Relationship between quantitative and descriptive methods of studying blood flow through intrapulmonary arteriovenous anastomoses during exercise

Several methods exist to study intrapulmonary arteriovenous anastomoses (IPAVA) in humans. Transthoracic saline contrast echocardiography (TTSCE), i.e., bubble scores, is minimally-invasive, but cannot be used to quantify the magnitude of blood flow through IPAVA (Q_IPAVA). Radiolabeled macroaggregates of albumin (^99mTc-MAA) have been used to quantify Q_IPAVA in humans, but this requires injection of radioactive particles. Previous work has shown agreement between ^99mTc-MAA and TTSCE, but this has not been tested simultaneously in the same group of subjects. Thus, the purpose of this study was to determine if there was a relationship between Q_IPAVA quantified with ^99mTc-MAA and bubble scores obtained with TTSCE. To test this, we used ^99mTc-MAA and TTSCE to quantify and detect Q_IPAVA at rest and during exercise in humans. Q_IPAVA significantly increased from rest to exercise using ^99mTc-MAA and TTSCE and there was a moderately-strong, but significant relationship between methods. Our data suggest that high bubble scores generally correspond with large Q_IPAVA quantified with ^99mTc-MAA during exercise.