Basis for detection of stenosis using venous administration of microbubbles during myocardial contrast echocardiography: bolus or continuous infusion?
OBJECTIVE
This study sought to determine the basis of detection of stenosis by myocardial contrast echocardiography using venous administration of microbubbles and to define the relative merits of bolus injection versus continuous infusion.


BACKGROUND
The degree of video intensity (VI) disparity in myocardial beds supplied by stenosed and normal coronary arteries can be used to quantify stenosis severity after venous administration of microbubbles. However, the comparative merits of administering microbubbles as a bolus injection or continuous infusion has not been studied.


METHODS
Coronary stenoses of varying severity were created in either the left anterior descending or the left circumflex coronary artery in 18 dogs. Imagent US (AF0150) was given as a bolus injection in 10 dogs (Group I) and as both a bolus injection and a continuous infusion in 8 dogs (Group II). For bolus injections, peak VI was derived from time-intensity plots. During continuous infusion, microbubble velocity and microvascular cross-sectional area were derived from pulsing interval versus VI plots. Myocardial blood flow (MBF) was determined using radiolabeled microspheres.


RESULTS
During hyperemia, VI ratios from the stenosed versus normal beds correlated with radiolabeled microsphere-derived MBF ratios from those beds for both bolus injections (r = 0.81) and continuous infusion (r = 0.79). The basis for detection of stenosis common to both techniques was the decrease in myocardial blood volume distal to the stenosis during hyperemia. The advantage of continuous infusion over bolus injection was the abolition of posterior wall attenuation and the ability to quantify MBF.


CONCLUSIONS
Both bolus injection and continuous infusion provide quantitative assessment of relative stenosis severity. Compared with bolus injection, continuous infusion also allows quantification of MBF and data acquisition without attenuation of any myocardial bed.
Cardiovascular Division, University of Virginia School of Medicine, Charlottesville 22908, USA.
K
K
Wei
A R
AR
Jayaweera
S
S
Firoozan
A
A
Linka
D M
DM
Skyba
S
S
Kaul
D000818:Animals; D003287:Contrast Media / Q000008:administration & dosage*; D003326:Coronary Circulation / Q000502:physiology; D003327:Coronary Disease / Q000000981:diagnostic imaging*; D004285:Dogs; D004452:Echocardiography; D005466:Fluorocarbons; D006940:Hyperemia / Q000000981:diagnostic imaging; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D012680:Sensitivity and Specificity
D003287:Contrast Media; D005466:Fluorocarbons; C099091:Imagent US