TURBULENT VISCOUS INTERACTIONS CONTROL DOPPLER/CATHETER PRESSURE DISCREPANCIES IN AORTIC-STENOSIS - THE ROLE OF THE REYNOLDS-NUMBER/

Background Despite good correlation between Doppler and catheter press ure drops in numerous reports, it is well known that Doppler tends to apparently overestimate pressure drops obtained by cardiac catheteriza tion. Neither (1) simplification of the Bernoulli equation nor (2) pre ssure recovery effects can explain this dilemma when taken alone. This study addressed the hypothesis that a Reynolds number-based approach, which characterizes (1) and (2), provides a first step toward better agreement of catheter and Doppler assessments of pressure drops. Metho ds and Results Doppler and catheter pressure drops. were studied in an in vitro model designed to isolate the proposed Reynolds number effec t and in a sheep model with varying degrees of stenosis. Doppler press ure drops in vitro correlated with the directly measured pressure drop for individual Valves (r=.935, .960, .985, .984, .989, and .975) but with markedly different slopes and intercepts. A Bland-Altman type plo t showed no useful pattern of discrepancy. The Reynolds number was suc cessful in collapsing the data into the profile proposed in the hypoth esis. Parallel results were found in the animal model. Conclusions App arent overestimation of net pressure drop by Doppler is due to pressur e recovery effects, and these effects are countered by both viscous ef fects and inertial/turbulent effects. Only by reconciliation of discre pancies by use of a quantity such as Reynolds number that embodies the relative importance of competing factors can the noninvasive and inva sive methods be connected. This study shows that a Reynolds number-bas ed approach accomplishes this goal both in the idealized in vitro sett ing and in a biological system.