LSI Logic Corp chairman, British-born Wilf Corrigan, is taking medical leave of absence from the Milpitas company he founded: he has to have bypass surgery this months, but hopes to be back at the firm in as little as 12 weeks; LSI says reassuringly that bypass surgery is a commonly performed procedure to increase the flow of blood to the heart, and over the past several years, has been performed on hundreds of thousands of individuals, who typically return to normal activities within a few months; Corrigan, 51, expects to participate in management decisions while he is recuperating, and has formed an Office of the Chief Executive with George Wells, president and chief operating officer, and the two will jointly make operating and strategic decisions affecting the firm.