Serious complications, such as myocardial infarction or death, may occur particularly in patients with severe coronary heart disease during coronary angiographies. Therefore, prediction of severe coronary heart disease before or during the initial steps of the procedure can provide a decrease in frequency of such complications. To predict the Seriousness of coronary heart disease during left ventriculography, before, during, and after the application of contrast matter, electrocardiography (ECG) records were taken and R-wave amplitudes were measured. Lead D11 was used for calculations. The patients were classified according to vessel lesions and were compared with the control group. Before and after left ventriculography, there was no significant difference between the groups with normal coronary arteries and one, two, or three vessel lesions. Although there was no significant difference obtained from the comparison of the control group and the groups with one-vessel and two-vessel lesions (9.7 mm, 9.2 mm, 10.1 mm, respectively, P > 0.05); there was statistical difference between the group with three-vessel lesions and the control group during left ventriculography (6.4 mm, 9.7 mm, respectively, P < 0.05). Nonionic contrast material was used in all procedures. The decrement of R-wave amplitude that is observed during left ventriculography can predict three-vessel disease, which is a more serious condition for the patients. These patients should be monitored more carefully during coronary angiographies.