In addition to Hill's illness, Lee's performance was affected by heart troubles, which would eventually lead to his death in 1870; he had been diagnosed with pericarditis by his staff physicians in March 1863, though modern doctors believe he had in fact suffered a heart attack. He wrote to Jefferson Davis that his physical condition prevented him from offering full supervision in the field, and said, "I am so dull that in making use of the eyes of others I am frequently misled."