| Popis: |
Patients with combined aortic valve pathology (stenosis and insufficiency) are often evaluated as if they had only a single pathology, because a means of evaluating the detrimental effects of combined insufficiency and stenosis does not yet exist. The study aim was to test the performance of a new hemodynamic index based on mechanical energy loss to measure the effects of combined valve disease on ventricular workload.An intact and subsequently perforated and sutured aortic bioprosthesis was tested in an in vitro model of the left heart, varying cardiac output, average diastolic aortic pressure, and the type and combination of valve lesion. The regurgitant fraction (RF), systolic transvalvular pressure gradient (Deltaps), and energy loss indices of forward flow (LPVf), regurgitant flow (LPVr), and the sum of the two (LPVc), were measured for each experimental condition and compared with the increase in work per unit volume net forward flow (DeltaWPV) due to perforation and suturing.Deltaps was found to underestimate LPVf when the valve was perforated. LPVc had an excellent linear relationship with DeltaWPV (slope = 0.98, r2 = 0.97) that was independent of valve lesion or flow and pressure conditions.Deltaps does not describe the increase in ventricular workload, or even the forward flow portion of it, when valve insufficiency is present. LPVc was found to be a very good measure of the decrease in pump effectiveness due to aortic valve insufficiency or combined valve pathology. |
