Imaging of adenosine bolus transit following intravenous administration: insights into antiarrhythmic efficacy.
OBJECTIVE
To study the effects of the site of intravenous injection of adenosine and to assess the site of action of adenosine in the heart by correlating cardiac effects with bolus transit.


METHODS
Ten patients undergoing routine technetium (Tc-99m) gated blood pool ventriculography consented to the coadministration of intravenous adenosine. The dose of adenosine required to produce heart block during sinus rhythm was determined following antecubital vein administration. This dose (6-18 mg) was mixed with Tc-99m and given first into the same antecubital vein (proximal injection) and then repeated into a hand vein (distal injection). The ECG was recorded and the transit of the bolus was imaged using a gamma camera.


RESULTS
Heart block occurred in all 10 patients (second degree in seven, first degree in three) at (mean (SEM)) 17.5 (1.0) seconds after the proximal injection of adenosine. Distal injection produced heart block in six patients (second degree in two, first degree in four) at 21.9 (4.4) seconds (p < 0.01). In eight of 10 patients the electrophysiological effects were less with distal injection. The onset of heart block was close to the time of peak bolus Tc-99m activity in the left ventricle. Peak bolus activity was delayed (by about three seconds) and the duration of bolus activity in the left ventricle was increased with distal injection compared with proximal injection, at 17.2 (4.2) v 9.2 (3.1) seconds, p < 0.01.


CONCLUSIONS
The lesser electrophysiological effects of adenosine following distal intravenous injections were associated with delay in transit time and dispersion of the bolus. The correlation of adenosine induced heart block with bolus activity in the left heart indicated dependence on coronary arterial delivery of adenosine to the atrioventricular node.
Department of Medical Cardiology, Royal Infirmary, Glasgow G31 2ER, Scotland, UK.
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D000241:Adenosine / Q000008:administration & dosage* / Q000493:pharmacokinetics; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D001283:Atrioventricular Node / Q000187:drug effects; D001692:Biological Transport; D003331:Coronary Vessels; D004562:Electrocardiography; D015637:Gated Blood-Pool Imaging; D006327:Heart Block / Q000139:chemically induced* / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008875:Middle Aged; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D013667:Technetium / Q000008:administration & dosage; D013997:Time Factors
D000889:Anti-Arrhythmia Agents; D019275:Radiopharmaceuticals; D013667:Technetium; D000241:Adenosine