DIFFERENT PRESSURE-GRADIENTS CAN BE PRODUCED IN A FIXED STENOSIS - ANIN-VITRO STUDY

An in vitro study was conducted, using a stenotic model to demonstrate that different pressure gradients can be produced by the same degree of valvular stenosis. This model is comprised of two cylindric chamber s with a diaphragm in the center which had a small central hole. An in jector was connected to one end of the prestenotic chamber to produce a steady pulsed flow. A rubber tube was connected to the other end of the poststenotic chamber and led upward to a large reservoir which pro vided a constant afterload pressure. Two pressure transducers were att ached to the two connecting tubes, both linked with two pigtail cathet ers which were accommodated in the chambers just before and after the stenotic diaphragm. Two sets of injection volumes (20 and 30 ml) and m ultiple injections with different flow rates (5, 10, 15,...49 ml/s) we re administered and resulting pressures measured by the two transducer s were recorded. Results showed that different pressure gradients coul d be produced using the same injection volume, the same afterload, and the same degree of stenosis. The greater the flow rate, the higher th e pressure gradient. Good correlation existed between the pressure gra dient and the injection flow rate (r = 0.95 and 0.97 for the study gro ups receiving 20 and 30 ml injection volumes, respectively; p< 0.001 i n all comparisons). Thus, a higher pressure gradient may not necessari ly indicate a severe degree of valvular stenosis. Evaluation of a sten otic lesion should not be made from the degree of pressure gradient al one-other hemodynamic conditions should also be taken into account.