In order to study the effects of residual stenosis on myocardial salvage, we created 99% coronary stenosis with or without contrast washout delay at reperfusion in six groups of dogs. In Group A (n = 8), the artery was occluded for 1h before being fully reperfused. In Group B (n = 9), the artery was occluded for 1h, then subjected to 6h of 99% stenosis without contrast washout delay. In Group C (n = 8), the artery was occluded for 1h, followed by 1 week of 99% stenosis without contrast washout delay. In Group D (n = 10), again the artery was occluded for 1h, then subjected to 6h of 99% stenosis with contrast washout delay. In Group E (n = 8), the artery was occluded for 7h, then fully reperfused for 1 week. Finally, in Group F (n = 8), the occlusion lasted for a full week. All dogs were sacrificed 1 week after occlusion. In Group A, myocardial creatine phosphokinase activity (CK) in the inner layer was 43.8 +/- 12.5% that of non-infarcted myocardium. Myocardial CK in Group B (46.5 +/- 7.4%) was little different but in Group C it dropped to 26.6 +/- 8.4%, suggesting that 99% residual stenosis is not deleterious if it is continued for 6h or less but that it will result in considerable depletion of myocardial CK, it is is sustained for 1 week. In Group D, myocardial CK dropped markedly to 11.3 +/- 3.7%, little different from that for either Group E (13.3 +/- 2.6%) or Group F (9.3 +/- 3.3%).(ABSTRACT TRUNCATED AT 250 WORDS)