ONLINE COMPUTERIZED VECTORCARDIOGRAPHY - INFLUENCE OF BODY POSITION, HEART-RATE, RADIOGRAPHIC CONTRAST FLUID AND MYOCARDIAL-ISCHEMIA

On-line computerized vectorcardiography (cVCG) is increasingly being u sed for continuous monitoring of myocardial ischemia, however, little is known about factors other than ischemia causing electrocardiographi c abnormalities. This paper describes how three important cVCG paramet ers, STC-VM, ST-VM and QRS-VD, are affected by different body position s, myocardial ischemia, contrast injection and increasing heart rate i n patients with and without coronary artery disease. The main findings of the study are: contrast injection and different body positions cau sed major changes in QRS-VT but affected ST-VM and STC-VM to a minor d egree. Increasing heart rate by atrial pacing produced substantial cha nges in all three parameters. Ischemia during angioplasty also produce d changes in all three parameters, STC-VM being the most sensitive par ameter. In conclusion: (1) STC-VM (greater than or equal to 50 mu V) i s the most valuable parameter for monitoring ischemia; (2) we propose ST-VM greater than or equal to 50 mu V as criterion instead of previou sly used 25 mu V; (3) QRS-VD cannot be used as a single marker of isch emia, and (4) electrocardiographic changes induced by increased heart rate should be taken into account during interpretation.