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SUMMARY To determine the independent influence of the extent and site of residual disease on late survival, we analyzed the fate of 1448 consecutive patients who had coronary artery bypass surgery during [1968][1969][1970][1971][1972][1973][1974] residual disease itself is an important independent variable affecting survival and, if so, to determine the influence on survival of the varying extent and site of residual disease.Materials and Methods A residual lesion was defined as the presence of a luminal stenosis causing more than a 70% reduction in diameter in a major coronary artery without a bypass graft attached distal to it. For example, a patient with two-vessel disease who had received two grafts was classified as having no residual disease, whereas if only one graft had been placed, one residual lesion was considered present. Thus, residual disease could consist either of small or diffusely diseased vessels that were inoperable or of vessels of good size, suitable for grafting, that were not operated upon. Because all of the patients in this study were referred, evaluated and operated upon by one cardiology group and surgeon in the same institution using constant surgical techniques, the prevalence of truly ungraftable vessels was assumed to be constant throughout the period of this study. All

ECEST interest in the use of ferrate compounds as strong ' oxidizing agents prompted an investigation of some factors influencing the stability of potassium ferrate solutions. In a study of the st,ahility of ferrate ions in aqueous solutions, Schreyer and Ockerman (2j found that the more dilute solutions of ferrate are more stable. They found also that some added salts, after increasing the initial deconiposition rate of ferrate solutions, apparently staliiljze the remainder; and that ferrate ions are more stable in buffer solutions of p H 8 than those of pH 7. These authors believe that the major factor influencing stability is the alkalinity of the solution. From qualitative experiments Schreyer ( 1 ) reported that solutions of potassium ferrate were partially decomposed photochemically over a period of 9.5 hours.Since it seemed desirable to establish the factors influencing the stability of ferrate compounds in connection with other xork, a quantitative study of t,he effects of light, temperature, alkalinity, and concentration, on the decomposition of aqueous solutions of potassium ferrate was made under carefully controlled conditions. PROCEDUREThe potassium ferrate was prepared by the method reported by Thompson, Ockerman, and Schreyer (4). To determine the effect of light on the decomposition rate of solutions of potassium ferrate under varying conditions, each of the experiments described below was performed using identical solutions in three flasks placed in a thermostat. One flask was exposed to the daylight in the laboratory, one was placed in the path of a beam of light from a 150-m-att G.E. spotlight, and one was painted black to exclude light. The latter was fitted with a rubber stopper containing a release valve to permit the escape of oxygen.As it was impossible to maintain a constant temperature with the splotlight shining directly on the bath, a 3000-ml. beaker of water was inserted between the bath and the spotlight to absorb most of the heat radiation. In this manner the temperature was successfully maintained constant to within +O.l O C.The solutions were analyzed by pipetting 10-ml. portions and determining the ferrate concentration by the chromite method ( 3 ) . Analyses were performed at varying intervals over a 2-hour period after the potassium ferrate solutions were prepared.Preliminary experiments indicated that several factors such as stirring, vibrations, and exposure of dry samples to the atmosphere influenced the decomposition. To minimize these factors the solutions were not stirred, and every effort was made to maintain constant conditions except for the one condition varied in 1 Present address, University of Cincinnati, Cincinnati, Ohio. rvlc each series of experiments. obtained.In this way reproducible rcwults were RESULTSEffect of Temperature. To study the effect of temperature on stability, quantitative determinations 15-ere made on aqueous solutions of potassium ferrate at' temperatures of 25' and 0.5' C. The results in Figure 1 shox that at 25" C. the concentration of potass...

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