The researchers used media reports from the Central Intelligence Agency archives to identify world leaders who had a CHD event while in office. Leaders included the heads of government for all countries with populations of at least 250,000. Events included angina, heart attack, or abnormal heart rhythm. The researchers determined whether the leader received treatment with bypass surgery (an operation to replace the blocked arteries), angioplasty (a procedure that opens blockages from inside), or thrombolytic therapy (drugs to dissolve the blockages). They also determined whether leaders received treatment outside their own countries and whether they returned to office after their heart attacks.