President Roosevelt’s medical records were closely guarded during his lifetime and surviving documentation is incomplete. But it’s clear he had persistently severe high blood pressure in the 1940s. In late 1943 he apparently had congestive heart failure (CHF) and his health declined significantly.
In April 1944 his blood pressure was recorded as extremely high (218/130). Unfortunately at that time (unlike today) no medications were available to effectively treat hypertension. The only recommendations were to avoid stress and vigorous activity, eat a sensible diet and avoid tobacco use.
In the summer of 1944, during the campaign for an unprecedented 4th term, several physicians collectively reported that FDR was in good health. One of them however, Frank Lahey of Boston, wrote a confidential memo that suggested the president might not survive another four years. The public never learned of his assessment, and in April 1945 Roosevelt succumbed to a stroke just three months into his fourth term.