Predictors of syncope post pacemaker implantation included : age 0-39 years ( HR 2.9 , 95 % CI 1.4 to 6.3 , p = 0.01 ; reference range 60-79 years ) , age 80 years ( HR 1.4 , 95 % CI 1.0 to 1.8 , p = 0.03 ) , syncope prior to pacemaker implant ( HR 1.8 , 95 % CI 1.4 to 2.3 , p < 0.001 ) , previous myocardial infarction ( HR 1.5 , 95 % CI 1.1 to 2.1 , p = 0.03 ) , heart failure ( HR 1.4 , 95 % CI 1.0 to 1.9 , p = 0.046 ) , and high Charlson comorbidity index ( HR 1.6 , 95 % CI 1.1 to 2.2 , p = 0.01 ) .