Yeltsin Has 7-Hour Heart Surgery And Doctors Say It Was a Success
Russian Pres Boris Yeltsin undergoes seven-hour, multiple-bypass heart operation in Moscow which doctors declare success; surgeons sew five grafts to restore blood flow to coronary arteries, blocked by fatty deposits of atheriosclerosis; are optimistic about Yeltsin's chances of resuming full workload; Yeltsin reported in stable condition in intensive care unit; signed decree prior to operation reassuming presidential powers, delegated hours before to Prime Min Viktor S Chernomyrdin; diagram (M)