Coronary angiography with Renografin 76 (RG76) occasionally results in ventricular fibrillation (VF). Angiovist 370 (AV370) is a contrast medium similar to RG76 except the calcium-sequestering agents, sodium citrate and EDTA in RG76 have been replaced by calcium EDTA. To determine whether these sequestering agents contribute to contrast medium-induced VF, a comparison was made of the effects of intracoronary injections of RG76, AV370, and saline solutions containing sodium citrate and EDTA (CIT/EDTA) and calcium EDTA (CA EDTA) on myocardial conduction, local QT intervals, and incidence of spontaneous and induced VF in 32 dogs. Four milliliters of RG76 produced a 111 +/- 12-ms increase in local QT intervals, compared with a 73 +/- 8-ms increase with AV370 (p less than 0.001). Spontaneous VF occurred in 12 of 16 six-milliliter injections of RG76, compared with 4 of 16 injections of AV370 (p less than 0.02) An early-cycle premature impulse applied after every fourth beat induced VF in 15 of 16 four-milliliter injections of RG76 compared with 5 of 16 injections of AV370 (p less than 0.01). As the premature beat conducted through the left anterior descending region, conduction slowing and fractionation occurred, which was less with AV370 than with RG76. The CIT/EDTA solution produced a greater increase in QT intervals (77 +/- 5 ms) than the CA EDTA solution (29 +/- 3 ms) or 0.9% saline solution alone (28 +/- 2 ms) (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)