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Inadequacy of the Gorlin formula for predicting prosthetic valve area
S R Cannon1, K L Richards, M H Crawford
1Utah State University, Logan 84322.
Insights
The Gorlin formula inaccurately estimates prosthetic aortic valve area, potentially leading to incorrect clinical decisions regarding aortic stenosis. This study found significant discrepancies between Gorlin formula predictions and actual valve areas in patients with mechanical valves.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Clinical Cardiology
Background:
- Prosthetic aortic valves are commonly implanted to treat aortic valve disease.
- Accurate assessment of prosthetic valve area is crucial for patient management.
- The Gorlin formula is a widely used method for estimating valve area.
Purpose of the Study:
- To determine the accuracy of the Gorlin formula in estimating the area of prosthetic aortic valves.
- To compare Gorlin formula-derived valve areas with independently verified actual valve areas.
Main Methods:
- Studied 135 male patients 6 months post-aortic valve replacement with Hancock, modified Hancock, or Bjork-Shiley prostheses.
- Compared catheterization-derived Gorlin valve areas with actual valve areas measured via pulse duplicator and direct calculation.
- Analyzed correlation and error magnitude between Gorlin and actual valve areas.
Main Results:
- Gorlin valve areas showed poor correlation with actual valve areas (r = 0.39).
- The mean error in Gorlin formula estimation was 0.36 cm2.
- Significant overestimation (>0.25 cm2) occurred in 32% of patients, and underestimation in 21%.
Conclusions:
- The Gorlin formula is inaccurate for predicting prosthetic aortic valve area.
- Overreliance on the Gorlin formula may lead to erroneous clinical decisions in patients with aortic stenosis.
- Re-evaluation of assessment methods for prosthetic aortic valve function is warranted.
Abstract:
A total of 135 patients with normally functioning prosthetic aortic valves who were catheterized 6 months after placement of Hancock, modified Hancock or Bjork-Shiley prostheses were studied to determine the magnitude of error in Gorlin formula estimates of prosthetic aortic valve area. All patients were male, selected from 13 participating hospitals and routinely followed after valve replacement for 5 years. Hemodynamically determined Gorlin valve areas were compared with independently verified actual valve areas. Actual Hancock areas were measured from videotapes of valves exercised in a pulse duplicator flow model. Actual Bjork-Shiley areas were calculated directly from the valves' inner ring radius. Gorlin valve areas correlated poorly with actual valve areas (r = 0.39). The mean Gorlin formula error was 0.36 cm2 (standard deviation = 0.32). Gorlin areas overestimated actual areas by greater than 0.25 cm2 in 43 patients (32%) and underestimated actual areas by greater than 0.25 cm2 in 29 (21%). It was concluded that the Gorlin formula inaccurately predicts prosthetic valve area in the aortic position. Overreliance on this formula in assessing aortic stenosis could lead to errant clinical decisions.