This study was designed to determine if the activated partial thrombop
lastin time (aPTT) present at the end of a diagnostic cardiac catheter
ization was correlated with specific patient or procedure characterist
ics. No relationship between time from heparin bolus and the aPTT was
found. Age, weight and body surface area were found to influence the a
PTT at catheterization completion (p < 0.05). Patient sex, height, smo
king status, hematocrit, and type and volume of contrast used were not
correlated with aPTT at the end of catheterization. This suggests pos
sible usefulness of the age and weight of patients to guide the dose o
f heparin used at cardiac catheterization.