Evaluation of operative left ventricular outflow tract lesions with a fluid impedance plot.

A hydraulic fluid impedance plot is produced by plotting instantaneous differential pressure against phasic blood flow across a vascular segment. This simple plot quantitatively and compactly describes the changes in flow resistance (impedance) throughout the entire cardiac cycle. Impedance plots were obtained before and after corrective surgery in patients with a variety of left ventricular outflow tract and aortic valve lesions. Although present techniques are still limited, impedance plots now provide quantitative measurement of flow resistance throughout the cardiac cycle in a variety of cardiac and great vessel lesions.