It was the fall of 1996, and Boris N. Yeltsin was running for re-election as Russia’s first president in the post-Soviet era. But he faced a crisis far more threatening than any opponent: he was desperately ill. Mr. Yeltsin had had a heart attack. He was experiencing chest pain from angina. He needed a coronary bypass operation. But his Russian doctors said he could not survive such surgery. For independent advice, Mr. Yeltsin reached out to an American doctor as renowned in Russia as he was in the United States: Dr. Michael E. DeBakey, the pioneering Houston heart surgeon. Dr....