DK2985_C000 1..28 - AlSharqia Echo Club

Evaluation of Aortic Valve Surgery 379recorded by CW Doppler in order to obtain the truegradient across the valve.. The presence of perivalvular edema or hematoma instentless prosthesis during the immediate postoperativeperiod may result in a lower than expected EOAduring the first few months after operation.For these reasons, the recording of relatively highgradients in the immediate postoperative period shouldnot be viewed with undue concern. A simple algorithmmay be used to assess abnormally high gradients in theimmediate postoperative period (Fig. 16.13); this algorithmis identical to the one used during operation. Giventhat patient–prosthesis mismatch is the most frequentcause of high gradients, the first step of this algorithm isto determine if mismatch is present by calculating theprojected indexed EOA. It should be noted that theDoppler-echocardiographic measurement of LVOT strokevolume (SV) and thus of valve EOA in the immediatepostoperative period is often not feasible and/or reliable.It is, therefore, preferable to use the projected indexedEOA to assess the presence and severity of mismatch.This parameter is simply calculated by dividing thenormal reference EOA for the model and size of prosthesisimplanted (see Table 16.3) by the patient’s BSA. If the projectedindexed EOA is 0.85 cm 2 /m 2 , the abnormally highgradient is likely due to mismatch. If the projected indexedEOA is .0.85 cm 2 /m 2 , several aforementioned conditionsand technical pitfalls must first be ruled out before concludingprosthesis dysfunction. Therefore, unless the transvalvulargradients are very high or are associated withsignificant symptoms or deterioration in left ventricularfunction, a conservative approach with observation andrepeat assessment 3–6 months later is advocated.Granted these considerations, a more comprehensivealgorithm may be used for evaluating abnormally high gradientsafter AoV replacement (Fig. 16.19). However, thisalgorithm should be used only when the hemodynamiccondition has settled down and there is, in particular, nohigh CO state or an abnormally high velocity in theLVOT. The diagnosis of patient–prosthesis mismatch isestablished by a nonindexed EOA of the prosthesisunder study comparable to its normal reference value(Table 16.3). On the other hand, if the nonindexed EOAis much lower than the reference value for the prosthesis,the diagnosis of intrinsic dysfunction should be raised.Causes of such dysfunction include the presence of thrombosis,pannus, or endocarditis. Occasionally, an abnormallyhigh velocity jet corresponding to a localizedgradient may be recorded by CW Doppler interrogationthrough the smaller central slit-like orifice of bileafletmechanical prosthesis. This is not reproduced when redirectingthe ultrasound beam through either lateral majororifices. This is a limitation of the echocardiographicevaluation of bileaflet prostheses inherent in their designwhich should be kept in mind when encountering a relativelyhigh gradient in an otherwise asymptomaticpatient with this type of mechanical prosthesis.In conclusion, perioperative echocardiography may beuseful to detect clinically unsuspected abnormalities thatmay alter or add operative procedures during AoVsurgery (Table 16.4). Patient–prosthesis mismatch is byLATE POST-OPERATIVE PERIODAbnormally high gradientMeasured EOAsimilar to reference EOAMeasured EOA 0.85 cm 2 /m 2 cRule-out:• Perivalvular edema instentless bioprostheses• Localized high gradients inbileaflet mechanical valvesMild/moderate PPM≤ 0.65 cm2/m2cSevere PPMRule-out:• Increased LVOTvelocity due tohyperdynamic state orsubvalvular narrowing• Technical pitfallsLook for:• Prosthesis dysfunctionFigure 16.19 Algorithm used for evaluating abnormally high transvalvular pressure gradients in the late postoperative period afteraortic valve replacement. This algorithm should be used only when the hemodynamic condition has stabilized and there is no highcardiac output state or abnormally high left ventricular outflow tract (LVOT) velocity (BSA, body surface area; EOA, effectiveorifice area; PPM, patient–prosthesis mismatch).