Author + information
- Received January 25, 1993
- Revision received May 24, 1993
- Accepted June 2, 1993
- Published online November 15, 1993.
- Edward G. Cape, PhDa,∗,
- Young H. Kim, PhDa,∗,
- Russell S. Heinrich, BSa,∗,
- Randall Y. Grimes, MDa,∗,
- Ethirajan Muralidharan, PhDa,∗,
- Jonathan D. Broder, BSa,
- Ehud Schwammenthal, MDa,†,
- Ajit P. Yoganathan, PhDa,∗ and
- Robert A. Levine, MD, FACCa,†,1
- ↵∗Address for correspondence: Dr. Edward G. Cape, Division of Pediatric Cardiology, Children's Hospital of Pittsburgh. University of Pittsburgh, 3705 Fifth Avenue, Pittsburgh, Pennsylvania 15213.
Objectives. This study addressed the hypothesis that motion of the surface containing a regurgitant orifice relative to the Doppler ultrasound transducer can cause differences between actual flow rate and calculations based on the proximal flow convergence
Background. In vitro studies quantising regurgitant flow rate by proximal flow convergence have been limited to stationary orifices, Clinically, however, valve leaflets generally move relative to the ultrasound transducer during the cardiac cycle and can move at velocities important relative to the measured color aliasing velocities. The transducer therefore senses the vector sum of actual flow velocity toward the orifice and orifice velocity relative to the transducer. This can cause potential overestimation or underestimation of true flow rate, depending on the direction of surface motion.
Methods. The hypothesis was explored computationally and tested by pumping fluid at a constant flow rate through an orifice in a plate moving at 0 to 8 cm/s (velocities comparable to those described clinically for mitral and tricuspid annulus motion toward an apical transducer).
Results. Surface motion in the same direction as flow caused over-estimation of the aliasing radius and calculated flow rate. Surface motion opposite to the direction of flow (typical for mitral and tricuspid regurgitation viewed from the apex or esophagus) caused underestimation of actual flow rate. The underestimation was greater for lower aliasing velocities (36 ± 11% for 10 cm/s vs. 23 ± 6% for 20 cm/s). Correcting for surface motion provided excellent agreement with actual values (y = 0.97x + 0.10, r = 0.99, SEE = 0.17 liters/min).
Conclusions. Physiologic motion of the surface containing a regurgitant orifice can cause substantial differences between actual flow rate and that calculated by the proximal flow convergence technique. Low aliasing velocities used to optimize that technique can magnify this effect. Such errors can be minimized by using higher aliasing velocities (compatible with the need to measure the aliasing radius) or eliminated by correcting for surface velocity determined by an M-mode ultrasound scan.
↵1 Dr. Levine is an Established Investigator of the American Heart Association, Dallas, Texas.
☆ This study was supported by Grants RO1 HL 45485 and R29 HL 33176 from the National Heart, Lung, and Blood Institute. National Institutes of Health, Bethesda, Maryland and a grant-in-aid from the American Heart Association, Dallas, Texas, with funds contributed in part by its Massachusetts Affiliate, Needham, Massachusetts.
- Received January 25, 1993.
- Revision received May 24, 1993.
- Accepted June 2, 1993.