differential diagnosis between angina and other conditions is made when such symptoms occur. In fact a 12-lead ECG recorded at rest in the absence of pain is normal in about half of the patients with typical angina. However, an ECG taken in the presence of pain may yield a great deal more information because it may document the presence of transient ST segments depression, a characteristic sign of subendocardial ischemia. Several studies have correlated findings from the exercise ECG with the presence or absence of significant obstruction of the coronary arteries with findings with angiography.
Variant angina is due to coronary artery spasm.
The spasm usually occurs very close to the obstruction. The ergonovine test is the most sensitive test for coronary artery spasm. Ergonovine is introduced to induce coronary spasm. Hyperventilation and coronary injections of acetylcholine are other means used to induce variant angina. Radioisotope imaging is a viable procedure for diagnosing coronary artery disease.