DK2985_C000 1..28 - AlSharqia Echo Club

TEE in Mechanical Circulatory Assistance 321(A)(B)SV CO VACUUMINFLOW CANNULANormal velocity < 250 cm/secINFLOWSV CO PRESSUREOUTFLOW CANNULANormal velocity > 200 cm/secFigure 14.6 From the left ventricular apex, on continuouswaveDoppler, flow is seen directed away from the probe.Normal flow should be laminar with a peak velocity,250 cm/sec. (A) In this example, the peak velocity was atthe upper limit due to restricted inflow in the canula secondaryto left-sided ventricular septal shift from severe right ventriculardilatation. (B) Flow at the level of the ascending aorta is seendirected towards the transducer. The normal outflow velocityshould be .200 cm/sec. (CO, cardiac output; SV, strokevolume) (5).support. If the AoV is found regurgitant, it mustbe either replaced or oversewn. This permanentclosure of the AoV does not usually have hemodynamicconsequences as, during full LVADsupport, the AoV normally does not open at all(Fig. 14.7).2. The presence of intracardiac shunts such as atrialseptal defect (ASD) or patent foramen ovale(PFO) must be methodically ruled out using twodimensional(2D), color Doppler as well as ultrasoundcontrast imaging (2). Because these patientsoften have a left atrial pressure exceeding rightatrial pressure during the entire cardiac cycle, aPFO, present in up to 20–30% of the general population(10) may not be readily obvious, even withintravenous injection of agitated saline ultrasoundcontrast. To elicit the presence of a potentialright-to-left shunt, a manoeuver equivalent to aValsalva must be performed by inducing asudden release of a sustained positive airway pressurepreviously achieved by inflating the lungsmanually. This maneuver will transiently reversethe atrial transseptal gradient and may helpuncover a PFO that would not have been seenotherwise. When a PFO or an ASD is discovered,it must be repaired. Indeed, failure to recognizethe presence of a right-to-left shunt, even small atbaseline, can result in important arterial desaturationduring LVAD support (11) from increasedshunting due to the combination of frequentlyincreased right atrial pressure and left atrial decompressionby LVAD.3. Baseline right ventricular function must also becarefully assessed (Fig. 14.11): poor right ventricularfunction warrants insertion of a RVAD. Thelevel of preoperative right ventricular functionalso helps to predict the eventual level of pharmacologicsupport required to support the right ventricularat the end of LVAD implantation.4. The degree of tricuspid regurgitation (TR) shouldalso be quantified (see Chapter 19).5. The apices of both ventricles (and atrium) shouldbe carefully inspected to rule out the presence ofthrombus: ventricular cannulation with thrombicould induce catastrophic embolic events. Cautiousremoval of thrombus may be attempted by thesurgeon to minimize embolic complications.6. The ascending, transverse, and descending thoracicAo should also be scrutinized for the presence ofmobile atherosclerotic debris. Incomplete TEEvisualization should be supplemented by epiaorticscanning (EAS). A safe site for aortic cannulation(outflow) could thus be determined.During Cardiopulmonary BypassSurgical positioning of the “inflow” cannulae in theatrium or the ventricle can be directly assisted by TEE.