Senator Mike Duffy this morning wrote the Speaker of the Senate Noel Kinsella, explaining the reason for Senator Duffy's absence from the chamber during the Speech from the Throne. The letter read in part:Dear Sir:I am writing to bring you up to date on my health status.When I had open heart surgery in 2006, they found 3 blockages. Because of  bleeding, broken ribs and various complications, they ended up fixing the main problem, but did not want to keep me on the table longer to fix the other 2 blocked vessels. They suggested that surgery could come later.At the end of August this year I suffered unstable angina at home on PEI, and spent 2.5 days in the QEH.On examination here this week, my Ottawa GP fears the disease has progressed. He is suggesting immediate tests. My GP suggests that to avoid further stress on my system, I stay off work until I get the all-clear from my medical team.Yours truly,Hon. Mike Duffy,Senator, Cavendish PEI