The diagnostic accuracy, safety and tolerance of adenosine thallium sc
intigraphy have been reported using a 2-site intravenous infusion with
either a titrated or fixed-dose protocol. A single-site infusion woul
d considerably simplify the test procedure, but its safety must be est
ablished before it can be recommended. Accordingly, 400 consecutive pa
tients who had adenosine and thallium-201 administered through the sam
e intravenous line were classified into 2 groups. Group I (n = 201) pa
tients received a 7-minute titrated intravenous infusion of adenosine,
with an initial dose of 50 mug/kg/min that increased at 1-minute inte
rvals to a maximum of 140 mug/kg/min. Group II (n = 199) patients rece
ived a fixed dose of adenosine at 140 mug/kg/min for 6 minutes. Adenos
ine significantly (p < 0.001) increased heart rate and decreased systo
lic blood pressure by similar amounts in both groups. Adverse effects
occurred more often (88 vs 71%, p < 0.001) and started earlier (2.8 vs
3.6 minutes, p < 0.001) in group II. There was no significant differe
nce in the occurrence of second- and third-degree atrioventricular blo
ck between the 2 groups (4.0 vs 5.0 %); however, chest pain, flushing
and nausea were all more frequent in group II. Severe side effects wer
e seldom seen in either group and occurred in 9 group I and 8 group II
patients. Scintigraphic findings were similar in both groups. Transie
nt perfusion defects were seen more often in patients with than withou
t second- or third-degree atrioventricular block (42 vs 21%, p < 0.05)
. Despite a high frequency of side effects for both the fixed dose and
stepwise infusion regimens, adenosine and thallium administration thr
ough a single intravenous site is safe and well-tolerated.