I have fairly advanced heart disease and peripheral artery disease, do i need any special arrangements during a long commercial flight?

Depends on disease: You should not fly at all if you have unstable angina (resting or worsening chest pain or trouble breathing or symptoms that your doctor has said are heart failure), abnormal heart rhythms, or heart failure bad enough that you are unable to perform everyday activities. Otherwise, if your oxygen saturation is 95% or less at rest, you should wear oxygen during the flight if you have heart disease.

Heart disease and PA: If you have advanced disease, you will need to be assessed by your cardiologist to see what arrangements you might need. A lot depends on how stable your heart disease is.