QUASI-STEADY BEHAVIOR OF PULSATILE, CONFINED, COUNTERFLOWING JETS - IMPLICATIONS FOR THE ASSESSMENT OF MITRAL AND TRICUSPID REGURGITATION

Mitral and tricuspid regurgitation create turbulent jets within the at ria. Clinically, for the purpose of estimating regurgitant severity, j et size is assumed to be proportional to peak jet flow rate and regurg itant volume. Unfortunately, the relationship is more complex because the determinants of jet size include interactions between jet pulsatil ity, jet momentum, atrial width, adn the velocity of ambient atrial co unterflows. These effects on fluorescent jet penetration were measured using an in vitro simulation. Both steady and pulsatile jets were dri ven into an opposing counterflow velocity field peak jet length (L(jp) ) measurements made as a function of (1) peak orifice velocity (U-jp), (2) the time required for the jet to accelerate from zero to peak vel ocity and begin to decelerate (T-jp), (3) jet orifice diameter (D-j), (4) counterflow velocity (U-c), and (5) counterflow tube diameter (D-c ). A compact mathematical description was developed using dimensional analysis. Results showed that peak jet length was a function of the co unterflow tube diameter, the ratio of peak jet to counterflow momentum , (M(jp)/M(c)) = ((UJPDj2)-D-2)/((UcDc2)-D-2), and a previously undesc ribed jet pulsatility parameter, the pulsatility index (PI), PI = D-c( 2)/(TjpUjpDj). For the same jet orifice flow conditions, jet penetrati on decreased as chamber diameter decreased, as the jet PI increased, a nd as the momentum ratio decreased. These interactions provide insight into why regurgitant jet size is not always a good estimate of regurg itant severity.