You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Dwight_D._Eisenhower

Context:
The last three years of Eisenhower's second term in office were ones of relatively good health. Eventually after leaving the White House, he suffered several additional and ultimately crippling heart attacks. A severe heart attack in August 1965 largely ended his participation in public affairs. In August 1966 he began to show symptoms of cholecystitis, for which he underwent surgery on December 12, 1966, when his gallbladder was removed, containing 16 gallstones. After Eisenhower's death in 1969 (see below), an autopsy unexpectedly revealed an adrenal pheochromocytoma, a benign adrenaline-secreting tumor that may have made the President more vulnerable to heart disease. Eisenhower suffered seven heart attacks in total from 1955 until his death.

Question:
How many heart attacks did Eisenhower have between 1955 and 1969?

seven