Fig. 1

Continuous electrocardiography in a patient with an anginal attack.
Elctrocardiography is presented by means of superimposed electrocardiogram: 20 superimposed blocked waves per 5 min, comprising superimposed averaged electrocardiographic waves per 15 s block. Data were analyzed using SCM-6000（Fukuda Denshi, Chiba City, Japan）.
A. Before angina attack（12:15-12:20 hours）.
B. Initiation of ST segments depression（12:20-12:25 hours）.
C. Experiencing angina attack and taking a nitrate sublingually（12:25-12:30 hours）.
D. Chest pain ceasing with ST segments returned to baseline（12:30-12:35 hours）.