Detection and quantification of small right-to-left shunts by the phase-plane method

Area of Science:

• Cardiovascular Physiology
• Diagnostic Imaging Techniques

Background:

• Right-to-left shunts are critical cardiovascular abnormalities.
• Accurate detection and quantification of shunts are essential for patient management.

Purpose of the Study:

• To evaluate the utility of phase-plane analysis for detecting and quantifying right-to-left shunts.
• To compare phase-plane measurements with standard indicator-dilution and oximetric methods.

Main Methods:

• Indicator-dilution curves and phase-plane plots were recorded in anesthetized dogs.
• Indocyanine green was injected into the superior vena cava and sampled from the femoral artery.
• Surgically produced right-to-left shunts were used to compare methods.

Main Results:

• Phase-plane measurements showed good correlation with standard indicator-dilution procedures (r = 0.890).
• Correlation with oximetry was less robust (r = 0.466).
• Phase-plane analysis detected alterations indicative of shunts more clearly than concentration-vs.-time curves.

Conclusions:

• Phase-plane analysis is a valuable tool for detecting and evaluating right-to-left shunts.
• The method demonstrates superior sensitivity in identifying small shunts compared to traditional curves.
• Phase-plane loops provide distinct alterations for shunt detection.